Projectors use different kinds of light sources, but those that use lasers produce bright, vivid images, have long life, and can be set in any position.
Here we introduce the laser light source and the technologies making the most of their features, not only for home and business use but in a growing array of applications, including educational settings and projection mapping at shopping complexes.
A projector works by shining light. The light undergoes a number of processes before projecting a generated image onto a surface. Traditionally, UHE (Ultra High Efficiency) lamps were the most common light source used in projectors, but as the uses of projectors expanded, projectors using LEDs or lasers as light sources were rapidly developed.
Because the light source of a laser projector has such a long life, projector users have to change lamps and perform maintenance far less often. This ensures high reliability and lower running costs. In addition, whereas projectors with UHE lamps have to be placed in a certain position to get stable performance from the lamp while it is on, laser projectors can be placed at any angle. They can easily project onto the ceiling or floor and create immersive experiences like with projection mapping and digital museums. Laser projectors, moreover, provide sufficient brightness as soon as the power is turned on, so they are ready to start projecting faster than a product with a UHE lamp. There are also big environmental advantages of laser projectors because they don't use mercury and consume less power.
Epson laser projectors use energy-efficient, long-life blue lasers as the light source together with a durable phosphor. But lasers need light from the three primary colors of red, green, and blue so there needs to be a way to get all three colors from a blue laser.
First, the blue light from the laser is separated into two paths by a dichroic mirror. One path is condensed by a phosphor and the other by a diffusion plate. Light that falls on the phosphor turns from blue to yellow, while light that falls on the diffusion plate eliminates coherence, a cause of a kind of glare called speckle. The light on the two paths is reunited by a dichroic mirror to generate white light.
In addition, Epson has a proprietary light source optical system with a mechanism that uses the properties of polarized light to adjust the ratio of blue and yellow to achieve optimal color balance.
Adopting a laser light source increased optical efficiency and helped make projectors brighter, but it also created a need to make optical components more heat-resistant and durable. One technology for doing that is called GL (glass-like) bonding, which is used on polarization converting elements and quartz retardation plate.
Polarization converting elements and quartz retardation plate are made by bonding panels of materials like glass and crystals. Traditionally, panels would be bonded with organic adhesives, but organic adhesives are a problem due to deterioration caused by light and heat. That is why we use GL bonding. Epson developed the technology that uses a glass-like bonding membrane to bond the crystal and glass. As a result, our projectors have nearly 20 times as much heat-resistance and durability as those with organic adhesives. Another feature of this technology is that it allows for a thinner bonding surface. Epson takes advantage of this to increase transmittance ratio and optical efficiency.