Speckle Displacement Detector with Dynamic Laser Control
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Solution Overview
Problem
The use of speckle patterns for precise displacement determination in image forming devices is hindered by differences in optical reflectivity between various paper types, leading to errors due to maximum and minimum reflected light values exceeding or falling below the dynamic range of image sensors.
Innovation Solution
A displacement detector system that emits variable laser light, detects the distribution of reflected light, and adjusts the laser intensity based on speckle contrast measurements to ensure that both maximum and minimum light values remain within the sensor's dynamic range, using a correction unit to set reference values for optimal image analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If speckle pattern is used for displacement determination, then measurement precision is improved, but reliability deteriorates due to paper type differences affecting reflectivity
Solution Approach 1:
The system performs preliminary measurement of the sheet's optical reflectivity properties before displacement measurement begins. By characterizing the sheet's reflectivity in advance, the system can compensate for paper type differences and ensure accurate speckle pattern analysis regardless of whether the sheet is plain, high-quality, plastic-film, or cured-resin paper.
Solution Approach 2:
The system continuously monitors the reflected light distribution and uses feedback to adjust the laser emission intensity. By comparing the actual reflected light pattern with expected patterns and adjusting the laser output accordingly, the system maintains optimal measurement conditions across different paper types and ensures reliable displacement measurement.
2Measurement precision
If laser light amount is increased to improve signal strength, then measurement precision is improved, but harmful factors increase due to light exceeding dynamic range
Solution Approach 1:
The laser emission intensity is made dynamically adjustable rather than fixed. The system continuously adapts the laser output intensity based on the measured optical reflectivity of the sheet and real-time feedback from the image sensor, ensuring that the reflected light remains within the dynamic range while maintaining sufficient signal strength for precise measurement.
Solution Approach 2:
The system changes the laser emission parameter (intensity) based on the measured optical properties of the sheet. By adjusting the laser intensity parameter according to the sheet's reflectivity characteristics, the system optimizes the reflected light signal to stay within the sensor's dynamic range while preserving measurement precision.
3Object-generated harmful factors
If laser light amount is decreased to avoid saturation, then harmful factors are reduced, but measurement precision deteriorates due to insufficient signal
Solution Approach 1:
The laser emission intensity is dynamically adjusted based on real-time feedback from measuring the reflected light pattern. This dynamic adjustment ensures that the laser output is sufficient to provide accurate speckle pattern information while preventing saturation, adapting automatically to each sheet's optical properties.
Solution Approach 2:
The system uses feedback from the image sensor to continuously monitor the reflected light levels and adjust laser emission accordingly. This feedback mechanism ensures that enough light is emitted to maintain measurement precision while preventing saturation by reducing intensity when necessary.
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 approach enables accurate displacement measurement of targets regardless of paper type, ensuring high precision and reducing errors caused by varying light reflectivity, thereby improving the control of movable members in image forming devices.
Implementation Method 1
detect a distribution of amounts of laser light reflected from the capture region
Implementation Method 2
A light emitted from a semiconductor laser is used to capture images of a target... speckle pattern appears in each image of the target... the speckle pattern reflects the fine structure of the target's surface
Implementation Method 3
use an image sensor, such as complementary metal-oxide semiconductor field effect transistors (CMOS) or a charge coupled device (CCD), to capture a continuous series of images
Data Source
AI summary
An emission unit of a displacement detector emits laser light to a range in a space in which a target moves. A detection unit detects a distribution of amounts of light reflected from a capture region in the predefined range. Based on a shift of speckle pattern indicated by a difference between the distributions of amounts of reflected light that the detection unit detects at different times, a calculation unit calculates a displacement of the target. A correction unit measures a speckle contrast from the distribution of amounts of reflected light, and based on an error between the measured value and a reference value, corrects the amount of laser light. The reference value is set to the value of a speckle contrast in a case in which the amounts of reflected light fall within the detectable range of the detection unit.