Variable Aperture Iris Control for Display Contrast and Brightness
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Solution Overview
Problem
Liquid crystal projectors face limitations in achieving high contrast ratios in dark scenes while maintaining brightness in bright scenes, leading to inferior image quality due to the iris ON/OFF mode switching mechanism.
Innovation Solution
A display device with a variable aperture iris and a control circuit that adjusts the iris opening/closing response differently based on signal level changes from dark to bright and vice versa, along with a signal adjustment unit to fine-tune the gain, ensuring optimal contrast and brightness adaptation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the iris is turned on to lower the black level and improve contrast ratio in dark scenes, then the contrast ratio is improved, but the white level is lowered and luminance in bright scenes is correspondingly lowered
Solution Approach 1:
The patent implements dynamic iris control where the iris opening degree is automatically adjusted based on the luminance level of the input image signal. In dark scenes, the iris closes to improve contrast ratio, while in bright scenes, the iris opens to maintain luminance. This dynamic adaptation resolves the contradiction by making the iris state dependent on scene conditions rather than fixed.
Solution Approach 2:
The system changes the iris opening degree parameter according to the luminance characteristics of the displayed content. By detecting the average luminance level and adjusting the iris aperture accordingly, the system optimizes both contrast ratio and luminance for different scene types, eliminating the trade-off between these two parameters.
2Measurement precision
If a fixed light blocking rate is set for the iris, then the contrast ratio improvement is limited, but the system complexity is reduced
Solution Approach 1:
The patent employs a feedback mechanism where the luminance level of the input signal is detected and used to control the iris opening degree. The control circuit continuously monitors the image signal characteristics and adjusts the iris aperture to achieve optimal contrast ratio, thereby resolving the limitation of fixed light blocking rates through automatic adaptive control.
Solution Approach 2:
The system performs self-adjustment by automatically detecting scene luminance characteristics and controlling the iris aperture without requiring manual intervention. The control circuit independently optimizes the contrast ratio based on the input signal properties, eliminating the need for complex manual configuration while achieving superior contrast performance.
3Stability of the object's composition
If the iris response is slow when transitioning from dark to bright scenes, then the iris stability is improved, but the image quality during transition deteriorates
Solution Approach 1:
The control circuit predicts the need for iris adjustment by detecting luminance changes in advance and initiates iris opening/closing actions proactively. When a transition from dark to bright scene is detected, the iris begins opening before the full brightness change occurs, ensuring smooth transition and maintaining image quality while preserving stability during steady states.
Data Source
AI summary
A display device able to give an image giving a good impression such as a sharp contrast in a dark scene and maintaining brightness in a bright scene, that is, a display device comprising a variable aperture iris and a control circuit for controlling opening/closing of the iris in accordance with a state of a level of an input signal forming a screen, wherein the control circuit controls the iris so that a response of an open/close operation of the iris is different between a case where the signal level fluctuates from a dark level to a bright level and a case where the signal level fluctuates from a bright level to a dark level.