(Solved) Indigo Alpha Lens focus issue

[sam1275]

Hello, I have a Indigo Alpha: https://www.eevblog.com/forum/thermal-imaging/does-a-swir-camera-sensitive-to-thermal-energy/msg1035318/ which comes with a 15 degree lens, the picture will only remain clear on objects between 60-80cm from camera, other will out of focus, I tried my best to rotate the Lens bare handed, but it's very firm and refuse to move, how can I adjust the focus? Thanks.

[Fraser]

Hiya,

Two types of lens mount method are common on the Indigo cameras.

The lens is either a slide fit, retained by a collar that grips the lens barrel, or a screw fit with fine thread and locking grub screw to prevent movement due to vibration. Both lens mount options were offered for the same camera model.

I regret I have no specific information on the ALPHA model that you own. Having looked at your picture though, I believe you have the screw thread mount with grub screw locking. The user manual may provide adjustment detail.

A stiff lens screw thread is commonly caused by the following:

1. Distortion of the fine screw thread on the lens barrel by an overtightened grub screw.
2. Thread locking fluid on the lens threads. Common in industry.
3. Old optical grease on threads that has solidified with age (common)
4. Drop damage with an impact to the lens front causing damage to lens barrel or threads. Usually obvious from physical marks on lens barrel.

Ensure the tiny grub screw is fully released before attempting to adjust lens. I usually remove the grub screw and look into the hole to see the lens barrel thread at the bottom. This confirms a threaded mount and the condition of the threaded section under the grub screw touch point.

To release a lens that is stuck due to hardened grease on the threads I often apply a releasing agent/mild lubricant such as IPA or WD40. Once the lens Is removed I clean the threads on both lens and camera with IPA and lubricate with optical thread grease. Vasalene Petrolium Jelly will also work OK. Only a small, amount is needed.

There is a weird aspect to your situation though.......

In your pictures your cameras lens appears to be fully retracted into the lens mount, as evidenced by the lens barrel finger grip ring being up against the mount ring. That should provide infinity focus ! The distance between the back of the lens and the microbolometer sets the focus as I suspect you know. The greater the distance between the two, the closer the focus point. Your lens to microbolometer distance appears to be too great and needs reducing.

In old visible light CCTV cameras it was often possible to set the lens to sensor backfocus distance by moving the actual sensor inside the camera ! Some needed the case to be removed for adjustment whilst others had a screw on the rear or side of the camera case that operated an adjustment mechanism. The mechanism moves the sensor on an internal 'sled' to set the correct distance between the sensor and lens.

The Alpha should have a simple focus adjustment but without knowing the history of the camera, it is possible that it was set up for close focus by positioning of the microbolometer inside the case with spacers moving it further away from the lens to achieve very close focus. Production line applications have such a requirement. There is always the possibility that your Alpha is fitted with a close focus lens for its original application ! If such is the case, you may not be able to increase its focus distance without modification.

Let us know how you get on with adjusting you cameras focus.

Fraser

[sam1275]

Hiya,

Two types of lens mount method are common on the Indigo cameras.

The lens is either a slide fit, retained by a collar that grips the lens barrel, or a screw fit with fine thread and locking grub screw to prevent movement due to vibration. Both lens mount options were offered for the same camera model.

I regret I have no specific information on the ALPHA model that you own. Having looked at your picture though, I believe you have the screw thread mount with grub screw locking. The user manual may provide adjustment detail.

A stiff lens screw thread is commonly caused by the following:

1. Distortion of the fine screw thread on the lens barrel by an overtightened grub screw.
2. Thread locking fluid on the lens threads. Common in industry.
3. Old optical grease on threads that has solidified with age (common)
4. Drop damage with an impact to the lens front causing damage to lens barrel or threads. Usually obvious from physical marks on lens barrel.

Ensure the tiny grub screw is fully released before attempting to adjust lens. I usually remove the grub screw and look into the hole to see the lens barrel thread at the bottom. This confirms a threaded mount and the condition of the threaded section under the grub screw touch point.

