Photosensor device and disk inspection apparatus using it

A photosensor device is provided which includes a light-applying fiber to apply an inspection light to a subject to be inspected; a light-receiving fiber to receive a reflected light from the subject to be inspected; a laser beam source to emit the inspection light to the light-applying fiber; and a photosensor to receive the reflected light via the light-receiving fiber. A disk inspection apparatus for inspecting surface conditions of a disk is also provided which includes a turning table for rotating the disk; a photosensor body disposed opposite to the surface of the disk; and a transfer mechanism for reciprocally transferring the photosensor body in a direction perpendicular to a rotating direction of the disk along the surface of the disk; wherein the photosensor device is utilized as the photosensor body.

FIELD OF THE INVENTION

The present invention relates to a photosensor device which detects fine scratches, distortion or the like on the surface of a subject to be inspected, and a disk inspection apparatus using it to inspect defects of disks.

BACKGROUND OF THE INVENTION

In general, when the presence or absence of scratches, pinholes, distortion or the like formed on the surface of a subject to be inspected is inspected with a photosensor device of such a type, a casing of this device is disposed opposite to the surface of the subject to be inspected at a predetermined distance, inspection light is applied to the subject to be inspected from a light-applying fiber installed in this casing, and reflected light from the subject to be inspected is received by a photosensor through a light-receiving fiber.

The reflected light received by the photosensor is photoelectrically converted and output to an arithmetic section, and it is judged whether or not the voltage value (received light intensity) is within a certain set value. At that time, when scratches, pinholes, distortion or the like exist on the surface of the subject to be inspected, the reflected light is scattered or deflected, whereby the received light intensity detected by the photosensor decreases. As a result, when the received light intensity (voltage value) detected by the photosensor is less than a certain set level, an inspector may judge that scratches or the like exist on the surface of the subject to be inspected.

Incidentally, in many cases, the light-applying fiber installed in the casing is extended from this casing and connected to a light source device prepared at the outside, and inspection light emitted from a light source such as a semiconductor laser installed in the light source device is applied to the subject to be inspected via the light-applying fiber.

When the distance between the photosensor and the light source device is relatively long, it is demanded to sufficiently guarantee the strength and durability, whereby the cost becomes high. Further, the optical fiber connecting them has a flexibility and is thus likely to tremble, and when the optical fiber trembles, noise is likely to be made and properties of the inspection light tend to change, such being inconvenient.

Further, a connector portion which connects the optical fiber and the light source device is likely to be overloaded, and therefore it is also demanded to sufficiently guarantee the durability of this connector portion.

On the other hand, in general, optical disks such as CD (compact disk) are prepared by forming a recording film by coating on the surface of a polycarbonate resin substrate, and further providing a reflecting film on its surface. If defects such as scratches exist on the reflecting film or the like, recording properties will be remarkably impaired. Accordingly, various inspection devices to detect the defects have been proposed.

For example, JP-A-2000-171405 discloses a disk inspection apparatus in which a laser beam is irradiated on a rotating magnetic recording disk, and reflected light is received by a CCD array, and luminance data of each received pixel is compared with a preliminarily set luminance threshold to judge the presence or absence of defects on the disk surface.

However, in the disk inspection apparatus disclosed in the above publication, an expensive CCD array is used as an element to receive the reflected light from the disk, and further a means for image processing by each pixel the results obtained from the light received by the CCD array, whereby the structure is complicated and the unit cost of product is high. Accordingly, provision of the disk inspection apparatus of this type in a plural number in production steps leads to rise of the cost for equipment and is therefore unlikely to be realized.

As a result, since the disk inspection apparatus is used for inspection of finished disks only, even if defects are formed during the production steps, the defects will not be found until completion of production, whereby the yield of products is low, such being problematic.

SUMMARY OF THE INVENTION

Accordingly, it is the first object of the present invention to provide at a low cost a photosensor device excellent in the durability without changing the properties of the inspection light. Further, the second object of the present invention in to provide a disk inspection apparatus by which the unit cost of apparatus is low by using the above photosensor device; the cost of equipment is not so much increased even if the photosensor device is provided in a plural number in the production steps; and by providing the photosensor device in a plural number in the production steps, defects formed during the production can be instantly defected, whereby the yield of products can be improved.

