What to do if the project requires a small lens, but there is no suitable size in stock? Postpone the project and wander around flea markets, hoping to find a suitable donor? Not necessary. A lathe allows you to solve this problem:
I take a piece of the correct sheet of plexiglass of suitable thickness (in in this case, 6 mm). I have a special step machined on the front of the chuck jaws, which allows me to clamp not cylindrical, but sheet workpieces. It is convenient to sharpen bodies such as washers, etc., although of course one must take into account that the reliability of fixing the part is not very good. But processing plexiglass does not require much effort, and the workpiece must be clamped gently in any way.
In general, a 6-mm workpiece, clamped in these ledges, is machined just to half the thickness. And then it turns over and goes through again. We get a “washer”, a flat cylinder of the required diameter.
Using a cutter, operating with two feeds at once, I roughly give it a convex shape: 
Now I take a triangular scraper made from a needle file and draw out the shape, removing the marks from the cutter: 
This processing method allows you to literally “shave” plexiglass, removing thin, thin shavings in a flat layer. With any other method, ring risks remain.
True, the fingers are in close proximity to the rotating cams; on a large machine I would not risk doing this (rpm 800-1000).
Now a drop machine oil on a piece of “zero”, and finishing treatment: 
If the lens is required to be biconvex, then I turn the workpiece over and process the second side.
I remove it from the machine and finally polish it with a thread disk with GOI paste. The technique of polishing plexiglass differs from metal. I apply more paste to the disc, and the pressure is much less. Light and short-term touches, evenly moving the friction zone over the entire surface of the lens. Otherwise - “burnout”, and an irreparable marriage.
Finished lens: 
And this is the “lens”, that is, the mount for this lens: 
Fixation of the lens as in real optical systems, with a thin threaded ring. Although, of course, you can use an elastic release ring-spring, or if very simply, put it on glue :-) But a lathe also allows you to do everything “in an adult way”, on a fine-pitch thread (in this case, by selecting guitar gears pitch 0.7 mm is selected). Lens assembly: 
To prevent the lens from scratching too quickly, it is useful to make the outer edge of the tube several times. higher than the most convex point of the lens, this is obvious.
And here is the mechanism from a small women’s watch, for which this lens was made: 
As you can see, the optical qualities of the lens are quite satisfactory, despite the fact that the geometry was derived almost from scratch. That is, such a lens certainly won’t work for a telescope, but for a flash drive it’s very suitable :-)
Thank you for your attention.
Hi all!
My name is Sergey.
And in this post I want to tell you one of the uses of a 3D printer, namely making lenses.
The task was as follows. There is an RGB LED, but the light source from it is not in the form of a beam, but scattered with a divergence angle of about 38 degrees. In the sketch I showed the light source and the divergence of the rays, and determined the point where the LED crystal should be.
1/f=(n-1)(1/R1+1/R2)................................. ........................................................ ....................(1)
Where R1 and R2 are the radii of curvature of the first and second surfaces of the lens, f is the focal length of the lens, n is the refractive index of the lens.
n=n2/n1, where n2 is the refractive index of the lens material (plexiglass 1.5), n1 is the refractive index of the medium surrounding the lens (air, about 1)
For simplicity, I assumed that R1=R2.
I only know from the formula f - 20 mm. For us, in essence, this is the distance from the LED crystal to the optical center of the lens.
Let's rewrite formula (1), taking into account that R1=R2=R:
R=f(n-1)2 .................................... ........................................................ ...........................(2)
Substituting the data into formula (2) n=1.5 and f=20
we find that the radii of curvature of the lens surfaces are 20 mm. See schematic drawing.
Based on this data, we build a 3D model of the lens. It turns out something like this.
I made a lens with a base.
All that remains is to print it, which is also not difficult. Result after printing (printing only, no processing).
Afterwards I sanded the lens a little with 1500 sandpaper and polished it with paste. Unfortunately, the photo final result I didn’t have any of the lenses either.
All that remains is to test the lens in action. This is what the LED spot looks like without a lens
And so it is with the lens.
1. I was not able to achieve a parallel beam, but I think that if I re-manufactured the lens with different parameters, I would have been able to do this.
2. The divergence of the beams is reduced by more than 3 times (the customer was satisfied with this)
3. The refractive index was most likely used incorrectly. The lens is made of polymer and its refractive index is unknown.
4. The lens had to be made with a larger diameter.
The simplest electronic digital microscope can be made with your own hands using an old phone with a camera, although it is still better to use a smartphone (in our case, an iPhone) with a larger screen and a better camera.
The total magnifying power of the microscope can be up to 375 times, depending on the number and class of lenses used.
By the way, when making microscopes we took the lenses themselves from an old laser pointer, but if you don’t have one, then you can buy them cheaply in any Chinese online store.
Cost price homemade microscope does not exceed 300 rubles, if we take into account the cost of materials:
Materials for manufacturing
Full list necessary materials for the project:
Manufacturing
1) Disassembling the laser pointer and removing the lens.
For this we use the cheapest pointer, so do not buy expensive models for this. A total of 2 lenses will be needed. (You can skip this step if you buy the lens itself at the store.)
To disassemble the pointer, unscrew the back cover and remove the batteries. We remove all the insides using a simple pencil with an eraser. The lens is located in the lens, and to get it out you need to unscrew a piece of small black plastic.
