JPH08335361A - Disk detecting mechanism - Google Patents

Abstract

PURPOSE: To detect a difference of a protective layer of a disk in thickness with high accuracy with a simple structure by making it unaffected by various factors such as a detecting element, a positioning error of the disk and a warp of the disk, etc. CONSTITUTION: A housing part 12a in a tray 12 is formed with supporting parts 16a, 16b and 16c. Then, an opening hole 12c bored halfway in the radial direction in the vicinity of an opening part 12b in the tray 12. A light emitting element 14 and a light receiving element 18 provided on an optical disk player main body 11 are faced on the opening hole 12c during the loading time. Then, the optical disk 15 is supported under the state of its housing in the housing part 12a of the tray 12 by the supporting parts 16a, 16b and 16c in contact with the surface of the optical disk 15. Then, the optical disk 15 is automatically rotated by driving a spindle motor 17. In this constitution, a difference of the protective layer of the optical disk in thickness is detected with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for recording and reproducing information using, for example, an optical disc as a recording medium, and more particularly to a disc detecting mechanism for detecting plural types of optical discs having different sizes.

[0002]

As is well known, an optical disk is used as a recording medium, such as a write-once optical disk drive device.
In a system for recording or reproducing information, in order to record or reproduce information on optical disks having different sizes, by detecting the size of the optical disk, based on this detection result, A disc detection mechanism for recording or reproducing data according to different optical discs is provided.

FIG. 9 shows such a conventional disk detection mechanism. That is, reference numeral 11 in the drawing is an optical disk player main body, and a tray 12 is provided on the right side surface thereof. The tray 12 is selectively slid in the direction shown by an arrow A or B in the figure by operating an unillustrated take-out mechanism of the optical disc player main body 11. A storage portion 12a having a substantially circular groove shape is formed on the upper surface of the tray 12, and a substantially disk-shaped optical disk (not shown) is stored in the storage portion 12a.

Further, the storage portion 12a of the tray 12 is formed with a substantially elongated hole-shaped opening portion 12b facing an optical head for recording or reproducing information signals from the substantially central portion thereof in the radial direction of the optical disc. ing. Also, this opening 1
A disc table of a disc rotation device (not shown) for rotating the optical disc faces 2b.

As shown in FIG. 10, a photosensor 13 for detecting the size of the optical disk to be selectively mounted is provided below the storage portion 12a of the tray 12. The photosensor 13 is composed of an optical system element such as a photodiode or a phototransistor that generates light and receives the light.

Here, the photo sensor 13 is the tray 1
When, for example, an LD (Laser Disk) is mounted in the second housing 12a, the light reflected from the signal recording surface of the optical disc is received, and therefore the ON state is determined and the LD is determined. In addition, the photo sensor 13 is provided when, for example, a CD (Compact Disk) is mounted in the storage section 12a of the tray 12,
Since the light reflected from the signal recording surface of the optical disk is not received, it is turned off and it is judged that it is a CD.
Since the photo sensor 13 is provided near the position of the storage section 12a of the tray 12, the size of the optical disk is immediately detected when the optical disk is mounted in the storage section 12a of the tray 12. Become. And
Based on the detection result of the photo sensor 13, the optical head built in the optical disc player main body 11 in FIG. 9 is immediately moved to the target position by the moving mechanism (not shown).

On the other hand, in FIG. 11, another mechanism for measuring the thickness and minute gap of the transparent protective layer of the optical disk is considered. Here, a device called an interferometer that applies the interference of light is widely used. In FIG. 11, reference numeral 14 in the figure denotes a light emitting element, which irradiates the surface of the optical disc 15 with a light beam of a single wavelength such as a laser beam C. Then, the laser light C emitted from the light emitting element 14
Is reflected by hitting the signal recording surface 15b of the optical disc 15 and received by a light receiving element such as a photodetector (not shown).

Here, the laser light C is transmitted to the optical disc 1
The thickness of the protective layer 15a of the optical disc 15 can be known by illuminating the five surfaces and observing the brightness of the interference light at the same time. The laser light C enters the incident point D and is refracted into the protective layer 15a in the direction of the reflection point E. Then, the laser beam C refracted by the protective layer 15 a is reflected by the signal recording surface 1 of the optical disc 15.
It is reflected by hitting the reflection point E of 5b, travels in the direction of the reflection point F, and is refracted in the direction indicated by the arrow G in the figure. Further, the laser light C strikes the incident point D and is reflected, so that the laser light C travels in the direction indicated by the dotted line in the figure.

