In recent years, with the maturity of large screen projection display technology, home projectors are increasingly becoming the target of consumers. Projectors with different technologies such as LCD and DLP follow Moore's Law. Many projectors are cheaper than large size televisions. Consumers seeking good audio-visual experience have added projection equipment to their homes. I have to mention that LED/laser projectors have also entered the eyes of consumers. What are their advantages over traditional projectors?

Projection light source

Whether the technology used by the manufacturer is 3LCD (Liquid Crystal Display) led by Epson, DLP (Digital Light Processing) invented by Texas Instruments, or LCOS (Liquid Crystal on Silicon), the light source lighting system is the premise of the design of the entire projection optical system, and the light source used by the projector is very important. At present, metal halide lamps, UHE/UHP lamps, xenon lamps, LEDs and lasers are common, among which metal halide lamps are thermal light sources and have basically been phased out; UHE/UHP is an ultrahigh pressure mercury lamp, which uses the optical principle to filter out the infrared ray and is a cold light source; The spectrum of xenon lamp is the closest to natural light; LED and laser have gradually entered the consumer market in recent years.

life

(UHP patent invented by Philips)

Anyone who has used a traditional projector will have experience: after a period of use, the brightness and picture quality of the projector will gradually decline. Replacing bulbs is an indispensable cost for long-term use of the projector. The service life of metal halide lamp is about 1000 hours, UHE/UHP is generally 4000-6000 hours, xenon lamp is about 1500 hours, LED is 10000 hours long, laser is more "long-life" than LED, and can reach more than 20000 hours.

Taking S1 Pro, the cheapest laser projector nut at present, as an example, the official label indicates that it can be used continuously for more than 30000 hours, even if only half of it is 15000 hours, which is almost three times as much as using UHE/UHP. LED/laser projector has great advantages in terms of service life and subsequent use costs.

brightness

An important parameter for the projector is the brightness of the projection, which is largely determined by the projection light source. In the early stage of development, although LED light source was superior to the original projector using traditional light source in all aspects, its brightness was always a hard wound. At the beginning of the commercial stage, because its relatively simple light path structure design could significantly reduce the size of the projector, the initial use of LED light source was basically small projectors. Fortunately, with the maturity of technology and innovation, LED light sources have basically caught up with traditional light sources. The brightness of Epson CH-TW5350 using traditional light sources is 2200 lumens, while nut G3 using LED light sources can already reach 4500 lumens (1000 if converted to ANSI).

In contrast, laser light sources with brightness more than 1000 times that of ordinary light sources have greater advantages in brightness. At present, most manufacturers use the DLP technology of Texas Instruments. The traditional light source first emits white light, and then it is decomposed into RGB three primary colors through the lens and color wheel and projected onto the DMD chip. The laser light source can be directly made into a three primary color laser by setting different wavelengths, The color wheel can be omitted (at present, the wavelengths commonly used for red, green and blue primary colors in China are 456nm, 532nm and 635nm respectively). Even if manufacturers only use monochrome lasers due to cost constraints, the color wheel cannot be omitted, and the brightness can be improved directly by increasing the number of lasers. Similarly, taking the nut S1 Pro, the most affordable laser projector, as an example, its brightness can reach 4000 ANSI, four times that of the nut G3 1000 ANSI just mentioned. BARCO's laser projector even reaches 11800 lumens.

Gamut

In addition to brightness, color gamut is also what everyone likes. When talking about color gamut, traditional light sources basically have no dignity. Since the development of LED, it has long since got rid of the restrictions of the original monochrome light source, and the LED light sources of white and RGB three primary colors have emerged, The solid color of RGB three primary color LED light source is very high. The three colors emit light in turn in chronological order, and the color gamut can easily reach more than 100%. The color restoration effect need not be mentioned. For example, the original G1 of nuts can easily reach more than 120% of NTSC.

Generally, the traditional light source can represent about 30% of the color that can be recognized by the human eye in nature, while the laser light source can represent more than 90% of the color that can be recognized by the human eye. There is a big gap between the two. From the chromaticity color synthesis, it is not difficult to see from the chromaticity diagram that if RGB three primary colors are used, the best effect needs to be designed into the largest triangle connected in the chromaticity diagram, that is, the three vertices are on the spectral path, and the red light is nearly 700nm, the green light is between 515-520nm, and the blue light is nearly 400nm. In fact, the only light source that can meet the requirements is laser, This is why many manufacturers are developing in the direction of laser. Taking nut S1 Pro as an example, even the brand's first laser projector has a color gamut covering more than 97% of Rec.709. It is not a problem to reach Rec.2020 in time.

other

In addition to the brightness and color gamut, LED/laser projectors also have proper advantages in contrast and other aspects - 50000:1 dynamic contrast and 1800:1 static contrast. The basic parameters of this laser projector have already dwarfed rivals. At the same time, because of the excellent directivity and polarization of the laser, its projection distance can be very short, which is very suitable for places with limited space. Real time focusing can also make users more convenient to use.

Back to the projector itself, because LED/laser is a cold light source and does not generate huge heat like traditional light sources, high-power cooling fans can be omitted in the design. The simple optical path structure has greatly reduced the volume of the optical projection part. The unique convergence of laser can also eliminate the internal condensing parts, and the size of the projector can be further reduced.

shortcoming

No man is perfect, no machine is perfect. Although LED/laser projector is all good, there are still some shortcomings. The common fault of LED is brightness, which is also mentioned above. If there is no major breakthrough in LED itself, you can only increase the number of LEDs if you want to improve the brightness, but the size of the light source as a projector cannot be too large, and increasing the number will also increase the cost accordingly.

The biggest problem of the laser projector is the potential safety hazard. Everyone knows that the laser cannot directly shoot the eyes. This is because the laser energy is quite concentrated, and direct irradiation of the human body will cause injury. A 150mW laser can easily burn the commonly used plastic film bags 1 meter away. Therefore, manufacturers need to take protective measures. Nuts are equipped with three sets of sensors in S1 Pro. When someone or something is detected approaching, the brightness will be automatically reduced, that is, the laser power will be reduced to ensure the safety in use. This should be the safety standard configuration of all laser projectors.

tail

Unlike projectors using LED light sources, which have entered the price of thousands of yuan, they can compete with traditional projectors in the market. Because of the high cost of laser generators and optical projection, laser projectors hover around tens of thousands of yuan, The latest S1 Pro of nuts barely dropped to the price of 20000 yuan without considering the cost (after all, the 0.65 '' DMD of a Texas instrument costs 1999 dollars), but there is still a long way to go before it can be widely popularized. However, with the progress of the times, LED/laser projectors will become the mainstream of the consumer market sooner or later, except that xenon lamps with high power and high brightness are required for special application environments such as military industry.

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