Projector on the knee

    It happens to me - you wake up in the middle of the night and think: “Interestingly, until the morning for a long time? Need to try to fall asleep or is there no sense? ” At this point, take a look at the watch, but:

    1. I am shortsighted, so any desk clock with a character size less than 20 cm is useless;
    2. Sleeping in a wristwatch is uncomfortable, and even at night on an analogue dial watch a damn thing is still not visible;
    3. The phone is infinitely far (distance more than 1m) from the bed, and getting up to decide whether you need more sleep is somehow not logical.

    In this regard, I had a long-standing idea to buy projection clocks that project time onto the ceiling, but it is also not so simple, because, firstly, they need to be bought. Especially for the sake of them, you won’t go to the store, but you can’t buy “at the same time” - you forget. Secondly, it is necessary that they "shine" into the ceiling constantly, because it’s not too lazy to press a button, but to put a watch next to a berth so that it is convenient to press a button does not work. I didn’t find a “constant light” problem - I didn’t find a clock shining immediately out of the box, and it wasn’t very interesting for the collective farm to “hold the button forever and solder the external power supply”.

    And then it happened that my Huawei P1 phone broke, so it stopped being a phone, but everything else in it, in general, worked. It’s impossible to sell, but it’s a pity to throw it away, and the brain inflamed by such a contradiction began to look for a place for the application of a half-working device.
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    What happened next - under the cut.

    The school experiment with the pinhole camera seems to have forever imprinted in consciousness. I always wanted to do it myself, but somehow my hands did not reach. And then there were very favorable circumstances for creating a device that was very similar in design, and a projector in terms of the effect of the direct opposite. The residual school knowledge on optics was enough to figure out that in order to create a masterpiece, in general, you need only three things: the “radiating matrix”, the focusing lens and the body. P1 could well have acted as the first, to make a case out of some shoebox was not impossible, to find a clerical magnifier in a nearby office supply store for 50 rubles also did not look like a man. After that, it was necessary to bring some hours to P1, project them onto the ceiling, and, woofing, the problem with nighttime commotion was solved.

    The raid to the stationery store ended with the purchase of 75mm magnifying glass, the rustling of the bins of the motherland - the capture of Intel NUC boxes in the cabinet. Here you need a digression on why exactly the box from under the NUC. There are two reasons for this. First: it is made of very good cardboard - dense and beautiful. Second: it is designed so that the inside is inserted from the end into the outside. Such a device promised tremendous advantages in experiments with focusing - after all, the “matrix” could be fixed on the inside of the box, the lens on the outside and quite suitable to move one relative to the other, achieving focus. So the box from under the NUC supported the focusing mechanism directly from the box, for shoe boxes would have to be collective farmed on purpose.

    The first attempt to bring it all together, as usual, failed. It turned out that clerical magnifying glass is an extremely telephoto thing. Therefore, in order for the image to be focused, it was necessary either between the lens and the screen (read the ceiling, because THIS was supposed to project the image onto the ceiling) was about five meters, and I do not live in the Hermitage, I have 3 meters with a small ceiling or between the "matrix" and the lens was about 60 cm, which did not fit into my idea of ​​the correct dimensions of the projector. Convulsive searches led to a lens in a DYI tool called a “third hand” like this, which was immediately sacrificed by extraction of this very lens. It gave a much more proud result - the distance between P1 and the lens is about 20 cm, the distance between the lens and the ceiling is about 2 m, which was suitable for installing the device either on a table or on the head of the bed. However, as it turned out, this lens is of rather mediocre quality - with wild distortion and focal length, smoothly changing from the center of the lens to the edges. So it was possible to achieve that either the center of the image was in focus, or the edges, which of course did not suit me. Muti in the image was lacking due to myopia, I did not want it to be generated also by a projector. Thoughts about the lens from the camera frantically flashed through my head (they were immediately discarded, since the device, which was originally conceived as cost-free, and so already was not due to the purchase of office lenses. Adding a lens to the system made the idea generally quite expensive) to the lenses from the slide projector (my friends had these and could be picked up for free, but my friends were far away, and I wanted to do things here now). And then I remembered that I have a set of macro lenses for the camera, for photography it is extremely useless (I played 15 minutes when I bought and did not use it anymore) and cheap enough (4 pieces for 10 bucks) so that it would not be a pity to spoil it. Bought a long time ago, but for pictures that are extremely useless (played for 15 minutes when I bought and did not use them anymore) and cheap enough (4 pieces for 10 bucks) so that it would not be a pity to spoil. Bought a long time ago, but for pictures that are extremely useless (played for 15 minutes when I bought and did not use them anymore) and cheap enough (4 pieces for 10 bucks) so that it would not be a pity to spoil. Bought a long time ago, butit looks one to one. A lens marked + 10x fits perfectly. She kept a distance of 20 cm between the lens and the “matrix”, under which the seats for the “matrix” were already cut out in my box and gave a very sharp image over the entire area of ​​the frame.

