JP2006038553A - Imaging apparatus and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus for calibrating the difference between a plurality of imaging systems, each of which is composed of an imaging part and an illumination system, without decreasing inspection sensitivity and an inspection speed, an imaging method and an inspection device using the imaging method. <P>SOLUTION: The imaging apparatus is composed of a plurality of the imaging systems respectively having imaging parts and has an exposure time coefficient calculating part for reading the brightness data corresponding to the exposure times of all of the imaging parts to calculate the exposure time coefficient at every imaging part from the brightness data and an exposure time calculating part for multiplying a predetermined exposure time by the exposure time coefficient corresponding at every imaging part to calculate an image exposure time used in the imaging of each imaging part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, a plurality of imaging systems including an imaging unit and an illumination are mounted so as to capture a wide area of a substrate on which a device is formed, so that a substrate image having the same luminance can be obtained in all imaging units. The present invention relates to an image pickup apparatus that removes machine differences between individual image pickup units and an illumination system, and a defect inspection apparatus using the image pickup apparatus.

2. Description of the Related Art Conventionally, when attempting to image a wide area, in order to reduce the time required for imaging, a plurality of imaging systems are provided and the above-described area is imaged at once in an inspection apparatus or the like.
However, as described above, when one image is acquired using a plurality of imaging systems, it is necessary to solve the problem of variation in characteristics between the imaging systems as compared to the case where a single imaging system is used. .
In particular, inspection apparatuses for pattern defects and the like are equipped with a plurality of imaging units and illumination systems as the inspection area is widened, and simultaneously inspects to realize a reduction in inspection time.

For this reason, it is necessary to make settings so that a substrate image with the same brightness can be obtained in all imaging units for a subject with uniform reflectance, and the defect extraction target differs for each process substrate to be inspected. It is necessary to set an amount of light suitable for defect extraction by processing, that is, to remove machine differences between individual imaging units and illumination systems.
That is, due to variations in the characteristics of the imaging unit and the illumination system of the imaging system, the luminance of the obtained image varies from part to part corresponding to the imaging system.

For this reason, it is necessary to make the characteristics of a plurality of imaging systems uniform, that is, in order to obtain images having the same luminance by a plurality of imaging units, the lighting is dimmed.
However, it is common to use a halogen light source having a long wavelength band in the visible region for illumination, which has several problems.
For example, in the case of a method in which the voltage applied to the light source is varied in order to dim the illumination, the responsiveness of the dimming is poor and the correspondence between the applied voltage and the luminance is not linear, so it is difficult to adjust with high accuracy. Furthermore, the load is applied to the light source due to the variable voltage, which causes deterioration of the characteristics of the light source.

For example, when an ND filter is used for dimming illumination, the amount of light exposed to the substrate cannot be changed instantaneously.
As an improvement measure, there is a method for setting image processing parameters based on image quality for the purpose of making inspection sensitivities the same in a plurality of optical systems included in the apparatus (see, for example, Patent Document 1). ).
JP 2000-67797 A

However, in the pattern inspection apparatus shown in Patent Document 1, in order to make inspection sensitivities the same in a plurality of optical systems included in the apparatus, image processing parameters are set from the image quality of the acquired image. The inspection sensitivity is adjusted according to the image processing parameters. However, it takes time for the image processing, and since it is acquired, there is a limit to the adjustment of the image quality, and the adjustment between the imaging systems cannot always be performed with high accuracy.
The present invention has been made in view of such circumstances, and an imaging apparatus and an imaging system that calibrates machine differences between a plurality of imaging systems, which include an imaging unit and an illumination system, without reducing inspection sensitivity and inspection speed. It is an object of the present invention to provide a method, and an inspection apparatus and an inspection method using the method.

The imaging apparatus according to the present invention is an imaging apparatus including a plurality of imaging systems each having an imaging unit (for example, the imaging unit 1 in the embodiment). Brightness value), and by multiplying a predetermined exposure time by an exposure time coefficient corresponding to each imaging unit, and calculating an exposure time coefficient for each imaging unit from the luminance information, And an exposure time calculation unit that calculates an imaging exposure time used for imaging of each imaging unit.
The imaging method of the present invention is an imaging method in an imaging device including a plurality of imaging systems each having an imaging unit, and reads luminance information corresponding to the exposure time of all imaging units, and from the luminance information for each imaging unit. An exposure time coefficient calculation process for calculating an exposure time coefficient, and an exposure time for calculating an imaging exposure time used for imaging of each imaging unit by multiplying a predetermined exposure time by an exposure time coefficient corresponding to each imaging unit. And a calculation process.

With the above-described configuration, the imaging apparatus and imaging method of the present invention correct the machine difference between the imaging systems composed of the imaging unit and the illumination device, and provide the same luminance between all imaging systems from the same imaging target. Since the same imaged object is imaged as a plurality of partial images by a plurality of imaging systems to generate the entire image of the imaged object, image processing after imaging is not performed. Therefore, it does not slow down the imaging and composition processing, and because it absorbs machine differences between the imaging systems at the time of imaging, it creates a whole image that is calibrated with high accuracy and has no visual discomfort. it can.
The imaging apparatus and imaging method of the present invention does not decrease the speed of imaging and synthesis processing, for example, when mounted on an inspection apparatus that inspects a take-up substrate or the like that creates a plurality of large-area FPD substrates, that is, inspection Since the machine difference between each imaging system is absorbed at the time of imaging without reducing the speed, the brightness of the synthesized result can be adjusted with high accuracy in the entire image, so that the accuracy of inspection can be improved. It becomes possible.

The imaging device of the present invention has an illumination device corresponding to each imaging unit, and a luminance measurement unit that measures the luminance received by all the pixels for each imaging unit by a calibration sample; And a dimming control unit that adjusts the amount of light of the illumination device with respect to the predetermined exposure time so that the maximum value of the luminance becomes a predetermined threshold value.
The imaging method according to the present invention includes a luminance measurement process for measuring the luminance of light received by all pixels for each imaging unit using a calibration sample, and the predetermined exposure time so that the maximum value of the luminance becomes a predetermined threshold value. On the other hand, it has a dimming control process for adjusting the light quantity of the illumination device corresponding to each imaging unit.
In the imaging apparatus of the present invention, the threshold value is a maximum in a range in which the luminance value is a linear function of brightness in the correspondence relationship between the brightness received by the light receiving unit of the imaging unit and the output brightness value at a predetermined exposure time. It is a value and is set to the smallest value in all the imaging units.

