Are the new hybrid slimlines bringing fear to the competition?

LEDs are increasingly finding their ways into our lives. LEDs as car lights, LEDs in torches, LEDs for domestic lighting, etc. And even in consumer electronics, they are here to stay. These days, LEDs illuminate almost all modern LCD monitors and flat screen TVs.

A similar trend is expected in the large-screen projection area. From generation to generation, LEDs have been achieving higher light output, and the first high-end projectors equipped with three LEDs as a light source have been on the market for several months (and have been verified by us in comprehensive tests). In addition to very promising benefits (long life, pure colours, etc.), all of these projector pioneers have one thing in common: they all cost well over €10,000.

And so it was all the more surprising that Casio introduced a completely new lighting technology at the beginning of this year. The new models of the "XJ-A" series also have no UHP lamp. Instead, a hybrid technology using LEDs and laser provides the necessary light.



A tandem of blue laser and red LED produces the light. A special phosphor–coated colour wheel that modulates the blue laser light into green wavelengths takes care of the green component.

Those now thinking that this LED / laser combination also suffers from severely limited light output, like the "LED-only" devices, are mistaken. The new Casio super slims are said to be able to reach an astonishing 2500 lumens. Then combine these with a life span of approximately 20,000 hours, about 10 times as long as a conventional UHP lamp.

In light of new technology, development costs of the first generation and long life benefits, you would expect the price to be high, but far from it. The current selling price is about €1,000 for all models. Thus they are not only one of the most modern, but also one of the cheapest projectors on the market.

All this sounds too good to be true. Is it really an advanced breakthrough, or are there hidden limitations and shortcomings? The first devices went on sale recently and we have secured an XJ-A to get to the bottom of this new hybrid technology.

1. Equipment and Technology

We should mention one thing up front. Casio did not develop this first hybrid generation as optimised home cinema equipment, but as an ultra portable presentation projector. The chassis is also compact accordingly.



With only about 4cm in height, it is one of the flattest projectors available, and in particular when the high light output is taken into account. With its approximate A4 / notebook format, it fits into almost any briefcase.

The workmanship is also unusually top quality. The device is stable and does not convey the typical "plastic feeling" that most other devices do in this price range. Weighing 2.3 kg, it is anything but a lightweight.

Flexible installation options are particularly important for portable presentation devices. This demand is met with a 2-fold zoom lens which makes almost any projection distance possible despite its small size (diameter is the size of a €2 coin).


Small but powerful: the projection optics

The amount of luxury provided is amazing. Both zoom and focus are motorised and can be adjusted easily by remote control.

In contrast, the connections are anything but luxurious. The absolute minimum is provided. At least, the digital age was not forgotten, and the projector was given a modern HDMI connector.



All the common types of resolution from VGA to UXGA can be set, although the latter has drawbacks due to lack of native resolution. Casio hybrid projectors are currently shipped with a maximum WXGA resolution. So they are nevertheless "HD-ready", especially since they also understand all resolutions and video signal standards (NTSC, PAL, YUV). However, there is one painful exception. Our test device was unable to process 1080/24p, which makes a film projection with the original film frequency impossible. This is a knock-out criterion for many fans, but you can hardly blame this on the device because it is not after all a home cinema projector, but merely a presentation device.



Things are more exciting as far as the chassis is concerned because we got to the bottom of the technology. Although the manufacturer published a rough sketch of the functions prior to release (see above), needless to say we were not satisfied and preferred to get a personal impression of the technical structure by opening the device.

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But we made the first interesting observation on the rear side. There is a screw cap here, similar to a light shaft. When you open this, a kind of module is revealed.



Like a typical UHP lamp module, this can be easily be removed from the device by loosening a few screws. What comes to light is of course not a lamp but the laser module of the hybrid projector.


Not just one but a total of 24 lasers provide the blue light

And here we experienced our first major surprise. The blue laser light is not produced by a single diode, but by a whole battery: 24 of them. You can see the individual mini lenses fitted in front of each laser diode in the picture above. A look at the now empty slot shows the beginning of the light path.



