JP4417408B2 - Optical disk device - Google Patents

Description

  The present invention relates to an optical disk apparatus that optically handles recorded contents on a recording medium such as an optical disk or a magneto-optical disk.

  Conventionally, reading of recorded contents from optical discs such as compact discs (CD), laser discs (LD) and digital video discs (DVD), and magneto-optical discs such as mini discs (MD) and magneto-optical discs (MO). In addition, handling of writing of recorded contents on CD-R, CD-RW, DVD-RAM, and the like is optically performed by an optical disc apparatus including an optical pickup. In an optical disk apparatus, an optical disk or a magneto-optical disk is mounted on a turntable and rotated, and the recorded content is read and written while controlling the focus servo and tracking servo for the optical pickup. Therefore, when the optical disk apparatus handles a disk-shaped recording medium such as an optical disk or a magneto-optical disk, it is necessary to detect whether or not the optical disk is loaded on the turntable.

  An optical pickup can be used for detecting the presence or absence of the optical disk. For example, in Japanese Patent Laid-Open No. 4-79032 and Japanese Patent Laid-Open No. 6-203467, whether or not there is a change corresponding to the detection of the optical disc in the amount of light received by the detector while moving the lens and changing the focus of the optical pickup is examined. Prior art for determining that an optical disc is loaded is disclosed. In these prior arts, the presence / absence of an optical disc is detected as part of focus adjustment.

  FIG. 11 schematically shows the light receiving surface 1 of the detector of the optical pickup. The light-receiving surface 1 is divided into four, and is divided into two sets of regions A and B that are diagonal to each other. The shape of the incident light 2 from the optical disk incident through the lens changes as shown in FIGS. 11A, 11B, and 11C in accordance with the positional relationship between the reflecting surface, the lens, and the light receiving surface 1 of the optical disk. To form an image on the light receiving surface 1. FIG. 11C shows a state where the optical system is in focus.

  FIG. 12 shows a change in the level of the detector output signal corresponding to the amount of reflected light incident on A and B of the light receiving surface 1 in accordance with the change in focus, and a change in the level of the total signal, which is the sum of reflected light amounts of A + B. In the state of FIG. 11A, the signal level of A is large, and in the state of FIG. 11B, the signal level of B is large. In FIG. 11C, the signal level is A = B, and the total signal level of A + B is also maximum. Therefore, the presence / absence of the optical disc can be determined based on whether or not the total signal level changes so as to show a peak.

  In Japanese Patent Laid-Open No. 4-79032 described above, if a zero cross where the level of the focus error signal, which is the difference between A and B, becomes zero is detected, it is determined that an optical disk is present. In JP-A-6-203467, the number of changes in the focus error signal level is counted, and if an S-curve waveform corresponding to the transparent layer and the reflective recording layer on the optical disk surface is detected, it is determined that the optical disk is present.

  To determine whether or not the above total signal shows a peak, set a reference level that is higher than the total signal level when out of focus and lower than the total signal level when focused. Is possible. The above-described detection of the zero cross and S curve of the focus error signal is also based on the premise that there are peaks before and after the zero cross, and it is necessary to set and compare a reference level in order to detect the peaks.

  When the presence or absence of a peak is determined by comparison with a reference level, for example, if the slice level FOKLEV indicated by the alternate long and short dash line in FIG. 12 is the reference level of the total signal, it can be clearly determined that there is a peak. However, for example, due to a temperature change, the DC offset of a detector or an amplifier that amplifies the output may increase. When the DC offset component in the signal level increases and the relative relationship with the reference level changes, the total signal level always becomes higher than the reference level, for example, as shown by a two-dot chain line in FIG. There is a risk that. In such a state, even if the optical disc is not loaded, it is detected that it is loaded. Even though the optical disk is not actually loaded, it is determined that the optical disk apparatus is loaded, which may cause malfunction of the optical disk apparatus.

  An object of the present invention is to provide an optical disc apparatus that does not cause a malfunction even if a signal level fluctuates due to a DC offset of a detector or an amplifier.

