JPH0582656B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a focus state inspection device that can be used in an optical information recording/reproducing device or an adjustment device thereof.

2. Description of the Related Art Structures of Conventional Examples and Their Problems In recent years, many optical information recording and reproducing devices that optically record and reproduce information at high density have appeared on the market. Among these, video disks and PCM audio disks are generally well known. Such optical information recording and reproducing devices require precise focus control in order to improve the information recording density.
For this reason, offset adjustment for focus control is generally performed when assembling an optical information recording/reproducing device or even during operation.
A means to directly evaluate the quality of the reproduced signal and inspect the focus state is required.

A conventional focus state inspection device for detecting offset in focus control will be described below with reference to the drawings. FIG. 1 is a block diagram of a conventional focus state inspection device, in which 1 is a reproducing head, 2 is a focus signal detection means, 3 is a control circuit, 4 is an actuator, 5 is an adder, 6 is an oscillator, and 7 is an AM detector. vessel,
8 is a synchronous detector, 9 is a low pass filter, and 10 is an information recording carrier.

The operation of the focus state inspection device configured as described above will be described below. The reproducing head 1 focuses a light beam on the information recording surface of the information recording carrier 10 and detects the reflected light to read information. At this time, the reproducing head 1 outputs a signal containing a component related to the focused state of the light beam on the information recording carrier together with the read signal, and the focus signal detection means 2 detects a focus signal related to the focused state from this signal. To detect. Based on this focus signal, the control circuit 3 drives the actuator to keep the focused state of the light beam on the information recording surface constant. However, this focused state is not necessarily optimal, and generally, in order to optimize the focused state, offset adjustment is performed while detecting the focused state from the read signal output from the reproducing head 1. The focused state is detected as follows. The oscillation signal of a predetermined frequency outputted from the oscillator 6 is added to the focus signal in the adder 5, so that the focused state oscillates at the predetermined frequency. The amplitude of the read signal varies with this fluctuation. Therefore, this read signal is subjected to AM detection by the AM detection means 7, and an AM test signal is output.This AM detection signal is synchronously detected by the above-mentioned swing signal, and the low-pass filter 9 detects the AM detection signal from the output. The focused state can be detected by extracting the low frequency component. That is, when the focused state oscillates around the state where the amplitude of the read signal is maximum, the DC component of the output of the low-pass filter 9 becomes zero, and the amplitude of the read signal is oscillated from the state where the amplitude is maximum. When the focused state oscillates around the shifted state, the output of the reduced pass filter 9 comes to include a DC component, and the direction of the shift can be identified from its polarity.
That is, the output of the low-pass filter 9 indicates the focus state, and when this output is zero, it indicates the focus state where the amplitude of the read signal is maximum.

However, in the above configuration, the focus error is detected based on the amplitude of the read signal, so (i) even if the quality of the read signal deteriorates, the amplitude may hardly change, so the detection accuracy of the focused state is is not good.

(ii) The focused state where the amplitude of the read signal is maximum does not necessarily coincide with the focused state where the quality is the best.

There was a problem.

OBJECT OF THE INVENTION An object of the present invention is to provide a focus error detection device that enables accurate inspection of the focus state of an optical information reproducing device that reproduces information from an information record carrier storing digital information. be.

Structure of the Invention The focus error detection device of the present invention has a reproducing head that focuses a light beam on an information recording carrier on which a binary signal is recorded, reads information, and outputs an information signal, and a reproducing head that outputs an information signal, and a reproducing head that outputs an information signal, and a reproducing head that outputs an information signal, and a reproducing head that outputs an information signal by focusing a light beam on an information recording carrier on which a binary signal is recorded. The device is configured to have a counting means for counting the number of times shorter than a predetermined length set near the minimum inversion interval of a binary signal for a predetermined time, and thereby information is transferred from an information recording carrier on which digital information is recorded. This makes it possible to accurately inspect the focus state of an optical information reproducing device that reproduces information.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a block diagram of a focus state inspection device according to an embodiment of the present invention. In FIG. 3, 11 is a waveform shaping means, 12 is an inversion interval detecting means, 13 is a counting means, and 14 is a clock generating means.

The operation of the focus state inspection apparatus of this embodiment configured as described above will be explained below. first,
As in the case of FIG. 1, the reproducing head 1 is controlled by the focus signal detection means 2, the control means 3 and the actuator 4 to focus on the information recording carrier 10, and reads information. The read signal read by the reproduction head 1 is processed by the waveform shaping means 11.
The waveform is shaped, and the inversion interval is measured by the inversion interval detection means 12. The reversal interval detection means 12 generates a pulse when the reversal interval is less than a predetermined value. The counting means 13 is cleared by the clock output from the clock generating means 14, and counts the number of pulses generated until the next clock. Generally, as the focus condition worsens, intersymbol interference increases when reading digital signals. Normally, as intersymbol interference increases, the inversion interval of a signal read from the minimum inversion interval determined by the modulation method becomes even shorter. Therefore, when the focus condition deteriorates, many inversion intervals shorter than a predetermined length set to about the minimum inversion interval appear. Therefore, the counting means 1
The count number 3 increases or decreases depending on the focus state, and the count number is the minimum when the focus state is the best. That is, the focus state can be inspected based on this count number.

