f-theta Optical System for Retinal Image Size Consistency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional visual field testing devices using planar display devices result in varying image sizes on the retina due to the tan θ curve relationship between incident angle and image height, affecting the accuracy of visual field diagnosis, especially at peripheral positions where the image appears smaller than at the center.
Innovation Solution
A vision testing device with a display optical system configured as a f - θ optical system, utilizing a series of lenses including an aspheric lens closest to the eyeball, ensures a proportional relationship between incident angle and image height, maintaining consistent image size on the retina regardless of display position, and is designed for use as a head mount type display device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a planar display device is used to display visual targets, then the device structure is simplified compared to dome type screens, but the image size on the retina varies depending on the display position due to the tan θ curve relationship
Solution Approach 1:
The patent transforms the optical system parameters by replacing the conventional lens with an f-θ optical system that establishes a linear relationship between incident angle and image height. This parameter change in the optical characteristics compensates for the tan θ curve effect, ensuring that visual targets of the same size on the display surface produce images of consistent size on the retina regardless of their position.
2Illumination intensity
If visual targets are displayed at peripheral positions on the display surface, then the viewing angle is expanded to cover the entire visual field, but the image size on the retina becomes smaller due to the tan θ curve
Solution Approach 1:
The f-θ optical system changes the optical parameters to create a linear mapping between the angular position of incoming light and the image height on the display surface. This ensures that visual targets at peripheral positions are magnified appropriately so that their retinal images maintain the same size as central targets, while still covering the required wide viewing angle for comprehensive visual field testing.
3Illumination intensity
If the visual target size is increased to ensure sufficient viewing angle for normal vision diagnosis, then the viewing angle is improved, but the variation in perceived size across different display positions is amplified
Solution Approach 1:
The patent applies parameter changes to the optical system by implementing an f-θ relationship that decouples the viewing angle from the image size variation problem. The optical system is designed so that the image height is directly proportional to the incident angle (Y = f·θ), which maintains consistent magnification across the entire field of view, allowing large visual targets to be displayed without amplifying size variation at different positions.
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 configuration allows for a consistent visual target size perception across the retina, enhancing the accuracy of visual field testing and maintaining a wide viewing angle, preventing pincushion deformation and ensuring precise diagnosis.
Implementation Method 1
a display optical system provided on an optical axis between an eyeball position where an eyeball of the testee is placed and a display surface of the planar display device, wherein the display optical system is configured by a f - θ optical system in which a relationship between an incident angle of a principal ray when the testee views a visual target from the eyeball position through the display optical system and an image height on a display surface of the planar display device is proportional
Data Source
Figure 1
Figure 2
Figure 3
AI summary
When displaying visual targets on a planar display element and performing vision examinations, the size of the visual target visible to the subject changes according to the position at which the visual target is displayed. This vision examination device 1 comprises: a planar display element 12 that displays visual targets to a subject of a vision examination; and a display optical system 11 (19, 20, 21) provided upon an optical axis 18 between an eyeball position at which an eyeball 8 of the subject is arranged and a display screen 12a of the planar display element 12. The display optical system 11 comprises an f-θ optical system having a proportional relationship between an image height on the display screen 12a of the planar display element 12 and the angle of incidence θ for the main light rays when the subject views the visual target through the display optical system 11 from the eyeball position.