JPH0266735A - Cross track counter - Google Patents

Abstract

PURPOSE:To make unnecessary a complicated circuit such as a band variable filter and to count a correct cross pulse by generating a pulse to show a cross direction each time an optical spot crosses a track. CONSTITUTION:A reflecting light from a recording medium 1 becomes a track error signal 22 by a differential amplifier 8 and becomes a track sum signal 23 by a differential amplifier 11. A maximum value 24 and a minimum value 25 of the sum signal 23 are respectively peak-held 12 and 13. The maximum value 24 and the minimum value 25 are averaged and become an average value output 26. The output 26 is compared 15 with the sum signal 23 and becomes a groove detecting signal 28. On the other hand, the error signal 22 is zero-cross- detected 16 and becomes a track cross pulse 27. An FF17 fetches the level of the signal 28 with the rise edge of the pulse 27 and generates a direction signal 29. A timer 18 generates a cross pulse 30 of a constant time width with the rise edge of the pulse 27. A selector 19 selects a line to output a pulse 30 by a direction signal 29, generates an outer circumferential direction pulse 31 and an inner circumferential direction pulse 32 and sends them to an up-down counter 33.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a cross-track counting device in an optical storage/reproduction device, and more particularly to a cross-track pulse detection circuit required for positioning a track to a target track.

Prior Art Conventionally, in this type of optical recording and reproducing apparatus, when positioning the beam spot between targets 1 and 1, the error between the current track and the target track is calculated, and the beam is moved by the number of tracks corresponding to the error. By moving the spot, movement to the target trunk is performed. Here, in order to perform accurate positioning to the target track, it is necessary to accurately cross the track 14 times, but when counting the number of track crossings, the beam spot
There is no problem if the beam spot is moving at a speed sufficiently higher than the eccentric speed of the beam spot and the rack, but if the two speeds are approximately equal or the moving speed of the beam spot is lower than the eccentric speed, the beam spot (When traversing in the opposite direction because the moving direction of and the traversal direction of
~ Even if you try to cross the rack, it may cause a clunk, making it difficult to accurately count the number of track crossings.

Therefore, the idea was to use the difference in the amount of reflected light between the grooves to detect the gap between the grooves, and to calculate the slope of the 1~Rack crossing signal when the beam passes over the groove or between the grooves. Alternatively, the track cross direction is detected by a change in the polarity of the signal, and an inner circumferential direction cross pulse and an outer circumferential direction cross pulse are generated according to the cross direction signal, and the up and down operations of the counter are performed using these pulses. According to this method, even if the moving speed of the beam slots 1 to 1 becomes slower than the eccentric speed of the medium, accurate 1-rack crossing pulses can be obtained, so that accurate crossing pulses can be counted.

Here, in the detection between the grooves, the amount of reflected light decreases when the beam spots 1~ are on the grooves, and increases between the grooves, so this difference in the amount of reflected light is used to signal the output of the photodetector of the optical head. Noise components are removed using a filter that transmits only a predetermined signal component, and the signal is then sliced using a predetermined threshold value. This is to prevent unnecessary signals such as noise from being included and to remove slice level fluctuations due to I)C fluctuations due to fluctuations in medium reflectance, etc., by extracting only predetermined signal components. In order to prevent deviation from the track cross direction signal, filters with the same characteristics are inserted into both the rack cross direction signal and the photodetector output signal which is the signal of the amount of light reflected from the medium.

In the above-mentioned conventional cross track counting device, when detecting gaps and grooves, the output signal of the photodetector of the optical head is passed through a filter that transmits only a predetermined signal component, and then sliced at a predetermined threshold value for detection. Therefore, it is necessary to vary the filter characteristics depending on the track crossing speed. In addition, it is necessary to use filters with the same characteristics for both the tracking error signal, which is a 1~rack crossing signal, and the output signal of the photodetector, which does not control the amount of reflected light. In order to detect by slicing with a threshold value, it is necessary to suppress the filter band to a narrow range to the extent that changes in medium reflectance can be ignored, which has the disadvantage of resulting in a complicated circuit configuration.

