JPH07249240A - Optical disk defect inspecting method and optical disc defect inspecting device - Google Patents

Abstract

PURPOSE:To detect the defect on the information surface side of an optical disk. CONSTITUTION:An optical disk 1 is irradiated with a light while inclining the light at a prescribed angle to the normal. Then, the reflected light and plural diffracted lights of the light are received by photodiodes PD1 to PD5. Moreover, outputs of received lights are added by an adding means 2. The defect is detected from the reduction in an added output by a discrimination means 3. Further, the width of the defect is detected from a discriminated output. The inclination of the defect is detected from the reduced level of the added output. Furthermore, the height of the defect can be also detected from these values.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk defect inspection method and a defect inspection apparatus for detecting abnormal surface conditions of various types of optical disks.

[0002]

2. Description of the Related Art In a conventional optical disk defect inspection apparatus, light is illuminated from the mirror surface side of an optical disk for inspection. In a conventional inspection apparatus, for example, as shown in FIG. 13A, a laser diode 102 is arranged on the mirror surface 101a (lower surface in the figure) side of an optical disc 101. Then, the light emitted from the laser diode 102 is condensed by the collimator lens or the focus lens 103 to an arbitrary measurement beam diameter on the mirror surface 101a to be measured on the optical disc 101. The reflected light is condensed by the lens 104 on the photodiode 105, which is a light receiving element, and received, and the light amount of the reflected light is converted into a voltage. Then, the received light signal is amplified by the amplifier 106 to obtain a specular signal. Optical disk 10 here
By rotating 1 to change the light irradiation position, an abnormal state on the surface side of the optical disc 101, that is, a defect such as a protrusion or a dent is detected from the fluctuation of the mirror surface signal due to the abnormal surface state. FIG. 13B is a waveform diagram showing an example of the mirror surface signal, and the abnormality can be detected by the large decrease S in level.

[0003]

However, in the optical disk defect inspection apparatus, there is a demand to detect a defect on the protective coated surface (information surface) 101b of the optical disk, that is, the upper surface side of FIG. 13 (a). In this case, it is conceivable that the protective coat surface is irradiated with laser light and the reflected light is received, as in the case of the inspection device on the mirror surface side. However, a recording film 101c and a reflective film 101d are formed in the optical disc 101 as shown in the figure, and a pre-group and a pit portion for recording information on the optical disc are formed. Since the inclination of the edge of this portion is not uniform, diffracted light is generated even if light is irradiated from the protective coating surface side, and the intensity ratio of reflected light and diffracted light varies. Therefore, even if an attempt is made to detect a defect by amplifying only the reflected light and discriminating it with a predetermined threshold value as in the conventional optical disk defect inspection apparatus, the obtained signal greatly changes as shown in FIG. 13C, Since the noise component N is large and the S / N ratio is bad, there is a problem that normal defect detection cannot be performed.

The present invention has been made in view of the above conventional problems, and it is possible to detect a protrusion defect, a width, an inclination, and a height of the protrusion defect on the protective coating surface (also referred to as an information surface) of an optical disk. Is a technical issue.

[0005]

According to the invention of claim 1 of the present application, the optical disk is moved along its surface, irradiated with light inclined at a predetermined angle from the direction perpendicular to the information surface of the optical disk, and reflected from the optical disk. Received reflected light and diffracted light in their respective light-receiving areas, add the received light signals of the reflected light and diffracted light,
By discriminating the added light receiving signal with a predetermined threshold,
It is characterized in that a defect occurring on the information surface of the optical disc is detected based on the decrease in the level of the received light.

According to a second aspect of the present invention, the optical disk is rotationally driven at a constant rotational speed, a clock signal having a cycle inversely proportional to the traveling speed of the optical disk at the light beam irradiation position is generated, and the clock signal is used. It is characterized in that the time for which the discrimination output is obtained is counted and the width of the defect is detected based on the counted output.

According to a third aspect of the present invention, the optical disk is rotationally driven at a rotational speed that is inversely proportional to the radius r from the center of rotation to the irradiation position of the light beam to generate a clock signal of a constant period and use the clock signal. The discrimination output is counted and the width of the defect is detected based on the counted output.

The invention according to claim 4 of the present application is characterized in that, when a signal of a predetermined value or less is detected by the discriminating means, the inclination angle of the defect is detected on the basis of the lowered level of the signal. .

According to a fifth aspect of the present invention, the optical disc is rotationally driven at a constant rotational speed, the light is irradiated at a predetermined angle with respect to the direction perpendicular to the information surface of the optical disc, and the reflected light and the diffracted light reflected from the optical disc are diffracted. Light is received in each light receiving area, the received light signals of reflected light and diffracted light are added, and the added received light signal is discriminated by a predetermined threshold to detect a decrease in the light reception level, and the discriminating means detects the light reception level to be a predetermined value or less. When the signal of is detected, the inclination angle of the defect is detected based on the level of decrease of the signal, and a clock signal having a cycle inversely proportional to the traveling speed of the optical disc at the irradiation position of the light beam is generated, and the clock signal is used. The width of the defect is detected by counting the discrimination output according to the above, and the height of the defect is detected based on the count output and the inclination of the defect.

