After more than two decades of doing home theatre consultation and calibration, initially as a hobby and then a career, it seems like projectors never truly gain a huge following. Even despite the fact that prices have dropped dramatically to merely a couple thousands of dollars, with performance that’s actually better than the predecessors that cost tens of thousands of dollars.
How it All Began
The first idea of projecting an image on a surface was envisioned in a drawing by Johannes de Fontana in 1420. It was a sketch of a monk holding a lantern. In the side of the lantern, there was a small translucent window that had an image of a devil holding a lance. The image, probably drawn on a thin sheet of bone, was projected onto a wall by the flame in the lantern. Without a lens, the image on the wall would have been very blurry.
But the idea provided inspiration to develop a projection model that would really work. Several people caught that inspiration, and any one of them could’ve been the actual inventor of the projector – it just depended who you asked and what country you were in.
Among the probable inventors, with the time and place of their invention, are Pierre Fournier (1515), Giovnni Battista della Porta (1589), Athansius Kircher (1646) – the list goes on and on.
Fast Forward to Home Theatre
In the early ‘50s and for the next 20 years, we used to use three-tube CRT projectors that weighed upwards of 200 lbs. and could only project images up to 40”. The image was dim, washed out, and the convergence between red, green and blue tubes were far from perfect. Calibration? Forget about it. Unless you were willing to redo the colour calibration and the convergence of red-green-blue alignment every six months, you could never get a decent picture (let alone near-perfect).
Yes, eventually the image got larger. But the price of projectors never really dropped. At least not until around the time when Blu-ray and HD-DVD were introduced to the general public in 2006. And even then, the price of a decent projector still fell in the $6,000 range at minimum.
Today, a projector of the same quality of one that cost $6,000 back in 2008 might sell for around $3,000, and is relatively easy to maintain. And those bulky CRT tubes have now been replaced by three main technologies (and their variants): DLP, LCoS, and LCD.
The following are explanations of each technology, and their pros and their cons.
At the heart of every DLP (Digital Light Processing) projection system is an optical semiconductor known as the DLP chip, which was invented by Dr. Larry Hornbeck of Texas Instruments in 1987.
The DLP chip is perhaps the world’s most sophisticated light switch. It contains a rectangular array of up to 8 million hinge-mounted microscopic mirrors. Each of these micro-mirrors measures less than one-fifth the width of a human hair. When a DLP chip is coordinated with a digital video or graphic signal, a light source, and a projection lens, its mirrors can reflect a digital image onto any surface. A DLP chip’s micro-mirrors tilt either toward the light source in a DLP projection system (ON) or away from it (OFF). This creates a light or dark pixel on the projection surface.
In this way, the mirrors in a DLP projection system can reflect pixels in up to 1,024 shades of gray to convert the video or graphic signal entering the DLP chip into a highly detailed grayscale image. The white light generated by the light source in a DLP projection display system passes through a colour wheel as it travels to the surface of the DLP chip. This filters the light into a minimum of red, green, and blue, from which a single-chip DLP projection system can create at least 16.7 million colours. As time goes by, the colour wheel of DLP technology evolved from three segments to six, seven and even more. Today, with BrilliantColor Technology, additional colours are added, including Cyan, Magenta and Yellow, to expand the colour palette for even more vibrant image reproduction.
Many DLP projection display systems also now offer solid-state illumination (usually 3-LED in R G B) which replaces the traditional Halide lamp. As a result, the light source emits the necessary colours eliminating the colour filter. Of course, for professional applications, a 3-chip architecture is used, particularly for high brightness projectors required for large venue applications such as concerts and movie theatres. These systems are capable of producing no fewer than 35 trillion colours.
