JP3881530B2 - Surface defect inspection equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  This inventionThe tableMore specifically, in the surface defect inspection apparatus for a surface plate such as a magnetic disk or a glass substrate (glass substrate) thereof, it is possible to accurately detect the size of the irregularities on the surface of the surface plate. The detection of the size and depth or the size and height of surface irregularities can be accurately detected.SurfaceThe present invention relates to a defect inspection apparatus.
[0002]
[Prior art]
Hard magnetic disks used for computer system recording media are at the stage of a substrate disk (substrate) as a material or a magnetic disk coated with a magnetic film (for convenience, these are collectively referred to as a magnetic disk or simply a disk). Each defect on the surface and its size are inspected.
In recent years, the size of a disk is 3.3 inches or less, and its recording density has been dramatically increased by the adoption of a GMR head. In this type of disk, a glass disk having a smaller thermal expansion coefficient is used from an aluminum substrate, and its thickness is also as thin as about 0.6 mm to 0.8 mm.
[0003]
FIG. 5 shows a configuration of a main part of a surface defect inspection apparatus 10 for a conventional magnetic disk.
A surface defect inspection apparatus 10 shown in FIG. 5A includes a rotation mechanism 2, a detection optical system 3, and a surface defect detection processing unit 4. The disk 1 to be inspected is mounted on the spindle 21 of the rotation mechanism 2 and is rotated by driving a motor (M) 22. On the other hand, the detection optical system 3 has a laser beam L from the laser light source 311 of the projection system 31._TIs focused by a focusing lens 312 and a spot S is formed on the surface of the disk 1._PAnd the surface of the disk 1 is irradiated.
For example, the spot S is generated by moving the disk 1 in the X-axis direction._PMoves in the radial direction (R direction) of the disk 1, whereby the surface of the disk 1 is scanned in a spiral shape. In this case, in order to make the scanning time as short as possible, the spot S_PIs the short diameter φ as shown in FIG.₁And major axis φ₂It has an elliptical shape with a major axis φ₂Is set at a right angle to the scanning direction to increase the scanning width.
[0004]
The defect F existing on the surface is the spot S_PScatter the light. The reflected light S_RIs condensed by the condenser lens 321 of the light receiving system 32 and received by a light receiver 322 made of a photoelectric conversion element, for example, an avalanche photodiode (APD) or a photomultiplier tube (PMT). The output signal of the light receiver 322 is input to the signal processing circuit 41 of the surface defect detection processing unit 4. Here, the defect F is detected, and the size of the defect is classified or calculated from the amplitude of the output signal. In order to detect defects and classify or calculate the size, the signal processing circuit 41 is a circuit that detects defects by so-called sampling, and an amplifier that amplifies an output signal from the light receiver 322 and a rotary encoder 23. A sampling circuit that samples the peak value of the output signal for the defect that exceeds the noise among the output signals amplified by receiving the pulse to detect the peak value of the defect, and further converts the sampled peak value to a digital value It comprises an A / D converter, a position data generating circuit that receives pulses from the rotary encoder 23 and generates position data on the disk.
[0005]
The data of the size of each defect and the data on the position on the disk are A / D converted inside the signal processing circuit 41 and input to the data processing device 44 including the MPU 42 and the memory 43. Here, the number of defects by size is counted, and the result is printed out by the printer (PR) 45 together with the position of the defect on the disk 1. Alternatively, the size is displayed on the display (CRT) 46 together with the position on the disc, and the count value is also displayed separately.
The rotary encoder 23 is provided adjacent to or engaged with the rotation shaft of the motor 22, detects the reference rotation position and the rotation amount of the disk, and sends each pulse signal to the signal processing circuit 41. To do.
[0006]
In order to satisfactorily detect the size of the concave defect and the convex defect, the surface defect inspection apparatus 10 described above is configured so that the laser beam L of the light projecting system 31_TProjection angle θ_TOr the light receiving angle θ of the light receiving system 32_RControl of factors related to detection sensitivity, such as the voltage V applied to the light receiver 322 (APD), the gain of the amplifier built in the signal processing circuit 41, the threshold voltage E for noise removal, and the laser output of the laser light source 311 Each is set optimally via the panel 47. Note that sensitivity adjustment can be performed by using an actual disk with a sample defect such as a dish-shaped defect, a pit defect, or a scratch defect with a known size, or an actual disk with a protrusion of a specific height as a sample. Has been done.
