Laser Spot Indicator Projection With Reduced Diffraction
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Solution Overview
Problem
Conventional barcode readers with LED-based spot indicators suffer from limited visibility range and diffraction effects, making it difficult to see the spot indicator at distances beyond 1 meter, especially in bright ambient conditions, due to physical constraints and inefficiencies in the optical projection system.
Innovation Solution
An optical system using a laser diode as a coherent light source, with a structured aperture and imaging lens configuration that positions the object plane between the light source and aperture, optimizing the distance between emission points to project a brighter, diffraction-free spot indicator at longer ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If an LED light source is used to project a spot indicator, then the device can be compact and energy-efficient, but the brightness is weak at distances greater than 1 meter making the spot indicator difficult or impossible to see
Solution Approach 1:
The patent changes the fundamental parameter of light coherence by replacing the incoherent LED light source with a coherent laser light source. This parameter change enables the light to maintain intensity over longer distances through constructive interference, directly resolving the contradiction between compact device size and extended visibility range.
2Length of stationary object
If a laser diode is used to increase brightness and range, then the spot becomes brighter at longer ranges, but diffraction patterns are produced that make the projected circle look like a blob or non-circular shape
Solution Approach 1:
The patent introduces an intermediary element - a specifically designed aperture structure with multiple openings - that mediates between the coherent laser light source and the final projected spot. This aperture structure controls and shapes the light paths to eliminate diffraction patterns while preserving the benefits of coherent light, thus resolving the contradiction between extended range and shape uniformity.
3Illumination intensity
If the dimension of the spot is reduced to increase brightness at distance, then the spot becomes brighter, but the device size is constrained by miniaturization efforts
Solution Approach 1:
The patent employs dynamic optical elements including movable mirrors and adjustable aperture structures that can be positioned at different distances from the laser source. This dynamic configuration allows the system to achieve high brightness at various distances without requiring a fixed large device volume, resolving the contradiction between spot brightness and device 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
The solution enables a brighter and more visible spot indicator at distances up to 20 meters with sharp edges and reduced diffraction patterns, suitable for both handheld and non-handheld barcode readers, maintaining a compact size.
Implementation Method 1
a coherent light source. A structure defining an aperture may be disposed in optical alignment with and at a first distance from the coherent light source so that a divergent angle of coherent light output by the coherent light source is incident the structure and aperture
Implementation Method 2
the use of the green spot indicator allows for silent mode operation that is effective use in both quiet environments (e.g., hospitals, libraries, etc.) and in noisy environments (e.g. manufacturing floor, warehouse/distribution centers, outdoors, grocery stores, etc.). Consider the case where the light source implemented for spot indicators (e.g., green spot, aiming spot, or other function or shape) is constituted by a light-emitting diode (LED), emitting Lambertian-distributed light or diffused light that is non-coherent, that shines through a circular aperture that is imaged by a single lens. Because of inefficiencies of the light projection system (see FIG. 2A, for example), at distance (e.g., greater than 1 meter), the brightness is weak, thereby making the spot indicator either difficult or often impossible to see by a user, especially in bright ambient conditions.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A system and method for projecting coherent light with reduced diffraction pattern may include a coherent illumination source, structure with an aperture, and focusing lens. The focusing lens may have an object plane defined between the illumination source and structure, such that an illumination signal, such as an indication signal (e.g., green spot, aiming signal, etc.) that is projected through the aperture and onto an image plane does not exhibit a noticeable diffraction pattern, thereby having sharper edges and more perceptible to a user of a system that performs the projection of coherent light. The focusing lens may be in front of, at, integrated with, or behind the structure with the aperture, but the object plane remains between the coherent illumination source and structure with the aperture.