Cooled DSLR History 2

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Dry ice cooled DSLR………………….05. 08. 29

I designed dry ice cooling unit & CMOS airtight chanber front of the lens mount.

At the left pictres square hole is the entrance for the dry ice to go in and get out.

I could buy 80 pieces of 28mm×28mm×28mm dry ice for USD $6.5 at dry ice store.

It can be keeped in styropor box for about 2 days and at open space 1 piece go 1/5 of it’s height after 30minutes. by blocking the air it keeped it up twice as long. By putting on insulating cloth it hoped to keep up even more.

Using 15cm FPC cable and connector to connect CMOS to mainboard it is more neatly connected than before.

Luckily I could get 32 pin, 1.0mm pitch, 15cm FPC cable so I was able to do jobs with preexistence CMOS and FPBC.

The boundary sides that cable passes(CMOS chamber > Dryice chamber > camera body)was sealed with silicon calking.

For cable wiring, I fixed camera bosy’s mirror upward, and removed shutter screen and the cable passed through that opened space.

CMOS sensor’s temperature is seemed to go up since dry ice will sublime. But I didn’t checked on yet. Since there were little amount of dew at low-temperature area in covered up CMOS chamber, after putting in dry nitrogen gas I thinked hard on it and I decided to  make CO2, which comes out when dry ice sublimes, go through inner unit of the CMOS and gets out of the camera. It was effective. CO2 gas is said that it is inactive and insulate well on below the normal temperature, but i’m not confident about what it’ll do on ships and inner wirings.

And because of the humidity problems inside the CMOS chamber, there were dew condensation at protection glass removed CMOS sensor’s surface, but there were no problems at working just as if nothing has happened.

Maybe separate surfaces like RGB filter in chip’s surface or micro lens, etc is making insulate layer at semiconductor devices.

there are many unfinished jobs about dew condensation.

 

To the right is CMOS sensor, there is 0.5mm protection glass to seal and protect light receiving surface, but it isn’t arnt-reflection coated so I removed it.

Luckily it was easily removed with thin blade of knife, I was in a hurry that I broke a piece and the part of it is still inside the sensor housing.

I was pressured that I have to be in a great carefulness when doing sensor jobs, and I had to consider the movemnet of the focus as much as the thickness of the broken glass.

To think of ti now, there was more loss than get( To others please don’t follow this)

 

 

Upper is the picture using dry ice in a frozen condition ASA1600, 30mins darkframe.

At B shutter there was no mechanical shutter but there was no problems in picture. Probably there is electric shutter concept working on here. There are vivid blazing noises at four corners and I still don’t know why. I’m thinking that since CMOS chamber is so little that at the four corners of the sensor, there is lot of heat-exchange from the housing. And this make the temperature go up more than the center of it.

Except these blazing noises there are nearly no noises.(refer enlargement images of A,B)

I filled dry nitrogen in CMOS chamber and sealed it perfectly, but there still was dew condensation.

To think about it normally the air pressure of it is the same as outer air, but if the frigidus starts by the dry ice the inner of the chamber’s air will shrunk and the air pressure will go down. And this will make outer air to come inside. First I’ll test it by filling it with the nitrogen and putting in drying agent as a  assistance.


The first object of field test was the Orion. As expected the frost was made at the surface of the sensor and it is vividly seen. But nomatter the frost the sensor worked normally.
Cannon 135mm L lens,
8mins exposure ( F3.6)

sensitivity 1600, Cooled 300D

 

* dew condensation needs to be fixed immediately.

 

 

 

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