JP3986715B2 - Reflected light quantity detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an optical disk apparatus for recording, reproducing, or erasing information by condensing a light beam from a semiconductor laser onto a recording medium.Reflected light intensity normalization circuitEtc.Reflected light quantity detection deviceAbout
[0002]
[Prior art]
  In an optical disk apparatus that records, reproduces, or erases information on a plurality of types of optical disks, it is necessary to accurately determine the optical disk on which information is recorded, reproduced, or erased.
  Examples of the optical disk include a highly reflective disk such as CD-ROM and CD-R, and a low-reflectance CD-RW.
[0003]
  Conventionally, as a means for accurately discriminating the reflectivity of the optical disc as described above, the reflected light when the optical disc is irradiated with one beam spot from a semiconductor laser light source (hereinafter referred to as “LD”) is photoelectrically detected by a light receiving element. Convert and normalize the sum signal with a signal representing the LD beam quantityReflected light quantity detection device(See, for example, JP-A-7-262560).
[0004]
  Also, the optical disc is discriminated based on a signal indicating the amount of light received during on-focus.Reflected light quantity detection device(For example, see Japanese Patent Application Laid-Open No. 11-25579).
[0005]
[Problems to be solved by the invention]
  However, as mentioned aboveReflected light quantity detection deviceThen, when the optical disk is irradiated with three beam spots consisting of one main beam spot and two sub beam spots from the LD, the total signal of all reflected light including the main beam spot and the sub beam spot ("main sub" Called "summation signal")Reflected light quantityHowever, there are problems as shown below.
[0006]
  First, the three-beam method and the DPP method are known as methods for irradiating three beam spots as described above.
[0007]
  The three-beam method is mainly used for an optical disc apparatus such as a CD-ROM drive for reproducing information, and a track on which information is recorded (or recorded from now on) and a track corresponding to ¼ track from the center of the track. This is a method of condensing the sub beam spot at a position shifted by a distance.
[0008]
  On the other hand, the DPP method is mainly used in an optical disc apparatus such as a CD-R drive or a CD-RW drive for recording, erasing, or reproducing information, and a sub-beam spot is condensed at the center of the track. It is.
[0009]
  When the three-beam method or the DPP method as described above is used, the light amount of the main beam and the sub beam of the LD of the optical pickup is larger in the main beam, and the light amount ratio varies from several times to 20 times. .
  Therefore, in order to detect a signal corresponding to the amount of light reflected from the optical disk by each beam, it is necessary to increase the signal gain of the means for detecting the sub beam.
[0010]
  Here, for discriminating the optical disc, the amount of light reflected from the optical disc is measured, but the objective lens is moved up and down (UP / DOWN) in a state where the focus control is not applied.Reflected light amount detection signalFind the peak of etc.
  This is because normal power control cannot be expected because proper power or the like cannot be set before discriminating the optical disk.
[0011]
  At this time, the main beam is incident on the light receiving element that receives the sub beam in a state of being largely off-focused, and the amount of the main beam is large and the sub beam detection gain is high.Reflected light amount detection signalIs larger than on-focus and accurateReflected light amount detection signalThere was a problem that it was impossible to measure.
[0012]
  On the other hand, in the sum signal only of the reflected light of the main beam spot (referred to as “main sum signal”), the phenomenon as described above does not occur.Reflected light quantityWhen detecting a sudden change in the number of defectsReflected light amount detection signalIs used, the effect of crossing the track during off-track during on-focus is affected.Reflected light amount detection signalWill appear as a level change ofReflected light amount detection signalIs not a constant level output, stableReflected light amount detection signalThere was a problem that could not be obtained.
[0013]
  The present invention has been made to solve the above problems, and is accurate and stable when a plurality of beam spots with different light amounts are irradiated onto a recording medium.Reflected light quantityIs intended to be obtained.
[0014]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention provides a beam spot for irradiating a recording medium with a light emitting means for emitting a light beam and a main beam spot with a large amount of light and a sub beam spot with a small amount of light based on the light emitted by the means. The reflected light of the main beam spot irradiated by the irradiation means and the means is received, and is the sum of the received reflected light.Main sum signal output means for outputting main sum signalAnd the reflected light of the sub beam spot irradiated by the beam spot irradiating means, and the sum of the sub total signal that is the sum of the received reflected light and the main total signal.Main sub-sum signal output means for outputting a main-sub sum signal, light quantity detection means for detecting the light quantity of light emitted by the light-emitting means, and normalizing the main sum signal based on the light quantity detected by the means A main sum signal normalizing means for normalizing the main sub signal, based on the light quantity detected by the light quantity detecting means.
[0015]
[0016]
  Furthermore, as aboveReflected light quantity detection deviceThe light amount detecting means for detecting the light amount of the light emitted by the light emitting means, the main sum signal / main sub sum signal selecting means for selecting one of the main sum signal and the main sub sum signal, and A main sum signal / main sub sum signal normalizing means for normalizing the main sum signal or the main sub sum signal selected by the main sum signal / main / sub sum signal selecting means based on the light quantity detected by the light amount detecting means; It is good to provide.