According to a sixth aspect of the present invention, the optical disk is rotationally driven at a rotational speed that is inversely proportional to the radius from the center of rotation to the irradiation position of the light beam, and the optical disk is inclined at a predetermined angle from the direction perpendicular to the information surface of the optical disk. The reflected light and the diffracted light reflected from the optical disc are received in their respective light receiving areas, the received light signals of the reflected light and the diffracted light are added, and the added received light signal is discriminated by a predetermined threshold value, thereby receiving light. When a signal lower than a predetermined value is detected by the discriminating means by detecting the level drop, the inclination angle of the defect is detected based on the signal drop level, a clock signal of a constant cycle is generated, and the clock signal is used. The width of the defect is detected by counting the time at which the discrimination output is obtained, and the height of the defect is detected based on the counting output and the inclination angle of the defect.

According to a seventh aspect of the present invention, there is provided an optical disk moving means for moving the optical disk along its surface, a light projecting section for irradiating light at a predetermined angle with respect to a direction perpendicular to the information surface of the optical disk, and an optical disk. A light-receiving unit that receives reflected reflected light and diffracted light at their respective light-receiving positions, an addition unit that adds each light-receiving signal obtained from the light-receiving unit, and a light-receiving signal that is added by the addition unit is discriminated by a predetermined threshold value. And a discriminating means for detecting a decrease in the received light level.

According to the invention of claim 8 of the present application, the optical disk moving means rotationally drives the optical disk at a constant rotational speed, and generates a clock signal having a cycle inversely proportional to the traveling speed of the optical disk at the irradiation position of the light beam. And a defect width detecting means for detecting the width of the defect by counting the output of the clock signal generating means based on the discrimination output of the discriminating means.

According to the invention of claim 9 of the present application, the optical disc moving means drives the optical disc while keeping the traveling speed of the optical disc constant at the irradiation position of the light beam, and the discrimination output of the discriminating means is a clock signal having a constant cycle. Defect width detecting means for detecting the width of the defect on the information surface side of the optical disc by counting

The invention of claim 10 of the present application is based on the peak value detecting means for detecting the width of the decrease in the output of the adding means at the position where the defect occurs as a peak value, and the peak value detected by the peak value detecting means. Defect inclination angle detecting means for detecting the inclination angle of the defect.

The invention according to claim 11 of the present application comprises an optical disk drive means for rotationally driving the optical disk at a constant rotational speed,
A light projecting unit that irradiates light at a predetermined angle with respect to a direction perpendicular to the information surface of the optical disc, a light receiving unit that receives reflected light and diffracted light reflected from the optical disc at respective light receiving positions, and a light receiving unit that receives light. Adding means for adding the received light signals of
Discrimination means for detecting a decrease in the light reception level by discriminating the light reception signals added by the addition means with a predetermined threshold value,
An information surface side of an optical disk by counting the output of the clock signal generating means based on the discrimination output of the clock signal generating means and the discrimination means for generating a clock signal having a cycle inversely proportional to the traveling speed of the optical disc at the irradiation position of the light beam. Defect width detection means for detecting the width of the defect, peak value detection means for detecting the width of the decrease in the output of the addition means at the position where the defect occurs as a peak value, and the peak value detected by the peak value detection means. Defect inclination angle detecting means for detecting the inclination angle of the defect based on the defect width; and defect height detecting means for detecting the height of the defect based on the outputs of the defect width detecting means and the defect inclination angle detecting means. It is a feature.

According to a twelfth aspect of the present invention, the traveling speed is constant depending on the light projecting portion that irradiates light at a predetermined angle with respect to the direction perpendicular to the information surface of the optical disk and the light projecting position of the optical disk. An optical disk moving means that moves along the surface thereof, a light receiving section that receives reflected light and diffracted light reflected from the optical disk at their respective light receiving positions, and an adding means that adds received light signals obtained from the light receiving section, Discrimination means for discriminating the received light added by the addition means by a predetermined threshold to detect a decrease in the light reception signal level, and the information surface side of the optical disc by counting the clocks of a constant cycle based on the discrimination output of the discrimination means. The defect width detection means for detecting the width of the defect, the peak value detection means for detecting the width of the decrease in the output of the addition means at the position where the defect occurs as the peak value, and the peak value detection means. Defect inclination angle detecting means for detecting the inclination angle of the defect based on the detected peak value, and defect height detecting means for detecting the height of the defect based on the outputs of the defect width detecting means and the defect inclination angle detecting means. And are provided.

