The dreaded Global Financial Crisis has struck again. My original plans for manufacturing this lens on a reasonably industrial scale have exhausted my potential investors, who were among the most influential in the market. Sadly, their funds did not match their enthusiasm. They prefer to buy (and continue to sell) ready-made European lenses at three times the price of the Horizon.
Lately, people whose opinions I respect have suggested custom-making a small run of these lenses for the discerning buyer. Each lens would be hand-crafted and assembled. I'm inclined to try it out, but in these tough times I realise discretionary spending, especially on high-end optics, is drying up.
The price I would have to sell these lenses for (to make a profit and cover the costs of a sufficiently large order for the glass) is about A$6,500. Considering that in Australia imported lenses are getting to around $12,000-plus, for what I'm told is lesser image quality, I believe this is a reasonable price in the current circumstances.
For Australian buyers, my production costs have increased by 50%, as the Australian dollar has dropped by approximately one-third... but this price increase is at the wholesale level. Imported anamorphic lenses to Australia have increased in price by 50%... at the retail level! Absorbing increased costs at the wholesale level is called "import substitution"... if you're buying from Australia you get a good deal.
For potential U buyers, A$6,500 in US dollars is about US$4,300 at current exchange rates, for the lens alone. Add in some freight and throw in a basic a slider and you're getting a superior performance optical device for about US$5,500 complete. That's another way of looking at the equation.
In any case, if you want to contact me and either encourage me to go ahead, or tell me my price is far too high (or that I'm mad!), please do so.
Email your criticisms/encouragement to me at cashcam[insert the "at" sign here]ozemail.com.au .
I'd be interested to hear the opinion of Constant Height HT aficianados out there.
P.S. sorry to take so long to update this blog, but I've been working on another project (survival!) for the past four months and have had to shelve the Horizon temporarily due to the original investors dropping out. Now that things are on more of an even keel, I feel I can think about making these lenses again... if there's a market for them.
Monday, February 9, 2009
Saturday, July 12, 2008
Why use a cylindrical lens?
When anamorphic prism lenses can be so cheap (down to a few hundred US dollars), why should a HT user purchase a more expensive cylindrical lens?
The basic problem with simple prism systems is that it is impossible to achieve simultaneous horizontal and vertical focus of the image at any one place on the screen.
The first illustration below says it all.
Shown are three computer modelled versions of a 16-pixel (4 x 4, black/white) checkerboard test pattern projected through a set of non color-corrected prisms.
To emphasize the aberrations seen, the test pattern is placed slightly towards one side of the final on-screen image. In the exact center of the screen the color aberrations shown would be minimized, and at the far edges the aberrations are so bad you might think I'm exaggerating them! So a compromise position was selected.
Each set of 4 x 4 pixels represents an on-screen area of 5.4 x 7.2 millimetres (about 1/5th x 1/3rd of an inch). The image is 1920 x 1080 pixels, projected onto a 3500mm wide (150") anamorphically stretched screen. Thus, the sets of 16 pixels shown are about 0.00075% of the full screen area.
Note: a basic prism lens cannot be focused. All focusing must be performed va the projector's focus mechanism.
Image #1
shows the projector focused to achieve the sharpest side edges of the pixels (best horizontal focus). However, the top and bottom edges of pixels are extremely blurred. Note also: because the prisms are not color-corrected, the three colors - Red, Blue and Green - are laterally displaced from each other at this point
Image #3
shows the converse situtation. This time the projector's focus has been changed to sharpen the top and bottom edges of the pixels (best vertical focus). However, the penalty for fixing the these has been to now blur the side edges. Color aberration is unchanged, as it is not primarily dependent upon focus of the system.
Image #2
shows the projector focused a third time. On this occasion, a "compromise" focus has been reached. Neither vertical nor horizontal focus is ideal, but at least some outline of the pixels can be seen. If you stand back a little from your monitor and squint you can make out a slightly soft, but discernable checkerboard pattern. Some of the color aberration also disappears... but only if you continue squinting!
What must also be remembered is that even this compromise focus can only be achieved over a limited area of the screen. At the pixel level, if the centre is compromise-focused vertically, then the sides will be blurred, and vice versa.
Contrast with cylindrical lens
The illustration below depicts a computer simulation of the Horizon lens's focus and color performance at the same point on the screen.
Note that both vertical and horizontal focus coincide. This has been brought about by first focusing the projector (without the Horizon lens in the projection beam) to achieve best focus across the screen.
