Dual-Modulator Projector Low Gray Value Representation
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Solution Overview
Problem
Projectors face difficulties in displaying low gray values effectively due to background brightness interference, leading to a poorer image impression, especially when multiple projectors are used to create a large image, as they struggle to distinguish between zero brightness and background brightness, resulting in flickering and incomplete gray value representation.
Innovation Solution
A projector control system that modulates the remaining light for pixels representing low brightness values, allowing for distinguishable representation of low gray values by switching associated pixels to a second state only during the image duration of the second pixel, thereby modulating the background brightness and enhancing image clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dithering methods (temporal or spatial) are used to represent low grayscale values, then the background brightness can be modulated to improve distinguishability of low gray values, but flickering effects are produced that distract viewers and reduce image quality
Solution Approach 1:
The patent applies periodic action by using temporal dithering to modulate the background brightness through periodic switching of pixel states across multiple frames. This allows low grayscale values to be represented by averaging the periodic on/off states of pixels, improving distinguishability while the periodic nature helps mask the flickering effect through consistent timing patterns
Solution Approach 2:
The patent segments the representation of grayscale values by separating the modulation of background brightness from the display of image content. Through spatial dithering, neighboring pixels are segmented into different states (on/off) within a single frame, allowing low gray values to be represented through the spatial distribution pattern rather than temporal flickering
2Area of stationary object
If multiple projectors are used to create a large image with overlapping edges, then the coverage area is increased, but the background brightness from multiple projectors adds up causing excessive brightness at low input brightness levels
Solution Approach 1:
The patent applies local quality by implementing different control strategies for different spatial regions of the projected image. Pixels at the overlapping edges of multiple projectors are treated differently from central pixels, with edge pixels having their background brightness component reduced or eliminated to prevent excessive brightness accumulation while maintaining proper illumination in non-overlapping regions
3Adaptability or versatility
If the lowest input grayscale values are displayed against background brightness, then the image can be projected with complete gray value range, but the low gray values become indistinguishable from the background brightness
Solution Approach 1:
The patent converts the harmful background brightness into a beneficial modulation carrier. Instead of treating background brightness as noise to be eliminated, the invention uses it as a medium to be modulated by dithering patterns, allowing low grayscale values to encode information in the temporal or spatial variation of the background brightness itself rather than trying to display against it
Data Source
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Figure 5~6
AI summary
A projector for projecting images is provided, comprising a first modulator (3) that can be supplied with light from a light source (2), and a second modulator (5) that is arranged downstream of the first modulator (3), and an imaging optic (4) that maps the first modulator (3) onto the second modulator (5), wherein the first modulator (3) has several first pixels (K1) arranged in rows and columns and the second modulator (5) has several second pixels (K2) arranged in rows and columns, wherein the first and second pixels (K1, K2) can each be switched independently into a first state in which light striking them is used to generate the image and into a second state in which light striking them is not used to generate the image, in order to modulate the light pixel-individually for generating the images, and wherein the projector further comprises a projection optic (6),the second modulator (5) maps light coming from it onto a projection surface (10) in order to project the images, and a control unit (7) which controls the two modulators (3, 5) on the basis of supplied image data (BD), wherein each second pixel (K2; K24) is assigned at least one first pixel (K1; K13, K14, K15) in such a way that the imaging optics (4) a) illuminates the second pixel (K2; K24) with light from the respective assigned first pixel (K1; K13, K14, K15) when the assigned first pixel (K1; K13, K14, K15) is switched to the first state to actively illuminate the second pixel (K2; K24), and b) does not illuminate the second pixel (K2; K24) with light from the respective assigned first pixel (K1; K13, K14, K15) when the assigned first pixel (K1; K13, K14, K15) is switched to the second state in order not to actively illuminate the second pixel (K2; K24), so that only unavoidable residual light falls on the second pixel (K2; K24),wherein the control unit (7) controls the modulators (3, 5) such that for at least one second pixel (K2; K24), which according to the image data is to represent a brightness value greater than zero and less than or equal to a predetermined first threshold, the assigned first pixel(s) (K1; K13, K14, K15) is/are switched to the second state at least during the time intervals in which the second pixel (K2; K24) is switched to the first state, so that no active illumination takes place and the second pixel (K2; K24) modulates the residual light.