In order to accomplish the above objects, the present invention provides a photosensor device, which comprises a light-applying fiber to apply an inspection light to a subject to be inspected; a light-receiving fiber to receive a reflected light from the subject to be inspected; a laser beam source to emit the inspection light to the light-applying fiber; a photosensor to receive the reflected light via the light-receiving fiber; and a casing enclosing the light-applying fiber, the light-receiving fiber, the laser beam source and the photosensor.

According to the photosensor device of the present invention, since the light-applying fiber, light-receiving fiber, laser beam source and photosensor are enclosed in one casing, connection with external units with a fiber cable is no longer required, and the durability and reliability can be improved.

In the photosensor device of the present invention, it is preferred to prepare a sensor unit as one channel which comprises the light-applying fiber, the light-receiving fiber which forms a pair with the light-applying fiber, the laser beam source connected to the light-applying fiber, and the photosensor connected to the light-receiving fiber; and dispose such sensor units as multi-channels in the casing to produce a fiber array. By such a structure, it is possible to inspect a wide inspection area in a short period of time.

The present invention also provides a disk inspection apparatus for irradiating an inspection light on a surface of a rotating disk and inspecting surface conditions of the disk based on a reflected light, which comprises a turning table for rotating the disk fitted thereon; a photosensor body disposed opposite to the surface of the disk; and a transfer means for reciprocally transferring the photosensor body in a direction perpendicular to a rotating direction of the disk along the surface of the disk; wherein the photosensor body comprises a fiber array constructed by arranging sensor units as multi-channels, each of the sensor units comprising as one unit, a light-applying fiber, a light-receiving fiber which forms a pair with the light-applying fiber, a laser beam source connected to the light-applying fiber, and a photosensor connected to the light-receiving fiber.

According to the disk inspection apparatus of the present invention, when a disk is fitted in the turning table and rotated, the photosensor body disposed opposite to the surface of the disk is transferred by a transfer means in a direction perpendicular to a rotating direction of the disk, and at this time, the inspection light is irradiated onto the surface of the disk from the light-applying fiber of fiber bundles which constitute the fiber array provided in the photosensor body, the reflected light is received by the photosensor via the light-receiving fiber of the fiber bundles, and the presence or absence of defects on the disk surface is detected based on the quantity of the reflected light received by the photosensor. And, the fiber array is composed of plural fiber bundles, and the inspection of defects on the disk surface is made while transferring the photosensor body in a direction substantially perpendicular to the rotating direction of the disk, whereby the entire surface of the disk can be inspected without arranging the fiber bundled densely.

In the disk inspection apparatus of the present invention, it is preferred to arrange the fiber arrays in plural lines in such a state that the phases of adjacent fiber arrays are shifted. By this structure, the fiber bundles can be arranged as dense as possible along the direction perpendicular to the direction for inspection.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 7show the first embodiment of the photosensor device of the present invention.FIG. 1is a plane view of the photosensor device.FIG. 2is a sectional view along line II—II inFIG. 1.FIG. 3is a bottom view of the photosensor device.FIG. 4is a sectional view along line IV—IV inFIG. 1.FIG. 5is a perspective view of the photosensor device.FIG. 6is a schematic side view of the photosensor device.FIG. 7is a circuit diagram of the photosensor device.

In these drawings, numeral100denotes a photosensor device. A front end portion for inspection102aextends from the center of the upper face of a casing102of the photosensor device100. At the front end portion for inspection102a,two lines of fiber arrays103,104are arranged. In this embodiment, the fiber arrays103,104are constituted by8channels of fiber bundles103a,104a,respectively. The fiber bundles103a,104ain respective lines are arranged with a predetermined pitch P, and the fiber bundles103a,104aadjacent to each other arranged in such a state that the phase of either one is shifted by a half pitch to another one.

Each of the fiber bundles103a,104ais constructed by bundling a light-applying fiber107and a light-receiving fiber108. An objective optical system109is provided at the front end of each of the fiber bundles103a,104a,and the objective optical system109is exposed on a front end face of the front end portion for inspection102a.Further, at the front end face of the front end portion for inspection102a,a transparent protecting cover110made of glass or the like is fixed.

