digital camera optical device?

N_Cook

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Apr 9, 2015, 5:40:00 AM4/9/15

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Decided to break into an old camera and remove the IR filter to explore
what effect that has for using as an IR camera to some extent.
Especially as there is a service manual for it , casio QV700 and
dismantling procedure and schematics etc.
There was a glass or crystaline square block that was blue in colour,
removed it, immediately over the CCD chip, now seem to have lost focus.
May have moved something else in the process, this block looking through
it has no refractive effect, seems to just colour things blue, what is
it? Maybe a sandwich of blue glass and 2 slabs of white glass, not equal
thicknesses

N_Cook

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Apr 9, 2015, 9:20:12 AM4/9/15

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replacing that little block and normal focus function ruturned

Michael Black

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Apr 9, 2015, 9:48:04 AM4/9/15

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On Thu, 9 Apr 2015, N_Cook wrote:

> replacing that little block and normal focus function ruturned
>

Did you check to see if the camera saw IR in the first place?

I have a few, and at least one digital camera sees IR.

Michael

John Robertson

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Apr 9, 2015, 10:41:10 AM4/9/15

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An easy check if a camera sees IR is to simply point an IR remote at the
camera and press buttons while looking through the camera at the dark
plastic end. If you see bluish/white light appear only on the camera
screen then you are seeing the IR light.

If you don't see IR then the lens likely has a coating on it to absorb
that spectrum.

John :-#)#

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Michael Black

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Apr 9, 2015, 12:33:14 PM4/9/15

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On Thu, 9 Apr 2015, John Robertson wrote:

> On 04/09/2015 6:48 AM, Michael Black wrote:
>> On Thu, 9 Apr 2015, N_Cook wrote:
>>
>>> replacing that little block and normal focus function ruturned
>>>
>> Did you check to see if the camera saw IR in the first place?
>>
>> I have a few, and at least one digital camera sees IR.
>>
>> Michael
>>
>>
>
> An easy check if a camera sees IR is to simply point an IR remote at the
> camera and press buttons while looking through the camera at the dark plastic
> end. If you see bluish/white light appear only on the camera screen then you
> are seeing the IR light.
>

Which is what I did. I can't even remember which camera it was, but it
wsan't my most recent one.

> If you don't see IR then the lens likely has a coating on it to absorb that
> spectrum.
>

Which then explains the original poster's issue, it's not a separate
filter but a coating.

Michael

Phil Hobbs

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Apr 9, 2015, 12:43:24 PM4/9/15

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It's the IR blocking filter, and usually also a pair of crossed walkoff
plates that spreads the light out evenly over the 2x2 pixel subarray (2
green, 1 red, 1 blue) that corresponds to each display pixel. That
prevents coloured jaggies in the image.

The colour filters used in CMOS and CCD processes are organic dyes,
which have a huge hole in the NIR. You need a separate IR filter, or
the colour balance will be all off and you'll start seeing through some
types of clothing. (There was a bit of a flap some years ago when Sony
introduced a camcorder that did that.)

Cheers

Phil Hobbs

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Optics, Electro-optics, Photonics, Analog Electronics

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