Optical Disc Focus Jump Control via Gain-Adaptive Thresholds
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Solution Overview
Problem
Existing optical disc driving devices face challenges in performing stable focus jumps between layers of a multilayered optical disc due to variations in the amplitude of the focus error signal and individual differences in disc and lens characteristics, making it difficult to accurately measure signal amplitudes and set appropriate threshold levels for focus actuation.
Innovation Solution
The optical disc driving device includes a control circuit that performs gain adjustments and balance adjustments based on focus error signals to generate focus loop and jump signals, allowing for stable focus jumps by setting threshold levels based on gain or balance adjustment information, thereby compensating for variations in disc and lens characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed threshold is applied to the FE signal for focus jump control, then the control logic is simple, but the focus jump cannot be performed accurately due to variations in FE signal amplitude caused by individual differences in disc and lens characteristics
Solution Approach 1:
The patent changes the parameter of threshold values from fixed to variable, making them adjustable according to the detected FE signal amplitude for each layer. This allows the threshold to adapt to individual differences in disc and lens characteristics, thereby achieving accurate focus jump control while maintaining relatively simple control logic.
2Measurement precision
If the FE signal amplitude is measured by rotating a disc with surface deflection, then the measurement can be performed, but it becomes difficult when the FE signal appears in synchronization with the rotational cycle
Solution Approach 1:
The patent performs preliminary action by measuring the FE signal amplitude during a preliminary focus search phase before normal playback. During this preliminary phase, the system detects and stores the FE signal amplitude characteristics for each layer, which are then used to set appropriate threshold values for focus jump control, avoiding the difficulty of measuring during rotational synchronization.
3Productivity
If the optical pickup unit focuses on the first layer, then the second layer cannot be accessed, but switching to the second layer requires focus jump which is slow due to inappropriate threshold values
Solution Approach 1:
The patent performs preliminary measurement of FE signal amplitudes for each layer during an initial focus search, and uses this information to pre-set appropriate threshold values for focus jump control. This preliminary action ensures that when layer switching is needed, the focus jump can be performed quickly and reliably with the pre-determined thresholds, improving both switching speed and reliability.
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 solution enables stable focus jumps between layers of a multilayered optical disc, even with individual differences in disc and lens characteristics, by adjusting threshold levels according to gain or balance information, ensuring accurate focus control and efficient data retrieval.
Implementation Method 1
focusing laser light from an optical pickup unit onto the multilayered optical disc
Implementation Method 2
converting read light which the optical pickup unit has acquired by applying light to a multilayered optical disc
Implementation Method 3
zero clear detection of a focus error signal (referred to as an FE signal from here on) which is generated on the basis of the output of the optical pickup
Data Source
AI summary
An optical disc driving device includes a control circuit 4 for performing a gain adjustment for each of two recording surfaces of a multilayered optical disc 1 on the basis of an FE signal in such a way as to maintain a state in which light is focused onto either of the recording surfaces, to generate a focus servo loop signal, and for generating a focus jump signal for causing either a transition from a state in which the light is focused onto one recording surface to a state in which the light is focused onto the other recording surface, or a transition in the opposite direction from a threshold set up on the basis of an amount of gain adjustment, and a focus actuator driving circuit 5 for performing either a focus jump or an operation of maintaining the state in which the light is focused.