The present invention provides an optical disc apparatus that determines the presence or absence of an optical disc based on the amount of light incident from the optical system when the optical system is swept along the optical axis.
A memory circuit for storing the level of a signal representing the amount of incident light before sweeping the optical system;
A maximum value detection circuit for detecting the maximum value of the signal level indicating the incident light amount during the sweep of the optical system;
After sweeping the optical system, the level of the signal stored in the memory circuit is compared with the level of the signal detected by the maximum value detection circuit, and when the level difference between the signals is within a preset range, An optical disk apparatus comprising: a determination circuit that determines that there is no optical disk.

  According to the present invention, when the optical disc is loaded, the level of the signal representing the incident light amount reaches a peak when the optical disc is in focus and is detected as the maximum value by the maximum value detection circuit during the sweep of the optical system. The The maximum value corresponding to the peak is not substantially in the same range as the signal representing the amount of incident light stored in the memory circuit before the sweep of the optical system, and a considerable difference occurs. When the optical disc is not loaded, the signal level stored in the memory and the maximum value are in the same range. Since the comparison between the two levels is performed relatively, even if the level of the signal representing the incident light amount is affected by a DC offset or the like, it is possible to make a reliable determination as to the presence or absence of the optical disc and prevent erroneous detection. .

Furthermore, the present invention provides an optical disc apparatus that determines the presence or absence of an optical disc based on the amount of light incident from the optical system when the optical system is swept along the optical axis.
A maximum value detection circuit for detecting the maximum value of the signal level indicating the incident light amount during the sweep of the optical system;
After sweeping the optical system, the level of the signal representing the amount of incident light is compared with the level of the signal detected by the maximum value detection circuit, and there is no optical disc when the level difference between the signals is within a preset range An optical disc apparatus including a determination circuit for determining

  According to the present invention, when the optical disc is loaded, the level of the signal representing the incident light amount reaches a peak when the optical disc is in focus and is detected as the maximum value by the maximum value detection circuit during the sweep of the optical system. The The maximum value corresponding to the peak is not substantially in the same range as the signal indicating the incident light quantity after sweeping of the optical system, and a considerable difference occurs. When the optical disk is not loaded, the level of the signal indicating the incident light quantity after the sweep and the maximum value are substantially in the same range. Since the comparison between the two levels is performed relatively, even if the level of the signal representing the incident light amount is affected by a DC offset or the like, it is possible to make a reliable determination as to the presence or absence of the optical disc and prevent erroneous detection. .

  According to the present invention, since the relative level of the signal representing the incident light amount is compared between the optical system before sweeping and the highest value during the sweep, the level of the signal representing the incident light amount is affected by a DC offset or the like. Even if it occurs, it is possible to make a reliable determination as to whether or not there is an optical disc and prevent erroneous detection.

  According to the present invention, since the relative level of the signal representing the incident light amount is compared between the highest value during the sweep of the optical system and after the sweep, the level of the signal representing the incident light amount is influenced by a DC offset or the like. Even if it occurs, it is possible to make a reliable determination as to whether or not there is an optical disc and prevent erroneous detection.

  FIG. 1 shows a schematic electrical configuration of an optical disc apparatus 10 as a first reference example of the present invention. Incident light 12 that forms an image on the light receiving surface 11 is reflected light that reflects the laser light generated from the laser light source 13 by the half mirror 14 and is irradiated through the lens 15. The detector having the light receiving surface 11 divided into four, the laser light source 13, the half mirror 14, the lens 15, and the like are mounted on the optical pickup 16. The optical pickup 16 is provided with a mechanism for focus servo and tracking servo.

  An optical disk 17 to be subjected to optical reproduction and recording of information by the optical pickup 16 is loaded on a turntable 18 and rotated by a motor 19. Although the optical disk 17 is not only mounted on the turntable 18 directly, such as a CD, but may be mounted in a jacket state such as an MD, the optical pickup 16 may be mounted. In contrast, since the shutter provided in the jacket is opened, the state is substantially the same.