Here, the value obtained by multiplying the optical path difference DEF by the refractive index n of the protective layer 15a is called the optical distance. That is,
The reflected light whose optical distance is a natural number of wavelengths causes interference and becomes bright. Further, the reflected light that is an integral multiple of the half wavelength becomes dark. Therefore, the thickness of the protective layer 15a can be calculated by measuring the intensity of the reflected light. Further, when a light beam having a plurality of wavelengths such as a light bulb is irradiated, only the light beam having a wavelength such that the optical distance, that is, the difference DEF × n, becomes an integer of the wavelengths selectively causes interference and becomes bright. By observing the reflected light component to see which wavelength of the color is bright, the protective layer 1
The thickness of 5a can be calculated.

By the way, in the optical disk 15 which can be measured by utilizing the light interference as described above, the protective layer 15a thereof is very thin, and it is required to be 1/2 to several times the wavelength of light. However, the current optical disc 15 such as a CD
Since the protective layer has a thickness of several tenths of mm to several mm, there is a problem that a measurement method using interference is impossible.

[0011]

As described above, the conventional disc detection mechanism has the same outer dimensions but different thicknesses of only the protective layer, that is, the thickness from the protective layer surface to the signal recording surface of the disc. However, there is a problem that it is difficult to discriminate between different objects.

The object of the present invention is not affected by various factors such as a detection element, a disc position error, a disc warp, etc., and has a simple and economically advantageous structure, and can accurately detect the difference in the thickness of the protective layer of the disc. It is to provide a disc detection mechanism capable of detecting the above.

[0013]

The disc detecting mechanism according to the present invention is capable of rotatably storing or taking out an optical disc having a signal recording surface and a protective layer provided above the signal recording surface. A housing means that is inserted into and ejectable from the main body, a light emitting element that is arranged so as to face the signal recording surface of the optical disk housed by the housing means, and irradiates the optical disk surface with laser light at a predetermined inclination, A light receiving element for receiving the reflected light from the optical disc, and a detection means for detecting the difference in the amount of reflected light from the optical disc due to the difference in the position in the thickness direction between the signal recording surface of the optical disc and the surface of the protective layer through the light receiving element. Is provided.

Further, the disc detecting mechanism according to the present invention detects at least the light emitting element for irradiating the optical disc surface with the laser beam, the light reflected on the protective layer surface of the optical disc and the light reflected on the signal recording surface of the optical disc. One light-receiving element, and a calculating means for calculating the thickness of the protective layer from the position error between the light reflected on the protective layer surface of the optical disc and the light reflected on the signal recording surface of the optical disc to identify the type of the optical disc. It was done like this.

[0015]

According to the above construction, the light emitting element and the light receiving element are arranged so as to face the optical disk housed in the tray, and the light emitting element irradiates the optical disk surface with a laser beam at a predetermined inclination. Since the irradiated laser beam is received by the light receiving element, the arrival distance of the reflected light on the light receiving surface can be different due to the difference in the thickness of the protective layer of the optical disc, so that the type of the optical disc can be easily identified.

Further, by directly arranging the light emitting element and the light receiving element on the tray, supporting the optical disk by the three supporting portions, or arranging the light emitting element and the light receiving element in the vicinity of the supporting portions,
It is possible to perform highly accurate detection that is not affected by position errors or optical disk warpage.

Further, since the light receiving element detects the light reflected on the surface of the protective layer of the optical disk and the light reflected on the signal recording surface, the influence of the positional error between the light receiving element and the optical disk or the warp of the optical disk. It is possible to detect with high accuracy without being affected.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 1, the same parts as those in FIG. The difference from the mechanism of FIG. 9 is that a plurality of (three in the illustrated case) support portions 16a, 16b, 16c are provided in the storage portion 12a of the tray 12 as the storage means.
Are different in that they are formed in a predetermined arrangement. Another difference from the mechanism shown in FIG. 9 is that a cutout hole 12c is formed near the opening 12b of the tray 12 in the radial direction. Among these, the light emitting element 14 and the light receiving element 18 provided inside the optical disc player main body 11 face the cutout hole 12c during the loading operation. Further, the support parts 16a, 16b, 16c will be described later in detail, but the optical disk 15 is stored in the storage part 12a of the tray 12.
In the state where the optical disc 15 is housed in the optical disc 15, the optical disc 15 is brought into contact with and supported by the surface of the optical disc 15, so that the warp generated on the optical disc 15 can be suppressed.