As an invention of this type, there is an application of Japanese Patent Laid-Open No. 10-325713 “Surface defect inspection method and inspection apparatus” by the applicant. This is because a simulated defect array whose size is gradually increased or decreased by performing a defect inspection using a radial sensitivity calibration disk in which the sizes of the projections or recesses of each simulated defect array differ in stages. Is displayed as a test result in a radial pattern, and the detection sensitivity is adjusted according to the test result.
[0007]
[Problems to be solved by the invention]
However, in the conventional defect detection system described above, a concave defect or a convex defect (including foreign matter) is detected by comparing the level of reflected light or scattered light detected by the light receiver with the reference level. Therefore, the detection of the size of the concavo-convex defect to be detected is substituted with the light receiving level, and it is not accurate. In particular, in a concave defect or a convex defect, the height and depth affect the light reception level, and the detection accuracy of the size as an area developed on a plane is low.
Recently, there has been a demand for measurement of uneven shapes and improvement of classification accuracy. However, the above-described technique has a problem that classification cannot be performed with high accuracy.
[0008]
  In order to solve this type of problem, the light receiver 322 is provided as an array sensor composed of APD multi-elements, and a staggered fringe pattern is provided in front of the light-receiving element 322 so as to reduce the concave portion from the difference in the amount of light received by adjacent light-receiving elements. This applicant has applied for a technique for detecting defects and convex defects as Japanese Patent Application No. 11-358769 “Defect Detection Optical System and Surface Defect Inspection Device”.
  However, this has a drawback that a staggered stripe pattern is required and a number of circuits for detecting the difference between adjacent elements are required.
  The object of the present invention is to solve such problems of the prior art, and can detect the size of the irregularities on the surface of the face plate with high accuracy.SurfaceIt is to provide a defect inspection apparatus.
  Another object of the present invention is to provide a surface defect inspection apparatus that can accurately detect the size and depth of a concavo-convex defect on the surface of a face plate or the size and height thereof and can easily classify defects.
[0009]
[Means for Solving the Problems]
  This invention for achieving such an objectTableThe feature of the surface defect inspection apparatus is that the surface of the face plate is scanned with a light beam, the light reflected from the surface by the light beam is received by a light receiver, and this light receiver generates a signal for detecting a defect.Surface defect inspection equipment, A light projection system that irradiates a light beam having a width in a direction perpendicular to the main scanning direction to relatively scan the face plate and n light receivers (where n is an integer of 2 or more). ) And a light receiving system in which an image at the scanning position of the face plate is formed on n light receiving elements and the image forming along the direction perpendicular to the main scanning direction is the arrangement direction. , The width of image formation in the main scanning direction is the width of the light receiving element or smaller than this,Obtained from the sloped part ofReflected lightany one of nWhen the light receiving element receives the image, the image is perpendicular to the arrangement direction.OneShake in the width direction of the light receiving element, and the amount of light received decreases or no light is received.OneThe light receiving elementWhich generates a peak signal,
  A peak signal when a concave defect or a convex defect is scanned is obtained from the light receiver corresponding to each of the n light receiving elements, and the concave defect or the defect signal is determined based on the distance between the two front and rear peak signals in each light receiving element. A concave defect or a convex defect is detected by detecting two peak signals corresponding to the inclined portions of the front and rear side surfaces of the convex defect.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
As in the above configuration, there is provided a light receiving system having n light receiving elements arranged so that the image formation along the direction perpendicular to the main scanning direction is the light receiving element arrangement direction, and The width of image formation is the width of the light receiving element or smaller than this, and the reflected light of the concave or convex defect is swung in the width direction of the light receiving element, so that the reflected light of the concave or convex defect is When the wave is swung to the left or right at the side inclined portion, the amount of light received by the light receiving element is reduced, or the light receiving element stops receiving light, and a detection signal lower than when there is no defect can be obtained.