[0017]
  Also as aboveReflected light quantity detection deviceIn this embodiment, there is provided a normalization main sum signal / main sub sum signal voltage gain changing means for changing the voltage gain of the main sum signal or the main sub sum signal before normalization in a plurality of stages based on the reflectance of the recording medium. Good.
[0018]
  Furthermore, as aboveReflected light quantity detection deviceThe light amount voltage gain changing means for changing the voltage gain of the light amount detected by the light amount detecting means in a plurality of stages may be provided.
[0019]
  Also as aboveReflected light quantity detection deviceThe normalized main sum signal / main sub sum signal voltage gain changing means for changing the voltage gain of the normalized main sum signal or main sub sum signal in a plurality of stages may be provided.
[0020]
  Furthermore, as aboveReflected light quantity detection deviceIn the above, it is preferable to provide an offset removing means for removing the electrical offset between the main sum signal and the main sub sum signal before normalization or the light amount detected by the light amount detecting means.
[0021]
  Furthermore, as aboveReflected light quantity detection deviceThe offset removal amount changing means for changing the offset removal amount by the offset removal means according to the reproduction state, recording state, erasing state, or type of the recording medium may be provided.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
  Embodiments of the present invention will be specifically described below with reference to the drawings.
  FIG. 1 is a diagram according to claim 1 of the present invention.Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitIt is a block diagram which shows the structure of these.
[0023]
  thisReflected light intensity normalization circuitIs mounted on an optical disc apparatus for recording, reproducing, and erasing information, and a pickup unit (Pick Up Module: PUM) 1 has a light emitting unit including a semiconductor laser light source (LD), an objective lens, and the like. .
[0024]
  This light emitting unit emits a laser beam on the surface of an optical disc (recording medium) and condenses the beam bundle. Based on the DPP method, one main beam spot (a beam spot with a large amount of light) and two sub beam spots are used. Irradiate a beam spot with a small amount of light.
[0025]
  Further, the PUM 1 has a light receiving unit including a light receiving element that receives and photoelectrically converts each reflected light from the optical disk based on the main beam spot and the sub beam spot.
[0026]
  This light receiving unit receives the reflected light of the main beam spot, photoelectrically converts it, and outputs it as a main beam signal S1 to the adder circuit 4. Further, the reflected light of the sub beam spot is received and subjected to photoelectric conversion, which is output to the adder circuit 5 as a sub beam signal S2.
  Further, the PUM 1 also includes a light receiving element that outputs a beam light amount signal S 6 indicating the light amount of the semiconductor laser light source to the adding circuit 7.
[0027]
  The LD control circuit 2 controls the light emission amount of the laser beam by the PUM1 based on the LD control signal S7 from the CPU 3 and the beam light amount signal S6 output from the PUM1.
[0028]
  The CPU 3 is a microcomputer, and thisReflected light intensity normalization circuitIn addition to controlling the entire system, it will be described later.Reflected light amount detection signalThe LD control signal S7 is output to the LD control circuit 2 based on the above.
[0029]
  The adder circuit 4 obtains a main sum signal S3 which is a sum obtained by adding the main beam signals S1 output from the PUM1, and obtains the main sum signal S3.Reflected light amount detection signalTo the CPU 3 and to the adder circuit 6.
[0030]
  The adder circuit 5 obtains a total sub-beam sum signal S4 obtained by adding the sub-beam signals S2 output from the PUM1, and outputs the sub-sum signal S4 to the adder circuit 6.
[0031]
  The adder circuit 6 obtains a main sub-sum signal S5 of the sum obtained by adding the main sum signal S3 input from the adder circuit 4 and the sub-sum signal S4 input from the adder circuit 5, and obtains the main sub-sum signal S5.Reflected light amount detection signalTo the CPU 3.
[0032]
  The adder circuit 7 adds the beam light amount signal S6 output from the PUM1 and outputs the sum to the LD control circuit 2.
[0033]
  thisReflected light intensity normalization circuitThe PUM 1 emits a laser beam with a predetermined LD power through the LD control circuit 2 on the basis of the beam light amount signal S6 indicating the beam light amount by the LD control signal S7 from the CPU 3, and the main beam spot and the sub beam spot are formed on the optical disk surface. Irradiate.
[0034]
  The main beam spot and the sub beam spot condensed on the optical disk are reflected, respectively, and the light receiving element for the main beam and the light receiving elements for the sub beam of the PUM 1 receive the light, respectively, and photoelectrically convert them to the main beam signal S1 and the sub beam, respectively. Output as signal S2.
[0035]
  Further, the adder circuit 4 obtains a main sum signal S3 of the sum of the main beam signals S1, and calculates it.Reflected light amount detection signalTo the CPU 3 and to the adder circuit 6. The adder circuit 6 obtains a main sub-sum signal S5 that is the sum of the main sum signal S3 and the sub-sum signal S4,Reflected light amount detection signalTo the CPU 3.