  With the configuration described above, the image pickup apparatus and the image pickup method of the present invention adjust the light amount of the illumination device so that the luminance of all the pixels of each image pickup unit is equal to or less than a predetermined threshold when correcting the machine difference. As a result, the control range is included in the change area of the linear function, and the machine difference of the imaging system can be controlled with high accuracy.

In the imaging apparatus according to the present invention, the exposure time coefficient calculation unit obtains an average value and 3σ of luminance information for each imaging unit, and subtracts the maximum 3σ from the threshold value in each imaging unit. The result of dividing the average value of the part is output as an exposure time coefficient.
In the imaging method of the present invention, in the exposure time coefficient calculation process, an average value and 3σ of luminance information for each imaging unit are obtained, and the maximum 3σ in each imaging unit is subtracted from the threshold value. A result obtained by dividing the average value of the imaging unit is output as an exposure time coefficient.
With the above-described configuration, the imaging apparatus and imaging method of the present invention have the maximum 3σ in a plurality of imaging systems, and the maximum of the threshold value, that is, the range in which the correspondence between illuminance and luminance in the imaging system has linearity. Since the average value of each imaging unit is subtracted from the value and the result of the division is used as each exposure time coefficient, even if the captured luminance varies, the luminance is corrected within a linear range. It becomes possible.

In the imaging apparatus of the present invention, the exposure time coefficient calculation unit obtains a luminance difference between an average value of luminance information for each imaging unit and a maximum value and a minimum value, and the maximum luminance difference in each imaging unit is determined as the threshold value. And the result obtained by dividing the average value of each imaging unit by the subtraction result is output as an exposure time coefficient.
In the imaging method of the present invention, in the exposure time coefficient calculation process, an average value of luminance information for each imaging unit and a luminance difference between a maximum value and a minimum value are obtained, and the maximum luminance difference in each imaging unit is Subtracting from the threshold value and dividing the average value of each imaging unit by the subtraction result, the result is output as an exposure time coefficient.
With the above-described configuration, the imaging apparatus and imaging method of the present invention have the maximum luminance difference between the maximum value and the minimum value of the luminance in a plurality of imaging systems, and the correspondence relationship between the threshold value, that is, the illuminance and the luminance in the imaging system. Since the average value of each imaging unit is subtracted from the maximum value of the linearity range and the result of the division is used as the exposure time coefficient, linearity can be obtained even if the captured brightness varies. It is possible to correct the luminance within a range having.

The image pickup apparatus of the present invention has a database that stores a reference exposure coefficient for adjusting a predetermined exposure time for each image pickup unit corresponding to an object to be picked up by the image pickup apparatus. .
In the imaging apparatus of the present invention, the exposure time calculation unit reads a reference exposure coefficient corresponding to the imaging target, corresponding to each imaging unit from the database, and multiplies the exposure time multiplied by the exposure time coefficient, It outputs as an imaging exposure time of each imaging part.
With the above-described configuration, the imaging apparatus of the present invention measures and stores in advance a reference exposure coefficient that is adjusted by multiplying this exposure time in order to obtain an exposure time corresponding to each imaging target for each imaging target. Therefore, it is possible to adjust the brightness with high accuracy for any imaging target corresponding to this reference exposure coefficient, and the optimal exposure time at the boundary where the imaging target changes. Since it can be obtained at high speed by simple calculation, the brightness of each imaging system can be adjusted in real time without increasing the inspection time.

  As described above, according to the imaging apparatus and imaging method of the present invention, the machine difference between the imaging systems composed of the imaging unit and the illumination device is corrected, and the same imaging target and the same between all imaging systems. Since an image having the brightness of 1 can be captured, when the same captured object is combined with multiple captured images by a plurality of imaging systems to generate an entire image of the captured object, image processing after capturing is performed. Therefore, the machine difference between the partial images is calibrated with high accuracy and visually. Can create a whole image without any sense of incongruity.

A substrate inspection apparatus equipped with an imaging apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram showing a configuration example of the embodiment.
In this figure, the inspection apparatus includes an imaging system composed of an imaging unit 1 and an illumination device 2, an integrated control unit 4 for adjusting brightness, a holding and moving unit 5 for adjusting the position of the calibration sample 3, and a substrate 8. And a substrate transport unit 7 that moves the substrate 8 on the stage 6.
Here, the present invention is an imaging apparatus including the integrated control unit 4 and a plurality of imaging systems. A plurality of imaging systems are arranged toward the back of the drawing, and each includes an imaging unit 1 and a lighting device 2.
The imaging unit 1 and the lighting device 2 use the same device, but have variations in individual characteristics.

The imaging unit 1 includes, for example, a line sensor in which CCDs (charge coupled devices) that are light receiving elements are arranged in a line in units of pixels.
The illumination device 2 uses, for example, a halogen lamp as a light source, and radiates a predetermined amount of light to the substrate 8 to be imaged.
In addition, the imaging unit 1 receives reflected light that is reflected from the imaging target by the light emitted from the illumination device 2 and outputs predetermined luminance information, that is, digital data indicating a luminance value.

The integrated control unit 4 is a characteristic part of the present invention and will be described in detail later. However, the integrated control unit 4 controls each of a plurality of imaging systems (imaging unit 1 and illumination device 2), and the difference between the imaging systems. The process which reduces is performed.
The calibration sample 3 is used to obtain luminance information for adjusting the light amount of each lighting device 2 and reducing the machine difference between the imaging devices.
The holding / moving unit 5 adjusts the position of the calibration sample 3, that is, when used for calibration, the light emitted from the illumination device 2 is reflected, and the reflected reflected light is reflected on the light receiving unit of the imaging unit 1. When it is not used, it is moved to a position where it does not interfere with the conveyance of the substrate 8 on the stage 6.
The substrate transport unit 7 transports the substrate 8 on the stage 6 at a speed corresponding to the timing at which the imaging system samples the image on the substrate 8.

