Cut-off filter

Abstract

The invention discloses a cut-off filter, which comprises at least 30 layers of high refractive index films and low refractive index films in total which are alternately distributed, wherein every 10 layers of films form a basic cycle layer; each basic cycle layer comprises a front reflection mirror, a composite interval layer and a back reflection mirror which are overlapped in sequence; the front reflection mirror is provided with three layers of films; the composite interval layer is provided with three layers of films; and the back reflection mirror is provided with four layers of films. The cut-off filter disclosed by the invention can serve as short-wave pass filter or long-wave pass filter specifically, an initial structure with a basic cycle of HLH2L2H2LHLHL is adopted, and the S and P polarizing separation and S and P polarizing position of the cut-off filter are extremely small in difference almost without polarization, so that the image definition and contrast degree can be obviously improved. The cut-off filter not only can be used for manufacturing a color separation and color image synthesis system with projected display, but also has important application value in the fields of optical communication and the like as well.

Description

technical field [0001] The invention relates to the field of cut-off filters in color separation and color image synthesis systems, in particular to non-polarized short-wave pass filters and long-wave pass filters. Background technique [0002] In a high-brightness digital projection display system, light energy utilization is the most important performance index. Therefore, reducing light energy loss and increasing display brightness to more than 30,000 lumens has always been a key technology that engineers and technicians urgently need to solve. [0003] In the existing color separation and color image synthesis systems for projection display, cut-off filters are required. Commonly used cut-off filters include short-wave pass filters and long-wave pass filters. Since the incident light must be at a certain incident angle At this time, the short-wave pass filter and the long-wave pass filter will produce greater polarization, resulting in greater S, P polarization separatio...

AI Technical Summary

Problems solved by technology

[0005] 1. The S and P polarization separations of the transmission spectroscopic curves of the short-wave pass filter and the long-wave pass filter are too large, which not only leads to loss of light energy, but also causes the lost part of the light to become stray light, resulting in a decrease in image clarity and contrast;

[0006] 2. The S and P polarization phase difference between the short-wave pass filter and the long-wave pass filter is too large, so that part of the light changes from linearly polarized light to flat elliptical polarized light. Since the incident light of the device is S linearly polarized light, the modulation The final outgoing signal light is P-linearly polarized light, and the S-polarized component in oblate elliptically polarized light will also lead to loss of light energy and introduction of stray light;

The prior art has never realized that the S, P polarization separation produced by the transmission spectroscopic curves of the short-wave pass filter and the long-wave pass filter will cause such serious consequences, and the prior art has never realized that the short-wave pass filter The S and P polarization phase difference of the long-wave pass filter will cause such serious consequences. The main reason is that the brightness and resolution requirements of general projectors are not very strict. This technology can only be used for high brightness and high-definition display. The key is highlighted

However, in high-brightness display, the temperature of the device itself is close to 70°C, and the accumulation of light energy loss caused by S, P polarization separation and S, P polarization phase difference greatly intensifies the temperature rise, which in turn produces thermal deformation of the optical surface. Further damage the clarity and contrast of the displayed image, and even cause the cracking of glass prisms and filter films

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