JP3815628B2 - Optical inspection system for workpieces - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a workpiece optical inspection apparatus that inspects the presence or absence of fine scratches on a workpiece surface or distortion.
[0002]
[Prior art]
In general, there is an optical inspection device as a non-contact type inspection for minute scratches on a workpiece surface or adhesion of minute foreign matters. As shown in FIG. 7, this optical inspection apparatus condenses inspection light emitted from a light source 1 such as a light-emitting diode on the surface of a work 3 via an objective lens 2 and reflects the reflected light to the inspection light. The light is received by the photosensor 5 through another objective lens 4 disposed at a sandwiching angle α with respect to the optical axis, and based on the amount of reflected light (output voltage of the photosensor) and the property of the surface of the workpiece 3. By comparing with the set threshold level, the surface of the workpiece is inspected for the presence or absence of flaws, adhesion of foreign matter, or distortion. That is, when the workpiece surface is flat, the reflected light from the workpiece surface is totally reflected in the direction of the photosensor, and when the workpiece surface is scratched, foreign matter, etc., or distorted. If the light is reflected, the reflected light is scattered or declined, and the amount of reflected light received by the photosensor 5 is reduced. As a result, when the intensity (output voltage) of the reflected light detected by the photosensor changes and the output voltage of the photosensor is lower than the threshold level, it is determined that there is a scratch or the like on the workpiece surface.
[0003]
[Problems to be solved by the invention]
However, in the conventional optical measuring device, the light emitting system and the light receiving system are arranged at positions close to the workpiece, and therefore the sandwich angle α between them is determined by the shape of the light source and the photosensor. The Accordingly, there is a limit to narrowing the sandwiching angle α. Further, it is extremely difficult to detect minute scratches, distortions, and the like only by a change in the output voltage of one photosensor, and erroneous detection is likely to occur simply by increasing the detection sensitivity as a countermeasure.
[0004]
Therefore, in a conventional optical inspection apparatus composed of light-emitting and light-receiving elements, microscopic scratches formed on the surface of a glass substrate such as a liquid crystal display, a silicon wafer used for a semiconductor, a ceramic substrate, or the like, or visually confirmed It has been difficult to detect, for example, adhesion of foreign matters that are difficult to detect and slight distortion with high accuracy.
[0005]
Accordingly, an object of the present invention is to provide an optical inspection apparatus for a work that can detect a fine flaw or distortion formed on the work surface at a low cost with high accuracy.
[0006]
[Means for Solving the Problems]
An optical inspection apparatus for a workpiece according to the present invention has an inspection optical tip on the surface of the workpiece so as to be relatively movable, and a single projection that emits inspection light from a light source to the workpiece surface. The optical fiber and a light receiving fiber that receives the reflected light from the work surface of the inspection light are bundled together, and the light receiving fiber is all disposed in contact with the light projecting fiber. A plurality of portions are arranged in an array, and a photosensor is disposed at the output end of the light receiving fiber.
An optical inspection apparatus for a workpiece according to a first preferred embodiment of the present invention is provided with a plurality of light receiving fibers in each of the fiber bundles, and the plurality of light receiving fibers are divided into a plurality of light receiving fiber groups. Photosensors are disposed at the emission ends, respectively, one photosensor is directly connected to the inspection calculation unit, the other photosensor is connected to the inspection calculation unit through an inverting circuit, and the inspection calculation unit is Comparing the difference between the output voltage from one photosensor and the output voltage from the other photosensor that has passed through the inverting circuit and a preset threshold level, and detecting the presence or absence of scratches on the workpiece surface It is characterized by being.
[0007]
The workpiece optical inspection apparatus according to the second preferred embodiment of the present invention is provided with a plurality of light receiving fibers in each of the fiber bundles, and the plurality of light receiving fibers are divided into a plurality of light receiving fiber groups. Photosensors are provided at the emission ends, and the photosensors are connected to an inspection calculation unit that detects distortion of the work surface based on a difference in output voltages of the photosensors.
