SPAD Pixel Array for Laser Rangefinder Optical Isolation
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Solution Overview
Problem
Existing laser rangefinders face challenges in optical isolation between transmission and reception paths, requiring precise alignment and high temporal resolution, which complicates the design and increases costs due to the need for sensitive signal processing and small detector fields of view.
Innovation Solution
A laser distance measurement device utilizing a large-area, time-resolving optical sensor with separate optical systems for transmission and reception, featuring a detection surface with multiple SPAD pixels that can be selectively activated, allowing for improved optical separation and reduced alignment requirements, and enabling better signal-to-noise ratios through adaptable pixel configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a small detector field of view is used to improve optical isolation between transmission and reception paths, then optical isolation is improved, but the alignment requirements become more stringent and the device complexity increases
Solution Approach 1:
The patent divides the detector into multiple independently controllable pixel elements. By selectively activating only those pixels within the narrow field of view that correspond to the transmission path, the system achieves good optical isolation while using a larger overall detector array, thereby reducing alignment stringency.
Solution Approach 2:
The patent employs dynamic pixel selection where different pixel groups are activated based on the current scanning position and required field of view. This dynamic activation allows the system to maintain optimal optical isolation for each measurement position while utilizing the flexibility of a large-area detector array.
2Ease of manufacture
If a large-area detector is used to reduce alignment requirements, then ease of manufacture is improved, but the signal-to-noise ratio deteriorates due to increased detector field of view
Solution Approach 1:
The patent applies local quality by activating only specific pixel regions of the large-area detector that correspond to the relevant measurement field of view. This selective activation ensures that only the necessary detector area contributes to the signal, maintaining high signal-to-noise ratio while benefiting from the manufacturing ease of a large-area detector.
Solution Approach 2:
The patent uses a large-area detector array (excessive action) but only activates a partial portion of it for each measurement. This approach provides alignment tolerance benefits from the large area while maintaining measurement precision by limiting active pixels to those necessary for the current field of view.
3Measurement precision
If pulse propagation time measurement method is used to achieve accurate distance measurement, then measurement precision is improved, but the temporal resolution requirement for signal processing electronics increases
Solution Approach 1:
The patent employs periodic modulation of the laser source and synchronous detection at the pixel level. By using periodic action with known frequency, the system achieves accurate distance measurement through phase or time-of-flight measurement while reducing the temporal resolution burden on electronics through the regular, predictable signal pattern.
Solution Approach 2:
The patent replaces high-speed electronic timing systems with a combination of periodic optical modulation and pixel-level detection. This substitution reduces the temporal resolution requirements for signal processing electronics while maintaining measurement precision through the optical domain's inherent time-resolution capabilities.
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 solution reduces the complexity and cost of signal processing, enhances optical isolation, and improves the dynamic range and signal-to-noise ratio, allowing for more accurate and efficient distance measurements with reduced alignment tolerances and increased flexibility in detector design.
Implementation Method 1
each pixel having at least one SPAD (single photon avalanche photodiode)
Implementation Method 2
each pixel having at least one SPAD (single photon avalanche photodiode)
Implementation Method 3
distance of an individual object point is measured by time-of-flight measurement
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
The invention relates to a measuring apparatus (10), in particular a handheld measuring apparatus, for measuring a target object in a multidimensional manner, wherein the distance to individual object points of the target object is sequentially measured, in particular using a phase-measuring system, which apparatus has at least: a transmitting device (12) for emitting optical measuring radiation (13) towards the target object (15); a receiving device (14) having a detection area (110) for detecting optical measuring radiation (16) returning from the target object (15); a scanning system for deflecting the optical measuring radiation, and an evaluation device (36) for determining measured distance values. The invention proposes that the detection area (110) of the receiving device has a plurality of pixels (111), wherein each pixel (111) has at least one SPAD (101), and wherein each of the plurality of pixels (111) is connected to the evaluation device (36). The invention also relates to a measuring device having such a measuring apparatus.