Now, simply interposing the Horizon into the beam may not be enough to maintain vertical focus (see Image #3 above). But this is where the Horizon's adaptability comes into play: the Horizon has its own focus mechanism. This focus mechanism only affects horizontal focus. It has no (or extremely little) effect on the projector's focus in the vertical direction.
As the Horizon's focus mechanism is adjusted, vertical focus (via the projector) remains unchanged, but horizontal focus is improved until it matches the projector's focus. Now both horizontal and vertical focus is excellent.
This relationship is based only on the throw distance. The Horizon, once focused, is focus-synchronized with the projector. Focus will be maintained through all zoom settings of the the projector, as long as the throw is not changed (changing throw is usually a rare event anyway).
If the projector goes out of focus when the zoom is changed, all that will be needed will be a readjustment of the projector's focus only. The Horizon's focus will still be synchronized with the projector.
Another aspect of the Horizon's design is that, during the focusing procedure, image size will not change appreciably. Because the Horizon uses weakly refracting internal elements to focus (not the main anamorphosing elements) the aspect ratio and basic image size will remain the same throughtout the focusing procedure.
Color performance has also improved. There is some very slight color aberration, but it is much less than a quarter of a pixel in width. In resolution terms, this slight color aberration is more than four times finer than the resolution at which any image will be viewed by the audience. It will thus be invisible at all except microscopic levels of observation (for example, from about six inches from the screen) and then it will be difficult to pick out amongst the projector's native aberrations and distortions.
Color-Corrected Prism Systems
Color correction is achieved by using two types of glass for each prism element, with each prism element thus being made up of two prisms cemented together.
Many HT buffs believe that color-correcting prism system eliminates both color-aberration and astigmatism. This is untrue. Color-corrected prisms still exhibit roughly the same level of astigmatism as non color-corrected prisms.
This is illustrated by removing the color aberration from Image #3 above and presenting it as Image #4 below.
Note that the color aberration has been fixed but, because color aberration and astigmatism are unrelated, the modelled prism system in Image #4 still exhibits the differential focus problems discussed above in relation to Images #1, #2 and #3.
Color-corrected, compensated prism system
To fully correct a prism system for both astigmatism and color-aberration, a cylindrical element must be added either before or after the prisms to bring the entire screen area into focus, while maintaining good color-correction performance. In effect, this type of lens is a combination prism-cylindrical system (although the extra astigmatism correction element is only a very weak powered cylindrical lens).
However, due to the extra weight involved in using prisms (especially including heavy, color-correcting flint glasses), and the extra size required to maintain throw ratio performance, any such prism system will be quite heavy compared to a basically equivalent cylindrical system.
Above is a size comparison of the Horizon and an equivalent color and astigmatism corrected prism system that I designed for the purposes of seeing which was bigger and by how much. The prism system is approximately the same height, but nearly twice as long as the Horizon. It weighs 2.5 times as much (9.5 pounds v. 3.8 pounds).
In Conclusion
The discussion above does not claim that any cylindrical system must perform as well or better than any prism system. Design and manufacturing tolerances still need to be maintained to produce an excellent cylindrical system that clearly outperforms a prism system.
However, this much is true: the design flexibility afforded by using the complex curved surfaces of a cylindrical system, will always present better potential for astigmatism, distortion and color correction than can possibly be afforded with a prism system. This is due simly to the greater freedom of design and curvature options that a cylindrical system affords.
The basic problem with simple prism systems is that it is impossible to achieve simultaneous horizontal and vertical focus of the image at any one place on the screen.
The first illustration below says it all.
Shown are three computer modelled versions of a 16-pixel (4 x 4, black/white) checkerboard test pattern projected through a set of non color-corrected prisms.
To emphasize the aberrations seen, the test pattern is placed slightly towards one side of the final on-screen image. In the exact center of the screen the color aberrations shown would be minimized, and at the far edges the aberrations are so bad you might think I'm exaggerating them! So a compromise position was selected.
Each set of 4 x 4 pixels represents an on-screen area of 5.4 x 7.2 millimetres (about 1/5th x 1/3rd of an inch). The image is 1920 x 1080 pixels, projected onto a 3500mm wide (150") anamorphically stretched screen. Thus, the sets of 16 pixels shown are about 0.00075% of the full screen area.
Note: a basic prism lens cannot be focused. All focusing must be performed va the projector's focus mechanism.
