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After issuing the focus close command, the following processes are taken for both DVD and CD. 1. Measure and optimize signal levels First drive PU lens far from the disc and then drive closer to the disc. At the focal point met in the process of this move, measure signal levels of FE, AS and RFENV respectively, and optimize their levels for FE and AS (1 & 2 in the above figure). 2. Focus closing Next, drive the lens far from the disc again to detect the closing levels of FE and AS. Then activate focus loop filter for closing focus (3 6). 3. Check closing Check the closing with signal levels of AS and RFENV (6 & 7). Focus search in test mode can check the signal levels and focus drive voltages for FE, AS and RFEV.
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1.2.2 Tracking Close
After issuing the tracking close command, the following processes are taken for both DVD and CD 1. Tracking brake Measure one half cycle of the tracking cross and if the cycle is within the range of designation, output the brake pals. Output direction of brake pals is determined by the phase relations of OFTR and TKC (TE's binarization) signals. After confirming that the swing of lens against disc is controlled, the brake stops and the closing begins. If the closing condition is not met within 10msec. after outputting brake, the brake stops and the closing begins. 2. Tracking closing Process the tracking drive hold with OFTR signal. 3. Check closing Check whether or not the track jump does not exceed the designated number within the designated term. Closing check will be time-out at 20msec. Retry using a command from the microcomputer.
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1.2.3 Track Jump
The system selects from three types of methods; i.e. interval jump, multi jump and traverse seek, according to the target number of moving tracks. 1. Interval Jump The detailed seek is capable due to the execution of repetitive one-track jumps. It is used when approaching to the target track or seek-operating to an adjacent track. 2. Multi Jump It counts both edges of the track cross signal TKC and moves for designated number of track counts. 3. Traverse Seek It controls the movement speed by measuring the time of the track cross signal TKC and manages the vibration of pickup generated upon movement to the minimum. Types of target number of moving jumps illustrating the jump switch setting for both DVD and CD DVD 1-10 Interval Jump 11-100 Multi Jump 101-500 Combination of Multi Jump and Interval Jump Over 501 Traverse Seek The waveforms of track jumps are shown in the next page.
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CD 1-10 Interval Jump 11-32 Multi Jump 33-500 Combination of Multi Jump and Interval Jump Over 501 Traverse Seek
