embodiments of the invention are described below with reference to the drawings . fig1 is a block diagram showing one embodiment of a video signal processing apparatus and method according to the invention . numeral 1 is a contour correction means , 2 is an edge ( contour portion ) detection means , 3 is an edge ( contour correction signal ) generation means , 4 is a mixing means , 5 is a selection means , 6 is an input terminal , 7 is an output terminal , and 8 is a contour correction means . in fig1 , a digital video signal s 1 input from the input terminal 6 is supplied to the contour correction means 1 , 8 . the contour correction means 1 has the same configuration as the conventional digital video signal processing apparatus shown in fig2 , and outputs a digital video signal s 2 in which a contour was corrected in the same manner as the digital video signal c shown in fig3 by performing the same operation . this digital video signal s 2 is supplied to the selection means 5 and the mixing means 4 . on the other hand , the contour correction means 8 consists of the edge detection means 2 , the edge generation means 3 , and the mixing means 4 . the digital video signal s 1 from the input terminal 6 is supplied to the edge detection means 2 and the edge generation means 3 . when the edge detection means 2 detects an edge ( contour portion ) of the input digital video signal s 1 by the method described later , the edge generation means 3 generates an edge signal s e using the digital video signal s 2 and an edge coefficient k supplied from an interpolation control means that is not illustrated , based on the detection result . this edge signal s e is supplied to the mixing means 4 , and mixed with the digital video signal s 2 output from the contour correction means 1 . furthermore , this edge signal s e is mixed with the digital video signal s 2 in this manner . accordingly , as described later , this signal is a contour correction signal for suppressing an undershoot in the contour portion generated by the correction processing of the contour correction means 1 , and is represented as an edge signal below . the edge generation means 3 and the mixing means 4 form an edge correction means , in this manner , that suppresses the undershoot generated in the digital video signal s 2 that was interpolated from the contour correction means 1 . a digital video signal s 3 with which the edge signal s e output from this mixing means 4 was mixed is supplied to the selection means 5 . this selection means 5 is controlled using a selection control signal s s for this edge period generated when the edge detection means 2 detected the edge of the digital video signal s 1 , and selects , in an edge period , the output digital video signal s 3 of the mixing means 4 , and , in a period other than the edge period , the output digital video signal s 2 of the contour correction means 1 . consequently , the output digital video signal s 2 of the contour correction means 1 is interpolated using the output digital video signal s 3 of the mixing means 4 and obtained in the output terminal 7 in the edge period . subsequently , the operation of the edge detection means 2 is described with reference to fig4 to 7 . fig4 is a flowchart showing one specific example of the edge detection operation of the edge detection means 2 . this edge is judged regarding multiple sample periods ( hereinafter referred to as a judgment sample period ) using three thresholds delta 1 , delta 2 , and level , and their relations are delta 1 & lt ; delta 2 and delta 1 & lt ; level . this judgment sample period is set in such a degree that an edge of a striped pattern repeated in the minimum cycle on a picture can be judged . incidentally , the threshold delta 1 is used for judging a flat portion ( hereinafter referred to as a flat portion merely ) of the picture . the threshold delta 2 is used for judging the crest of a peak of the picture or the root of a valley of the picture ( hereinafter referred to as the crest of a peak or the root of a valley merely ). the threshold level is used for judging an edge . the edge detection operation of the edge detection means 2 is described below citing one specific example of an image pattern . ( 1 ) as a first edge criterion of the edge judgment of the edge detection means 2 , two flat portions that differ in a signal level are detected in the aforementioned judgment sample period . when no flat portion can be found between these flat portions , an edge is assumed to exist between these flat portions . fig5 shows one specific example of the judgment sample period in which an edge can be judged based on this first edge criterion , and fig5 ( b ) is the digital video signal s 1 of the sample cycle t input to the edge detection means 2 . fig5 ( a ) conveniently shows one example of the continuous waveform of this digital video signal s 1 . this digital video signal s 1 samples the video signal shown in this fig5 ( a ) in the sample cycle t . in fig5 ( b ), incidentally , a judgment sample period is specified as four times of the sample cycle t , that is , 4t , and the samples to be judged are specified as samples a to e . furthermore , the signal levels of each of the samples a , b , c , d , e are specified as a , b , c , d , e , and another edge judgment described later is also specified in the same manner . for such judgment sample periods a to e , the edge detection means 2 , first , obtains the absolute value | a − b | of the difference of the signal levels of the first two samples a , b . when this value is lower than the threshold delta 1 (“ yes ” in step 100 of fig4 ), a flat portion is assumed to exist between the samples a and b . subsequently , the absolute value | b − c | of the difference of the signal levels of the samples b , c is obtained . when this value is lower than the threshold delta 1 (“ yes ” in step 101 of fig4 ), the flat portion of the period of 2 t is obtained , and , accordingly , an edge is assumed to be undetected ( step 301 of fig4 ). the processing of this judgment sample period terminates and the same judgment processing starts in the next judgment sample period starting from the sample b shifting by the sample cycle t . in fig5 ( b ), however , because the absolute value | b − c | exceeds the threshold delta 1 (“ no ” in step 101 of fig4 ) , a flat portion is assumed to exist up to the sample b and , furthermore , the absolute value | c − d | of the difference of the signal levels of the samples c , d is obtained . when this value is lower than the threshold delta 1 (“ yes ” in step 102 of fig4 ), the flat portion is assumed to exist even between the samples c and d . accordingly , there are two flat portions sandwiching between the samples b and c . when the absolute value | b − c | of the signal levels of these b , c is higher than the threshold level (“ yes ” in step 109 of fig4 ), an edge is assumed to exist between the samples b and c ( step 201 of fig4 ). the judgment processing of these judgment sample periods a to e terminates and moves to the judgment processing of the next judgment sample period starting from the sample b . when the absolute value | c − d | is higher than the threshold delta 1 (“ no ” in step 102 of fig4 ) and lower than the threshold delta 2 (“ no ” in step 103 of fig4 ), or / and the absolute value | c − d | is higher than the thresholds delta 1 , 2 (“ no ” in step . 