Image #1
shows the projector focused to achieve the sharpest side edges of the pixels (best horizontal focus). However, the top and bottom edges of pixels are extremely blurred. Note also: because the prisms are not color-corrected, the three colors - Red, Blue and Green - are laterally displaced from each other at this point
Image #3
shows the converse situtation. This time the projector's focus has been changed to sharpen the top and bottom edges of the pixels (best vertical focus). However, the penalty for fixing the these has been to now blur the side edges. Color aberration is unchanged, as it is not primarily dependent upon focus of the system.
Image #2
shows the projector focused a third time. On this occasion, a "compromise" focus has been reached. Neither vertical nor horizontal focus is ideal, but at least some outline of the pixels can be seen. If you stand back a little from your monitor and squint you can make out a slightly soft, but discernable checkerboard pattern. Some of the color aberration also disappears... but only if you continue squinting!
What must also be remembered is that even this compromise focus can only be achieved over a limited area of the screen. At the pixel level, if the centre is compromise-focused vertically, then the sides will be blurred, and vice versa.
Contrast with cylindrical lens
The illustration below depicts a computer simulation of the Horizon lens's focus and color performance at the same point on the screen.
Note that both vertical and horizontal focus coincide. This has been brought about by first focusing the projector (without the Horizon lens in the projection beam) to achieve best focus across the screen.
Now, simply interposing the Horizon into the beam may not be enough to maintain vertical focus (see Image #3 above). But this is where the Horizon's adaptability comes into play: the Horizon has its own focus mechanism. This focus mechanism only affects horizontal focus. It has no (or extremely little) effect on the projector's focus in the vertical direction.
As the Horizon's focus mechanism is adjusted, vertical focus (via the projector) remains unchanged, but horizontal focus is improved until it matches the projector's focus. Now both horizontal and vertical focus is excellent.
This relationship is based only on the throw distance. The Horizon, once focused, is focus-synchronized with the projector. Focus will be maintained through all zoom settings of the the projector, as long as the throw is not changed (changing throw is usually a rare event anyway).
If the projector goes out of focus when the zoom is changed, all that will be needed will be a readjustment of the projector's focus only. The Horizon's focus will still be synchronized with the projector.
Another aspect of the Horizon's design is that, during the focusing procedure, image size will not change appreciably. Because the Horizon uses weakly refracting internal elements to focus (not the main anamorphosing elements) the aspect ratio and basic image size will remain the same throughtout the focusing procedure.
Color performance has also improved. There is some very slight color aberration, but it is much less than a quarter of a pixel in width. In resolution terms, this slight color aberration is more than four times finer than the resolution at which any image will be viewed by the audience. It will thus be invisible at all except microscopic levels of observation (for example, from about six inches from the screen) and then it will be difficult to pick out amongst the projector's native aberrations and distortions.
Color-Corrected Prism Systems
Color correction is achieved by using two types of glass for each prism element, with each prism element thus being made up of two prisms cemented together.
Many HT buffs believe that color-correcting prism system eliminates both color-aberration and astigmatism. This is untrue. Color-corrected prisms still exhibit roughly the same level of astigmatism as non color-corrected prisms.
This is illustrated by removing the color aberration from Image #3 above and presenting it as Image #4 below.
Note that the color aberration has been fixed but, because color aberration and astigmatism are unrelated, the modelled prism system in Image #4 still exhibits the differential focus problems discussed above in relation to Images #1, #2 and #3.
Color-corrected, compensated prism system
To fully correct a prism system for both astigmatism and color-aberration, a cylindrical element must be added either before or after the prisms to bring the entire screen area into focus, while maintaining good color-correction performance. In effect, this type of lens is a combination prism-cylindrical system (although the extra astigmatism correction element is only a very weak powered cylindrical lens).
However, due to the extra weight involved in using prisms (especially including heavy, color-correcting flint glasses), and the extra size required to maintain throw ratio performance, any such prism system will be quite heavy compared to a basically equivalent cylindrical system.
Above is a size comparison of the Horizon and an equivalent color and astigmatism corrected prism system that I designed for the purposes of seeing which was bigger and by how much. The prism system is approximately the same height, but nearly twice as long as the Horizon. It weighs 2.5 times as much (9.5 pounds v. 3.8 pounds).
In Conclusion
The discussion above does not claim that any cylindrical system must perform as well or better than any prism system. Design and manufacturing tolerances still need to be maintained to produce an excellent cylindrical system that clearly outperforms a prism system.
However, this much is true: the design flexibility afforded by using the complex curved surfaces of a cylindrical system, will always present better potential for astigmatism, distortion and color correction than can possibly be afforded with a prism system. This is due simly to the greater freedom of design and curvature options that a cylindrical system affords.
