Optical Displacement Sensor Exposure Control for Reflectance Variations
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Solution Overview
Problem
Conventional optical displacement sensors face measurement errors due to dynamic changes in light reflecting levels from objects, particularly when objects with different reflectance are measured, leading to underexposure or overexposure and inaccurate distance measurements.
Innovation Solution
An optical displacement sensor with an imager having multiple pixel blocks, each with a light receiving level upper limit, comparators to monitor and stop exposure, and a logic circuit to associate exposure time with measurement distance, ensuring accurate distance measurement by preventing measurement errors from light reflecting level changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional automatic exposure function is used with average brightness calculation, then exposure time can be adjusted based on overall image brightness, but measurement accuracy deteriorates when light reflecting level changes dynamically causing temporary underexposure or overexposure
Solution Approach 1:
The patent applies preliminary action by stopping exposure in advance when the light receiving level reaches a predetermined upper limit value, preventing overexposure before it occurs. This is achieved by continuously monitoring the light receiving level during exposure and immediately terminating exposure when the threshold is reached, ensuring that pixel saturation is avoided and measurement accuracy is maintained even when light reflecting levels change dynamically
2Measurement precision
If exposure is stopped when peak light receiving level is detected, then overexposure and saturation are avoided, but measurement error increases when light reflecting level changes dramatically
Solution Approach 1:
The patent implements feedback by continuously monitoring the light receiving level of pixels during exposure and using this real-time information to control the exposure termination. The monitoring unit provides continuous feedback on light receiving levels, and when the upper limit value is reached, this feedback triggers immediate exposure stopping, ensuring both precision in exposure control and reliability in measurement even under varying light conditions
Solution Approach 2:
The patent applies dynamics by making the exposure time variable and adaptive rather than fixed. The exposure duration dynamically adjusts based on the actual light receiving conditions, extending exposure longer for low reflectance objects and automatically terminating earlier for high reflectance objects. This dynamic adjustment ensures optimal measurement reliability across different light reflecting levels while maintaining precision through real-time monitoring
3Ease of operation
If fixed exposure time is used for all objects, then device operation is simple, but measurement accuracy deteriorates when objects with different reflectance are measured
Solution Approach 1:
The patent applies dynamics by implementing variable exposure time that automatically adapts to different object reflectance levels. The system dynamically determines exposure duration based on real-time light receiving level monitoring, allowing simple operation without manual intervention while achieving high measurement precision across diverse objects with varying reflectance properties
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 sensor provides accurate distance measurements without measurement errors, even with dynamic light reflecting levels, by monitoring and controlling exposure to prevent overexposure or underexposure, and allows for quick response to changes in object reflectance.
Implementation Method 1
an imager (1) having a plurality of pixels (5) for receiving light from an object (M)
Data Source
AI summary
The present invention includes an imager 1 having an automatic exposure stopping function, which are implemented therein, and includes an exposure time measuring unit 24 to measure the exposure time from the start of exposure to the stopping of exposure in the imager 1, a measurement distance calculating unit 21 to calculate the measurement distance to an object M on the basis of a displacement of the light receiving position in the imager 1, and a data output/storage unit 25 to output and/or store, as data related with acquisition of a distance actual value, which is an actual distance to the object, in a condition in which the measured exposure time and the measurement distance calculated with this exposure time are associated with each other.