Wearable Display Laser Power Calibration With Shared Light Sensor
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Solution Overview
Problem
Wearable display devices face challenges in achieving consistent light efficiency due to variations in light emitter performance, such as laser diodes, which affect the quality of augmented reality imaging, and existing calibration methods are inaccurate, leading to errors in power monitoring.
Innovation Solution
Incorporating a calibration light sensor to receive a portion of the light from the emitter structure, allowing for real-time calibration of monitor photodiodes by sequentially pulsing each light source, ensuring accurate power monitoring and adjustment of light output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single calibration light sensor is used to calibrate multiple light sources, then device complexity is reduced, but measurement precision deteriorates due to sequential calibration requirements
Solution Approach 1:
A single calibration light sensor is designed to serve multiple light sources (laser diodes) within the imaging unit. The sensor is positioned to receive light from different emitters sequentially, enabling one sensor to perform calibration functions for multiple sources, thereby reducing the number of sensors needed while maintaining calibration capability across all light sources.
Solution Approach 2:
The calibration process employs sequential pulsing of light sources, where each light source is activated in turn to allow the single calibration sensor to measure and calibrate that specific emitter. This periodic activation pattern enables the sensor to systematically calibrate multiple sources over time, achieving comprehensive calibration coverage without requiring simultaneous measurement of all sources.
2Device complexity
If light efficiency variations among light emitters are not corrected, then device complexity remains low, but imaging quality deteriorates due to inconsistent light output
Solution Approach 1:
The calibration system uses the calibration light sensor to measure actual light output from each emitter and feeds this information back to the control system. Based on this feedback, individual calibration factors are determined for each light source, allowing the system to compensate for manufacturing variations and achieve consistent light output across all emitters during operation.
Solution Approach 2:
The system adjusts operational parameters (such as drive current or pulse duration) of each light source based on measured light efficiency variations. By changing these parameters individually for each emitter, the system compensates for manufacturing tolerances and material variances, ensuring uniform light output performance across all light sources in the imaging unit.
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 method enhances the accuracy of light output calibration, improving the consistency and quality of augmented reality imaging by correcting variations in light emitter performance, thereby enhancing the overall display performance of wearable devices.
Implementation Method 1
a calibration light sensor for receiving a portion of the light from one of the one or more optical elements
Implementation Method 2
Sensor data from the calibration light sensor, which is representative of the power emitted from the front facet of the laser diode, may be used to calibrate the monitor photodiodes during a calibration process
Data Source
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AI summary
A wearable display includes left and right display lens systems each having imaging units configured for augmented reality imaging. The imaging units include an emitter structure, one or more optical elements, a display optic, an electrically alterable scanning optical element and a calibration light sensor. The emitter structure has one or more light sources configured to emit light. The optical elements direct the light along a light path in the imaging unit. The scanning optical element receives the light from the optical elements and directs it to the display optic. The scanning optical element scans in one or more dimensions to direct the light through an imaging optic that directs the light into the display optic. The calibration light sensor is located at a point along the light path between the emitter structure and the scanning optical element and receives a portion of light from one of the optical elements.