Optical Absorption Filter Integration in Automatic Survey Instruments
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Solution Overview
Problem
The existing automatic survey instruments using dichroic prisms for wavelength division in optical systems require multiple optical absorption filters, leading to increased complexity and potential defects that degrade tracking performance due to the narrow light flux and invisible defects in these filters.
Innovation Solution
Inserting a single optical absorption filter between the dichroic prism's reflecting surfaces to absorb visible light, allowing for improved SN ratio and reduced component count, while positioning it within the prism to increase the light flux diameter and reduce defect impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple optical absorption filters are used for range-finding and tracking, then the SN ratio is improved, but the device complexity increases
Solution Approach 1:
The patent combines the functions of multiple optical absorption filters into a single filter unit. The optical absorption filter is configured to simultaneously process both range-finding light and tracking light, eliminating the need for separate filters for each function. This merging approach maintains the SN ratio improvement while reducing the total number of components in the optical system.
Solution Approach 2:
The single optical absorption filter is designed to perform multiple functions: it absorbs visible light from both range-finding light and tracking light, serving both detection paths simultaneously. This multi-functional design allows one component to replace what would traditionally require multiple specialized filters, simplifying the overall system architecture.
2Reliability
If optical absorption filters are inserted after the dichroic prism, then the SN ratio is improved, but the light flux diameter becomes narrower increasing defect impact
Solution Approach 1:
The patent changes the spatial positioning of the optical absorption filter from a post-prism location to an integrated position within the dichroic prism structure. By forming the filter at a border between prisms inside the dichroic prism assembly, the light flux diameter is maintained at a larger size, reducing the relative impact of any defects in the filter material while still achieving the necessary visible light absorption for SN ratio improvement.
3Device complexity
If a single optical absorption filter is used, then the device complexity is reduced, but the defect inspection becomes more difficult
Solution Approach 1:
The patent utilizes the optical properties of the filter material to make defects visible through color or optical property changes. The optical absorption filter is designed with specific wavelength absorption characteristics that allow defects to manifest as visible optical anomalies, enabling inspection using standard optical microscopy without requiring specialized inspection equipment.
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 simplifies the optical system, enhances tracking performance by reducing light flux defects and eliminating the need for additional inspection equipment, and allows for relaxed defect tolerance, improving component yield and SN ratio.
Implementation Method 1
an optical absorption filter that absorbs a wavelength band of visible light is inserted
Implementation Method 2
The first dichroic mirror surface 24 transmits wavelengths of 400 nm - 650 nm of the reflected light, and reflects wavelengths of 650 nm - 850 nm. The second dichroic mirror surface 25 transmits wavelengths of 720 - 850 nm of infrared light, and reflects wavelengths of 650 - 720 nm.
Implementation Method 3
Reflected light from a target passes through an objective lens 5 on an optical axis O
Data Source
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AI summary
In an automatic survey instrument that divides reflected light from a target into collimation light, range-finding light, and tracking light, a configuration of an optical absorption filter for visible light absorption to be used for SN ratio improvement is simplified, and deterioration in automatic tracking performance due to a defect inside the optical absorption filter is suppressed. Between two prisms (41, 43) defining a second reflecting surface (45) of a dichroic prism (40) through which reflected light from a target enters, an optical absorption filter (46) that absorbs a wavelength band of visible light is inserted, and the second reflecting surface (45) is formed at a border between a rear surface of the optical absorption filter (46) with respect to a light propagation direction and a surface of the prism (43) on the rear side of the optical absorption filter in the light propagation direction.