Reflective Optical Sensor Light Shielding via PCB Silkscreen

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Solution Overview

Problem

The existing reflective optical sensors in electrophotographic image forming devices face challenges in preventing light leakage, which decreases the accuracy of toner density detection due to ambient light incidence, and the current methods of forming grooves on circuit boards to fit light shielding walls are time-consuming and costly.

Innovation Solution

A reflective optical sensor design that incorporates a cover element with a light shielding wall positioned to contact the circuit board surface or have a minute gap, featuring silkscreen layers on the circuit board to absorb light and enhance shielding effects, reducing light leakage and production time and costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a groove is formed on the circuit board surface to fit the light shielding wall, then light leakage prevention is improved, but production time and costs increase due to router cutting requirements

Engineering Contradiction:

Improvelight leakage preventionVSAvoidproduction time

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent replaces the expensive and time-consuming router cutting process with a cheap silkscreen layer that can be applied through standard PCB manufacturing processes. The silkscreen layer serves as an effective light shielding solution without requiring additional machining steps, thereby reducing both production time and costs while maintaining light leakage prevention.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent substitutes the mechanical router cutting system with a chemical/visual system using silkscreen printing. Instead of physically removing material to create grooves, the solution uses a printed layer that can be applied to the PCB surface, replacing mechanical manufacturing with a more efficient printing process.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If a groove is formed on the circuit board surface to fit the light shielding wall, then light leakage prevention is improved, but production costs increase due to router cutting requirements

Engineering Contradiction:

Improvelight leakage preventionVSAvoidproduction costs

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces the expensive router cutting process with a cheap silkscreen layer that can be applied through standard PCB manufacturing processes. The silkscreen layer serves as an effective light shielding solution without requiring additional machining steps, thereby reducing both production time and costs while maintaining light leakage prevention.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If the light shielding wall is positioned with a minute gap from the circuit board surface, then ease of assembly is improved, but light leakage may occur

Engineering Contradiction:

Improveassembly easeVSAvoidlight leakage prevention

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent addresses the gap issue by adding a light shielding function in a different dimension - the silkscreen layer is applied on the PCB surface plane, covering the gap area between the light shielding wall and the board. This two-dimensional coverage compensates for the three-dimensional gap, maintaining light leakage prevention while allowing assembly tolerance.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent creates a composite light shielding system combining the vertical light shielding wall structure with the horizontal silkscreen layer. This composite approach uses both structural and visual shielding methods working together to prevent light leakage even when gaps exist due to assembly tolerances.

Inventive Principle:

Principle #40Composite materials

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 design effectively prevents light leakage, ensuring accurate toner density detection and reducing production time and costs by using silkscreen layers for improved light shielding, allowing for stable and precise detection of toner patches in electrophotographic image forming devices.

Implementation Method 1

featuring silkscreen layers on the circuit board to absorb light and enhance shielding effects

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS9052659B2Reflective optical sensor and image forming device incorporating the same

Publication Date: 2015.06.09 RICOH CO LTD

AI summary

A reflective optical sensor includes a light emitting element to irradiate a target object with a light beam, a light receiving element to receive the light beam reflected by the surface of the target object, a circuit board on which the light emitting element and light receiving element are mounted, a cover element supported on the circuit board to surround the light emitting element and light receiving element, and a light shielding wall provided in the cover element to be a partition between the light emitting element and light receiving element to prevent a part of the light beam from the light emitting element from leaking to the light receiving element. A layer in a certain thickness is formed on the surface of the circuit board along either or both sides of the light shielding wall.