[0017]

According to the inventions of claims 1 and 7 having the above characteristics, light is irradiated from the information surface side of the optical disc while being inclined from the normal line, and reflected light and diffracted light thereof are received and added. , The defect of the optical disc is detected based on the decrease of the addition level. Further, in the inventions of claims 2 and 8, the size of the defect is detected by rotationally driving the optical disk at a constant rotational speed and counting the discrimination output based on a clock signal having a cycle inversely proportional to the traveling speed of the optical disk. I am trying. Further, in the invention of claim 3 or 9, the rotation speed is controlled so that the traveling speed of the optical disk is constant at the irradiation position of the optical disk, and the pulse number of the constant clock is counted based on the output discriminated by the discriminating means. By doing so, the width of the defect on the information surface of the optical disc is detected. Further, in the invention of claims 4 and 10 of the present application, since the decrease level of the output of the adding means corresponds to the inclination of the defect, the angle of the inclination of the defect is detected based on the decrease level. Further claims 5, 6, 11 and 12
In the invention, the width and angle of the defect are detected, and the height of the defect is detected from these values.

[0018]

1 is a diagram showing a schematic structure of an optical disc defect inspection apparatus according to an embodiment of the present invention, and FIG. 2 is a sectional view showing an example of an optical disc. The lower surface of the base 1a of the optical disc 1 is formed into a mirror surface, and the upper surface thereof has pits and grooves 1b for recording information. A recording film 1c and a reflective film 1d are further formed on the upper surface of the base 1a where the pits and the grooves 1b are formed, and a protective coat 1e is formed on the recording film 1c and the reflective film 1d. The surface on the protective coat side is called the information surface. As shown in FIGS. 1 and 2, when a light beam is incident at a predetermined angle from the normal line perpendicular to the information surface, diffracted light is generated at an angle defined by the groove pitch. In FIG. 1, when the inclination angle of the incident light from the normal is θin, the reflected light is reflected at an angle θ ₀ equal to θin with respect to the normal, and part of it is diffracted. This reflected light is called 0th order light. The diffracted light is called 0th order light (reflected light), 1st order light, 2nd order light, ... Further, the angles from the 0th-order light to the 1st-order light and the 2nd-order light due to diffraction are respectively set as θ ₁ and θ ₂ . The diffracted lights emitted to the incident light side are referred to as the 1'th order light and the 2'th order light, respectively, and the angles from the 0th order light are θ _-1 and θ _-2 , respectively.

FIG. 3 shows the principle of generation of reflected light and diffracted light. The pitch of the pits irradiated with parallel incident light is d
The first-order diffracted light is generated at an angle whose path difference is equal to the wavelength of the light source. That is, the angle of the primary reflected light from the normal is θa
(Θa = θ ₀ + θ ₁ ), where λ is the wavelength of light, when the path difference d2 of the first-order diffracted light has the following relationship with the path difference d1 of the incident light, the first-order diffracted light is generated. d2-d1 = d {sin (θ ₀ + θ ₁ ) −sin θin} = λ Similarly, second-order diffracted light is generated at an angle where the optical path difference is 2λ. d2-d1 = d {sin (θ ₀ + θ ₂ ) −sin θin} = 2λ Further, the 1′-order light and the 2′-order light are θ ₁ , θ in the above equation.
_This holds when ₂ is replaced by θ ₋₁ and θ ₋₂ , respectively.

When laser light is emitted from the mirror surface side, the intensity ratio of each diffracted light is almost constant. Therefore, in order to detect a defect from the mirror surface side, it is sufficient to receive only the 0th order light. However, as described above, when light is incident from the information surface side, 0th order light, 1,
1 ', 2, 2' ... The intensity ratio of the next light changes. This is because the recording film 1 has unevenness such as pits and grooves 1b on the information surface side.
This is because the level of each diffracted light fluctuates depending on the incident position of the light because the c and the reflection film 1d are formed and the shapes of the pits and grooves are not normally traced. However, if there is no defect, the total sum of these received light amounts does not change, and the ratio thereof only changes. The present invention has been made based on such a principle.

FIG. 1 shows the concept of an optical disk defect inspection apparatus according to the present invention. An optical disk 1 is irradiated with laser light from a laser diode LD which is a laser light source, and its 0th-order reflected light, 1, 1′-order light, The 2nd and 2'th order lights are received by the photodiodes PD1 to PD5, respectively, and the output thereof is converted into a voltage. Then, the addition means 2 adds them to obtain a light reception signal. If there is no defect, this addition signal has a substantially constant level, and if there is a defect, the level is lowered. Therefore, the discriminating means 3 discriminates this output with a predetermined threshold value, and detects a defect and outputs it when the output is below a predetermined value. This makes it possible to detect the presence or absence of defects. In addition to this,
The defect width is determined from the output width of the discrimination means 3 to the defect width detection means
Detect by. Further, the peak value detecting means 5 calculates the difference between the normal level and the lowest level of the output of the adding means 2. In this way, the defect inclination detecting means 6 can detect the inclination of the defect based on the peak value.
Then, based on the defect width and the peak value, the defect height detecting means 7 detects the defect height by a method described later.

Now, the fluctuations of the reflected light and the diffracted light when there are protrusion defects on the information surface of the optical disk will be described. FIG. 4 is a view showing the laser diode and the photodiode from the side of the paper surface of FIG. Assuming the defect is conical,
It is assumed that there is no absorption of measurement light due to defects or scattering under other than angular conditions. In FIG. 4, W is the width of the measurement beam on the light receiving surface, which also matches the width of the projected beam. Further, D indicates a light receiving surface of a light receiving element, for example, a photodiode, which is wider than the beam width W. Here, if there is no defect, all the incident light becomes reflected light or diffracted light as described above. FIG. 4A shows this state.

