Tell me about some of the innovations of the AISYS optical system.
- Suzuki
- We wanted these projectors to be small enough for home use while ensuring sufficient brightness and contrast…well, I should let Okuyama and Kodama take up the discussion from this point, since they handled the optical design.
"The primary inspiration was the PBS itself. The PBS has different properties vertically and horizontally. To harness these properties effectively, we drew on the insights of a group member." (Kodama)
- Kodama
- To put it very simply, making projectors brighter and more compact at the same time means giving up contrast, unless you take other steps. That's essentially how these qualities are related. We can increase the angle of incidence on panels to improve brightness, for example, and bring the lamp closer to the panels. This makes the projector smaller. But light with a wide angle of incidence is undesirable from the standpoint of the PBS (polarization beam splitter), a fundamental component of LCOS projectors.
Can you clarify why some light is desirable or undesirable?
- Kodama
- LCOS and PBS technology relies on light polarization-you understand polarization, right?
That's where we cause light waves to oscillate in a particular direction. We use polarized glasses to watch 3D movies. And we use polarizing filters in photography. Like vertical blinds, a layer in this kind of filter has countless gaps that allow some light to pass through, gaps so thin they can't be seen. If you turn one layer parallel to another, all light is blocked out if they're turned so that they're 180º parallel to each other.
- Kodama
- That's the right idea, although there are no gaps. Projectors equipped with LCD panels use polarization to adjust brightness. The polarization works best and most accurately when light rays hit the PBS at 45º and the panels at 0º . The greater the departure from these angles, the lower the brightness.
So if the beam from the lamp strikes the PBS or LCOS panels at wide angles, these components won't work well.
- Kodama
- More precisely, the image areas that should be dark won't be completely dark. Light will leak through, reducing contrast. And we face the opposite problem when the lamp is farther from the panels. As light rays become more parallel, contrast intensifies, but illumination becomes unsatisfactory. That was the pattern with previous LCOS projectors.
So achieving better brightness diminishes the LCOS advantages, which are higher contrast and fuller gradation.
- Kodama
- Right. That's why so far we've seen LCOS-equipped products that sacrifice compactness and brightness to achieve contrast. To avoid such trade-offs, AISYS splits beams into vertical and horizontal components, then uses each component to enhance brightness or contrast. This is an effective, high-performance system.
Can light really be split into vertical and horizontal components?
- Okuyama
- Yes, though the optical engineering is a bit complex. We use a cylindrical lens - what we call a "compressor lens" in our company - array as the illumination optics from the lamp. From one perspective, the cylindrical lens array looks like a set of curved lenses, but viewed perpendicularly, it has parallel surfaces like a series of flat glass slides. Used vertically, this array focuses or disperses horizontal beams without affecting vertical beams. In this way, a single optical system changes the angle of incidence of vertical and horizontal components of light. This is the key to improving brightness and contrast at the same time.
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That's quite a discovery! Where did the idea come from?
- Okuyama
- The primary inspiration was the PBS itself. The PBS has different properties vertically and horizontally. To harness these properties effectively, we drew on the insights of a group member experienced in copier development. That's because copier optics generally incorporate cylindrical lenses.