Next, the inspection apparatus of FIG. 1 will be described in detail with reference to FIG. FIG. 2 is a block diagram showing in detail the configuration of each part of the inspection apparatus.
The integrated control unit 4 includes an image data processing unit 10 and a control management unit 11. Before the inspection, the image data processing unit 10 performs luminance difference adjustment control, and outputs a control result to the control management unit 11. The control management unit 11 adjusts the illumination device 2 and the imaging unit 1 according to the control result.
During the inspection, the image data processing unit 10 generates an inspection image, detects a defective portion from the inspection image, and outputs the coordinates of this portion. The control management unit 11 moves the substrate 8 on the substrate 6 relative to the imaging system at a predetermined speed.

The illumination device 2 includes a light source 13 that emits light with high illuminance, such as a halogen lamp, and a dimming control unit 12 that adjusts the light amount of the light source 13, and a control signal from the control management unit 11. A predetermined amount of light is emitted.
The imaging unit 1 receives external light such as reflected light, converts the incident light amount into a luminance value for each image (pixel) by a light receiving element, and outputs digital data indicating the luminance value; In accordance with a control signal from the control management unit 11, the light receiving unit 1 includes an imaging control unit 14 that controls a time width in which external light is incident, that is, an exposure time, at every sampling timing of a predetermined period. When the imaging unit 1 is a CCD line sensor, the light receiving elements arranged one-dimensionally output a luminance value of one pixel.

The holding / moving unit 5 has a sample up / down drive control unit 16 that adjusts the reflection surface of the calibration sample 3 to the same height as the inspection surface of the substrate 8 with respect to the imaging system on the stage 6.
The substrate transfer unit 7 fixes the substrate 8 to the transfer unit 20, the transfer unit 20 that moves with the substrate 8, the transfer control unit 18 that adjusts the moving speed of the transfer unit 20 to a speed corresponding to the sampling timing, and the transfer unit 20. A substrate clamp unit 21 and a clamp control unit 19 that controls the fixation and release of the substrate 8 in the substrate clamp unit 21 are provided.

Next, the image data processing unit 10 in the imaging apparatus according to the embodiment of the present invention will be described with reference to FIG. Here, FIG. 3 is a block diagram illustrating a configuration example of the image data processing unit 10.
The image data processing unit 10 calculates an exposure time coefficient for adjusting the predetermined exposure time for each imaging unit, an exposure time coefficient calculation unit 30 for calculating an exposure time coefficient, and calculates an exposure time for each imaging unit using the exposure time coefficient. An exposure time calculation unit 31 and a database 32 for storing the exposure time coefficient corresponding to each imaging unit.

Next, with reference to FIGS. 1 to 3 and FIGS. 4 to 7, 9, and 10, the operation of the inspection apparatus equipped with the imaging device of the present invention described above will be described. 4 to 7, 9, and 10 are flowcharts specifically showing an operation example of the inspection apparatus according to the embodiment of FIGS. 1 to 3.
<Measurement preparation process>
First, in the order shown in the flowchart of FIG. 4, before the inspection measurement, the base exposure time in step S1, the exposure time coefficient in step S2, and the reference exposure coefficient in step S3 are sequentially obtained.
The base exposure time is a reference time for obtaining the imaging exposure time that each imaging unit actually uses, and this exposure time is multiplied by an exposure time coefficient that suppresses the influence of machine differences for each imaging unit. Further, the multiplication exposure time is calculated by multiplying the multiplication result by a reference exposure coefficient corresponding to the imaging target (that is, corresponding to the reflectance of the imaging target).

<Base exposure time setting>
First, processing for setting a reference exposure time in step S1 will be described with reference to the flowchart shown in FIG. In setting the base exposure time, a plurality of imaging systems are selected and performed.
The user installs a low reflectance layer substrate (that is, the substrate 8) on the stage 6 (step S11).
Then, when the user inputs an instruction to start the preparation process to the integrated control unit 4, the control management unit 11 outputs a signal to instruct the clamp control unit 19 to clamp the substrate 8, thereby 6, the substrate clamping unit 21 clamps the substrate 8 (step S12).
Here, the term “clamp” means that the substrate clamp unit 21 is brought into a vacuum state by a vacuum suction machine, and the substrate 8 is sucked and fixed to the substrate clamp unit 21.

Next, the control management unit 11 sets the maximum exposure time in the specification of the imaging unit 1 to the imaging control unit 14 (step S13).
Thus, when the imaging instruction is input from the control management unit 11, the imaging control unit 14 controls the light receiving unit 15 to receive external light during the maximum exposure time.
Then, the control management unit 11 outputs a signal that instructs the transport control unit 18 to move to a position where it can be imaged by the imaging system (step S14).
Thereby, the conveyance control part 18 drives the conveyance part 20, and moves the board | substrate 8 to the position which can be imaged with an imaging system.
This position is a place where a feature point on the substrate 8, that is, a portion where it is desired to detect the presence or absence of a defect is imaged by the imaging system.

Next, the control management unit 11 outputs an imaging instruction of the substrate 8 (low reflectance layer substrate) to the imaging control unit 14 (step 15), and the image data processing unit 10 averages the feature points. An instruction is given to calculate the luminance value (step S16). Here, in order to adjust the illuminance of the lighting device, a low-reflectance layer substrate is used. The layer substrate is a display substrate such as an FPD or a semiconductor substrate, and indicates a substrate at the time of processing in each process in manufacturing.
Thereby, the exposure time coefficient calculation unit 30 calculates the average value of the luminance of the light input by all the light receiving elements of the CCD included in the imaging unit 1 in the selected imaging unit 1.
The exposure time coefficient calculation unit 30 determines that the average brightness value (brightness average value) obtained by the imaging unit 1 is in a correspondence relationship between the illuminance of the input light of the imaging unit 1 and the output luminance value. Then, it is determined whether or not the linearity is included, that is, the luminance value is included in a range that is a linear function of the illuminance of light (step S17).

