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04-23-2013, 10:47 PM   #1
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laser focus assist light (home made)?

LaurenOE mentioned on another thread using a red dot scope (rifle scope) to help aim his k-01. This scope just projects a red dot inside the scope but I misunderstood and thought he was using a laser sight. It got me thinking about my sony v1 camera that uses a laser hologram auto focus assist light. Basically it is a grid of laser lines. It has night shooting capabilities (pulls the ir cut filter out of the way), and can auto focus in darkness using the laser grid. I got to wondering if a laser would help the k-01 with low light focus. I picked up a cheap laser pointer at the dollar store. While it wasn't a cure all, it certainly seemed to sometimes help. It even focused correctly at times in very low light where the camera alone didn't have any chance of focusing. It seemed about half the time it blew the focus, but you could tell before shoting if the focus was right. If the focus was right, the laser dot was a small dot. If it didn't focus right, the laser dot was expanded out. I tried it a little in low light and it seemed to sometimes help and or allow focus when the camera otherwise couldn't.

So does anyone have any thoughts on building a laser focus assist light? I got a few more laser pointers. I taped them together with the buttons taped down and they seemed to help but it was hard to get the beams confined to a small area. I have included a pic of what the sony v1's laser grid looks like, and what the laser pointers look like. I'm tearing the guts out of a few and trying to mount them (I'm thinking I don't have everything I need handy right now but I will start thinking of ideas).

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04-23-2013, 11:11 PM   #2
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Excellent idea and one that I've pondered as to why they don't use more. Personally my recommendation is to use IR (Infra Red) light and a suitable sensor in the camera to read it. I have experience with IR flood lights with military night vision goggles (NVG's). Each one is equipped with a "flash light" (more used for covert signaling, but does work to brighten things up), but it can only be scene when looking through the NVG's. I can't help but feel this would help because they can make it as bright as they want, and it won't affect the subject by blinding them because they won't be able to see it. Just another visit I had from the Good Idea Fairy

Regarding your implementation, I would recommend against using multiple lasers. One is for accuracy (they have to be aligned perfectly of their lasers might not meet because of angle variations, and the further the focus point/subject, the greater this is exagerated, to the point where the lasers may not land on the subject together). Also, it creates multiple lasers to increase the risk of damage to the subject, assuming you are focusing on a person (I hope not, and if you are, please read into the damage lasers can do to human eyes, but I am confident this is not news to you).

To mitigate the need for multiple lasers, and to make the laser a bit less dangerous to your subjects, I recommend fashioning a "gobo." Short for "Goes Between," it is a common application to advanced strobism lighting. Basically you put something between your light source and the subject being lit. You may not be aware of them, but I guarantee you've come across them. Here's an example:



Using the same idea, just on a much smaller scale, fashion a grid of sorts using your finest (in terms of smallest, not nicest lol) sewing needles and place it directly in front of the laser. Use something that is not permeable to the laser light (thick and black paper should do the trick) so there are clearly defined dots leaving the laser as opposed to just the entire laser strength but diffused. Experiment with different size dots, number of dots, distance between the dots, etc.

This should also make it a lot simpler in terms of sychronizing all the laser dots to be triggered at the same time

Hope this helps, and I commend your desire to hack.

-Heie
04-23-2013, 11:53 PM   #3
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Thanks for the advice. I am aware of the dangers of lasers and your eyes. This was/is going to be a push button kind of thing so I can push the button, focus, release the button, recompose and shoot (not getting the laser near someones face if shooting a person). I was thinking something mounted in the hot shoe to keep it stable. The thought of modifying the beam had crossed my mind (at least in respect to using a lens). I used to have a laser pointer where you could twist the top and get different patterns (it had different lenses). It would be nice if I could find that (not sure if I still have it). I also bought a mini flashlight when I bought the laser pointers and tried the lens off it to spread the beam but no luck. It would be really nice if I could split the beam into some sort of grid. I'll try your idea with interrupting the beam. I'll just have to find suitable material. One thing that is a bit limiting is these lasers are not very strong (when I say I got them at a dollar store, I mean they were actually a dollar each).

As far as aligning the lasers, I was thinking of mounting the boards from inside the laser pointers with some sort of screw adjustment to align them. It would be a lot better if I can come up with a good way to split the beam. Even if I used a couple of lasers, I would much rather have lines or a grid rather than a dot.

It kind of makes me curious about the sony camera and its laser grid (and peoples eyes). I wonder if it is not strong enough to do damage (it seems pretty strong).

I have a feeling this is going to be another one of those complicated projects so I might be working on it for a while.

The sony v1 camera has an ir light too (I think it only uses it in night mode with the ir filter pointed out of the way). I have no idea why they don't use that laser focus on more cameras. It works great.
04-24-2013, 12:47 AM   #4
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OMG, this really puts new meaning to "nailing the eye"!

Also, don't take pictures of airplanes with that device. Pointing a laser pointer at an airplane is regarded as an act of terrorism around my parts of the world.