Eight vertical mirrors at an angle of 45 degrees directed toward the laser module reflect the light of a respective pair of diodes “around the corner" in the common light channel. The design with an exchangeable laser module from the outside raises questions. Does the manufacturer assume that the laser light source will not work completely maintenance-free for the next 20,000 hours? Should early changes be made easier for the sake of service? Why is there no corresponding change tray for the red LED?

We continued with our investigations and removed the cover of the projector. The interior shows a typical structure with upper signal board.



The sophisticated projection optics are in the long metal tube on the top left. To facilitate a large zoom range, it was not built in sideways, but lengthwise. In the middle (to the right of the signal board), we see the laser module described above. The power supply with corresponding switching electronics is on the right in the housing.



We removed the signal electronics where there are no special components or chips. The equipment is typical DMD control chips from Texas Instruments.



We finally reach our goal under the board. Here, the entire light path is revealed. The open part for light bundling is noticeable before the closed DLP-typical part of the light path begins.



So how does the lighting system consisting of laser + LED + a phosphorous wheel work? The implementation is as easy to understand as it is ingenious.


The paths of the individual primary colours in the Casio projector

We start with the red part which is emitted from an LED. The latter is located on the right in the picture and is covered by a ribbon cable. It shines straight through a semi-transparent mirror (long red arrow) before the light beam is diverted by a semi-transparent mirror down to the encapsulated optical path. From here it is directed to the DMD which modulates the brightness proportion based on pixels, before leaving the projector through the long optic.

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It becomes more complicated when the blue and green spectral components of the colour representation are taken into consideration. For the sake of precision, we will take a look at the associated "colour wheel" which is only the size of a €2 coin. Instead of traditional colour segments, it consists of an aluminium disc, the edge of which is almost completely coated with phosphor. Only a very small part consists of a transparent glass window.


Phosphor-coated aluminium wheel

The colour wheel is illuminated in the light path directly by the blue light of the 24-diode laser module bundled through the mirror. If it hits the little "window glass" section, it passes the colour wheel unchanged. But if it hits the bright phosphor stripes, it emits green light animated by the laser energy, but not in the same direction. It reflects in the opposite direction. It is so to speak a phosphorus-mirror layer.



The green light has to be intercepted by a semi-transparent mirror in order for it not to radiate back into the light source. This reflects it away to the left (green arrows) where it is directed by another mirror to the encapsulated part of the light path towards the DMD chip / optics. Red and green lights appear alternately due to this simple principle. The energy loss through the phosphor conversion is compensated by the longer lighting time. This explains why the window on the colour wheel is so small in proportion to the phosphor.

The sequential colour display is typical of such a single-chip design, always making the display of primary colours on the screen appear in sequence. By using two light sources however, it is possible to mix red simultaneously with blue or green as desired with Casio projectors. "True" magenta or "yellow" also thus become possible, which allows a better use of brightness and higher colour purity than in conventional RGB colour wheels.

The technical structure of the hybrid projector shows how simple innovative constructions can be. The whole system combines conventional single-chip DMD projection systems using a colour wheel with modern light sources such as lasers and LEDs. From many years of experience, we know that at least the conventional parts of this structure (DMD chip / colour wheel) are nearly indestructible. The manufacturers claim that LEDs and laser diodes last 20,000 hours. If this is the case, then this projector is the most maintenance-free device that has been built. For continuous commercial use in particular, this is a unique feature and economic benefit (especially in combination with the low purchase price), which leaves the competition standing.

The only feature to be criticised however is the noise level. It is a misconception that LEDs and laser diodes do not require cooling. Although they are good at attaining a much higher light conversion of the input energy than conventional UHP lamps, there is still a substantial loss of heat. In simple terms, LEDs and lasers with high output are literally hot, very hot! And since they are also very sensitive to heat, effective cooling is a must. This is done in the Casio models very traditionally and conservatively by fans. And since the chassis is designed so compact and flat, these fans in turn have to have a very small diameter, and offset a lack of size with higher speed. A high speed means more air movement and associated noise. The equally small colour wheel and the high frequency switching electronics of LED & laser unit provide additional background noise, so that the projector is not below 29dB even in eco mode.