102 of fig4 and “ yes ” in step 103 ) but when the signal level c is not higher or lower than the signal levels b , d (“ no ” in step 106 of fig4 ), the absolute value | d − e | of the difference of the signal levels of the samples d , e is obtained subsequently . when this value is lower than the threshold delta 1 (“ yes ” in step 104 of fig4 ), a flat portion is assumed to exist between these d and e . accordingly , the flat portion is assumed to exist between the samples a and b and between the samples c and d . subsequently , whether an edge is assumed to exist between the samples b and d is judged based on this judgment result . that is , when the signal level continues increasing or decreasing in the order of the samples b , c , d (“ yes ” in step 107 of fig4 : in fig5 ( b ) the signal level is increasing sequentially ), and the absolute value | b − d | is higher than the threshold level (“ yes ” in step 110 of fig4 ) , an edge is assumed to exist between the samples b and d ( step 202 of fig4 ). as described above , for the digital video signal s 1 shown in fig5 ( b ) in which two flat portions exist , ( when the absolute value | c − d | is lower than the threshold delta 1 ) between these flat portions , that is , between the samples b and c or ( the absolute value | c − d | is higher than the threshold delta 1 between the samples b and d , and the signal levels b , c , d sequentially increase or decrease ), an edge can be detected . furthermore , the judgment processing of the judgment sample periods a to e terminates , and , in the judgment processing of the judgment sample periods ( sample b → sample a , sample c → sample b , . . . ) starting from the next sample b , the processing of steps 100 , 111 , 112 , 303 of fig4 or steps 100 , 111 , 112 , 113 , 117 , 303 of fig4 is performed . consequently , an edge is not detected between the samples b and c or samples b and d in fig5 ( b ). that is , the same edge will not be detected twice or more . moreover , although the aforementioned case applied to an edge in which a signal level increases , the edge is judged using the absolute value of the difference of the signal levels between two samples . accordingly , even for an edge in which the signal level decreases , the edge is judged in the same manner . accordingly , in fig5 , if there is a trailing edge subsequently , the flat portion immediately before the edge and the flat portion behind this edge are detected . consequently , this trailing edge is detected in the same way as described above . ( 2 ) as a second edge criterion of the edge judgement of the edge detection means 2 , a flat portion of a signal level and a changing point , such as the crest of a peak or the root of a valley of a signal level fluctuation , are detected in the aforementioned judgment sample period and an edge is assumed to exist between the flat portion and this changing point ( their sequence relations are ignored ). the changing point is described specifically below as the crest of the peak or root of the valley from the relation with a drawing . fig6 shows one specific example of the judgment sample period in which an edge can be judged based on this second edge criterion , and , in this specific example , a flat portion and the crest of a peak are detected . fig6 ( b ) is the digital video signal s 1 of the sample cycle t input to the edge detection means 2 . fig6 ( a ) conveniently shows an example of the continuous waveform of this digital video signal s 1 , and , as illustrated , shows the start portion of a picture that represents a striped pattern in which light and shade are repeated every period of less than 2t . the digital video signal s 1 samples the video signal shown in this fig6 ( a ) in the same cycle t . even in this specific example , the judgment sample period is specified as 4t , and the samples to be judged are specified as the samples a to e . in fig6 ( b ), the judgment between the samples a and b , the judgment between the samples b and c , and the judgment between the samples c and d are the same as the specific example shown in fig5 . among the samples a to d , a flat portion is judged between the samples a and b by the judgment processing of steps 100 to 103 ( 106 ) of fig4 . subsequently , the absolute value | d − e | of the difference of the signal levels of the samples d and e is obtained and whether this value is lower than a threshold or not is judged . incidentally , when this absolute value | d − e | is higher than the threshold delta 1 (“ no ” in step 104 of fig4 ) and is higher than the threshold delta 2 (“ yes ” in step 105 of fig4 ), a flat portion is not assumed to exist between the samples d and e . accordingly , in the aforementioned first criterion , an edge cannot be judged between the samples b and d not sandwiched by two flat portions and the judgment enters a held state . incidentally , in this specific example , the second criterion is applied . that is , the sample d has a higher signal level than the samples b , c , e and forms the crest of a peak or has a lower signal level and forms the root of a valley (“ yes ” in step 108 of fig4 ) and , when the absolute value | b − d | of the difference of the signal levels of the samples b , d is higher than the threshold level (“ yes ” in step 110 of fig4 ), an edge is judged between the samples b and d ( step 202 of fig4 ). in other cases ( that is , the judgment “ no ” of steps 105 , 108 , 110 ), the edge is not assumed to exist between the samples b and d ( step 303 ). furthermore , in fig6 ( b ), when the sample c among the samples b , c , d is the crest of a peak or the root of a valley ( steps 103 , 106 , 109 ), an edge is assumed to exist between the samples b and c ( step 201 of fig4 ) . when the digital video signal s 1 samples a digital signal consisting of a series of rectangular waves of high frequency using a fine striped pattern of a picture , the edge at the head of the first rectangular wave that cannot be detected in the aforementioned first criterion according to this second criterion . furthermore , even in the specific example shown in this fig6 ( b ), in the next sample period ( in this case , sample b → sample a , sample c → sample b , . . . ) starting from the sample b , the processing of 119 , 304 or 116 , ( 120 ), 305 is performed from steps 100 , 111 , 112 , 113 , 114 , 118 , 115 of fig4 . an edge is not judged between the samples b and d once the edge was judged in the processing of the previous judgment sample periods a to e . accordingly , the same edge is not detected twice or more . ( 3 ) as a third edge criterion of the edge judgment of the edge detection means 2 , when the crest of a peak and the root of a valley are detected in the aforementioned judgment sample periods , an edge is assumed to exist between these crest of the peak and root of the valley . fig7 shows one specific example of the judgment sample periods in which an edge can be judged based on this third edge criterion . in this specific example , the crest of a peak and the root of a valley are detected . fig7 ( b ) is the digital video signal s 1 of the sample cycle t input to the edge detection means 2 . fig7 ( a ) conveniently shows the intermediate portion of an example of the continuous waveform of this digital video signal s 1 , and , as illustrated , shows a picture that represents a striped pattern in which light and shade are repeated every period of 2t or less . the digital video signal s 1 samples the video signal shown in this 7 ( a ) in the sample cycle t . even in this specific example , the judgment sample period is specified for 4t and the samples to be judged are specified as the samples a to e . in fig7 ( b ), for these judgment sample periods a to e , the edge detection means 2 , first , obtains the absolute value | a − b | of the difference of