Projection Apparatus Sync Pulse Color Correction
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Solution Overview
Problem
DLP projectors using semiconductor light-emitting elements, such as LEDs and laser diodes, face issues with unnatural image perception due to yellowish black appearance caused by sync pulses influencing viewer perception, especially when using liquid-crystal shutter eyeglasses.
Innovation Solution
The projector employs a gamma correction method to adjust the blue light component's gradation to complement the yellow sync pulse, converting it into a gray component, ensuring that the stereoscopic images appear natural by minimizing the luminance impact of the yellow sync pulse during dark image projection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sync pulses of high luminance are inserted to enable liquid-crystal shutter eyeglasses to switch between left-eye and right-eye images, then the stereoscopic image switching is achieved, but the yellowish black appearance and unnatural image perception occur due to the luminance difference influencing viewer perception
Solution Approach 1:
The patent changes the color of the sync pulse from yellow to blue by driving only the blue light-emitting element during the sync pulse period, while suppressing the red and green light-emitting elements. This color change makes the sync pulse less perceptible to viewers, eliminating the yellowish black appearance problem while maintaining reliable stereoscopic image switching functionality.
Solution Approach 2:
The patent changes the luminance parameter of the sync pulse by controlling the drive current to the blue light-emitting element, adjusting it to be lower than the luminance of the blue image field. This parameter adjustment reduces the perceptibility of the sync pulse, preventing the unnatural yellowish black appearance while maintaining the reliability of image switching.
2Reliability
If multiple semiconductor light-emitting elements are driven simultaneously to generate sync pulses, then the sync pulse is generated, but the yellow light component influences viewer perception making dark images appear yellowish
Solution Approach 1:
The patent extracts and removes the harmful yellow light component from the sync pulse by suppressing the red and green light-emitting elements during the sync pulse period. Only the blue light-emitting element is driven, which eliminates the yellow light component that causes the unnatural appearance in dark images, while maintaining sync pulse generation for reliable image switching.
Solution Approach 2:
The patent converts the potentially harmful high-luminance sync pulse into a beneficial low-perceptibility signal by using blue light instead of yellow light. The blue sync pulse maintains the necessary function for image switching while being less perceptible to viewers, thereby converting a harmful visual artifact into a beneficial imperceptible signal.
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 approach effectively reduces the unnatural yellowish tint in dark images, providing a more natural viewing experience by canceling out the yellow component with a gray component, thus enhancing the image quality without adding complexity or additional components.
Implementation Method 1
each semiconductor light-emitting element basically emits a beam of one color only
Implementation Method 2
The projector employs a gamma correction method to adjust the blue light component's gradation to complement the yellow sync pulse, converting it into a gray component
Data Source
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AI summary
A projection apparatus includes a light source unit (15) including a plurality of semiconductor light-emitting elements (18, 19), an input unit (11) for inputting a video signal, a projecting unit (12-17) for forming an optical image according to the video signal input by the input unit (11) and projecting the optical image, using light coming from the light source unit (15), and an image converting unit (12) and CPU (28) for simultaneously driving the semiconductor light-emitting elements (18, 19) included in the light source unit (15), and generating a sync signal for use in projecting a stereoscopic image, and correcting gradations ranging from zero gradation to the gradation according to the luminance level of the sync signal, to a specific gradation, when the projecting unit (12-17) forms an optical image of a color complimentary to the color of the sync signal.