The concave defect or the convex defect has two pair of right and left side inclined portions in the main scanning direction, and therefore two detection signals can be obtained for one defect. Therefore, the size of the defect at the position can be easily detected from the distance relationship between the two detection signals. In particular, when n light receiving elements are arranged in the radius R direction, a plurality of light receiving elements arranged according to the size of the defect in the radial direction can simultaneously detect the defect. Therefore, the area corresponding to the size of the defect can be easily calculated.
[0011]
  Further, it is possible to easily determine the continuity of the defect from the relationship between the defect detection coordinates to which each of the n light receiving elements determined in accordance with the scanning is assigned and the detection signal of each light receiving element. The area can also be calculated for a defect in a slightly deformed state among the defect and the convex defect. Further, by taking the average value of the levels of the two detection signals, the depth of the concave defect or the height of the convex defect can be detected with high accuracy.
  As a result, the size of the irregularities on the surface of the face plate can be detected with high accuracy, and the size and depth or the size and height of the irregularities on the surface of the face plate can be accurately detected.OrA surface defect inspection apparatus with easy defect classification can be realized.
[0012]
【Example】
In FIG. 1, 100 is a surface defect inspection apparatus, and 50 is the detection optical system. Reference numeral 51 denotes a light projection system of the detection optical system 50, and the light projection system 51 is a laser beam L from the laser light source 511._TIs received by the beam expander 512, and the laser beam is expanded in one direction (R direction) perpendicular to the paper surface in the drawing to shift the focal position toward the front. The expanded beam passes through the cylindrical lens 513 and the focussing lens 514, and is shifted toward the beam waist in the radius R direction by an offset Δd (see FIG. 2A) so that the focal position is shifted to the front, and the surface of the disk 1 is moved. Focus. As a result, the beam spot S becomes elliptical._p(See Fig. 2 (b))
[0013]
  In FIG. 1, in a direction parallel to the paper surface of the drawing (disk rotation direction, that is, the θ direction), the light beam that has passed through the cylindrical lens 513 passes through the focussing lens 514 as shown, and the surface of the disk 1.PlaneIt is focused on the inspection point S in the form of dots (see the ♦ points in FIG. 2B). The projection angle is about 30 ° with respect to the normal on the disk 1 in the θ direction, as shown in FIG. The inspection point S becomes light having a constant width W (for example, about 150 μm to about 200 μm) in the direction perpendicular to the paper surface (R direction), and this width W indicates the arrangement range of the light receiving elements on the imaging surface. It is the length to cover. At this point, the beam spot S in FIG._pIs different.
  The light receiving system 52 has an objective lens 521, which receives regular reflection light from the inspection point S of the disk 1 and converts it into parallel light and guides it to the imaging lens 522. The imaging lens 522 forms an image of the inspection point S on the light receiving surface of the APD array sensor 523. In the APD array sensor 523, as shown in FIG. 3, n (for example, 23) light receiving elements are arranged along the image of the disk 1 in the radius R direction (direction perpendicular to the paper surface of FIG. 1). It is. On the APD array sensor 523, an image of the inspection point S is formed so that the above-described width W (about 150 μm to about 200 μm) covers the range of the light receiving element array length of about 120 μm. At this time, the width of each light receiving element in the arrangement direction of each element is, for example, 0.5 mm on the light receiving element and about 5 μm on the surface of the disk 1.
[0014]
FIG. 2A is a development explanatory view of a light projecting / receiving system for explaining a direction parallel to the paper surface (θ direction) and one direction perpendicular to the paper surface (R direction), and the upper side is the θ direction parallel to the paper surface. Yes, the lower side is the R direction perpendicular to the paper surface.
As shown in FIG. 2A, in the θ direction, the laser beam L from the laser light source 511 is obtained._TPasses through the beam expander 512 and the focussing lens 514, and is focused as a spot (see the point ♦ in FIG. 2B) at the inspection point S with the focussing lens 514 focusing on the surface of the disk 1. The specularly reflected light from the inspection point S is received by each light receiving element of the APD array sensor 523 through the objective lens 521 and the imaging lens 522.