- Scalable chip size results in the ability to produce tiny-sized projectors
- Amazing for 3D applications due to its potential of 10,000 Hz refresh rate
- Does not require convergence set up
- Rainbow effect that can be seen by around 5% of the population (with the exception of 3-chip DLP where each chip reflects each primary colour separately)
- Not-so-black black levels
- Relatively high noise due to the spinning of the colour wheel
An LCD projector is a modern equivalent of the slide projector or overhead projector. In order to display images, LCD (Liquid Crystal Display) projectors typically send light from a metal halide lamp through a prism or series of dichroic filters that separates light to three polysilicon panels – one each for the red, green and blue components of the video signal. As polarized light passes through the panels (combination of polarizer, LCD panel and analyzer), individual pixels can be opened to allow light to pass or closed to block the light. The combination of open and closed pixels can produce a wide range of colours and shades in the projected image.
Metal-halide lamps are used (also used in DLP and LCoS projectors) because they output an ideal colour temperature and a broad spectrum of colour. These lamps also have the ability to produce an extremely large amount of light within a small area; current projectors average about 2,000 to 15,000 American National Standards Institute (ANSI) lumens.
LCD technology started with RGB chips being sandwiched together onto a single panel. Although this was great for convergence, this type of projector could never be calibrated for colour accuracy since there was no way to control each colour individually.
The single chip was eventually replaced with what is now called “ 3-LCD “ technology, where separate R G B chips are used to achieve higher brightness, contrast ratio and colour accuracy.
In later years, Epson revamped 3-LCD technology even further to allow the ability for each panel to be calibrated to create perfect convergence, thus improving the apparent sharpness of the projected picture.
- More consistent colour reproduction out of the box
- Less motor noise due to the lack of a colour wheel
- Historically, the most tried and true technology for home use
- On some projectors, convergence is an issue (albeit very slight) that can not be fixed
- Colour uniformity across the screen is reserved for higher-priced LCDs
- Mediocre 3D presentation
LCoS & Its Variants
LCoS is where things got interesting. LCoS (Liquid Crystal on Silicon) is a reflective version of LCD. So instead of having light passing through the panel, similar to DLP Micro-mirror, LCoS and its variants reflects the light on to the panel.
At the 2004 CES, Intel announced plans for the large-scale production of inexpensive LCoS chips for use in flat panel displays. These plans were cancelled in October of that year. Instead, Sony made it to market in December 2005 with the VPL-VW100 or “Ruby” projector that used the SXRD trademark (Silicon X-tal Reflective Display) 3 LCoS chips, each with a native resolution of 1,920 × 1,080, and with a stated a contrast ratio of 15,000:1 using a dynamic iris.
Sony’s design maintains a uniform, ultra-thin liquid crystal cell gap without any spacers in the image area. With such a small gap, SXRD technology produces superb contrast. Sony also uses a Vertically Aligned Nematic (VAN) liquid crystal that changes state with amazing speed. This enables Sony’s SXRD microdisplay to run as fast as 200 frames per second while minimizing image smear.
The variant of LCoS technology is JVC D-ILA (Digital Direct Drive Image Light Amplifier) which was actually first released back in 1997, a decade earlier than Sony’s SXRD. Understandably (and expectedly, of course) since JVC commercialized its version of LCoS a decade earlier than Sony, there are some advantages of D-ILA over SXRD.
First, there’s very little space between D-ILA pixels (although SXRD is no slouch either), which results in an exceptionally smooth, “film-like” image. DLP includes moving parts, and space is needed between pixels for these moving parts. LCD requires that a transistor be mounted on each pixel and wires run between pixels. This, too, forces pixels to be spaced farther apart compared to D-ILA (and SXRD) devices. In both of these cases, the moving parts, transistors and wires limit the total area through which light can pass, which limits brightness. It can also create what’s known as the “screen door effect” – a “shadowing” on the image caused by the spaces between pixels. Look closely, and it’s as if you’re looking at the image through a screen door.
Second, the D-ILA device structure helps deliver very high native contrast. This is, in part, a consequence of the vertical alignment of the liquid crystal layers. Most recently, JVC’s D-ILA performance has been further improved by using new technology to make the surface more even, and pixel spacing has been further reduced. The result is unprecedented contrast, delivering deep blacks, bright whites and subtle gradations.
