Optical Mouse Laser Diode Safety Control Circuit
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Solution Overview
Problem
Conventional optical mice using coherent light sources pose eye safety hazards due to potentially excessive laser beam intensity, and existing solutions often require complex and costly optical elements to mitigate this issue.
Innovation Solution
An optical mouse with a control circuit that restricts the optical power of a coherent light source to safe levels using a calibration circuit and fault detection circuit, preventing excessive current flow to ensure eye safety without the need for lenses or complex optical elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a coherent light source (laser diode) is used in the optical mouse, then the optical resolution and cursor control precision are improved, but the eye safety is compromised due to excessive laser beam intensity
Solution Approach 1:
The patent changes the physical parameter of the laser beam by introducing a diffuser that increases beam divergence. This transforms the concentrated, high-intensity laser beam into a dispersed, low-intensity pattern, reducing the optical power density at any single point while preserving the overall optical resolution needed for cursor control
Solution Approach 2:
The patent introduces a diffuser as an intermediary optical element between the laser diode and the working surface. This diffuser mediates the interaction between the coherent light source and the target surface, scattering the light to reduce intensity while maintaining the functional optical pattern for precise cursor control
2Object-affected harmful factors
If optical elements such as lenses or diffusers are added to reduce laser intensity, then eye safety is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent employs a simple, inexpensive diffuser element that can be easily manufactured and integrated into the optical mouse. This cost-effective component provides the necessary beam divergence without requiring complex optical assemblies, thereby reducing overall device complexity and manufacturing cost while achieving eye safety
3Object-affected harmful factors
If the laser beam intensity is reduced to safe levels, then eye safety is improved, but the optical power available for normal operation decreases
Solution Approach 1:
The patent segments the laser beam spatially by introducing a diffuser that divides the concentrated beam into multiple dispersed paths. This segmentation reduces the power density at any single location (improving eye safety) while distributing the total optical power across a broader area, maintaining sufficient overall power for operational functionality
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 effectively limits optical power to safe levels, preventing eye damage while maintaining the necessary intensity for normal operation, thereby enhancing safety and reducing costs by simplifying the optical design.
Implementation Method 1
a vertical cavity surface emitting laser (VCSEL) positioned to project a laser beam onto the working surface
Implementation Method 2
a sensor positioned to detect the laser beam reflected from the working surface
Data Source
AI summary
A computer input apparatus is disclosed which has improved safety control. The computer input apparatus includes a calibration circuit to control the operation current of a coherent light source to be above a minimum threshold required for normal operations, but below an upper threshold for safety reason. The computer input apparatus includes a fault detection circuit to monitor fault conditions. When this computer input apparatus employs a coherent light source, it does not require any optical lens to diminish optical power.