To release a lens that is stuck due to hardened grease on the threads I often apply a releasing agent/mild lubricant such as IPA or WD40. Once the lens Is removed I clean the threads on both lens and camera with IPA and lubricate with optical thread grease. Vasalene Petrolium Jelly will also work OK. Only a small, amount is needed.

There is a weird aspect to your situation though.......

In your pictures your cameras lens appears to be fully retracted into the lens mount, as evidenced by the lens barrel finger grip ring being up against the mount ring. That should provide infinity focus ! The distance between the back of the lens and the microbolometer sets the focus as I suspect you know. The greater the distance between the two, the closer the focus point. Your lens to microbolometer distance appears to be too great and needs reducing.

In old visible light CCTV cameras it was often possible to set the lens to sensor backfocus distance by moving the actual sensor inside the camera ! Some needed the case to be removed for adjustment whilst others had a screw on the rear or side of the camera case that operated an adjustment mechanism. The mechanism moves the sensor on an internal 'sled' to set the correct distance between the sensor and lens.

The Alpha should have a simple focus adjustment but without knowing the history of the camera, it is possible that it was set up for close focus by positioning of the microbolometer inside the case with spacers moving it further away from the lens to achieve very close focus. Production line applications have such a requirement. There is always the possibility that your Alpha is fitted with a close focus lens for its original application ! If such is the case, you may not be able to increase its focus distance without modification.

Let us know how you get on with adjusting you cameras focus.

Fraser

Thank you VERY much Fraser!
I feel so lucky to have a specific analyze from a experienced person like you
As shown in photo, there's no locking screw on my camera.
I just notice there is a missing screw for the camera case, so it might be disassembled.(It's on the top side, so didn't shown in my photo.)
I also noticed there's a very tiny crack on the lens, donno if it's dropped.
Both evidence are new to me, I didn't notice them until today...
I may try tear it down and see if the sensor can be adjusted.
Also, how to check if the Lens is a close focus lens?
I'll report back if there's any progress.
Thank you again!

[Fraser]

Hiya,

I thought I could see a grub screw hole in the cameras lens mount outer ring in your picture ?? Please look closely for a small hole in the mount flange of the camera and check if it is empty.

Fraser

[sam1275]

Hiya,

I thought I could see a grub screw hole in the cameras lens mount outer ring in your picture ?? Please look closely for a small hole in the mount flange of the camera and check if it is empty.

Fraser

Hi Fraser.
There are 4 of them, all are empty, and the picture shows 2 of them.
I looked into the hole and I can see the bottom end of the lens, I mean the lens seems not fully retracted into the lens mount. But it's stiff anyway.
Also, is the locking ring part of the camera?
Thank you.
Sam

[sam1275]

Okay, I disassembled it and have a few findings:
*There are 4 boards inside the camera, one on rear, one on front, one on bottom, and one on side, they are plugged together by connectors similar to IDE for laptops, but smaller. There are also some smaller connectors with only 2 pins.
*The sensor is made by Boeing company And it have a vacuum tail and a round surface, and a valve-style pin layout.
*The shutter is inside the lens mount, not on board.
*There's a biggest chip on the bottom, with some material filled the gap to the case, so the tripod mount may also function as a heatsink I guess.
So it's a interesting tear down to me, but the sensor is not adjustable, so I reassembled it back and still have to deal with the stiff lens.

[sam1275]

Hi Fraser, I don't have WD40 and I'm not sure what's IPA...
Can I just drop some machine oil into the holes and try to turn it?
Edit: I found it, IPA is iso-propyl alcohol... I don't have it.

[Fraser]

Hiya,

I regret I have no ALPHA specific data on lens removal. It should unscrew BUT it could be a fixed focus lens that is securely mounted to the camera. i.e not intended to be removed ! If it does not turn clockwise or anti clockwise with reasonable effort, do not force it. I presume that you have tried clockwise rotation to see if the lens has a manual focus range of movement ?