Purpose of the Invention Therefore, the present invention was made to eliminate the drawbacks of the conventional ones, and its purpose is to eliminate the need for complex circuits such as variable band filters, and to improve the It is an object of the present invention to provide a stable transverse track counting device that eliminates malfunctions due to variations in depth, width, reflectance of a medium, etc.

According to the present invention, there is provided a transverse track counting device for irradiating a recording medium with a minute optical spora l~ and moving this optical spoiler +- onto a target track, the apparatus comprising: a positional deviation detection means for generating a signal corresponding to the positional deviation with respect to the track; a reflected light amount detection means for generating a signal according to the amount of light reflected from the recording medium by the light spot; and a detection output from the reflected light amount detection means. average value detection means for generating an average value signal corresponding to the average value of the amount of reflected light from the maximum value and minimum value of the amount of reflected light; a groove detecting means for detecting that 1~ is on the groove between the 1~ racks, and an output of the positional deviation detecting means and an output of the groove detecting means, each time the light spot crosses the track. There is obtained a transversal track run 1--device characterized in that it comprises means for generating a pulse indicating the transverse direction, and the pulse indicating the transverse direction is supplied to an up-down counting circuit.

Example Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, the beam emitted from the laser light source 2 is 27
The light is irradiated onto the medium 1 through the imager 1 to lens 3, the beam printer 4, and the objective lens 5. The reflected light from the medium 1 passes through the objective lens 5, is reflected by the beam splitter 4, and is irradiated onto the photodetector 6.

The signal photoelectrically converted by the photodetector 6 is input to the differential amplifier 8 and becomes a tracking error signal 22, and is also input to the summing amplifier 1.
1 and becomes the track sum signal 23. The track error signal 22 passes through the phase correction circuit 9 and the drive circuit 10 to drive the locking actuator 1 to 7 to perform a track following operation.

The track sum signal 23 is input to the peak hold circuit 12 and the peak hold circuit 13. Peak hold circuit 1
2 peak-holds the maximum value of the track sum signal, and peak bold circuit 13 peak-holds the minimum value of the track sum signal. Each peak bold circuit output, 4=f2
4 and 25 are input to the average value circuit 14, and an average value output 26 of both is obtained.

Further, the track sum signal 23 is compared with an average value output 26 by a level comparison circuit 15 and becomes a groove detection signal 28.

1, the rack error signal 22 is detected as a zero cross by the zero cross detector 16 and becomes a track crossing pulse 27.
It is input to F/F (flip-flop) 17 and timer 18. The F/F 17 receives the level of the groove detection signal 28 at the rising edge of the track crossing pulse 27, and outputs the direction signal 2.
generate one. The timer 18 generates a crossing pulse 30 of a constant time width at the rising edge of the track crossing signal 27, and inputs it to one selector. One selector selects a line for outputting a transverse pulse 30 based on a direction signal 29, generates an outer circumferential direction pulse 31 and an inner circumferential direction pulse 32, and sends them to an amplifier town counter 33. The up/down counter 33 counts the number of track crossings and generates a track search end signal when the number matches a target value.

FIG. 2 is a diagram illustrating the circuit operation of the present invention.

The track error signal 22 is a signal that crosses zero on the groove and between the grooves, and at this time, the rack sum signal 23 to 1 is minimum on the groove and maximum between the grooves. Therefore, it can be seen that by using this level difference of the track sum signal, it is easy to recognize whether a groove is located between grooves.

Here, the amplitude of the track sum signal on the groove changes when the groove depth, width, and medium reflectance change. Therefore, there is a high possibility of variation not only between media but also within the same surface of the media. Therefore, it is necessary to be able to stably recognize the grooves and between the grooves even if these parameters change, but here, the track sum signal 23 between the grooves and between the grooves is held by the peak hold circuit 12.13. In addition to obtaining an inter-groove hold output 24 and an on-groove bold output 25, an average value output 26 is determined by an average value circuit 14 and compared with an I/rack sum signal 23 by a level comparison circuit 15 to obtain a groove detection signal 28.

According to this method, the slice level of the track sum signal 23 is always at the intermediate level of the groove and the difference in the track sum signal 23 between grooves, so it is stable regardless of fluctuations in the depth, width, reflectance, etc. of the groove. A groove detection signal 28 is obtained.