  The presence / absence detection of the optical disc 17 and various servo controls as a reference example are performed by the control circuit 20. The control circuit 20 includes a microcomputer and performs control operations according to a preset program.

  A signal corresponding to the detected light quantity when the incident light 12 resulting from reflection when the optical disk 17 is loaded forms an image on the light receiving surface 11 is divided into A and B and amplified by the amplifier circuits 21 and 22, respectively. The light receiving surface 11 of the detector is composed of a photodiode, and a current value corresponding to the detected light amount is converted into a voltage value by the amplifier circuits 21 and 22 and amplified. The amplification gains of the amplifier circuits 21 and 22 can be controlled by the control circuit 20. The signals that have been subjected to IV conversion by the amplifier circuits 21 and 22 and amplified are added by the adder circuit 23 to derive a total signal representing the incident light quantity of A + B. The voltage level of the total signal is compared with the voltage of the reference level FOKLEV generated from the reference level generation circuit 25 by the comparison circuit 24, and the / FOK signal representing the comparison result is input to the control circuit 20. For servo control of the optical pickup 16, the output signal from the control circuit 20 is amplified by the drive circuit 26 to drive the actuator of the optical pickup 16.

  In the drawing, “/” indicates a bar symbol drawn on a character or a character string in the drawing, and indicates a negative logic signal, that is, a low level is a logical value representing true. However, it is also possible to use positive logic in which a high level represents true, and these choices are a matter of design.

  FIG. 2 shows the relationship between the lens sweep that moves the lens 15 that is the optical system of the optical pickup 16 in FIG. 1 along the optical axis with respect to the optical disc 17, the total signal level, and the / FOK signal that represents peak detection. Are indicated by (a), (b), and (c), respectively. When the focus is changed by sweeping the lens, the level of the total signal becomes maximum at the in-focus position where the focus is achieved, and the / FOK signal changes to a low level exceeding the reference level FOKLEV. The control circuit 20 can detect that the optical disk 17 is loaded by detecting that the / FOK signal transitions from the high level to the low level.

  FIG. 3 shows a procedure for determining the presence or absence of the optical disc 17 by the control circuit 20 of FIG. The procedure starts from step a0. At the start of the procedure, the amplification gains of the amplifier circuits 21 and 22 are set so as to leave room for gain increase. In step a1, the reference level generation circuit 25 is controlled to set the reference level FOKLEV. The reference level FOKLEV to be set is, for example, a voltage considered to be most appropriate in design.

  In step a2, it is determined whether or not the level of the / FOK signal representing the comparison result of the comparison circuit 24 is the high level “H”. When the high level is originally set to the low level due to the influence of the DC offset or the like, the reference level FOKLEV is increased at step a3, and the determination at step a2 is repeated until the high level is reached. Unless there is a failure in the optical pickup 16, the reference level FOKLEV is designed to be higher than the background level of the total signal that is not peaked. In the present embodiment, the reference level FOKLEV is raised to bring the / FOK signal to a high level, but the amplification gains of the amplifier circuits 21 and 22 may be reduced.

  When the / FOK signal becomes high level, the lens 15 is swept as shown in FIG. 2A at step a4. In step a5, it is determined whether or not the sweeping / FOK signal has become low level “L”. If it is determined that the level is not low, it is determined in step a6 whether or not the IV amplifier gain, which is the amplification gain of the amplifier circuits 21 and 22, is at the maximum value MAX. If the maximum value is not reached, the gain is increased at step a7, and the process returns to step a2. As a result, it is possible to avoid a situation in which the peak cannot be detected due to insufficient amplification of the total signal. In this embodiment, the amplification gains of the amplifier circuits 21 and 22 are increased, but the reference level FOKLEV may be decreased.

  When it is determined in step a5 that the in-sweep / FOK signal has become a low level, it is determined in step a8 that a disk is present and the optical disk 17 is loaded. If it is determined in step a6 that the I-V amplifier gain is MAX, it is determined in step a9 that there is no disk and the optical disk 17 is not loaded.

