Light Grid Microlens Aperture Field of View Control

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Solution Overview

Problem

Conventional light grids face issues with large space requirements, complex production, and interference from neighboring light sources due to the wide field of view of photodiodes, leading to incorrect behavior and faulty switching.

Innovation Solution

A light grid with a microlens array substrate where each microlens is assigned an aperture at its focal point, restricting the field of view and allowing for adjustable reception angles, reducing space requirements and simplifying production by eliminating the need for precise alignment of receiving optics with photodiodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional receiving optics with lens and aperture are used to restrict field of view, then interference from neighboring light grids is reduced, but the receiving optics take up considerable space (10-20 mm) and require complex assembly

Engineering Contradiction:

Improveinterference reductionVSAvoidinstallation space

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent combines the lens and aperture into a single integrated component - the microlens array substrate. Each microlens is formed directly on the substrate with its aperture, eliminating the need for separate lens and aperture components and their complex assembly. This merging reduces the overall volume while maintaining the field of view restriction function.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent replaces the conventional mechanical receiving optics (lens + aperture tube assembly) with a planar microlens array substrate that can be simply attached to the photodiode array. This substitution eliminates the need for precise mechanical positioning and complex assembly mechanisms, reducing both volume and manufacturing complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If conventional receiving optics with lens and aperture are used to restrict field of view, then interference from neighboring light grids is reduced, but manufacturing becomes complex and expensive due to multiple components and precise positioning requirements

Engineering Contradiction:

Improveinterference reductionVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The microlens array substrate serves multiple functions simultaneously: it focuses light onto the photodiodes, restricts the field of view through its aperture structure, and provides a planar mounting surface. This multi-functionality eliminates the need for multiple separate components, simplifying manufacturing while maintaining interference reduction capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If photodiodes without additional optics are used, then the reception solid angle is large (Ω = 2π), but light from interfering sources easily enters the receivers causing malfunctions and incorrect switching

Engineering Contradiction:

Improvereception angleVSAvoidinterference resistance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent segments the receiving field of view by providing individual microlenses and apertures for each photodiode. This segmentation restricts each photodiode to receive light only from its designated direction, preventing light from interfering sources outside the intended field of view from entering the receivers, thus improving interference resistance while maintaining appropriate reception angles.

Inventive Principle:

Principle #1Segmentation

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 design effectively minimizes optical crosstalk, reduces space requirements, and simplifies production while maintaining or increasing the detection area without increasing the overall depth, enhancing the performance and reliability of the light grid.

Implementation Method 1

each microlens is associated with an aperture, and the apertures are each located at the focal point of the associated microlens

Methodology Applied

Scientific EffectLight focusing: Lens

Data Source

PatentEP3620829B1Light grid

Publication Date: 2022.01.19 SICK AG

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AI summary

The light grid according to the invention comprises several light transmitting units for emitting transmitted light beams, several light receiving units that provide received signals according to the incident light and that can receive the transmitted light beams with an unobstructed beam path to form the light grid, receiving optics, and an evaluation unit for evaluating the intensity of the incident light on the light receiving units. To increase the performance of the light grid by restricting the field of view of the light receivers, it is proposed that the receiving optics comprise a substrate having a microlens array, with each microlens having an associated aperture, and the apertures being located at the focal point of the respective microlens.