can't perform an effective grid calibration

[ericmateovisan]

I checked the lens specification.. this is a 1/2 type lens ( Max image format 6.4x4.8mm) and the camera have a 1/2.5"  sensor format.. it means me lens is a little bit bigger than image sensor.. I've read somewhere that this issue ( lens bigger than sensor ) cause the phenomenon called "Magnification" .. could this issue  have something to do with  the focus thing ?

[SamiF]

Forget about magnification, this is a characteristic of your setup not an issue.

A 1/2" lens means this lens provides an image circle big enough to cover a 1/2" sensor. Above this size, you may have dark borders on your image (vignetting). Anyway, this is not the problem in your case.

Your problem is probably that the lens resolution is too poor on the border. The sensor you are using has very small pixels (2.2 µm I think). You should check with your supplier if your lens can handle that. Computar has many ranges of lenses, from standard quality to high end ones.

Sami

[ericmateovisan]

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@SamiF wrote:

Forget about magnification, this is a characteristic of your setup not an issue.

A 1/2" lens means this lens provides an image circle big enough to cover a 1/2" sensor. Above this size, you may have dark borders on your image (vignetting). Anyway, this is not the problem in your case.

Your problem is probably that the lens resolution is too poor on the border. The sensor you are using has very small pixels (2.2 µm I think). You should check with your supplier if your lens can handle that. Computar has many ranges of lenses, from standard quality to high end ones.

Sami

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Thank you Sami, I got it 🌼🌹 

yes the pixel sizes on sensor are 2.2x2.2 micro meters. I will contact Computar to know if this lens can handle that pixel size or not

best regards

Eric

[BruceAmmons]

Wide angle lenses commonly have issues with distortion and focus at the edges of the images.  It takes a pretty expensive lens to fix that.  Usually the solution is to move the camera further away from the target and use a different lens.

Honestly, your image didn't look too bad to me.  There might be slight focus issues, but the calibration grid looks pretty clear.

Bruce

[ericmateovisan]

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@BruceAmmons wrote:

Wide angle lenses commonly have issues with distortion and focus at the edges of the images.  It takes a pretty expensive lens to fix that.  Usually the solution is to move the camera further away from the target and use a different lens.

Honestly, your image didn't look too bad to me.  There might be slight focus issues, but the calibration grid looks pretty clear.

Bruce

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Thank you Bruce for your reply, actually when I zoom in to identify the pixels to check the calibration results I have low focus and low contrast between the dots edges and the white part of the paper.. as you and Sami mentioned the unevenness of light and reflect of light inside the device box, itself bother the quality of the image in the corners.. furthermore I realized that the quality of the printed calibration grid is quite low in the edges of the dots which could be another reason of my problem.. 

this is a microscopic image of one of the dots