  FIG. 4 shows the relationship between the state in which the FOKLEV signal representing the reference level with respect to the total signal rises and the change in the / FOK signal in the procedure of FIG. If the level of the FOKLEV signal is low as shown by the alternate long and short dash line with respect to the total signal before sweeping the lens shown by the solid line in FIG. 4A, the / FOK signal becomes low level as shown in FIG. Become. Since the / FOK signal is at the low level before the sweep starts, the peak of the total signal cannot be detected by the change to the low level. If the level of the FOKLEV signal becomes higher than the total signal as indicated by a two-dot chain line in FIG. 4A, the / FOK signal becomes a high level, and the peak of the total signal can be detected by the change to the low level. It becomes possible.

  FIG. 5 shows another procedure for determining the presence or absence of an optical disc by the optical disc apparatus 10 of FIG. 1 as a second reference example of the present invention. The operation contents of steps b0 to b2 are the same as those of steps a0 to a2 in FIG. Further, the operation contents of the steps b4 to b9 are the same as the steps a4 to a9 of FIG.

  When it is determined in step b2 that the / FOK signal is not at a high level, it is determined in step b3 whether or not the reference level FOKLEV is equal to the maximum value MAX. The reference level generation circuit 25 has a limit in the range of the generated reference level FOKLEV based on constraints such as a power supply voltage. If it is determined in step b3 that the reference level FOKLEV is not equal to the maximum value MAX, the reference level is increased in step b3n, and the process returns to step b2. The operation of step b3n is equivalent to step a3 of FIG. If it is determined in step b3 that the reference level FOKLEV has reached the maximum value MAX and are equal, the IV amplifier gains of the amplifier circuits 21 and 22 are decreased DOWN in step b3y, and the process returns to step b2.

  In this reference example, since the degree of amplification of the DC offset component becomes small, the background level of the total signal becomes smaller than the reference level FOKLEV, and the possibility that the condition of step b2 is satisfied increases. For this reason, it is possible to prepare for the determination of the presence / absence of the optical disk more reliably.

  In this reference example, the reference level FOKLEV is increased until the / FOK signal becomes high level, and the amplifier circuits 21 and 22 are still in the state where the / FOK signal is at low level even if the reference level FOKLEV reaches the maximum value MAX. Even if the IV amplifier gain of the amplifier circuits 21 and 22 is decreased and the IV amplifier gain of the amplifier circuits 21 and 22 becomes the minimum value, the / FOK is reduced. When the signal is at the low level, the reference level FOKLEV may be increased and the IV amplifier gains of the amplifier circuits 21 and 22 may be set to initial values when the process returns to step b1.

  FIG. 6 shows a schematic electrical configuration of an optical disc apparatus 30 as a third reference example of the present invention. In the optical disc apparatus 30 of the present reference example, the same reference numerals are given to portions corresponding to those of the optical disc apparatus 10 in FIG. The control circuit 31 of the optical disk device 30 includes a microcomputer and the like, and the memory circuit 32 stores the reference level FOKLEV set in the reference level generation circuit 25 when the previous optical disk presence / absence determination is made. The memory circuit 32 can be configured using a semiconductor storage element such as a RAM having a backup power source or a nonvolatile flash memory.

  FIG. 7 shows an optical disc presence / absence determination procedure in the reference example of FIG. The operation content of each step of step c0 and step c3 to step b9 is equivalent to each step of step a0 and step a3 to step a9 of FIG. In step c 1, the previous reference level FOKLEV stored in the memory circuit 32 is set so as to be generated from the reference level generation circuit 25. As long as the same optical disk device 30 is used, the state of occurrence of DC offset or the like should not be very different from the previous time, and the possibility that the / FOK signal becomes high level in step c2 increases, and the lens in step c4 The time required until the start of the sweep can be shortened. The shortening time can be several seconds depending on the conditions. Note that the previous IV amplifier gains of the amplifier circuits 21 and 22 may be stored, and the IV amplifier gains of the amplifier circuits 21 and 22 may be set.

  FIG. 8 shows a schematic electrical configuration of the optical disc apparatus 40 as the first embodiment of the present invention. In the optical disk device 40 of the present embodiment, the same reference numerals are given to portions corresponding to the optical disk device 10 of FIG. The control circuit 41 including a microcomputer or the like inputs the level of the total signal derived from the adder circuit 23 as digital data that is analog / digital converted by the A / D circuit 42.

  FIG. 9 shows an optical disk presence / absence determination procedure in the embodiment of FIG. In step d0, the procedure is started, and in step d1, the level of the total signal indicating the amount of incident light on A and B on the light receiving surface 11 of the detector is measured. The measurement is performed by storing the voltage value converted into a digital value by the A / D circuit 42 in the memory circuit 43. The memory circuit 43 can be incorporated in a microcomputer included in the control circuit 40, or a register of the microcomputer can be used.

  In step d2, the lens 15 is swept as shown in FIG. In step d3, the maximum value MAX of the total signal is measured during the lens sweep. The measurement of the maximum value MAX is one of the basic algorithms of the microcomputer program, and therefore detailed procedures are omitted. In step d4, it is determined whether or not the A + B voltage value, which is the content of the total signal stored in the memory circuit 43, is sufficiently small compared to the maximum value MAX. If it is determined that the disk is sufficiently small, it is determined in step d5 that there is a disk. If it is determined in step d4 that it is not sufficiently small, the total signal level has not changed much from the background A + B voltage value before the lens sweep, and it is determined in step d6 that there is no disk.

  FIG. 10 shows a procedure for determining the presence or absence of another optical disk by the optical disk device 40 of FIG. 8 as a second embodiment of the present invention. The procedure starts from step e0, and in step e1, the lens 15 is swept first. During the lens sweep, the maximum value MAX of the total signal is measured at step e3. In step e4 after the sweep, the level of the total signal as the voltage value of A + B after the sweep is compared with the maximum value MAX stored during the sweep. The determination of the presence / absence of a disk based on the comparison results in step e5 and step e6 is the same as in steps d5 and d6 in FIG.

  In the first and second embodiments of the present invention, the presence / absence of the optical disc 17 is determined by a relative comparison of the total signal during and after the lens sweep. Therefore, even if the total signal includes a DC offset, it is possible to determine the presence / absence of the disk without being affected by the DC offset.

  Each embodiment of the present invention is less susceptible to erroneous disk detection even under the influence of a DC offset or the like, and therefore an optical disk included in an in-vehicle audio apparatus or navigation apparatus in which environmental fluctuations such as temperature may increase. The present invention can be particularly preferably applied to an apparatus or the like.

According to the present invention, the following embodiments are possible.
(1) In an optical disc apparatus that determines the presence or absence of an optical disc based on whether or not the level of a signal representing the amount of light incident from the optical system exceeds a reference level when the optical system is swept along the optical axis.
A reference level generation circuit for generating a reference level;
A comparison circuit that compares the level of the signal representing the amount of incident light with the reference level generated from the reference level generation circuit, and derives a signal representing the comparison result;
When the signal from the comparison circuit determines that the level of the signal representing the amount of incident light exceeds the reference level before the sweep of the optical system starts, the reference level is raised by controlling the reference level generation circuit. An optical disc apparatus comprising: a first control circuit that controls to start sweeping of an optical system after the level of a signal indicating the amount of light does not exceed a reference level.

  According to the present invention, the first control circuit is generated from the reference level generation circuit when it is determined by the signal indicating the comparison result from the comparison circuit that the level of the signal indicating the incident light amount exceeds the reference level. When the level of the signal indicating the amount of incident light does not exceed the reference level, the optical system starts to sweep. Since the level of the signal representing the amount of incident light does not exceed the reference level from the start of sweeping, for example, even if the DC offset increases, the reference level is set appropriately, and erroneous detection of the optical disk can be prevented.

  According to the present invention, when the level of the signal representing the incident light amount exceeds the reference level, the reference level is increased or the amplification gain is decreased so that the signal level representing the incident light amount does not exceed the reference level. After an appropriate state is reached, sweeping of the optical system is started, and the presence / absence of the optical disc can be determined based on the presence / absence of a peak in the level of a signal representing the incident light amount. For example, even if the DC offset becomes large, the reference level or amplification gain is set appropriately, and erroneous detection of the optical disc can be prevented.