) - The rack error signal 22 is zero-cross detected by the zero-cross detection circuit 16, and a track crossing pulse 27 is obtained. Here, since the optical spot is on the groove when the groove detection signal 28 is at a high level, it can be recognized which edge of the track crossing pulse is the zero-crossing timing on the groove. where - cross-track pulse 27
The polarity change on the groove differs depending on the direction across the track, and the polarity is reversed when moving toward the outer circumference and when moving toward the inner circumference, so it is easy to detect the direction of movement. .

FIG. 3 shows the timing at which the outer circumference direction pulse 31 and the inner circumference direction pulse 32 are generated from the track crossing pulse 27 and the groove detection signal 28.

First, at the rising edge of the track crossing pulse 27, the groove detection signal 2
If 8 is high level, set F/F 17 to high and set Sera 1
-, and if the groove detection signal 28 is at a low level, it is set to low. The output of this F/F 17 is output as a direction signal 27, and the selector 19 selects an output line.
When the F/F 17 is high, the inner circumferential direction pulse 32 is output, and when it is low, the outer circumferential direction pulse 31 is output.

The track crossing pulse 27 is input to the timer 18, which outputs an output pulse of a constant time width at the rising edge. The transverse pulse 30 of the timer 18 is selected to be output by one selector, and a direction pulse is output in accordance with the direction signal 27. The inner circumferential direction pulse 32 and the outer circumferential direction pulse 31 are inputted to an up/down counter 33, thereby making it possible to accurately cross the track regardless of the rack traversal speed.

Although not shown in this embodiment, the detection of the track crossing direction is necessary to accurately obtain the number of track crossings when the track crossing speed approaches or becomes lower than the eccentric speed due to medium eccentricity. Since it is necessary to recognize whether the track has been traversed in the circumferential direction or the outer circumferential direction, it is not necessary to stably obtain a direction signal up to a region where the track crossing speed is higher than the steel core speed of the medium, and it is not necessary to stably obtain a direction signal in this speed region. Then, the F/F is forcibly set in the transverse direction of the rack, which is known in advance, and when the rack crossing speed approaches the eccentric speed of the medium, the direction detection signal 28 is used to detect the direction. If this method is adopted, the signal band from 1 to Rack Washinzuki can be kept low. Therefore, disturbances in the peak hold signal due to medium defects are reduced, and a large hold time constant for peak hold can be obtained, suppressing slice level fluctuations at low speeds and making stable groove detection possible.

As explained above, according to the present invention, each level is held by utilizing the fact that the track sum signal is maximum between grooves and minimum on the groove, and the 5V average value of each hold output is calculated. By slicing the rack sum signal into 1 and detecting it, there is no need for complex circuits such as variable band filters, and stable traversal is possible without malfunctions due to fluctuations in groove depth, width, medium reflectance, etc. It has the effect of being able to detect direction.

Therefore, highly accurate searches can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a signal waveform diagram of each part showing the operation of the blocks in FIG. 1, and FIG. 3 is a time chart showing the relationship between the track crossing direction and the directional pulse. Explanation of symbols of main parts 1... Recording medium 8... Working amplifier 11... Summing amplifier 1.2.13... Peak hold circuit 14...
... Average value circuit 15 ... Level comparison circuit 16 ... Zero cross detection circuit

Claims (1)

[Claims] (1) A cross-track counting device for irradiating a recording medium with a minute light spot and moving this light spot onto a target track, which outputs a signal corresponding to the positional deviation between the light spot and the track. A positional deviation detection means that generates a positional deviation, a reflected light amount detection means that generates a signal corresponding to the amount of reflected light from the recording medium by the light spot, and a reflected light amount detection means that detects the reflected light from the maximum and minimum values of the detection output from the reflected light amount detection means. an average value detection means that generates an average value signal corresponding to the average value of the light amount; and a level comparison between the average value signal and the output of the reflected light amount detection means to determine that the light spot is on the groove between the tracks. Groove detection means for detecting;
means for generating a pulse indicating the transverse direction each time the light spot crosses the track using the output of the positional deviation detecting means and the output of the groove detecting means, and increasing the pulse indicating the transverse direction. A cross-track counting device characterized in that the supply is supplied to a down counting circuit.