Optical Disc Feedforward Control for Label Printing
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Solution Overview
Problem
Existing optical disc devices face challenges in achieving high accuracy for focusing laser light on a laser label print face due to low reflectance and surface irregularities, leading to noise in reflection signals and inadequate control accuracy for feedback control systems, which affects print quality and processing time.
Innovation Solution
The optical disc device employs feedforward control with higher operation resolution for the focusing actuator, using a data processing unit to switch the gain of the driver circuit and convert control data into analog signals with a larger bit number, allowing for precise focusing by measuring and storing surface wobbling data and interpolating control data for efficient label printing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If feedback control with standard digital-to-analog conversion circuit and driver circuit is used to drive the focusing actuator, then the system can record and reproduce digital information, but the control accuracy of the objective lens position reaches only ±1 micrometer which is insufficient for laser label printing requiring ±30 micrometers accuracy
Solution Approach 1:
The patent divides the control system into two independent pathways: feedback control for data recording/reproduction and feedforward control for label printing. Each pathway has its own digital-to-analog conversion circuit with appropriate resolution (16-bit for feedforward, 8-bit for feedback) and driver circuit gain settings. This segmentation allows each subsystem to be optimized for its specific function without compromising the other, resolving the contradiction between precision requirements and system complexity.
Solution Approach 2:
The patent implements dynamic switching between feedback control mode and feedforward control mode based on the operational requirement. The control system can adaptively change the operation resolution of the focusing actuator and the gain of the driver circuit according to whether the task is data recording or label printing. This dynamic adjustment enables the system to achieve ±30 micrometers accuracy for label printing while maintaining ±1 micrometer accuracy for data operations, without requiring permanently high-resolution components that would increase overall system complexity.
2Manufacturing precision
If the operation resolution of the focusing actuator is increased for feedforward control to achieve ±30 micrometers accuracy, then label printing quality improves, but the processing time increases due to larger bit number conversion
Solution Approach 1:
The patent performs preliminary measurement and storage of surface wobbling characteristics of the optical disc before label printing. The feedforward control data, including the high-resolution focusing actuator control signals (16-bit), are pre-calculated and stored in memory based on the measured disc surface properties. During actual label printing, the system simply retrieves and executes the pre-computed feedforward control signals without performing real-time high-resolution digital-to-analog conversion, thereby achieving high print quality while minimizing processing time.
3Manufacturing precision
If feedforward control is implemented with high operation resolution for the focusing actuator, then the control accuracy reaches ±30 micrometers suitable for label printing, but the system requires separate digital-to-analog conversion circuit and driver circuit from feedback control
Solution Approach 1:
The patent applies local quality by providing different control circuit characteristics to different functional requirements within the same system. The feedforward control pathway uses a 16-bit digital-to-analog conversion circuit with specific driver circuit gain settings optimized for label printing, while the feedback control pathway uses an 8-bit digital-to-analog conversion circuit with different gain settings optimized for data recording. Each control pathway has locally optimized components matched to its specific precision requirements, avoiding the need to upgrade the entire system to the highest precision level.
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 approach improves the quality of laser label printing and reduces processing time by achieving the required control accuracy for clear prints without blurring or bleeding, even with surface wobbling, and allows for efficient data acquisition and processing.
Implementation Method 1
based on a focus error signal obtained from an output of a photo detector which detects reflection light from a disc
Implementation Method 2
move up and down an objective lens of an optical pickup while keeping constant the distance between the objective lens and the disc whose surface is wobbling with rotation
Implementation Method 3
irradiating the disc face with laser light for optical recording to record a title, a picture and a photograph
Data Source
AI summary
The optical disc device has a circuit which forms a focus error signal for focus servo control based on reflection light from an optical disc exposed to laser light. Also, the device has a data processing unit which can control by feedback a position to which an objective lens is moved by a focusing actuator based on a focus error signal. In label printing, the data processing unit controls, by feedforward, a position to which the objective lens is moved by the focusing actuator based on control data for label printing. The operation resolution of the focusing actuator in feedforward control is made higher than that in feedback control. Thus, an intended position control accuracy is achieved in feedforward control. For instance, in feedforward control, the gain of the driver circuit for the focusing actuator is switched to a smaller one in comparison to that in feedback control.