Light Guide Plate Layout for High-Speed Print Defect Detection
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Solution Overview
Problem
Existing illumination devices in ink jet printing systems face challenges in accurately detecting fine streak-like defects and density unevenness due to insufficient light utilization efficiency and improper disposition of light guide plates, which affect the SN ratio and resolution in high-speed printing.
Innovation Solution
The illumination device employs a light guide plate disposed at a specific distance and angle based on its refractive indices and total reflection properties to optimize light distribution, ensuring uniform illumination and avoiding interference with other members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the transport speed of the printed matter is doubled to increase productivity, then the reading period of the image sensor must be halved, but this reduces the charge accumulation amount and lowers the SN ratio
Solution Approach 1:
The patent changes the optical parameters of the light guide plate (refractive index, thickness, distance from emission surface to illumination target area) to optimize light distribution and increase the amount of light reaching the image sensor. By setting the distance to be equal to or shorter than a specific value Lt calculated from the refractive indices and thickness, the system maintains high SN ratio even at high transport speeds.
2Measurement precision
If the amount of light received by the image sensor is doubled to maintain the SN ratio at high speed, then the illuminance must be doubled, but this increases energy consumption and heat generation
Solution Approach 1:
The patent optimizes the light guide plate parameters (refractive index, thickness, emission surface distance) to improve light utilization efficiency. By setting the distance from the emission surface to the illumination target area to be equal to or shorter than Lt, the system achieves doubled light intensity at the sensor without increasing LED power consumption, thus avoiding additional heat generation.
3Use of energy by moving object
If a light guide plate is used to reflect and guide light to increase illumination efficiency, then the light utilization efficiency is improved, but the disposition distance must be precisely controlled to avoid interference with other members
Solution Approach 1:
The patent provides specific parameter ranges for the light guide plate (refractive index, thickness, distance from emission surface) to achieve optimal light distribution. By setting the distance to be equal to or shorter than Lt, the system achieves high light utilization efficiency while maintaining sufficient clearance from other members, thus reducing the complexity of disposition control.
4Productivity
If the reading period is halved to maintain resolution at doubled transport speed, then the reading speed must be doubled, but this reduces the charge accumulation time and lowers image quality
Solution Approach 1:
The patent optimizes the light guide plate parameters to increase the amount of light reaching the image sensor. By setting the distance from the emission surface to the illumination target area to be equal to or shorter than Lt, the system compensates for the reduced charge accumulation time at high transport speeds, maintaining image quality and detection accuracy without sacrificing productivity.
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 enhances the SN ratio and resolution by doubling the light intensity reaching the image sensor, allowing for high-accuracy defect detection and correction in high-speed printing without increasing costs or heat generation.
Implementation Method 1
a light guide plate including a first surface on which the light emitted from the light source is incident, a reflecting surface that reflects the light incident from the first surface one or more times
Data Source
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AI summary
Provided are an illumination device, a light guide plate disposition determination method, and a printing system in which appropriate disposition of a light guide plate is defined depending on a condition of the light guide plate. In an illumination device including a light guide plate (32) using total reflection, in a case in which a total length of the light guide plate in a thickness direction is denoted by W, a refractive index of a periphery of the light guide plate is denoted by n1, a refractive index of the light guide plate is denoted by n2, and a maximum incidence angle with respect to a first surface corresponding to the number of reflections is denoted by θimax, the light guide plate is disposed at a position at which a distance from an emission surface (35) to an illumination target area is equal to or shorter than Lt, which is calculated by Lt = {(1/2) × (n1/n2) × W}/tanθimax.