The noise level for a presentation projector is normal in eco mode, but in the lighter stages it is disturbing, and even unacceptable for home cinema. In our estimation, the chassis could have been designed somewhat higher to reduce noise without losing portability.

That was the technology, but what kind of image is displayed on the screen? Does it have more to offer than conventional UHP projectors, or does it have serious drawbacks? To assess this, we took the projector into operation and dealt first with the settings options of the picture menu.

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2. Operation & Provided Options

As innovative as the technical design is, so simple and outdated are the on-screen menus. In various categories, there are only Spartan options with which to control the image display.



"Picture Settings 1" offers only controls for brightness, contrast, colour balance and colour mode. The latter term is also misleading, since these are general presets for different applications affecting not only the colours.



"Standard", "Graphics", "Cinema" and "Scoreboard" are the default choices. We will examine how they affect the image display in the picture display section.

PIC

We will skip the “Volume Settings" heading, as they deal only with the internal audio speakers, and find a trapeze balance under "Display Settings" which is almost indispensable in a presentation projector. Front-/Back-/Cover/Table projection can be programmed here. The settings options for the other parameters are purely cosmetic.



In the "Options Settings 1" menu, we finally found the important "Eco mode" option, with which the brightness and associated power input and noise level of the fan can be controlled. What is interesting is the fact that the projector not only offers two levels here, like almost every other projector on the market, but three.



Under "Operation Information", we finally obtained useful information about how the video signal is fed. A control option like this is especially useful with PCs which often do not do what they should.

The entire menu system is controlled by a small remote control as is typical for compact presentation projectors.



The mini-remote is anything but practical, but at least the manufacturer did without the otherwise popular "credit card" infrared sensors. After all, it provides a complete d-pad and useful shortcuts for the eco mode and adjusting the lens.

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3. Picture Display

In this part of our great Special, we will finally see whether the new hybrid technology has more to offer in picture quality than conventional UHP lamp projectors, or whether the benefits are limited only to the life and reliability. What type of a picture does the combination of laser and LED produce?

Given the scarcity of opportunity to control the picture, you have to rely heavily on the factory pre-settings in terms of picture quality. We therefore examined them in relation to fundamental picture features ... we limited ourselves to the aspects of image display which can actually be affected by the new lighting technology.

3.1 Colour display

In our testing of LED projectors optimised for home cinema, we have learned that they excel in a particularly pure colour display and can thus produce very strong colours. For this reason, we anticipate the biggest differences to conventional projectors in this area.

First, we looked at the primary colours on the screen with the help of picture filling test images. Where green is concerned, there is nothing worth noting at first. Its colour tone is very comparable to that of conventional UHP projectors.


Spectral analysis of green

Evidently, the phosphorus compound has been optimised for high light output with a large yellow content. This is certainly legitimate in a presentation projector. But it does not offer any benefits in terms of colours.

The situation is different for red. Here, there is such a strong and pure red displayed on the screen, which is simply not possible for a projector without LED. We photographed both colours simultaneously to illustrate the difference between standard-video standard-red.


Compared to the LED red (left), the video standard-red seems orange

Please note that the above picture can differ greatly from the visual impression depending on the computer monitor (for example, because your monitor can not reproduce LED-red). The spectral measurement proves our visual impression. The great advantage of LED is that it has a very, very narrow band frequency characteristic, close to the target colour.


Spectral analysis of red

Conventional UHP lamps have their weaknesses in the red area in particular. They do not emit enough red components, so they lose a lot of light during calibration.

We were even more amazed by the blue primary colour. The Casio also displays it more strongly and purely than we have seen on any projector, even with LEDs.



This can be explained by the known property of lasers. They only emit a single wavelength of light, so to speak accurately to the desired colour. Our spectral evidence of this:


Spectral analysis of blue

The blue laser light behaves as sharply as a needle, and is thus more accurate than LED, and than UHP anyway. In terms of colour purity, laser is undoubtedly a reference.


Spectral analysis of white

The above measurement shows the full spectrum of white as emitted by Casio hybrid projectors. It is certainly as unique as a fingerprint and has "a bit of everything". It has green like a conventional projector, red like an LED projector and blue like no other device on the market. What does this result mean in terms of the corresponding colour space?


