Optical Scanning Device Random Number Assignment for Image Density
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Solution Overview
Problem
In optical scanning devices, the non-uniform pixel width in the main scanning direction of electrostatic latent images due to beam diameter variations and optical path distortions leads to image density unevenness, which conventional correction methods fail to adequately address, especially when pseudo random number sequences are updated unnecessarily for light emitting parts not contributing to scanning.
Innovation Solution
An optical scanning device with a light source, deflector, random number generator, selection part, and exposure control part, where pseudo random number sequences are updated only for active light emitting parts, ensuring the irregularity of target pixel positions and preventing useless updates, thus maintaining image quality by adjusting light emitting times based on specific random number update periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pseudo random number sequence assignment is updated every time when the deflection surface is switched, then the irregularity of target pixel positions is maintained, but useless updating occurs for light emitting parts not contributing to scanning
Solution Approach 1:
The patent applies local quality by differentiating the update behavior of pseudo random number sequences based on the operational state of individual light emitting parts. Active light emitting parts (those contributing to scanning) receive updated pseudo random number sequences, while inactive parts (those not contributing to scanning) maintain their existing sequences. This localized differentiation eliminates useless updates for inactive parts while preserving the irregularity requirement for active parts, thereby resolving the contradiction between maintaining pixel position irregularity and avoiding wasted updates.
2Ease of operation
If light emitting time is made uniform for each pixel, then the exposure process is simplified, but pixel width non-uniformity occurs in the main scanning direction
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the light emitting time parameter based on the specific pixel position and the selected light emitting part. Instead of using a fixed uniform light emitting time for all pixels, the system varies the light emitting time parameter to compensate for optical path distortions and beam diameter variations. This parameter adjustment enables correction of pixel width non-uniformity while maintaining the overall simplicity of the exposure process through automated control.
3Device complexity
If the same position in the main scanning direction is used for correction, then the correction process is systematic, but density unevenness occurs in the formed image
Solution Approach 1:
The patent applies asymmetry by intentionally making the correction positions asymmetric and irregular across different scan lines. Instead of applying correction to the same systematic position in the main scanning direction for all scan lines, the system varies the correction positions using pseudo random number sequences. This asymmetric positioning of correction targets prevents the formation of regular patterns that would cause density unevenness, while the correction process remains systematically controlled through the pseudo random sequence generation.
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 effectively suppresses pixel width non-uniformity in the main scanning direction, maintaining image quality by ensuring accurate and efficient light emitting time adjustments, thereby preventing unnecessary updates and maintaining image quality.
Implementation Method 1
The deflection surface reflects the light beam to scan a circumferential surface of an image carrier rotating around an axis with the light beam in a main scanning direction
Data Source
AI summary
An optical scanning device includes a light source, a deflector, a random number generator, a selection part, a random number assignment part and an exposure control part. The light source includes a plurality of light emitting parts arranged in a predetermined direction at fixed intervals in a sub-scanning direction. The random number assignment part is configured to assign a random number sequence to each light emitting part constituting a set of target light emitting parts as an index for specifying a timing at which a light emitting time of the set of target light emitting parts is set to a correction value different from a reference value and to update the assignment of the random number sequence at a random number update period. The random number update period coincides with a scanning period of each light emitting part constituting the set of target light emitting parts.