As shown inFIG. 2, in the casing102, a housing of circuit parts102bhaving an opening at the bottom is formed. At both sides of the front end portion for inspection102aof the housing of the circuit parts102b,holding members at the light-receiving side111a,111band holding members at the light-applying side112a,112bare arranged in upper and lower two stages in such a state that respective ones are arranged opposite to one another.

On each of the front faces of the holding members at the light-receiving side111a,111b,which are facing each other, a rear end of a strand in the light-receiving fiber108of each of the fiber bundles103a,104ais held via a ferule (not shown). Further, to each of back faces of the holding members at the light-receiving side111a,111b,a photosensor113corresponding to each light-receiving fiber108is fixed. The light-receiving face of each photosensor113has a continuity with each light-receiving fiber108via the ferule (not shown).

On the other hand, on each of the holding members at the light-applying side112a,112b,a rear end of a strand in the light-applying fiber107of each of the fiber bundles103a,104ais held via a ferule (not shown). Further, to each of side faces of the holding members at the light-applying side112a,112b,which are facing the light-applying fiber107, a semiconductor laser generator114as a laser beam source is fixed. The light-applying face of each semiconductor laser generator114has a continuity with each light-applying fiber107via the ferule (not shown).

Further, circuit boards at the light-receiving side115a,115bare provided at the back faces of the holding members at the light-receiving side111a,111b,and circuit boards at the light-applying side116a,116bare provided at the holding members at the light-applying side112a,112b.

As shown inFIG. 7, on each of the circuit boards at the light-applying side116a,116b,a semiconductor laser generator114is mounted and at the same time, a head amplifier117of a predetermined input impedance for supplying a voltage to each semiconductor laser generator114is provided. This head amplifier117is connected to a constant voltage circuit120provided in an external unit119via an external connection cable118.

In addition, on each of the circuit boards at the light-receiving side115a,115b,a photosensor113is mounted and at the same time, an amplifying circuit121for amplifying the voltage photoelectrically converted with the photosensor113is provided. This amplifying circuit121is connected to an arithmetic circuit123provided in the external unit119via a signal cable for external connection122. An opening portion of the housing of circuit parts102bis closed with a cover not shown.

Moreover, numeral W inFIGS. 5 and 6denotes a subject to be inspected W in a disk shape, for example, CD (compact disk), DVD (digital versatile disk) or HD (hard disk). The photosensor device100is provided in an inspection step of a production line for the subject to be inspected W. An inspection light is applied or irradiated over the surface of the subject to be inspected W from the light-applying fiber107, the reflected light is received by the photosensor113via the light-receiving fiber108, and the presence or absence of scratches, pinholes or distortion on the surface of the subject to be inspected W is inspected based on the received light intensity.

Then, explanation will be made about the operation of this embodiment having the above structure. When a driving voltage is transmitted from the constant voltage circuit120provided in the external unit119to the photosensor device100via the external connection cable118, the driving voltage is supplied to respective semiconductor laser generators114from the head amplifier117mounted on the circuit boards at the light-applying side116a,116bwhich are provided in the casing of the photosensor device100, and then the inspection light is emitted from the semiconductor laser generators114. The inspection light is introduced into the light-applying fiber107, and focused in a predetermined manner with an objective optical system109and irradiated on the surface of the subject to be inspected W.

Then, the reflected light from the surface of the subject to be inspected W is introduced into the light-receiving fiber108via the objective optical system109, and received by the photosensor113. The quantity of the reflected light is photoelectrically converted, and then amplified in a predetermined manner with the amplifying circuit121, and output to the arithmetic circuit123provided in the external unit119via the signal cable for external connection122.

When scratches, pinholes, distortion or the like is formed on the surface of the subject to be inspected W, since the reflected light is scattered, the quantity of the reflected light to be received by the photosensor113is reduced, and the voltage output from the amplifying circuit121is also reduced.

In the arithmetic circuit123, based on the voltage value output from the amplifying circuit121, presence or absence of scratches, pinholes or distortion on the surface of the subject to be inspected W is inspected.

