#directdriveimagelightamplifier

The development of digital technology has provoked a rapid development in the consumer electronics segment. Over the past 10 years, innovation unrecognizably transformed many familiar household devices. Today the market offers robotic vacuums with cleaning schedules, efficient navigation and even the Automatic Dirt Disposal option, coffee machines with automatic preparation of a huge number of different coffee drinks, modular Samsung MicroLED TVs with the ability to change screen size, etc.

Introduction

Of course, projectors occupy a worthy place on this list. Until recently, many considered them only as an element of a home theater. But the development of semiconductor technologies has expanded the capabilities of engineers, allowing them to design mini, pico, pocket projectors with a laser or LED light source. Today the market already offers smartphones with a built-in laser projector and Rif 6 Cube with unprecedented 0.30 lbs (136 g) and 2 x 2 x 1.9 in (5.1 x 5.1 x 4.8 cm), which can form a projection up to 50 inches.

Of course, the segment of full-size powerful Home Theater 4K HDR projectors also continues to actively develop. Their popularity is quite founded. The cost of TVs with a screen size of 75 inches and above remains very high, reaching several thousand dollars. At the same time, even a mid-budget projector with a price of up to $ 1,000 already provides 4K HDR quality on a screen with a diagonal of 100 inches or higher. Of course, companies sometimes indicate a maximum projection size of about 300 inches. But it’s even scary to think how much a projector should cost, which can provide acceptable image quality for such a screen. A range of 100 to 150 inches is more realistic for modern projectors. But even this size radically exceeds the capabilities of TVs, with the exception of modular Samsung MicroLED panels.

Therefore, in recent years, many consider the projector as an alternative to TV. This factor provides good demand and, accordingly, the rapid development of the projector segment.

Laser projectors

As known, the success of semiconductor manufacturers has provoked a new direction in the projector segment. Companies have actively begun to develop projectors with lasers and LEDs as light sources. After a few years, companies offered a huge amount of laser and LEDs projectors. The relatively low price, a huge resource of up to 20,000 hours, silent operation due to the lack of a cooling fan, and compactness ensured them great popularity. Of course, their classification is rather vague. Companies often call these models mini, piko, pocket, or portable projectors. But, of course, this aspect contains a marketing component. With the exception of really miniature models weighing a few lb, most of these projectors are more consistent with the term mini. Probably, many projectors can fit in a large coat pocket, but this is not enough for pocket classification. As a rule, laser models provide a sufficiently high brightness, high image quality, and are well suited for Home Theater. Unfortunately, they have a fairly high price, which can reach several thousand dollars. LEDs projectors are much cheaper, but their brightness usually varies up to several hundred lumens, and the image quality often does not match the level of the Home Theater.

Epson 3LCD technology

All modern projectors use DLP, 3LCD or LCoS imaging technology. Due to the high price, LCoS projectors have a small market share. Today, only JVC and Sony projectors use LCoS technology. JVC calls it D-ILA (Direct Drive Image Light Amplifier), Sony - SXRD (Silicon X-tal Reflective Display). Unfortunately, Sony VPL models cost from $ 2,000 and up.

DLP projectors are very popular due to their relatively low price and high quality. But they have some cons, including the rainbow effect, etc. Today DLP models from BenQ, Optoma, LG, ViewSonic, etc are competing fiercely in the Home Theater segment. But the leaders, for example, Optoma or ViewSonic, offer the entire range of DLP projectors. In addition, AAXA, Miroir, Asus Anker, etc also offer a huge range of laser and LED DLP mini projectors. The situation in the segment of 3LCD projectors is significantly different. As known, 3LCD technology was developed by Seiko Epson Corporation. In early 2012, Epson introduced its first 3LCD 3D home theater projectors. Today the market offers NEC, ViewSonic, Sony, etc 3LCD projectors. But Epson confidently dominates this segment. For example, the very popular Epson 4K HDR 5040 and 5050 series are included in many top lists with the best home theater models of 2019.

In fact, today the main competition is concentrated between Epson 3LCD projectors and DLP models. Traditionally, 3LCDs have a higher price, but provide higher quality. This factor is caused by the objective key features of this technology.

White Light Output (WLO) vs Color Light Output (CLO)

The vast majority of modern devices form color by mixing red, green and blue (RGB). Therefore, each pixel of an LCD monitor uses 3 subpixels. The principle of color formation works as follows: - the maximum brightness of three points provides white color; - the minimum brightness forms a black color; - the maximum brightness of the red and green subpixels gives yellow light, etc. The luminous flux of the projector is traditionally measured in white. Theoretically, the maximum brightness of the projector should be equal to the sum of the color brightness of red, green, and blue. But really, 3LCD and DLP technologies form the color image in different ways. 3LCD technology forms an image using three liquid crystal matrices. The projector divides the white color of the light source into red, green and blue using special filters. Then, each stream is modulated by a corresponding matrix. After that, the three components are combined again, forming a color image on the screen. Accordingly, this technology provides minimal brightness loss. But the 1-chip DLP system uses a color wheel, forming only one color component at a time.