On the other hand, as shown in the lower side of FIG. 2A, in the radius R direction, the laser beam L from the laser light source 511 is obtained._TPasses through the beam expander 512, the focussing lens 514, and is focused by the focussing lens 514 to the inspection point S with the width W in an elliptical shape with the position just before the offset Δd from the surface of the disk 1 as a focal point (FIG. 2B). reference). The specularly reflected light from the inspection point S passes through the objective lens 521 and the imaging lens 522, and is then inspected along the arrangement direction of the light receiving elements 523a, 523b, 523c, ..., 523n of the APD array sensor 523 by the imaging lens 522. The image of S is received.
[0015]
As shown in FIG. 1, detection signals (output signals) obtained from the respective light receiving elements 523a to 523n of n APD array sensors 523 arranged in the R direction are signals of the surface defect detection processing unit 4 in FIG. The data is input to the defect detection unit 400 corresponding to the processing circuit 41. Here, data of the defect F and its depth or height are generated. Those defect data are input to a data processing device 410 including an MPU 411 and a memory 412. Then, in the data processing device 410, the area of the defect F is calculated, and the size is classified according to the calculated area together with the depth or height. These results are printed out by the printer (PR) 45 together with the position of the defect in the disk 1. They are displayed on the display (CRT) 413 together with the position on the disc, and the count value is also displayed separately.
[0016]
Here, characteristics of detection signals output from the n light receiving elements 523a to 523n will be described. Each of the light receiving elements 523a to 523n has an image formed in the inspection area S in the R direction inside the light receiving area of each element in the central direction so that it does not protrude from the light receiving area as shown in FIG. Is imaged. That is, the width of the image formed in the inspection area S is the width D of each light receiving element or smaller. Therefore, when no defect is detected, such a light receiving state is established, and the detection signal is at the maximum level. When a defect is detected, the image formed in the inspection area S swings to the right or left in FIG. When shaken, the level of the detection signal of each light receiving element decreases according to the shake state. Further, when the image formed in the inspection area S deviates from the light receiving area, the level of the detection signal becomes substantially zero.
[0017]
Next, it will be described with reference to FIG. 4 that the image of the specularly reflected light of the concave defect and the convex defect fluctuates left and right when the defect is detected.
Laser beam L_TIf a recess defect is encountered while scanning the disk 1, the laser beam L_TIf the angle of the inclined portion when entering the recess defect is δ, as shown in FIG. 4A, the regularly reflected light rotates clockwise by 2δ in the θ direction. As a result, the specularly reflected light from the inspection point S is shifted by 2δ in the θ direction. Accordingly, the image formed by the light receiving element that receives specularly reflected light corresponding to a certain recess defect in FIG. 3 moves from the center position to the right side. Thereafter, the bottom surface of the defect is scanned, and the image formed by the light receiving element returns to the center position. And conversely, the laser beam L from the recess defect_TWhen 出 る comes out, the angle δ of the inclined portion is reversed, moves from the central position to the left side, and then returns to the central position.
On the other hand, in the convex defect, the left and right inclined parts appear opposite to the above, and in contrast to the concave defect, the imaged image of the light receiving element first moves to the left, returns to the center, and then moves to the right. Return to the center.
Furthermore, in the case of a deep hole or a high protrusion, the amount that deviates from the light receiving area of the light receiving element increases when it swings to the left or right, and when the depth or height increases, it returns completely after being completely removed. .
As a result, a detection signal as shown in FIG. 4B is obtained according to the depth of the recess defect or the protrusion defect, and when the hole is a deep hole or a high protrusion, the level is greatly reduced.
[0018]
Now, referring back to FIG. 1, the detection signals of the n light receiving elements 523a, 523b,... 523n are inverted and amplified by the inverting amplifiers 401a, 401b,. A positive peak signal is input to the peak detection sample hold circuits 402a, 402b,. Here, the peaks of the detection signals of the two peaks (a signal obtained by inverting the signal of FIG. 4B) are detected for each light receiving element (each detection channel). The detected peak values are A / D converted by the A / D conversion circuits (A / D) 403a, 403b,... 403n, and the respective converted values are stored in the defect memory 404.
The peak detection / sample hold circuits 402a to 402n receive the clock CLK from the clock generation circuit 406, and hold the peak value as a sample value accordingly.
