Multi-Beam Scanning Optical System With Micro-Mirror Phase Control
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Solution Overview
Problem
Conventional multi-beam scanning optical systems with polygon mirrors are bulky and costly, and while micro-mirror devices offer a downsized alternative, they often result in uneven scanning speeds and density issues, particularly in color printers, due to shifted phase ranges and varying angular velocities.
Innovation Solution
A multi-beam scanning optical system employing a micro-mirror device as a deflector, with a light source having spaced laser emitters, a diverging property changing element, and a scanning speed controlling element, configured to satisfy specific conditions that ensure constant scanning speed and reduced scanning speed differences between laser beams, thereby achieving high-definition and high-quality scanning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polygon mirror is employed as a deflector in a multi-beam scanning optical system, then the system achieves stable scanning performance, but the system occupies very large space and causes high cost
Solution Approach 1:
The patent replaces the mechanical polygon mirror deflector with a micro-mirror device that can be oscillated at high frequency. This substitution enables the system to achieve compact size and reduced cost while maintaining scanning functionality through electronic control of the micro-mirror oscillation rather than mechanical rotation of a large polygon mirror.
Solution Approach 2:
The patent changes the operating parameters by using a micro-mirror device oscillated at high frequency (e.g., several kHz) compared to the low-speed rotation of a polygon mirror. This parameter change allows the system to achieve the same scanning line frequency with a much smaller and less expensive deflector, resolving the contradiction between size/cost and scanning performance.
2Area of stationary object
If a micro-mirror device is employed as a deflector to downsize the system, then the system occupies smaller space and costs less, but the scanning speed becomes uneven and density issues occur
Solution Approach 1:
The patent applies a phase advance to the drive signal for oscillating the micro-mirror device. This preliminary action compensates for the inherent phase lag in the oscillation system, ensuring that the micro-mirror reaches the correct angular position at the right time to maintain uniform scanning speed across all laser beams, thereby preventing density unevenness.
Solution Approach 2:
The patent employs feedback control by detecting the actual oscillation state of the micro-mirror device and adjusting the drive signal phase accordingly. This feedback mechanism ensures that scanning speed uniformity is maintained by dynamically compensating for variations in the oscillation characteristics of the micro-mirror device.
3Productivity
If multiple laser beams are concurrently scanned with a micro-mirror deflector, then productivity increases, but scanning speed differences between beams cause color unevenness
Solution Approach 1:
The patent applies phase advance to the drive signal that is specifically calculated to compensate for the position-dependent phase lag in the micro-mirror oscillation. This preliminary correction ensures that all multiple laser beams are scanned at uniform speeds across the entire scanning field, preventing color unevenness while maintaining high productivity through concurrent multi-beam scanning.
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 system provides favorable optical performance and high-definition drawing by ensuring constant scanning speed and minimizing scanning speed differences between laser beams, addressing the density and color unevenness issues in conventional micro-mirror-based systems.
Implementation Method 1
a diverging property changing element configured to change a diverging property of each of the laser beams emitted by the light source
Implementation Method 2
a deflector configured to be sine-functionally oscillated and to deflect each of the laser beams with the diverging property thereof changed
Data Source
AI summary
A multi-beam scanning optical system configured to scan a plurality of laser beams on a scanned surface in a predetermined scanning direction includes a light source emitting a plurality of laser beams from respective laser emitters spaced from each other in the predetermined scanning direction, a diverging property changing element changing a diverging property of each of the emitted laser beams, a deflector configured to be sine-functionally oscillated and to deflect each of the laser beams with the diverging property thereof as changed so as to scan each of the laser beams on the scanned surface in the predetermined scanning direction, and a scanning speed controlling element configured to control a scanning speed at which each of the laser beams deflected by the deflector is scanned on the scanned surface. The multi-beam scanning optical system is configured to satisfy a predetermined condition.