JPH0877591A - Optical information recording/reproducing device - Google Patents

Abstract

PURPOSE: To prevent an injury to the human body and to improve safety by detecting an optical path condition in a separation type optical head and instantly stopping the generation of a light beam when the fact that an optical path is interrupted is judged. CONSTITUTION: Outputs T1 , T2 of photodetectors are inputted to an MPU 5 through A/D converters AD1, AD2 respectively. The MPU 5 measures respective T1 , T2 signal when a track is traversed, and outputs comparative reference voltage values lower than respective minimum values by prescribed values to D/A converters DA1, DA2. CMPs 6, 7 compare the T1 , T2 with the outputs of the DA1, DA2, and inputs the compared result to a detection circuit 9 through an OR circuit 8. The circuit 9 stops LD emission through an LLD 10 only when the fact that the T1 or T2 becomes lower than the comparative reference voltage values is detected. Thus, the safety is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical information for recording information on an optical information recording medium, reproducing the information recorded on the recording medium and / or erasing the information recorded on the recording medium. The present invention relates to a recording / reproducing device. The present invention is particularly effective when applied to an optical information recording / reproducing apparatus in which the constituent elements of an optical head are divided into a movable portion and a fixed portion.

[0002]

2. Description of the Related Art Heretofore, various types of information recording media such as discs, cards, tapes, etc. have been known as information recording media for recording and reproducing information using light. Some of these optical information recording media are recordable and reproducible, and only reproducible. Recording of information on a recordable medium is performed by scanning an information track with a light beam that is modulated according to the record information and focused into a minute spot, and the information is recorded as an optically detectable information bit string. .

Information is reproduced from a recording medium by scanning an information bit string of an information track with an optical beam spot having a constant power such that recording is not performed on the medium and reflecting or transmitting light from the medium. Is detected.

The above-mentioned optical head used for recording and reproducing information on the recording medium is movable relative to the recording medium in the information track direction and in the direction transverse to the direction, and by this movement, the optical head is moved. Information track scanning of the beam spot is performed. An objective lens, for example, is used as a lens for narrowing the light beam spot in the optical head. The objective lens can be independently moved in its optical axis direction (focusing direction) and in a direction (tracking direction) orthogonal to both the optical axis direction and the information track direction of the recording medium. Held in. Such holding of the objective lens is generally performed through an elastic member, and the movement of the objective lens in the above two directions is generally driven by an actuator utilizing magnetic interaction.

Among the above-mentioned optical information recording media, a card-shaped optical information recording medium (hereinafter referred to as an optical card) is a small-sized, light-weight, convenient-to-carry, relatively large-capacity information recording medium, which will be large in the future. Demand is expected.

FIG. 4 is a schematic plan view of the write-once optical card, and FIG. 5 is a partially enlarged view thereof.

In FIG. 4, a large number of information tracks 42 are arranged in parallel on the information recording surface of the optical card 41 in the LF direction. A home position 43, which is a reference position for accessing the information track 42, is provided on the information recording surface of the optical card 41. Information track 42
Is 42-1 in order from the side closer to the home position 43,
42-2, 42-3, ... Are arranged, and as shown in FIG. 5, tracking tracks 54 are sequentially adjacent to these information tracks, such as 54-1, 54-2, 54-3 ,. It is provided. These tracking tracks 54 are used as guides for auto-tracking (hereinafter, referred to as AT) that controls the beam spot so that the beam spot does not deviate from a predetermined information track at the time of scanning a light beam spot during information recording / reproduction. .

This AT servo detects the deviation (AT error) of the light beam spot from the information track in the optical head, negatively feeds back the detection signal to the tracking actuator, and the objective lens is attached to the optical head main body. This is performed by moving in the tracking direction (D direction) and causing the light beam spot to follow a desired information track.

Further, during information recording / reproduction, when scanning an information track with a light beam spot, in order to make the light beam into a spot shape (focus) of an appropriate size on the optical card surface, Focusing (hereinafter referred to as AF) servo is performed. This AF servo detects a deviation (AF error) from the focused state of the light beam spot in the optical head, negatively feeds back the detection signal to the focusing actuator, and moves the objective lens to the optical head main body in the focusing direction. By moving the light beam spot to the optical card surface to focus the light beam spot on the optical card surface.

In FIG. 5, S₁ , S₂ , S₃ Is
Shows the light beam spot, S₁ And S ₃ Use the light spot of
And use AT to do S₂ AF using the light spot of
And the creation of information bits during recording and
Read out. In each information track, 56-
1,56-2 and 57-1,57-2 are pre-fo
Shows matted left and right address parts
Then, by reading this address part, the information track
Identification is performed. 55 (55-1 and 55-2 in the figure are phases
Is the data part, where the predetermined information is recorded.
Be done.

Here, the optical information recording method will be described with reference to the schematic view of the optical head optical system shown in FIG.

In FIG. 6, reference numeral 21 denotes a semiconductor laser which is a light source, and in this example, it emits light polarized in the direction of the paper surface. Further, 22 is a collimator lens, 23 is a beam shaping prism, 24 is a diffraction grating for splitting a light beam, and 25
Is a polarization beam splitter. Further, 26 is a quarter wavelength plate, 27 is an objective lens, 29 is a cylindrical lens,
Reference numeral 30 represents a photodetector.

The light beam emitted from the semiconductor laser 21 enters the collimator lens 22 as a divergent light beam. Then, it is made into a parallel light beam by the lens, and is further shaped by the beam shaping prism 23 into a beam having a predetermined light intensity distribution, that is, a circular intensity distribution. Then, the light flux enters the diffraction grating 24, and is divided into three effective light beams (0th-order diffracted light and ± 1st-order diffracted light) by the diffraction grating 24. These three light beams enter the polarization beam splitter 25 as P-polarized light beams. The polarization beam splitter 25 transmits nearly 100% of the incident P-polarized light.

