Lcos projection technology introduction

Lcos projection technology introduction

LCOS (LiquidC which talOnSilieon) technology is a new type of liquid crystal microdisplay technology developed in the past few years. After the technology was introduced, large and small companies all over the world are very interested in it. It is agreed that LCOS micro display technology is the most in the field of projection. Competitive technology "33]. In recent years, through various efforts (chip or panel design manufacturers, light engine design manufacturers and system integration manufacturers), LCOS liquid crystal projections (including backs) manufactured by LCOS technology The performance of projectors and front projectors has been continuously improved and gradually matured. From trial production to small batch production to mass production, their products have gradually been recognized by the market and have been sold in large quantities in the North American market. LCOS technology is in LCD technology. Developed on the basis of, therefore, they have many similarities, for example: LCOS panel and LCD panel work must use polarized light, because both are liquid crystal devices. Using the image signal voltage applied to the pixel electrode Acting to change the alignment (orientation) of liquid crystal molecules perfused in the pixel, so that the liquid crystal layer modulates the luminous flux transmitted through it to form an image light signal, the difference being LC D is a light transmitting device, that is, light is emitted through the liquid crystal layer; and LCOS is a light reflecting device, and light enters the liquid crystal layer and is reflected back and emitted from the incident surface of the light. From the perspective of polarized light, S polarization After the light enters the LCD panel, the output light is still S-polarized light; and in order to avoid the interference of the incident light and the reflected light, the S-polarized light enters the liquid crystal layer of the LCOS device, and the polarized light output after the reflection is no longer S-polarized light. Instead, it is called P-polarized light by PBS. Compared with LCD micro-display technology, LCOS micro-display technology has obvious advantages [7].

(1) The LCOS panel has a large aperture ratio and high light utilization efficiency, and thus the projector made of the LCOS panel has high brightness.

(2) Only TFTs are fabricated in the LCD panel, and other panel driver ICs are on the outside of the panel. The LCOS panel integrates the panel driver IC and peripheral circuits, which greatly reduces the LCOS peripheral leads and improves reliability.

(3) The LCOS panel can be produced in a general 2.5 micron CMOS process, so its manufacturing cost is low, which is one of the greatest advantages of the device.

(4) LCOS technology has fewer patents.

LCOS panel structure and working principle

The basic meaning of LCOS is liquid crystal on silicon wafer, now known as liquid crystal on silicon, is a liquid crystal reflective device. Its structure is shown in Figure 3-1. The driving array circuit and the liquid crystal driving circuit are integrated on the silicon wafer by a CMOS process on the single crystal silicon wafer, and the liquid crystal electrode is plated with an aluminum material as a mirror, and the electrode is used as a substrate and a transparent semiconductor electrode (ITO) opposite thereto. The liquid crystal is poured between the plates. The black and white small grid in the figure indicates a driving circuit integrated on a silicon substrate. The small round objects on both sides of the liquid crystal layer serve to seal and support, and the top is the glass cover plate, thus forming an LCOS liquid crystal pixel, which is shown in Figure 3-2.

The incident light enters the polarization converter PBS, which reflects the S-polarized light, and the S-polarized light passes through the glass cover plate and the ITO common electrode into the liquid crystal layer, is reflected by the underlying aluminum-plated electrode, and passes through the liquid crystal layer, the ITO electrode, and The glass cover enters the polarization converter and becomes P-polarized light. The polarization converter is used to separate the incident light and the reflected light, which ensures that the contrast of the LCOS panel is not affected. Since the aluminized electrode is a liquid crystal control electrode, there is an image signal voltage thereon, and the liquid crystal molecules change the orientation state due to the effect of the image signal voltage, and the emitted light flux is modulated, and the sum of the reflected light of the pixel array forms the image light. The signal is then focused by the projection lens, amplified, and projected onto the projection screen to form a light image [9].

Figure 3-2 Working principle of LCOS pixels