Here, the upper limit within the range is set as a threshold value in the claims, and the lower limit of the range also exists as the lower threshold value. However, since the exposure time is set based on the above threshold value, the lower threshold value is not considered.
Therefore, the control management unit 11 controls the light control unit 12 so that the light emitting unit 13 emits light with the maximum light amount at the start of step S1.

If the exposure time coefficient calculation unit 30 detects that the average brightness value is included in the range of the straight line (does not exceed the threshold value), the process proceeds to step S18. Is not included in the range of the straight line (exceeding the threshold value), the process proceeds to step S19 (step S17).
Next, the exposure time coefficient calculation unit 30 outputs to the control management unit 11 a detection signal that is detected that the luminance average value is not included in the range of the straight line.
As a result, the control management unit 11 outputs a control signal for reducing the predetermined light amount to the dimming control unit 12 of the illumination device 2 of the selected imaging system, and reduces the light amount emitted by the light emitting unit 13. The process returns to step S14 (step S19).

Further, the exposure time coefficient calculation unit 30 outputs a detection signal that is detected that the average luminance value is included in the range of the straight line to the control management unit 11.
Thereby, the control management unit 11 instructs the transfer control unit 1 to move the transfer unit 20, and retracts the substrate 8 on the stage 6 from the position where the calibration sample 3 is moved up and down by the holding and moving unit 5. The process proceeds to step S20 (step S18).
And the control management part 11 instruct | indicates fixing with the applied voltage used as the luminance value contained in the threshold value so that the light quantity which the light emission part 13 light-emits may not be changed with respect to the light control part 12. Step S20).

Next, the control management unit 11 instructs the sample vertical drive control unit 16 of the holding and moving unit 5 to position the calibration sample 3 in the vertical direction (step S21).
As a result, the sample vertical drive control unit 16 sets the surface of the calibration sample 3 at the same position as the inspection surface of the substrate 8 with respect to the imaging system.
Then, when confirming that the calibration sample 3 has been positioned, the control management unit 11 instructs the imaging control unit 14 to image the surface of the calibration sample 3 (step S22).

Next, the control management unit 11 instructs the image data processing unit 10 to calculate the average luminance value of the reflected light that is reflected from the calibration sample 3 and input to the selected imaging system.
As a result, the exposure time coefficient calculation unit 30 calculates an average value of the luminance of light input by all the light receiving elements of the CCD included in the imaging unit 1 in the imaging unit 1.
The exposure time coefficient calculation unit 30 has linearity in the correspondence relationship between the illuminance of the input light of the imaging unit 1 and the output luminance value. That is, it is determined for each imaging system whether the luminance value is included in a range that is a linear function of the illuminance of light (step S23).

At this time, when the exposure time coefficient calculation unit 30 detects that the average brightness value obtained in step S23 is included in the range of the straight line, the process proceeds to step S25, while the average brightness value is a straight line. If it is detected that it is not included in the range, the process proceeds to step S24 (step S23).
Next, the exposure time coefficient calculation unit 30 outputs to the control management unit 11 a detection signal that is detected that the luminance average value is not included in the range of the straight line.
Thereby, the control management unit 11 outputs a control signal for reducing the predetermined exposure time to the imaging control unit 14 of the corresponding imaging unit 1, and reduces the time width that the light receiving unit 15 receives at the sampling timing. The process returns to step S22 (step S24).

Further, the exposure time coefficient calculation unit 30 outputs a detection signal that is detected that the average luminance value is included in the range of the straight line to the control management unit 11.
Thereby, the control management unit 11 stores the currently set exposure time in the database 32 as the base exposure time (α), and advances the process to step S26 (step S25).
Next, the control management unit 11 outputs an instruction to lower the calibration sample 3 to a position where the constituent sample 3 does not come into contact with the movement of the substrate 8 to the sample vertical drive control unit 16 of the holding movement unit 5. (Step S26).
Thereby, the sample up / down drive control unit 16 lowers the calibration sample 3 to a predetermined position.

<Setting of exposure time coefficient>
Next, processing for setting the exposure time coefficient in step S2 will be described below using the flowchart shown in FIG.
The user instructs the control manager 11 how to derive the exposure time coefficient, and the control manager 11 sets the derivation method in the derivation method flag (step S30).
Here, when the flag is a, a = 0 is set when the derivation method is the luminance difference maximum value search, and a = 1 is set when the derivation method is the 3σ search. This difference in derivation method will be described later.

Then, the control management unit 11 reads out the base exposure time from the database 32, sets the “base exposure time” for the imaging control units 14 in all the imaging units 1, and sets all the illumination devices. The dimming control unit 12 is instructed to set the light amount to the value obtained when the base exposure time is obtained (step S31).
Next, the control management unit 11 instructs the sample vertical drive control unit 16 of the holding and moving unit 5 to position the calibration sample 3 in the vertical direction (step S32).
As a result, the sample vertical drive control unit 16 sets the surface of the calibration sample 3 at the same position as the inspection surface of the substrate 8 with respect to the imaging system.

Then, the control management unit 11 sequentially selects a predetermined one from each imaging unit 1 (step S33).
At this time, assuming that there are n imaging units 1 and the number of the imaging unit 1 is k, the control management unit 11 performs imaging in the order of k = 1, 2, 3,..., N−1, n. Initialization is performed with k = 1 so that part 1 is selected.
Next, the control management unit 11 outputs a control signal to the imaging control unit 14 of the imaging unit 1 of the k-th car so that the surface of the calibration sample 3 is imaged (step S34).

Then, the control management unit 11 instructs the image data processing unit 10 to calculate the average luminance value of the reflected light that is reflected from the calibration sample 3 and input to the imaging unit 1 of the k-th machine (step). S35).
Thereby, the exposure time coefficient calculation unit 30 calculates the average value of the luminance of light received by all the light receiving elements of the CCD included in the imaging unit 1 for the imaging unit 1 of the k-th car.
Next, the exposure time coefficient calculation unit 30 outputs the luminance average value obtained for each imaging unit 1 as the illuminance of the input light of the imaging unit 1. It is determined for each imaging system whether the correspondence with the luminance value has linearity, that is, whether the luminance value is included in a range that is a linear function of the illuminance of light (step S36).