Next, the three light beams are converted into a quarter wave plate 2
6 and is converted into circularly polarized light at this time, and the objective lens 2
It is focused on the optical card 1 by 7. As shown in FIG. 12, the focused light has three minute beam spots S ₁ (+ _1st-order diffracted light), S ₂ (0th-order diffracted light), and S ₃ (−
1st-order diffracted light). S ₂ is used for recording, reproduction and AF control, and S ₁ and S ₃ are used for AT control. The spot position on the optical card 1 is as shown in FIG.
The light beam spots S ₁ and S ₃ are located on the adjacent tracking tracks 4, and the light beam spot S ₂ is located on the information track 2 between the tracking tracks.
Thus, the reflected light from the light beam spot formed on the optical card 1 passes through the objective lens 27 again to be a parallel light beam, and passes through the quarter-wave plate 26 so that the polarization direction is 90 degrees from that at the time of incidence. ° Converted to a rotated light beam.
Then, it enters the polarization beam splitter 25 as an S-polarized beam and is guided to the detection optical system.

In the detection optical system, a spherical lens 28 and a cylindrical lens 29 are combined, and this combination performs AF control by the astigmatism method. The three light beams reflected from the optical card 1 are respectively collected by the detection optical system, enter the photodetector 30 and
Form two light spots. As shown in FIG. 15, the photodetector 30 is composed of light receiving elements 30a and 30c and a four-division light receiving element 30b. Light receiving element 30a,
30c receives the reflected light of the above-mentioned light spots S ₁ and S ₃ , and AT control is performed using the difference between the outputs of these two light receiving elements. The light receiving element 30b of the 4 division receives the reflected light of the light spot S _2, and recorded information is carried out AF control using the output is reproduced.

The processing of the signal detected by the detection optical system will be described with reference to FIG. The reflected light from the light spots S ₁ , S ₂ , S ₃ formed on the optical card 1 is
Light receiving elements 30a, 30b, 30 of the photodetector 30, respectively
Light spots S _a , S _b , and S _c are formed on _c .

The outputs from the diagonally divided portions of the four-division light receiving element 30b are added by the addition circuits 117 and 118, respectively. The outputs of the adder circuits 117 and 118 are added by the adder circuit 121, whereby the information reproduction signal RF
Is obtained. That is, the information reproduction signal RF corresponds to the total light quantity of the light spot S _b formed on the four-divided light receiving element 30b. Further, the outputs of the adder circuits 117 and 118 are subtracted by the differential circuit 120, whereby the AF control signal Af is obtained.

The outputs from the light receiving elements 30a and 30c are different from each other.
And the AT control signal At is subtracted by the dynamic circuit 119.
Is obtained. Then, normally, this AT control signal At is zero.
AT control is performed so that Optical car shown in FIG.
Two light spots S on Do 1₁ , S₂ Each track
Equal to King Track (group) 54-2, 54-3
On the light receiving elements 30a and 30c
Light spot S_a , S _c Light amount becomes equal. Therefore,
If the AT control signal At is controlled to be zero, the optical card
Light spot S on 1₂ Is Tracking Track 4
It will be located exactly in the center between -2 and 4-3.

By moving the entire head optical system as described above, the information track can be scanned with the light beam spot.

By the way, the optical head optical system as described above is
As shown in FIG. 6, the information track can be scanned with the light beam spot S _b by dividing the fixed portion and the movable portion and moving only the movable portion as shown by the arrow. In such a separation type optical head, the amount of movement of the movable portion needs to be about the length of the optical card 1 in the vertical direction, and is usually about 100 mm.

[0021]

However, in the above-mentioned separation type optical head, it is divided into a fixed portion and a movable portion, and a light beam which becomes parallel light propagates between them, and is adapted to an optical card. If so, the optical path length becomes long.

Therefore, in assembling, adjusting, inspecting and maintaining the same machine, it is possible that a hand or an obstacle is accidentally inserted into the optical path.

Since the light beams are parallel and have a particularly strong power at the time of recording, it is not possible for the light beam to directly illuminate the human body or for the light reflected from an obstacle to enter the eye. There is a risk of damaging the.

[Object of the Invention] The present invention has been made in view of the above points.
When it is determined that the optical path has been interrupted by detecting the optical path condition inside the separable optical head, the generation of the light beam is stopped immediately to prevent damage to the human body, thus providing highly safe optical information. It is to provide a recording / reproducing apparatus.

[0025]

As a means for solving the above problems, the present invention provides a fixed portion composed of an irradiation optical system including a light source and a detection optical system, a reflecting mirror movable with respect to the fixed portion, and an objective. An optical head having a movable part including a condensing optical system including a lens is provided, and information recording / reproduction, focusing control, and tracking control are performed by the optical head on an optical information recording medium having a plurality of tracks. In the optical information recording / reproducing apparatus for recording and reproducing information by irradiating a light spot group for scanning and scanning the track while focusing control and tracking control by reflected light from the light spot group. A plurality of photodetectors for detecting each reflected light from the optical information recording medium of the spot group are provided, and the plurality of photodetectors include a plurality of tracking control Means for detecting whether or not a change in at least one of the signals from the plurality of photodetectors for tracking control is in a predetermined state when the light beam is cut off, and the detection means. An optical information recording / reproducing apparatus comprising: a unit for stopping the light emission of the light source when the predetermined state is detected.

Further, according to the present invention, two signals for tracking control are added from the plurality of photodetectors to generate a tracking sum signal, and whether the change of the tracking sum signal is in a predetermined state when the light beam is cut off. It is also a device provided with a means for detecting whether or not there is any means, and a means for stopping the light emission of the light source when the detecting means detects the predetermined state.

Further, according to the present invention, two signals for tracking control are subtracted from the plurality of photodetectors to generate a tracking difference signal, and whether the change of the tracking difference signal is in a predetermined state when the light beam is cut off. It is also an apparatus provided with a means for detecting whether or not there is any means, and a means for stopping the light emission of the light source when the detecting means detects the predetermined state.