When _a defect having an angle α _a occurs as shown in FIG. 4B and light is incident on this slope, the reflected light is displaced from the center of the light receiving surface D of the photodiode. If the distance moved from the center of the light receiving surface is M,
When the end of the reflected light exceeds the position where it contacts the light receiving surface D of the photodiode, the amount of reflected light decreases. FIG. 4B shows a limit point at which the amount of received light decreases, and the distance M ₁ that the reflected light moves from the center of the light receiving surface is expressed by the following equation M ₁ = (D−W) / 2. When M is M ₁ or less, the light amount does not decrease, but when M exceeds M ₁ , the light amount decreases. Angle α at this time
_a is expressed by the following equation, where L is the distance between the photodiode and the optical disk. α _a = tan (M ₁ / L) If the height H of the defect in FIG. 4 is Ha to Hc,
Since Ha, Hb, and Hc << L, L−H = L.

Further, when the angle of the defect in which the center of the reflected light corresponds to the end of the light receiving surface is α _b , it becomes as shown in FIG. 4C, and the moving distance M _{2 at} this time is shown by D / 2.

Further, when the limit moving distance at which the end of the reflected light is not reflected by the photodiode is M ₃ and the angle is α _c as shown in FIG. 4D, the moving distance M ₃ is M ₃ = (D + W ) / 2. The angle α _{c at} this time is α _c = tan (M ₃ / L). Therefore, the detectable tilt angle α is between the moving distances M _{1 to} M ₃ and is represented by the following equation.

[Equation 1]

The waveforms shown in the lower portions of FIGS. 4A and 4B are graphs showing changes in the reflection level when the optical disc is moved in parallel along its surface at a constant speed.

FIG. 5A is a diagram showing the output of the adding means 2 shown in FIG. 1 when the optical system of the optical disc 1 or the light emitting / receiving unit is scanned at a constant speed. When the position where the light beam becomes a defect is irradiated, the output level from the adding means 2 decreases as shown in FIG. 5 (a). Therefore, if the output of the adding means 2 is lowered, the width W _D of the time when the output is below the predetermined threshold value Vth corresponds to the size of the defect. Times t _{1 to} t ₂ show a state in which the light beam irradiates a position having a relatively large defect and t _{3 to} t ₄ has a small defect. The length on the optical disc 1 corresponding to the time width obtained by binarizing this is W _D
Then, W _D is the size of the defect.

Assuming that the defect has a conical shape as shown in the side view of FIG. 6A, since W _D has its width, the inclination α and the height H of the defect have the following relationship. Indicated by.

[Equation 2] Therefore, the height H of the defect is expressed by the following equation. H = (W _D / 2) ・ tan α ・ ・ ・ (3)

In FIG. 4, the magnitude of the voltage Vx that drops from the steady level corresponds to the defect inclination α as shown in FIG. FIG. 6B is a graph showing the relationship between the inclination angle α of this defect and the voltage drop Vx. As the inclination angle α increases within the range of detectable inclinations α _{a to} α _c. The voltage Vx will increase. The peak value detecting means 5 shown in FIG. 1 detects this voltage Vx. If this Vx is calculated, the value of the inclination angle α of the defect can be calculated from a fixed relationship. Therefore, using the inclination angle α and the size W _D of the defect, the height H of the defect is calculated by the equation (3).
Can be detected. The defect height detecting means 7 of FIG. 1 detects the height H of the defect by such a method.

Next, the overall structure of the optical disc defect inspection apparatus according to the embodiment of the present invention will be described with reference to FIG. In the figure, the optical disc 1 is driven by a rotation drive unit 11 at a constant rotation speed (n rps).
A rotary encoder (R
E) 12 is connected, and the logical product signals of the A phase and the B phase are connected to the clock input terminal of the circumferential address counter 14 via the AND circuit 13. The Z-phase output of the rotary encoder 12 is input to the circumferential direction address counter 14 as a clear signal, and the circumferential address counter 14 outputs an address in the rotation direction of the optical disc 1.

Here, the optical disc 1 is divided into, for example, 1,000 addresses in the circumferential direction and addresses 0 to 999, as shown in FIG. 8A. A constant width in the radial direction, for example 100μ
It is assumed that a division is made for each length of m and a division is made into a minute fan-shaped area (hereinafter referred to as a matrix) as shown in FIG. 8B, and the presence or absence of a defect is detected for each matrix as described later. . The output of the circumferential direction address counter 14 is input to the height data memory 15 as an address, and the height data memory 15 holds the height data. The height data memory 15 has a storage area of 0 to 999 according to a circumferential address as described later, but is not divided in the radial direction.

