On-Axis Aimer Distance Measurement for Machine Vision Focus

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Solution Overview

Problem

Conventional machine vision systems require multiple images and computationally intensive methods for autofocus, which are time-consuming and inefficient, and often fail to accurately measure distance to the target due to misalignment of aiming and image acquisition axes.

Innovation Solution

An on-axis aimer and distance measurement assembly that uses a light beam coaxial with the optical axis for both aiming and distance measurement, incorporating a light source, receiver, and reflective elements like beam splitters and dichroic filters, allowing for single-distance-based control of vision system parameters such as focus, gain, and aperture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional machine vision systems use multiple images and computationally intensive methods for autofocus, then focus accuracy can be improved, but time consumption and processing complexity increase

Engineering Contradiction:
Improvefocus accuracyVSAvoidtime consumption
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The system performs distance measurement using the on-axis aimer and light beam before image acquisition, allowing autofocus to be pre-determined based on measured distance rather than requiring multiple test images and computational analysis during the imaging process

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

A separate distance measurement mechanism (on-axis aimer with light beam and receiver) is introduced as an intermediary to directly measure distance to the target, providing focus distance information without requiring computational analysis of multiple images

Inventive Principle:
Principle #24Intermediary (Mediator)

2Adaptability or versatility

If conventional systems use separate aiming and image acquisition axes, then operational flexibility is maintained, but distance measurement accuracy deteriorates due to misalignment

Engineering Contradiction:
Improveoperational flexibilityVSAvoiddistance measurement accuracy
Core Design Contradiction:
Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The system merges the aiming function and distance measurement function onto the same optical axis (the reader's optical axis), so that the on-axis aimer projects light beams and receives reflected light exactly along the image acquisition path, ensuring that distance measurement is performed at the precise location where images are captured

Inventive Principle:
Principle #5Merging (Combining)

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

Enables fast and accurate focus adjustment and image acquisition by determining relevant distances for improved image quality and 3D measurements, reducing the need for multiple images and enhancing pointing accuracy.

Implementation Method 1

a receiver configured to receive reflected light from the object based on the first light beam

Methodology Applied
Scientific EffectLight reflection: Reflection

Implementation Method 2

a processor device configured to determine a distance between the at least one lens and the object based on the reflected light

Methodology Applied
Scientific EffectTime of flight: Time of Flight

Implementation Method 3

a beam splitter configured to direct the light beam from the light source coaxially with the reader optical axis

Methodology Applied
Scientific EffectOptical reflection: Reflection

Implementation Method 4

a dichroic filter configured to transmit the illumination light and reflect the light beam from the light source

Methodology Applied
Scientific EffectDichroic filtering: Dichroic Filter

Data Source

PatentEP4217912B1Machine vision system and method with on-axis aimer and distance measurement assembly
Publication Date: 2025.10.15 COGNEX CORP
  • EP4217912B1 patent drawingFigure 1
  • EP4217912B1 patent drawingFigure 2
  • EP4217912B1 patent drawingFigure 3A~3B

AI summary

An on-axis aimer and distance measurement apparatus for a vision system can include a light source configured to generate a first light beam along a first axis. The first light beam can project an aimer pattern on an object and a receiver can be configured to receive reflected light from the first light beam to determine a distance between a lens of the vision system and the object. One or more parameters of vision system can be controlled based on the determined distance.