In the present invention, the plurality of photodetectors include a plurality of photodetectors for focusing control, and signals from the plurality of photodetectors for focusing control are added to obtain an information reproduction signal. Means for detecting whether or not the change of the information reproduction signal is in a predetermined state when the light flux is cut off, and means for stopping the light emission of the light source when the detection means detects the predetermined state. It is also an equipped device.

[0029]

According to the present invention, the tracking control signal, the tracking sum signal, the tracking difference signal, or the information reproduction signal to which the focusing control signal is added is monitored, and a signal that appears when the light beam is blocked is detected. The state is set in advance as a predetermined state, and when the predetermined state is detected, the generation of the light beam is immediately stopped, so that the human body or the like can be prevented from being damaged by the light beam.

[0030]

【Example】

Embodiment A Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit block diagram of an embodiment of the present invention. T ₁ and T ₂ are the photodetectors 30a and 30 shown in FIG.
It is the output of c. T ₁ is input to the A / D converter 1 and the comparator 6, and T ₂ is also input to the A / D converter 2 and the comparator 7.

The A / D converters 1 and 2 digitize the signal waveforms of T ₁ and T ₂ and then send them to the MPU 5.

The comparator 6 compares the comparison reference voltage output from the D / A converter 3 with T _1, and creates a binarized output. Similarly, the comparator 7 compares the comparison reference voltage output from the D / A converter 4 with T ₂ and outputs a binarized output. Here, when T ₁ and T ₂ become lower than the comparison reference voltage, it becomes H.

The D / A converters 3 and 4 output the comparison reference voltage according to the data from the MPU 5.

In the MPU 5, after the AF pull-in, the signal waveforms of T ₁ and T ₂ at the time of crossing the track are converted into the A / D converter 1,
Measure through 2 and find each minimum. Furthermore, calculate a voltage value that is lower than each minimum value by a predetermined amount, and use these data as D / A.
Outputs to converters 3 and 4.

The voltage value lower by the predetermined amount is a voltage obtained by subtracting the margin voltage from the minimum value so as not to react with the fluctuation factors such as the reflectance in the optical card and the variation of the contrast.

The outputs of the comparators 6 and 7 are the OR circuit 8
The signal is input to the detection circuit 9 via the, and can be detected even when one of the signals T ₁ and T ₂ is blocked.

The detection circuit 9 outputs the output of H only when the output of the OR circuit 8 becomes H for a predetermined time or more (here, T _b or more shown in FIG. _2B ).
D) Send to 10.

In the LDD 10, the output from the detection circuit 9 is H.
When it changes to, the LD light emission is stopped immediately.

FIG. 2 is a timing chart showing the signal waveforms of FIG.

(A) shows the signal waveforms of T ₁ and T ₂ when a track is crossed after the AF is pulled in.

(B) shows the respective signal waveforms when the light flux cutoff of T ₁ occurs.

The operation of the embodiment will be described below with reference to FIG.

First, the initial setting operation performed every time the optical card is inserted will be described.

AF insertion is performed after the optical card is inserted,
The AF servo state is set. Details of this operation are omitted because they are not directly related to the present invention.

Next, the MPU 5 drives a tracking actuator (not shown) in the track crossing direction to drive T ₁ , T 2.
Generate track crossing signal to ₂ .

FIG. 2A shows the signal waveforms of T ₁ and T ₂ at this time. When each tracking spot is on the tracking track, the minimum value of each of T ₁ and T ₂ is V. _min , and the maximum value V _max when it is on the data track.

The MPU 5 performs the above-mentioned operation and
The track crossing signal waveforms generated at T ₁ and T ₂ are read as digital data via the A / D converters 1 and 2.

The MPU 5 finds the minimum value of each of T ₁ and T ₂ from the read digital data.

FIG. 2A shows the case where both T ₁ and T ₂ are at the same level, but T ₁ and T ₂ are optical, that is, the size of the beam diameter, and the 0th and 1st order light distribution ratios of the grating. The actual value will differ due to variations in the
The minimum value is calculated for each of T ₁ and T ₂ .

Next, the MPU 5 calculates a voltage by subtracting the above-mentioned margin voltage: V ₀ from each minimum value, and the voltage is D /
Each digital data is set so as to be output from the A converters 6 and 7.

After that, the AT pull-in is performed and the AT servo state is established. Details of this operation are omitted because they do not directly relate to the present invention.

At this stage, the initial setting operation is completed. Next, with reference to FIG. 2B, the operation when the light flux is blocked will be described.

In the figure, the case where the light flux of the spot on the T ₁ side is blocked is shown as a representative.

When the initial setting operation is completed, the AT servo state is established and T ₁ maintains the value of V _c which is the target value of the AT servo.

Here, in the D / A converter 6, the minimum value of T ₁ obtained in the initial setting: V _min to the margin voltage: V ₀
The reference voltage for comparison: V _r is set.

In FIG. 2B, the symbol, indicates the case where there is a defect or the like on the tracking guide of the optical card.

Since the defect of (1) does not reach V _r , it does not appear in the signal A which is the input signal of the detector 9. One of the defects exceeds V _r , and the signal A has a pulse width T _a . However, the detector 9 causes T _a <T _b
Since it is not determined that the light beam is blocked, it is not output to the signal B output from the detector 9.

[0059] is the case where the light beam is interrupted, but, V _r
And the pulse width of the signal A also exceeds T _{b, the} signal B is H
Then, the LD light emission stop signal is sent to the LDD 10 to stop the LD light emission.

As described above, even if the detector 9 has a defect on the optical card, the LD emission can be stopped only when the light flux is blocked without erroneous detection.

During recording, the tracking control light spots S _a and S _c are also modulated in light intensity in the same manner as the recording light light spot S _b is modulated by the recording pulse.