Tuesday, June 24, 2008
The Approaching Horizon
This blog is intended to be a meeting place for HT projection enthusiasts interested in my new cylindrical lens design for Constant Image Height (CIH) applications.
If you don't know what "CIH" means and how it works then you probably need to visit one or more of the several excellent net forums that deal with this area of HT projection. You could try the AV Science Forum which has extensive information on CIH, Mark Techer's excellent CIH-based Australian site, or perhaps the DTV Forum from Australia which covers CIH issues from time to time.
The "working title" of my lens design is "Horizon". Since early 2007, I have been testing and evaluating the prototype Horizon with a variety of HT and cinema projectors, screens and optical systems to make sure it performs as well as modelled by my Zemax optical design software, the world standard for advanced optical design.
The aim of the design is to produce an optically advanced 1.33x horizontal expansion anamorphic lens that is bright, focusable, has low astigmatism, low grid distortion, maintains its 2.37:1 image geometry over a sizeable range of throw ratios and is compatible with 1920 x 1080 HT projectors, all in a moderately-priced, easy to use package.
In many ways, the optical design is the easy part. When you're doing your computer modelling, you don't have to worry about dust, or faulty glass, or trying to get engineers (who'd rather be making door knobs) to turn out your precise mechanics sometime within the next year. You don't need to worry about unreal price expectations of users, kibbitzers who only want to criticise, or potential customers who know far too little about far too much and take every opportunity to tell you about it. Most of all you don't have to worry about the money, as in "lots of it", which is necessary to go into production so that your product can be appreciated, as much for its external appearance as its critical function.
But first, a couple of things that always get asked about any new product.
When?
If there is sufficient serious demand, I am hoping to produce an initial "advanced prototype" run of from 25 to 50 units before the end of 2008. These will be most likely sold direct off the net to keep marketing and distribution costs down, and to enable me to have direct feedback from customers on the performance and quality of the design .
Price
I know I said "moderate" but I haven't decided on a firm price yet. Suffice it say that I intend the Horizon to be very competitive in the market. By this I don't mean just $10 short of the price of some of the European cylindrical anamorphics available today. I mean a lot less expensive.
On the other hand, I can't give the Horizon away and there are no shortcuts in quality optics. The initial product will probably be a little less expensive than subsequent production runs in order to get it out there in the marketplace and to garner some feedback. So please keep these thoughts in mind.
Quality
When I use the term "advanced prototype" I don't mean something held together with chewing gum and Durex tape. But, until full production jigs and tooling are fully on line, I'm going to have to put these lenses together one-by-one in a sort of "mass customization" manufacturing process.
However, there will be no compromise on the optics. I believe performance is already optically first-class. Optical quality will not be sacrificed to pressure of cost. Berlow are some screen shots of a recent test, using test patterns of my own design (click to enlarge to 100%).
The features to notice in this series of screen shots are the clear separation between pixels and lines. "Fundamental Frequency" demonstrates alternating single pixel lines or dots: black-white-black-white etc. "Fundamental" indicates the finest resoution available in the display device, in this case a Sony 1920 x 1080 pixel full High Definition projector. In these shots, the fundamental frequency is clearly displayed with very good separation between pixels.
Design Outline
The design uses four lenses - two singlets and two doublets - in two groups: and anamorphic group and a focusing group. As a result of the functional separation between the two groups, image size will not change as focusing proceeds. You'll set your zoom, focus your projector and then focus the Horizon... all without any change in image geometry. Remove the Horizon from the light path and your 16:9 image will be exactly the same height, and still as perfectly focused as your anamorphic image was. That is what genuine "Constant Image Height" performance is all about.
Any other questions... please ask them. I don't guarantee to give answers to all of them (for example, I'm not publishing the curvatures of the individual lenses or similar cinfidential details, and I'll be trying to avoid directly comparing my lens with any other similar product... let others do that), but I'll try my best to be frank and upfront as this project continues.
The design uses four lenses - two singlets and two doublets - in two groups: and anamorphic group and a focusing group. As a result of the functional separation between the two groups, image size will not change as focusing proceeds. You'll set your zoom, focus your projector and then focus the Horizon... all without any change in image geometry. Remove the Horizon from the light path and your 16:9 image will be exactly the same height, and still as perfectly focused as your anamorphic image was. That is what genuine "Constant Image Height" performance is all about.
Any other questions... please ask them. I don't guarantee to give answers to all of them (for example, I'm not publishing the curvatures of the individual lenses or similar cinfidential details, and I'll be trying to avoid directly comparing my lens with any other similar product... let others do that), but I'll try my best to be frank and upfront as this project continues.
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