Laser Color Calibration via Temporal Segmentation
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Solution Overview
Problem
Current laser projection systems, particularly pico-projectors, face challenges in dynamic color calibration due to temperature fluctuations and positional errors of laser diodes, which require costly and cumbersome calibration methods that interfere with image projection.
Innovation Solution
A dynamic calibration method using a color calibration device with an emitted light detector, a calibration unit, and a dominant color detector to electronically compensate for positional errors, allowing for real-time adjustment of laser power and alignment without disrupting the image projection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single calibration photodiode is used to detect mixture of RGB laser beams, then cost and device complexity are reduced, but calibration precision deteriorates because the mixture power composition is not exactly known
Solution Approach 1:
The calibration process is segmented into three independent phases, one for each laser beam color (RGB). During each phase, only the corresponding laser beam is active while others are turned off, allowing the single photodiode to measure each color's power separately. This segmentation enables precise calibration of each laser beam despite using a single photodiode, resolving the contradiction between device simplicity and measurement precision.
2Adaptability or versatility
If calibration is performed during normal operation to maintain dynamic adjustment, then adaptability is improved, but image quality deteriorates due to interference with displayed image
Solution Approach 1:
The calibration process uses periodic action by alternating between calibration phases and normal image projection phases. During calibration, specific laser beams are activated in periodic intervals while others are suppressed. This periodic switching allows dynamic calibration to occur without continuously interfering with image display, maintaining both adaptability and image quality through time-multiplexed operation.
3Measurement precision
If three isolated photodiodes are used for calibration, then calibration precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
Three separate calibration measurements are merged into a single photodiode by temporally separating the activation of each laser beam. The single photodiode receives calibration signals sequentially for R, G, and B beams, combining the function of three photodiodes into one through time-multiplexing. This merging maintains calibration precision while significantly reducing device complexity and cost.
4Object-generated harmful factors
If calibration points are placed outside the image to avoid interference, then image quality is preserved, but measurement difficulty increases due to blocking requirements
Solution Approach 1:
Instead of placing calibration points outside the image area and trying to block them, the invention inverts the approach by using temporal separation to distinguish calibration signals from image content. The single photodiode measures calibration power by detecting which laser beam is active during each measurement phase, eliminating the need for spatial separation and blocking mechanisms while preserving image quality.
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
Enables reliable and cost-effective color calibration in pico-projectors by measuring power and adjusting laser diode currents, ensuring accurate color representation without the need for additional components or complex calibration procedures.
Implementation Method 1
an emitted light detector configured to measure a power of the emitted light beam
Data Source
AI summary
A color calibration device for a laser scanning apparatus includes a compensation unit configured to electronically compensate for positional errors of the three-color laser source. The compensation unit includes an emitted light detector configured to measure a power of an emitted light beam. A calibration unit coupled to the emitted light detector has a controller configured to generate a quantity correction value for the three-color laser source. A laser source control element is configured to generate a control quantity for the three-color laser source, based on the quantity correction value. A dominant color detector is configured to detect any dominant color in the light beam being projected and actuate the controller for the dominant color.