Camera for PC Monitor Image Acquisition

[B.Settles]

I am looking for a NI supported camera that can be used to capture PC monitor images. The largest monitor I am trying to analyze is ~22 in. with a resolution of 1600 x 1200 with a refresh rate of 60 Hz. I tried to use the camera advisor, but did not see any that would meet these settings.

[BruceAmmons]

If you are trying to analyze the individual pixels of the monitor, it will require several pixels of camera resolution for each pixel of monitor resolution.  You would probably be better off using several cameras, like a 2x2 array where each camera looks at 1/4 of the screen.  Even then, the cameras will be expensive.  The size of the monitor doesn't really matter, since you just pick a lens that will give you the field of view you need.

Bruce

[AnalogKid2DigitalMan]

An issue that might crop up is camera frame acquisition time versus monitor frame rate. I do not know how to fully explain it, other than it is an aliasing artifact. Have you ever seen the PC monitors in the background of newcasts or a video of someone's monitor? Note how there is sometime a horizontal bar that progresses downward in the monitor. Your eyes alone never see it, but it crops up only when you are watching a monitor acquired by another camera. Clear as mud?

[BruceAmmons]

Actually, that is easily taken care of.  You just have to match your exposure time to the frequency of the screen.  For example, if your screen refreshes at 65 Hz, your shutter speed has to be 1/65 second or an integer multiple of that.

Bruce

[AnalogKid2DigitalMan]

Bruce:

Would synchronzation matter regardless if rates are the same or multiples?

If you start camera acqusition when the monitor is currently 'writing' say 1/2 way down the screen and data written to monitor is changing, would the upper half of the acquired frame not match the lower? Ideally sync the camera to the start of frame of the monitor.

Any interlaced versus non-interlaced issues?

I am just curious about this, no application in mind, but it may be of use to the OP.

Thanks

[BruceAmmons]

If it is a static image, synchronization won't matter.  If the image was changing, you would want to synchronize the frame start.

For an interlaced image, you have to do multiples of 2 scans so you capture both odd and even lines.

Bruce