The beveled mount that sits around the rear of the lens is part of the camera face plate assembly and likely held in place by screws from the inside of the camera face plate. The only way to really be sure how the lens is mounted is to separate the camera front plate from the rest of the camera and look at the inside of the lens barrel fro evidence of parts that should separate, such as threaded sections. Applying excessive rotational force to the lens without knowing the mounting method could end badly so I do not recommend taking a pipe wrench to it ! Hand grip only and then do not go mad twisting it. A clockwise then anti-clockwise twist will normally reveal any movement in the lens mount threads. If none is felt, the lens may be rigid mounted and not intended to unscrew. If the lens does move slightly, you can keep rocking it back and forth to see if it loosens. Adding a small amount of very thin oil is permissible but such should not be allowed to get on the FFC flag or microbolometer window. Only a tiny amount of penetrating oil is often needed to release corroded aluminium lens threads as capillary action spreads it around.

Fraser

[sam1275]

Hiya,

I regret I have no ALPHA specific data on lens removal. It should unscrew BUT it could be a fixed focus lens that is securely mounted to the camera. i.e not intended to be removed ! If it does not turn clockwise or anti clockwise with reasonable effort, do not force it. I presume that you have tried clockwise rotation to see if the lens has a manual focus range of movement ?

The beveled mount that sits around the rear of the lens is part of the camera face plate assembly and likely held in place by screws from the inside of the camera face plate. The only way to really be sure how the lens is mounted is to separate the camera front plate from the rest of the camera and look at the inside of the lens barrel fro evidence of parts that should separate, such as threaded sections. Applying excessive rotational force to the lens without knowing the mounting method could end badly so I do not recommend taking a pipe wrench to it ! Hand grip only and then do not go mad twisting it. A clockwise then anti-clockwise twist will normally reveal any movement in the lens mount threads. If none is felt, the lens may be rigid mounted and not intended to unscrew. If the lens does move slightly, you can keep rocking it back and forth to see if it loosens. Adding a small amount of very thin oil is permissible but such should not be allowed to get on the FFC flag or microbolometer window. Only a tiny amount of penetrating oil is often needed to release corroded aluminium lens threads as capillary action spreads it around.

Fraser

Thank you very much!
Yes I tried both clockwise and counter-clockwise, and I tried my best but the Lens is not moving a bit, although I'm not strong and it's a bit slippery between my hand and the lens. I think oil may not help either...
I did remove the front plate during the tear down, but I didn't examine it carefully, I think I may have to disassemble it again.
If it's "secure mounted", can I still adjust it somehow?
Sam

[Fraser]

Hi Sam,

If you can get some decent pictures of the area inside the rear of the lens and the rear of the camera face plate I may be able to advise further. Sadly I have not been able to find any references to the ALPHA having a user interchangeable lens. It may well be fitted and set at manufacture but anything that can be set, should be able to be 're-set'  Even fixed focus lenses need some adjust for correct minimum focus distance.

The fact that the lens has no signs of movement suggests that it is securely mounted on the camera. In some lenses, internal lens elements are used to set the focus whilst the front and rear lenses remain static. The adjustment is normally on the lens barrel or via a set screw in the rear of the lens that turns a worm drive rhat in turn moves the mid mounted lens element.

If the lens is designed for close up focus only, I regret you would have to consider modifications in order to achieve a longer focus range and there are no guarantees that the lens will perform well at such distances. Hopefully this is not the case though.

Bess Wishes

Fraser

[sam1275]

Hi Sam,

If you can get some decent pictures of the area inside the rear of the lens and the rear of the camera face plate I may be able to advise further. Sadly I have not been able to find any references to the ALPHA having a user interchangeable lens. It may well be fitted and set at manufacture but anything that can be set, should be able to be 're-set'  Even fixed focus lenses need some adjust for correct minimum focus distance.

