Light Beam Detection Circuit Using Single Sensor and Reference Signal

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Solution Overview

Problem

Conventional light beam detection systems for electrophotographic image forming apparatuses require multiple optical sensors, leading to increased costs and potential displacement of the starting position for image writing due to variations in light beam intensity caused by ambient conditions.

Innovation Solution

A light beam detection circuit utilizing a single optical sensor to generate a detection signal, a reference signal proportional to the light-emission control signal, and a synchronizing signal generation section to determine the scanning starting position, which simplifies the circuit configuration and reduces costs by eliminating the need for additional sensors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If two optical sensors are used to detect light beam passage timing precisely, then measurement precision is improved, but device complexity and cost increase

Engineering Contradiction:

Improvelight beam passage timing detection precisionVSAvoidnumber of optical sensors

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent uses a single optical sensor to detect the light beam, and creates a reference signal that copies the light amount control signal. This reference signal serves as a virtual duplicate of the expected detection signal, allowing precise timing detection without needing a second physical sensor. The comparator compares the actual detection signal with this reference copy to generate accurate synchronizing signals.

Inventive Principle:

Principle #26Copying

2Adaptability or versatility

If light amount of light beam is changed according to ambient conditions, then adaptability is improved, but manufacturing precision of starting position deteriorates

Engineering Contradiction:

Improveadaptation to ambient temperature and humidityVSAvoidstarting position for image writing

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent implements a feedback mechanism where the light amount control signal (which adjusts for ambient conditions) is fed back to create a reference signal. This reference signal is then used by the comparator to adjust the detection threshold dynamically. When ambient conditions change and require light amount adjustment, the reference signal automatically adapts, keeping the detection timing consistent and preventing starting position displacement.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the threshold parameter dynamically based on light amount control signals. Instead of using a fixed threshold, the comparator uses a variable reference signal that changes in proportion to the light amount control signal. This allows the detection system to adapt to changing ambient conditions (temperature, humidity) while maintaining consistent detection timing, as the threshold parameter adjusts alongside the light beam intensity.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If a single optical sensor is used, then device complexity is reduced, but measurement precision deteriorates due to inability to compare waveforms

Engineering Contradiction:

Improvenumber of optical sensorsVSAvoidlight beam passage timing detection precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent introduces a reference signal as an intermediary element that mediates between the single optical sensor output and the detection decision. This reference signal acts as a virtual second sensor, providing a comparison reference without requiring physical duplication of the optical sensor. The comparator uses this intermediary reference signal to achieve waveform comparison functionality with a single physical sensor.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Enables precise detection of light beam passage timing while maintaining cost-effectiveness by using a single optical sensor, preventing displacement of the starting position for image writing even with changes in light beam intensity.

Implementation Method 1

a detection signal generation section (34) which receives a light beam for scanning of a scanning target with one optical sensor (10), and generates a detection signal corresponding to an amount of received light

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS9170521B2Light beam detection circuit, light beam scan unit and image forming apparatus to detect light beam that changes light-amount thereof

Publication Date: 2015.10.27 SHARP KK

AI summary

In order to detect a passage timing of a light beam and to suppress cost, a light beam detection circuit (2) includes a detection signal generation section (34) configured to receive a light beam for scanning of a scanning target (101A) with one optical sensor (10), and generate a detection signal corresponding to an amount of received light; a reference signal output section (44) configured to output a reference signal that is in proportion to a light-amount control signal of a light-emission element (LD1) that emits the light beam; and a synchronizing signal generation section (35) configured to compare a detection signal generated by the detection signal generation section (34) with a reference signal output from the reference signal output section (44) to generate a synchronizing signal to determine a position to start scanning of the scanning target (101A) with the light beam.