How can I get a clear image of a moving object,using my interlaced camera?

[31238]

The shutter speed is 1/25,1/250,1/500,1/1000 and etc., it seems the interalced camera can capture a moving object with a low speed,such as 0.02m/s,because the shutter speed can climb up to 1/4000 (as the instruction said).
But why in fact I can't get a clear image?

[BruceAmmons]

Your problem is the frame rate. I will assume you are using a 30 fps camera. It is actually taking 60 fields per second, which are the odd and even lines of your image. Half of the image is taken 1/60 of a second after the first half. No matter what you set the exposure at, the delay between the odd and even lines will be 1/60 of a second. You will notice that at fast shutter speeds, all of your lines are very clear, but the object is in a different position for each field.

One option for moving objects is to use field mode, which only uses a single field (odd or even lines), which gives you an image which is 1/2 the height of a normal image.

Another option is using a progressive scan camera, which takes all lines of the image at the same time.

A f
ew interlaced cameras will let you overlap the exposure times, giving you 1/30 second exposure time on all lines. In this case, you could use a strobe so that all of the lines would be exposed simultaneously. This could be tricky, and not many cameras let you do that.

Bruce

[31238]

Thanks for the fast response. However I try to use field mode, the result is the same. Maybe the illumination light is weak so the shutter speed can not be automatically turned to high values? Do u thin so?

On the other hand, what do u mean at your last paragraph? "overlap the exposure times..." Can explain it more detailed?

[BruceAmmons]

You mentioned that your longest shutter time is 1/25 of a second. This means the exposure periods for the odd and even fields overlap. With a fast, bright strobe you could expose both fields simultaneously. The rest of the exposure period would be essentially dark. The trick would be timing the strobe so that the odd and even fields were both part of the same image. Otherwise, you would have to locate the exposed odd and even fields and put them together to make the image.

I would think it would be much simpler to just use a progressive scan camera. Using very bright lights and short exposure times will also help you.

Bruce