Yet another variant of LCoS was just recently introduced by Epson at CEDIA this past September. It was developed by and licensed from NHK, and is called LCoQ – Liquid Crystal of Quartz. Essentially it’s the same as LCoS but for the use of quartz instead of silicon. The potential for even better image clarity and colour reproduction is promising.
In the beginning, LCoS was utilizing similar technology to DLP – a colour wheel. As time progressed, the colour wheel has been dropped in favour of 3-chip LCoS, with each chip that deals with a single primary colour. Unlike with DLP, there hasn’t been a single company that still utilizes a colour wheel for the past decade.
- Nearly no screen-door effect
- Amazing black level
- Convergence of red, green and blue pixels can easily be perfected
- More expensive to manufacture
- Cannot be miniaturized, resulting in larger bodied projectors
- Just like LCD, not so great for 3D presentation due to the much slower refresh rate of the panels (maximum potential of 480 Hz)
The Future of Projectors
What about the future?
According to authorities on display technologies, Tomlinson Holman of the famed THX (and now working as a consultant for Apple) and Joel Silver of Imaging Science Foundation, the transmissive version of any technologies (such as single-chip DLP with colour-wheel and LCD) will be relegated to entry-level projectors due to their inability to produce deep blacks.
“As consumers are being more sophisticated and knowledgeable about the importance of video quality especially in black levels, transmissive projection technology will eventually go by the wayside,” says Tomlinson.
Adds Silver: “With the long life and colour temperature consistency within their respective life expectancy, LED and laser projectors are the future in projector technology.”
Only technologies using a reflective approach, such as 3-chip DLP and LCoS (and its variants, including LCoQ, D-ILA, SXRD), will survive in the long run thanks to their excellent abilities in creating native contrast ratio from the deepest blacks to the whitest white.
Beyond that, the regular bulb will eventually be replaced with either LED for screen sizes of 120” or smaller, or laser, like the Epson LS-10000 that was demonstrated at CEDIA 2014, for high brightness requirements such as 3D presentations and/or screen sizes larger than 120”. By using either LED and/or laser, the life of a bulb before reaching 60% brightness increased from a mere 1,000 hours (each projector varies, of course) to an estimated 10,000-15,000 hours!
Also due to the improvements in native contrast ratio, dynamic iris will eventually only be used in sub-$1,000 projectors. This way, there will be no iris-motor noise and iris opening lag (which creates a brightness pumping effect that can be distracting to some).
And I feel the technology will not stop there. Ultra High Definition video standards will play a huge role in the near future. We no longer have to endure the archaic BT-709 colour gamut, 8-bit video with 4:2:0 colour compression, 16-235 RGB range and 24 frames-per-second files. The Society of Motion Picture and Television Engineers (SMPTE) and Blu-ray Disc Association (BDA) have worked together to establish a vastly improved standard for UHD, which includes a minimum of 10-bit video with 4:4:4 colour compression, a wider 1-256 RGB range and up to 60 frames-per-second with an expanded colour gamut up to REC-2020. That’s essentially the full colour gamut a person can see.
Take for example, the Sony VPL-HW300ES 4K projector and the Epson LS10000 laser projector, both of which sell in the $8,000 range. These projectors are able to receive the full spectrum of the UHD standard natively, and upscale not only the input resolution but also the colour gamut, RGB range and colour bit depth to 12-bit (that’s trillions of colours!) These projectors also no longer use a mechanical iris to produce high dynamic range video.
They are not only amazing in theory, but from what I witnessed at CEDIA 2014, these two products are the beginning of the future of projectors. Beyond the super bright, long lamp life, full UHD compliance (and yes, both include HDCP 2.2 copy protection), and no mechanical iris, the post calibration colour rendition and greyscale accuracy are top notch. Just three years ago, that type of quality was relegated to projectors at three to four times the price. It’s clear the sky is the limit, and the future is bright.