Table of Content
One is to take the plans to an optical design firm and have them custom grind the lenses for you. The other is to make the lenses yourself by hand and then have them coated somewhere with the AR coating. I was hoping that someone out there had better access and funds to try to have one made. In the future I may try and redesign the lens for use with plastic lenses that can be hand made more easily but there is no reason that the lenses could not be made by hand. I may try and come up with a method that is doable in the future.
The way I figure it the average dot size for a high resolution CRT monitor is around .24 mm. This dot consists of three color pixels so lets say that for a lens system to accurately focus on these small objects it must be able to focus each subpixel. So we need a lens that can focus a spot size of .08 mm to be able to accurately focus the image.
Loupe 10x Oval Hasting Triplet 18mm Black Quality Metallic, Focal 1" Clarity
Since you are stuck with that distance, you have to work backwards to see how you can get the arc image focussed right at the projection lens. You can move the field fresnel to before or after the LCD. You can also play with the lamp-to-condensor-fresnel distance a bit to move the focal point of the field fresnel.
(Lenses designed with this have a 30 degree field of view.) I usually just use the chart at the bottom of the page. I know that a 1000 mm + 1000 mm duplet works very well with a 15" LCD. The field angle is about 32 degrees. With a shorter focal length and a 15" LCD, the field angle increases so it may not work as well. If you use a smaller LCD, then the field angle may decrease. You could try making one with off-the-shelf CR-39 plastic lenses to see if it works for your projector.
Designing a Cooke Triplet
Is the common generic design of triplet lens, like Rodenstock's Geronar, among others. I'm personally tempted to try a long focus Crown and flint achromat as my next project, I've seen a book on the subject and figure if I read it enough times I might just stand a chance! First off, I am in the process of making my own projector and trying to figure out what projection lens to use has brought me to this thread. So what this comes down to is that we need a lens system that can accurately focus an image as small as .08 mm or 80 microns.
The good thing about building a small refractor telescope is that they’re light and portable, making them idea for taking to dark-sky sites. We create a merit function using the Zemax Optimization Wizard with attempts to minimize the root-mean-squared spot size radius calculated from the centroid, with 3 rings and 6 arms. We also insert an optimization operand, EFFL, to control the effective focal length of 50 mm. The 2D Layout shown below shows significant coma aberration in the caustic of the off-axis fields.
Is it possible to build a triplet apochromatic refractor?
When a lens designer starts a design, he has a set of goals. Telescope objective designers don't care how their lens performs with light entering at a 20 degree angle, because it will be mounted in a long tube with a tiny eyepiece at the other end. Rays coming in at more than 1 degree will never make it to the eyepiece. A particular telescope objective might work okay with a 20 degree off-axis ray, but it might not. The mechanics involved in making lenses is often more challenging than the optics. One possibility is to go for a reusable, interchangeable-parts approach.
The lens cell on triplets is a vital element and quite complex to design and machine. So what your saying is lens with focal lengths of that distance always have a narrow feild of focus? You say that you dont know of a fresnal that will match that lens. Does the fresnel focal length need to be similiar to the focal length of the lens?
HTS 203A0 10x 21mm Chrome Triplet Jeweler's Loupe with Leather Case
This cancellation is not perfect either, so, Cooke Triplets are usually restricted to applications requiring only moderate speed and field coverage . My last camera was build with 2 box of cardboard and only one meniscus lens and seem like work so fine but this project i can't move the body for focus. For remedy this problem i'd like to project a lens like Cooke Triplet or other simple schema to focus more easy and adapt this lens to different kind of body that i'll build.
While spherical aberration dominates the on-axis field. Mark, you have exhumed an ancient thread, so I don't know if you'll get many answers. I have never tried to use an ordinary triplet lens as a macro lens, but here is some speculation. The Cooke Triplet was the basis of all of the high speed lenses used in 35mm photography.
I have compared it to a four element optimized glass tessar lens and the tessar is slightly better giving a 32 micron spot for the paraxial axis. For most application the slight improvement of the tessar over the cooke triplet does not justify the cost and added complexity. For us it shouldn't matter too much as the cooke has twice the on-axis resolution that we need. When a lens is used to focus parallel rays of light, the focal length is the distance from the lens to the point of focus. This means that for a single element camera lens, the focal length determines the distance the lens needs to be from the film or sensor.
This article will explore some of the top triplet lenses out there. This comes after going through numerous customer reviews, product reviews, and research into the specifications of the products. At the end of this review, you should be able to make an educated buying decision for one or multiple triplet lenses. Some of the glass required is pretty expensive and then there are 6 optical surfaces to grind, polish and multi-coat. The 3 lens elements need to be very carefully matched, spaced and mounted.
A small home made kiln will be made that can heat small glass blanks up to a moldable temperature. With e-drawing you can manipulate the model in real 3D space but you can not edit it. You can however, mark up notes and questions on the model and perhaps save the screen as a jpeg.
Rays of light from distant objects like the Moon pass through this and are bent or ‘refracted’ towards a point just inside the far end of the tube. Building your own telescope from simple components will help you understand how telescopes work. Our telescope design also makes a good science project for kids and young astronomers to complete at school or at home.
This is the focal length of the lens, or close to it. Ideally, the light source should be an infinite distance away, but I find that a light across the room gives me a pretty good approximation. The #1 model won this place with its consistent performance, ease of use, and quality build. At this stage it’s a good idea to make a temporary stand for your eyepiece and replace the card with it to confirm that the optical arrangement works effectively. You may even have a pair of broken binoculars with one salvageable objective lens. Thankfully, lenses are relatively easy to come by and can be surprisingly cheap at around £20 for a 60mm lens.
There are so many variables that triplet design was really an art form until computers became available. Early designers had to spend weeks doing the math to model how the lens would perform, changing each parameter a tiny bit each time through the calculations to see if it helped or hurt. Another approach is to use two tubes with slightly different diameters to build a sliding focuser. Cardboard mailing tubes or PVC pipes are possible sources for the sliding tubes. Sticky-back felt, from your local arts and crafts store, can be used to create a nice friction fit between the two tubes.
No comments:
Post a Comment