Endoscope Optical Path Splitting for Wide Depth of Field
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Solution Overview
Problem
Endoscope systems with high pixel image pickup elements face a narrow depth of field due to small pixel pitch, limiting their ability to capture clear images over a wide range without excessive focus differences or aberrations.
Innovation Solution
An endoscope system that splits an object image into two optical images of different focus using an optical path splitting unit and combines them using an image synthesis processing section, with a first lens having negative refractive power, to generate a composite image with a wider depth of field, while satisfying specific conditional expressions to maintain appropriate focus and reduce aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of pixels of the image pickup element is increased to improve image quality, then the pixel pitch becomes smaller, but the depth of field becomes narrow
Solution Approach 1:
The object image is segmented into two optical images with different focus positions using an optical path splitting unit. This allows the system to capture both near and far objects simultaneously, effectively widening the depth of field while maintaining high pixel density for image quality
Solution Approach 2:
The patent introduces a new dimension by creating two separate optical paths with different focal points. By capturing images at different focus positions and combining them, the system extends the depth of field beyond what a single image pickup element can achieve
2Measurement precision
If the pixel pitch is made small to increase the number of pixels, then image quality improves, but the permissible circle of confusion becomes small, further narrowing the depth of field
Solution Approach 1:
By segmenting the imaging into two separate optical paths with different focus positions, each path can be optimized for its specific focal range. This segmentation allows the system to maintain small pixel pitch for high quality while compensating for the reduced permissible circle of confusion through multi-focus capture
3Length of moving object
If images are split and combined to widen depth of field, then depth of field increases, but the device complexity increases
Solution Approach 1:
A single image pickup element performs multiple functions by capturing two different optical images through the optical path splitting unit. This multi-functionality approach widens the depth of field without requiring multiple separate image pickup elements, thereby controlling device complexity
4Ease of manufacture
If a single image pickup element is used to reduce cost, then manufacturing cost decreases, but the depth of field remains narrow
Solution Approach 1:
The optical path splitting unit segments the light from a single image pickup element into two separate optical paths with different focus positions. This segmentation enables one image pickup element to effectively capture a wider depth of field, maintaining cost effectiveness while improving depth of field performance
Solution Approach 2:
The optical path splitting unit acts as an intermediary component that enables a single image pickup element to achieve wide depth of field by creating two separate optical paths. This intermediary approach provides a cost-effective solution compared to using multiple image pickup elements
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 widens the depth of field, allowing for high-quality imaging in both normal and close observation modes without degrading resolving power, even with larger pixel image pickup elements, and reduces manufacturing costs by using a single image pickup element.
Implementation Method 1
an optical path splitting unit which splits an object image acquired by the objective optical system into two optical images of a different focus
Implementation Method 2
the objective optical system includes a first lens having a negative refractive power which is nearest to object
Data Source
AI summary
An endoscope system includes an objective optical system OBL, an optical path splitting unit which splits an object image acquired by the objective optical system OBL into two optical images having a different focus, an image pickup element which acquires the optical images, and an image synthesis processing section which selects in a predetermined area an image with a relatively high contrast from the two optical images acquired, and generates a composite image, wherein the objective optical system OBL includes a first lens L1 having a negative refractive power which is nearest to object, and the endoscope system satisfies the following conditional expressions (1) and (2).3<D_diff/im_pitch≤100 (1)0.005<D_diff/R1_r<1.0 (2)where,D_diff denotes an air conversion length of a difference in length of optical paths of the two optical images,im_pitch denotes a pixel pitch of the image pickup element, andR1_r denotes a radius of curvature at an image-side surface of the first lens having a negative refractive power.