At the same time, color filters block two other colors. Accordingly, color mixing and image formation is carried out already on the screen. Of course, the eye does not perceive the separation of colors over time due to the high frequency. But, this technology has high loss of color brightness due to filtering. As a result, 3LCD and DLP models provide different CLO even with the same WLO. The visualization of this difference is clearly seen in side-by-side comparisons.

Projector brightness

Of course, the brightness of the projector is one of its main specs. In particular, it directly affects the following factors: - color accuracy depends on the projector brightness; - technology for 3D reproducing requires increased brightness to compensate for its losses; - high brightness expands the possibilities of using economical modes of the light source and reduces the requirements for darkening the room to ensure high image contrast. As a result, this parameter has acquired important marketing value. Of course, Epson regularly draws the attention of consumers to this aspect, pointing out in the specs WLO and CLO, which are always the same. In turn, manufacturers of DLP projectors are trying to solve the problem of brightness loss. But today, the use of more expensive 3-chip DLP technology has proven to be the most effective.

Unfortunately, the price of 3-chip DLP models is commensurate with the cost of 3LCD projectors. Many companies use the addition of a white segment to the color wheel. But magnification of the white component worsens other colors, making them darker and faded.

Of course, increasing the power of the light source also effectively solves this problem. But it is effective only for laser or LED projectors, which practically do not heat up. But powerful lasers increase the model price. An increase in lamp power requires efficient cooling and an increase in internal volume for heat dissipation. Unfortunately, the use of a more powerful fan increases the noise level of the device, and an increase in internal volume increases its dimensions. Therefore, many DLP manufacturers prefer to specify only WLO without CLO.

Epson EF-100

Almost every year, Epson offers innovative models. 2020 was no exception. At CES 2020, the company introduced the portable 3LCD Epson EF-100 Smart Streaming Laser Projector with Android TV.

Model has the following main specs: - price about $ 900; - 2,000 lumens of white and color brightness; - 1280 x 800 WXGA native resolution with support up to 1080p (1920 x 1080); - 3-chip 3LCD design without rainbow effect; - innovative Epson MicroLaser Array Projection Technology, based on multi-array laser diode technology, increases the brightness while significantly enhancing the black density; - 9-element lens with seven glass elements; - internal speaker 5.0 W Mono; - 3.5mm stereo output; - Audible Noise 29.0 dB/26.0 dB (eco); - Throw Ratio of 1.06:1; - Digital Zoom and Horizontal & Vertical Digital Keystone; - remote with built-in Google Assistant voice search; - laser light source with service life of 12,000/20,000 (eco) hours; - Android TV wireless dongle included; - size and weight - 3.6 x 8.3 х 9.1 in (9 x 21 x 23 cm) and 6.0 lbs (2.7 kg). The rectangular shape allows the user to position the projector horizontally for projection onto a wall or vertically for projection onto a ceiling. The Android dongle supports popular streaming services, including Netflix, YouTube, Hulu, ESPN, etc. It also supports 4K and can be used with any device with a compatible HDMI connection.

Key features

The Epson EF-100 has become an excellent compromise between price, dimensions and specs. On the other hand, 3.6 x 8.3 x 9.1 in and 6.0 lbs are quite consistent with its classification as a portable model.

For comparison, dimensions and weight of the very popular in this class BenQ HT3550 and Optoma EH412 reach 5 x 15 x 10 in, 9.3 lbs and 4.3 x 12 x 9.5 in, 7.7 lbs, respectively. Moreover, a very successful design with right angles allows the user to install the projector in any position, including vertical for projection onto the ceiling. Digital Zoom and Horizontal & Vertical Digital Keystone further simplify this process. Finally, the internal 5.0W speaker completes the list of pros in terms of its mobility. Specs are also of a high standard. In particular, 2,000 lumens of white and color brightness and 1280 x 800 WXGA native resolution with support up to 1080p (1920 x 1080) are quite suitable for using the model as a Home Theater. In addition, the innovative Epson MicroLaser Array Projection Technology and the great 9-element lens with seven glass elements provide projection with a diagonal of up to 150 inches and WXGA resolution at Throw Distance 2.3 ft - 11.1 ft. For example, the projector projects a 100-inch diagonal image at a distance of 7.6 ft from the screen.