The outputs of the inverting amplifiers 401 a to 401 n are input to the defect detection circuit 405. The defect detection circuit 405 has a hysteresis comparator, and compares the output of the inverting amplifiers 401a to 401n with the predetermined value Vth under the OR condition, and when the output level of any of the inverting amplifiers rises above the predetermined value. When the defect detection signal DET is generated and the output level of the amplifier falls below a certain value (corresponding to the vicinity of the peak value), the defect detection signal DET stops. The trailing edge (rear edge) when DET stops is sent to the defective memory 404 as a write control signal WR. Further, the write control signal WR is delayed a little and input as a reset signal RS to each of the peak detection / sample hold circuits 402a to 402n, and the values up to that time are reset.
[0019]
As a result, a peak value in a period from when the defect detection signal DET is generated until the defect detection signal DET ends is transmitted from each A / D 403a to 403n to the defect memory 404 and stored as defect data. The level at this time represents the depth of the concave defect, and represents the height of the convex defect. Further, the distance between the peaks corresponds to the size of the defect.
Such defect data is stored in the updated address of the defect memory 404 together with the position data of R and θ. This address is updated each time data is written. The position coordinate data of R and θ is generated by the scanning position coordinate generation circuit 407.
The write control signal WR is generated from the peak detection / sample hold circuit 402 (as a representative of the peak detection / sample hold circuits 402a to 402n) at the timing of peak detection, not the fall of the defect detection signal DET. Also good.
[0020]
The scanning position coordinate generation circuit 407 receives an index signal indicating the rotation reference position of the disk 1 and an angle signal θ corresponding to the rotation from the rotary encoder 23 (see the one shown in FIG. 5), and further receives a current signal from the data processing device 410. In response to the coordinate position R in the radius R direction, the position coordinate data of R and θ are generated and sent to the defect memory 404 as position data.
As a result, the defect memory 404 indicates the level value of the detection signal corresponding to the depth or height of the defect and the position where the two detection signals are generated for one concave defect or convex defect each time the defect is detected. To remember.
The clock generation circuit 406 sends a clock CLK to the A / Ds 403a to 403n, the peak detection / sample hold circuits 402a to 402n, the data processing device 410, and the like.
[0021]
Next, defect area calculation and size classification of the data processing apparatus 410 will be described.
In FIG. 1, the data processing apparatus 410 includes an MPU 411, a memory 412, a CRT display 413, an interface 414, and the like, which are connected to each other via a bus 415. When the spiral scanning of the disk 1 is completed, the defect data obtained from the defect memory 404 by the MPU 411 is read and stored in the memory 412 via the interface 414 and the bus 415.
The memory 412 stores a detection signal distance calculation program 412a, a continuity determination processing program 412b, a defect area calculation program 412c, a defect size classification program 412d, a height / depth classification program 412e, and the like. Yes. In addition, various data files for classification are stored in an external storage device 416 such as an HDD (hard disk device) connected via the interface 414.
[0022]
The detection signal distance calculation program 412a is executed by the MPU 411, and by executing this, the MPU 411 reads the defect data in the defect memory 404 into the memory 412, and calculates the distance L from the detection coordinates of two adjacent peak values. When the distance L is within the reference value S, it is determined that the data is for one defect. Further, the center coordinate is further calculated from the coordinate values detected for the two peak values, and the calculated distance L (corresponding to the length of the defect) and the center coordinate value are sequentially stored. Then, similar processing is performed on adjacent peak values for the next defect data, and when this processing is completed, the continuity determination processing program 412b is called. When the reference value S is exceeded, one of them is stored as defect data with zero length and the coordinate value as the center coordinate.
[0023]
The continuity determination processing program 412b is executed by the MPU 411. By executing this, the MPU 411 calculates the center coordinates and the length (distance L) as continuity determination processing when the distance L is calculated for all defect data. It is determined whether or not the distance L overlaps with the width of 5 μm in the vertical and horizontal directions based on the detection width of one light receiving element (in this embodiment, about 5 μm), and the continuity of defects is determined between adjacent defect data. . Then, consecutive data are grouped and stored as a single defect data in the order of defects sequentially detected from the innermost or outermost periphery of the disk, and the defect area calculation program 412c is called.
