Video Projector Color Correction via Camera Exposure Synchronization
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Solution Overview
Problem
Existing methods for color correction in video projection, such as JP 4120841 B2, fail to accurately acquire color information when using a color time division projector with a rolling shutter camera, leading to color discrepancies between the upper and lower portions of the projected image.
Innovation Solution
A video projection system that includes a color corrector capable of synchronizing the time division period of the projector with the exposure time of the camera, using either an internal or external imaging apparatus, to perform color correction based on detected color information, integrating color information across multiple frames to compensate for exposure time differences and rolling shutter effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a color time division projector is used to project videos, then the projector can display multiple primary colors efficiently, but the exposure time of the camera cannot be synchronized with the time division period, causing excess or deficiency in exposure time for each primary color and inaccurate color acquisition
Solution Approach 1:
The patent applies preliminary action by pre-setting the camera's exposure time to match the projector's time division period. The exposure time is calculated based on the formula Texp = (1/f) × (M/N), where f is the frame rate, M is the number of primary colors, and N is the duty cycle. This pre-synchronization ensures that each primary color is captured during its specific time window, resolving the exposure timing mismatch before color acquisition begins.
Solution Approach 2:
The patent implements periodic action by synchronizing the camera's exposure cycles with the projector's time division periods. The camera performs repeated exposure cycles at the same frequency as the projector's color switching, ensuring that each exposure cycle captures the complete sequence of primary colors in the correct temporal order. This periodic synchronization eliminates exposure time excess or deficiency for each primary color.
2Productivity
If a rolling shutter camera is used to image the projected video, then the camera can capture images continuously, but a time difference occurs in the start of exposure between upper and lower portions of the imaging sensor, causing color differences in different portions of the imaged image
Solution Approach 1:
The patent applies preliminary action by calculating and setting the exposure start time for each row of pixels based on their vertical position. The exposure start time for row i is offset by (i × row_period) from the top row, where row_period is the time for the scanning beam to move to the next row. This pre-calculated timing compensation ensures that all rows capture the same temporal phase of the time-division colors, eliminating color differences across the image.
Solution Approach 2:
The patent implements local quality by applying different exposure timing to different rows of pixels based on their vertical position. Each row has a customized exposure start time that compensates for the rolling shutter delay. This localized timing adjustment ensures that each row captures color information consistent with the projector's time division, resolving the color inconsistency caused by the rolling shutter effect.
3Device complexity
If color correction is performed without synchronizing exposure time with time division period, then the color correction process is simpler, but the color information acquired is inaccurate due to exposure time mismatch
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the camera's exposure time parameter to match the projector's time division period. The exposure time is set to Texp = (1/f) × (M/N), where this parameter change ensures that the exposure duration corresponds exactly to the projection duration of each primary color. This parameter adjustment maintains color information accuracy while keeping the color correction process relatively simple.
Data Source
AI summary
An object is to provide a technology for correcting color of a projected video more suitably. In order to solve the above-described object, a configuration includes a video projector configured to display a plurality of colors in time division and project a video to be displayed, and a color corrector configured to perform color correction on a projected video from the video projector. In the configuration, the projected video projected by the video projector is imaged by an internal imaging apparatus or an external imaging apparatus connected by wire or wireless connection, and the color corrector performs the color correction on the basis of a video corresponding to time division one period of the projected video detected from the imaged image or color information of the video corresponding to N times period of time division one period.