At this time, if the exposure time coefficient calculation unit 30 detects that the average brightness value obtained in step S36 is included in the range of the straight line, the process proceeds to step S38, while the average brightness value is a straight line. If it is detected that it is not included in the range, the process proceeds to step S37 (step S36).
Next, the exposure time coefficient calculation unit 30 outputs to the control management unit 11 a detection signal that is detected that the luminance average value is not included in the range of the straight line.
Thereby, the control management unit 11 outputs a control signal for reducing the predetermined exposure time to the imaging control unit 14 of the corresponding imaging unit 1, and reduces the time width that the light receiving unit 15 receives at the sampling timing. The process returns to step S34 (step S37).

Further, the exposure time coefficient calculation unit 30 outputs a detection signal that is detected that the average luminance value is included in the range of the straight line to the control management unit 11.
Thereby, the control management unit 11 outputs a control signal to the imaging control unit 14 so as to fix the current setting as the reference exposure time, and the exposure time coefficient calculation unit 30 adds 1 to k (k The process proceeds to step S39 (step S38).
Next, the exposure time coefficient calculation unit 30 compares k and n, and when it is detected that “k ≦ n (k is n or less)”, the process returns to step S34, where “k> n (k is If it is detected that the value is less than n), the process proceeds to step S40 (step S39).
That is, the exposure time coefficient calculation unit 30 repeats the processing from step S34 to step S39 until the adjustment of the exposure time of all the imaging units 1 is completed.

Then, the control management unit 11 outputs an instruction to lower the calibration sample 3 to a position where the constituent sample 3 does not come into contact with the movement of the substrate 8 to the sample vertical drive control unit 16 of the holding movement unit 5. (Step S40).
Thereby, the sample up / down drive control unit 16 lowers the calibration sample 3 to a predetermined position.
Next, the control management unit 11 instructs the image processing unit 10 to calculate an average luminance value, a luminance difference, and 3σ with respect to the luminance value output by each light receiving element for each imaging unit 1. (Step S41).

Then, the control management unit 11 detects whether the flag a is “1” or “0”, and when detecting that a ≠ 0 (that is, a = 1), the control management unit 11 performs steps S43 to S48. On the other hand, if it is detected that a = 0, the processing from step S50 to step S55 is executed.
Next, when “a = 1”, the control management unit 11 outputs a control signal instructing the image data processing unit 10 to derive the exposure time coefficient using 3σ of the luminance value ( Step S43).

Thereby, the exposure time coefficient calculation unit 30 searches for 3σ of all the imaging units 1 and detects the largest 3σ (the maximum value of 3σ) among the searched.
Then, the exposure time coefficient calculation unit 30 initializes k = 1 and advances the process to step S45 (step S44).
Next, the exposure time coefficient calculation unit 30 divides “the luminance average value of the k-th unit” by “the result obtained by subtracting the maximum value of 3σ from the number of bits of the imaging unit 1 (the threshold value)”. When the value of this division result is γ, the ratio of the changed new exposure time H to the base exposure time α is multiplied by γ, and the exposure time coefficient “γ” corresponding to the k-th unit of the imaging unit 1 is multiplied. XH / α "is calculated. This exposure time coefficient is stored in the database 32 in association with the k-th car (step S46).

Then, the exposure time coefficient calculation unit 30 adds 1 to k and advances the process to step S48 (step S47).
Next, the exposure time coefficient calculation unit 30 compares k and n, and if it is detected that “k ≦ n (k is n or less)”, the process returns to step S45, where “k> n (k is If it is detected that the value is less than n), the process is terminated (step S48).
That is, the exposure time coefficient calculation unit 30 repeats the processing from step S45 to step S48 until the calculation of the exposure time coefficient of all the imaging units 1 is completed.

On the other hand, if “a = 0”, the control management unit 11 outputs a control signal instructing the image data processing unit 10 to derive the exposure time coefficient using the maximum luminance difference (Step S1). S50).
As a result, the exposure time coefficient calculation unit 30 searches for the maximum luminance difference value of all the imaging units 1 and detects the largest luminance difference among the searched values as the maximum luminance difference value.
Then, the exposure time coefficient calculation unit 30 initializes k = 1 and advances the process to step S52 (step S51).
Next, the exposure time coefficient calculation unit 30 divides “the luminance average value of the k-th unit” by “the result of subtracting the maximum luminance value from the number of bits of the imaging unit 1 (the threshold value)”. When the value of this division result is γ, the ratio of the changed new exposure time H to the base exposure time α is multiplied by γ, and the exposure time coefficient “γ” corresponding to the k-th unit of the imaging unit 1 is multiplied. XH / α "is calculated. This exposure time coefficient is stored in the database 32 in association with the k-th car (step S52).

Then, the exposure time coefficient calculation unit 30 adds 1 to k and advances the process to step S55 (step S54).
Next, the exposure time coefficient calculation unit 30 compares k and n, and if it is detected that “k ≦ n (k is n or less)”, the process returns to step S52, where “k> n (k is If it is detected that it is less than n), the process is terminated (step S55).
That is, the exposure time coefficient calculation unit 30 repeats the processing from step S52 to step S55 until the calculation of the exposure time coefficient of all the imaging units 1 is completed.

<Setting of standard exposure coefficient>
Next, the reference exposure coefficient setting process in step S3 will be described with reference to the flowchart shown in FIG.
The number of the imaging unit 1 used when the user calculates the reference exposure coefficient is input to the control management unit 11 as k number (1 ≦ k ≦ n) (step S61).
Then, the control management unit 11 instructs the image data processing unit 10 to set the imaging exposure time of the imaging unit 1 to the imaging control unit 14.
As a result, the exposure time calculation unit 31 reads the exposure time coefficient γ and the base exposure time α corresponding to the No. k machine from the database 32, and multiplies the exposure time coefficient by the base exposure time. The multiplication result is used as the imaging exposure time, overwriting the exposure time stored in the imaging control unit 14 to obtain a new exposure time (step S62).