  And CPU3 is theEach reflected light amount detection signalBased on the above, an LD control signal S7 is generated and output to the LD control circuit 2.
[0036]
  In other words, the PUM 1 functions as a beam spot irradiating unit that irradiates a recording medium with a light emitting unit that emits a light beam and a main beam spot with a large amount of light and a sub beam spot with a small amount of light based on the light beam emitted by the unit. Fulfill.
[0037]
  The PUM1 and the adder circuit 4 receive the reflected light of the main beam spot irradiated by the beam spot irradiating means, and are the sum of the received reflected light.Main sum signal output means for outputting main sum signalFulfills the function.
[0038]
  Further, the PUM 1 and the addition circuits 5 and 6 receive the reflected light of the sub beam spot irradiated by the beam spot irradiating means, and the sum of the sub total signal, which is the sum of the received reflected light, and the main total signal. is thereMain sub sum signal output means for outputting main sub sum signalFulfills the function.
[0039]
  thisReflected light intensity normalization circuitFor example, during off-focus and on-focusReflected light amount detection signalWhen measuring the absolute value ofReflected light amount detection signal of main / sub total signal S5Has a problem that the main signal component enters the sub-signal in the off-focus state and its absolute value becomes larger than that in the on-focus state.
[0040]
  Therefore, the CPU 3Reflected light amount detection signal of main sum signal S3Is used for measurement. Therefore, it is accurate during off-focusReflected light quantityCan be measured.
[0041]
  on the other hand,Reflected light amount detection signal of main sum signal S3If you are off-tracking during on-focus, the effect of crossing the trackReflected light amount detection signalWill appear as a level change, so stableReflected light amount detection signalCan't get.
[0042]
  Therefore, the CPU 3Reflected light amount detection signal of main / sub total signal S5Is used. Therefore, it is accurate even when off-tracking during on-focus.Reflected light quantityCan be measured.
[0043]
  In this wayReflected light quantitySince there are two systems of main sum signal and main sub sum signal, or sub sum signal, the signal to detect is always stable by using the signal according to the situationReflected light amount detection signalCan be obtained.
[0044]
  FIG. 2 is a diagram according to claim 2 of the present invention.Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitFIG. 2 is a block diagram showing the configuration of FIG. 1, and parts common to FIG.
[0045]
  Shown in Figure 1 aboveReflected light intensity normalization circuitIf the light emission amount of LD changes, even if the reflectance is constantReflected light amount detection signalChanges in the output. Therefore, as shown in FIG.Reflected light intensity normalization circuitThen, regardless of the change in the amount of light emitted from the LD, the output level changed only by the change in reflectance, and was stable.Reflected light quantityIs to be obtained.
[0046]
  As shown in FIG.Reflected light intensity normalization circuitThen, the beam light amount signal S6 output from the adder circuit 7 and the main sum signal S3 output from the adder circuit 4 are input, and the main sum signal S3 is normalized based on the beam light amount signal S6.Reflected light amount detection signalAs a main signal normalization circuit 10 to be output to the CPU 3 is newly provided.
[0047]
  Further, the beam light amount signal S6 output from the adder circuit 7 and the main sub sum signal S5 output from the adder circuit 6 are input, and the main sub sum signal S5 is normalized based on the beam light amount signal S6.Reflected light amount detection signalThe main sub signal normalization circuit 11 for outputting to the CPU 3 is also provided.
[0048]
  That is, the PUM1 functions as a light amount detecting unit that detects the amount of light emitted by the light emitting unit.
[0049]
  Further, the adder circuit 7 and the main signal normalization circuit 10 function as a main sum signal normalization means for normalizing the main sum signal based on the light quantity detected by the light quantity detection means.
[0050]
  Further, the adder circuit 7 and the main sub signal normalization circuit 11 function as main sub sum signal normalization means for normalizing the main sub sum signal based on the light quantity detected by the light quantity detection means.
[0051]
  thisReflected light intensity normalization circuitIs output to the CPU 3 by the main signal normalization circuit 10 and the main sub signal normalization circuit 11.Reflected light amount detection signalThis level is not affected by the amount of light emitted from the semiconductor laser light source, but only by the difference in reflectance.Reflected light quantityCan be measured.
[0052]
  In this way, the output changes stably only by the change in reflectance regardless of the change in the light emission amount of the LD.Reflected light amount detection signalCan be obtained.
[0053]
  FIG. 3 shows a third aspect of the present invention.Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitFIG. 2 is a block diagram showing the configuration of FIG. 1, and parts common to those in FIGS.
[0054]
  Shown in Figure 2 aboveReflected light intensity normalization circuitIn this case, two normalization circuits, that is, the main signal normalization circuit 10 and the main sub signal normalization circuit 11 are required. However, the normalization circuit is generally expensive and expensive.
