ToF Optical Layout Using Microlens Array for High Resolution
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Solution Overview
Problem
Existing time-of-flight distance measurement methods face challenges in achieving a compact and high-resolution optical apparatus due to the expansion of the angle of view caused by diffractive optical elements.
Innovation Solution
The proposed optical apparatus includes a light emitter with at least one light emitting element, a light receiver with multiple light receiving elements, an optical element with a microlens array, and an optical system featuring a first telecentric lens. The microlenses outnumber the light emitting elements, forming an afocal system with the telecentric lens to achieve high resolution and compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diffractive optical element is used to increase the resolution of projected light, then the resolution is improved, but the angle of view is expanded requiring a larger light receiving element array
Solution Approach 1:
The optical element is divided into multiple microlenses arranged in an array, where each microlens processes a portion of the light from corresponding light emitting elements. This segmentation allows the system to achieve high resolution through multiple discrete optical paths while maintaining a compact light receiving element array size, as each microlens focuses light to a specific region on the light receiving element array.
Solution Approach 2:
The patent transitions from a one-to-one correspondence between light emitting elements and light receiving elements to a many-to-many relationship through the microlens array. Each microlens can focus light from multiple light emitting elements onto multiple light receiving elements, creating additional optical paths in the angular dimension. This enables high resolution distance measurement without requiring a proportionally larger light receiving element array.
2Volume of stationary object
If the light emitting element array and light receiving element array have approximately the same sizes to share the imaging lens, then the device size is reduced, but the resolution is limited by the angle of view matching requirement
Solution Approach 1:
The imaging function is segmented across multiple microlenses rather than relying on a single shared imaging lens. Each microlens creates a focused spot on the light receiving element array, and the collective information from all microlenses provides high resolution distance measurement. This allows the light receiving element array to be smaller while maintaining high resolution, as each element receives focused light from its corresponding microlens region.
Solution Approach 2:
The patent changes the optical parameters by using an afocal system where the microlens array and telecentric lens have different focal lengths. This parameter change enables the system to decouple the angle of view matching requirement from the resolution requirement, allowing high resolution to be achieved without requiring the light emitting and light receiving element arrays to have the same size.
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 enables the development of a small and high-resolution optical apparatus, effectively addressing the limitations of previous methods by maintaining a compact size while enhancing resolution.
Implementation Method 1
an optical element including a plurality of microlenses
Implementation Method 2
The plurality of microlenses and the first telecentric lens form an afocal system
Implementation Method 3
a light receiver including a plurality of light receiving elements, an acquiring unit configured to acquire distance information to an object based on a time required from when the light emitter emits light to when the light receiver receives the light reflected by the object
Data Source
Figure 1
Figure 2~3
Figure 4(a)~4(c)
AI summary
An optical apparatus (1) includes a light emitter (111) including at least one light emitting element (211), a light receiver (121) including a plurality of light receiving elements (125), an optical element (112) including a plurality of microlenses (231), an optical system including a first telecentric lens (131), and an acquiring unit (122, 123) configured to acquire distance information to an object based on a time required from when the light emitter emits light to when the light receiver receives the light reflected by the object. The number of microlenses is larger than the number of light emitting elements. The plurality of microlenses and the first telecentric lens form an afocal system.