[0009]
[Action]
According to the workpiece optical inspection apparatus of the present invention, the inspection light from the light source is emitted to the surface of the workpiece via the light projecting fiber, and the reflected light is guided to the photo sensor via the light receiving fiber. It is possible to form the inspection optical front end portion facing the workpiece surface in an extremely small size, and to detect minute scratches or distortion on the workpiece surface.
In the optical inspection apparatus for the first workpiece, the inspection light from one light projecting fiber in at least one fiber bundle provided at the inspection optical tip is moved relative to the inspection optical tip. The reflected light is incident on the plurality of light receiving fibers of the fiber bundle. Then, the reflected light emitted from each of the light receiving fibers is received by a photosensor disposed at the light emitting ends of the two light receiving fibers that divide each of the light receiving fibers, and the reflected light amount is converted into a voltage, and then the inspection calculation unit Thus, the difference between the output voltage from one photosensor and the voltage obtained by inverting the output voltage from the other photosensor is obtained, and the difference voltage is compared with a preset threshold level to cause scratches or foreign matter on the workpiece surface. Inspect for the presence of adhesion.
[0010]
In the optical inspection apparatus for the second workpiece, the inspection light from one light projecting fiber in at least one fiber bundle provided at the inspection optical tip is moved relative to the inspection optical tip. The reflected light is incident on the plurality of light receiving fibers of the fiber bundle. Then, the reflected light emitted from each light receiving fiber is received by a photo sensor provided at the light emitting end of each light receiving fiber group in which each light receiving fiber is divided into predetermined parts, and the reflected light amount is converted into a voltage, and then inspected. The calculation unit obtains the difference between the output voltages of the photosensors, and inspects the distortion of the workpiece surface based on the difference voltage.
[0011]
Further, in the first and second workpiece optical inspection apparatuses, the inspection optical tip portion is constituted by a fiber array in which a plurality of the fiber bundles are arranged, so that the relatively moving workpiece surface can be arranged in rows. Can be inspected.
[0012]
【Example】
Examples of the present invention will be described below with reference to FIGS.
FIG. 1 shows a flat workpiece W and an inspection optical tip 11 of an inspection apparatus provided on the flat workpiece W. The flat workpiece W is a glass substrate of a liquid crystal display, a ceramic substrate, a light receiving surface of a solar cell, or the like, and is placed on a table (not shown) that can move relative to the inspection optical tip 11.
[0013]
The inspection optical tip 11 is a fiber array in which a plurality of sets of fiber bundles 12 are arranged in a line in the width direction of the flat work W, and the fiber bundles 12 constituting the fiber array correspond to each other. It is composed of one light projecting fiber 13 and two light receiving fibers 14a and 14b that are bundled in contact with each other. Further, as shown in FIG. 2, an objective optical system 15 is attached to the tip of each fiber bundle 12, and the surface of the flat workpiece W is exposed on the focal point of the objective optical system 15.
[0014]
On the other hand, as shown in FIG. 3, the base end side of each of the fiber bundles 12 is faced to the corresponding computing device 21. The calculation device 21 includes a light source unit 21A and an inspection calculation unit 21B, and an incident end of the light projecting fiber 13 faces the light source unit 21A. The light receiving fibers 14a and 14b are divided into two light receiving fiber groups 16a and 16b, and the emission ends of the light receiving fiber groups 16a and 16b face the inspection calculation unit 21B. In this embodiment, since there are two light receiving fibers, each of the light receiving fibers 14a and 14b has a one-to-one correspondence with the light receiving fiber groups 16a and 16b. When there are more (preferably even number), the individual light receiving fibers are appropriately divided into light receiving fiber groups 16a and 16b (for example, every half if there are even numbers), and faced to the inspection calculation unit 21B. .