Therefore, when the recording pulse is emitted, T
The absolute value levels of ₁ and T ₂ increase by the light intensity modulation.

For this reason, the sensitivity for blocking a predetermined amount of light flux becomes low. However, there is no problem because the above-described light beam cutoff detection is performed between recording pulses.

Examples of the detection circuit 9 include a method using the MPU 5 and a method using a dedicated IC such as a retriggerable monostable multivibrator.

An example of the former case is shown in FIG.

In the figure, 31 is a rising edge detector, 32 is a falling edge detector, and 33 is a counter.
When CLK receives a start signal, it counts up and outputs when it reaches the same count value as the preset count value.

The operation will be described below.

When the rising edge detector 31 detects a rising edge, the counter 33 is started. The counter 33 counts up the basic clock: CLK, and sets the out port 34 from L to H when the count value becomes equal to the preset count value.

However, if the falling edge detector 32 detects a falling edge before the count value reaches the preset count value, a reset signal is sent to the counter 33.
The counter 33 stops counting and clears the counter value at that time, and then waits for the next start signal input.

In this way, a detection circuit is constructed which does not output a pulse for a predetermined time T _b or less determined by the preset count value and the basic clock: CLK.

The above-mentioned components are generally incorporated in the MPU, and the configuration and operation of these components can be easily constructed by software.

<Other Embodiment A> In the above-mentioned embodiment, the minimum value of the track crossing signals of T ₁ and T ₂ is measured every time the optical card is inserted, but when the variation in the characteristics of the optical card is small. Measures the above with an optical card that has standard characteristics when adjusting the device in advance.
It is also possible to shorten the time by storing the data in a non-volatile memory such as OM or EEPROM and omitting the measurement during the initial setting operation.

[Embodiment B] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 8 is a circuit block diagram of an embodiment of the present invention. T ₁ and T ₂ are the photodetectors 30a and 30 shown in FIG.
The output of c is input to the adder circuit 11 and added output ATadd
Becomes ATadd is input to the A / D converter 1 and the comparator 6.

The A / D converter 1 digitizes the signal waveform of ATadd and sends it to the MPU 5.

Comparator 6 is from D / A converter 3
Output comparison reference voltage: V_r And T ₁ Compare with and binary
Create the verbose output.

Here, when ATadd becomes lower than the comparison reference voltage, it becomes H.

The D / A converter 3 outputs the comparison reference voltage: V _r according to the data from the MPU 5.

After pulling in the AF, the MPU 5 measures the signal waveform of ATadd at the time of crossing the track via the A / D converter 1 to obtain the minimum value. Further, a voltage lower than the minimum value by a predetermined amount is calculated, and these data are output to the D / A converter 3.

The voltage value lower by the predetermined amount is a voltage obtained by subtracting the margin voltage for not reacting to the fluctuation factors such as the reflectance in the optical card and the variation of the contrast from the minimum value.

The output of the comparator 6 is input to the detection circuit 9.

The detection circuit 9 sends the output of H to the LDD (LDD, LD driver) 10 only when the output of the comparator 6 becomes H for a predetermined time (here, T _b ).

The LDD 10 outputs the output from the detection circuit 9 at H level.
When it changes to, the LD (laser: hereinafter LD) light emission is stopped immediately.

FIG. 9 is a timing chart showing the signal waveforms of FIG.

(A) shows an ATadd signal waveform when a track is crossed after the AF is pulled in.

(B) is ATa in the case where the light flux is blocked.
The dd signal waveform is shown.

The operation of the embodiment will be described below with reference to FIG.

First, the initial setting operation performed each time the optical card is inserted will be described.

AF insertion is performed after the optical card is inserted,
The AF servo state is set. Details of this operation are omitted because they are not directly related to the present invention.

Next, the MPU 5 drives a tracking actuator (not shown) in the track crossing direction to set T ₁ , T 2.
Generate track crossing signal to ₂ .

FIG. 9A shows the waveform of the sum signal ATadd of T ₁ and T ₂ at this time. When each tracking spot is on the tracking track, the AT
The minimum value of add is V _min , and the maximum value is V _max when it is on the data track.

The MPU 5 performs the above-mentioned operation and
The track crossing signal waveform generated at ATadd is read as digital data via the A / D converter 1.

The MPU 5 obtains the minimum value of ATadd from the read digital data.

Next, the MPU 5 calculates a voltage obtained by subtracting the above-mentioned margin voltage: V ₀ from the obtained minimum value, and sets digital data so that the same voltage is output from the D / A converter 3.

After that, AT pull-in is performed and the AT servo state is established. Details of this operation are omitted because they do not directly relate to the present invention.

At this stage, the initial setting operation is completed. Next, with reference to FIG. 9B, the operation when the light flux is blocked will be described.

When the initial setting operation is completed, the AT servo state is established, and ATadd maintains the value of V _c .

[0098] The here D / A converter 3, the minimum value of ATadd determined by default: margin voltage from V _{mi n:} comparison reference voltage minus V _0: V _r is set.

In FIG. 9B, the symbol, indicates that there is a defect or the like on the tracking guide of the optical card.

In the defect of V, since it has not reached V _r , it does not appear in the signal A input to the detector 9. One of the defects exceeds V _r and causes the signal A to have a pulse width T _a . However, since the detector 9 does not determine that T _a <T _{b and the} light flux is not blocked, it is not output to the signal B output from the ticket type attaching unit 9.

In the case where the light flux is blocked, V _r
And the pulse width of the signal A also exceeds T _b , the signal B becomes H, and the LD light emission stop signal is sent to the LDD 10.
Stops emitting light.

As described above, even if the detector 9 has a defect on the optical card, the LD light emission can be stopped only when the light flux is blocked without erroneous detection.

During recording, the tracking control light spots S _a and S _c are also modulated in light intensity in the same manner as the recording light spot S _b is modulated by the recording pulse.

Therefore, when the recording pulse is emitted, the AT
The absolute value level of add increases by the light intensity modulation.

