Ophthalmic Examination Head Alignment Using a Tilted Motion Axis
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Solution Overview
Problem
Existing ophthalmic devices face challenges in accurately aligning the examination head with the subject eye without bringing it close to the nose, affecting examination accuracy and image quality due to the short operating distance caused by large objective lenses.
Innovation Solution
The ophthalmic device employs a displacement mechanism that displaces the examination head along an axis of tilt, incorporating movement and rotation mechanisms to position the head without proximity to the nose, using a drive controlling unit to manage these movements based on alignment detection and manual control modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a large objective lens is used in the examination head to support wide-angle photographing, then the photographing capability is improved, but the operating distance becomes shorter causing the examination head to come close to the subject's nose
Solution Approach 1:
The patent introduces a tilt angle dimension (theta) to the examination head positioning. Instead of only moving the examination head along the optical axis (one dimension), the head is tilted at an angle theta relative to the optical axis, creating a two-dimensional positioning approach. This allows the examination head to maintain a larger operating distance while still capturing the subject eye effectively, resolving the contradiction between large lens size and short operating distance.
2Measurement precision
If the examination head is brought close to the subject's nose to achieve proper alignment, then the alignment accuracy is improved, but the comfort and safety for the subject deteriorates
Solution Approach 1:
By introducing the tilt angle theta as an additional degree of freedom, the system can achieve proper alignment without requiring the examination head to be positioned close to the subject's nose. The tilted positioning creates a geometric relationship where the examination head can be farther away while maintaining alignment accuracy, thus improving subject comfort and safety.
Solution Approach 2:
The patent changes the positioning parameters from only translational movement along the optical axis to include rotational tilt angle theta. This parameter change allows the examination head to be positioned at a safer distance while maintaining alignment accuracy through angular adjustment rather than pure translational movement.
3Object-affected harmful factors
If the examination head is positioned far from the subject's nose to ensure safety, then subject comfort is improved, but alignment accuracy deteriorates
Solution Approach 1:
The tilt angle theta provides an additional dimensional parameter that decouples the relationship between distance and alignment accuracy. By adjusting the tilt angle, the system can maintain accurate alignment even when the examination head is positioned farther from the subject's nose, thus preserving both subject comfort and alignment accuracy.
Data Source
AI summary
The ophthalmic device includes an examination head configured to examine on a subject eye and a displacement mechanism (an XZ movement mechanism, a Y movement mechanism, a swing rotation mechanism, and a tilt rotation mechanism) configured to displace the examination head with respect to the subject eye. The displacement mechanism displaces the examination head to an examination position for the subject eye along an axis of tilt. Here, the axis of tilt is an axis obtained by tilting, around the center of the subject eye, a reference axis that extends along the eye direction of the subject eye in parallel with a front-back direction serving as an operating distance direction (Z-direction) of the examination head, outward away from a subject's nose.