As shown in FIG. 1, a laser diode LD for irradiating the optical disk 1 with light at an angle inclined by a predetermined angle .theta.in from a normal line, and its 0th-order light, 1st-order diffracted light, and 1'th-order diffracted light are respectively received. The photodiodes PD1 to PD3 arranged at the positions to be held are held on the optical pickup section 16.
Here, the laser diode LD constitutes a light projecting portion, and the photodiodes PD1 to PD3 constitute a light receiving portion. The optical pickup unit 16 is held by a linear actuator 17 so as to be slidable in the radial direction, and as shown in FIG. 8, is driven in the radial direction at a predetermined circumferential length W _R , for example, every 100 μm. To do. These photodiodes P
The outputs of D1 to PD3 are amplified by the amplifiers 18 to 20, respectively, and the outputs are added by the adder 21. The adder 21 is addition means for adding these outputs,
The output is given to the comparator 22 and the peak hold circuit (PH) 23. The comparator 22 is a discriminating means for discriminating an input signal by a predetermined threshold value Vth and outputting an H level when the input is below this threshold value. The peak hold circuit 23 holds the peak of the decrease in the output of the adder 21 (the lowest level than the steady value, that is, Vx shown in FIG. 5A, and holds the output based on the clear signal from the microcomputer 24. The peak value is input to the A / D converter 25. The A / D converter 25 converts the peak value into a digital signal based on a start signal from the microcomputer. The output is given to the latch circuit 26. The latch circuit 26 temporarily holds this output and inputs it to the microcomputer 24 at a necessary timing.

On the other hand, a linear encoder (LE) 27 is connected to the linear actuator 17. The linear encoder 27 is a unit length of the linear actuator 17 (100
A pair of pulse signals corresponding to the moving direction are output for each movement (μm), and the output is given to the up / down counter (U / D) 28. The up-down counter 28 counts up or down-counts the output of the linear encoder, and outputs the currently scanned radius (r) of the optical disc 1 as a count value. The output of the up / down counter 28 is the PLL circuit 29.
Entered in. A clock generator (OSC) 30 that generates a clock signal of a constant cycle is connected to the PLL circuit 29, and a pulse having a cycle corresponding to a radius r is obtained by dividing the input signal based on the count value of the counter 28. To occur. The period Tr of this pulse changes so as to be inversely proportional to the radius r of the light beam scanning the optical disc 1. By doing so, the product of the rotational speed 2πnr (m / s) and the period Tr at the irradiation position becomes constant. That is, the PLL circuit 29 is set so that the length of the optical disc scanned at the irradiation position during the irradiation time corresponding to the period is always constant. Here, the linear encoder 27, the counter 28, the PLL circuit 29, and the clock generator 30 constitute a clock generating means for generating a clock signal having a cycle inversely proportional to the traveling speed of the optical disc 1. The pulse output of the PLL circuit 29 is given to the AND circuit 31.

The above-mentioned comparator 22 discriminates the output of the adder 21 with a predetermined threshold value, and its output C is inputted to the microcomputer 24 and further given to the AND circuit 31. AND circuit 31 is a one taking the logical product of the pulse signal of the PLL circuit 29, its output is input to W _D counter 32. The W _D counter 32 is a counter that detects the width W _D of the defect by counting this pulse based on a control signal from the microcomputer 24, and its output is sent via the latch circuit 33 at a predetermined timing to the microcomputer. 24 is input.

Next, the operation of this embodiment will be described with reference to the flowchart and time chart. 9 and 1
The flow chart of 0 is a flow chart for detecting the width, inclination and height of the defect, and FIGS. 11 and 12 are time charts when the defect is detected and the relationship between the matrix and the defect. FIGS. 11A to 11D show the case where the defect DF1 does not reach the boundary of the matrix, and the AND circuit 13 outputs the matrix signal T according to the switching of the matrix as shown in FIG. 11B. And The matrix signal T is the time t ₅ that rises, the output C of the comparator 22 checks whether H level proceeds to step 42 from step 41 of FIG. Immediately after the start of the operation, the output C of the comparator 22 is at the L level as shown in FIG. 11C, so the routine proceeds from step 42 to step 43 to check whether or not the defect detection flag F is set. The defect detection flag F is a flag which is set at the same time as the detection of the defect as shown in FIGS.
If there is no defect, the routine proceeds to step 44, where the memory data of that address, that is, the data of the previous cycle is read from the height data memory 15. Then, it proceeds to step 45 and checks whether the value is 0 or not.
In steps 46 and 47, the rise of the output C of the comparator 22 and the rise of the matrix signal T are checked. As shown in FIGS. 11B and 11C, if the output of the comparator 22 rises to the H level in the middle of the matrix due to the detection of the defect DF1 at time t ₆ , step 4
From 6 to 48, the operation of the W _D counter 32 is started. Next, at step 49, the peak hold of the peak hold circuit 23 is started. At this time, since a defect is detected, the routine proceeds to step 50, where the defect detection flag F is set. Then, in steps 51 and 52, the falling edge of the output C of the comparator 22 or the matrix signal T
Check the rise of. In FIG. 11A, since the defect DF1 exists in the middle of the matrix, the comparator 2
The output C of 2 is the time when the next matrix signal T rises.
It is inverted to L level at time t ₇ until t ₈ . Therefore, in this case, the process proceeds from step 51 to 53, and the count value of the W _D counter 32 is latched by the latch circuit 33. Then, the peak hold value of the peak hold circuit 23 is A / D converted and the A / D converted value is latched (steps 54 and 5).
5). Then, in steps 56 and 57, the count value of the W _D counter 32 is cleared, the peak hold circuit 23 is turned off, and the process returns to step 41.

