Print Head Light Calibration via Leaked Light Detection
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Solution Overview
Problem
Light-emitting-element-array type print heads face challenges in accurately calibrating light emission amounts due to variations in structure and properties among light emitting elements, leading to errors in optical path lengths and destabilization of feedback control, especially when using organic light-emitting diodes (OLEDs) as light sources.
Innovation Solution
A print head design featuring a light source panel with light emitting elements arranged in a matrix, an optical system array with compound lenses, and light receiving elements positioned in a leaked light region between the light-source-side and image-side lenses, allowing for accurate detection and correction of light emission amounts regardless of individual differences between light emitting elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If light receiving elements are disposed beside the microlens opposite a substrate on which a light emitting element array is mounted to detect leaked light for feedback control, then light emission amounts can be calibrated to compensate for variations between light emitting elements, but measurement precision deteriorates when there is variation in optical path lengths due to structural variations among light emitting elements
Solution Approach 1:
A diffusing plate is introduced as an intermediary component between the light emitting elements and the light receiving elements. This diffusing plate uniformly scatters the light before it reaches the light receiving elements, acting as a mediator that decouples the measurement from the specific optical path variations of individual light emitting elements. The diffusing plate transforms the direct light paths into multiple scattered paths, ensuring that the light amount detected by each light receiving element reflects the overall light emission status rather than being influenced by specific structural variations of individual light emitting elements.
2Object-generated harmful factors
If a light-emitting-element-array type print head is used to simultaneously expose one line of the photoreceptor surface, then noise from deflectors is eliminated and optical path length is shortened, but variations in structure and properties between light emitting elements cause uneven light emission amounts
Solution Approach 1:
The diffusing plate serves as a mediator that receives light from multiple light emitting elements with different structural variations and uniformly scatters it before reaching the photoreceptor. This intermediary component effectively averages out the light emission variations caused by manufacturing differences among individual light emitting elements, producing uniform light distribution across the exposed line without requiring precise matching of each light emitting element's properties.
3Measurement precision
If light receiving elements are positioned to detect light emitted from light emitting elements for calibration, then light emission amounts can be corrected, but detection accuracy is reduced when light amounts are insufficient at the light receiving elements
Solution Approach 1:
The diffusing plate acts as a light gathering and redistributing intermediary. It collects light from multiple light emitting elements and redistributes it uniformly to multiple light receiving elements, ensuring that each light receiving element receives sufficient light amount for accurate detection. This intermediary mechanism transforms the light distribution pattern, ensuring adequate illumination at each detection point even when individual light emitting elements have variations in emission intensity.
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 design improves the accuracy of light emission calibration by ensuring sufficient detectable light at the light receiving elements, reducing errors and maintaining stable feedback control, even with variations in optical path lengths, thereby enhancing image quality and reducing distortion.
Implementation Method 1
The light source panel includes light emitting elements arranged in a matrix
Implementation Method 2
The optical systems each include at least a light-source-side lens and an image-side lens, and focus light from the light emitting elements onto different regions of the photoreceptor
Implementation Method 3
The light receiving elements each include a light receiving surface disposed in a leaked light region and detect an amount of light incident on the light receiving surface
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3C
AI summary
A print head (202) that focuses light emitted from light emitting elements (316) arranged on a light source panel (310) in a matrix through optical systems arranged in a matching matrix onto different regions of a surface of a photoreceptor drum (24K). Each optical system is a compound lens including at least a light-source-side lens (321) and an image-side lens (323). Light receiving elements (425) each include a light receiving surface in a leaked light region (LLR) that detects light incident on the light receiving surface. The leaked light region is in a gap between the light-source-side lens and the image-side lens and is occupied by optical paths of light transmitted through the light-source-side lens but not incident on the image-side lens. A corrector (522) corrects amounts of light to be emitted from the light emitting elements based on the amounts of light detected by the light receiving elements.