For example, when the fiber arrays103,104are provided in two lines and the length thereof in the direction of lines is equal to the radius of the recording face provided on the disk-like subject to be inspected W, the presence or absence of scratches or the like on the entire surface of the rotating disk-like subject to be inspected W can be inspected, by moving the photosensor device100at a predetermined speed in a direction of the lines of the fiber arrays103,104by ½ of the pitch P of respective fiber bundles103a,104aconstituting the fiber arrays103,104.

Incidentally, respective fiber arrays103,104may be constituted by 9 channels or larger, or 7 channels or smaller, otherwise the fiber arrays may be arranged in three or more lines with the pitch shifted. Further, respective fiber arrays may be radially arranged.

According to this embodiment, since the semiconductor laser generator114and the photosensor113are enclosed in the casing102of the photosensor device100, the photosensor device100may be connected to the external unit119only with the external connection cable118for voltage supply to supply the driving voltage to the semiconductor laser generator114and the signal cable for external connection which transmits the electric signal photoelectrically converted by the photosensor113, whereby the connection operation can be made easily.

Further, since it is no longer required to connect the casing102and the external unit119with a fiber cable, the entire system can be simplified and low production cost can be realized. Further, since the external connection cable is made of only an electric cable, the durability of the external connection cable can be improved and the reliability of product can be improved.

Moreover, since the semiconductor laser generator114is enclosed in the casing102, not only the length of the light-applying fiber107which introduces the inspection light from the semiconductor laser generator114into the direction of light application, can be remarkably shortened, but also the light-applying fiber107can be secured inside the casing102, whereby stable inspection light properties without incorporation of noise can be obtained.

The housing of circuit parts102bof the casing102may be encapsulated with, if necessary, fillers such as grease, resins, powder which hardly impart a pressing force to the light-applying fiber107and the light-receiving fiber108, so as to improve the vibration resistance.

Next, a perspective view of a photosensor device according to the second embodiment of the present invention is shown inFIG. 8. In the above first embodiment, two lines of the fiber arrays103,104are provided in the photosensor device100. In a photosensor device131according to the second embodiment, a fiber bundle made of one light-applying fiber107and one light-receiving fiber108(reference can be made toFIG. 1) is provided at the front end portion for inspection131aof a cylindrical shape.

Inside a casing132of the photosensor device131, a substrate (not shown) on which a semiconductor laser generator and a photosensor are mounted, is enclosed, and the semiconductor laser generator and the light-applying fiber, and the photosensor and the light-receiving fiber are connected with ferules.

According to this structure, since the semiconductor laser generator and the photosensor are enclosed in a casing132, it is no longer required to connect the casing132and an external unit with a fiber cable like in the first embodiment, whereby the entire system can be simplified and low production cost can be realized. In addition, the durability of the external connection cable can be improved and the reliability of product can be improved.

In this instance, the fiber array may be constructed by combining a plurality of photosensor devices131.

Next,FIGS. 9 to 16show the first embodiment of the disk inspection apparatus of the present invention utilizing the above-mentioned photosensor device.FIG. 9is a perspective view of a handler unit having the disk inspection apparatus incorporated therein.FIG. 10is a view of the system structure of the disk inspection apparatus.FIG. 11is a perspective view of a photosensor body.FIG. 12is a plane view of the photosensor body.FIG. 13is a schematic side view of the photosensor body.FIG. 14is a circuit diagram of the photosensor body.

Numeral201inFIGS. 9 and 10denotes a rotary driving portion of the disk inspection apparatus. At the front end portion of a spindle202aprotruding from a built-in motor202(reference can be made toFIG. 14) , a rotary table204is provided. On this rotary table204, a disk W such as a finished or semi-finished CD (compact disk) is mounted.

Further, on the surface Wf of the disk W to be mounted on the rotary table204(the underside surface of the disk in the drawings), a front end portion for inspection205aof a photosensor body205is provided opposite to the surface Wf with a predetermined distance. The photosensor body205is mounted on and fixed to a slide table206. To the slide table206, is connected a ball screw207aof a slide motor207which is a transferring means for reciprocatively moving the slide table206in a direction substantially perpendicular to the rotation direction of the disk W, along the surface Wf of the disk W. This slide motor207is connected to a driving unit208.