the signal levels of the first two samples a , b . this is judged to be higher than the threshold delta 1 (“ no ” in step 100 of fig4 ) and higher than the threshold delta 2 (“ yes ” in step 111 of fig4 ). subsequently , the absolute value | b − c | of the difference of the signal levels of the samples b , c is obtained and this value is judged to be higher than the threshold delta 1 (“ no ” in step 112 of fig4 ). furthermore , when the absolute value | b − c | is lower than the threshold delta 1 (“ yes ” in step 112 of fig4 ), a flat portion is assumed to exist between the samples b and c . accordingly , an edge is assumed to be undetected ( step 303 of fig4 ) and processing moves to the processing between the next judgment sample periods . subsequently , the absolute value | c − d | of the difference of the signal levels of the samples c , d is obtained . when this is higher than the threshold 1 (“ no ” in step 113 of fig4 ) and is lower than the threshold delta 2 (“ no ” in step 114 of fig4 ) or is higher than the threshold delta 2 (“ yes ” in step 114 of fig4 ), the signal levels of the samples a , b , c , d are a & gt ; b & lt ; c & lt ; d (“ no ” in step 118 of fig4 ). accordingly , the absolute value | d − e | of the difference of the signal levels of the samples d , e is obtained and whether this value is higher than the threshold delta 1 or not is judged ( step 115 of fig4 ). in this case , the absolute value | d − e | is higher than the threshold delta 1 (“ no ” in step 115 of fig4 ) and is higher than the threshold 2 (“ yes ” in step 116 of fig4 ). furthermore , because the signal levels of the samples a to e are a & gt ; b & lt ; c & lt ; d & gt ; e (“ yes ” in step 120 of fig4 ), the sample b is judged as the root of a valley and the sample d is judged as the crest of a peak . subsequently , the absolute value | b − d | of the difference of the signal levels of the samples b , d is obtained between the root of this valley and the crest of this peak . when this value is higher than the threshold level (“ yes ” in step 11 of fig4 ), an edge is judged between these samples b and d ( step 204 ). further , in fig7 ( b ), when the sample c is the crest of a peak instead of the sample d , processing advances from step 114 of fig4 to step 118 and “ yes ” is judged . the sample b is judged as the root of a valley and the sample c is judged as the crest of the peak . furthermore , when the absolute value | b − c | of the difference of the signal levels between the samples b and c is higher than the threshold level (“ yes ” in step 11 d of fig4 ) , an edge is judged between the sample b of the root of the valley and the sample c of the crest of the peak ( step 203 ). moreover , in fig7 ( b ), when a flat portion is assumed to exist between the samples c and d (“ yes ” in step 113 of fig4 ) , the signal levels of the samples a , b , c are a & gt ; b & lt ; c (“ yes ” in step 117 of fig4 ). accordingly , the sample b is judged as the root of a valley . according to the aforementioned second criterion , when the absolute value | b − c | of the difference of the signal levels with this sample b and the sample d at the head of the flat portion is higher than the threshold level (“ yes ” in step 11 d of fig4 ), an edge is judged between the samples b and c ( step 204 of fig4 ). further , in fig7 ( b ), when a flat portion is assumed to exist between the samples d and e (“ yes ” in step 115 of fig4 ) , the signal levels of the samples b , c , d are b & lt ; c & lt ; d (“ yes ” in step 119 of fig4 ). accordingly , the sample b is judged as the root of a valley . according to the aforementioned second criterion , when the absolute value | b − c | of the difference of the signal levels with this sample b and the sample c at the head of the flat portion is higher than the threshold level (“ yes ” in step 11 d of fig4 ), an edge is judged between the samples b and d ( step 203 of fig4 ). furthermore , in the specific example shown in fig7 , a leading edge was detected between the samples b and c or between the samples b and d , but processing is performed using the absolute value of the difference of signal levels . accordingly , a trailing edge is detected in the same manner . except the aforementioned case , an edge is not judged between the samples b and c or between the samples b and d ( steps 304 , 305 of fig4 ). returning to fig1 , the edge detection means 2 detects an edge of an input digital video signal s 1 in this manner . the edge generation means 3 generates the edge signal s e using the edge period of the digital video signal s 1 detected by the edge detection means 2 and the edge coefficient k supplied from an interpolation control means that is not illustrated . fig8 shows an edge period detected by the edge detection means 2 . each of b to f marked with a circle is the sample of the digital video signal s 1 in this edge period and each of b ′ to f ′ marked with a square and a black square is the sample of the edge signal s e in this edge period . the edge generation means 3 sequentially generates the samples b ′, c ′, d ′, e ′, f ′ corresponding to an edge period detected by the edge detection means 2 , for example , the samples b , c , d , e , f of the digital video signal s 1 . supposing that the first sample b ′ of the edge period is the first sample and the j - th ( where , j = 1 , 2 , 3 , 4 , 5 ) sample signal level is v j , it follows that in fig8 , the edge generation means 3 obtains a signal level assuming β j = 1 / 2 in the above expression ( 1 ). among the samples within the edge period of the digital video signal s 1 , a sample ( in fig8 , sample d ) of this signal level v k of the edge signal s e is generated at the timing of the sample ( in fig8 , sample d ) of the signal level most approximate to this signal level v k . the signal levels ( in this case , signal levels v 1 , v 2 of the samples b ′, c ′) of all samples that precede this sample d ′ are specified as signal level b when β j = 0 in the aforementioned expression ( 1 ) and the signal levels ( in fig8 , signal levels v 4 , v 5 of samples e ′, f ′) of all samples following this sample ( in fig8 , sample d ′) are specified as signal level f when β j = 1 in the aforementioned expression ( 1 ). accordingly , the efficient β j of the signal level v j from the sample b ′ in the aforementioned expression ( 1 ) in this case appears as this coefficient β j is supplied from an interpolation control means that is not illustrated as an edge coefficient k . furthermore , this edge coefficient β j is not limited to only this , but it can be set optionally as occasions demand , such as the edge signal s e generated by the edge generation means 3 in this manner is supplied to the mixing means 4 . this edge signal s e and the digital video signal s 3 from the contour correction means 1 are mixed at a desired ratio and the digital video signal s 3 is generated . fig9 shows the situation . when the input digital video signal s 1 shown in fig9 ( a ) is corrected for a contour by the contour correction means 1 , as shown in fig9 ( b ), an undershoot 10 occurs in the start portion of the period that corresponds to an edge period detected by the edge detection means 2 and an overshoot 11 occurs immediately after the period that corresponds to this edge period . fig9 ( c ) shows the aforementioned edge signal s e in the edge period generated by the edge generation means 3 and detected by the edge detection means 2 . this signal and the digital video signal s 2 shown in fig9 ( b ) are mixed by the mixing means 4 at a predetermined ratio . subsequently , the digital video