At the same time, high brightness does not require careful dimming of the room. Unfortunately, the model does not have a Lens Shift.

Conclusion

As known, the whole history of the consumer electronics development is accompanied by fierce competition. It forces companies to constantly increase competitiveness, expanding the functionality of their models and reducing its costs. Of course, the solution of this problem requires the active use of innovative technologies. As a result, companies are investing heavily in their development. As a consequence, today the market often offers similar in consumer qualities models using different technologies. LED LCD, OLED (LG), QLED(Samsung) and NanoCell (LG), Micro LED models in a TV segment perfectly illustrate this trend. High-tech projectors are no exception. Today, models with DLP, 3LCD, and LCoS (D-ILA, SXRD) projection technologies successfully compete in the market. In addition, the development of the segment with LEDs and laser LEDs as light sources initiated the rapid development of portable models of various form factors (pico, cubed, micro, pocket). Moreover, advances in precision technology for manufacturing aspherical lenses and reflective mirrors pushed the development of very popular Ultra Short Throw (UST) projectors, which are able to create huge high-quality projections at a distance of several tens of inches. LG PF1000UW perfectly demonstrates these possibilities. Of course, this situation provides a very rapid improvement of household appliances that pleases consumers. Unfortunately, this wonderful trend has a side effect. Today, the conscious choice of the optimal device requires some effort from the consumer. Of course, the price and functionality remain the main criteria. The price depends entirely on company policy and we cannot influence it. But assessing the price / quality ratio is sometimes a difficult task because of the abundance of offers, which often contain a marketing component. Therefore, even a simplified classification can partially simplify this task.

Operation principle

As known, DLP (Digital Light Processing) uses a semiconductor DMD (Digital Micromirror Device) chip from Texas Instrument with an array of micromirrors to reflect light. In fact, each micromirror corresponds to one pixel. The control signal tilts the micromirror at an angle of ± 12 °, forming a white or black dot on the screen. The frequency of control signals in modern models reaches several kHz. Today, the company produces a wide range of DMD, including, for example, DLP 2000 (0.20 "), DLP 2010 (0.21"), DLP 230GP (0.23"), DLP 230KP (0.23"), DLP 230NP ( 0.23"), DLP 3010 (0.31"), DLP 3310 (0.33") and DLP 4710 (0.47"). They support display resolution from 640 x 360 (nHD) to 1920 x 1080 (1080 p or Full HD). But DLP projectors form a color image on the screen, alternating a sequence of projections with different colors and creating the illusion of a color image due to the high frame rate. The color wheel with segments of different colors serves as a color filter. As known, 3LCD technology was developed by Epson. It uses the influence of electricity on the spatial orientation of liquid crystal molecules. In fact, its matrixes work in the same way as traditional LCD matrices in TVs. But unlike the DLP projector, the 3LCD models form a color image with the help of special prism from three mono-color images. The LCoS (Liquid Crystal on Silicon) projectors combine the best qualities of DLP and 3LCD technologies. Today, its versions of SXRD (Silicon X-tal Reflective Display) from Sony and D-ILA (Direct Drive Image Light Amplifier) from JVC are the most popular.

Contrast ratio

Of course, the image quality dependents on the contrast. As known, this value characterizes the ratio of the brightness of the brightest and darkest pixels. Specs of projectors or TVs contain it in the form of, for example, 60,000: 1. Accordingly, the contrast depends on the maximum brightness and depth of black. In fact, contrast provides depth and dimension of the image, which affect the realism of perception. Today DLP technology in the DLP and LCoS projectors provides higher contrast compared to LCD models. The use of reflection allows engineers to achieve very deep black due to the complete cut-off of light. LCD matrixes use the light pass and cannot ensure its complete blocking. But on the other hand, powerful lamp 3LCD projectors partially compensate for this factor with higher brightness. Many models use effective Auto Iris technology, which adjusts the aperture depending on the illumination of the scene in the frame.

Brightness and color

The brightness characterizes the light intensity in ANSI lm or lm. It has several names, including the light output or lumens rating. This value mainly depends on the type of the light source in the projector. Today, lamps and lasers provide maximum brightness. But the lamps are quite expensive and have a limited service life (4,000-6,000 hours). Laser LEDs provide high power and long service life, but are expensive (mainly due to expensive green lasers). LEDs have a very long service life (20,000-30,000 hours) and are relatively inexpensive, but do not provide sufficient brightness. In turn, brightness affects viewing comfort. Low brightness requires dimming the room to produce acceptable image quality. High brightness provides it even in daylight. Unfortunately, powerful lamps get very hot during operation and require efficient cooling. In turn, the noise during the operation of powerful fan reduces the viewing comfort. Therefore, the choice of brightness represents a trade-off between durability, dimming requirements and noise level. The type of light source mainly depends on the positioning model (portable, home theater, etc) and does not depend on technology. But in general, the 3LCD models often use lamps, and DLP and LCoS - semiconductor light sources (LEDs or laser LEDs). Color accuracy, color range and saturation depend only on the model class.

