Light Scanning Apparatus Timing Control for Image Forming
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Solution Overview
Problem
Existing image forming apparatuses face challenges in determining the emitting timing of the light beam for the light scanning apparatus without causing marking back on the recording medium, as they require separate detection units for the rotary polygon mirror's rotation phase, increasing complexity and cost.
Innovation Solution
An image forming apparatus that includes a light scanning apparatus with a rotary polygon mirror, a light receiving unit, and a signal generating unit to determine the emitting timing of the light beam based on phase difference information, allowing the identification of the reflection surface without marking back by controlling the light source timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate detection unit with mark and light reflection sensor is provided to detect rotary polygon mirror rotation phase, then the emitting timing of light beam can be determined accurately, but the number of parts increases and cost increases
Solution Approach 1:
The light receiving unit that normally detects the synchronous signal from the light beam deflected by the rotary polygon mirror is made to serve a dual purpose: it also detects the rotation phase of the rotary polygon mirror by receiving light from the light source before the light beam is emitted to the photosensitive member. This eliminates the need for a separate detection unit with mark and light reflection sensor, thereby reducing the number of parts and cost while maintaining accurate emitting timing determination.
Solution Approach 2:
Instead of using a separate physical detection unit with mark and sensor to detect rotation phase, the patent uses the existing light receiving unit to detect the rotation phase indirectly by measuring the phase difference between the synchronous signal and the signal from the light source. This virtual copying of the detection function avoids adding physical components.
2Reliability
If light beam is emitted to generate synchronous signal during pre-rotation processing at warm-up, then synchronization can be established, but marking back occurs on the recording medium
Solution Approach 1:
The patent performs the detection of rotation phase and determination of emitting timing before the light beam is actually emitted to the photosensitive member during pre-rotation processing. By measuring the phase difference between the synchronous signal and the light source signal in advance and storing this phase difference information, the system can accurately determine when to emit the light beam during actual image formation without causing marking back. This preliminary detection and calculation allows precise timing control without unnecessary exposure.
3Object-generated harmful factors
If allowance time period α is introduced to prevent marking back during synchronization, then the light beam timing can be adjusted, but the scanning periodic ratio effectiveness is reduced
Solution Approach 1:
The patent uses feedback from the light receiving unit to continuously monitor the phase difference between the synchronous signal and the light source signal. By measuring this phase difference and using it to precisely control the emitting timing of the light beam, the system can maintain accurate synchronization without needing to introduce a fixed allowance time period α. This feedback-based dynamic adjustment ensures that the light beam is emitted at the optimal moment, maintaining scanning periodic ratio effectiveness while preventing marking back.
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 enables accurate determination of the light beam emitting timing, preventing marking back on the recording medium and reducing the number of components needed, thus simplifying the apparatus and lowering costs.
Implementation Method 1
a light source configured to emit the light beam
Implementation Method 2
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 3
a light receiving unit arranged on a scanning route of the light beam in such a position as to receive the light beam that is emitted from the light source during a period other than a period during which the photosensitive member is scanned, and is deflected by the plurality of reflection surfaces, the light receiving unit being configured to generate a first signal for determining an emitting timing of the light beam
Data Source
AI summary
An image forming apparatus including: a photosensitive member; a charging unit; a light scanning apparatus configured to emit a light beam to scan the photosensitive member to form a latent image; and a developing unit configure to develop the latent image. The light scanning apparatus includes a light source, a rotary polygon mirror, a light receiving unit, and a signal generating unit. An incident timing when the light beam deflected by the polygon mirror enters the light receiving unit after the photosensitive member is charged by the charging unit and after a voltage is applied to a toner carrying member by the developing unit is identified based on the number of second signals generated by the signal generating unit between the first signal and the first signal generated by the light receiving unit before the photosensitive member is charged and before the voltage is applied to the toner carrying member.