[0055]
  Therefore, as shown in FIG.Reflected light intensity normalization circuitThen, it showed in the said FIG. 2 using one normalization circuit.Reflected light intensity normalization circuitCan obtain the same function as above, andReflected light intensity normalization circuitIt is easier and less expensive.
[0056]
  As shown in FIG.Reflected light intensity normalization circuitThen, as shown in FIG.Reflected light intensity normalization circuitIn place of the main signal normalization circuit 10 and the main sub signal normalization circuit 11, a normalization circuit block 20 is provided.
[0057]
  The normalization circuit block 20 includes an analog switch 21 and a normalization circuit 22. The analog switch 21 is input from the addition circuit 4 to the normalization circuit 22 based on the normalized signal selection signal S 8 output from the CPU 3. The output of the main sum signal S3 and the main sub sum signal S5 input from the adder circuit 6 is switched.
[0058]
  The normalization circuit 22 normalizes the main sum signal S3 or the main sub sum signal S5 output via the analog switch 21 and outputs the normalized signal to the CPU 3.
[0059]
  That is, the PUM1 and the adder circuit 7 serve as a light amount detecting unit that detects the amount of light emitted by the light emitting unit.
  The CPU 3 and the analog switch 21 function as main sum signal / main sub sum signal selection means for selecting one of the main sum signal and the main sub sum signal.
[0060]
  Further, the adding circuit 7 and the normalizing circuit 22 normalize the main sum signal or the main sub sum signal selected by the main sum signal / main / sub sum signal selecting means based on the light quantity detected by the light quantity detecting means. It functions as a main sum signal / main sub sum signal normalization means.
[0061]
  thisReflected light intensity normalization circuitDuring on-focus and off-focusReflected light quantity, The CPU 3 outputs a normalized signal selection signal S8 for switching to the main sum signal S3 to the analog switch 21, and the analog switch 21 switches the connection to the main sum signal S3 side to normalize the circuit 22. The main sum signal S3 is output. Then, the normalization circuit 22 normalizes the main sum signal S3.Reflected light amount detection signalTo the CPU 3.
[0062]
  Further, during off-track during on-focus, the CPU 3 outputs a normalized signal selection signal S8 for switching to the main sub sum signal S5 to the analog switch 21, and the analog switch 21 switches the connection to the main sub sum signal S5 side. The main sub total signal S5 is output to the normalization circuit 22. The normalization circuit 22 normalizes the main / sub total signal S5.Reflected light amount detection signalTo the CPU 3.
[0063]
  In this way, less expensive normalization circuits can be configured, andReflected light quantityThe signal to be measured can be reduced, so it is stableReflected light quantityCan be obtained easily and at low cost.
[0064]
  FIG. 4 is a diagram according to claim 4 of the present invention.Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitFIG. 4 is a block diagram showing the configuration of the normalization circuit block, and the same reference numerals are given to portions common to FIGS. 1 to 3 and description thereof is omitted.
[0065]
  First, the absolute values of the main sum signal and the main sub sum signal representing the reflected light from the optical disc when information is generally reproduced from the optical disc having different reflectivity are greatly different due to the difference in the reflectivity of the optical disc.
[0066]
  For this reason, the main sum signal and main sub sum signal are normalized and output by the normalization circuit.Reflected light amount detection signalThe absolute values are also very different from each other, and when the reflectivity is small and the signal level is small, it is easily affected by the offset of the normalization circuit. A normalization circuit with a small offset is expensive.
[0067]
  As shown in FIG.Reflected light intensity normalization circuitThen, when information is to be reproduced from different types of optical discs, the magnitudes of the main sum signal S3 and the main sub sum signal S5 representing the amount of light reflected from the optical disc, which is a signal normalized by the normalization circuit 22, It varies greatly in proportion to the difference in reflectance.
[0068]
  Therefore, after discriminating the reflectivity based on the type of the optical disc, the signal becomes small when the optical disc has a low reflectivity, so that the normalization circuit 22 can easily influence the influence of the electrical offset.
[0069]
  In addition, the normalization circuit generally tends to generate an offset, and a low offset circuit is expensive and expensive.
  Therefore, in the normalization circuit block shown in FIG. 4, the influence of offset at the time of normalization is reduced.
[0070]
  As shown in FIG. 4, in this normalization circuit block, the signal levels of the main sum signal S3 and the main sub sum signal S5 that are selected by the analog switch 21 and output to the normalization circuit 22 are set as variable gains from the CPU 3. A variable gain amplifier 30 that switches to at least two stages based on the control signal S9 is newly provided.
[0071]
  That is, the CPU 3 and the variable gain amplifier 30 change the voltage gain of the main sum signal or the main sub sum signal before normalization in a plurality of stages based on the reflectance of the recording medium. It functions as a sub total signal voltage gain changing means.
[0072]
  This normalization circuit block was providedReflected light intensity normalization circuitFor example, when reproducing information on an optical disk, the CPU 3 sends a variable gain control signal S9 corresponding to the difference in reflectance to the variable gain amplifier 30 after the determination of the reflectance of the optical disk. Changes the voltage gain of the main sum signal S3 or the main sub sum signal S5 input from the analog switch 21 based on the variable gain control signal S9, and outputs it to the normalization circuit 22 at a constant level.
[0073]
  Therefore, the normalization circuit 22 always normalizes the main sum signal S3 or the main sub sum signal S5 at a constant level.Reflected light amount detection signalThe influence of offset on the can be reduced, and an inexpensive configuration can be achieved.
[0074]
  In this way, the signal level is adjusted for the main sum signal and the main sub sum signal that are normalized according to the reflectivity of the optical disc from which information is to be reproduced. Therefore, the reflectivity of the optical disc from which information is to be reproduced is adjusted. Regardless, a nearly constant voltage will be input to the normalization circuit,Reflected light amount detection signalOffset effect can be reduced, andReflected light intensity normalization circuitCan be configured at low cost.
[0075]
  FIG. 5 is a diagram according to claim 5 of the present invention.Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitFIG. 5 is a block diagram showing the configuration of the normalization circuit block, and the same reference numerals are given to portions common to those in FIGS. 1 to 4 and description thereof is omitted.
[0076]
  Normally, the required LD emission power differs greatly between the case where information is reproduced from the optical disk and the case where information is recorded or erased on the optical disk. There is.
[0077]
  Therefore, it is necessary to provide a normalization circuit having a wide voltage input range and a large voltage gain range. However, providing such a normalization circuit results in high cost.
[0078]
  That is, since the magnitude of the beam light amount signal output to the normalization circuit differs between when reproducing information from the optical disc and when recording or erasing information, the normalization circuit block shown in FIG. In addition, a high quality signal having a large level in the voltage input range and voltage gain of the beam light quantity signal is required.
[0079]
  Therefore, the normalization circuit block shown in FIG. 5 can be normalized even by using an inexpensive normalization circuit with a small voltage input range and voltage gain by adjusting the voltage gain of the beam light amount signal input to the normalization circuit. I am doing so.
[0080]
  As shown in FIG. 5, the normalization circuit block is newly provided with a variable gain amplifier 31 that switches the signal level of the beam light amount signal S6 to at least two stages based on a variable gain control signal from the CPU 3. Yes.
[0081]
  That is, the CPU 3 and the variable gain amplifier 31 function as a light amount voltage gain changing unit that changes the voltage gain of the light amount detected by the light amount detecting unit in a plurality of stages.
[0082]
  This normalization circuit block was providedReflected light intensity normalization circuitSends a variable gain control signal S10 to the variable gain amplifier 31 indicating an adjustment level according to a state in which the CPU 3 is reproducing information on the optical disc or a state in which information is being recorded or erased on the optical disc.
  The variable gain amplifier 31 adjusts the beam light amount signal to the adjustment level of the variable gain control signal S10 and outputs it to the normalization circuit 22.
[0083]
  Accordingly, a beam light amount signal at a constant level can always be input to the normalization circuit 22 even in the state of reproducing, recording, or erasing information. Therefore, the voltage input range and voltage gain range of the divider that realizes the normalization circuit 22 Can be reduced.
[0084]
  In this way, the output level of the beam light amount signal, which changes depending on whether information is being reproduced from the optical disk or whether information is being recorded or erased, is always input to the normalization circuit with a constant output level. The voltage gain and voltage input range of the normalization circuit can be reduced, and normalization can be performed even with an inexpensive normalization circuit.
[0085]
  FIG. 6 is a diagram according to claim 6 of the present invention.Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitFIG. 6 is a block diagram showing the configuration of the normalization circuit block, in which parts common to those in FIGS. 1 to 5 are denoted by the same reference numerals and description thereof is omitted.
[0086]
  Reflected light intensity normalization circuitIf the PUM of the optical system element including the light emitting element and the light receiving element is different, the signal level output from the sum signal indicating the reflected light from the optical disk, even when information on the same optical disk is reproduced, recorded, or erased, A signal representing the amount of beam light may vary depending on variations in light receiving sensitivity of the light receiving element.
[0087]
  On the other hand accurateReflected light intensity measurementTherefore, when reproducing, recording, or erasing information on the same optical disk, it is possible to suppress variations in sensitivity of the optical system elements and to maintain a certain level.Reflected light level detection signal levelMust be output.
[0088]
  That is, in the normalization circuit block shown in FIG. 5, if the PUM1 including the light receiving element is different, even if the information on the same optical disk is reproduced, recorded, or erased, it represents the reflected light from the optical disk. The signal levels of the sum signal, sub-main sum signal, and beam light amount signal may vary depending on variations in the light receiving sensitivity of the light receiving elements.
[0089]
  Therefore, the normalization circuit block shown in FIG. 6 suppresses variations in the signal levels of the main sum signal, sub-main sum signal, and beam light amount signal due to variations in the light receiving sensitivity of the light receiving elements,Reflected light amount detection signalBased on accurateReflected light quantityCan be measured.
[0090]
  As shown in FIG. 6, in this normalization circuit block, the signal levels of the main sum signal S3 and the main sub sum signal S5 normalized by the normalization circuit 22 are based on the variable gain control signal S11 from the CPU 3. A variable gain amplifier 32 that switches to at least two stages and outputs to the CPU 3 is newly provided.
[0091]
  That is, the CPU 3 and the variable gain amplifier 32 function of the normalized main sum signal / main sub sum signal voltage gain changing means for changing the voltage gain of the normalized main sum signal or main sub sum signal in a plurality of stages. Fulfill.
[0092]
  This normalization circuit block was providedReflected light intensity normalization circuitThe CPU 3 outputs to the variable gain amplifier 32 a variable gain control signal S11 indicating an adjustment level according to variations in sensitivity and the like of optical system elements including the light receiving elements in the PUM1.
  The variable gain amplifier 32 adjusts the normalized main sum signal S3 or main sub sum signal S5 output from the normalization circuit 22 to the adjustment level of the variable gain control signal S11 and outputs it to the CPU 3.
[0093]
  Therefore, it is input to the CPU 3Reflected light amount detection signalIs always controlled at a certain level, so individual variations due to variations in sensitivity of light receiving elements, etc. are suppressed,Reflected light intensity measurementIs accurate and stableReflected light amount detection signalCan be obtained.
[0094]
  In this wayReflected light amount detection signalThe signal level can be changed to a certain level before being input to the CPU, so that individual variations due to variations in the sensitivity of the light receiving elements to the CPU are suppressed and stable.Reflected light amount detection signalCan be supplied.
[0095]
  FIG. 7 is a diagram according to claim 7 of the present invention.Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitFIG. 7 is a block diagram showing the configuration of the normalization circuit block, and the same reference numerals are given to portions common to FIGS. 1 to 6 and description thereof is omitted.
[0096]
  When trying to process the beam light amount signal, the main sum signal of reflected light from the optical disc, the main sub sum signal, etc., with an electrical signal, an element that converts light into an electrical signal by the photoelectric effect, or the signal into a predetermined signal An electrical offset may occur in the signal processing system to be converted.
[0097]
  In such a case, the normalization circuit performs an operation including an electrical offset and is accurate.Reflected light amount detection signalYou will not be able to get.
[0098]
  That is, in the normalization circuit block shown in FIG. 6, an electrical voltage offset is applied to the beam light amount signal, the main sum signal, and the main sub sum signal, so that accurateReflected light amount detection signalMay not be obtained.
[0099]
  Therefore, in the normalization circuit block shown in FIG. 7, by providing means for removing the electrical offset, it is possible to correct even if an offset occurs in the beam light amount signal, the main sum signal, and the main sub sum signal.Reflected light amount detection signalIs to be obtained.
[0100]
  As shown in FIG. 7, the normalization circuit block includes a digital / analog converter (Digital Analog Converter: DAC) for adjusting the beam light amount offset that is output to the variable gain amplifier 31 by removing the electrical offset of the beam light amount signal S6. 40 is newly provided.
[0101]
  Furthermore, a digital / analog converter (DAC) 41 for adjusting the sum signal offset that removes the electrical offset of the main sum signal S3 and the main sub sum signal S5 output from the analog switch 21 and outputs to the variable gain amplifier 30 is also newly provided. Provided.
[0102]
  The DAC generates an analog signal for removing an electrical offset based on a setting by a digital signal from the CPU 3, and an electric circuit for applying the analog signal to a beam light amount signal, a main sum signal, and a sub main sum signal. Consists of.
[0103]
  That is, the beam light amount offset adjusting DAC 40 and the sum signal offset DAC 41 calculate the electrical offset between the main sum signal and the main sub sum signal before normalization or the light amount detected by the light amount detecting means. It functions as an offset removing means for removing.
[0104]
  This normalization circuit block was providedReflected light intensity normalization circuitThe beam light amount offset DAC 40 generates an electric signal in a direction to remove the electric offset of the beam light amount signal, applies the electric signal to the beam light amount signal to remove the offset, and the sum signal offset DAC 41 generates the main sum. An electric signal is generated in a direction to remove the electrical offset of the signal and the main / sub sum signal, and the offset is removed by applying the electric signal to the main sum signal and the main / sub sum signal.
[0105]
  Therefore, by removing the electrical offset of the main sum signal S3, the main sub sum signal S5, and the beam light amount signal S6 in the previous stage of the normalization circuit 22, the normalization circuit 22 has a pure signal component.OnlyEntered so accurateReflected light quantityCan be measured.
[0106]
  In FIG. 7, both the beam light amount offset adjustment DAC 40 and the total signal offset DAC 41 are provided, but either one may be provided.
[0107]
  In this wayReflected light amount detection signalIt is possible to eliminate the electrical offset generated in the beam light quantity signal, main sum signal, and sub main sum signal that constitutes theReflected light quantityCan measureReflected light intensity normalization circuitCan be provided.
[0108]
  FIG. 8 is a diagram according to claim 8 of the present invention.Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitFIG. 8 is a block diagram showing the configuration of the normalization circuit block, and the same reference numerals are given to portions common to those in FIGS. 1 to 7 and description thereof is omitted.
[0109]
  Depending on the type of optical disc, the state where information is being reproduced from the optical disc, or the state where information is being recorded or erased on the optical disc, the signal level and gain of the electrical circuit may differ, and the amount of electrical offset may also vary. is there.
  In such a case, it is not possible to remove the offset sufficiently with only one type of offset adjustment value.Reflected light amount detection signalThere is a fear that you can not get.
[0110]
  That is, in the normalization circuit block shown in FIG. 7, only one type of offset adjustment signal can be output from each of the beam light amount offset adjustment DAC 40 and the total signal offset adjustment DAC 41. If the voltage gain of the electric circuit is different or the amount of the electric offset is different when recording or erasing is performed, the electric offset may not be accurately removed.
[0111]
  Therefore, in the normalization circuit block shown in FIG. 8, the electrical offset can always be accurately removed regardless of whether the information is reproduced or whether the information is recorded or erased.
[0112]
  As shown in FIG. 8, the normalization circuit block includes a first beam light amount offset adjustment DAC 51 and a second beam light amount offset adjustment DAC 52 that output different offset adjustment signals for removing the electrical offset of the beam light amount signal S6. Based on the offset adjustment DAC selection signal S12 from the CPU 3, the first beam light amount offset adjustment DAC 51 or the second beam light amount offset adjustment DAC 52 is connected, and the offset adjustment signal output from the connected DAC is used as the beam light amount offset adjustment signal S14. As a result, an analog switch 50 is newly provided.
[0113]
  Also, a first total signal offset adjustment DAC 61 and a second total signal offset adjustment DAC 62 that output different offset adjustment signals for removing the electrical offset of the main sum signal S3 or the main sub sum signal S5, and an offset adjustment DAC from the CPU 3. An analog switch 60 is also connected to the first sum signal offset adjustment DAC 61 or the second sum signal offset adjustment DAC 62 based on the selection signal S13, and outputs the offset adjustment signal output from the connected DAC as the sum signal offset adjustment signal S15. Provided.
[0114]
  That is, the CPU 3, the analog switches 50 and 60, the first beam light amount offset adjustment DAC 51, the second beam light amount offset adjustment DAC 52, the first sum signal offset adjustment DAC 61, and the second sum signal offset adjustment DAC 62 are reproduced from the recording medium. It functions as an offset removal amount changing means for changing the offset removal amount by the offset removal means in accordance with the state, recording state, erasing state, or type of the recording medium.
[0115]
  This normalization circuit block was providedReflected light intensity normalization circuitTries to reproduce information from the optical disc type and the optical disc in advance for the first beam light amount offset adjustment DAC 51, the second beam light amount offset adjustment DAC 52, the first total signal offset adjustment DAC 61, and the second total signal offset adjustment DAC 62. It is set so that each offset adjustment signal corresponding to a state in which information is recorded or information is to be recorded on or deleted from the optical disk is output.
[0116]
  When the CPU 3 determines the type of the optical disk, the state where information is being reproduced from the optical disk, or the state where information is being recorded or erased from the optical disk, offset adjustment DAC selection signals S12 and S13 indicating the determined state are displayed. Send to analog switches 50 and 60, respectively.
[0117]
  The analog switches 50 and 60 are respectively connected to the first beam light amount offset adjustment DAC 51 or the second beam light amount offset adjustment DAC 52 based on the offset adjustment DAC selection signals S12 and S13 input from the CPU 3, and the first total signal offset adjustment. The connection to the DAC 61 or the second total signal offset adjustment DAC 62 is switched, and the offset adjustment signals output from the switched DAC are output as a beam light amount offset adjustment signal S14 and a total signal offset adjustment signal S15, respectively.
[0118]
  Therefore, the main gain signal S3 or the main sub-sum signal S5 from which the offset is accurately removed regardless of the type of the optical disk and the state of information reproduction, information recording, information erasure, etc. with respect to the optical disk, and the beam light amount Since each of the signals S6 can be input, normalization processing without the influence of offset can be performed in the normalization circuit 22, and accurateReflected light quantityCan be measured.
[0119]
  In this way, information is being reproduced or information is being recorded or erased
The electrical offset amount applied to the beam light amount signal, the main sum signal, and the main sub sum signal can be switched depending on the state, so that the electrical offset can be accurately removed regardless of the above state.Reflected light intensity normalization circuitCan be provided.
[0120]
【The invention's effect】
  As explained above, the present inventionReflected light quantity detection deviceAccording to the above, when a plurality of beam spots having different light amounts are irradiated onto the recording medium, the recording medium is accurate and stable.Reflected light quantityCan be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram according to claim 1 of the present invention;Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitIt is a block diagram which shows the structure of these.
FIG. 2 is a diagram according to claim 2 of the present invention;Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitIt is a block diagram which shows the structure of these.
FIG. 3 is a diagram according to claim 3 of the present invention;Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitIt is a block diagram which shows the structure of these.
FIG. 4 is a diagram according to claim 4 of the present invention;Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitIt is a block diagram which shows the structure of this normalization circuit block.
FIG. 5 is a diagram according to claim 5 of the present invention;Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitIt is a block diagram which shows the structure of this normalization circuit block.
FIG. 6 is a diagram according to claim 6 of the present invention;Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitIt is a block diagram which shows the structure of this normalization circuit block.
FIG. 7 is a diagram according to claim 7 of the present invention;Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitIt is a block diagram which shows the structure of this normalization circuit block.
FIG. 8 is a diagram according to claim 8 of the present invention;Reflected light quantity detection deviceIs an embodiment ofReflected light intensity normalization circuitIt is a block diagram which shows the structure of this normalization circuit block.
[Explanation of symbols]
1: Pickup module
2: LD control circuit 3: CPU
4-7: Adder circuit 10: Main signal normalization circuit
11: Main / sub signal normalization circuit
20: Normalization circuit block
21, 50, 60: Analog switch
22: Normalization circuit 30-32: Variable gain amplifier
40: DAC for beam light quantity offset adjustment
41: DAC for total signal offset adjustment
51: First beam light amount offset adjustment DAC
52: Second beam light amount offset adjustment DAC
61: First sum signal offset adjustment DAC
62: Second sum signal offset adjustment DAC
S1: Main beam signal S2: Sub beam signal
S3: Main sum signal S4: Sub sum signal
S5: Main / sub total signal S6: Beam light quantity signal
S7: LD control signal
S8: Normalized signal selection signal
S9 to S11: Variable gain control signal
S12, S13: Offset adjustment DAC selection signal
S14: Beam light quantity offset adjustment signal
S15: Total signal offset adjustment signal

Claims (7)

A light emitting means for emitting light;
Beam spot irradiating means for irradiating the recording medium with a main beam spot with a large amount of light and a sub beam spot with a small amount of light based on the light emitted by the means;
Main sum signal output means for receiving reflected light of the main beam spot irradiated by the means and outputting a main sum signal that is the sum of the received reflected light;
A main sub sum signal that receives reflected light of the sub beam spot irradiated by the beam spot irradiation means and outputs a main sub sum signal that is a sum of the sub sum signal that is the sum of the received reflected light and the main sum signal. Output means;
A light amount detecting means for detecting the light amount of the light emitted by the light emitting means;
Main sum signal normalizing means for normalizing the main sum signal based on the amount of light detected by the means;
It reflected light detecting apparatus characterized by comprising a main sub sum signal normalizing means for normalizing the main sub-sum signal based on the detected light amount by the light amount detecting means. In the reflected light amount detection device according to claim 1,
A light amount detecting means for detecting the light amount of the light emitted by the light emitting means;
A main sum signal / main sub sum signal selection means for selecting one of the main sum signal and the main sub sum signal;
Main sum signal / main sub sum signal normalizing means for normalizing the main sum signal or main / sub sum signal selected by the main sum signal / main / sub sum signal selecting means based on the light quantity detected by the light quantity detecting means And a reflected light amount detection device . In the reflected light amount detection device according to claim 1 or 2 ,
Pre-normalized main sum signal / main sub sum signal voltage gain changing means for changing the voltage gain of the main sum signal before normalization or the main sub sum signal in a plurality of stages based on the reflectance of the recording medium is provided. A reflected light amount detection device characterized by the above. In the reflected light amount detection device according to any one of claims 1 to 3 ,
A reflected light amount detecting device, comprising: a light amount voltage gain changing means for changing a voltage gain of the light amount detected by the light amount detecting means in a plurality of stages. In the reflected light amount detection device according to any one of claims 1 to 4 ,
A reflected light amount detecting device, comprising: a normalized main sum signal / main sub sum signal voltage gain changing means for changing a voltage gain of the normalized main sum signal or main sub sum signal in a plurality of stages. In the reflected light amount detection device according to any one of claims 1 to 5 ,
A reflected light amount detection device comprising an offset removing means for removing an electrical offset between the main sum signal and the main sub sum signal before normalization, or an electrical offset of the light amount detected by the light amount detecting means. . In the reflected light amount detection device according to claim 6 ,
A reflected light quantity detection device comprising offset removal amount changing means for changing an offset removal amount by the offset removal means in accordance with a reproduction state, a recording state, an erasure state, or a type of the recording medium with respect to the recording medium .

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