signal s 2 shown in fig9 ( b ) is substituted for the digital video signal s 3 from the mixing means 4 by the selection means 5 in the edge period detected by the edge detection means 2 . fig9 ( d ) shows a digital video signal output from the selection means 5 . this digital video signal consists of the digital video signal s 3 from the mixing means 4 when the period corresponds to the edge period detected by the edge detection means 2 . because this digital video signal s 3 is mixed with the edge signal s e , the undershoot 10 generated in the start portion of this edge period by the correction processing of the contour correction means 1 is reduced or suppressed . the undershoot 10 generated by the correction processing of the contour correction means 1 can be reduced or suppressed in this manner and the generation of a black edge that occurs in the contour portion of a picture can be suppressed . as the luminance level difference of an edge that forms the contour portion increases , the black edge appears more remarkably . by the aforementioned processing of this embodiment , however , the generation of this type of black edge can be suppressed and a picture having good image quality can be obtained . moreover , in the edge period of the digital video signal s 3 , because the edge signal s e is mixed with the output digital video signal s 2 of the contour correction means 1 , an edge having a steeper slope is generated in comparison with this digital video signal s 2 . accordingly , in a picture using a digital video signal output from the selection means 5 , the black edge in the contour portion does not become highlighted . at the same time , in the picture , the contour portion becomes more vivid and the sharpness is improved . furthermore , the overshoot 11 is generated in an edge by the correction processing of the contour correction means 1 . because this overshoot appears immediately after an edge period , however , it is not affected by the mixing of the edge signal s e but remains as is . accordingly , the contour portion of a picture is represented remarkably and a high - quality picture of high sharpness is obtained suppressing the generation of a black edge . moreover , in fig9 , a leading edge ( contour portion ) is described as an example . in a trailing edge ( contour portion ), however , an overshoot caused by contour correction is added behind the contour portion . accordingly , the overshoot is shifted later from an edge period in which the edge detection unit 3 ( fig1 ) detects from the input digital video signal s 1 . incidentally , the edge detection means 2 shifts edge detection timing , and , accordingly , the edge signal s e the edge generation means 3 generates and the operation of the selection are delayed for the shift of this edge detection timing . for example , when the contour correction means 1 corrects a contour by the method described in fig2 and 3 , an undershoot added to a falling contour portion is delayed by only 2t twice of the sample cycle t in comparison with the contour portion of the input digital video signal s 1 . incidentally , when the edge detection portion detects an edge ( contour portion ), whether the contour portion is a rising contour portion or not is judged by comparing the signal level between the start sample and the end sample . when the contour portion is the falling contour portion , the generation start of the edge signal s e of the edge generation means 3 is delayed only by 2t and the operation of the selection means 5 is delayed in the same manner . furthermore , in the aforementioned embodiment , only the undershoot caused by the contour correction in a contour portion is suppressed , but an overshoot may also be suppressed . accordingly , an abnormal “ glare ” in the contour portion of a picture can also be removed . to perform such correction processing , a period ( that is , edge period ) at which the video signal s 3 of the selection means 5 in fig1 is prolonged . the period can be prolonged until the period in which an overshoot exists after the edge period of the contour portion terminates . for example , when fig9 is cited as an example , the period in which the selection means 5 selects the video signal s 3 is prolonged until the period in which the overshoot occurs in comparison with the illustrated edge period . needless to say , the edge signal s e is also created at least until this extended period . moreover , consequently , even when the contour portion consists of a trailing edge , the same edge signal s e as this can be used . even if an undershoot is suppressed in this manner , and even if an overshoot is suppressed , an edge becomes steeper in comparison with the result of the correction processing of the contour correction means 1 by the mixing processing of the mixing means 4 and a contour correction effect is improved . fig1 is a block diagram showing one embodiment of a camera device and its imaging method according to the invention using the video signal processing apparatus described above . numeral 11 is a ccd ( charge coupled device ) image sensor , 12 is a cds ( correlated double sampling ) circuit , 13 is an agc ( automatic gain control ) circuit , 14 is an a / d ( analog / digital ) converter , 15 is a y ( luminance )/ c ( chroma ) separation circuit , 16 is a luminance signal processing circuit , 17 is a gamma correction circuit , 18 is a contour correction circuit , 19 is a synchronous addition circuit , 20 is a d / a ( digital / analog ) converter , 21 is a chrominance signal processing circuit , and 22 , 23 are d / a converters . in fig1 , the ccd image sensor 11 photographs a picture that is not illustrated and outputs an electric signal in accordance with this picture . in this electric signal , a waveform is formed through the cds circuit 12 and a pixel signal is sampled . in the electric signal , after a gain is controlled so that amplitude may be made constant through the agc circuit 13 , a digital video signal is generated by supplying the electric signal to the a / d converter 14 . this digital signal is separated into a digital luminance signal y and a digital chrominance signal c through the y / c separation circuit 15 . the digital luminance signal y is supplied to the luminance signal processing circuit 16 and the digital chrominance signal c is supplied to the chrominance signal processing circuit 21 respectively . in the luminance signal processing circuit 16 , after the input digital luminance signal y is gamma - corrected through the gamma correction circuit 17 , a contour portion is corrected through the contour correction circuit 18 and a synchronous signal is added through the synchronous addition circuit 19 . the digital luminance signal y for which the aforementioned processing was performed is output from the luminance signal processing circuit 16 and converted to an analog luminance signal by the d / a converter 20 . for example , the luminance signal y having a predetermined system such as an ntsc ( national television system committee ) system is obtained . on the other hand , after processing , such as separation into a primary colors signal , white balance , or gamma correction , is performed to the digital chrominance signal c separated through the y / c separation circuit 15 , digital color difference signals r - y , b - y are generated , and modulated respectively . these digital color difference signals r - y , b - y are supplied to the d / a converters 22 , 23 respectively and converted to an analog signal . the color difference signals r - y , b - y having the predetermined system such as the ntsc