Autofocus Device with Rotating Line Image for Level Difference Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Autofocus devices struggle to perform focus detection on surfaces with level differences due to beam scattering, especially when the edge line of the level difference coincides with the direction of the line-like image, leading to difficulties in achieving accurate focus detection.
Innovation Solution
An autofocus device is designed with a cylindrical lens that forms a line-like image on the surface of the measurement target, allowing the line-like image to rotate and avoid overlap with edge lines, enabling focus detection by averaging the distance to the surface, even with level differences present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single light beam is used for focus detection, then the device structure is simple, but focus detection cannot be performed when the beam is scattered by edge lines of level differences
Solution Approach 1:
The patent divides the single light beam into multiple beams using a beam splitter. This segmentation allows the light to be distributed across multiple detection points, enabling focus detection even when some beams are scattered by edge lines of level differences on the work surface.
Solution Approach 2:
The patent uses a cylindrical lens to transform the point-like light beam into a line-like image, adding a spatial dimension to the detection. This line-like image can span across multiple height levels on the work surface, allowing focus detection to be performed by averaging distances across the line, thereby overcoming the limitation of single-point detection failing at edge lines.
2Reliability
If a line-like image is formed to perform averaging effect, then focus detection can be performed on surfaces with level differences, but the entire beam is scattered when the line-like image direction coincides with edge line direction
Solution Approach 1:
The patent introduces a rotation unit that can rotate the line-like image around the optical axis. This dynamic adjustment allows the orientation of the line-like image to be changed, enabling the system to adapt to different orientations of edge lines and level differences on the work surface, thereby preventing complete beam scattering.
Solution Approach 2:
The patent changes the orientation parameter of the line-like image by rotating it around the optical axis. By adjusting this parameter, the system can avoid alignment between the line-like image direction and edge line direction, preventing total beam scattering and maintaining focus detection capability for various surface orientations.
3Device complexity
If the line-like image direction coincides with edge line direction, then the device structure is simple, but the entire beam is scattered making focus detection difficult
Solution Approach 1:
The rotation unit enables dynamic adjustment of the line-like image orientation, allowing the system to optimize the angle between the line-like image and edge lines. This prevents complete beam scattering and maintains measurement precision without significantly complicating the device structure.
Solution Approach 2:
By changing the orientation parameter of the line-like image through rotation, the system avoids the harmful alignment condition where the line-like image direction coincides with edge line direction. This parameter adjustment prevents total beam scattering and maintains focus detection accuracy.
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
The device effectively performs focus detection on surfaces with level differences by rotating the line-like image to avoid overlap with edge lines, ensuring accurate measurement and versatility in image formation between line-like and spot-like images.
Implementation Method 1
a tube lens that forms the emitted light into parallel light
Implementation Method 2
a line-like image forming unit that forms a line-like image on a surface of the measurement target by the parallel light from the tube lens
Data Source
AI summary
An autofocus device including: an optical source; an optical unit that allows emitted light from the optical source and object light from a measurement target to pass through the same optical path, the optical unit being arranged between the optical source and the measurement target; and a detection unit that performs focus detection by using the object light passed through the optical unit. The optical unit includes: a tube lens that forms the emitted light into parallel light; an image forming unit that forms a continuous line image on a surface of the measurement target; and a rotation unit that rotates the continuous line.