Native colour space of the Casio

The colour space is no less spectacular. There is barely enough space in the diagram for red and blue. Green, on the other hand, is in the typical green / yellow range. For applications that require very pure and strong colours, the Casio is certainly without competition, especially in this price range. With respect to the conventional video standard however, such differences are rather counterproductive, since they produce oversaturated colours and compensate the image naturalness. The engineers were evidently aware of this because they tried to trim the colour space in the direction of video standard in the presets "Cinema" and "Graphics".


Reduced colour space of "Cinema" and "Graphics"

Now it is not so easy to trim a projector in terms of primary colours because you have to mix in each of the other colours to each primary colour in order to reduce the colour space. You then have to use these "mixed" colours as a base colour for the actual picture colour mixture. The (still) exotic light sources of the Casio projector also make this more difficult, thus the video standard colour space in this first generation is only moderately successful.

Unfortunately, the projector also has no colour management function, meaning that the user cannot optimise the colour space alone. The next generation clearly has to provide an improvement here.

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The colour temperature demonstrates the advantage of LED technology. The projector is close to the video standard even if you almost exhaust all the light reserves, as there is not such a big red loss as with UHP lamps. The “Cinema” preset is the most precise although not perfect.


The Cinema preset is close to the D65 standard

There are, after all, subsequent correction options here. The user can mix the RGB channels in the “Colour Balance” picture menu, but not separately for light and dark.



What type of colour quality do these optical properties deliver? To test this, we fed the Casio with various images. The result is impressive for animated films in which chromaticity and accuracy of colour are important. No other projector produces red and blue colours as purely and radiantly as the Casio. Films like "Finding Nemo" and "Cars” get a new dimension in the truest sense of the word. The Casio is beaten by the LED projectors only when displaying green.

The projector also shows benefits for picture material that was recorded taking a large colour space into account. Be it the pure colours of natural flowers or a bright colour advertisement etc., wherever highly saturated colours are evident in reality, the Casio is in a position to reproduce these more credibly.

The case is similar with video, but with one limitation. Our software in Blu-ray, DVD & co. is not adapted for large spaces, but more for the traditional video standard. The projector must also be trimmed to the video standard in order to play properly. And despite the "Cinema" preset with reduced colour space, the Casio projector shows great weaknesses in this domain. Our view test showed that blue tones compounded the problem. Particularly dark picture scenes often tended to look violet, and lost credibility. This is certainly due to the frugal colour space program of the software. For playing films, the projector can only be recommended if strong colours are more important to you than colour accuracy. With these first generations devices, Casio has yet to prove that hybrid technology is in a position to produce perfect colours from conventional video.

3.2 Contrast, brightness, and plasticity

The aspect of image plasticity is also of interest. Anyone who knows a little about presentation projectors will know that they are trimmed to a luminous efficacy above all, whereby the contrast and black level are rather neglected. Even though modern devices usually have a light output of more than 2000 lumens, they only have a contrast of 1000:1. Hence the poor black level and the plasticity in dark scenes. You should not forget that when conducting this test the Casio models are not devices optimised for home cinema but ultra- portable presentation devices with one predominant goal: lots of light.

As explained in the technical part of the Special, the projector has three "Eco modes". The manufacturer specifies the maximum light output with up to 2,500 lumens. To test this, we switched our test model to the highest lamp mode. If you activate this, the image menu changes and offers an even brighter mode, a kind of "Brilliant colour". To really get the maximum light output, we took the contrast control up to the clipping (overdriving) border as the last step. Despite these measures, our test model clearly missed the 2500 lumens mark, more than 1,700 lumens were simply not to be teased out of it. Nevertheless, it is an impressive value at this mark, and this proves that UHP lamps are no longer needed even for high light output. By the way, in high "Lamp" mode, the colour space cannot be changed. If you want it to be “bright” you have to be prepared to deal with “colourful” too.

The fact that the projector loses hardly any light and contrast through calibration is positive. The discrepancy between maximum brightness and colour accuracy is reduced with LED and laser at last. The high light output of the eco modes is also positive. Even in the highest power saver mode, the only one with a moderate noise level, the little Casio still reaches about 800 lumens. Many is the home cinema projector that can only dream of such brightness.

