fig2 shows the modified device . the light source in this device is preferably a light source with low thermal inertia that can be modulated at rates higher that 10 khz , and preferably higher than 1 mhz . a preferred light source is an ultrabright , light emitting diode (“ led ”), which produces 0 . 05 watts of output . this led can be turned on and off at rates up to about 2 mhz . a pulse generator 210 is provided which produces a pulse output that modulates the led . the system described herein also is used to detect movements , e . g . vibrations , of micromachined structure 199 . the micromachined structure 199 is driven to vibrate . the driving is preferably done by a signal generator that drives the pulse generator that drives the led . a phase offset , shown as φ , exists between the two outputs 202 which drives the led and 204 which drives the micromachined structure 199 . this phase offset can be used to change the point in the vibration cycle of the micromachined device 199 at which the visual image is acquired . the visual image is acquired by driving the led to produce strobes of light . each pulse of the led strobe illuminates both the object to be imaged and the reference surface . the interference between the two illuminations enables determination of position . since the pulse of the strobe is short , the device , even if moving , will not have moved much during the strobe . this avoids blurring of the interferometric measurement . in a particularly preferred embodiment , the mems device which is imaged is a cloverleaf - type rotary vibration sensor . the inventors also found that many mems devices , including the one that is preferably imaged herein , vibrates differently under atmospheric pressure or might not vibrate at all under such pressure . this can be caused by excessive viscous drag on the micromachined structure . accordingly , the operation of the present system includes a vacuum chamber 230 provided to house the sample . the vacuum chamber includes a vacuum port 232 connected to a vacuum source 234 . the vacuum source evacuates the air from the chamber 230 . the mems device 199 to be detected is located in the chamber 230 . the vacuum chamber 230 also includes a wire port 236 allowing wires to be connected so that the signal generator 210 can vibrate and / or actuate the mems device 199 . the sample beam 120 in this embodiment therefore encounters an additional glass plate : the viewport 238 . in order to compensate for the effects of the viewport , a compensating plate 240 is placed into the reference arm 242 of the michelson interferometer . the compensating plate is of the same thickness as the glass viewport 238 . this compensates for the extra glass in the path caused by the vacuum chamber . in order to accurately detect the movement of the mems device 199 , it is necessary to modulate the light source at a synchronized modulation rate , that is synchronized to the movement of the mems device 199 . movement of the device during the illumination pulse could cause blurring of the fringe of the interference pattern . therefore , the duty cycle of the source should be shortened as the vibration amplitude increases . the device should not move more than a distance of about { fraction ( 1 / 20 )} th of the center wavelength of the source , during the illumination pulse . hence , for a structure vibrating at 10 khz with a 10 μm amplitude , this translates into a maximum pulse width of about 200 nsec , or about a 0 . 2 % maximum duty cycle . the overall integrated light intensity of a frame using illumination with such a short duty cycle may be very small . the pulse rate of the light source should be at least a factor of 10 lower than the lowest modulation rate of the light source . as explained above , the light source must be modulable at least at 10 khz . if the amount of incoming light is too small , or to improve the noise , the system can integrate over a larger number of periods . presumably , the image obtained during each period is substantially the same . hence , by integrating a number of these images , the light output can be increased . a processor calculates the relationship between the interference fringes , and uses that to determine the position of the device . this is done in a conventional way . the phase between motion and light pulse can be varied to image the device at different points in its periodic motion . the processor then calculates all of these different positions . superluminescent leds , a cluster of conventional leds , or a laser could be used to further improve the brightness . although only a few embodiments have been disclosed in detail above , those of ordinary skill in the art should certainly understand that modifications are possible in the preferred embodiment without departing from the teachings hereof . all predictable modifications are intended to be included . for example , while the present system describes only modifying a single optical profiler , it should be understood that other optical profilers can also be modified . for example , any optical profiler which uses an imaging interferometer could be modified in this way . more generally , however , any measurement detecting structure which detects using optical operations could be detected in this way . the operation describes using a single pulse generator , but of course two separate pulse generators could be used , with one triggered from the other . moreover , the system herein describes using a superluminescent led as the light source . however , any light source which can be modulated at a high enough rate can be used . all such modifications are intended to be encompassed within the following claims in which :