Here, the tray 12 has a storage portion 12a.
When the optical disc 15 is housed in the optical disc 15 and is mounted in the optical disc player main body 11 in the direction indicated by the arrow A in the figure, first, the optical disc 15 is inserted through the cutout hole 12c.
The light emitting element 14 and the light receiving element 18 face the surface of the optical disk player, and after that, they are mounted on the spindle motor 17 rotatably supported inside the optical disk player body 11. In this case, the optical disk 15 housed in the housing section 12a of the tray 12 is placed on a turntable (not shown) driven by the spindle motor 17 and rotated. At this time, the optical disc player main body 11
In the optical disc player device including the above, the optical disc 15 is automatically rotated when the tray 12 is closed, and, for example, enters a recording / reproducing standby state. Although the tray system is adopted in the operation of inserting and ejecting the tray 12, it goes without saying that the same effect can be obtained even if a mechanism such as a kangaroo pocket system is adopted.

Next, FIG. 2 shows a positional relationship between the optical disk 15 and the light emitting element 14 when the optical disk 15 faces the light emitting element 14 through the cutout hole 12c. That is, the light emitting element 14 and the light receiving element 18 are arranged near the lower side of the cutout hole 12c of the tray 12.
Then, the laser beam emitted from the light emitting element 14 is passed through the notch hole 12c at a predetermined angle and the optical disc 1 is emitted.
5 is irradiated. Further, the laser light applied to the optical disk 15 hits the surface of the optical disk 15, is reflected, and is received by the light receiving element 18 through the notch hole 12c. Although the light emitting element 14 and the light receiving element 18 are provided separately from the tray 12 here, the light emitting element 14 and the light receiving element 18 may be arranged on the back surface of the tray 12. At this time, it is not necessary to consider the play error at the time of inserting the elements 14 and 18 and the tray 12 into the optical disk player main body 11, so that the detection accuracy is improved.

Here, the optical disc 15 accommodated in the tray 12 obtains laser light from the light emitting element 14 by passing through the notch hole 12c above the light emitting element 14 and the light receiving element 18 during loading. I am trying. That is, the light receiving element 18 can detect reflected light only at the moment when the cutout hole 12c passes above the light emitting element 14 and the light receiving element 18, and the timing for detecting the optical disk 15 can be set arbitrarily. Therefore, by setting the detection timing, it is not necessary to provide a switch or the like each time. The optical disc 15 stored in the tray 12
Of course, when the loading is completed, the laser light from the light emitting element 14 may be obtained through the notch hole 12c. In short, in this example,
Before the optical disc 15 is mounted on the disc table in the optical disc player main body 11, the thickness of the protective layer 15a of the optical disc 15 can be detected in advance.
It is possible to shorten the access time from the storage of 5 in the tray 12 to the recording and reproduction.

Here, as shown in FIG. 3A, when an optical disc 19 (for example, H = 0.6t) having a thin protective layer is inserted into the optical disc player main body 11, the reflected light of the optical disc 19 becomes Light receiving portion 18a of light receiving element 18
Is received at the position. At this time, the light emitting element 14 is used while being inclined at a predetermined angle. Here, in order to show the above-mentioned optical disks 15 by type, the optical disk 1
It is divided into 9 and 20. Further, as shown in FIG. 3B, when an optical disc 20 with a thick protective layer (for example, I = 1.2t) is inserted into the optical disc player main body 11, the reflected light of the optical disc 20 is received by the light receiving element 18. The light is received at the position of the portion 18b. Therefore, by disposing the light receiving element 18 at a predetermined position, the optical disc 1 that is selectively inserted due to the difference in the position of the reflected light (the difference in the amount of reflected light).
The difference between the thicknesses H and I of the protective layers 19a and 20a of the 9 and 20 is detected.