For this reason, the sensitivity to blocking a predetermined amount of light flux becomes low. However, there is no problem because the above-described light beam cutoff detection is performed between recording pulses.

Examples of the detection circuit 9 include a method using the MPU 5 and a method using a dedicated IC such as a retriggerable monostable multivibrator.

An example of the former case is shown in FIG.

In the figure, 31 is a rising edge detector, 32 is a falling edge detector, and 33 is a counter.
When CLK receives a start signal, it counts up and outputs when it reaches the same count value as the preset count value.

The operation will be described below.

When the rising edge detector 31 detects a rising edge, the counter 33 is started. The counter 33 counts up the basic clock: CLK, and sets the out port 34 from L to H when the count value becomes equal to the preset count value.

However, if the falling edge detector 32 detects a falling edge before the count value reaches the preset count value, a reset signal is sent to the counter 33.
The counter 33 stops counting and clears the counter value at that time, and then waits for the next start signal input.

In this way, a detection circuit that does not output a pulse for a predetermined time T _b or less determined by the preset count value and the basic clock: CLK is constructed.

The above-mentioned components are generally incorporated in the MPU, and the configuration and operation of these components can be easily constructed by software.

<Other Embodiment B> In the above-mentioned embodiment, the minimum value of the track crossing signal of ATadd was measured every time the optical card was inserted. Perform the above measurement with an optical card that has standard characteristics when adjusting
It is also possible to shorten the time by storing the data in a non-volatile memory such as OM or EEPROM and omitting the measurement during the initial setting operation.

[Embodiment C] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 10 is a circuit block diagram of an embodiment of the present invention. A _t is the tracking difference signal Hesi photodetectors 30a, the output of 30c shown in FIG. A _t the A / D
Input to the converter 1 and the comparators 6 and 7.

[0117] A / D converter 1 after digitizing the signal waveform of the A _t, and sends it to the MPU 5.

Comparator 6 is from D / A converter 3
Output comparison reference voltage: V_r1And A _t Compare with and binary
Create the verbose output. Similarly, the comparator 7 is a D / A converter.
Comparative reference voltage output from the barter 4: V_r2And A_t And
It compares and outputs the binarized output.

The D / A converters 3 and 4 output the comparison reference voltage according to the data from the MPU 5.

[0120] In MPU 5, after pulling AF, the signal waveform of the A _t the time of track crossing is measured through the A / D converter 1, obtain the maximum and minimum value. Further, a voltage value lower than the minimum value by a predetermined amount and a voltage value higher than the maximum value by a predetermined amount are calculated, and these data are output to the D / A converters 3 and 4.

The predetermined voltage value is a voltage obtained by subtracting the margin voltage from the minimum value or adding it to the maximum value so as not to react with the fluctuation factors such as the reflectance in the optical card and the variation of the contrast.

The outputs of the comparators 6 and 7 are input to the detection circuit 9 via the OR circuit 8 and can be detected even when either one of the signals is blocked by the light beam.

The detection circuit 9 outputs the output of H to L only when the output of the OR circuit 8 becomes H for a predetermined time (here, T _b ).
It is sent to the DD (LD driver LDD) 10.

The LDD 10 outputs the output from the detection circuit 9 at H level.
When it changes to, the LD light emission is stopped immediately.

FIG. 11 is a timing chart showing each signal waveform of FIG.

[0126] (A) after retraction AF, shows the signal waveforms of A _t the time of the track crossing.

(B) shows respective signal waveforms when the light flux cutoff of T ₁ occurs.

The operation of the embodiment will be described below with reference to FIG.

First, the initial setting operation performed each time the optical card is inserted will be described.

AF insertion is performed after the optical card is inserted,
The AF servo state is set. Details of this operation are omitted because they are not directly related to the present invention.

Next, the MPU 5 drives a tracking actuator (not shown) in the track crossing direction to generate a track crossing signal at A _t .

[0132] (A) of FIG. 11 shows the signal waveforms of A _t this time, if either of the tracking spot is on the tracking tracks, A _t is the minimum value V
_min or the maximum value V _max .

The MPU 5 performs the above-mentioned operation,
A track crossing signal waveforms occurring in A _t through the A / D converter 1, read as digital data.

[0134] MPU5 from digital data read up to the A _t, find the minimum value.

Next, the MPU 5 calculates a voltage by subtracting the above-mentioned margin voltage: V ₀ from the obtained minimum value, and sets digital data so that the same voltage is output from the D / A converter 3.

Similarly, the MPU 5 calculates a voltage obtained by adding the above-mentioned margin voltage: V ₀ from the obtained maximum value, and sets digital data so that the same voltage is output from the D / A converter 4.

After that, AT pull-in is performed and the AT servo state is established. Details of this operation are omitted because they do not directly relate to the present invention.

At this stage, the initial setting operation is completed. Next, with reference to FIG. 11B, an operation when the light flux is blocked will be described.

In the figure, the case where the light flux of the spot on the T ₁ side is blocked is shown as a representative.

[0140] When the initial setting operation is completed becomes the AT servo state, A _t is maintained the value of V _c is a target value of the AT servo.

Here, in the D / A converter 3, from the minimum value A _t of the initial setting: V _min to the margin voltage V _0.
The subtracted comparison reference voltage: V _r is set.

In FIG. 11B, the symbol, indicates that there is a defect or the like on the tracking guide of the optical card.

In the defect of (1), since it has not reached V _r1 , it does not appear in the signal A input to the detector 9. One of the defects exceeds V _r1 and produces _a signal A with a pulse width T _a . However, since T _a <T _b is not determined by the detector 9 and it is not determined that the light beam is blocked, it is not output to the signal B output from the detector 9.

In the case where the optical path is blocked, V _r1
And the pulse width of the signal A also exceeds T _{b, the} signal B is H
Then, the LD light emission stop signal is sent to the LDD 10 to stop the LD light emission.