As shown inFIG. 14, the driving unit208is provided with a motor control portion209which outputs a driving signal to the slide motor207, a constant voltage circuit210which supplies a constant voltage to the photosensor body205, and an A/D converter211which converts an analog signal from the photosensor body205to a digital signal.

On the other hand, on the front end portion for inspection205aof the photosensor body205, fiber arrays212,213are arranged in two lines. These fiber arrays212,213are constituted by fiber bundles212a,213aeach having 8 channels. Respective fiber bundles212a,213aare arranged with a predetermined pitch P in such a state that a fiber bundle212aand an adjacent fiber bundle213aare arranged with a phase shifted by a half pitch.

Each of the fiber bundles212a,213ais constituted by a light-applying fiber214and a light-receiving fiber215which are bundled. At the front end portion of each of the fiber bundles212a,213a,an objective optical system (not shown) is provided.

Further, as shown inFIG. 14, at the rear end of the light-applying fiber214of each of the fiber bundles212a,213a,a laser beam source216such as a semiconductor laser generator is provided opposite to the rear end. In addition, a photosensor217is provided opposite to the rear end of the light-receiving fiber215. The light-applying fiber214and the laser beam source216, and the light-receiving fiber215and the photosensor217, are connected via ferules (not shown).

Each laser beam source216is connected to a head amplifier218of a predetermined input impedance provided in the photosensor body205, and this head amplifier218is connected to the constant voltage circuit210provided in the driving unit208.

Further, each photosensor217is connected to an amplifying circuit220, and this amplifying circuit220is connected to the A/D converter provided in the driving unit208.

Moreover, as shown inFIGS. 10 and 14, the driving unit208is connected to a control unit222aof a host computer222. Here, numeral222bdenotes a monitor. In the control unit222a,based on the output signal from the photosensor217provided in the photosensor body205, the presence or absence of scratches, pinholes or distortion on the surface Wf of the disk W is inspected.

Further, as shown inFIG. 9, the rotary table204is incorporated in a handler unit223which is interposed in the line for transferring the disk W. The handler unit223has a handler223awhich sucks the disk W conveyed from a transport line224at the upstream side and places the disk W on the rotary table204, and also sucks the disk W mounted on the rotary table204and transfers it to a transport line at the downstream side (not shown). Here, the handler unit223is controlled and operated based on the signals from the control unit222a.

Next, the operation of the embodiment of the above structure will be explained. When the disk W is conveyed from the transport line224at the upstream side, the handler223aof the handler unit223moves synchronistically, and sucks the disk W, and then put the disk W on the rotary table204of the disk inspection apparatus.

Whereupon, the rotary table204rotates, and then the slide motor207connected via a ball screw207ato the slide table206on which the photosensor body205is mounted opposite to the surface Wf of the disk W, rotates, thereby moving the photosensor body205at a predetermined speed in a direction substantially perpendicular to the rotation direction of the disk W.

On the other hand, a driving voltage is supplied from the constant voltage circuit210provided in the driving unit208of the disk inspection apparatus to each laser beam source216via the head amplifier218, whereby an inspection light is emitted from the laser beam source216.

The inspection light is introduced into the light-applying fiber214of each of the fiber bundles212a,213aconstituting the fiber arrays212,213provided at the front end portion for inspection205aof the photosensor205, and focused in a predetermined manner with an objective optical system (not shown), and irradiated on the surface Wf of the disk W.

Then, the light reflected from the surface Wf of the disk W is introduced into the light-receiving fiber215of each of the fiber bundles212a,213avia an objective optical system (not shown) , and received by the photosensor217, and then the quantity of the reflected light is photoelectrically converted to output a predetermined voltage value.

This voltage value is amplified in a predetermined manner with the amplifying circuit220, and output to the driving unit208, and the analog signal is converted to a digital signal with the A/D converter211provided in the driving unit208, and then the digital signal is output to the control unit222aof the host computer222.

In the control unit222a,based on the voltage value corresponding to the quantity of the reflected light detected by the photosensor217, the presence or absence of scratches, pinholes or distortion on the surface Wf of the disk W is inspected. Namely, when defects such as scratches, pinholes or distortion exist on the surface Wf of the disk W, since the reflected light is scattered, the quantity of the reflected light received by the photosensor217is reduced, and the voltage output from the amplifying circuit220is also lowered, whereby this disk is judged to be defective. The result of the judgement is displayed on the monitor222b.

