Laser Beam Shaping in Biometric Optics to Prevent Reflection Interference
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Solution Overview
Problem
Biological information measurement apparatuses using laser light suffer from interference light generated by front and back surface reflections, which decreases measurement accuracy.
Innovation Solution
A biological information measurement apparatus with a light transmission member that separates laser light into a first and second beam, using a first light receiving unit to detect the first beam and a second light receiving unit to detect scattered light, with a differential circuit to generate an output signal, and a control apparatus to analyze biological information, ensuring the first diameter of the laser light along a parallel axis is smaller than the second diameter along an orthogonal axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light transmission member is used to separate laser light into first and second beams, then the laser light can be effectively separated for detection, but interference light is generated due to front and back surface reflections
Solution Approach 1:
The patent applies asymmetry by making the first diameter (D1) of the laser light along the parallel axis smaller than the second diameter (D2) along the orthogonal axis. This asymmetric beam shaping ensures that the reflected light from the front surface and back surface do not overlap, thereby preventing interference light generation while maintaining effective light separation for accurate measurement
Solution Approach 2:
The patent addresses the interference problem by introducing a dimensional parameter - the relative diameters of the laser light in different directions. By controlling the beam dimensions in the parallel and orthogonal directions separately, the solution transforms a one-dimensional problem (light separation) into a two-dimensional solution (asymmetric beam shaping), preventing overlap of reflected beams
2Measurement precision
If the first diameter of laser light is made smaller than the second diameter, then overlapping of reflected light beams is prevented, but the light transmission member design becomes more complex
Solution Approach 1:
The patent implements parameter changes by controlling the physical dimensions of the laser light beam - specifically setting the first diameter (D1) smaller than the second diameter (D2). This parameter adjustment is achieved through the light transmission member's optical properties and geometry, allowing precise control of beam shape to prevent interference while maintaining design simplicity
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
Prevents interference light generation, maintaining high measurement accuracy by minimizing overlapping areas of reflected light beams and ensuring sufficient light amounts for accurate biological information detection.
Implementation Method 1
The light transmission member reflects a part of the laser light and separates the laser light into a first light beam and a second light beam
Implementation Method 2
a first light receiving unit configured to detect the first light beam
Implementation Method 3
a second light receiving unit configured to detect scattered light generated when the second light beam enters the living body
Data Source
AI summary
A biological information measurement apparatus includes: a light emitting unit configured to emit laser light to a living body; a light transmission member configured to reflect a part of the laser light and separate the laser light into a first light beam and a second light beam; a first light receiving unit configured to detect the first light beam; and a second light receiving unit configured to detect scattered light. The light transmission member has a first surface where the laser light enters and a second surface where the laser light entering the first surface enters, and D1<D2, in which a parallel axis parallel to an intersection line between the first surface and an entering surface on which the light emitting unit and the first light receiving unit are disposed is defined as a first axis, an orthogonal axis orthogonal to the first axis on the first surface is defined as a second axis, D1 is a first diameter of the laser light along the first axis, and D2 is a second diameter of the laser light along the second axis.