system are obtained . this embodiment uses a video signal processing apparatus according to the invention described previously as the contour correction circuit 18 of the luminance signal processing circuit 16 in a camera device of this configuration . accordingly , the luminance signal y obtained from the d / a converter 20 is corrected for a counter , but it changes into a luminance signal because an undershoot is suppressed by this contour correction processing . in a picture based on a video signal obtained by this camera device , a black edge is not highlighted in the contour portion . furthermore , the embodiment shown in fig1 shows one example of the invention . even a camera device of any configuration having a contour correction circuit including this example can use the video signal processing apparatus shown as the aforementioned embodiment , as this contour correction circuit . accordingly , needless to say , the camera device according to the invention is constructed . as described above , according to the invention , the generation of a black edge in the contour portion of a picture caused by contour correction can be suppressed and the glare in the contour portion can be suppressed . a picture having high image quality can be obtained holding the sharpness of the image caused by contour correction satisfactorily . fig1 is a block diagram of one embodiment of an interpolation device and interpolation method according to the invention , and a camera device and its imaging method . numeral 1 is an imaging means , 2 is a signal processing means , 3 is a memory means , 4 is an interpolation control means that controls an interpolation using a timing pulse and an interpolation coefficient , 5 , 6 are interpolation means , 7 is an edge detection means , 8 is an edge generation means , 9 is a mixing means , 10 is a selection means , and 11 is an output terminal . in fig1 , an electric signal obtained by the photographing of the imaging means 101 is supplied to the signal processing means 201 and the digital video signal s 1 of the sample ( pixel ) cycle t is generated . this digital video signal s 1 is written to the memory means 301 at the timing of the sample cycle t every sample with the write timing pulse p w generated by the interpolation control means 401 , and a sample is sequentially read with the read timing pulse p r generated by the interpolation control means 401 in the four - time timing of the sample cycle t . moreover , the sample is read by 1 h every 4 h ( h is a horizontal scanning period ) in a vertical scanning direction . accordingly , the one fourth portion of the sample is sampled with the digital video signal s 1 input to the memory means 301 . consequently , the digital video signal s 2 of a picture ( hereinafter referred to as an enlarged picture ) enlarged into four times in horizontal / vertical scanning directions respectively is obtained . as shown in fig1 , the interpolation means 501 , 601 , the selection means 5 , and the interpolation control means 401 constructs an interpolation device . the digital video signal s 2 is supplied to the interpolation means 501 , 601 of this interpolation device . the interpolation means 601 consists of the edge detection means 2 , the edge generation means 3 , and the mixing means 4 . in the interpolation means 501 , a digital video signal of the sample cycle t is interpolated linearly ( also in a vertical scanning direction , the linear interpolation of a horizontal scanning line is performed , but the linear interpolation in the vertical scanning direction is not described ) using the interpolation coefficient k 1 generated by the interpolation control means 401 , and a digital video signal s 3 of the sample cycle t is obtained . this digital video signal s 3 is supplied to the selection means 5 and the mixing means 4 of the interpolation means 601 . on the other hand , in the interpolation means 601 , when the edge detection means 2 detects the edge of the digital video signal s 2 of an enlarged picture by the method described later , the edge generation means 3 generates an edge signal s e consisting of the sample of the cycle t using the digital video signal s 2 and the edge coefficient k 2 described later generated by the interpolation control means 401 based on the detection result . this edge signal s e is supplied to the mixing means 4 and mixed with the digital video signal s 3 output from the interpolation means 501 . the edge generation means 3 and the mixing means 4 forms an edge enhancement means in this manner that enhances the edge of the digital video signal s 3 interpolated from the interpolation means 501 . a digital video signal s 4 with which the edge signal s e output from this mixing means 4 is mixed is supplied to the selection means 5 as an output signal of the interpolation means 601 . this selection means 5 is controlled using a selection control signal s s in the period of this edge generated when the edge detection means 2 detected the edge of the digital video signal s 2 , and selects , in the edge period , the output digital video signal s 4 of the interpolation means 601 , and , in a period other than the edge period , the output digital video signal s 3 of the interpolation means 501 . accordingly , the output digital video signal s 3 of the interpolation means 501 is obtained in an output terminal 11 in the edge period by interpolating the output digital video signal s 4 of the interpolation means 601 . in the interpolation means 501 , the digital video signal s 2 is interpolated using the linear interpolation described in fig1 , but this linear interpolation is described with reference to fig1 ( b ), ( c ). incidentally , supposing a picture p 2 of the sample cycle t shown in fig1 ( b ) is a picture p 3 of the sample cycle t (= t / 4 ), three samples are interpolated between the adjacent samples of the picture p 2 . in linear interpolation , a straight line connects between the adjacent samples , and a signal level of an interpolation sample is set so that the signal level on this straight line may be obtained . incidentally , in fig1 ( b ), the signal levels of the adjacent two samples a , b are a , b respectively , a signal level q 1 of an interpolation sample q 1 ( where , i = 1 , 2 , 3 ) interpolated between these samples a and b is represented as for a flat portion , because a ≈ b , it follows that q 1 ≈ a . moreover , for an edge , because b = α × a ( where , α & gt ; 1 ), it follows that and the picture p 3 shown in fig1 ( c ) is generated . the interpolation means 501 generates the interpolation sample q 1 by supplying in the aforementioned expression ( 1 ) from the interpolation control means 401 as the interpolation coefficient k 1 and performing the operation of the aforementioned expression ( 1 ) every adjacent two samples in the picture p 2 shown in fig1 ( b ), and generates the picture p 3 shown in fig1 ( c ) interpolated using this sample . the signal of this picture p 3 is the digital video signal s 3 in fig1 . subsequently , the operation of the edge detection means 2 is described with reference to fig1 to 16 . fig1 is a flowchart showing one specific example of the edge detection operation of the edge detection means 2 . this edge is judged regarding multiple sample periods ( hereinafter referred to a judgment sample period ) using three thresholds delta 1 , delta 2 , and level , and their relations are delta 1 & lt ; delta 2 and delta 1 & lt ; level . this judgment sample period is set in such a degree that an edge of a striped pattern repeated in the minimum cycle on a picture can be judged . incidentally , the threshold delta 1 is used for judging a flat portion ( hereinafter referred to as a flat portion merely ) of the picture . the threshold delta 2 is used for judging the crest of a peak of the picture or the root of a valley of the picture ( hereinafter referred to as the crest of a peak or the root of a valley merely ). the threshold level is used for judging an edge . the edge detection operation of the edge detection means 2 is described below citing one specific example of an image pattern . ( 1 ) as a first edge criterion of the edge judgment of the edge detection means 2 , two flat portions that differ in a signal level are detected in the aforementioned judgment sample period . when no flat portion can be found between these flat portions , an edge is assumed to exist between these flat portions . fig1 shows one specific example of the judgment sample period in which an edge can be judged based on this first edge criterion , and fig1 ( b ) is the digital video signal s 2 of the sample cycle t input to the edge detection means 2 . fig1 ( a ) conveniently shows an example of the continuous waveform of this digital video signal s 2 . this digital video signal s 2 samples the video signal shown in this fig1 ( a ) in the sample cycle t . in fig1 ( b ), incidentally , the judgment sample period is specified as four times of the sample cycle t , that is , 4t , and the samples to be judged are specified as samples a to e . furthermore , the signal levels of each of the samples a , b , c , d , e are specified as a , b , c , d , e , and another edge judgment described later is also specified in the same manner . for these judgment sample periods a to e , the edge detection means 2 , first , obtains the absolute value | a − b | of the difference of the signal levels of the first two samples a , b . when this value is lower than the threshold delta 1 (“ yes ” in step 100 of fig1 ), a flat portion is assumed to exist between the samples a and b . subsequently , the absolute value | b − c | of the difference of the signal levels of the samples b , c is obtained . when this value is lower than the threshold delta 1 (“ yes ” in step 101 of fig1 ), the flat portion of the period of 2t is obtained , and , accordingly , an edge is assumed to be undetected ( step 301 of fig1 ). the processing of this judgment sample period terminates and the same judgment processing starts in the next judgment sample period starting from the sample b shifting by the sample cycle t . in fig1 ( b ), however , because the absolute value | b − c | exceeds the threshold delta 1 (“ no ” in step 101 of fig1 ) , a flat portion is assumed to exist up to the sample b and , furthermore , the absolute value | c − d | of the difference of the signal levels of the samples c , d is obtained . when this value is lower than the threshold delta 1 (“ yes ” in step 102 of fig1 ), the flat portion is assumed to exist even between the samples c and d . accordingly , there are two flat portions sandwiching between the samples b and c . when the absolute value | b − c | of the signal levels of these b , c is higher than the threshold level (“ yes ” in step 109 of fig1 ), an edge is assumed to exist between the samples b and c ( step 201 of fig1 ). the judgment processing of these judgment sample periods a to e terminates and moves to the judgment processing of the next judgment sample period starting from the sample b . when the absolute value | c − d | is higher than the threshold delta 1 (“ no ” in step 102 of fig1 ) and lower than the threshold delta 2 . (“ no ” in step 103 of fig1 ), or / and the absolute value | c − d | is higher than the thresholds delta 1 , 2 (“ no ” in step 102 of fig1 and “ yes ” in step 103 ) but when the signal level c is not higher or lower than the signal levels b , d (“ no ” in step 106 of fig1 ), the absolute value | d − e | of the difference of the signal levels of the samples d , e is obtained subsequently . when this value is lower than the threshold delta 1 (“ yes ” in step 104 of fig1 ), a flat portion is assumed to exist between these d and e . accordingly , the flat portion is assumed to exist between the samples a and b and between the samples c and d . subsequently , whether an edge is assumed to exist between the samples b and d is judged based on this judgment result . that is , when the signal level continues increasing or decreasing in the order of the samples b , c , d (“ yes ” in step 107 of fig1 : in fig1 ( b ) the signal level is increasing sequentially ), and the absolute value | b − d | is higher than the threshold level (“ yes ” in step 110 of fig1 ) , an edge is assumed to exist between the samples b and d ( step 202 of fig1 ). as described above , for the digital video signal s 2 shown in fig1 ( b ) in which two flat portions exist , ( when the absolute value | c − d | is lower than the threshold delta 1 ) between these flat portions , that is , between the samples b and c or ( the absolute value | c − d | is higher than the threshold delta 1 between the samples b and d , and the signal levels b , c , d sequentially increase or decrease ), an edge can be detected . furthermore , the judgment processing of the judgment sample periods a to e terminates , and , in the judgment processing of the judgment sample periods ( sample b → sample a , sample c → sample b , . . . ) starting from the next sample b , the processing of steps 100 , 111 , 112 , 303 of fig1 or steps 100 , 111 , 112 , 113 , 117 , 303 of fig1 is performed . consequently , an edge is not detected between the samples b and c or samples b and d in fig1 ( b ). that is , the same edge will not be detected twice or more . moreover , although the aforementioned case applied to an edge in which a signal level increases , the edge is judged using the absolute value of the difference of the signal levels between two samples . accordingly , even for an edge in which the signal level decreases , the edge is judged in the same manner . accordingly , in fig1 , if there is a trailing edge subsequently , the flat portion immediately before the edge and the flat portion behind this edge are detected . consequently , this trailing edge is detected in the same way as described above . ( 2 ) as a second edge criterion of the edge judgement of the edge detection means 2 , a flat portion of a signal level and a changing point , such as the crest of a peak or the root of a valley of a signal level fluctuation , are detected in the aforementioned judgment sample period and an edge is assumed to exist between the flat portion and this changing point ( their sequence relations are ignored ). the changing point is described specifically below as the crest of the peak or root of the valley ) from the relation with a drawing . fig1 shows one specific example of the judgment sample period in which an edge can be judged based on this second edge criterion , and , in this specific example , a flat portion and the crest of a peak are detected . fig1 ( b ) is the digital video signal s 2 of the sample cycle t input to the edge detection means 2 . fig1 ( a ) conveniently shows an example of the continuous waveform of this digital video signal s 2 , and , as illustrated , shows the start portion of a picture that represents a striped pattern in which light and shade are repeated every period of less than 2t . the digital video signal s 2 samples the video signal shown in this fig1 ( a ) at the same cycle t . even in this specific example , the judgment sample period is specified as 4t and the samples to be judged are specified as the samples a to e . in fig1 ( b ), the judgment between the