Staggered Phosphor Wheel Timing for Projector Flicker Reduction
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Solution Overview
Problem
Projectors using semiconductor light-emitting elements and phosphor wheels experience flicker in projected images due to cyclic decreases in light emission caused by phosphor seams, which is exacerbated when multiple phosphor wheels are synchronized, leading to increased brightness fluctuations.
Innovation Solution
A projector configuration with multiple phosphor wheels where the rotation timing of each wheel is controlled such that the minimum light emission occurs at different times, and the excitation light is irradiated on seams at non-synchronized angles, using a phosphor rotation control unit and optical sensors to detect reference positions and adjust rotational speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple phosphor wheels are synchronized to rotate at the same timing, then the brightness of projected light is increased through synthesis, but flicker in the projected picture is exacerbated due to simultaneous light decreases at seams
Solution Approach 1:
The patent applies periodic action by rotating multiple phosphor wheels at different phase angles so that each wheel passes through its minimum brightness point (at the seam) at a different time. This staggers the periodic light decreases, preventing them from occurring simultaneously and thereby reducing flicker while maintaining increased overall brightness through the combined light output of multiple wheels.
Solution Approach 2:
The patent introduces asymmetry in the rotational timing of multiple phosphor wheels by setting different phase angles for each wheel. Instead of symmetric synchronous rotation, the wheels are deliberately desynchronized, creating an asymmetric temporal pattern of light emission that prevents simultaneous brightness drops and reduces perceptible flicker.
2Ease of manufacture
If phosphor segments are adhered along the circumference to form phosphor wheels, then the structure is simplified and manufacturing is easier, but seams between adjacent phosphors cause cyclic decreases in light emission
Solution Approach 1:
The patent accepts the segmented structure of phosphor wheels as a manufacturing advantage but mitigates its harmful effect by using multiple segmented wheels with different phase angles. The segmentation is maintained for ease of manufacture, but the harmful brightness drops are staggered across multiple segments on different wheels, preventing simultaneous decreases and reducing flicker.
3Stability of the object's composition
If phosphor wheel rotation is synchronized with display device drive cycle, then the rotational speed can be fixed for stable operation, but the timing of minimum light emission coincides with drive cycle causing visible flicker
Solution Approach 1:
The patent maintains fixed rotational speeds for stability but introduces different phase angles in the periodic rotation of multiple phosphor wheels. This creates staggered periodic action where the minimum brightness points occur at different times, desynchronizing the flicker effect from the display device drive cycle and making flicker less perceptible.
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 reduces flicker perception in projected images by ensuring that light decreases are staggered, making the brightness fluctuations less noticeable, and decreases the proportion of change in synthesized light, thereby minimizing image flicker.
Implementation Method 1
a phosphor wheel in which a plurality of arc-shaped phosphor segments are affixed, each phosphor segment taking light from one of the light sources as excitation light to emit light
Data Source
AI summary
A projector has: a plurality of light sources, a plurality of phosphor wheels to which are affixed a plurality of arc-shaped segments of phosphor that takes as excitation light the light from the light sources to emit light, a synthesizing optical system that synthesizes light emitted by the plurality of phosphor wheels, and a phosphor rotation control unit that controls the rotation of the plurality of phosphor wheels such that the timing at which the quantity of light emitted by the phosphor wheels becomes a minimum value differs for each of the plurality of phosphor wheels.