As described above, even if the detector 9 has a defect on the optical card, it is possible to stop the LD emission only when the light flux is cut off without erroneous detection.

The above is T₁ When the optical path on the side is blocked
I explained about it, but T₂ If the spot on the side is blocked
However, the same operation is performed. However, in that case, the comparison reference voltage
Is V _r2Be on the side.

Further, at the time of recording, the tracking control light spots S _a and S _c are also light intensity modulated in the same manner as the recording light light spot S _b is light intensity modulated by the recording pulse, but the light path is blocked. If a _t signal is not, the offset light intensity variation, the output does not fluctuate.

When the optical path is blocked, the same detection as above can be performed.

However, as the light intensity becomes higher, the gain becomes higher, so that it becomes easier to make an erroneous detection for a medium defect or the like.

FIG. 12 shows an embodiment for solving such a problem at the time of recording.

In FIG. 12, the variable gain amplifier 12 shown in FIG.
This is an example improved by inserting the, and other points are the same as in FIG. The variable gain amplifier becomes through with the recording pulse WP with a low gain and the like. If the ratio between the low gain and the gain 1 is made equal to the light intensity modulation ratio for making the recording pulse, the output of the variable gain amplifier 10 does not show the influence of the light intensity modulation by the recording pulse, and therefore stable optical path cutoff detection is performed. Can be done.

That is, during the information recording operation, by switching the signal gains from a plurality of photodetectors within the period of the recording pulse and outside the period, the influence of the recording pulse can be corrected and input to the detecting means. You can do it.

Examples of the detection circuit 9 include a method using the MPU 5 and a method using a dedicated IC such as a retriggerable monostable multivibrator.

An example of the former case is shown in FIG.

In the figure, 31 is a rising edge detector, 32 is a falling edge detector, and 33 is a counter.
When CLK receives a start signal, it counts up and outputs when it reaches the same count value as the preset count value. The operation will be described below.

When the rising edge detector 31 detects a rising edge, the counter 33 is started. The counter 33 counts up the basic clock: CLK, and sets the out port 34 from L to H when the count value becomes equal to the preset count value.

However, if the falling edge detector 32 detects a falling edge before the count value reaches the preset count value, a reset signal is sent to the counter 33.
The counter 33 stops counting and clears the counter value at that time, and then waits for the next start signal input.

In this way, the detection circuit which does not output the pulse for the predetermined time T _b or less determined by the preset count value and the basic clock: CLK is constructed.

The above-mentioned components are generally incorporated in the MPU, and the configuration and operation of these components can be easily constructed by software.

[0160] In <Other Example C> embodiments described above, but the maximum and minimum value of the track crossing signal per inserted optical card A _t was measured, in the case variations in the characteristics of the optical card is small, Perform the above measurement in advance with an optical card having standard characteristics when adjusting the device, etc.
It is also possible to shorten the time by storing data in a non-volatile memory such as M or EEPROM and omitting the measurement during the initial setting operation.

[Embodiment D] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 13 is a circuit block diagram of an embodiment of the present invention. RF is an information reproduction signal by adding the respective outputs of the focusing control photodetector 30b shown in FIG. RF
Is input to the A / D converter 1 and the comparator 6.

The A / D converter 1 digitizes the RF signal waveform and sends it to the MPU 5.

The comparator 6 compares the comparison reference voltage V _r output from the D / A converter 3 with RF and creates a binarized output. Here, when RF becomes lower than the comparison reference voltage, it becomes H.

The D / A converter 3 outputs the comparison reference voltage: V _r according to the data from the MPU 5.

After the AF pull-in, the MPU 5 measures the RF signal waveform at the time of crossing the track and the signal waveform of the preformatted pit reproduction through the A / D converter 1 to obtain each minimum value. Further, the lowest value among them is set as the minimum value, a voltage value lower than the minimum value by a predetermined amount is calculated, and these data are output to the D / A converter 3.

The predetermined voltage value is a voltage obtained by subtracting a margin voltage from the minimum value so as not to react with variable factors such as reflectance in the optical card and variations in preformatted pit recording pits.

The output of the comparator 6 is input to the detection circuit 9.

The detection circuit 9 sends the H output to the LDD (LD driver and LDD) 10 only when the output of the comparator 6 becomes H for a predetermined time (here, T _b ).

The output from the detection circuit 9 of the LDD 10 is H level.
When it changes to, the LD (laser, hereinafter LD) light emission is stopped immediately.

FIG. 14 is a timing chart showing each signal waveform of FIG.

(A) shows the RF signal waveform (a) and the RF signal waveform (b) of the pre-format pit when the track is crossed after the AF pull-in.

(B) shows the RF signal waveform when the light flux is blocked.

The operation of the embodiment will be described below with reference to FIG.

First, the initial setting operation performed each time the optical card is inserted will be described.

AF insertion is performed after inserting the optical card,
The AF servo state is set. Details of this operation are omitted because they are not directly related to the present invention.

Next, the MPU 5 drives a tracking actuator (not shown) in the track crossing direction to generate a track crossing signal in RF.

(A) in FIG. 14A shows R at this time.
The signal waveform of F is shown. The minimum value of RF is V _min1 when each focusing spot is on the tracking track, and the maximum value V _max is when it is on the data track.

The MPU 5 performs the above-mentioned operation,
The track crossing signal waveform generated in RF is read as digital data via the A / D converter 1.

The _{MPU 5} obtains the minimum value V _{min1 of} RF from the read digital data.

After that, the AT pull-in is performed, the AT servo state is set, and the preformat reproduction is performed.

The details of this operation are directly related to the present invention.
Omitted because it does not give. At this time, (b) of (A) of FIG.
The RF signal waveform of the
If the pot is on the pre-format pit, the RF
The minimum value is V _min2And if it is on the data track
Maximum value is V_max Becomes

The MPU 5 performs the above-mentioned operation,
The RF signal waveform of the preformatted pit generated in RF is read as digital data via the A / D converter 1.