As described above, according to this embodiment, the information record in which digital information is recorded can be This makes it possible to accurately inspect the focus state of an optical information reproducing device that reproduces information from a carrier.

Next, other embodiments of the present invention will be described with reference to the drawings.

FIG. 3 shows a block diagram of a focus state inspection device according to another embodiment of the present invention. In FIG. 3, 15 is a storage means, 16 is a comparison means, and 17
18 is a reversible counter, 18 is a D/A conversion means, 19 is an addition means, 20 is a tracking control means, and 21 is a tracking jump means.

The operation of the focus state inspection apparatus of this embodiment configured as described above will be explained below. first,
The reproducing head 1 is focus-controlled and the information recording carrier 10 is
The steps from here on are the same as in the previous embodiment, but here tracking control is further performed by the tracking control means 20. Truck jump means 21
By generating a jump pulse in synchronization with the rotation of the information recording carrier 10 and applying it to the tracking control means 20, the same portion of the spiral information track formed on the information recording carrier 10 is repeatedly reproduced. Hereinafter, the waveform shaping means 11, the inversion interval detection means 12, the counting means 13 and the clock generation means 14 operate in the same manner as in the previous embodiment.
5 records the value of the counting means 13 immediately before being cleared by the clock. Furthermore, comparison means 16
compares the value of the counting means 13 immediately before being stored in the storage means 15 with the previously stored value of the storage means 15, and sets the reversible counter 1 according to the magnitude thereof.
7 controls the clock to count forward or count backward. The D/A conversion means 18 performs D/A conversion on the count value of the reversible counter 17, and the addition means 19 adds the output to the focus error signal.

As described above, according to this embodiment, the reproduction head 1
Since the same portion of the information track is repeatedly reproduced, it is possible to suppress fluctuations in the focus state test value due to changes in the stored information signal. Also,
As in the above embodiment, the reliability of the information reproducing apparatus can be improved by adding an appropriate bias value determined according to the output of the focus state inspection apparatus to the focus error signal.

In addition, the reversal interval detection means 1 in the above embodiment
2 may be any device that can detect that the state reversal interval is less than or equal to a predetermined length. For example, by generating a clock with a cycle sufficiently shorter than the minimum reversal interval, This clock can be counted by the clock and a pulse is generated when the count value is less than a predetermined value, or a monostable multivibrator can be set by reversing the state of the read signal and the next pulse is generated before it is reset. It is possible to use a configuration that generates a pulse when a state reversal occurs.

Further, the track jump means 21 is configured to generate a jump pulse in synchronization with the rotation of the information recording carrier 10, but the jump pulse is generated at a predetermined timing so that the same portion of the information track is repeatedly read by the reproducing head 1. Any such configuration may be used; for example, it may be configured to generate a jump pulse when the read head 1 reads a predetermined address.

Effects of the Invention As is clear from the above description, the present invention provides a reproducing head that focuses a light beam on an information recording carrier on which a binary signal is recorded, reads information, and outputs an information signal, and a reproducing head that outputs an information signal, and a reproducing head that outputs an information signal, and and counting means for counting the number of times the interval is shorter than a predetermined length for a predetermined time, so that the focus state of an optical information reproducing device that reproduces information from an information record carrier on which digital information is recorded can be accurately determined. This provides an excellent effect of allowing thorough inspection. As a result, it is possible to accurately adjust the offset of the focus control device of the optical information reproducing device.

The recording medium is further provided with track jump means for moving the tracking position of the reproduction head to a nearby information track at a predetermined timing so that the reproduction head repeatedly traces the same portion of the spiral information track of the information recording carrier. As a result, it is possible to suppress fluctuations in the test value of the focus state due to changes in the recorded information signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional focus state inspection device, FIG. 2 is a block diagram of a focus state inspection device in one embodiment of the present invention, and FIG. 3 is a block diagram of a focus state inspection device in another embodiment of the present invention. It is a block diagram. 1... Reproduction head, 11... Waveform shaping means, 1
2... Reversal interval detection means, 13... Counting means.

Claims (1)

[Scope of Claims] 1. A reproducing head that focuses a light beam on an information recording carrier on which a binary signal is recorded, reads information, and outputs the information signal, and a reproduction head that outputs the information signal, and a state inversion interval of the information signal is the minimum of the binary signal. 1. A focus state inspection device comprising: counting means for counting the number of times shorter than a predetermined length set in the vicinity of a reversal interval for a predetermined time. 2. The information recording carrier has a spiral information track, and track jump means moves the tracking position of the playback head to a nearby information track at a predetermined timing so that the playback head repeatedly tracks the same portion of the information track. A focus state inspection device according to claim 1, characterized in that it comprises: