Pulsed Laser Control for Scanned Beam Projectors
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Solution Overview
Problem
Digital scanned beam projectors face challenges in synchronizing the continually changing time period of virtual pixel scanning with a fixed digital control system clock, and laser-based projectors struggle with efficient low light power generation, leading to reduced brightness and image artifacts.
Innovation Solution
A laser beam scanner with a pulsed pixel controller dynamically aligns beam pulses with virtual pixels and selects waveforms to maximize power efficiency, using a dynamic edge engine and programmable delay lines to adjust pulse timing and energy duty cycles, ensuring alignment and maintaining sufficient pixel energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant sample frequency DACs are used with digital upsampling, then synchronization with changing virtual pixel frequency is achieved, but bus transaction power cost increases significantly
Solution Approach 1:
The patent applies periodic action by using pulsed laser modulation synchronized to the virtual pixel frequency. Instead of continuous high-rate DAC sampling, the system uses periodic pulse generation triggered by pixel timing signals, where each pulse corresponds to a virtual pixel. This reduces the effective sampling rate while maintaining synchronization accuracy, thereby reducing bus transaction power cost significantly.
2Use of energy by moving object
If laser optical power is modulated between off and high power, then power efficiency increases, but maximum brightness of video content is reduced
Solution Approach 1:
The patent applies dynamics by implementing adaptive pulse width modulation where the pulse width dynamically adjusts based on the required optical power for each pixel. The system selects from multiple waveform templates with different pulse widths and amplitudes, allowing the laser to operate at high efficiency (pulsed mode) while maintaining the ability to achieve maximum brightness when needed. This dynamic adjustment resolves the contradiction between efficiency and maximum brightness.
3Use of energy by moving object
If only one DAC sample is active per pixel period, then laser efficiency increases, but brightness is reduced and significant video artifacts occur
Solution Approach 1:
The patent applies parameter changes by using multiple waveform templates with varying pulse width and amplitude parameters. Instead of using a single fixed waveform, the system selects from a library of waveforms with different characteristics (different pulse widths, amplitudes, and shapes) to match the required optical power level for each pixel. This allows the system to maintain high laser efficiency while avoiding video artifacts by selecting the appropriate waveform parameter set for each pixel's brightness requirement.
4Device complexity
If beam pulses are not dynamically aligned with virtual pixels, then system complexity is reduced, but image sharpness and positioning accuracy deteriorate
Solution Approach 1:
The patent applies feedback by implementing a pixel timing signal generation system that monitors and tracks the actual scanner position and velocity. The system uses feedback from the scanner's motion to dynamically adjust the pulse timing and width, ensuring that beam pulses are precisely aligned with virtual pixels despite changes in scanner velocity. This feedback mechanism maintains positioning accuracy without requiring overly complex predetermined timing schemes.
Data Source
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AI summary
Briefly, in accordance with one or more embodiments, a scanned beam projector comprises a laser diode (114) to emit a beam, a scanning engine (110) to scan the beam on a surface to project an image comprising virtual pixels on the surface, a digital-to-analog converter (DAC) coupled to the laser diode to cause the laser diode to emit the beam in response to a digital video signal provided to the DAC, and a pulsed pixel controller to provide the digital video signal to the DAC, the pulsed pixel controller to align the digital video signal provided to the DAC with the virtual pixels of the image, and to select an optimal waveform to be generated by the laser diode for each virtual pixel.