Projection Display Diaphragm Contrast Brightness Trade-off
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Solution Overview
Problem
Existing projection type display apparatuses face challenges in enhancing contrast while minimizing a reduction in brightness, due to the characteristics of light sources and optical parts.
Innovation Solution
The apparatus employs a combination of diaphragms in the illumination and projection optical systems, with the illumination diaphragm having a rectangular shape and the projection lens diaphragm having a rhombus shape, to adjust contrast and brightness by blocking diffracted light and optimizing the incidence polarization direction, thereby enhancing contrast performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If smaller F values are used for illumination and imaging optical systems, then brightness increases, but contrast deteriorates due to increased incidence angles
Solution Approach 1:
The patent divides the optical system into multiple segments with independent diaphragms: an illumination optical system diaphragm and an imaging optical system diaphragm. Each diaphragm can be independently adjusted to control the incidence angle of light rays at different stages of the optical path, allowing separate optimization of brightness and contrast parameters
Solution Approach 2:
The patent applies different diaphragm configurations to different parts of the optical system. The illumination diaphragm controls the overall light cone angle, while the imaging diaphragm specifically controls the angle at the liquid crystal display device. This localized control allows each segment to be optimized for its specific function while maintaining overall system performance
2Manufacturing precision
If larger F values are used for illumination and imaging optical systems, then contrast improves, but brightness decreases
Solution Approach 1:
The patent introduces adjustable diaphragms that can dynamically change the effective F values of the optical systems. By moving the diaphragms to different positions, the system can adaptively adjust the light cone angles, allowing the F values to be optimized in real-time based on whether contrast or brightness is the priority
Solution Approach 2:
The patent changes the geometric parameters of the optical system by introducing diaphragms with specific aperture sizes and positions. The diaphragm aperture diameter and distance from the liquid crystal display device are adjusted to control the maximum incidence angle, thereby changing the effective F value and optimizing the balance between contrast and brightness
3Device complexity
If a single diaphragm is used in either illumination or imaging optical system, then device complexity is reduced, but contrast enhancement capability is insufficient
Solution Approach 1:
The patent segments the contrast control function into two separate diaphragms located in different parts of the optical system. The illumination diaphragm controls the light source distribution, while the imaging diaphragm controls the light incident on the display device. This segmentation provides superior contrast enhancement compared to a single diaphragm while maintaining reasonable structural complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively increases contrast by about 10% while minimizing brightness reduction, by preferentially blocking low-angle light components with low contrast and maintaining sufficient brightness, demonstrating improved contrast performance.
Implementation Method 1
preferentially blocking diffracted light
Implementation Method 2
a liquid crystal display device and a polarization device such as a polarization beam splitter have incidence angle dependencies
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
It is to provide a projection type display apparatus which enhances the contrast performance while minimizing a reduction in the brightness by blocking a light beam which would decrease the contrast through the use of diaphragms provided in both of an illumination optical system and a projection lens. [Solution] A light source portion 1 and 2, a first lens array 4, a second lens array 5, and a superposition lens 7 constitute an illumination optical system. An illumination diaphragm 8 located in the vicinity 7 of the second lens array becomes a diaphragm aperture in a rectangular shape when being narrowed, wherein a side of the diaphragm aperture in the rectangular shape and longer side directions of the lens cells of the second lens array 5 are perpendicular or parallel to each other. A liquid crystal display device 17 modulates incident light. A projection lens 19 enlarges and projects modulation light. A projection lens diaphragm 20 becomes a diaphragm aperture in a rhombus shape when being narrowed, wherein a diagonal line of the diaphragm aperture in the rhombus shape and directions of sides of lens cells in a pupil image of the second lens array 5 which is formed in a pupil position of the projection lens are perpendicular or parallel to each other.