In order for the user to calculate the reference exposure time of the substrate for each layer, the evaluation layer substrate (substrate 8) is placed on the stage 6 (step S63).
Then, when the user inputs an instruction to start the preparation process to the integrated control unit 4, the control management unit 11 outputs a signal instructing the clamp of the evaluation layer substrate to the clamp control unit 19. The substrate clamp unit 21 clamps the evaluation layer substrate on the stage 6 (step S64).
Here, the term “clamp” means that the substrate clamping unit 21 is brought into a vacuum state by a vacuum suction machine, and the evaluation layer substrate is sucked and fixed to the substrate clamping unit 21.

Then, the control management unit 11 outputs a signal for instructing the transport control unit 18 to move to a position where it can be imaged by the imaging system (step S65).
Thereby, the conveyance control unit 18 drives the conveyance unit 20 to move the evaluation layer substrate 8 to a position where the imaging system can capture an image.
This position is a place where a characteristic point on the evaluation layer substrate 8, that is, a portion where the presence or absence of a defect is to be detected is imaged by the imaging system.

Next, the control management unit 11 outputs an imaging instruction for the evaluation layer substrate to the imaging control unit 14 (step S66), and the brightness difference when a plurality of feature points are captured to the image data processing unit 10 is obtained. An instruction is given to calculate the average value (step S67).
Thereby, the exposure time coefficient calculation unit 30 calculates the average value of the luminance difference of the light received by all the light receiving elements of the CCD included in the imaging unit 1.

Then, the exposure time coefficient calculation unit 30 determines whether or not the luminance difference average value obtained for the imaging unit 1 is included within a specified range (step S68).
Here, the upper limit within the range is set as a threshold value in the claims, and the lower limit of the range also exists as the lower threshold value. However, since the exposure time is set based on the above threshold value, the lower threshold value is not considered.

Here, the luminance difference average value will be described. In the imaging unit 1, the difference between the maximum value and the minimum value is obtained in the luminance value of the feature point obtained from the light receiving element, and this difference is set as the luminance difference.
To explain with a specific example, first, as shown in FIG. 11, a layer board for evaluation is prepared, and the sampled measurement points obtained by taking an image of the board are made a histogram of the appearance frequency for each luminance value (FIG. 12). .
Next, when there are two points of interest in the layer (points A and B in FIG. 11), it is grasped where the points A and B belong to in the histogram.
The difference between the peak values of the peaks of the histogram to which the points A and B belong is obtained, and this is used as the luminance difference.
A single layer is imaged a plurality of times, and the average of the obtained luminance differences is taken as the luminance difference average value.

The prescribed range of the luminance difference average value will be described. Here, when the brightness of the bright part of point B in FIG. 12 is IB and the brightness of the dark part of point A is IA, the contrast C is C = (IB−IA) / (IB + IA)
It is represented by
Since the contrast of the evaluation layer substrate is constant, as IA increases, IB increases, and the brightness difference average value, which is the difference, also increases.
Therefore, the longer the exposure time and the brighter, the higher the accuracy of identifying points A and B.
However, the luminance output with respect to the amount of light to which IB is input needs to be in a linear range.
Therefore, the specified range is determined as appropriate so that the brightness of the bright portion of each substrate does not exceed the upper threshold value and the necessary identification accuracy is obtained.

If the exposure time coefficient calculation unit 30 detects that the average brightness difference value is included in the specified range (does not exceed the threshold value), the process proceeds to step S70. If it is detected that the value is not included in the range of the straight line (exceeds the threshold value), the process proceeds to step S69 (step S68).
Next, the exposure time coefficient calculation unit 30 outputs to the control management unit 11 a detection signal that is detected that the luminance average value is not included in the range of the straight line.
As a result, the control management unit 11 outputs a control signal for decreasing the predetermined exposure time to the imaging control unit 14 of the corresponding imaging unit 1, increases or decreases the exposure time of the light receiving unit 15, and performs processing. Return to S65 (step S69).

In addition, the exposure time coefficient calculation unit 30 outputs a detection signal that is detected that the average luminance difference value is included in the specified range to the control management unit 11.
As a result, the control management unit 11 instructs the transfer control unit 1 to move the transfer unit 20, and retracts the evaluation layer substrate on the stage 6 from the position where the calibration sample 3 is moved up and down by the holding and moving unit 5. Then, the process proceeds to step S71 (step S70).
Then, the exposure time coefficient calculation unit 30 divides the “exposure time in the imaging unit 1 at the time of step S70” by “the result of multiplying the reference exposure time and the exposure time coefficient corresponding to the k-th unit”. The division result is used as a reference exposure coefficient for the evaluation layer, and is stored in the database 32 corresponding to the layer information (for example, the layer number) of the evaluation layer substrate (step S71).

Next, the above-described processing is repeated to obtain a reference exposure coefficient corresponding to each of all necessary evaluation layer substrates.
As described above, when the pre-measurement preparation flow shown in FIG. 4 is completed, the reference exposure coefficient j corresponding to each of the layers (evaluation layer substrates) shown in FIG. 8 and the exposure time corresponding to each of the imaging units 1. A table with the coefficient i is formed, and the exposure time calculation unit 31 calculates in advance a value of i × j corresponding to the combination of the imaging unit 1 and the layer (substrate 8), and uses this as the base exposure time. By multiplying, the imaging exposure time for each imaging unit 1 can be calculated at high speed.

<Measurement execution process>
Next, the processing from step S4 to step S8 is performed as the inspection measurement in the order shown in the flowchart of FIG.
The layer information (for example, the layer number) of the substrate 8 to be inspected is acquired from the server that performs inspection management of the inspection apparatus (step S4).
Then, the exposure time calculation unit 31 of the image data processing unit 10 reads the reference exposure coefficient corresponding to the substrate 8 from the database 32 from the layer information, and sets the base exposure time for each imaging unit 1. On the other hand, the imaging exposure time is obtained by multiplying the reference exposure time and the exposure time coefficient corresponding to each imaging unit 1 read from the database 32, and the imaging unit 1 corresponding to the imaging exposure time obtained for each imaging unit 1 is obtained. Is set in the imaging control unit 14 (step S5).

