Compact Aiming Light Assembly With Field Lens Imaging
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Solution Overview
Problem
Existing compact aiming light assemblies for imaging readers using LEDs face challenges in generating a small, uniform, and bright aiming light spot over an extended range of working distances due to large divergence angles and optical artifacts, which result in low optical power and non-uniform brightness, especially when components are misaligned.
Innovation Solution
The solution involves an aiming light assembly with a light emitting diode (LED), a field stop, and an aiming lens, where a field lens is added to image the LED onto the lens aperture of the aiming lens, maintaining the assembly's compactness and improving brightness and uniformity by eliminating optical artifacts and tolerating misalignments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an LED is used as the aiming light source to avoid laser safety concerns, then the device becomes safer for healthcare and retail applications, but the large divergence angle and optical artifacts from the LED chip surface result in low optical power and non-uniform brightness in the aiming spot
Solution Approach 1:
A field lens is introduced as an intermediary optical element between the LED and the aiming lens. This field lens images the LED chip onto the aperture of the aiming lens, serving as a mediator that transforms the divergent LED light into a controlled beam that can be properly focused by the aiming lens, thereby achieving uniform brightness without requiring laser light
Solution Approach 2:
The patent changes the optical parameters of the system by introducing the field lens with specific focal length and positioning it at a specific distance from the LED. This parameter change transforms the light propagation characteristics, converting the LED's large divergence angle into a controlled beam profile that maintains uniformity across the aiming spot while preserving safety benefits
2Volume of moving object
If the LED is positioned close to the field stop to maintain compactness, then the assembly size is reduced, but the large divergence angle causes significant misalignment sensitivity and non-uniform brightness
Solution Approach 1:
The field lens acts as a compensating intermediary that optically couples the LED to the field stop. By imaging the LED onto the aiming lens aperture, it creates a virtual source position that is less sensitive to physical misalignments, thereby providing manufacturing tolerance compensation while maintaining compact dimensions
Solution Approach 2:
The optical design incorporates built-in compensation for potential misalignments through the field lens configuration. This beforehand cushioning ensures that even if manufacturing or assembly variations occur, the aiming spot uniformity is maintained because the optical path is pre-configured to tolerate such variations
3Illumination intensity
If the LED is imaged onto the aiming lens aperture using a field lens, then the aiming spot uniformity and brightness are improved, but additional optical components increase the assembly complexity
Solution Approach 1:
The field lens serves multiple functions simultaneously: it images the LED onto the aiming lens aperture to ensure uniform illumination, it controls the beam divergence to maintain compactness, and it provides alignment tolerance compensation. This multi-functionality achieves improved uniformity without proportionally increasing 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
This configuration enhances the brightness and uniformity of the aiming light spot, maintaining the assembly's compact size and improving visibility across the working distance range, even with component offsets, thereby enhancing the aiming process.
Implementation Method 1
a field lens is added to image the LED onto the lens aperture of the aiming lens
Implementation Method 2
an aiming lens having a lens aperture and an optical axis. The aiming lens is spaced along the optical axis away from the field stop and is operative for optically modifying the aiming light beam passing through the field stop to form the at least one aiming light spot
Implementation Method 3
a light emitting diode (LED) for emitting an aiming light beam
Data Source
AI summary
An aiming light assembly generates an aiming light spot with increased brightness and uniformity over a range of working distances in which targets are electro-optically read by image capture. The assembly includes a light emitting diode (LED) for emitting an aiming light beam, a field stop through which the aiming light beam passes, an aiming lens for optically modifying the aiming light beam passing through the field stop to form the aiming light spot over the range of working distances, and a field lens located in the vicinity of the field stop and operative for imaging the LED downstream of the field stop and in the vicinity of a lens aperture of the aiming lens.