[0015]
The light source section 21A is provided with an LED driver 22, and an incident end of the light projecting fiber 13 is opposed to a light emitting diode 23 that emits light in response to a drive signal from the LED driver 22. Further, in the inspection calculation unit 21B, photosensors 24a and 24b are respectively provided at the emission ends of the light receiving fiber groups 16a and 16b. The photosensors 24 a and 24 b are connected to the amplifier circuits 25 a and 25 b, respectively, and one amplifier circuit 25 a is connected to one input terminal of the differential amplifier circuit 28. The other amplifier circuit 25b is connected to an analog switch 26 such as an analog multiplexer. The analog switch 26 has a two-channel configuration, and one output terminal is connected to the other input terminal of the differential amplifier circuit 28 via an inverting circuit 27, and the other output terminal is the other terminal of the differential amplifier circuit 28. Is directly connected to the input terminal. The analog switch 26 selects any channel in a time-sharing manner or arbitrarily according to a control signal output from a control device (not shown). The differential amplifier circuit 28 outputs a voltage proportional to the difference between the two input signals.
[0016]
Further, the output terminal of the differential amplifier circuit 28 is connected to one input terminal of the comparison circuit 29, and the threshold level setting circuit 30 is connected to the other input terminal. The comparison circuit 29 compares the differential voltage output from the differential amplifier circuit 28 with the threshold level output from the threshold level setting circuit 30 and outputs the result to a post-processing circuit 31 including a counter and the like. On the other hand, the other output terminal of the differential amplifier circuit 28 is connected to a post-processing circuit 32 including an A / D conversion circuit. The threshold level is a threshold value for determining the presence or absence of scratches Wo (or adhesion of foreign matter) on the surface of the flat workpiece W, and is set based on the surface properties of the flat workpiece W to be inspected. Yes.
[0017]
The inspection operation unit 21B selectively inspects the presence or absence of a scratch Wo (or adhesion of foreign matter) or the like on the surface of the flat workpiece W and the distortion θ by the switching operation of the analog switch 26. That is, when the analog switch 26 outputs the output signal from the amplifier circuit 25b to the inverting circuit 27, the surface of the flat workpiece W is inspected for scratches Wo (or adhesion of foreign matter) and the like. The result is processed by the post-processing circuit 31. When the output signal from the amplifier circuit 25b is directly output to the differential amplifier circuit 28, the surface distortion θ of the flat workpiece W is inspected, and the result includes the A / D converter circuit. It is output to the processing circuit 32.
[0018]
Next, the operation of the embodiment having the above configuration will be described.
A flat work W is placed on a table (not shown) of the inspection apparatus, the table is moved relative to the flat work W, and the flat work W is transferred to the inspection optical tip 11. Inspection light from the light-emitting diodes 23 provided in the light source part 21A of the arithmetic unit 21 shown in FIG. 3 is emitted from the light projecting fibers 13 provided in the fiber bundles 12 of the inspection optical tip part 11, and the objective optical system 15 The surface of the flat workpiece W is irradiated through
[0019]
On the other hand, when the inspection light reflected from the surface of the flat workpiece W is incident on the two light receiving fibers 14a and 14b through the objective optical system 15, the reflected light is reflected on the light receiving fibers 14a and 14b. Are received by the photosensors 24a and 24b provided in the inspection calculation unit 21B of the calculation device 21 from the emission ends of the light receiving fiber groups 16a and 16b corresponding to one-to-one in this embodiment, After the reflected light amount is converted into a voltage, it is amplified to a predetermined level by the amplifier circuits 25a and 25b. The reflected light is scattered when scratches (or deposits or the like) Wo are present on the surface of the flat workpiece W, so that the amount of light received by the photosensors 24a and 24b is reduced, and the amplification circuit 25a is reduced. , 25b also has a low voltage.
[0020]
The output voltage from one amplifier circuit 25a is output to one input terminal of the differential amplifier circuit 28, and the output voltage from the other amplifier circuit 25b is passed through the analog switch 26 to the current inspection item. Is output to the inverting circuit 27 when the inspection is for the presence or absence of scratches Wo on the surface of the flat workpiece W, and the current inspection item is an inspection of the strain θ on the surface of the flat workpiece W. Is directly output to the other input terminal of the differential amplifier circuit 28.
[0021]
In the following description, the case of inspecting the presence or absence of scratches Wo on the surface of the flat workpiece W will be described first, and then the case of inspecting the strain θ of the surface of the flat workpiece W will be described.