The MPU 5 obtains the minimum value V _{min2 of} RF from the read digital data.

Next, the MPU 5 calculates the minimum value V _min1 ,
Compare V _min2 and select the smaller one as the minimum value,
A voltage is calculated by subtracting the above-mentioned margin voltage: V ₀ from this value, and digital data is set so that the voltage value is output from the D / A converter 3.

At this stage, the initial setting operation is completed.

In the present embodiment, the minimum values of RF when reproducing the pre-format pit and the recording pit are almost equal. That is, it is assumed that the contrast is about the same. Therefore, if the recording pit has a smaller value than the preformatted pit, it is necessary to add the difference to the above-mentioned margin voltage: V ₀ and subtract the voltage from the selected minimum value.

The operation when the light beam is blocked will be described with reference to FIG.

When the initial setting operation is completed, RF maintains the value of V _{max in} the AT servo state.

Here, the D / A converter 3 has a margin voltage: V ₀ from the minimum value of RF: V _min2 obtained in the initial setting.
The reference voltage for comparison: V _r is set.

In FIG. 14B, the symbol, indicates that there is a defect or the like on the data track of the optical card.

In the defect of (1), since it has not reached V _r , it does not appear in the signal A input to the detector 9. One of the defects exceeds V _r , and the signal A has a pulse width T _a . However, since the detector 9 does not determine that T _a <T _{b and the} light beam is not blocked, the signal B is not output.

In the case where the light beam is blocked, V _r
And the pulse width of the signal A also exceeds T _b , the signal B becomes H, and the LD light emission stop signal is sent to the LDD 10.
Stops emitting light.

As described above, the detector 9 can stop the LD light emission only when the light beam interruption occurs without erroneous detection even when there is a defect on the optical card.

Further, at the time of recording, the light spot S _b for recording light is light intensity modulated by the recording pulse.

When recording pits are generated by the recording pulse, the reflectance of the medium is significantly reduced.

Therefore, when the intensity ratio of the reflected light from the medium is larger than the intensity ratio of the light applied to the medium, the recording light may cause an erroneous detection.

FIG. 15 shows an embodiment for solving such a problem at the time of recording.

FIG. 15 is a block diagram of the variable gain amplifier 12 shown in FIG.
This is an example improved by inserting the, and other points are the same as in FIG. The variable gain amplifier 12 passes through the recording pulse WP with the gain G and others. If the ratio of the gain G to the gain 1 is made equal to the light intensity modulation ratio of the reflected light from the medium to be the recording pulse, the output of the variable gain amplifier 12 does not show the influence of the light intensity modulation by the recording pulse. The stable optical path interruption detection can be performed.

That is, during the information recording operation, the influence of the recording pulse can be corrected and input to the detecting means by switching the signal gains from the plurality of photodetectors within the period of the recording pulse and outside the period. You can do it.

Examples of the detection circuit 9 include a method using the MPU 5 and a method using a dedicated IC such as a retriggerable monostable multivibrator.

An example of the former case is shown in FIG.

In the figure, 31 is a rising edge detector, 32 is a falling edge detector, and 33 is a counter.
When CLK receives a start signal, it counts up and outputs when it reaches the same count value as the preset count value.

The operation will be described below.

When the rising edge detector 31 detects a rising edge, the counter 33 is started. The counter 33 counts up the basic clock: CLK, and sets the out port 34 from L to H when the count value becomes equal to the preset count value.

However, if the falling edge detector 32 detects a falling edge before the count value reaches the preset count value, a reset signal is sent to the counter 33.
The counter 33 stops counting and clears the counter value at that time, and then waits for the next start signal input.

In this way, the detection circuit that does not output the pulse for the predetermined time T _b or less determined by the preset count value and the basic clock: CLK is constructed.

Each of the above components is generally incorporated in the MPU, and the configuration and operation of these can be easily constructed by software.

<Other Embodiment D> In the above-described embodiment, the minimum value of the RF track crossing signal and the preformatted RF signal is measured every time the optical card is inserted, but the variation in the characteristics of the optical card is small. In this case, the above measurement is performed in advance with an optical card having standard characteristics when adjusting the device, and the data is stored in a non-volatile memory such as EPROM or EEPROM, and the above measurement during the initial setting operation is performed. It is possible to shorten the time by omitting it.

[0210]

EFFECT OF THE INVENTION [Effect A] As described above, in the optical information recording / reproducing apparatus using the separation type optical head, when the tracking control signal is kept below the predetermined level and for the predetermined time,
By judging that the light flux has been blocked and immediately stopping the LD emission, even when the hand or obstacle is accidentally inserted into the optical path during the assembly, adjustment, inspection and maintenance of the machine, damage to the human body will occur. Therefore, the safety of the device can be dramatically improved.

[Effect B] As described above, in the optical information recording / reproducing apparatus using the separate type optical head, when the tracking sum signal is below the predetermined level and kept for the predetermined time, it is judged that the light flux is blocked. However, by stopping the LD light emission immediately, it is possible to prevent damage to the human body even if a hand or an obstacle is accidentally inserted into the optical path during the assembly, adjustment, inspection, or maintenance of the aircraft, Therefore, the safety of the device can be dramatically improved.

[Effect C] As described above, in the optical information recording / reproducing apparatus using the separation type optical head, when the tracking difference signal is maintained for a predetermined time exceeding the predetermined level range, the light beam is blocked. By making a judgment and immediately stopping the LD light emission, it is possible to prevent damage to the human body even if a hand or an obstacle is accidentally inserted into the optical path during assembly, adjustment, inspection or maintenance of the machine. Therefore, the safety of the device can be dramatically improved.

