Tunable Laser Projector for Depth Measurement
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Solution Overview
Problem
Existing depth measurement technologies face challenges in accurately determining object positions with low technical effort and cost, particularly due to the complexity of correspondence problems in triangulation methods and the limitations of coherent light sources such as speckle issues in laser-based systems.
Innovation Solution
A projector system utilizing a tunable laser source and diffractive optical element to generate multiple illumination patterns with adjustable properties, such as wavelength and intensity, which are controlled by a control unit to improve depth measurement accuracy and reduce speckle interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If structured light methods with stereo systems are used to determine depth images via triangulation, then measurement precision is improved, but computational demand and device complexity increase due to quadratic scaling evaluation algorithms required to solve correspondence problems
Solution Approach 1:
The patent segments the illumination pattern into multiple independently controllable light sources (laser diodes at different wavelengths) that can be activated separately. This allows the system to project simplified patterns (points, lines, planes) rather than complex structured light patterns, reducing the correspondence problem complexity from quadratic to linear scaling while maintaining depth measurement accuracy through multi-wavelength triangulation
Solution Approach 2:
The patent changes the wavelength parameter of the light source to solve correspondence problems. By using laser diodes at different wavelengths (e.g., 405nm, 450nm, 532nm, 650nm) and analyzing wavelength-dependent reflections, the system can uniquely identify corresponding features across views without requiring complex computational algorithms, thus reducing device complexity while maintaining measurement precision
2Measurement precision
If coherent light sources such as laser diodes are used for illumination, then measurement precision is improved through coherent illumination, but speckle interference increases reducing measurement reliability
Solution Approach 1:
The patent uses a composite illumination approach by combining multiple laser diodes at different wavelengths rather than using a single wavelength source. This composite multi-wavelength illumination reduces speckle interference through wavelength diversity while maintaining the coherent illumination benefits needed for precise depth measurement, thus improving measurement reliability without sacrificing precision
Solution Approach 2:
The patent employs periodic modulation of individual laser diodes at different frequencies to encode depth information. By modulating each wavelength sequentially or simultaneously at distinct frequencies and detecting the modulated reflections, the system can distinguish between different depth ranges and reduce speckle-related measurement errors, maintaining both precision and reliability
3Adaptability or versatility
If multiple laser diodes at different wavelengths are used to generate illumination patterns, then adaptability to different object conditions is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent implements a universal illumination system where a single projector unit can generate multiple illumination patterns (points, lines, planes) across multiple wavelengths using an integrated array of laser diodes. This multi-functional design allows the same hardware to adapt to different object conditions and measurement requirements without requiring separate specialized devices, improving ease of manufacture while maintaining high adaptability
Solution Approach 2:
The patent merges multiple laser diodes at different wavelengths into a single integrated illumination unit with shared optical components (lens, control electronics). By combining these elements into one compact projector rather than using separate systems for each wavelength, the patent reduces manufacturing complexity and cost while maintaining the ability to selectively activate different wavelengths for different object conditions
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
The solution enables reliable and efficient determination of object positions with reduced computational resources and cost, while minimizing speckle interference and enhancing measurement accuracy across varying object conditions.
Implementation Method 1
at least one tunable laser source
Implementation Method 2
substantially monochromatic and coherent electromagnetic radiation
Implementation Method 3
at least one diffractive optical element... arranged to produce a diffraction pattern of a known geometry
Implementation Method 4
optical sensors each having a light-sensitive area, wherein each optical sensor is designed to generate at least one sensor signal in response to an illumination of its respective light-sensitive area by a reflection light beam
Data Source
Figure 1~2B
Figure 2C~3B
Figure 4
AI summary
A detector (110) comprising a projector (122) for illuminating an object (112) with two illumination patterns (124) is disclosed. The projector (122) comprises a tunable laser source (126) and a diffractive optical element (128). The projector (122) is configured to generate the two illumination patterns (124) each comprising a plurality of illumination features by controlling a property of the tunable laser source (126). The projector (122) comprises a control unit (136) for controlling the property of the tunable laser source (126). The detector comprises a sensor element (114) having a matrix (116) of optical sensors (118) for generating sensor signals. The detector comprises an evaluation device for selecting at least one reflection feature of the reflection image and for determining a longitudinal coordinate z of the selected reflection feature by evaluating a combined signal Q from the sensor signals.