[0022]
When the output voltage from the amplifier circuit 25b is inverted by the inverting circuit 27 through the analog switch 26 and then input to the other input terminal of the differential amplifier circuit 28, the input voltage is input to one input terminal. A voltage proportional to the difference from the output voltage from the amplifier circuit 25a is output. The two output voltages input to the amplifier circuit 25a are obtained by photoelectrically converting the reflected light of the same inspection light reflected by the surface of the workpiece W. Therefore, the two output voltages are inverted by inverting one of the output voltages. By obtaining the voltage difference, the change in the output voltage is increased and the sensitivity is remarkably improved, and the sensitivity of the difference voltage, which is usually about 0.2 V, increases to 1.0 to 2.0 V.
[0023]
Then, the differential voltage output from the differential amplifier circuit 28 is input to one input terminal of the comparison circuit 29, and compared with the threshold level from the threshold level setting circuit 30 input to the other input terminal. This threshold level predicts the increase amount of the differential voltage output from the differential amplifier circuit 28 when there is a fine flaw (or a deposit or the like) Wo on the surface of the work W, and the differential voltage is It is set in advance as a threshold value that can detect the increase to such a value.
[0024]
The comparison circuit 29 outputs an H signal to the post-processing circuit 31 when the differential voltage is equal to or higher than the threshold level, and an L signal when the differential voltage is equal to or lower than the threshold level. In this post-processing circuit 31, the output signal from the comparison circuit 29 is read every predetermined time in synchronization with the movement amount of the flat plate workpiece W, and the address of the memory corresponding to the movement amount of the flat plate workpiece W is counted. The 1-bit data at the address is set when the H signal is output, and cleared when the L signal is output.
[0025]
This inspection is executed for each arithmetic device 21 connected to each fiber bundle 12, and the data stored in the memory of the post-processing circuit 31 provided in each arithmetic device 21 is represented in a point coordinate system and output. By doing so, the presence or absence of scratches (or deposits or the like) Wo on the surface of the workpiece W and the position of the scratches can be inspected in sequence.
[0026]
On the other hand, when the strain θ on the surface of the flat workpiece W is inspected, the voltage amplified by the amplifier circuit 25 b is directly output from the analog switch 26 to the other input terminal of the differential amplifier circuit 28. The differential amplifier circuit 28 outputs a voltage proportional to the difference between the voltages output from the amplifier circuits 25 a and 25 b to the post-processing circuit 32.
[0027]
As shown in FIG. 2, for example, when the surface of the workpiece W has a distortion of an inclination θ in the upper right direction in the figure, the reflection direction of the inspection light emitted from the light projecting fiber 13 is declined, and the light receiving fiber 14 a The amount of light reflected to the other side is reduced, and the amount of light reflected to the other light receiving fiber 14b is reduced accordingly. As a result, the amount of reflected light emitted from the light receiving fiber 14a and received by the photosensor 25a is P + δP (δP: variation with respect to the inclination θ), where P is the amount of light received when flat, and the other light receiving The amount of reflected light received by the other photosensor 25b through the fiber 14b is P-δP.
Since the voltage output from the differential amplifier circuit 28 is a voltage proportional to the difference between the light amounts (P + δP, P−δP), the surface of the flat workpiece W is flat (θ = 0). If the inclination θ is distorted, a voltage corresponding to + 2δP or −2δP is output to the post-processing circuit 32 depending on the direction of the inclination.
[0028]
In the post-processing circuit 32, the voltage output from the differential amplifier circuit 28 is A / D converted, and this data is stored in the memory at predetermined intervals in synchronization with the amount of movement of the flat workpiece W. Then, by expressing the inspection result in the point coordinate system for each arithmetic device 21, the degree of distortion of the entire surface of the workpiece W can be grasped with specific numbers.
[0029]
When inspecting either a scratch or a distortion on the surface of the flat workpiece W, the two light receiving fibers 14a and 14b are opposed to the workpiece surface at extremely close positions. These changes are offset each other.
