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Revision as of 00:50, 11 April 2012 by Legacy (Talk | contribs) (how does laser beam work)

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pcb laser exposer

project idea

The idea is to use a laser to define the traces on a standard photoresist-covered PCB-laminate.

On way would be to use a UV-laser (with suitable wavelength) to expose a positive photoresist, and then develop and etch the board the usual way. An option to a laser might be to use a high powered UV-diode with focusing optics to make a small enough dot of light to be useful.

laser dunnos (what i guess without an answer)

  • using green LED's with a conic black coated tip, opened at the tip to 0.1 - 0.2mm width as 'light-pen' in a plotter for exposing positive photo-films ?
  • or using modern UV-LED's
  • or BluRay-diodelasers with 50-200mW for positive/negative films
  • or 445nm(blue)-diodelaser with 1Watt max. power for exposing and/or cutting/engraving
  • or 808nm/975nm-IR-diodelasers with powers of some Watts to some ten Watts of power for cutting/engraving

What would a laser (or diode/optics arrangement) ? with sufficient power cost?

  • UV-LED with driver - some cents
  • (salvaged) BluRay-diode with optics driver - some ten $/€
  • 445nm-diodelaser with optics and driver - maybe 50 - 100 $
  • IR-diodelaser with optics and driver - maybe 200 - 1500 $ (power-dependant)
  • what about 405nm ???

(READ WITH CARE) how dangerous is Ultraviolet light (UV) wavelength ?

Ultraviolet light (UV) is non-ionizing radiation in the 180 to 400-nanometer wavelength region of the electromagnetic spectrum. The ultraviolet spectrum is commonly divided into the following three regions:

  • UVA Black Light 315nm .. 400nm
  • UVB Erythemal 280nm .. 314nm
  • UVC Germicidal 180nm .. 280nm

Exposure to ultraviolet radiation is typically limited to the UVA region resulting from exposure to direct sunlight. The Earth’s atmosphere shields us from the more harmful UVC and greater than 99% of UVB radiation. However, some equipment can generate concentrated UV radiation in all the spectral regions that, if used without the appropriate shielding and personal protective equipment, can cause injury with only a few seconds of exposure.


An unfortunate property of UV radiation is that there are no immediate warning symptoms to indicate overexposure. Symptoms of overexposure including varying degrees of erythema (sunburn) or photokeratitis (welder’s flash) typically appear hours after exposure has occurred.

  • Skin Injury - UV radiation can initiate a photochemical reaction called erythema within exposed skin. This “sunburn” can be quite severe and can occur as a result of only a few seconds exposure. Effects are exaggerated for skin photosensitized by agents such as coal tar products, certain foods (e.g., celery root), certain medications and photoallergens. Chronic skin exposure to UV radiation has been linked to premature skin aging, wrinkles and skin cancer.
  • Eye Injury – UV radiation exposure can injure the cornea, the outer protective coating of the eye. Photokeratitis is a painful inflammation of the eye caused by UV radiation-induced lesions on the cornea. Symptoms include a sensation of sand in the eye that may last up to two days. Chronic exposures to acute high-energy UV radiation can lead to the formation of cataracts.


  • first rule: never allow the skin or eyes to be exposed to UV radiation sources. The UV radiation generated by laser equipment can exceed

recommended exposure limits and cause injury with exposures as brief as three seconds in duration.

  • second rule to avoid Eye Injury: use protection glass, these are essential when operating a Class IV or Class IIIb laser in an environment where reflections can occur. They absorbs wavelengths from 370nm to 560nm, with an OD of +5 to +6 depending on the wavelength, unfortunately these will not provide protection against red or infrared lasers. They are intended for use with green, blue, and violet lasers.