04-24-2013, 02:29 AM   #5
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I ran across one possibility (maybe). I noticed the pattern on the sony camera got bigger further away. Outside with dim light from streetlights it gets hard to see past maybe 40 feet (except when it hits a tail light on a car and such, then it can be seen much further). The laser pointer shots much further. I have various pieces of broken lenses as well as macro filters. It seems I can pretty easily make the beam spread in a similar manner. Its just a matter of finding a lens element or group with the right spread (too much spread and it no longer helps as it is a weak laser). Painting the lens and then removing paint in spots might help shape the laser to. This would also limit its range if I can find a suitable lens. I found suitable macro lenses, but they are cheap (uncoated or poor coatings) and most of the laser gets reflected back. It seems the elements out of broken lenses work better.
04-24-2013, 04:44 AM   #6
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I believe that Sony stopped putting that laser grid into cameras a few years ago because of concerns from Government officials and safety groups. I have an older High-end DV format video camera from Sony that uses that technique and it nailed focus better than any camera I have ever used - even in complete darkness.
04-24-2013, 04:48 AM   #7
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I remember laser pointers being sold in Chinatown that had heads with different patterns (star, mickey mouse, etc). I'll check to see if I can get those, and if they help.
04-24-2013, 04:51 AM   #8
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I found it in my Sony manual, its called Hologram AF Laser assist. It was available around 2003 and disappeared a couple years later from their lineup as far as I can tell.

04-24-2013, 05:02 AM   #9
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QuoteOriginally posted by ripit Quote
I ran across one possibility (maybe). I noticed the pattern on the sony camera got bigger further away
Of course it does. It's a hologram

QuoteOriginally posted by JinDesu Quote
I remember laser pointers being sold in Chinatown that had heads with different patterns (star, mickey mouse, etc). I'll check to see if I can get those, and if they help.
Yes, you can use that. It's much better than the single dot created by a laser pointerr, and less dangerous to the eyes also. It's exactly the same principle as the pattern of lines that Sony used. The single dot can be hit and miss because the AF system might or might not notice it. The pattern created by a hologram is larger and will be easier to catch for the AF system.

"But wait, we all know holograms are really 3D thingies, right?" Sort of, but only when they are lit via two synchronized light sources. With a laser you have one light source, so no 3D.
04-24-2013, 10:39 AM   #10
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At this point I see 3 possible options.

Try something with the laser pointers I have and lenses. I have a zoom lens assembly (basically 2 groups of elements that can move away from each other in a tube. It makes the dot range from 3"-6" at about 30 feet. It did give more change but apparently there was a loose ring and the 2 elements dropped out of one group on the floor. Only being 2 elements, I can of course try different combinations to see what I get. I have another lens in a collar that would mount well to the zoom tube, and then I can get anywhere from a dot to about a 8" circle (looks a bit faint at full size at 30 feet). It has an aperture in it that I would have to tie open or remove (smallest hole is to big to effect the laser so maybe I could leave it but then the laser would need to shoot through the hole and multiple lasers would be out). It also has a tube that might need to be cut back. These are partial assemblies out of zoom lenses by the way. Partially painting the lens to produce a patern would be an option.

The second (and much better option) would be to get a laser pointer with lenses built in to project a pattern. I even saw some that would project a grid of dots. As this would probably be shipped direct from china, It will probably be a few weeks after I decide what to buy so I have some time to play with idea 1 (which cost mo nothing).

There are also lenses designed for laser projectors that look kind of like a slide. I want to look into them a little more.

So what about laser color? With with the laser pointers that have built in lenses to project some sort of pattern or image, there are red, green and maybe blue. The af assist light on the k-01 is green. Is there some advantage to green light for this camera, and if so would a green laser work better? I'm kind of wondering if the ir cut filter is killing a bit of the laser intensity to?
04-24-2013, 10:50 AM   #11
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If it's CDAF, I would wildly guess that because a bayer sensor has twice as many green sensors as blue and red, the sensor would react better to a green laser.
04-24-2013, 11:11 AM   #12
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QuoteOriginally posted by ripit Quote
LaurenOE mentioned on another thread using a red dot scope (rifle scope) to help aim his k-01.
LOL...I'm female...as in *she*

Also the red-dot doesn't project, it just illuminates on the scope.
I don't think projecting a red-dot is a good idea when dealing with wildlife or human subjects.

The only laser I use, if for my Cactus Laser trigger.

04-24-2013, 11:15 AM   #13
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QuoteOriginally posted by JinDesu Quote
If it's CDAF, I would wildly guess that because a bayer sensor has twice as many green sensors as blue and red, the sensor would react better to a green laser.
Thanks for the info. I guess thats why they use a green focus assist light on the k-01. I guess I'll look for a green laser pointer with projection lenses.
04-24-2013, 11:28 AM   #14
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QuoteOriginally posted by LaurenOE Quote
LOL...I'm female...as in *she*

Also the red-dot doesn't project, it just illuminates on the scope.
I don't think projecting a red-dot is a good idea when dealing with wildlife or human subjects.

The only laser I use, if for my Cactus Laser trigger.

Sorry, I guess I could pay attention to user names and icons (I was up pretty late last night). I have played with the red dot scopes but it was a long time ago. I just misunderstood at first and though you were talking about a laser site. Even after I realized my mistake the idea of using a laser still stuck though as it works so well with the sony camera.
04-25-2013, 12:02 AM   #15
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QuoteOriginally posted by ripit Quote
Thanks for the info. I guess thats why they use a green focus assist light on the k-01. I guess I'll look for a green laser pointer with projection lenses.
No, you don't want to use (point) a green laser pointer on human subjects either.

BTW, I also have the Sony V1, and have always been amazed that they put the laser function in the camera (makes it a collector's camera, along with the night vision feature and ability to shoot IR). The camera came out 9-10 years ago which was not that long ago. The concern about laser pointers was well in force at that time too. So, it is not just a safety concern today.
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