Here, in the defect detection, one or a plurality of detections of the light receiving elements arranged in the R direction according to the size of the defect occur at the same θ direction coordinates. This is possible by determining that the detected coordinates in the direction are within the range of the distance L of the defect and the adjacent coordinates in the R direction are continuous. Therefore, the continuity may be determined by tracing a defect having the same detection coordinate in the θ direction with the width of L along the R direction. In this way, determination of continuity becomes easier.
[0024]
By the way, since the defect is detected corresponding to n light receiving elements here, the detection coordinate in the R direction of the defect is the coordinate in the R direction of the defect detection position stored in the defect detection memory 404, and n It can be grasped in a subdivided manner corresponding to the position of each light receiving element. Therefore, the detection accuracy of the n light receiving elements is added as detection coordinates in the R direction to obtain n times the positional accuracy. Thereby, the resolution of defect detection in the R direction can be improved to correspond to each light receiving element. When a plurality of adjacent light receiving elements among n in the R direction detect one defect, the position of the light receiving element at the center of the plurality of light receiving elements is set as a detection coordinate in the R direction of the defect.
[0025]
The defect area calculation program 412c is executed by the MPU 411, and by executing this, the MPU 411 calculates the area of one grouped defect as an area calculation process. Note that the defect of one peak that does not become two detection signals is an isolated defect with an area of 5 μm, and the area that is not continuous in the R direction is calculated by the length L × 5 μm. Then, the defect size classification program 412d is called.
The defect size classification program 412d is executed by the MPU 411, and the MPU 411 executes the defect size classification program 412d according to the classification criteria as the size classification determination process for the area calculated as described above. Then, the classification result is stored in correspondence with the defect number by classifying into five minimum levels. Thereafter, the height / depth classification program 412e is called.
[0026]
The height / depth classification program 412e is executed by the MPU 411, and the MPU 411 executes the defect data value of the defect memory 404 stored in the memory 412 in the order of the defect number (the peak value of the detection signal in one grouped defect). (Average value) is calculated, and the average value is classified into large, medium, and small as height or depth, and stored in the memory 412 corresponding to the defect number. When there is no defect data for one defect, no average value is taken. Most of the defect data is defect data having a peak value of two or more for one concave defect and convex defect. Therefore, the depth and height of each defect can be calculated by average values. Their detection accuracy is improved.
Note that the above processing is a simple one in which each program is executed sequentially, and therefore description thereof in the flowchart is omitted.
[0027]
As described above, in the embodiment, an example of the laser beam is given as the irradiation light to be applied to the inspection surface of the disk. However, when the laser beam is used, it is particularly preferable to use the S-polarized laser beam. However, the present invention is not limited to this laser beam, and it is needless to say that the irradiation light may be white light.
Further, in the embodiment, the description has been made mainly on the disk surface defect inspection apparatus, but the present invention is not limited to the disk, but of course can be applied to the inspection of the LCD substrate and the like. Furthermore, in the embodiment, the scanning in the Rθ direction has been described, but the scanning may be XY two-dimensional scanning.
In the embodiment, the concave defect and the convex defect are detected without distinction, but these may be detected separately. In this case, since the concave and convex defects are reversed in the left and right shake order with respect to the light receiving element, for example, the light receiving element of the embodiment is divided into two at the center in the width direction, and two columns, This is possible by determining whether the defect is a concave defect or a convex defect depending on whether any of the divided light receiving elements that have been arranged in the R direction has previously generated a light reception signal.
[0028]
【The invention's effect】
  As described above, according to the present invention, a light receiving system having n light receiving elements arranged and having an image formed along a direction perpendicular to the main scanning direction as the light receiving element arrangement direction is provided. And, the width of the image formation in the scanning direction is the width of the light receiving element or smaller than this, and the reflected light of the concave or convex defect is shaken in the width direction of the light receiving element to reduce the light receiving region, When the reflected light of the concave defect or convex defect fluctuates to the left or right at the side inclined portion of the defect, the amount of received light is reduced, and a detection signal that is lower than when there is no defect can be obtained.
  Therefore, the size of the defect at the position can be easily detected from the distance relationship between the two detection signals. Further, the depth or height of the defect can be easily detected from the levels of the two detection signals.
  As a result, the size of the irregularities on the surface of the face plate can be detected with high accuracy, and the size and depth or the size and height of the irregularities on the surface of the face plate can be accurately detected.OrA surface defect inspection apparatus with easy defect classification can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram of an embodiment of a surface defect inspection apparatus to which the present invention is applied.
FIG. 2 is a development explanatory view of a light projecting / receiving system in a direction in a detection optical system in a direction parallel to the paper surface (θ direction) in the drawing and one direction (R direction) in the drawing perpendicular to the paper surface.
FIG. 3 is an explanatory diagram of a relationship between an image formed on a light receiving surface in an inspection region and an APD array sensor.
FIG. 4 is an explanatory diagram of generation of specularly reflected light of a recess defect and a detected waveform thereof;
FIG. 5 is an explanatory diagram of a configuration of a main part of a conventional magnetic disk surface defect inspection apparatus.
[Explanation of symbols]
1 ... disc,
2 ... rotating mechanism, 10 ... surface defect inspection device,
21 ... Spindle, 22 ... Motor,
3, 50 ... detection optical system,
31, 51 ... Projection system, 311, 511 ... Laser light source,
512 ... Beam expander,
513 ... Cylindrical lens,
514: Focusing lens,
521 ... Objective lens, 522 ... Imaging lens,
523 ... APD array sensor,
32, 52 ... light receiving system, 400 ... defect detection unit,
401a, 401b, 401n... Inverting amplifier,
402a, 402b, 402n ... peak detection sample hold circuit,
403a, 403b, 403n ... A / D conversion circuit (A / D),
404 ... defect memory, 405 ... defect detection circuit,
406 ... Clock generation circuit, 407 ... Scanning position coordinate generation circuit,
410: Data processing device, 42, 411: MPU, 45: Printer (PR),
43, 412 ... memory,
412a ... Detection signal distance calculation program,
412b ... continuity determination processing program,
412c ... Defect area calculation program,
412d ... defect size classification program,
412e ... height / depth classification program,
413 ... CRT display,
414 ... interface, 415 ... bus,
416 ... External storage device, 100 ... Surface defect inspection device,
L_T... Laser beam, S_P... Beam spot, φ₁... the minor axis of the spot,
φ₂... spot major axis, F ... defect.

Claims (4)

In the surface defect inspection apparatus in which the surface of the face plate is scanned with a light beam, the light reflected from the surface by the light beam is received by a light receiver, and the light receiver generates a signal for defect detection.
A light projecting system that irradiates the light beam having a width in a direction perpendicular to the main scanning direction to relatively scan the face plate, and n light receivers arranged (where n is an integer of 2 or more) And a light receiving system in which an image at the scanning position of the face plate is formed on the n light receiving elements and the image formation along the perpendicular direction is the array direction. When the reflected light obtained from the inclined portion of the concave defect or the convex defect is received by any one of the n light receiving elements, the width of the imaging is less than the width of the light receiving element. The imaging is shaken in the width direction of the one light receiving element which is perpendicular to the arrangement direction, and the light receiving amount is reduced or no light is received, so that the one light receiving element generates a peak signal. And
The peak signal when the concave or convex defect is scanned is obtained from the light receiver corresponding to each of the n light receiving elements, and the distance between the two front and rear peak signals in each light receiving element. A surface defect inspection apparatus for detecting the concave defect or the convex defect by detecting two peak signals corresponding to the inclined portions of the front and rear side surfaces of the concave defect or the convex defect based on the above . The surface defect inspection apparatus according to claim 1, wherein the face plate is a disk. Further comprising a detection circuit for generating a detection signal by amplifying the signal of the peak, the disc is a substrate, wherein the scanning is helical scan, the imaging is an oblong The surface defect inspection apparatus according to claim 2, wherein the major axis corresponds to the arrangement direction of the light receiving elements. Further, the position coordinates generation circuit for generating information on the scanning position of said disk, and A / D conversion circuit for converting the peak value of the detection signal into a digital value, the digital of the peak value from the A / D converter circuit receiving the value and the distance to obtain the distance between two of the detection signal before and after the information of the scan position from the position coordinate generating circuit receives the information of the scanning position of one when in less than a predetermined value The surface defect inspection apparatus according to claim 3, which is detected as a defect.

Images