  Next, the control management unit 11 moves all the imaging substrates at predetermined intervals (sampling timing) while moving the substrate 8 to be inspected by the plurality of imaging systems to the predetermined speed by the transport control unit 18. The imaging control unit 14 of the unit 1 is instructed to perform imaging, and the imaging control unit 14 of each imaging unit 1 turns on the light receiving element of the light receiving unit 15 of the imaging unit 1 during the set imaging exposure time. The luminance value for each light receiving element is measured and temporarily stored in the line memory in the image data processing unit 10 (step S6).

Then, the image data processing unit 10 changes significantly compared to the luminance value of the previous cycle stored in the line memory and the luminance value currently received by the light receiving unit 15 for each light receiving element. The part which is doing is extracted as a defect candidate (step S7).
Next, the image data processing unit 10 includes layer information of the substrate 8, coordinate values on the substrate 8 (specified by the number of samplings in the time direction, and the position of the light receiving element of the light receiving unit 15 of the imaging unit 1), and the defect The size (specified in the range of the coordinate values) is output (step S8).

Next, the process of step S5 for calculating the exposure time of the imaging unit 1 in the flowchart of FIG. 9 will be described in detail with reference to the flowchart of FIG.
The control management unit 11 initializes the camera number of the imaging unit 1 as k = 1 (1 ≦ k ≦ n) to k = 1 (step S80).
Then, the control management unit 11 instructs the image data processing unit 10 to set the imaging exposure time of the imaging unit 1 to the imaging control unit 14.
Thereby, the exposure time calculation unit 31 reads the exposure time coefficient corresponding to the k-th machine and the reference exposure coefficient corresponding to the layer information of the substrate 8 from the database 32, and uses the exposure time coefficient and the reference exposure coefficient as the base. And the multiplication result is set as the imaging exposure time in the imaging control unit 14 (step S81).

Next, the exposure time coefficient calculation unit 30 adds 1 to k and advances the process to step S83 (step S82).
Next, the exposure time coefficient calculation unit 30 compares k and n, and if it is detected that “k ≦ n (k is n or less)”, the process returns to step S81, where “k> n (k is If it is detected that the value is less than n), the process is terminated (step S83).
That is, the exposure time coefficient calculation unit 30 repeats the processing from step S81 to step S83 until the calculation of the imaging exposure time of all the imaging units 1 is completed.

Next, as another example, the configuration is the same as that of the embodiment shown in FIGS. 1 to 3, but as shown in FIG. 13, a new time is added between step S <b> 36 and step S <b> 38 in the flowchart of FIG. 6. The operation provided with steps S56 and S57 as processing will be described only for the operation different from the embodiment described above.
After the process of step S35, the exposure time coefficient calculation unit 30 calculates the luminance average value obtained for each imaging unit 1 as the rough adjustment of the luminance value, and the illuminance and output of the input light that the imaging unit 1 has. For each imaging system, it is determined whether or not each imaging system has a linearity, that is, whether the average luminance value is included in the first specified range that is a linear function of the illuminance of light. This is performed (step S56).

At this time, if the exposure time coefficient calculation unit 30 detects that the luminance average value obtained in step S56 is included in the first specified range, the process proceeds to step S36, while the luminance average value Is detected not to be included in the first range, the process proceeds to step S57 (step S56).
Next, the exposure time coefficient calculation unit 30 outputs to the dimming control unit 12 a detection signal that is detected that the luminance average value is not included in the first specified range.
Thereby, the dimming control unit 12 adjusts the voltage applied to the light emitting unit 13 corresponding to the corresponding imaging unit 1 (lower if the luminance value is higher and higher if the luminance value is lower), and returns the process to step S34. (Step S57).

  After the rough adjustment of the luminance value in step S56, the exposure time coefficient calculation unit 30 inputs the light average value obtained for each image pickup unit 1 as the fine adjustment of the luminance value that the image pickup unit 1 has. In the correspondence relationship between the illuminance of the image and the output luminance value, it is determined whether each image has linearity, that is, whether the average luminance value is included in the second specified range in the linear function of the illuminance of light. This is performed for each system (step S36).

At this time, if the exposure time coefficient calculation unit 30 detects that the luminance average value obtained in step S36 is included in the second specified range, the process proceeds to step S38, while the luminance average value Is not included in the second specified range, the process proceeds to step S37 (step S36).
Next, the exposure time coefficient calculation unit 30 outputs a detection signal, which is detected that the luminance average value is not included in the second specified range, to the control management unit 11.
Thereby, the control management unit 11 outputs a control signal for reducing the predetermined exposure time to the imaging control unit 14 of the corresponding imaging unit 1, and reduces the time width that the light receiving unit 15 receives at the sampling timing. The process returns to step S34 (step S37).

In the other embodiments described above, the first prescribed range of the luminance average value is set wider than the second prescribed range. Also, the adjustment range of the average luminance value is set to be wide at the time of coarse adjustment and narrow at the time of fine adjustment.
That is, the exposure time variable step amount of the imaging control unit 14 can be set more finely than the light adjustment step amount of the dimming control unit 12.
By controlling the luminance value by changing the voltage applied to the light emitting unit 13 described above, the light emitting unit 13 deteriorates due to long-time operation of the lighting device 2, and the light quantity of the light emitting unit 13 varies greatly for each channel. There is an effect that the brightness value can be adjusted when the difference in brightness cannot be obtained only by controlling the exposure time of the imaging control unit 14.

In the inspection apparatus described above, the description is made assuming that there is one type of layer substrate. However, in order to improve the operation efficiency of the manufacturing apparatus for production in the factory, as shown in FIG. A plurality of types of layer substrates are manufactured on the substrate simultaneously (manufactured as a take-up substrate).
At this time, coordinate information indicating the switching position of the type of the board to be inspected on the substrate to be taken is indicated from the server, and the control management unit 11 is the coordinate information measured by itself (for example, the traveling direction of the board). The coordinate information of the switching position (the switching position from the layer board area A to the layer board area B) input from the server matches the one-dimensional coordinate value obtained from the moving speed and moving time in the x-axis direction. This is detected, the reference exposure coefficient is read from the database 32 based on the layer information transmitted together with the coordinate information, and the imaging exposure time is calculated.

