Lens Array Equalizing Depth of Focus in Scanners
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Solution Overview
Problem
In image forming apparatuses, such as scanners and printers, lens arrays with one-dimensionally arranged lenses suffer from uneven depth of focus and depth of field in the main scanning and sub-scanning directions, causing image blurring and discomfort when the object or image plane deviates from the design value, and existing solutions fail to maintain resolution balance.
Innovation Solution
A lens array design featuring a first and second lens with lens elements arrayed in the main scanning direction, where the lens elements' width in the sub-scanning direction is larger than the pitch in the main scanning direction, ensuring equal emission distances in both directions, and a light blocking member is used to control light passage, maintaining focus and field depth equality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the lens array is arranged one-dimensionally with lenses in a row in the main scanning direction, then the depth of focus and depth of field in the sub-scanning direction are large, but the depth of focus and depth of field in the main scanning direction become small, causing blurring when the object or image plane deviates from the design value
Solution Approach 1:
The patent transitions from a one-dimensional lens arrangement to a two-dimensional array configuration where lenses are arranged in both main scanning direction and sub-scanning direction. This dimensional change enables simultaneous optimization of depth of focus and depth of field in both directions, resolving the contradiction between large depth in sub-scanning direction and small depth in main scanning direction.
Solution Approach 2:
The patent applies different lens arrangement characteristics to different directions: in the main scanning direction, lenses are spaced to provide appropriate depth of focus, while in the sub-scanning direction, lenses are arranged to provide large depth of focus and field. This local differentiation allows each direction to have optimized characteristics without compromising the other.
2Illumination intensity
If the diameter of lens surfaces in the sub-scanning direction is made larger than the pitch among lens elements in the main scanning direction, then light amount and MFT are improved, but the balance of resolution characteristics is lost when object or image plane deviates from design value
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: lens surface diameter in sub-scanning direction, pitch among lens elements in main scanning direction, and relative positioning between lens arrays. By changing and balancing these parameters, the patent achieves both improved light amount/MFT and maintained resolution balance, resolving the contradiction between these two characteristics.
3Device complexity
If a one-dimensional lens array is used, then the device complexity is low, but image blurring occurs when object or image plane deviates from design value due to unequal depth of focus and field in main and sub-scanning directions
Solution Approach 1:
The patent adds a second dimension to the lens array arrangement, transforming it from one-dimensional to two-dimensional. This increases device complexity but simultaneously improves reliability by providing equal depth of focus and field in both main and sub-scanning directions, preventing image blurring under various focusing conditions.
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 prevents image blurring by maintaining equal depth of focus and field in both directions, ensuring consistent image quality and reducing light unevenness, even when the object or image plane deviates, thus enhancing user experience.
Implementation Method 1
a first lens includes a plurality of lens elements arrayed in a row in a main scanning direction orthogonal to an optical axis and configured to condense, with an emission surface, light made incident on an incident surface from an object point
Implementation Method 2
a light blocking member is provided on the emission surface of the first lens, and the light blocking member blocks light made incident on the emission surface of the first lens
Data Source
AI summary
According to one embodiment, a lens array includes a first lens and a second lens. The first lens includes a plurality of lens elements arrayed in a main scanning direction and configured to condense, with an emission surface, light made incident on an incident surface from an object point. The second lens includes a plurality of lens elements arrayed in the main scanning direction. The lens elements condense again, with an emission surface, light made incident on an incident surface. When the light from the object point is made incident on the incident surface of the first lens and emitted from the emission surface of the second lens, a distance between two points of emission positions on outermost sides on the emission surface of the second lens is substantially the same in the main scanning direction and a sub-scanning direction.