At time t ₈ when the next matrix signal T is output, the routine proceeds from step 41 to step 42 to check whether the output C of the comparator 22 is at H level. In this case, since the scanning of the defect DF1 has already been completed, the routine proceeds to step 43, where the defect detection flag F is checked. This flag because it is erected at step 50 reads the data (W _D) of the latch circuit 33 proceeds to step 60 from step 43. Similarly, in step 62, the data (Vx) of the A / D converted value latch circuit 26 is read. Then, the Vx value is calculated as shown in FIG.
The angle α of the defect is calculated by multiplying a predetermined coefficient from the relationship of (b). Then, in step 63, the height Hx of the defect is calculated from the equation (3). Next, in steps 64-66, the data in the latch circuits 33, 26 are cleared and the defect detection flag F is reset. Then, the routine proceeds to step 67, where the memory data of the same address (previous cycle data) is read. Then, the memory data Mn of the previous cycle is compared with the height Hx calculated in step 63 (step 68).
If the previous-cycle data stored in the height memory 15 is larger, the height memory 15 is not updated and the currently detected H
If x is larger, the routine proceeds to step 69, where the memory contents are updated to the present data Hx. Then, returning to steps 46 and 47 in FIG. 10, the same processing is repeated. By doing so, for example, as shown in FIG. 11E, even when the defect DF2 exists at the same address across the boundary of the matrix, only the highest value among them is finally held as the data of that address. It will be.

Next, the case where there is a defect DF3 that crosses the boundary of the matrix at the same radial position as shown in FIG. 12 will be described. Figure 1 shows the operation from time t _{9 to} t ₁₀ .
It is similar to the case of 1. Operation of W _D counter 32 and the peak hold circuit 23 starts the process proceeds from step 48 because the output of the comparator 22 rises to 50 at time t _10, the defect detection flag F is set. Then, in steps 51 and 52, the falling edge of the comparator 22 or the rising edge of the matrix signal T is checked.
_When the rising edge of the matrix signal T is detected at ₁₁ , the routine proceeds to step 42, where the level of the output C of the comparator 22 is checked. At this time, since the comparator C is at the H level, the steps 51 to 51
It returns to the loop of 52 and waits for the fall of the output C of the comparator 22 or the next rise of the matrix signal T. In this way, even when defects continue beyond the boundaries of the matrix, after the end, that is, in the case of FIG. 12, at time t ₁₂ , the count value of the counter is held and peak hold is performed at steps 60 to 69. , These data can be taken and converted into height data.

When the defect detection flag F is reset in step 66, in the subsequent routine, the process proceeds from step 43 to steps 44 and 45 to read the data of the same address. If the data in the memory is not 0, the data in the memory is determined in step 70. In this data determination, for example, a signal indicating that there is a defect may be output when the value exceeds a predetermined value, or the signal may be classified into a plurality of levels according to the height of the defect and output.
Then, in step 71, this determination result is displayed or output to the outside. Next, in step 72, the memory area of the address is cleared and the process returns to steps 46 and 47. In this way, even for defects that occur beyond the boundary of the matrix, its final height Hx can be held at the address of the memory where the defect ends.

In this embodiment, the optical disk 1 is divided at a predetermined angle and a height memory 15 having an address corresponding to the number of divisions is provided, and one data area is provided for each address. Although the memory address is not divided, it goes without saying that it may be configured to hold the data of the respective heights of the respective matrices divided in the angle and radial directions. Further, in this embodiment, the optical pickup section 16 is driven by the linear encoder 17, and the clock signal having the pulse width inversely proportional to the traveling speed of the optical disk based on the driving amount is constituted by the up / down counter and the PLL circuit. , A count value of the up / down counter is once converted into a voltage signal, a VCO that oscillates a frequency based on this voltage signal is provided, the output of this VCO is shaped, and a cycle of a cycle inversely proportional to the traveling speed at the irradiation position of the light beam is provided. It can also be configured to generate a clock signal.

In this embodiment, three photodiodes PD1 to PD3 for receiving the reflected light (0th order light), the 1st order diffracted light, and the 1'diffracted light are provided to simplify the structure. In addition, as shown in FIG. 1, it goes without saying that a photodiode for receiving the second-order diffracted light, the 2′-diffracted light, and the higher-order diffracted light may be provided and these may be added.

Further, in this embodiment, the optical disk is rotationally driven at a constant rotational speed to generate a pulse according to the irradiation position in the radial direction, but the rotational speed is controlled based on the output of the linear actuator. The optical disc may be scanned at a constant speed at the light beam irradiation position. In this case, it is necessary to increase the rotation speed when irradiating the vicinity of the center of the optical disk, and to decrease the rotation speed in inverse proportion to the radius when irradiating the peripheral portion. In this way, the width of the defect can be detected by using the clock signal source having a constant frequency. Further, the optical disc may be linearly driven by an XY recorder to detect a defect. In this case, if the optical disc is moved at a constant speed, the clock pulse for detecting W _D can be a pulse having a constant frequency, so that the configuration of the clock signal generating means can be simplified.