    As a result, I have a device that projects the image from the phone from the head of the bed onto the ceiling.

    The diagonal of the image is about 1.5 meters. It is enough to consider the numbers, having myopia of almost any degree. True, there is one snag. As with any projector, the image from the matrix lens is flipped. Therefore, in order for the projected image to be “in the correct orientation,” the matrix must show it upside down. Those. The image must be flipped either horizontally or vertically. In fact, this is a problem, because I did not find a way to do such a trick in Android. Yes, there are separate applications, basically these are all sorts of HUDs that can do this, but for hours ... In this place, I refer to one of my previous articles , in particular, to this and thisscreenshots. The opportunity was drawn to display not only the clock, but also climate information, which is not that useful at night, but a nice bonus. It was very easy to undo an html page, it was enough to add scaleX (-1) to the CSS style of the page and voila:

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    Now it’s dry about the necessary process.

    Material List:


    Tool List:
    • Felt-tip pen
    • Stationery knife
    • Super glue


    Process


    The process will be described for the Intel NUC box, for other boxes the process will be more complicated, but there is no problem guessing how to implement it. So, we apply the lens in the middle of the closed end of the outer part of the box. We circle the lens with a felt-tip pen. With a clerical knife, cut a hole half a millimeter smaller than the circled ring. Insert the lens into the hole. Yes, this must be done with effort, but then it will not go anywhere during the experiments, and it will be possible to fix it simply by applying a little superglue to the place of contact between the lens body and the box. Take the "matrix", put it on the end of the inside of the box. We put the outer part on the inner one so that we get a “pie” (from bottom to top): the inner part of the box, the “matrix”, the outer part of the box. Thus, we got a stand for choosing the correct distance between the lens and the "matrix", After all, by adjusting the depth of dressing of the outer part of the box on the inside, you can control the focus. It should be mentioned that in my case the structure should project onto the ceiling, and, accordingly, stand upright, so there are no surprises with the “matrix” falling inside the box, gravity helps me. Further, choosing the depth of donning we achieve acceptable focusing. At this moment, pinpoint the depth of donning. By the depth of donning, we determine the distance between the "matrix" and the lens. After that, we remove the end face of the inner part of the box with which it enters the outer part, and in the inner gasket part we cut out the seat under the “matrix”, measuring the found distance from the end of the inner part. that in my case, the structure should project onto the ceiling, and, accordingly, stand upright, so that there are no surprises with the “matrix” falling inside the box, gravity helps me. Further, choosing the depth of donning we achieve acceptable focusing. At this moment, pinpoint the depth of donning. By the depth of donning, we determine the distance between the "matrix" and the lens. After that, we remove the end face of the inner part of the box with which it enters the outer part, and in the inner gasket part we cut out the seat under the “matrix”, measuring the found distance from the end of the inner part. that in my case, the structure should project onto the ceiling, and, accordingly, stand upright, so that there are no surprises with the “matrix” falling inside the box, gravity helps me. Further, choosing the depth of donning we achieve acceptable focusing. At this moment, pinpoint the depth of donning. By the depth of donning, we determine the distance between the "matrix" and the lens. After that, we remove the end face of the inner part of the box with which it enters the outer part, and in the inner gasket part we cut out the seat under the “matrix”, measuring the found distance from the end of the inner part. At this moment, pinpoint the depth of donning. By the depth of donning, we determine the distance between the "matrix" and the lens. After that, we remove the end face of the inner part of the box with which it enters the outer part, and in the inner gasket part we cut out the seat under the “matrix”, measuring the found distance from the end of the inner part. At this moment, pinpoint the depth of donning. By the depth of donning, we determine the distance between the "matrix" and the lens. After that, we remove the end face of the inner part of the box with which it enters the outer part, and in the inner gasket part we cut out the seat under the “matrix”, measuring the found distance from the end of the inner part.

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    We install the “matrix" in the

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    seat : We put the outer part of the box on the inside to failure. At this moment, the required distance is formed between the "matrix" and the lens, the entire projector is ready.

    Here is a photo of the projector from the end with the focus on the “matrix”:

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    And with the focus on the end of the box: The

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    projected image is very pale, this is understandable, after all, the energy emitted by the 4 "screen is smeared over a 60" image, i.e. "Brightness" drops 225 times. So during the day it is not visible, it is visible only at night, but I did achieve this.

    For those who have read to the end here is a photo of the result, taken from the ceiling with a shutter speed of 15 seconds:

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