(2) Amplifying a signal representing the amount of incident light and inputting the amplified signal to the comparison circuit;
The first control circuit reduces the amplification gain of the amplifier circuit when the reference level does not reach the level of the signal representing the incident light amount even if the reference level is raised to a preset upper limit, and then the reference level generation circuit An optical disc apparatus characterized in that the control for increasing the reference level generated from the recording medium is performed again.

  According to the present invention, the first control circuit is configured such that the level of the signal representing the incident light amount by a DC offset or the like exceeds the reference level before the start of the sweep of the optical system, and the reference level reduces the incident light amount only by increasing the reference level. If the level does not reach the level indicated, the amplification gain of the amplifier circuit is decreased. By reducing the amplification gain, the DC offset component and the like are also reduced, and control is performed so that the level of the signal representing the incident light quantity does not exceed the reference level except for the peak, so that erroneous detection of the optical disk can be prevented more reliably.

  According to the present invention, the control circuit increases the reference level and increases the amplification gain of the amplification circuit when the level of the signal representing the incident light amount by a DC offset or the like exceeds the reference level before the start of the sweep of the optical system. As a result, the DC offset component is also reduced, and the reference level and amplification gain are set appropriately so that the signal level representing the incident light quantity does not exceed the reference level except for the peak, thereby making it possible to further reliably detect optical disc errors. Can be prevented.

(3) In an optical disc apparatus that determines the presence or absence of an optical disc based on whether or not the level of a signal representing the amount of light incident from the optical system exceeds a reference level when the optical system is swept along the optical axis.
A reference level generation circuit for generating a reference level;
A comparison circuit that compares the level of the signal representing the amount of incident light with the reference level generated from the reference level generation circuit and derives a comparison result;
An amplification circuit that amplifies a signal representing the amount of incident light and inputs the amplified signal to the comparison circuit;
When the signal from the comparison circuit determines that the level of the signal representing the incident light amount exceeds the reference level before the optical system starts sweeping, the amplification circuit is controlled to reduce the amplification gain, and the incident light amount is reduced. An optical disc apparatus comprising: a second control circuit that controls to start sweeping of the optical system after the level of the signal to be expressed does not exceed the reference level.

  According to the present invention, the second control circuit reduces the amplification gain of the amplifier circuit when it is determined by the signal representing the comparison result from the comparison circuit that the level of the signal representing the incident light amount exceeds the reference level. Then, after the level of the signal representing the incident light quantity does not exceed the reference level, sweeping of the optical system is started. Since the level of the signal representing the amount of incident light does not exceed the reference level from the start of sweeping, for example, even if the DC offset is increased, the amplification gain is appropriately set, and erroneous detection of the optical disk can be prevented.

  According to the present invention, since the reference level or / and amplification gain at the previous operation is used as an initial value to control the increase of the reference level or / and the decrease of the amplification gain, The reference level can be increased or / and the amplification gain can be decreased from the state where the influence has already been taken into account, and the reference level or / and the amplification gain can be set appropriately for a short time.

  (4) The second control circuit generates a reference level generated from a reference level generation circuit when the reference level does not reach the level of the signal representing the incident light amount even if the amplification gain is increased to a preset upper limit. The optical disc apparatus is characterized in that the control for decreasing the amplification gain of the amplifying circuit is performed again after the signal is raised.

  According to the present invention, the second control circuit allows the level of the signal representing the incident light amount due to DC offset or the like to exceed the reference level before the start of the sweep of the optical system, and the reference level reduces the incident light amount only by reducing the amplification gain. When the level does not reach the level indicated, the reference level generated from the reference level generation circuit is increased, and then the amplification gain of the amplifier circuit is decreased again. By increasing the reference level, even if there is a DC offset component or the like, control is performed so that the level of the signal representing the incident light quantity does not exceed the reference level except for the peak, and erroneous detection of the optical disc can be prevented more reliably.

