Confocal Sensor with Variable Pinhole-Diffractive Lens Distance
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Solution Overview
Problem
Conventional confocal sensors have a limited measuring range of several mm in the front-back direction, centered on a point several tens of mm from the sensor head, restricting their application in measuring distances accurately over a wider range.
Innovation Solution
A confocal sensor design that includes a light source emitting multiple wavelengths, a diffractive lens generating chromatic aberration, a pinhole for focused light, and a measuring unit that uses a non-linear relationship between wavelengths and distances to expand the measuring range by varying the distance between the pinhole and diffractive lens, allowing continuous or stepwise adjustments to achieve a wider measurement range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional confocal sensor uses a fixed optical system with a confocal lens, then the measurement resolution can achieve several nm, but the measuring range is limited to several mm in the front-back direction
Solution Approach 1:
The patent makes the optical system dynamic by enabling continuous adjustment of the distance between the pinhole and the diffractive lens. This dynamic adjustment allows the measurement range to be extended from a fixed several mm to a much wider range while maintaining the confocal measurement principle and nanometer-level resolution through wavelength analysis
2Adaptability or versatility
If the distance from the pinhole to the diffractive lens is increased to expand the measuring range, then the measuring range increases, but the optical system becomes more complex
Solution Approach 1:
The patent changes the optical parameters by using a diffractive lens instead of a conventional confocal lens. The diffractive lens generates chromatic aberration that can be utilized to expand the measuring range. By adjusting the distance parameter between the pinhole and diffractive lens, the system achieves extended measurement capability without proportionally increasing structural complexity
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
The solution enables the confocal sensor to measure distances over a significantly wider range while maintaining high accuracy, particularly in the short wavelength region, and allows for precise determination of object position within a predetermined range.
Implementation Method 1
a diffractive lens that generates a chromatic aberration with respect to the light along an optical axis direction and converges the light on an object without another intervening lens
Implementation Method 2
a diffractive lens that generates a chromatic aberration with respect to the light along an optical axis direction and converges the light on an object
Implementation Method 3
a pinhole through which reflected light passes, the reflected light being a portion of the light focused on and reflected by the object and converged by the diffractive lens
Implementation Method 4
a measuring unit that measures a distance from the diffractive lens to the object based on a wavelength of the reflected light
Data Source
AI summary
Provided is a confocal sensor having a wider measuring range. A confocal sensor 1 comprises: a light source 10 that emits light at a plurality of wavelengths; a diffractive lens 130 that causes a chromatic aberration with respect to the light along an optical axis and focuses the light onto an object 200 without another intervening lens; a pinhole 120 through which reflected light passes, the reflected light being a portion of the light that was focused onto and reflected from the object 200 and focused by the diffractive lens 130; and a measuring unit 40 that measures the distance from the diffractive lens 130 to the object 200 on the basis of a wavelength of the reflected light. A distance L2 from the pinhole 120 to the diffractive lens 130 is variable.