samples a and b , the judgment between the samples b and c , and the judgment between the samples c and d are the same as the specific example shown in fig1 . among the samples a to d , a flat portion is judged between the samples a and b by the judgment processing of steps 100 to 103 ( 106 ) of fig1 . subsequently , the absolute value | d − e | of the difference of the signal levels of the samples d and e is obtained and whether this value is lower than a threshold or not is judged . incidentally , when this absolute value | d − e | is higher than the threshold delta 2 (“ no ” in step 104 of fig1 ) and is higher than the threshold delta 2 (“ yes ” in step 105 of fig1 ), a flat portion is not assumed to exist between the samples d and e . accordingly , in the aforementioned first criterion , an edge cannot be judged between the samples d and e not sandwiched by two flat portions and the judgment enters a held state . incidentally , in this specific example , the second criterion is applied . that is , the sample d has a higher signal level than the samples b , c , e and forms the crest of a peak or has a lower signal level and forms the root of a valley (“ yes ” in step 108 of fig1 ) and , when the absolute value | b − d | of the difference of the signal levels of the samples b , d is higher than the threshold level (“ yes ” in step 110 of fig1 ), an edge is judged between the samples b and d ( step 202 of fig1 ). in other cases ( that is , the judgment “ no ” of steps 105 , 108 , 110 ), the edge is not assumed to exist between the samples b and d ( step 303 ). furthermore , in fig1 ( b ), when the sample c among the samples b , c , d is the crest of a peak or the root of a valley ( steps 103 , 106 , 109 ), an edge is assumed to exist between the samples b and c ( step 201 of fig1 ) . when the digital video signal s 2 samples a digital signal consisting of a series of rectangular waves of high frequency using a fine striped pattern of a picture , the edge at the head of the first rectangular wave that cannot be detected in the aforementioned first criterion according to this second criterion . furthermore , even in the specific example shown in this fig1 ( b ), in the next sample period ( in this case , sample b → sample a , sample c → sample b , . . . ) starting from the sample b , the processing of 119 , 304 or 116 , ( 120 ), 305 is performed from steps 100 , 111 , 112 , 113 , 114 , 118 , 115 of fig1 . an edge is not judged between the samples b and d once the edge was judged in the processing of the previous judgment sample periods a to e . accordingly , the same edge is not detected twice or more . ( 3 ) as a third edge criterion of the edge judgment of the edge detection means 2 , when the crest of a peak and the root of a valley are detected in the aforementioned judgment sample periods , an edge is assumed to exist between these crest of the peak and root of the valley . fig1 shows one specific example of the judgment sample period in which an edge can be judged based on this third edge criterion . in this specific example , the crest of a peak and the root of a valley are detected . fig1 ( b ) is the digital video signal s 2 of the sample cycle t input to the edge detection means 2 . fig1 ( a ) conveniently shows the intermediate portion of an example of the continuous waveform of this digital video signal s 2 , and , as illustrated , shows a picture that represents a striped pattern in which light and shade are repeated every period of 2t or less . the digital video signal s 2 samples the video signal shown in this 16 ( a ) in the sample cycle t . even in this specific example , the judgment sample period is specified for 4t and the samples to be judged are specified as the samples a to e . in fig1 ( b ), for these judgment sample periods a to e , the edge detection means 2 , first , obtains the absolute value | a − b | of the difference of the signal levels of the first two samples a , b . this is judged to be higher than the threshold delta 1 (“ no ” in step 100 of fig1 ) and higher than the threshold delta 2 (“ yes ” in step 111 of fig1 ). subsequently , the absolute value | b − c | of the difference of the signal levels of the samples b , c is obtained and this value is judged to be higher than the threshold delta 1 (“ no ” in step 112 of fig1 ). furthermore , when the absolute value | b − c | is lower than the threshold delta 1 (“ yes ” in step 112 of fig1 ), a flat portion is assumed to exist between the samples b and c . accordingly , an edge is assumed to be undetected ( step 303 of fig1 ) and processing moves to the processing between the next judgment sample periods . in fig1 ( b ), for these judgment sample periods a to e , the edge detection means 7 , first , obtains the absolute value | a − b | of the difference of the signal levels of the first two samples a , b . this is judged to be higher than the threshold delta 1 (“ no ” in step 100 of fig1 ) and higher than the threshold delta 2 (“ yes ” in step 111 of fig1 ). subsequently , the absolute value | b − c | of the difference of the signal levels of the samples b , c is obtained and this value is judged to be higher than the threshold delta 1 (“ no ” in step 112 of fig1 ). furthermore , when the absolute value | b − c | is lower than the threshold delta 1 (“ yes ” in step 112 of fig1 ), a flat portion is assumed to exist between the samples b and c . accordingly , an edge is assumed to be undetected ( step 303 of fig1 ) and processing moves to the processing between the next judgment sample periods . subsequently , the absolute value | c − d | of the difference of the signal levels of the samples c , d is obtained . when this in higher than the threshold 1 (“ no ” in step 113 of fig1 ) and is lower than the threshold delta 2 (“ no ” in step 114 of fig1 ) or is higher than the threshold delta 2 (“ yes ” in step 114 of fig1 ), the signal levels of the samples a , b , c , d are a & gt ; b & lt ; c & lt ; d (“ no ” in step 118 of fig1 ). accordingly , the absolute value | d − e | of the difference of the signal levels of the samples d , e is obtained and whether this value is higher than the threshold delta 1 or not is judged ( step 115 of fig1 ). in this case , the absolute value | d − e | is higher than the threshold delta 1 (“ no ” in step 115 of fig1 ) and is higher than the threshold 2 (“ yes ” in step 116 of fig1 ). furthermore , because the signal levels of the samples a to e are a & gt ; b & lt ; c & lt ; d & gt ; e (“ yes ” in step 120 of fig1 ), the sample b is judged as the root of a valley and the sample d is judged as the crest of a peak . subsequently , the absolute value | b − d | of the difference of the signal levels of the samples b , d is obtained between the root of this valley and the crest of this peak . when this value is higher than the threshold level (“ yes ” in step 11 of fig1 ), an edge is judged between these samples b and d ( step 204 ). further , in fig1 ( b ), when the sample c is the crest of a peak instead of the sample d , processing advances from step 114 of fig1 to step 118 and “ yes ” is judged . the sample b is judged as the root of a valley and the sample c is judged as the crest of the peak . furthermore , when the absolute value | b − c | of the difference of the signal levels between the samples b and c is higher than the threshold level (“ yes ” in step 121 of fig1 ) , an edge is judged between the sample b of the root of the valley and the sample c of the crest of the peak ( step 203 ). moreover , in fig1 ( b ), when a flat portion is assumed to exist between the samples c and d (“ yes ” in step 113 of fig1 ) , the