Light Scanning Apparatus Timing Control Using Rotary Polygon Mirror Signals
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Solution Overview
Problem
Existing light scanning apparatuses require a separate optical sensor to detect a mark on a rotor, increasing complexity and the number of parts, which complicates the determination of lighting-up timing for the light source to prevent marking back on the recording medium.
Innovation Solution
A light scanning apparatus that determines the lighting-up timing of the light source using a first signal indicating the scan starting position and a second signal based on the rotation angle of the rotary polygon mirror, without the need for an additional optical sensor, by establishing a relationship between these signals before voltage application and using this relationship to determine the lighting-up timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate optical sensor is provided to detect the mark on the rotor, then the lighting-up timing can be determined, but the structure becomes more complex and the number of parts increases
Solution Approach 1:
The beam detector is made to serve dual functions: detecting the light beam for BD signal generation and detecting the mark on the rotor for lighting-up timing determination. This eliminates the need for a separate optical sensor and reduces device complexity while maintaining measurement precision.
Solution Approach 2:
The functions of the beam detector and the mark detection sensor are merged into a single device. The beam detector simultaneously detects both the light beam and the mark position, combining multiple detection functions into one component to simplify the overall structure.
2Reliability
If the light source is kept on during BD search, then the BD signal can be detected, but the photosensitive member is exposed causing marking back on the recording medium
Solution Approach 1:
The mark detection is performed in advance during the BD search phase to determine the lighting-up timing before actual image formation begins. This preliminary determination allows the light source to be turned off during BD search and only activated when needed, preventing marking back while ensuring reliable BD signal detection.
Solution Approach 2:
The system takes preliminary action to prevent marking back by determining the exact lighting-up timing in advance through mark detection. The light source is kept off during BD search and only turned on at the precisely determined timing, thereby preventing harmful exposure to the photosensitive member while maintaining detection reliability.
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 simplifies the structure of the light scanning apparatus, prevents marking back on the recording medium, and ensures accurate alignment of electrostatic latent images for high-quality image formation without the need for additional sensors.
Implementation Method 1
a rotary polygon mirror comprising a plurality of reflection surfaces configured to deflect the light beam emitted from the light source so that the light beam scans the photosensitive member
Implementation Method 2
a first signal generating unit configured to receive the light beam deflected by each of the plurality of reflection surfaces, and generate a first signal indicating a scan starting position of the light beam on the photosensitive member
Data Source
AI summary
An image forming apparatus includes: a photosensitive member; a process member configured to act on the photosensitive member; and a light scanning apparatus configured to emit a light beam to the photosensitive member. The light scanning apparatus includes: a light source; a rotary polygon mirror; a first signal generating unit configured to receive the light beam deflected by the rotary polygon mirror to generate a first signal indicating a scan starting position; and a second signal generating unit configured to generate a second signal based on a rotation angle of the rotary polygon mirror. A lighting-up timing of the light source for generating the first signal is determined based on a number of the second signals after a voltage for image formation is applied and a relationship between the first signal and the second signal is obtained before the voltage is applied and after the rotary polygon mirror is rotated.