The fact that the lens has no signs of movement suggests that it is securely mounted on the camera. In some lenses, internal lens elements are used to set the focus whilst the front and rear lenses remain static. The adjustment is normally on the lens barrel or via a set screw in the rear of the lens that turns a worm drive rhat in turn moves the mid mounted lens element.

If the lens is designed for close up focus only, I regret you would have to consider modifications in order to achieve a longer focus range and there are no guarantees that the lens will perform well at such distances. Hopefully this is not the case though.

Bess Wishes

Fraser

Hello Fraser,

Photos First:





So... it doesn't have any visible screws, I also checked other angles not shown in photos, the inner ring is the same all of the round.

And as you can see, there seems to have some glues inside, I can also see a bit on the front lens from outside...

 

So is it fixed and not adjustable? And is it even impossible to remove/change the lens without hard modding?

A interesting thing is there are 4 wires to the lens, 2 of them must be the FFC shutter, what about the others? For aperture?

Thanks,
Sam

[mikeselectricstuff]

A interesting thing is there are 4 wires to the lens, 2 of them must be the FFC shutter, what about the others? For aperture?

Could be the shutter has seperate coils to open & close, or temperature sensing, or anti-condensation heater

[sam1275]

A interesting thing is there are 4 wires to the lens, 2 of them must be the FFC shutter, what about the others? For aperture?

Could be the shutter has seperate coils to open & close, or temperature sensing, or anti-condensation heater

Thank you.
It's unlikely to be separate shutter coil, because they connected to different board.
I think the temperature sensing is the most likely...

[Fraser]

Hi Sam,

Thanks for the pictures.

The four wires are FFC shutter and lens temperature sensor. It is unusual to find the FFC shutter within the actual lens but the temperature sensor is commonly placed in the lens barrel as the temperature of the Germanium lens element is needed fro radiometric measurements especially in high ambient temperatures.

The lens has all the appearance of a fixed focus unit and it is not user changeable. You may recall that Bill commented that his ALPHA has its FFC shutter on the front of the lens ! This suggests that the ALPHA is not untended to have its lens removed or changed. Bill may know whether the lens focus may be changed on his version.

I regret that it appears that your ALPHA was specified for a particular task, machine vision is a possibility. Such cameras were used on production lines to monitor the temperature of key components. Such cameras commonly have a limited focus range either variable or fixed for close working.

Fraser

[sam1275]

Hi Sam,

Thanks for the pictures.

The four wires are FFC shutter and lens temperature sensor. It is unusual to find the FFC shutter within the actual lens but the temperature sensor is commonly placed in the lens barrel as the temperature of the Germanium lens element is needed fro radiometric measurements especially in high ambient temperatures.

The lens has all the appearance of a fixed focus unit and it is not user changeable. You may recall that Bill commented that his ALPHA has its FFC shutter on the front of the lens ! This suggests that the ALPHA is not untended to have its lens removed or changed. Bill may know whether the lens focus may be changed on his version.

I regret that it appears that your ALPHA was specified for a particular task, machine vision is a possibility. Such cameras were used on production lines to monitor the temperature of key components. Such cameras commonly have a limited focus range either variable or fixed for close working.

Fraser

It's a sad news to me... But is it able to buy a concave lens and put it in front of the camera? I think this would help it focus infinite without modding itself.

[Fraser]

Hi Sam,

Sadly such a converter would be somewhat more complex than just a concave lens. The only simple way to achieve a longer focus distance would be to increase the distance between the lens rear and the microbolometer.  Try placing a simple card spacer between the cameras front panel an the camera chassis. some experimentation may reveal what can be achieved by moving the lens further array from the sensor by a few mm.

If that approach works, you can make up a more permanent spacer from aluminium or plasticard (model shops sell it in various thicknesses.). Even an old credit card could be pressed into service ! If the lens is fixed focus it should have a decent depth of field. Thsi is quick and easy to try and a lot less complex than changing the optics.

