Exposure Apparatus Light Amount Unevenness Compensation
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Solution Overview
Problem
In solid-state exposure type exposure apparatuses using organic EL elements, light amount unevenness leads to prominent density unevenness in print images, degrading image quality due to the distinct temperature-light amount characteristics of organic EL elements compared to other light-emitting elements.
Innovation Solution
The exposure apparatus includes multiple light-emitting chips with light-emitting portions arranged along the axial direction of a photosensitive member. A control unit outputs image data to these chips, adjusting the driving currents based on the number of bits indicating a specific value in the image data, thereby controlling the light emission to compensate for temperature-induced light amount variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If organic EL elements are used in solid-state exposure type exposure apparatus, then downsizing, enhancing quietness, and cost reduction are easier, but light amount is small requiring longer exposure time which integrates light amount unevenness and causes prominent density unevenness in print images
Solution Approach 1:
The patent adjusts the driving current parameters for each light-emitting element based on pre-measured light amount characteristics. By changing the electrical parameter (driving current) according to the specific light output characteristics of each element, the system compensates for light amount unevenness and prevents density unevenness in the final print image.
Solution Approach 2:
The patent performs preliminary measurement of light amount for each light-emitting element during manufacturing, stores these characteristics in advance, and uses this pre-acquired data to adjust driving currents during operation. This preliminary action allows the system to proactively compensate for light amount variations before they manifest as image quality defects.
2Illumination intensity
If driving current is increased to compensate for light amount reduction in light-emitting thyristor, then light amount is maintained, but temperature-light amount characteristic differs from organic EL element causing compensation inaccuracy
Solution Approach 1:
The patent measures and utilizes the specific temperature-light amount characteristics of organic EL elements to determine appropriate driving current adjustments. By basing compensation on the actual characteristics of the used light-emitting elements rather than generic models, the system achieves accurate compensation that accounts for the unique thermal and optical properties of organic EL materials.
3Duration of action of moving object
If light amount unevenness is present in organic EL element array, then deviation from target light amount is integrated over exposure time, but longer exposure time is required due to small light output
Solution Approach 1:
The patent adjusts driving current parameters for each light-emitting element to compensate for light amount variations before exposure. By pre-balancing the light output through electrical parameter adjustment, the system prevents the integration of light amount deviations during the necessarily longer exposure time, thereby maintaining image quality.
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 effectively suppresses light amount unevenness between light-emitting chips due to temperature changes, thereby preventing image quality degradation and ensuring consistent print density.
Implementation Method 1
a light-emitting element array 201 including a plurality of organic EL elements 602
Data Source
AI summary
An exposure apparatus for exposing a photosensitive member includes: a first chip that includes a plurality of first light-emitting portions arranged along an axial direction of the photosensitive member; a second chip, arranged at a different position from the first chip in the axial direction, that includes a plurality of second light-emitting portions arranged along the axial direction; and a control unit configured to output image data that is a set of binary bits each indicating a first or second value. A first part and a second part of the image data are output to the first and second chips, respectively. The control unit is configured to control a driving current supplied in each of the first and second chips based on a counted number of bits indicating the first value in the corresponding part of the image data.