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I wish to build a kind of fly tunnel with 2 light curtains for flying insects.
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I've never worked with a line laser, time to look how a laser line is working. My first test was if you can control a laser with short pulses. The tests showed that you can control the laser light even with a few us on time. Ideally suited to take a look into the laser itself.
The Mitutoyo 10X lens is used to look into the laser. Given laser light is quite powerful a short laser pulse was used, only 100 us. There was also used a short foreground illumination with 2 out of 6 of LED channels (top and bottom) and only 600 usec exposure. This was necessary in order to obtain greater depth in the image. Normally I use 6 channel and 2000 us as standard frontale exposure. The laser beam will give you a 650 nm light wave. During recording, you should very good measuring the red channel of your camera to obtain no saturation. This is perfectly adjustable by setting the proper pulse time of the laser. I use a resolution of 1 us in a range of 0 .. 99999 us. This time was set in my controller. (I have several additional output channels for new devices during the stacking.) For the stacking I use 75 images with 5 um step. Zone A and Zone B have a difference in depth of 350 microns.
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This 2D image already shows the variation of the laser light. But you really have to see the 3D version, best in full HD, to understand how the internal light actually expires. There are two horizontal zones, zone A and zone B which do not lie at the same depth. On a 2D picture you can not see it but the 3D version can be. It is remarkable that you see here two horizontal zones while the line of the laser beam will come out vertically . You can not see this here, just the more or less circular laser diode. Here is a very small 3D version, the Original can be used via the link. He has composed cross-view, so you can make your own version .mpo for a full HD screen.
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https://www.flickr.com/photos/fotoopa_h ... 09/sizes/l
What you see is that Zone A is more in front than Zone B. In Zone A the laser light come from the background and focuses on the Zone A line. Zone B is just the opposite. You see in Zone B in depth a sharp line and the laser beams coming out wider to the front. Sorry for 2D viewers, you can not see this ! I have taken a global view image so you can see better how the laser setup was during recording. (is also a 3D image)
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https://www.flickr.com/photos/fotoopa_h ... 23/sizes/l
I have made a crop from zone A in 3D. This picture proves that the laser beams arise very accurately because the 75 stacking photographs still show some pattern. Later this wil be confirmed better if we look at the projection beam in closeup. Only an 3D version, the 2D version has much less value.
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https://www.flickr.com/photos/fotoopa_h ... 61/sizes/l
Now we will go and see the projection of the laser beam. I need a line for my line array detector system. The question now is what will be a projection of a laser line. My first thought was to see a beautiful pure clear line. But this is not, the light shows a traveling wave. The greater the distance the more widly seem the projection wave. The wave is constant and starts always from the same place / corner. The analog signal on the detector array show the same results. I made two shots to show this. The first is has an 110 mm projection distance, the 2nd 210 mm. For my purposes I need 110 mm. the images are 2D images because the projections are perfectly flat.
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The pictures show the projection of the beam as well as the step size. To create these images, I have used 2000 us and 5000 us laserpulse instead of the100 us pulse to look direct into the lens. There is no foreground flash used. Curiously, the wave always comes back to the same place. This is a stable appearance. The wave is always at the same place. In my detector I must take this into account.
A measuring setup with the receiver line array you can see in this picture:
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A complete scan of the array with an object:
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A closeup detail of an object of 1.4mm that appears in the beam:
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A general view of waviness of the laser light on the array:
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This is a project in development. There is still quite a lot to measure and explore. Possibly many people know this already, but for me there were still some elements that I did not know and you did not find information easily.
Sorry for the long story!
Frans.
Updates:
foto_11 replaced by foto_10 error 2 times the same picture.
Added warning:
Warning:
Never look directly into the laser beam.
Just use a correct timing for the laser and start with a very low value. Test the hardware driver output with scope or logic analyser before the first use. So you are sure of the good working. Lasers are not toys, you should use them thoughtfully.