Fraser

[sam1275]

Hi Sam,

Sadly such a converter would be somewhat more complex than just a concave lens. The only simple way to achieve a longer focus distance would be to increase the distance between the lens rear and the microbolometer.  Try placing a simple card spacer between the cameras front panel an the camera chassis. some experimentation may reveal what can be achieved by moving the lens further array from the sensor by a few mm.

If that approach works, you can make up a more permanent spacer from aluminium or plasticard (model shops sell it in various thicknesses.). Even an old credit card could be pressed into service ! If the lens is fixed focus it should have a decent depth of field. Thsi is quick and easy to try and a lot less complex than changing the optics.

Fraser

Thank you very much.
But are you sure it will focus further when I INCREASE the distance between the lens and the sensor? As you mentioned previously, it should provide infinite focus if I can screw the lens nearer to the sensor, or am I misunderstood?
By the way I still think a simple concave thermal lens would increase the focus distance, because it will just work like a glasses for the near-sighted. Although I didn't ever seen such a lens for thermal camera...
I'll do a experiment of the relation between the sensor-lens distance and the focus distance.
Sam

[Fraser]

Ooooops sorry. You are absolutely right. I am so used to modifying stuff for near focus using spacers. Brain fade moment. Apologies.

I shall think some more about your lens and comment further if I have any thoughts to share.

Please PM me your email address.

Fraser

[Bill W]

The lens has all the appearance of a fixed focus unit and it is not user changeable. You may recall that Bill commented that his ALPHA has its FFC shutter on the front of the lens ! This suggests that the ALPHA is not untended to have its lens removed or changed. Bill may know whether the lens focus may be changed on his version.

Yes it does focus, and to infinity.  It looks pretty similar to this one from memory, I'll have to have a closer look and see if there are any more clues to fix Sam's one.


Bill

[sam1275]

Ooooops sorry. You are absolutely right. I am so used to modifying stuff for near focus using spacers. Brain fade moment. Apologies.

I shall think some more about your lens and comment further if I have any thoughts to share.

Please PM me your email address.

Fraser

Thank you, no need to apologies
Email sent.

[sam1275]

The lens has all the appearance of a fixed focus unit and it is not user changeable. You may recall that Bill commented that his ALPHA has its FFC shutter on the front of the lens ! This suggests that the ALPHA is not untended to have its lens removed or changed. Bill may know whether the lens focus may be changed on his version.

Yes it does focus, and to infinity.  It looks pretty similar to this one from memory, I'll have to have a closer look and see if there are any more clues to fix Sam's one.


Bill

Thank you Bill, would you please tell me whether your camera have adjustable focus, and have a removable lens?

[Bill W]

It is adjustable focus, the lens is essentially fixed, there is no bayonet to switch lenses for example.

I'd expect it was calibrated with the lens so exchanging lens types would cause calibration problems.

regards
Bill

[sam1275]

It is adjustable focus, the lens is essentially fixed, there is no bayonet to switch lenses for example.

I'd expect it was calibrated with the lens so exchanging lens types would cause calibration problems.

regards
Bill

Thank you very much!

[Bill W]

Hi Sam,

Had a look and the camera is identical but mine has a different lens (40 FoV).  The sensor is in the same position.  The lens focusses fine and mounts the same way.  I suspect something not right with your lens.

regards
Bill

[sam1275]

Hi Sam,

Had a look and the camera is identical but mine has a different lens (40 FoV).  The sensor is in the same position.  The lens focusses fine and mounts the same way.  I suspect something not right with your lens.

regards
Bill

Hi Bill W,
Thank you very much. I also remember that my 15 degree FOV lens is also a standard one for Alpha, so it shouldn't be designed as fixed focus, also there's a manual grub on mine but very stiff...
Would you please check if your lens also have those suspicious glue trace as mine shown in my pictures? I think there might be someone added those glues to it. Is it possible to use some kind of liquid solution to soften/dissolve/remove those glues?
Sam