[0042]

As described in detail above, according to the inventions of claims 1 to 12 of the present application, the information beam of the optical disk is irradiated with the light beam, and the reflected light and the diffracted light are received at their respective light receiving positions. Since the defect is detected based on the added value, it is possible to detect the defect on the information surface even when the diffracted light is generated and the level of the reflected light is largely changed. Also, claim 2,
According to the third, eighth and ninth inventions, the width of this defect can be detected when the information surface of the optical disc has a protrusion type defect. In the inventions of claims 4 and 10, the angle of the defect can be detected based on the reduction level of the addition output. In the inventions of claims 5, 6 and 11, 12, the defect angle can be detected based on the width and the angle of the defect. The effect that the height can be detected is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an optical disc defect inspection apparatus of the present invention.

FIG. 2 is a schematic diagram showing changes in reflected light when the optical disc of the present invention is irradiated with light.

FIG. 3 is an explanatory diagram showing a principle of generating diffracted light when a laser beam parallel to an optical disc is irradiated.

FIG. 4 is a diagram showing a relationship between a projected beam and reflected light when a laser beam parallel to a defect having a different angle on an optical disk is irradiated, and a change in a light reception signal at that time.

FIG. 5A is a time chart showing changes in reflected light and its received light level when a defective area is irradiated, and FIG. 5B is a waveform diagram showing the output of the comparator when its output is discriminated. Is.

FIG. 6A is a conceptual diagram showing the relationship between the width and height of a defect,
FIG. 6B is a diagram showing the relationship between the amount Vx of decrease in the light receiving level and the inclination angle α of the defect.

FIG. 7 is a block diagram showing an embodiment of an optical disc defect inspection apparatus of the present invention.

FIG. 8A is a diagram showing a state in which an optical disc is disassembled into minute fan-shaped matrices, and FIG. 8B is a diagram showing one matrix portion thereof.

FIG. 9 is a flowchart (part 1) showing the operation of the present embodiment.

FIG. 10 is a flowchart (part 2) showing the operation of the present embodiment.

11A and 11E are time charts showing a defect occurrence state in a state where an optical disc is divided into matrices, and FIGS. 11B to 11D are time charts showing output changes at that time.

12A is a time chart showing a defect occurrence state in a state where an optical disc is divided into a matrix, and FIGS. 12B to 12D are time charts showing output changes at that time.

13A is a schematic diagram showing an optical system portion of a conventional optical disc defect inspection apparatus, and FIGS. 13B and 13C are graphs showing output changes at that time.

[Explanation of symbols]

1 Optical Disc 1e Protective Film 2 Addition Means 3 Discrimination Means 4 Defect Width Detection Means 5 Peak Value Detection Means 6 Defect Inclination Detection Means 7 Defect Height Detection Means 11 Rotation Drives 12 Rotary Encoders 13, 31 AND Circuits 14 Circumferential Direction Address Counters 15 Height Data Memory 16 Optical Pickup Section 17 Linear Actuator 18, 19, 20 Amplifier 21 Adder 22 Comparator 23 Peak Hold Circuit 24 Microcomputer 25 A / D Converter 26, 33 Latch Circuit 27 Linear Encoder 28 Up / Down Counter 29 PLL circuit 30 clock generator 32 W _D counter

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G11B 20/18 F 8940-5D 572 C 8940-5D F 8940-5D

Claims (12)