[0030]
Furthermore, in this embodiment, one light projecting fiber 13 and two light receiving fibers 14a and 14b are bundled in an array having a minimum cross-sectional area, but the size and state of the workpiece to be inspected. For example, as shown in FIG. 4, two light receiving fibers 14a and 14b may be arranged on both sides of the light projecting fiber 13, as shown in FIG. As described above, the four light receiving fibers 14a to 14d are arranged in a cross shape around the light projecting fiber 13, or the light receiving fibers 14a to 14f are arranged around the light projecting fiber 13 as shown in FIG. A plurality of may be provided. In this case, the emission end side of each of the light receiving fibers 14a to 14d or 14a to 14f is divided into two light receiving fiber groups 16a and 16b, which are guided to the inspection operation unit 21B of the arithmetic unit 21 shown in FIG. It is burned.
[0031]
【The invention's effect】
As described above, according to the present invention, the inspection light from the light source is emitted to the work surface through the light projecting fiber, and the reflected light is guided to the photosensor through the light receiving fiber. It is possible to form the inspection optical front end portion facing the surface in a minimum size, and it is possible to detect minute scratches or distortions on the workpiece surface.
[0032]
In addition, the reflected light from the workpiece surface of the inspection light emitted from one light projecting fiber is incident on a plurality of light receiving fibers, and each of the received reflected light is divided into respective light receiving fiber groups. In addition, the photo sensor is used to receive light so that fine scratches or distortions formed on the workpiece surface can be detected with high sensitivity, and the inspection accuracy can be greatly improved. Cost reduction can be realized.
[Brief description of the drawings]
FIG. 1 is a plan view of a workpiece and an inspection optical tip portion shown in a II cross section in FIG.
FIG. 2 is a side view of FIG.
FIG. 3 is a circuit diagram of an arithmetic unit.
FIG. 4 is a cross-sectional view of a fiber bundle according to another embodiment.
FIG. 5 is a cross-sectional view of a fiber bundle according to another embodiment.
FIG. 6 is a cross-sectional view of a fiber bundle according to another embodiment.
FIG. 7 is a schematic explanatory diagram of a conventional optical inspection apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Inspection optical front-end | tip part 12 ... Fiber bundle 13 ... Projection fiber 14a-14f ... Light receiving fiber 16a, 16b ... Light receiving fiber group 21A ... Light source 21B ... Inspection calculating part 24a, 24b ... Photosensor W ... Workpiece | work

Claims (3)

The inspection optical tip is placed on the work surface so that it can be moved relatively.
This inspection optical tip, the inspection light from the light source to unity and one light projecting fiber emitted to the workpiece surface, and a light receiving fiber you incident reflected light from the work surface of the inspection light formed is, the light receiving fiber is arranged the leading end of the fiber bundle all of which are disposed in contact with the light projecting fiber into a plurality of sets array Te,
An optical inspection apparatus for a workpiece, wherein a photosensor is disposed at an emission end of the light receiving fiber . Each of the fiber bundles is provided with a plurality of light receiving fibers, the plurality of light receiving fibers are divided into a plurality of light receiving fiber groups,
Photosensors are disposed at the output ends of the respective light receiving fiber groups,
One photo sensor is directly connected to the inspection calculation unit, and the other photo sensor is connected to the inspection calculation unit through an inverting circuit,
The inspection calculation unit compares the difference between the output voltage from the one photosensor and the output voltage from the other photosensor that has passed through the inverting circuit with a preset threshold level to determine whether the surface of the workpiece is damaged. The workpiece optical inspection apparatus according to claim 1 , wherein the presence or absence of the workpiece is detected. Each of the fiber bundles is provided with a plurality of light receiving fibers, the plurality of light receiving fibers are divided into a plurality of light receiving fiber groups,
Photosensors are disposed at the output ends of the respective light receiving fiber groups,
2. The workpiece optical inspection apparatus according to claim 1 , wherein each of the photosensors is connected to an inspection operation unit that detects distortion of the workpiece surface based on a difference between output voltages of the photosensors.

Images