  Further, in the configuration described above, a reference exposure count for each layer substrate is used for an inspection apparatus for a substrate on which an imaging device using only one imaging system, that is, only one combination of the imaging unit 1 and the illumination device 2 is mounted. Even if these are used in a database, the inspection efficiency can be improved.

  The program for realizing the function of the image pickup apparatus in FIG. 1 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into the computer system and executed to adjust the brightness. Processing may be performed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system provided with a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and a storage device such as a hard disk built in the computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

It is a conceptual diagram which shows the structure of the inspection apparatus of the board | substrate which mounts the imaging device of one Embodiment of this invention. It is a block diagram which shows the structural example of the test | inspection apparatus of FIG. It is a block diagram which shows the structural example in the present Example of the image data processing part 10 of FIG. It is a flowchart which shows an example of the process of the measurement preparation in the inspection apparatus of FIG. FIG. 5 is a flowchart illustrating in detail a process in step S1 of FIG. 5 is a flowchart illustrating in detail the process of step S2 of FIG. FIG. 5 is a flowchart illustrating in detail a process in step S3 of FIG. 3 is a conceptual diagram illustrating a configuration of a table in a database 32. FIG. It is a flowchart which shows an example of the measurement process of the inspection apparatus of FIG. 10 is a flowchart illustrating in detail the process in step S5 of FIG. It is a conceptual diagram explaining the process which calculates | requires the reference | standard exposure coefficient for every layer board | substrate. It is a hiss and a gram which show appearance frequency for every luminance value of a measurement point when a layer board is imaged. It is the flowchart in other embodiment which demonstrated the process of FIG.4 S2 in detail. It is a conceptual diagram explaining the process which calculates | requires the reference | standard exposure coefficient for every layer board | substrate area | region of a different kind in a prepared substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Imaging part 2 ... Illuminating device 3 ... Calibration sample 4 ... Integrated control part 5 ... Holding movement part 6 ... Stage 7 ... Substrate conveyance part 8 ... Substrate 10 ... Image data processing part 11 ... Control management part 12 ... Light control Unit 13 ... Light emitting unit 14 ... Imaging control unit 15 ... Light receiving unit 16 ... Sample vertical drive control unit 18 ... Transport control unit 19 ... Clamp control unit 20 ... Transport unit 21 ... Substrate clamp unit 30 ... Exposure time coefficient calculation unit 31 ... Exposure Time calculator 32 ... Database

Claims (11)

In an imaging device comprising a plurality of imaging systems each having an imaging unit,
An exposure time coefficient calculation unit that reads luminance information of images corresponding to the exposure time of all imaging units, and calculates an exposure time coefficient for each imaging unit from the luminance information;
An imaging apparatus comprising: an exposure time calculation unit that calculates an imaging exposure time used for imaging of each imaging unit by multiplying a predetermined exposure time by an exposure time coefficient corresponding to each imaging unit. The imaging device has an illumination device corresponding to each imaging unit,
A luminance measurement unit that measures luminance information received by all pixels for each imaging unit, using a calibration sample;
The imaging apparatus according to claim 1, further comprising: a dimming control unit that adjusts a light amount of the illumination apparatus with respect to the predetermined exposure time so that the maximum value of the luminance becomes a predetermined threshold value. .   The threshold value is a maximum value in a range where the brightness value is a linear function of brightness in the correspondence relationship between the brightness received by the light receiving unit of the imaging unit and the output brightness value at a predetermined exposure time, and all The imaging device according to claim 2, wherein the imaging device is set to the smallest value.   The exposure time coefficient calculation unit obtains the average value and 3σ of luminance information for each imaging unit, subtracts the maximum 3σ in each imaging unit from the threshold value, and divides the average value of each imaging unit by the subtraction result The imaging apparatus according to claim 1, wherein the result is output as an exposure time coefficient.   The exposure time coefficient calculation unit obtains the luminance difference between the average value and the maximum value and the minimum value of the luminance information for each imaging unit, and subtracts the maximum luminance difference in each imaging unit from the threshold value, and the subtraction result The imaging apparatus according to claim 1, wherein a result obtained by dividing the average value of each imaging unit is output as an exposure time coefficient.   2. A database in which a reference exposure coefficient for adjusting a predetermined exposure time is stored for each imaging unit in correspondence with an object to be imaged by an imaging device. The imaging device according to any one of 5.   The exposure time calculation unit reads out a reference exposure coefficient corresponding to the imaging target from the database corresponding to each imaging unit, and multiplies the exposure time multiplied by the exposure time coefficient to obtain the imaging exposure time of each imaging unit. The imaging apparatus according to claim 6, wherein: In an imaging method in an imaging device including a plurality of imaging systems each having an imaging unit,
Reading the luminance information of the image corresponding to the exposure time of all the imaging units, and calculating the exposure time coefficient for each imaging unit from the luminance information,
An imaging method comprising: calculating an imaging exposure time used for imaging of each imaging unit by multiplying a predetermined exposure time by an exposure time coefficient corresponding to each imaging unit. Luminance measurement process for measuring luminance information of all pixels for each imaging unit by using a calibration sample;
And a dimming control process for adjusting a light amount of an illuminating device corresponding to each imaging unit with respect to the predetermined exposure time so that the maximum value of the luminance becomes a predetermined threshold. The imaging method according to 8.   In the exposure time coefficient calculation process, the average value and 3σ of the luminance information for each imaging unit are obtained, the maximum 3σ in each imaging unit is subtracted from the threshold value, and the average value of each imaging unit is divided by the subtraction result. The imaging method according to claim 8 or 9, wherein the obtained result is output as an exposure time coefficient. In the exposure time coefficient calculation process, a luminance difference between an average value of luminance information for each imaging unit and a maximum value and a minimum value is obtained, and the maximum luminance difference in each imaging unit is subtracted from the threshold value. The imaging method according to claim 8 or 9, wherein a result obtained by dividing an average value of each imaging unit by the result is output as an exposure time coefficient.

Images