LED PWM Control for Binary SLM Intensity Resolution
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Solution Overview
Problem
Existing video display systems using binary spatial light modulators (SLMs) face limitations in intensity resolution due to mechanical constraints, leading to reduced image quality and the need for costly redesigns when using techniques like neutral density filters or dynamic aperture technology.
Innovation Solution
The implementation of a rapid switching light source, such as LEDs, which allows for increased bit-depth by varying display times and light intensities, enabling existing binary SLM designs to produce a wider range of light intensities with minimal modification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If neutral density filter or dynamic aperture technology is used to reduce minimum light amount, then bit-depth is improved, but system complexity and cost increase significantly
Solution Approach 1:
The patent replaces mechanical light modulation systems (neutral density filters, dynamic apertures) with an electrical control system. By using PWM to control the timing of light emission from the source, the system achieves variable intensity resolution through electronic timing control rather than mechanical intervention, thereby reducing system complexity while maintaining or improving bit-depth.
Solution Approach 2:
The patent changes the control parameter from mechanical position/filter density to temporal duration. By varying the on-time of the light source within each frame period, the system achieves different intensity levels. This parameter change from spatial/mechanical control to temporal/electronic control simplifies the system architecture while enabling higher intensity resolution.
2Measurement precision
If neutral density filter is used to modulate light, then minimum light amount is reduced, but overall system brightness is reduced due to light loss
Solution Approach 1:
The patent employs periodic pulsed emission of light from the source, where the light is emitted in controlled time intervals (PWM cycles) rather than continuously. By adjusting the duty cycle of these periodic pulses, the system achieves variable intensity levels without mechanical attenuation, thereby maintaining high overall brightness while enabling fine intensity resolution through temporal modulation.
3Ease of operation
If mechanical techniques are used to modulate light, then light intensity can be controlled, but physical limits prevent achieving desired minimum light levels
Solution Approach 1:
The patent replaces mechanical light modulation techniques with electronic PWM control of the light source timing. This substitution removes the physical limits inherent in mechanical systems (such as minimum aperture size or filter density steps) and enables much finer control of minimum light levels through precise temporal control, achieving higher intensity resolution without mechanical constraints.
4Measurement precision
If binary SLM switching time is reduced to increase bit-depth, then intensity resolution is improved, but mechanical constraints prevent further reduction
Solution Approach 1:
Instead of attempting to reduce the switching speed of the mechanical binary SLM (which has physical limits), the patent inverts the approach by controlling the light source timing. The binary SLM operates at its natural switching speed, while the PWM-controlled light source emits light only during the brief periods when the SLM is in the desired state. This inversion transfers the timing control burden from the mechanical SLM to the electronic light source, achieving high bit-depth without compromising SLM switching performance.
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 enhances image quality by increasing bit-depth without the need for significant redesign, allowing for lower-cost, more reliable light modulators and improved manufacturing yields.
Implementation Method 1
The implementation of a rapid switching light source, such as LEDs
Data Source
AI summary
A method for increasing intensity resolution (bit-depth) using LED illumination. A preferred embodiment comprises determining a display time for a bit to be displayed on a display system, with the display time being based upon a weighting of the bit. If the display time is less than a minimum display time of the display system, then a light modulator and light source modulation are to be used to display the bit. If the display time is equal to or greater than the minimum display time, then a light modulator is to be used to display the bit. The use of a light source that can switch at a faster rate than the light modulator can change states and/or a light source that can produce light at multiple intensities can permit the display of less light and thereby increase the bit-depth of the display system.