[Effect D] As described above, in the optical information recording / reproducing apparatus using the separation type optical head, when the information reproducing signal obtained by adding the focusing control signal is kept below the predetermined level for the predetermined time. It is judged that the light flux has been cut off, and by immediately stopping the LD light emission, the human body is damaged even if a hand or an obstacle is accidentally inserted in the optical path during the assembly, adjustment, inspection and maintenance of the machine. It is possible to prevent the occurrence of such a problem, and thus the safety of the device can be dramatically improved.

[Brief description of drawings]

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

FIG. 2 is a timing chart of an embodiment of the present invention.

3 is a circuit block diagram of an embodiment of the detector of FIG. 1 of the present invention.

FIG. 4 is a schematic plan view of a write-once optical card.

FIG. 5 is a partially enlarged view of the write-once optical card.

FIG. 6 is a schematic diagram of an optical head optical system.

FIG. 7 is a block diagram of a photodetector and a control signal generation circuit of the optical information recording / reproducing device.

FIG. 8 is a circuit block diagram of an embodiment of the present invention.

FIG. 9 is a timing chart of an example of the present invention.

FIG. 10 is a circuit block diagram of an embodiment of the present invention.

FIG. 11 is a timing chart of an example of the present invention.

FIG. 12 is a block diagram of another embodiment of the present invention.

FIG. 13 is a circuit block diagram of an embodiment of the present invention.

FIG. 14 is a timing chart of an example of the present invention.

FIG. 15 is a block diagram of another embodiment of the present invention.

[Explanation of symbols]

 1, 2 A / D converter 3, 4 D / A converter 6, 7 comparator 8 OR circuit 9 detection circuit 10 LDD 5 MPU 11 adder circuit

Claims (14)

[Claims] 1. An optical head comprising a fixed portion including an irradiation optical system including a light source and a detection optical system, and a movable portion movable relative to the fixed portion and including a condensing optical system including a reflection mirror and an objective lens. And irradiating an optical information recording medium having a plurality of tracks from the optical head with a light spot group for recording and reproducing information, focusing control and tracking control,
In an optical information recording / reproducing apparatus that records and reproduces information by scanning the track while focusing control and tracking control by reflected light from the light spot group, A plurality of photodetectors for detecting the respective reflected lights of the plurality of photodetectors, wherein the plurality of photodetectors include a plurality of photodetectors for tracking control, and the signals from the plurality of photodetectors for tracking control are included. A means for detecting whether a change in at least one of the signals is in a predetermined state when a light beam is blocked, and stopping the light emission of the light source when the detecting means detects the predetermined state. An optical information recording / reproducing apparatus comprising: 2. The predetermined state is such that the signal levels from the plurality of photodetectors for tracking control are for a predetermined time or more,
The optical information recording / reproducing apparatus according to claim 1, wherein the optical information recording / reproducing apparatus is a case where the optical information recording / reproducing apparatus has a predetermined level or less. 3. The optical information recording / reproducing apparatus according to claim 2, wherein the predetermined level is smaller than a minimum value of a signal level when the plurality of photodetectors for tracking control cross a track. 4. A tracking sum signal is generated by adding two signals for tracking control from the plurality of photodetectors, and a change in the tracking sum signal is a predetermined state when a light flux is blocked. The optical information recording device according to claim 1, further comprising: a means for detecting whether or not the light source is turned off, and a means for stopping the light emission of the light source when the detection means detects the predetermined state. Playback device. 5. The optical information recording / reproducing apparatus according to claim 4, wherein the predetermined state is a case where the tracking sum signal level is not lower than a predetermined level for a predetermined time or longer. 6. The optical information recording / reproducing apparatus according to claim 5, wherein the predetermined level is smaller than a minimum value of a signal level when the tracking sum signal crosses a track. 7. A tracking difference signal is generated by subtracting two tracking control signals from the plurality of photodetectors, and a change in the tracking difference signal is a predetermined state when a light beam is blocked. The optical information recording device according to claim 1, further comprising: a means for detecting whether or not the light source is turned off, and a means for stopping the light emission of the light source when the detection means detects the predetermined state. Playback device. 8. The optical information recording / reproducing apparatus according to claim 7, wherein the predetermined state is a case where the tracking difference signal level exceeds a predetermined level range for a predetermined time or more. 9. The optical information recording / reproducing apparatus according to claim 8, wherein the predetermined level range is a range of a maximum value and a minimum value of a signal level when the tracking difference signal crosses a track. 10. An apparatus in which the light spot group is generated by dividing light emitted from a single light source, and information is recorded on the optical information recording medium by intensity-modulating the light emitted by a recording pulse. During the information recording operation, it is possible to correct the influence of the recording pulse by inputting to the detecting means by switching the signal gain from the plurality of photodetectors within the period of the recording pulse and outside the period. The optical information recording / reproducing apparatus according to claim 7, which is characterized in that. 11. The plurality of photodetectors include a plurality of photodetectors for focusing control, wherein signals from the plurality of photodetectors for focusing control are added to generate an information reproduction signal, Means for detecting whether or not the change in the information reproduction signal is in a predetermined state when a light flux is preset, and means for stopping the light emission of the light source when the detecting means detects the predetermined state. Claim 1 characterized by the fact that it is provided.
The optical information recording / reproducing apparatus described in 1. 12. The optical information recording / reproducing apparatus according to claim 11, wherein the predetermined state is a case where the information reproduction signal level is not lower than a predetermined level for a predetermined time or longer. 13. The predetermined level is smaller than the smallest value of the signal level when the information reproduction signal crosses tracks, the preformatted pit, and the signal level when the recording pit is reproduced. Claim 1
2. The optical information recording / reproducing apparatus described in 2. 14. A device in which the light spot group is generated by dividing light emitted from a single light source, and information is recorded on the optical information recording medium by intensity-modulating the light emitted by a recording pulse. During the information recording operation, it is possible to correct the influence of the recording pulse and input it to the detecting means by switching the signal gain from the plurality of photodetectors within the period of the recording pulse and outside the period. The optical information recording / reproducing apparatus according to claim 11, which is characterized in that: