Optical Scanning Device APC Stability via Beam Splitter
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Solution Overview
Problem
Optical scanning devices using surface emitting lasers face challenges in stable scanning operations and precise light quantity detection due to the difficulty in implementing Auto Power Control (APC) without increasing costs or device size, as they lack a monitoring photodetector and are affected by light divergence angle variations.
Innovation Solution
An optical scanning device with a light source having multiple emitters, an optical element to reflect and transmit light, a photodetector with a sufficient light receiving surface, and a light deflector, where the photodetector receives light reflected by the optical element, ensuring a light quantity of at least 0.01 mW and a rate of change in light ratio less than 4% even with changes in full width at half maximum (FWHM) of the light beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a surface emitting laser is used as the light source, then the device can be compact and cost-effective, but it cannot emit light backward for monitoring purposes, making APC operation difficult
Solution Approach 1:
A beam splitter is introduced as an intermediary optical element to separate the light path from the surface emitting laser. The beam splitter redirects a portion of the emitted light to the photodetector for monitoring purposes, enabling APC operation without requiring the laser to emit light backward. This mediator resolves the contradiction by providing a indirect path for light monitoring while maintaining the cost-effectiveness of using a surface emitting laser.
2Reliability
If a beam splitter is used to branch light for monitoring, then APC operation can be performed, but the device size and cost increase
Solution Approach 1:
The patent optimizes the parameters of the beam splitter and photodetector to minimize the size of the monitoring system. By carefully selecting the beam splitter ratio and positioning the photodetector, the system achieves effective light monitoring with minimal additional components. This parameter optimization reduces the overall device size while maintaining APC operation capability.
3Measurement precision
If the light receiving surface size is increased to capture more light, then light quantity detection precision improves, but the device size increases
Solution Approach 1:
The patent optimizes the size parameter of the light receiving surface to achieve the minimum area required for sufficient light capture. By calculating and setting the photodetector area to the optimal value, the system achieves adequate light quantity detection precision without unnecessarily increasing the device size. This parameter optimization balances measurement precision with compact device design.
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 stable scanning operations and precise light quantity detection without increasing costs or device size, maintaining image density consistency across varying environmental conditions and long-term usage.
Implementation Method 1
an optical element located on a light path of the light beams emitted by the light source to reflect part of the light beams while transmitting residue of the light beams
Implementation Method 2
a photodetector having a light receiving surface to receive the light beams reflected by the optical element
Data Source
AI summary
An optical scanning device including a light source having multiple light emitters; an optical element to reflect and transmit the emitted light beams; a photodetector to receive the reflected light beams; an aperture having an opening to shape the transmitted light beams; a light deflector to deflect the transmitted light beams; and a scanning optics to guide the deflected light beams to a scanning surface. The quantity of each of the light beams received by the photodetector is not less than 0.01 mW, and the size of a light receiving surface of the photodetector is determined such that even when the full width at half maximum of the emitted light beams changes, the rate of change of the ratio of the quantity of the light beams detected by the photodetector to the quantity of the light beams passing through the opening of the aperture is not greater than 4%.