The lens itself consists of thin translucent glass, about 1 mm thick, you can attach it to the phone camera to experiment with an enlarged photograph, it is very difficult to take a high-quality photograph, so I decided to make a clamp for the microscope.
2) Making the base of the body.
The entrance was a piece of plywood measuring 7 x 7 cm, in which we drill 3 holes for racks (bolts). The places for drilling holes are shown in the photo with marks.
3) Preparation of plexiglass and lenses.
We cut out 2 pieces of plexiglass with dimensions: 7 x 7 cm and 3 x 7 cm. On the first piece of plexiglass we drill 3 holes according to the plywood template, this will be top part housings. On the 2nd piece we drill 2 holes according to the plywood template, this will be the intermediate shelf of the microscope.
When drilling plexiglass, do not press hard.
Now you will need to drill holes in the plexiglass for the lens and lens, this will require a D = D lens drill or slightly smaller. We make the final adjustment of the hole using round files or rasps.
Lenses must be built into drilled hole in both glasses.
4) Housing assembly.
When all the parts of the microscope are ready, you can begin the assembly itself, but before that there is still 1 point left:
- it is necessary to supply a light source from below, for this I drilled a hole in the lower part of the case for mounting a small diode lamp.
Let's get started final assembly. We tighten the bolts tightly to the base.
The intermediate stand of the microscope with the o 2 lens must be placed up and down so that the size of the magnification can be adjusted with the optics.
To do this, tighten wing nuts and 2 washers onto 2 bolts and mount the glass with a 3*7 cm lens already glued in.
Then we install the top cover, here we already use ordinary nuts, but we place them on both the top and bottom.
Congratulations, you have just made a cheap digital microscope, here are some photographs taken with it.
Video instructions for production and demonstration of work
(in English)
One of the undeniable advantages of LEDs over traditional light sources is the ability to create almost any luminous flux distribution for maximum effective use energy. This formation is carried out using secondary optics - a reflector (reflector) or lens.
To denote the shape of light distribution in lighting engineering, the term “luminous intensity curve” or abbreviated as LSI is used. LEDs in most cases have a primary lens (transparent silicone or glass), which forms the CSS shown in the figure below.
As can be seen from the graph, the light intensity gradually decreases with increasing angle of deviation from the central axis. To obtain a different type of distribution, a lens or reflector of the appropriate type is superimposed on the LED. Hence the name – secondary optics. Reflectors have enough limited area applications - they allow you to work only on the concentration of the light flux, i.e. decreasing the radiation angle. Lenses provide a wider range of possibilities, so it’s worth considering them in more detail.
The most common materials for making lenses are polymethyl methacrylate (commonly known as plexiglass) and polycarbonate. They are manufactured by injection molding, in strict compliance with technological standards. So making your own lenses is out of the question. When you try to mechanically process these materials, all you can achieve is a dull, scratched piece of plexiglass.
Methods for pairing with LED
There are several ways to mount lenses. The simplest one is gluing. Lenses, small size Can be glued directly to the LED board. Larger and more massive ones require a holder. The holder has an adhesive base with a protective film (essentially double-sided tape), and the lens simply snaps into it. An ideal option for products made by hand at home, but not reliable enough for harsh operating conditions (temperature changes, mechanical shaking and vibration). The second method - fastening with screws - is more reliable, but requires the presence of appropriate structural elements at the lens. And finally, you can attach the secondary optics using the body elements of the product (lamp, flashlight, etc.). For example, press down with protective glass. Anyway great importance has precise alignment of the lenses relative to the LEDs; for this purpose, some lenses and holders have special stands (pins). Naturally, the corresponding holes must be provided on the board. When installing, do not touch the working surfaces of the lens with your hands.
Types of lenses
Typically, the manufacturer classifies lenses according to two main criteria - by the type of LED and by the type of light distribution. Also, optics can be single and group, when a single lens module is put on several LEDs, transparent and matte, symmetrical and asymmetrical, etc.
Currently, manufacturers of secondary optics are “keeping pace” with manufacturers of light-emitting diodes, and after the appearance of a new type or family of LEDs, in almost a couple of months we can already purchase corresponding new lenses for it.
The most common form of light distribution is circularly symmetrical. These lenses produce a round light spot. The angle of the light beam can be completely different: from 3˚ to 150˚. Concentrating lenses with an angle of less than 10˚ are usually called “spot” (from the English Spot - spot).
There are optics with a special light distribution.
The figure below shows a lens for street lighting and its KSS.
DIY lighting masterpiece
The variety of lenses for LEDs and their wide availability make it possible to implement quite complex lighting solutions with your own hands. Lensed LEDs can give the most intricate shapes of CSS, some of them are presented in the figures below.
By combining different lenses in one lamp, you can achieve light distribution of almost any complexity.
Simple tasks are also solved more efficiently using secondary optics. So an LED flashlight, assembled with your own hands using a one-watt CREE LED, with one narrow-degree LEDIL lens will “pierce” the darkness for several hundred meters, while giving a clearly defined spot of light. While its purchased counterpart, comes from South-East Asia, with a bunch of small LEDs and a shiny reflector, will hardly “master” half of this distance.
The capabilities of secondary optics are impressive!
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