(5) a first memory circuit for storing the reference level;
When the first or second control circuit performs control to increase the reference level generated from the reference level generation circuit, the reference level at the previous determination stored in the first memory circuit is used as an initial value. An optical disc apparatus characterized by controlling.

  According to the present invention, when the first or second control circuit performs control to increase the reference level, the reference level at the previous operation stored in the first memory circuit is used as the initial value. The reference level can be raised from the state in which the influence of the DC offset characteristic of the apparatus is taken into account, and an appropriate reference level can be set in a short time.

(6) a second memory circuit for storing the amplification gain;
The second control circuit controls the amplification gain at the previous determination recorded in the second memory circuit as an initial value when performing control to reduce the amplification gain of the amplification circuit. apparatus.

  According to the present invention, when the second control circuit performs control to reduce the amplification gain of the amplifier circuit, the amplification gain at the previous operation stored in the second memory circuit is used as the initial value, so that the optical disk The amplification gain can be reduced from the state in which the influence of the DC offset characteristic of the device is taken into account, and an appropriate amplification gain can be set in a short time.

1 is a block diagram showing a schematic electrical configuration of an optical disc apparatus of a first reference example of the present invention. 2 is a graph showing the relationship between lens sweep, total signal level, and FOK signal representing peak detection in the reference example of FIG. 1. 2 is a flowchart showing a procedure for determining the presence or absence of an optical disc in the reference example of FIG. 2 is a graph showing a relationship between an increase in a FOKLEV signal indicating a reference level with respect to a total signal in the reference example of FIG. 1 and a change in the FOK signal. As a second reference example of the present invention, it is a flowchart showing a procedure for determining the presence or absence of another optical disc by the optical disc apparatus 10 of FIG. It is a block diagram which shows schematic electrical structure of the disc apparatus as the 3rd reference example of this invention. 7 is a flowchart showing a procedure for determining whether or not there is an optical disc in the reference example of FIG. 6. 1 is a block diagram showing a schematic electrical configuration of a disk device as a first embodiment of the present invention; 9 is a flowchart showing a procedure for determining whether or not there is an optical disc in the embodiment of FIG. It is a flowchart which shows the presence-absence determination procedure of an optical disk as 2nd Embodiment of this invention. It is a figure which shows the relationship between the change of a focus, and the shape of the incident light imaged on the light-receiving surface divided into four by the detector. 12 is a graph showing a relationship between a change in focus, a signal level representing the amount of incident light for each of the light receiving surfaces A and B in FIG. 11, and a change in the level of the total signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 30, 40 Optical disk apparatus 11 Light-receiving surface 12 Incident light 15 Lens 16 Optical pick-up 17 Optical disk 20, 31, 41 Control circuit 21, 22 Amplifier circuit 23 Adder circuit 24 Comparison circuit 25 Reference level generation circuit 26 Drive circuit 32, 43 Memory Circuit 42 A / D circuit

Claims (2)

In an optical disc apparatus that determines the presence or absence of an optical disc based on the amount of light incident from the optical system when sweeping the optical system along the optical axis.
A memory circuit for storing the level of a signal representing the amount of incident light before sweeping the optical system;
A maximum value detection circuit for detecting the maximum value of the signal level indicating the incident light amount during the sweep of the optical system;
After sweeping the optical system, the level of the signal stored in the memory circuit is compared with the level of the signal detected by the maximum value detection circuit, and when the level difference between the signals is within a preset range, An optical disk apparatus comprising: a determination circuit that determines that there is no optical disk. In an optical disc apparatus that determines the presence or absence of an optical disc based on the amount of light incident from the optical system when sweeping the optical system along the optical axis.
A maximum value detection circuit for detecting the maximum value of the signal level indicating the incident light amount during the sweep of the optical system;
After sweeping the optical system, the level of the signal representing the amount of incident light is compared with the level of the signal detected by the maximum value detection circuit, and when the level difference between the signals is within a preset range, there is no optical disc An optical disc apparatus comprising: a determination circuit for determining

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