Incidentally, as shown inFIG. 12, when the length of each of the fiber arrays212,213in two lines is set so as to substantially cover at least the recording area in the radius direction of the surface Wf of the disk W, since respective fiber arrays212,213are arranged in a state that the phases thereof are shifted with a half pitch, the presence or absence of defects on the entire recording surface of the surface Wf of the disk W can be inspected only by transferring the photosensor body205by a half of the pitch P of the fiber bundles212a,213ain a predetermined speed.

Accordingly, in this embodiment, the defects on the surface Wf of the disk W can be inspected only with the quantity of the reflected light detected by the photosensor217.

As mentioned above, according to this embodiment, since the photosensor body205is transferred, the fiber arrays212,213may be constituted by the fiber bundles212a,213aarranged with a predetermined pitch P without arranging the fiber bundles212a,213adensely, and since the presence or absence of defects can be inspected based on the quantity of the reflected light, arithmetic processing can be made easily and the apparatus can be produced at a low cost in total.

Since the unit cost of product of the disk inspection apparatus is relatively low, in, for example, the production line of CD (compact disk) as shown inFIG. 15, handler units223having the disk inspection apparatuses of this embodiment incorporated may be arranged between a step M1for molding a polycarbonate resin molded substrate and a step M2for coating a recording film on the surface of the substrate with a spin coater, etc.; between the step M2and the subsequent step M3for providing a reflection film on the surface thereof; and in a step M5for inspecting finished products.

As a result, the presence or absence of defects on the surface Wf of semi-finished disk W can be inspected between respective steps, whereby the yield of products can be improved.

In this case, as shown inFIG. 16, in a production line of, for example, DVD (digital versatile disk) wherein disks W separately produced in the same steps as the production steps of CDs are bonded to each other in the final step M4, the handler units223having the disk inspection apparatuses incorporated according to this embodiment may be arranged between respective steps to still further improve the yield of products.

Namely, in a case where inspection is made only on finished products as in a conventional process, even if a disk W in one production line is non-defective, a finished product will be judged to be defective if a disk W in another production line is defective. However, as in this embodiment, by incorporating the inspection apparatuses between respective lines, the defective quality can be detected instantaneously at the step of semi-finished products, whereby the yield of products can be improved.

In this case, respective fiber arrays212,213may be constituted by 9 or more channels, or 7 or smaller channels. Further, the fiber arrays may be constituted by 3 or more lines, and arranged with the phases shifted. Moreover, respective fiber arrays may be arranged radially.

Next,FIG. 17shows a schematic view of a disk inspection apparatus according to the second embodiment of the present invention. As shown in this drawing, a magnetic recording disk W constituting a hard disk device (HDD) of a computer is produced by forming a disk-like shape by using a material such as aluminum or glass, and coating its surface with a magnetic material.

Accordingly, in a case of the magnetic recording disk W, photosensor bodies205are arranged at both surfaces of the magnetic recording disk W, and in the same operation as in the first embodiment, respective photosensor bodies205are reciprocatively moved, during which the presence or absence on the surface of the magnetic recording disk W is inspected.

In this case, by inspecting the edge section W′ of the magnetic recording disk W with a single photosensor205′, presence or absence of cracks which are likely to form at edged portions can also be inspected.

As explained above, according to the photosensor device of the present invention, since the light-applying fiber, light-receiving fiber, laser beam source and photosensor are enclosed in one casing, connection with external units with a fiber cable is no longer required, and the durability of the external connection cable can be improved and the reliability of the entire system can also be improved.

Further, according to the disc inspection apparatus of the present invention, since the presence or absence of defects on the disk surface can be inspected using fiber arrays, the unit price of apparatus can be made relatively low, and thus even if a plurality of the apparatuses are arranged in the production steps, the cost for equipment is not substantially affected. In addition, by arranging a plurality of the apparatuses in the production steps, it is possible to detect the defects during the production instantaneously, whereby the yield of products can be improved.