1. Field of the Invention
The present invention relates to an optical disc recording and playback apparatus that is configured so as to record signals onto a disc by a light beam emitted from a laser element built into an optical pickup, and to perform a playback operation of the signals that have been recorded on the disc by the light beam.
2. Description of the Related Art
Disc players for performing operations to read signals that have been recorded on a disc using an optical pickup are popular. However, in addition to the playback function, optical disc recording and playback apparatuses, which are configured to enable the recording of signals to discs by a light beam emitted from a laser element built into the optical pickup, have recently been manufactured on a commercial basis.
This optical disc recording and playback apparatus is configured so that the recording operation is performed on the basis of a synchronization signal that is sampled from a wobble signal obtained from groove called a wobble that is provided on the disc, and of a recording reference signal.
The optical disc recording and playback apparatus is configured so that the signal recording operation is performed according to a recording command from a computer apparatus, which is a host. This recording operation first stores into a buffer RAM a signal, which is to be recorded onto a disc, then performs the signal recording operation to the disc by reading out the signal stored in the buffer RAM.
In a state where the signal recording operation to the disc is performing normally, the write operation to the buffer RAM of the recording signal that is output from the computer apparatus, the read operation of the signal from the buffer RAM, and the recording operation to the disc of the signal that was read are performed to correspond to the quantity of the recording signals and the status of the recording to the disc.
Recording speeds are increased in order to perform the signal recording operation to the disc in a short period of time. However, when the quantity of the recording signals stored in the buffer RAM is insufficient while a high-speed signal recording operation is performed, a state occurs where the signal recording operation to the disc cannot be performed, namely, a condition called buffer under run occurs. As a method to solve this problem, a technique has been developed to temporarily stop the recording operation to the disc when the quantity of the recording signals stored in the buffer RAM drops below a predetermined value, or a recording interrupt preset value, and to resume the recording operation to the disc when the quantity of the recording signals stored in the buffer RAM exceeds a predetermined value, or a recording resume preset value.
As described above, a method exists for solving the problem of buffer under run by interrupting, then resuming the recording. The operation to resume the recording plays back the signal that has been recorded on the disc prior to the recording interruption by retracting the optical pickup from the recording interrupted position, synchronizes a synchronization signal that is included in the played back signal with a recording reference signal, and resumes the recording operation when synchronization is achieved.
The signal recording operation to the disc in the optical disc recording and playback apparatus is performed at a state of constant linear velocity. When rotationally driving the disc at a state of constant linear velocity, the angular speed of rotation is faster at the inside of the disc compared to the outside. Therefore, it is difficult to rotationally drive the spindle motor at the same high constant linear velocity from the inside to the outside of the disc.
As a method to solve this problem, a technique has been developed to change the linear velocity to a faster linear velocity as the recording position moves from the inside to the outside of the disc, namely, as the recording position moves to a position where the recording linear velocity can be increased. This operation to change the recording speed first stops the recording operation when a point is reached where the recording speed is to be changed, and performs a control operation for resuming the recording when the rotational speed of the disc attains a fast constant linear velocity due to an increase in the rotational speed of the spindle motor.
The operation to change the recording linear velocity was performed by interrupting and resuming the recording operation as described above. In the conventional technique, when the operation to change the rotational speed of the disc is performed after interruption of the recording operation, the position of the optical pickup is retracted to a fixed position from the recording interrupted position, and in this state the rotational speed is changed, and after the rotation stabilizes, a control operation is performed to resume the recording. For this reason, the time required from when the recording was interrupted until when the recording operation is resumed becomes long, which prevents the speed for the recording operation from being increased.
When the recording linear velocity is to be changed, the present invention concurrently retracts the pickup and changes the recording linear velocity. For this reason, the interruption time can be shortened. Furthermore, the amount of retraction of the recording position is determined while taking into consideration the time required to change the recording linear velocity of the disc. As soon as the change in the recording linear velocity completes, the recording can be resumed.