Since the light emitting element 14 and the light receiving element 18 are provided in the vicinity of the tray insertion opening of the optical disc player main body 11, the tray storing the optical discs 19 and 20 in the optical disc player main body 11 is provided. At the start of inserting the optical disc 12, the thicknesses H and I of the protective layers 19a and 20a of the optical discs 19 and 20 are detected. Then, based on the detection result from the light receiving element 18, recording / reproduction corresponding to each of the optical discs 19 and 20 is immediately performed.

Next, FIG. 4 shows a state where the optical disc 19 has a warp angle θ. Here, the optical disc 19 with a thin protective layer shown by the dotted line in the drawing is the storage unit 12 of the tray 12.
When contacted with a, it may be bent upward or downward in the drawing. Here, the optical disc 2 having a thick protective layer
At 0, warpage or the like is not generated. In this case, in the detection of the optical disc 20 without the warp and the optical disc 19 with the warp, the laser beams reflected from the signal recording surfaces of the optical discs 19 and 20 are received at the same position of the light receiving element 18, so that each protection is performed. It is conceivable that the optical disks 19 and 20 may be erroneously recognized as the same although the layers 19a and 20a have different thicknesses. As a cause of this, first, it is considered that the storage portion 12a of the tray 12 receives the entire optical disk surface.

Therefore, as shown in FIG. 5, the tray 12 has the above-mentioned supporting portions 16a, 16b, 1 in its storage portion 12a.
6c (only 16a is shown in the figure) are provided at predetermined intervals. Then, an optical disc 19 having a thin protective layer
The support portions 16a, 16b, 16c in the bent state.
The slant angle θ1 with the storage portion 12a can be made minute in terms of detection by being supported by. Therefore, the optical disc 1
There is a difference in the light receiving position of the reflected light J of 9 and the reflected light K of the optical disc 20 with respect to the light receiving surface of the light receiving element 18, which allows easy identification.

The cutout hole 12c of the tray 12 is also provided.
Is located on the inner peripheral side with respect to half the radius of the optical disks 19 and 20. This is because even if the optical disc is warped, the degree of warpage on the inner peripheral side is small. Therefore, highly accurate detection can be performed without being affected by warpage or the like caused by the optical discs 19 and 20.

Next, FIG. 6 shows a second embodiment of the present invention. In FIG. 6, the same parts as those in FIG. 3 is different from that shown in FIG.
4 is arranged so as to be substantially perpendicular to the surfaces of the optical disks 19 and 20, and the reflected light from the optical disks 19 and 20 is received by the two light receiving elements 18 and 18 arranged near the light emitting element 14. The points are different. Then, the output signal output from each of the light receiving elements 18 and 18 is calculated by the calculation circuit 21, and the light receiving element 1 is thus calculated.
It is also different in that the amounts of received light in 8 and 18 are identified.

That is, as shown in FIG. 6A, the light emitting element 14 has a reflection point 1 on the signal recording surface of the optical disc 19.
Laser lights L and M are applied to 9b and 19c, respectively. Further, the laser beams L and M applied to the optical disc 19
Are reflection points 19b, 1 on the signal recording surface of the optical disc 19.
9c, which is reflected and is respectively received by the light receiving elements 18, 18
The light is received by the light receiving portions 18a, 18a. Therefore, the reflected laser lights L and M in the directions shown by arrows N1-N2 in the figure
The position difference or the intensity difference of the light amount can be detected.
Then, the output signals from the light receiving elements 18, 18 are respectively supplied to the arithmetic circuit 21 and are arithmetically operated to be taken out from the terminal 22.

On the other hand, in FIG. 6B, the light emitting element 14 is
Reflection points 20b and 20c on the signal recording surface of the optical disc 20
The laser beams L and M are respectively irradiated on the above. Further, the laser beams L and M applied to the optical disc 20 hit the reflection points 20b and 20c on the signal recording surface of the optical disc 20 and are reflected, and the light receiving portions 18 of the light receiving elements 18 and 18, respectively.
The light is received by b and 18b. Then, the light receiving elements 18, 18
The output signal from each is output to the arithmetic circuit 21 and subjected to the same processing as that in FIG. 6 (a).

