Lighting Device Condensing Body for Image Reading
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Solution Overview
Problem
Conventional image reading apparatuses using bar light sources suffer from flare light issues, especially with whitish documents, leading to reduced reading performance, while point light sources like LEDs result in illuminance ripples and insufficient light quantity, affecting image quality, especially when documents are unevenly lit or lifted from the contact glass.
Innovation Solution
A lighting device incorporating a point light source with a condensing body that directs rays within a sub-scanning direction, ensuring angles are below the critical angle of total reflection on the contact glass, and a reflection mechanism to illuminate the document from both sides, maintaining light intensity and reducing shadows and ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a bar light source is used, then the light quantity is sufficient, but flare light is generated reducing reading performance
Solution Approach 1:
The bar light source is divided into multiple point light sources arranged linearly in the main scanning direction. Each point light source emits light independently, and the total illumination is the superposition of individual point source contributions, providing sufficient light quantity while enabling precise optical control to reduce flare light
Solution Approach 2:
A condensing body is introduced as an intermediary optical element between the point light sources and the document surface. This condensing body controls the emission angles of rays, ensuring they fall within the critical angle for total reflection at the contact glass interface, thereby preventing flare light generation while maintaining adequate illumination
2Object-affected harmful factors
If point light sources are used, then flare light is reduced, but illuminance ripples occur reducing image quality
Solution Approach 1:
The emission parameters of the point light sources are precisely controlled through the condensing body, which adjusts the ray angles to be within the critical angle for total reflection. This parameter control ensures uniform illuminance distribution across the document surface while preventing flare light
Solution Approach 2:
The problem of illuminance ripples in the main scanning direction is solved by controlling light distribution in the sub-scanning direction through the condensing body's angular control, effectively using dimensional separation to address different illumination issues independently
3Illumination intensity
If point light sources are arranged close to the document surface, then light quantity is maximized, but document lifting causes large light loss
Solution Approach 1:
The condensing body is pre-configured with specific optical parameters (focal length, curvature) that define a predetermined light emission angle range. This preliminary optical design ensures that light rays are always directed within the critical angle for total reflection, compensating for document lifting without requiring active adjustment
Solution Approach 2:
The optical system is designed to dynamically adapt to document position variations through its inherent angular control characteristics. The condensing body's fixed angular control range naturally accommodates small document lifts while maintaining reliable reading performance
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 enhances reading performance by maintaining light intensity across the document surface, reducing flare light and illuminance ripples, and preventing shadows, even when documents are unevenly lit or lifted, thereby improving image quality and consistency.
Implementation Method 1
The condensing body is arranged in a direction in which angles of all rays, which pass through the condensing body, are smaller than a critical angle of total reflection on the contact glass
Data Source
AI summary
A lighting device used in an image forming apparatus includes point light sources that emits rays; and a condensing body that is arranged in a direction of the rays emitted from the point light source and that condenses the rays on a surface of a document, which is placed on a contact glass, within a reading width in a sub-scanning direction of the document. The condensing body is arranged in a direction in which angles of all rays, which pass through the condensing body, are smaller than a critical angle of total reflection on the contact glass.