Optical Stylus Imaging With Dynamic Focus and Stable Magnification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing styluses have limitations in accurately determining position and depth due to requiring physical contact or small separation from the screen, and existing optical systems face challenges with depth of field, light collection, and magnification control.
Innovation Solution
An optical system for a position determination device, such as an optical stylus, with a dynamic optical element that adjusts focal length based on working distance, using a double telecentric or object-space telecentric configuration, combined with a distance measurement sensor and electrotuneable lens, to maintain consistent magnification and focus across a range of distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional telecentric system is used, then magnification remains constant for objects at different distances, but the depth of field is limited and images are not sharp across a range of distances
Solution Approach 1:
The patent applies a dynamic optical element (electrotuneable lens) that can change its focal length in real-time based on the working distance to the position-encoded surface. This dynamic adjustment allows the system to maintain both constant magnification and sharp focus across a range of distances (10mm to 100mm), resolving the contradiction between depth of field and magnification control by making the optical system adaptive rather than static.
Solution Approach 2:
The system changes the optical parameters (focal length) of the dynamic optical element based on the measured working distance. By adjusting the focal length parameter in response to distance variations, the system maintains optimal focus and magnification control across different working distances, thereby resolving the contradiction between extended depth of field and precise magnification control.
2Measurement precision
If the diameter of the stop aperture is decreased to increase depth of field, then light collection capabilities are reduced leading to lower illumination and higher noise levels
Solution Approach 1:
Instead of using a fixed small aperture to increase depth of field, the patent employs a dynamic optical element that actively adjusts its focal length based on working distance. This dynamic approach allows the system to maintain adequate aperture size for light collection while achieving sharp focus at different distances, thereby resolving the contradiction between depth of field and illumination intensity.
3Measurement precision
If the diameter of the stop aperture is decreased, then diffraction effects are introduced which limit the maximum achievable resolution
Solution Approach 1:
The patent resolves the contradiction between depth of field and optical resolution by using a dynamic optical element that adjusts focal length rather than reducing aperture size. This approach maintains larger aperture dimensions that minimize diffraction effects while achieving extended depth of field through active focal length adjustment, thereby preserving maximum achievable resolution.
4Measurement precision
If a dynamic optical element is used to increase depth of field, then magnification control at different focal lengths becomes poor compared to conventional telecentric systems
Solution Approach 1:
The system incorporates a feedback mechanism where the working distance is measured and used to control the focal length of the dynamic optical element. This closed-loop control ensures that as the focal length changes to accommodate different working distances, the magnification is actively compensated to remain constant, thereby resolving the contradiction between extended depth of field and precise magnification control.
Solution Approach 2:
The system dynamically changes the focal length parameter of the optical element based on working distance measurements. By coordinating this parameter change with appropriate control signals to the dynamic optical element, the system maintains constant magnification across different focal lengths, resolving the contradiction between depth of field extension and magnification control.
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
Enables accurate 3D pose determination and consistent image focus from 10 mm to 100 mm distances, maintaining controlled magnification and improving image quality through real-time voltage control of the electrotuneable lens.
Implementation Method 1
The dynamic optical element is configured to be electrically actuated in order to form onto the image sensor in-focus images of any position-encoded pattern
Implementation Method 2
an object lens with a side positioned away from the stop aperture by a first distance and an image lens with a side positioned away from the stop aperture by a second distance
Data Source
AI summary
The present invention relates to an optical system (30) for a position determination device (20), in particular an optical stylus, for determination of the position of the device (20) relative to a position-encoded surface (50) having different position-encoded patterns (52). The optical system (30) comprises an image sensor (31) for capturing at least one image of any position-encoded pattern (52) of the position-encoded surface (50), one or more light sources (42) for illuminating any of the position-encoded patterns, a stop aperture (48), an object lens (32) with a side positioned away from the stop aperture by a first distance (d1) and an image lens (34) with a side positioned away from the stop aperture (48) by a second distance (d2). The optical system (30) further comprises a dynamic optical element (36) configured to be electrically actuated in order to form onto the image sensor (31) in-focus images of any position-encoded pattern (52) of the position-encoded surface (50) within working distances (WD) of the position determination device (20) comprising the optical system (30). The invention also concerns a method for determining a working distance of an optical stylus as a function of the 3D pose of the optical stylus relative to a position-encoded surface as well as a method for controlling the voltage to be applied on the dynamic optical element of the optical stylus.