Motion Blur and Input Lag

As known, this effect is visualized in highly dynamic scenes. Companies solve this problem by increasing the frequency or using the interpolation method that TV manufacturers have been using for years. This technology is based on the formation of intermediate frames by the processor. Today, almost all leading companies use this technology and own indexes for TVs, including Motion Clarity Index (MCI), Clear motion rate (CMR), Picture Quality Index (PQI), Perfect Motion Rate (PMR), Motionflow XR, etc. Unfortunately, increasing the processor load significantly increases Input Lag. Therefore, some projectors automatically disable it in game mode. As known, Input Lag is especially important in games. This value in many modern projectors does not exceed several tens of milliseconds. But some projectors provide an unprecedented low Input Lag, which allows them to be positioned as game models. For example, the Input Lag of UST ViewSonic PX800HD does not exceed 16 ms with 3X Fast Input option. With other things being equal, DLP projectors are confidently leading in this aspect compared to 3LCD and LCoS models.

Rainbow and Screen Door Effects, and Dust Resistance

Rainbow effect appears as multicolored points along the contour of contrasting objects in the frame. It's caused by using a color wheel and shown only in 1-chip DLP projectors. Increasing the speed of its rotation reduces the effect. However, today companies successfully solve this problem in various ways, including, for example, using the innovative RGBRGB color wheel. Of course, LCD and LCoS projectors do not have this effect due to the lack of a color wheel. Screen Door Effect is a visualization of pixels on the screen at a short distance. The high pixel fill factorI duu to the minimum distance between micro mirrors in the DMD chip almost completely eliminates this effect in DLP projectors. Unfortunately, 3LCD models, especially inexpensive, form an image with this effect due to the rather large distance between the matrix crystals. However, more expensive models successfully compensate for it by high resolution. LCoS projectors form an image without this effect. Of course, dust significantly reduces the quality of optics, which is one of the main components of any projector. From this point of view, DLP projectors have a great advantage, because DMD chips are superbly sealed. 3LCD and LCoS models use sealed or non-sealed chips. More expensive models have additional protection.

Conclusion

The rapid development of innovations based on digital technology is the main trend for all segments of consumer electronics. Of course, high-tech projectors are no exception. For several decades, the projector has become a complex digital device with huge media capabilities. The projector in the smartphone, miniature Pico and Cube projectors with semiconductor light sources (LEDs or laser LEDs) perfectly illustrate this trend. As known, modern models form a projection image using DLP, 3LCD or LCoS technology. DLP and LCoS technologies use reflected light, while LCD works on the light pass. Of course, each of them has its pros and cons, but they all have been successfully competing in the market for many years.

LCoS (Liquid Crystal on Silicon) operation principle

LCoS can be positioned as a hybrid of 3LCD and DLP technologies. In fact, the LCoS matrix is an LCD matrix that is glued to the mirror. The control semiconductor layer on the substrate with a reflective surface is under the matrix with an array of liquid crystals, protective glass and a polarizer. The spatial orientation of the liquid crystal in the semiconductor layer depends on the control signal.

In fact, it adjusts the transparency of the cell, ensuring control of the light flux passing to the reflective layer and back.

Thus, the liquid crystal matrix modulates the luminous flux, using not the light pass, but its reflection. The light from the source is divided by a system of dichroic and simple mirrors into three light streams corresponding to red, green and blue. Further, each of them falls on its own Polarizing Beam Splitter (PBS) and on the reflecting matrix. The matrix modulates the light, forming the color components for each color channel. They pass back through the PBS and come together in a dichroic prism, forming a color image. The resulting picture is projected through the lens on the screen.

Today several companies use this principle of image formation, having patented their own developments. The list of the most popular includes SXRD (Silicon X-tal Reflective Display) from Sony, D-ILA (Direct Drive Image Light Amplifier) from JVC.

PROS & CONS

The developers of LCoS technology initially set themselves the task of combining the advantages of 3LCD and DLP technologies, of course, without their cons. LCoS projectors provide very high image quality, high brightness and contrast. Moreover, they support the projection with very large image format. In addition, the production technology of reflective matrices allows companies to place the control conductors and electronics behind the reflective layer, increasing the coverage area of the pixels. As a result, these models do not have a screen-door effect.