405nm laser should be the safer choice

polygon mirror

Its assembly is mounted vertically on the flatbed scanners sled. The flatbed scanner sled is the Vertical axis, and the polygon mirror defelcting the laser in the scanner is the horizonbtal axis. Each Horizontal line is scanned about 150 times before the sled moves on to the next vertical position. The laser is scanned by the mirror continuasly at 55 Revolutions of the mirror per second, or 333 Hz scanrate, as the mirror is hexagon shaped. The exposure pattern is produced by turning the laser on and of synced to the rotation of the mirror.

Optics & Optical Issues

The original laser in a laserprinter is infrared, and that wavelength doesn't work for exposing pcbs which need 405nm at least.

You'd removed the infrared laser, and make a nice alluminium laser mount milling down the mirror assembly to fit it. As the lenses in the polygon mirror assembly had the wrong optical properties for my application, csudr different wavelength and different focussing distance, you'd removed them all.

The optical system should consists only of the laser, its focussing lens, and the polygon mirror.

There is one problem with this: as the beam length varies with the angle of the deflected laser beam, the focus of the laser lens would also have to be adjusted for each beam length. As this isn't done, the laser gets blurry at the ends and the middle of the scanline. But this is not a problem in practice, as the image gets sharp enough.

how does laser beam work


operating with pulse laser circuit

beam idea from Panasonic KX P4410


where to buy (proof list)

laser @ 405nm ??

  • Lilly-Electronics on ebay
  • o-like

Canon LBP1210


mirror motor

     3-phase Brushless driver
      VCC |1    \__/   36| nc    
      RS  |2           35| Limit
      FLT |3           34| Vref
      B1  |4           33| Vctl
      PS  |5         * 32| /Acc   <-----
phase.U   |6         * 31| /Dec   <-----
pahse.V   |7           30| RCP
      Gnd |8           29| Gnd 
      Gnd |9           28| Gnd
      Gnd |10          27| Gnd 
      Gnd |11          26| Gnd
phase.W   |12          25| SGnd
      HU+ |13          24| OSCV
      HU- |14          23| OSCC
      HV+ |15          22| FG- <----- it may be interesting
      HV- |16          21| FG+ <----- it may be interesting
      HW+ |17          20| Amp.out 
      HW- |18          19| FGout 

                 output current 
ACC   DEC        VCTL(CPout)       Function
H(5V) H(5V)         0uA            Hold
H(5V) L(0V)      -200uA            Deceleration
L(0V) H(5V)      +200uA            Acceleration
L(0V) L(0V)         0uA            Hold

Cable  Pin    Symbol       Function
         1    Vcc          Power supply 
         2    RS           Current sense 
         3    FLT          Connect to application of filter 
         4    B1           Short brake switch 
         5    PS           Power save signal input 
         6    U            Motor phase U output 
         7    V            Motor phase V output 
       8..11  Gnd          Power Gnd 
        12    W            Motor phase W output 
        13    Hu+          Hall sensor signal input (U phase +)
        14    Hu-          Hall sensor signal input (U phase -)
        15    Hv+          Hall sensor signal input (V phase +)
        16    Hv-          Hall sensor signal input (V phase -)
        17    Hw+          Hall sensor signal input (W phase +)
        18    Hw-          Hall sensor signal input (W phase
        19    FGout        FG comparator output
        20    Amp.out      FG amp. output
        21    FG+          FG signal input (+)
        22    FG-          FG signal input (-)
        23    OSCC OFF     Timer setup -1
        24    OSCV OFF     Timer setup -2
        25    SGnd         Gnd
      26..29  Gnd          Power Gnd
        30    RCP          Charge pump output current setup term.
        31    DEC          Deceleration signal input
        32    ACC          Acceleration signal input
        33    VCTL         Motor speed control voltage input
        34    VREF         Reference voltage input
        35    LIMIT        Current limit set up terminal
        36    N.C.         N.C

cable     M63154AFP
|1 |-  4,5, 8,9,10,11   (gnd)
|2 |-  31               (/dec, deceleration input)
|3 |-  32               (/acc, acceleration input)
|4 |-  1,2              (Vcc)