signal levels of the samples a , b , c are a & gt ; b & lt ; c (“ yes ” in step 117 of fig1 ). accordingly , the sample b is judged as the root of a valley . according to the aforementioned second criterion , when the absolute value | b − c | of the difference of the signal levels with this sample b and the sample c at the head of the flat portion is higher than the threshold level (“ yes ” in step 121 of fig1 ), an edge is judged between the samples b and c ( step 203 of fig1 ). further , in fig1 ( b ), when a flat portion is assumed to exist between the samples d and e (“ yes ” in step 115 of fig1 ) , the signal levels of the samples b , c , d are b & lt ; c & lt ; d (“ yes ” in step 119 of fig1 ). accordingly , the sample b is judged as the root of a valley . according to the aforementioned second criterion , when the absolute value | b − c | of the difference of the signal levels with this sample b and the sample c at the head of the flat portion is higher than the threshold level (“ yes ” in step 122 of fig1 ), an edge is judged between the samples b and d ( step 203 of fig1 ). furthermore , in the specific example shown in fig1 , a leading edge was detected between the samples b and c or between the samples b and d , but processing is performed using the absolute value of the difference of signal levels . accordingly , a trailing edge is detected in the same manner . except the aforementioned case , an edge is not judged between the samples b and c or between the samples b and d ( steps 304 , 305 of fig1 ). returning to fig1 , the edge detection means 2 detects an edge of an input digital video signal s 2 from the memory 3 in this manner . the edge generation means 3 of the interpolation means 601 generates the edge signal s e using the edge period of the digital video signal s 2 detected by the edge detection means 2 and the edge coefficient k 2 supplied from the interpolation control means 401 . this is described with reference to fig1 . fig1 ( a ) shows the digital video signal s 2 in fig1 in which the edge portion of a continuous waveform was sampled in the sample cycle t . b , c , d are the samples of this digital video signal s 2 . moreover , fig1 ( b ) shows the edge portion of the digital video signal s 3 interpolated linearly by the interpolation means 501 and the edge signal s e generated by the edge generation means 3 against this . incidentally , black circles are the samples b , c , d , a circle is an interpolation sample interpolated linearly between the samples b and c and between the samples c and d , and a square is the sample of the edge signal s e that forms an edge period generated by the edge generation means 3 . the edge generation means 3 sequentially generates seven edge interpolation samples ( shown with a square in fig1 ) in the sample cycle t (= t / 4 ) in the edge period detected by the edge detection means 2 , for example , between the samples b and d of the digital video signal s 2 . supposing the j - th ( where , j = 1 , 2 , . . . , 7 ) signal level is v j . it follows that assuming β j = 1 / 2 in the above expression ( 2 ). among the interpolation samples in the edge period of the digital video signal s 3 from the interpolation means 501 , an interpolation sample of this signal level v k is generated at the timing of the interpolation sample of the signal level most approximate to this signal level v k . the signal levels v 1 , v 4 , . . . , v k − 1 of all edge interpolation samples that precede this edge interpolation sample are specified as signal level b when β j = 0 in the aforementioned expression ( 2 ) and the signal levels v k + 1 , v k + 2 , . . . , v 7 of all edge interpolation samples following this edge interpolation sample are specified as signal level d when β j = 1 in the aforementioned expression ( 2 ). accordingly , supposing the edge interpolation sample of this signal level v k is most approximate to the signal level of the sample c of the digital video signal s 2 , the efficient β j of the signal level v j in the aforementioned expression ( 2 ) of the edge interpolation sample in the edge period appears as this coefficient β j is supplied from the interpolation control means 401 as an edge coefficient k 2 . furthermore , this edge coefficient k 2 is not limited to only this , but it can be set optionally as occasions demand , such as the edge signal s e generated by the edge generation means 3 in this manner is supplied to the mixing means 4 . this edge signal s e and the digital video signal s 3 from the contour correction means 5 are mixed at a desired ratio and the digital video signal s 4 is generated . incidentally , the edge signal s e generated in this manner can reproduce an edge component exceeding one half of the sampling frequency 1 / t of the digital video signal s 2 according to a sampling theorem , but the reproduction is a forecast to the end . accordingly , the image quality deterioration generated by an aliasing phenomenon when the forecast was not right can be reduced by mixing the output digital video signal s 3 of the interpolation means 501 interpolated according to the sampling theorem and the edge signal s e output from the edge generation means 3 . the selection means 5 selects the digital video signal s 4 in the edge period ( for example , the period between the samples b and d in fig1 to 16 ) of the digital video signal s 3 controlled using the control signal s s from the edge detection means 2 and detected by the edge detection means 2 , and selects the digital video signal s 3 from the interpolation means 501 in other periods . as described above , in this embodiment , when a digital picture is enlarged , because the enlarged picture is interpolated using an edge signal represented in the frequency component exceeding one half of sampling frequency in only the portion in which there is the frequency component exceeding the half of the sampling frequency of the enlarged picture , a picture having high sharpness can be obtained . moreover , because the edge detection means 2 and the edge generation means 3 are constructed without a multiplication means , a circuit scale can be reduced small . furthermore , the aforementioned embodiment was described assuming it to apply to a camera device , but the invention is not limited to only this . needless to say , the invention can be applied to another system , such as a sample is sampled and sent as a picture in which the number of samples was reduced on the sending side and the invention applies to the sample and the picture is interpolated on the receiving side . as described above , according to the invention , because an edge signal represented at frequency exceeding one half of the sampling frequency of a picture is generated from the digital video signal of the picture that becomes the object of a sample and the picture is interpolated using this edge signal , an edge is reproduced satisfactorily and a picture having high sharpness can be obtained . moreover , because an edge detection means and an edge generation means are constructed without needing a multiplication circuit , the increase of a circuit scale can be prevented and a picture having high sharpness can be obtained . while we have shown and described several embodiments in accordance with our invention , it should be understood that disclosed embodiments are susceptible of changes and modifications without departing from the scope of the invention . therefore , we do not intend to be bound by the details shown and described herein but intend to cover all such changes and modifications that fall within the ambit of the appended claims .