Although two light receiving elements 18 are used in FIGS. 6A and 6B, this light receiving element 1
The same effect can be obtained by using a plurality of 8. Next, FIG.
Shows a third embodiment of the present invention. here,
The optical disc 19 will be described as an example. That is, the laser light emitted from the light emitting element 14 to the optical disc 19 at a predetermined angle is refracted by the protective layer 19a of the optical disc 19, and thereafter, the signal recording surface 1 of the optical disc 19 is recorded.
It is reflected by hitting 9b, and follows the path shown by the solid line in the figure to be received by the light receiving portion 23a of the light receiving element 23. Also,
The laser light emitted from the light emitting element 14 to the optical disc 19 is reflected by hitting the surface of the protective layer 19a of the optical disc 19, and is received by the light receiving portion 23b of the light receiving element 23 along the path shown by the dotted line in the figure. That is, the optical disc 19
The laser light applied to the laser light is split into a surface reflection light beam O reflected by the surface of the protective layer 19a and a deep reflection light beam P reflected by the signal recording surface 19b. The surface-reflected light ray O and the deep-layer reflected light ray P are parallel lines having an interval corresponding to the thickness of the protective layer 19a of the optical disc 19. Therefore, when the two reflected light rays O and P are detected by the light receiving element 23 such as a phototransistor, a detection signal showing the characteristic in the figure is obtained.

The light-receiving element 23 has, for example, a plurality of phototransistors arranged in the characteristic x-axis direction in the figure.
All the wirings from the plurality of phototransistors are connected to the arithmetic circuit 21. That is, the arithmetic circuit 21 detects which phototransistor receives and outputs the signal, and performs processing.

In this characteristic, the vertical axis represents the intensity y of the detection signal, and the horizontal axis represents the light receiving position x of the reflected light beam with respect to the light receiving element 23. It should be noted that the horizontal axis may be represented by displacement or time unit. That is, when the reflected light rays O and P are received by the light receiving element 23, the intensity of the detection signal shows a peak at the light receiving position. Then, the peak in the light receiving portion 23a of the light receiving element 23 and the light receiving portion 2
If the interval between the peak in 3b and Δl is Δl, the arithmetic circuit 21 can calculate the thickness of the protective layer 19a based on the interval Δl between the peaks and known values such as the incident angle and the reflection angle.

According to this third embodiment, the reflected rays O,
Even if P is displaced in either direction of the light receiving position x due to surface deviation of the optical disc 19 or the like, the arithmetic circuit 21 performs arithmetic processing based on the interval between the two reflected light beams O and P. The thickness of the protective layer 19a can be accurately calculated.

Next, FIG. 8 shows a fourth embodiment of the present invention. In FIG. 8, the same parts as those in FIG. 7 is different from that shown in FIG.
Is different in that a large number of light detecting means are arranged on the light receiving surface, for example, an image pickup device such as a CCD.
The image pickup device such as CCD conveys the electric charges generated by the reflected light rays O and P along the light receiving surface thereof by the transfer voltage applied from the outside. That is, the light receiving element 23 detects the reflected light rays O and P within the light receiving surface even when the reflected light rays O and P move in any of the directions indicated by the arrows X and Y in the figure due to the movement of the optical disk 19 or the like. It is the one.

That is, according to this embodiment, since the light receiving element 23 can detect the reflected light rays O and P on its light receiving surface, the image recognition circuit 24 calculates the interval between the two reflected light rays O and P. The thickness of the protective layer 19a can be calculated. Therefore, the types of the optical disks 19 and 20 can be identified.

[0036]

As described above in detail, according to the present invention,
Provided with a disk detection mechanism that is not affected by various factors such as a detection element, disk position error, disk warp, etc., and has a simple and economically advantageous structure and can detect the difference in the thickness of the protective layer of the disk with high accuracy. can do.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a disc detection mechanism according to the present invention.

FIG. 2 is a cross-sectional view shown for explaining the positional relationship between the optical disc, the light emitting element, and the light receiving element housed in the tray in the embodiment.

FIG. 3 is a cross-sectional view shown for explaining how reflected light from the optical disc surface is received by a light receiving element in the embodiment.

FIG. 4 is a sectional view showing a detection state when the optical disc according to the embodiment has a warp.

FIG. 5 is a sectional view showing a detection state when the optical disc is supported by a supporting portion in the embodiment.