[Claims] 1. An optical disc is moved along the surface thereof, irradiated with light inclined at a predetermined angle from a direction perpendicular to the information surface of the optical disc, and respective reflected light and diffracted light reflected from the optical disc are received. By receiving the reflected light and the diffracted light, the received light signals are added, and the added received light signal is discriminated by a predetermined threshold value.
A method for inspecting an optical disc defect, which comprises detecting a defect occurring on an information surface of an optical disc based on a decrease in the level of received light. 2. An optical disk is rotationally driven at a constant rotational speed to generate a clock signal having a cycle inversely proportional to the traveling speed of the optical disk at the light beam irradiation position, and the discrimination output is obtained using the clock signal. 2. The optical disc defect inspection method according to claim 1, wherein the time is counted and the width of the defect is detected based on the count output. 3. An optical disk is rotationally driven at a rotational speed that is inversely proportional to a radius r from the center of rotation of the optical disk to an irradiation position of a light beam, a clock signal having a constant cycle is generated, and the discrimination output is counted using the clock signal. 2. The optical disc defect inspection method according to claim 1, wherein the defect width is detected based on the count output. 4. The inclination angle of the defect is detected based on the lowered level of the signal when the discriminating means detects a signal of a predetermined value or less. Optical disc defect inspection method according to the item. 5. An optical disk is rotationally driven at a constant rotational speed, irradiates light at a predetermined angle with respect to a direction perpendicular to the information surface of the optical disk, and receives reflected light and diffracted light reflected from the optical disk. By receiving light in a region, adding the received light signals of the reflected light and the diffracted light, and discriminating the added received light signal by a predetermined threshold,
Detecting a decrease in the received light level, when a signal below a predetermined value is detected by the discriminating means, the inclination angle of the defect is detected based on the decrease level of the signal, and the running speed of the optical disc at the light beam irradiation position is detected. Generating a clock signal having an inversely proportional period, detecting the width of the defect by counting the discrimination output using the clock signal, and detecting the height of the defect based on the count output and the inclination of the defect. An optical disc defect inspection method characterized by the above. 6. The optical disc is rotatably driven at a rotational speed that is inversely proportional to the radius from the center of rotation of the optical disc to the irradiation position of the light beam, and the optical disc is irradiated with light at a predetermined angle with respect to a direction perpendicular to the information surface of the optical disc. By receiving the reflected light and the diffracted light reflected by the respective light receiving regions, adding the received light signals of the reflected light and the diffracted light, and discriminating the added light receiving signal by a predetermined threshold value,
Detecting a decrease in the received light level, when a signal below a predetermined value is detected by the discriminating means, the inclination angle of the defect is detected based on the decrease level of the signal, and a clock signal of a constant cycle is generated, and the clock is generated. The defect width is detected by counting the time at which the discrimination output is obtained using a signal, and the defect height is detected based on the counting output and the inclination angle of the defect. . 7. An optical disk moving means for moving the optical disk along its surface, a light projecting section for irradiating light at a predetermined angle with respect to a direction perpendicular to the information surface of the optical disk, and reflected light reflected by the optical disk. And a light receiving unit that receives the diffracted light at each light receiving position, an adding unit that adds the respective light receiving signals obtained from the light receiving unit, and a light receiving signal that is added by the adding unit is discriminated by a predetermined threshold value. An optical disc defect inspection apparatus, comprising: a discriminating means for detecting a decrease in the received light level. 8. The optical disk moving means drives the optical disk to rotate at a constant rotational speed, and generates a clock signal for generating a clock signal having a cycle inversely proportional to the traveling speed of the optical disk at the irradiation position of the light beam. 8. An optical disk according to claim 7, further comprising: means for detecting the width of the defect by counting the output of the clock signal generating means based on the discrimination output of the discrimination means. Defect inspection equipment. 9. The optical disk moving means drives the optical disk while keeping the traveling speed of the optical disk constant at the irradiation position of the light beam, and the discriminating output of the discriminating means counts a clock signal having a constant cycle. 8. An optical disc defect inspection apparatus according to claim 7, further comprising defect width detection means for detecting a width of a defect on the information surface side of the optical disc. 10. A peak value detecting means for detecting a width of a decrease in the output of the adding means at a position where a defect occurs as a peak value, and a tilt angle of the defect based on the peak value detected by the peak value detecting means. 8. An optical disk defect inspection apparatus according to claim 7, further comprising defect inclination angle detection means for detecting. 11. An optical disk drive means for rotationally driving the optical disk at a constant rotational speed, a light projecting section for irradiating light at a predetermined angle with respect to a direction perpendicular to the information surface of the optical disk, and reflection reflected by the optical disk. A light-receiving unit that receives light and diffracted light at respective light-receiving positions, an adding unit that adds the respective light-receiving signals obtained from the light-receiving unit, and a light-receiving signal that is added by the adding unit are discriminated by a predetermined threshold value. Discriminating means for detecting a decrease in the light receiving level by means of: a clock signal generating means for generating a clock signal having a cycle inversely proportional to the traveling speed of the optical disc at the irradiation position of the light beam; and the clock based on the discriminating output of the discriminating means. Defect width detection means for detecting the width of the defect on the information surface side of the optical disc by counting the output of the signal generation means; Peak value detecting means for detecting the width of decrease in the output of the adding means at a certain position as a peak value, and defect inclination angle detection for detecting the inclination angle of the defect based on the peak value detected by the peak value detecting means. An optical disk defect inspection device comprising: a defect width detecting unit and a defect height detecting unit that detects a defect height based on outputs from the defect inclination angle detecting unit. 12. A light projecting portion for irradiating light at a predetermined angle with respect to a direction perpendicular to an information surface of the optical disk, and a surface of the optical disk so that the traveling speed is constant at a light projecting position of the light projecting portion. An optical disc moving unit that moves along the optical disc; a light receiving unit that receives reflected light and diffracted light reflected by the optical disc at respective light receiving positions; an adding unit that adds light receiving signals obtained from the light receiving unit; and the adding unit. Discriminating means for detecting a decrease in the received light signal level by discriminating the added light reception by a predetermined threshold, and counting the clocks of a constant cycle based on the discrimination output of the discriminating means Defect width detection means for detecting the width of the defect; peak value detection means for detecting the width of the decrease in the output of the addition means at the position where the defect occurs as a peak value; Defect inclination angle detection means for detecting the inclination angle of the defect based on the peak value detected by the value detection means, and defect for detecting the height of the defect based on the outputs of the defect width detection means and the defect inclination angle detection means. An optical disc defect inspection apparatus comprising: a height detection unit.