Optical Distance Measuring Apparatus Bias Voltage Control
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Solution Overview
Problem
Conventional optical distance measuring apparatuses using APDs face detection errors due to temperature changes and varying reflectance of measuring objects, leading to inaccurate distance measurements, especially when surfaces with different reflectances are at the same distance.
Innovation Solution
The apparatus incorporates a detected signal amplifying unit with an amplifier and/or offset removal unit, and an amplification factor control unit that includes a differentiation circuit to adjust the bias voltage and light reception level, ensuring accurate distance measurement regardless of object reflectance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If APD multiplication factor is controlled for temperature compensation, then temperature-induced detection errors are reduced, but measurement accuracy for objects with different reflectances deteriorates
Solution Approach 1:
The patent changes the parameter being compensated from multiplication factor to bias voltage. By controlling the bias voltage applied to the APD, the system compensates for temperature changes while maintaining consistent light reception levels across different reflectance values, thereby resolving the contradiction between temperature stability and measurement accuracy
Solution Approach 2:
The system implements feedback control by measuring the light reception level and adjusting the bias voltage accordingly. The light reception level detection unit monitors the actual received light intensity, and this information feeds back to the bias voltage control unit, which adjusts the bias voltage to maintain optimal reception levels despite temperature variations and reflectance differences
2Reliability
If amplifier offset is removed using a capacitor, then signal offset is reduced, but distance measurement accuracy deteriorates due to large capacitor influence on voltage comparison
Solution Approach 1:
The patent extracts and removes the capacitor from the circuit configuration. Instead of using a capacitor to remove amplifier offset, the system employs direct bias voltage control and light reception level detection, eliminating the harmful influence of the capacitor on voltage comparison while maintaining signal quality through alternative offset management methods
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 configuration enables highly accurate distance measurements by compensating for temperature changes and varying light intensities, effectively reducing detection errors and maintaining precision across different reflectance surfaces.
Implementation Method 1
The APD is a photo diode in which a phenomenon called an avalanche multiplication is used to improve light sensitivity.
Implementation Method 2
irradiating laser light on a ranging object
Implementation Method 3
receives laser light reflected from the ranging object
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
An optical distance measuring apparatus including a light source (1), a variable mirror (2) scanning the light on an object (14), a receiving device (3) receiving light from the object (14), a detected signal amplifying unit (6) detecting a light receiving signal obtained by the receiving device (3), an amplification control unit (7) detecting a set target value of light sensitivity of the receiving device (3) or sets the light sensitivity based on a light quantity of reflected light, and a distance calculation unit (11) detecting a flight time of the ranging light from a light emitting signal and calculating a distance up to the object (14), wherein in a first scan period, the amplification control unit (7) detects the set target value based on a light quantity of the reflected light, and in a second scan period, the amplification control unit (7) sets sensitivity of the receiving device (3) to the set target value and the distance calculation unit (11) calculates the distance.