FIG. 6 is a sectional view showing a second embodiment of the present invention.

FIG. 7 is a sectional view showing a third embodiment of the present invention.

FIG. 8 is a sectional view showing a fourth embodiment of the present invention.

FIG. 9 is a perspective view showing a conventional disc detection mechanism.

FIG. 10 is a sectional view showing a specific configuration of a tray in the conventional mechanism.

FIG. 11 is a sectional view showing another conventional disk detection mechanism.

[Explanation of symbols]

11 ... Optical disc player main body, 12 ... Tray, 12
a ... storage part, 12b ... opening part, 12c ... notch hole, 13
... Photo sensor, 14 ... Light emitting element, 15 ... Optical disk, 15a ... Protective layer, 15b ... Signal recording surface, 16a ... Support section, 16b ... Support section, 16c ... Support section, 17 ... Spindle motor, 18 ... Light receiving element, 18a ... Light receiving part, 18b
... Light receiving part, 19 ... Optical disk, 19a ... Protective layer, 19b
... signal recording surface, 20 ... optical disk, 21 ... arithmetic circuit, 2
2 ... Terminal, 23 ... Light receiving element, 24 ... Image recognition circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Mineharu Uchiyama, 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Kanagawa Prefecture, Multimedia Technology Research Laboratories, Ltd. (72) Masanori Ozawa, 8 Shinsita-cho, Isogo-ku, Yokohama, Kanagawa Banchi Co., Ltd. Inside Toshiba Multimedia Technology Laboratory

Claims (9)

[Claims] 1. An accommodating means capable of rotatably accommodating or ejecting an optical disk having a signal recording surface and a protective layer provided above the signal recording surface, and being supported by an optical disk player body so as to be insertable into and ejectable from the optical disk player main body. And a light emitting element which is arranged so as to face the signal recording surface of the optical disc housed by the housing means and which irradiates the optical disc surface with a laser beam with a predetermined inclination, and receives reflected light from the optical disc. A light receiving element; and a detection means for detecting, via the light receiving element, the difference in the amount of light reflected from the optical disk due to the difference in the position in the thickness direction between the signal recording surface of the optical disk and the surface of the protective layer. A disk detection mechanism characterized by the following. 2. The storage means is provided with a cutout hole, and the light receiving element receives the laser beam reflected from the optical disk only when the cutout hole passes over the light emitting element and the light receiving element. Claim 1 characterized by the above.
The described disk detection mechanism. 3. The disc detection mechanism according to claim 1, wherein the cutout hole is provided at a position corresponding to substantially the inner circumference of the optical disc. 4. The light emitting element and the light receiving element are integrally provided in the storage means in order to determine the type of the optical disk when the optical disk is placed in the storage means. 1. The disk detection mechanism described in 1. 5. The disk arranging portion of the accommodating means is formed with at least three supporting portions on a circumference coaxial with the disc arranging portion, and the light emitting element and the light receiving element are any of the supporting portions. 2. The disc detection mechanism according to claim 1, wherein the disc detection mechanism is disposed at a position close to the. 6. The light emitting element is arranged so as to be substantially orthogonal to the optical disk surface, and the reflected light from the optical disk is received by the light receiving element arranged in the vicinity of the light emitting element. The disk detection mechanism according to claim 1. 7. The output of at least two or more light receiving elements arranged in the vicinity of the light emitting element is calculated,
7. The disc detecting mechanism according to claim 6, wherein the type of the optical disc is identified based on the calculated amount of received light. 8. A light emitting element for irradiating an optical disk surface with a laser beam, at least one light receiving element for detecting light reflected on the surface of the protective layer of the optical disk and light reflected on the signal recording surface of the optical disk, The optical disc further includes a calculating unit that calculates the thickness of the protective layer from the positional error between the light reflected on the surface of the protective layer of the optical disc and the light reflected on the signal recording surface of the optical disc, and identifies the type of the optical disc. A disk detection mechanism characterized by: 9. The light receiving element is composed of, for example, an image pickup element such as a CCD, and an image recognition circuit discriminates between light reflected on the surface of the protective layer of the optical disc and light reflected on the signal recording surface of the optical disc. 9. The method according to claim 8, wherein
The described disk detection mechanism.