drascic@ecf.UUCP (08/14/87)
I have an application where two CCD video cameras have to be genlocked. There seem to be two routes available: 1) for those cameras accepting a composite genlock signal, we can use a distribution amplifier to split the video output of one camera into two parts. The first part is used as normal, the second is used as the genlock input to the second camera. Question: does anyone know of a (cheap) amplifier that would be appropriate? Could we build our own with a suitable op amp (must run at 12V, though)? 2) for cameras expecting HD/VD, we need a sync generator. The only ones I have been able to find cost $3K - $4K, which exceeds our budget enormously. We do not need something that is broadcast quality (it would be wasted on the equipment we have!). I'm amazed at the difficulty/cost we have faced. After all, every cheapo video camera and graphics board has a sync generator built in. Question: do cheap video sync generators exist? Can we build one ourselves? Thanks. David Drascic drascic@ecf.toronto.edu University of Toronto utecfb!drascic Dept. of Industrial Engineering
dsi@unccvax.UUCP (DataSpan R+D) (08/17/87)
In article <225@mv03.ecf.toronto.edu>, drascic@ecf.toronto.edu (SpIKe) writes: > I have an application where two CCD video cameras have to be genlocked. > > There seem to be two routes available: > 1) for those cameras accepting a composite genlock signal, we > can use a distribution amplifier to split the video output > of one camera into two parts. The first part is used as normal, > the second is used as the genlock input to the second camera. > > Question: does anyone know of a (cheap) amplifier that would be appropriate? For synchronization pulse distribution, you could even stoop as low as using a TL 081 or (preferably) an MC 33074 opamp. This is not going to preserve the edges (150 nS rise) obviously, but it will work pretty darned well. Better still, if the camera will genlock to composite video, use a plain old emitter follower stage. The best, cheap approach, is to use a decent comparator (LM 311 comes to mind) and clip off the sync pulses and distribute that. > 2) for cameras expecting HD/VD, we need a sync generator. The only > ones I have been able to find cost $3K - $4K, which exceeds our > budget enormously. We do not need something that is broadcast > quality (it would be wasted on the equipment we have!). I'm > amazed at the difficulty/cost we have faced. After all, every > cheapo video camera and graphics board has a sync generator built > in. Most cameras I have seen expecting HD/VD will accept composite sync for HD, and integrated vertical sync for VD. Use a two stage integrator and a comparator to generate the vertical drive signal, and just clip the sync pulses for the horizontal. This works very effectively. You could use a one-shot and some combinational logic if you really **must** have true horizontal drive. The best way to do this is to have a master sync generator. Ferranti has a sync generator chip, the ZNA 134 H; as does Fairchild (the number escapes me). They are both broadcast quality when used with the appropriately stable timebase. You can build this for well under $25. If you need colour sync generation (black burst, etc.) this will be considerably more difficult but not impossible to build; the Fairchild chip would then be your choice. The Fairchild chip runs at 4 Fsc in colour mode, for which either an oscillator can be made using an ordinary colour burst crystal, or you can always get 14.3182818 mHz crystals through commodity parts junk dealers like DigiKey. ] Most cheapo graphics cards use less than full NTSC sync generation. This would include the TMS 34061, which we currently are using in a commercial product. I have seen Cohu cameras genlock to even this chip, even though it does not provide the equalizing pulses (the TI chip, that is). If you were desparate, you could probably build what you need out of a few sequential PAL's or SSI. David Anthony DataSpan, Inc
johnlee@pnet01.CTS.COM (John Wiley) (08/17/87)
I'm interested in doing something similar. I understand that you need a
variable phase, in order to match the 2 cameras. Beyond that, it seems like
it should be easy. I'd appreciate email or a summary on why it isn't. Also,
how about building a camera from the process board and CCD? Couldn't you then
just use the sync generated by the first camera?
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INET: johnlee@pnet01.CTS.COMgeorgep@vice.TEK.COM (George Pell) (08/18/87)
In article <225@mv03.ecf.toronto.edu>, drascic@ecf.toronto.edu (SpIKe) writes: > I have an application where two CCD video cameras have to be genlocked. > .............. > Question: do cheap video sync generators exist? Can we build one ourselves? You might use a MM5321 TV camera sync generator from National Semiconductor. It is a P-channel MOS LSI device which uses either a 1.26 Mhz or a 2.04545 Mhz clock which can be derived from dividing down a 14.31818 Mhz clock by 7. The device outputs color burst gate, horizontal drive, color burst sync, composite sync, composite blanking, vertical drive, and a field index pulse which can be used to gen lock another 5321. I have breadboarded this device, and it is easy to use and costs about $20.00 . geo
olson@endor.harvard.edu (Eric Olson) (08/19/87)
In article <1826@vice.TEK.COM> georgep@vice.TEK.COM (George Pell) writes: >You might use a MM5321 TV camera sync generator from National >Semiconductor. It is a P-channel MOS LSI device which uses This chip is being discontinued by National (according to our local hardware guru, who would really like to find one that ISN'T being discontinued). -Eric Eric K. Olson olson@endor.harvard.edu harvard!endor!olson