The only thing left is contrast. The manufacturer did without the contrast-increasing measures that the new LED / laser technology would easily allow. Thus, the device provides no adaptive light control. The LEDs will not dim the image content in real time as with the LED home cinema projectors. The manufacturer specifies a contrast ratio of 1800:1 in the technical data, which we confirmed through precise measurements in our test.

The contrast of 1800:1 is "honest" native contrast which is fully available for image display. It is to Casio's credit that they were not tempted to simply switch off the LED / laser for black and let the technical data soar in contrast to six or seven-digit "values". For stubborn "comparers of data" that may even give them a competitive disadvantage, as many competitors install extra adaptive apertures for “styling” the contrast values. But, in use, these are so bad that they do not increase the image plasticity in the video image.

In practical tests, the high native and honest contrast is rewarded. Adjusted properly (ex works the levels are unfortunately completely blocked), the small Casio offers an excellent balance of black level, brightness and image contrast in the eco mode. The visual plasticity is in fact so good that it leaves almost all home cinema projectors in the same price range standing. This result is quite remarkable for a presentation projector not optimised for contrast.

It is becoming apparent that hybrid technology is suitable for very high image plasticity. With high-quality, larger light path and an intelligent adaptive lighting control system (similar to the LED projectors), it is conceivable that reference performance can be achieved. Only the D-ILA technology would have to still admit defeat.

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3.3 Digital DLP artefacts

Many home cinema fans now have such high demands on the image quality that the typical single-chip artefacts have become knock-out criteria. These include the infamous "rainbow effect" in particular, which produces colour flashes in the primary colours in strong contrasts.

A solution has finally been found with LED technology. The three light sources are each clocked so high (900Hz and above) that the sequential colour generation remains unnoticed for our eyes. High-end LED projectors are finally free of rainbows.

Unfortunately, the situation is different for the Casio hybrid technology. As explained in the technology section, the Casio projector does not have an individual light source for all three primary colours, but green and blue are alternated by a conventional colour wheel. And such a colour wheel has mechanical limitations in speed so that high frequencies such as those in a 3-LED can not be reached.

As a result, it is then not surprising that the Casio projector behaves like a conventional UHP / single-chip DLP projector with a colour wheel when it comes to the rainbow effect. However, the resulting flash of colour is at a level that is acceptable for a conventional projector with 4-speed colour wheel (200Hz). Conclusion: the Casio is not better but no worse than its UHP colleagues in terms of rainbows.

The case is similar where noise is concerned. With a signal strength of 10% and higher, the screen image is noise free. The adjustable mirror frequencies of DMD chips are still recognisable on the screen.

4. Conclusion

The laser / LED hybrid technology was hailed as a “revolution” by its inventor Casio, and indeed it is in certain areas.

First of all, there are the economic benefits. If the device can actually maintain its purchase price of less than €1,000 with the promised 20,000 hours, the hardware price of only 5 cents per hour is substantially less than that of lamp devices. Apart from this, there are no benefits in terms of "Ecotec", as the projector really is not a savings wonder with an excess of 200W power input. The cooling by the small fan is also no louder than that of a lamp device.

There are more benefits in everyday use, on the other hand, as the LEDs have no warm up time and must not be cooled. The projector is “there” immediately after it is switched on, and can be disconnected from the mains immediately after being switched off - Plug & Play in its purest form.

In terms of image quality, the new technology proves that it is capable of producing very intense colours, and that there is no problem with brightness, even if the manufacturer’s data are not met. Particularly surprising is that a high contrast can be combined with lots of light, and that there is a lot of potential through future improvements.

No revolution however has been observed in the DLP typical artefacts. By using a colour wheel, the projector behaves exactly like traditional lamp models.

Overall, it's a great idea to be able to use a modern projector without worrying about the wear and tear of the lamp, just like a TV. Projectors are thus becoming more and more appropriate for everyday use, and the gap separating them from flat-screen TVs will continue to be narrower. The revolution has yet to take place in image quality in the short term, at least as long as the corresponding software support through Blu-ray and DVD is not in place.

13th April 2010

Ekkehart Schmitz

www.Cine4Home.com

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