JPH11248423A - Method and apparatus for measuring height - Google Patents

Abstract

PROBLEM TO BE SOLVED: To greatly improve the cycle time to enable the accurate height measurement, by obtaining the height of a protrusion from a taken image of the protrusion, differentiating it to extract height data of a flat part from the differentiated value. SOLUTION: An object to be measured is made to be a printed cream solder on a wiring board. A laser light from a laser diode 1 is collimated by a collimating lens 2 into a parallel beams 1a, restricted by a focus lens 3 into a spot beam, reflected at 45 deg. to the incident angle by a projection mirror 4, and drawn in one direction by a line generator 5 into a line beam of 14 μm wide, 10 mm long on the object 11 which is then photographed by a CCD camera 6, variously processed image data is sent to a center of gravity position processing block to compute the center of gravitational value and stored in a memory as a height data, the read height data is differentiated to obtain the height of a flat part and the cream solder height is obtd. from the flat part as a reference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a height measuring method and apparatus, and more particularly, to a height measuring minute height such as cream solder printed by a cream solder printing machine used in a surface mounting system. The present invention relates to a measuring method and an apparatus.

[0002]

2. Description of the Related Art Conventionally, as a device for recognizing a three-dimensional shape and measuring a height, a three-dimensional recognition device using a light section method has been known. Fig. 2 shows a three-dimensional recognition device using this light section method
0 is shown. Line light 122 from a line light generator 121, which is a light source, is projected at a predetermined angle from obliquely above the DUT 123, and an image formed along the surface shape formed on the surface of the DUT 123 is vertical. Photographed by the CCD camera 124 from above. The image taken by the CCD camera 124 is CC
The data is A / D converted by the D camera controller 125 and captured by the image capturing unit 126. Then, the captured data is converted into three-dimensional coordinates of the device 123 by the coordinate calculator 127.

[0003] In a cream solder height measuring device used in a cream solder printing machine, a portion (measurement unit) 128 surrounded by a dotted line in FIG. 20 is built in an XY moving gantry (XY moving mechanism). Used. First, when the wiring board for printing is carried into the cream solder printing machine, after the positioning of the wiring board and the stencil is completed,
The measurement unit 128 is moved by the XY moving gantry from the initial expected evacuation position to the target measurement position. Then, the measurement unit converts the image of the line light formed on the pad surface (resist surface) on the wiring substrate, which is the object to be measured, into CC.
After the image is taken by the D camera 124, it is moved and evacuated again to the first expected evacuation position. Next, cream solder is printed on the pad surface of the wiring board. After the printing on the pad surface of the wiring board is completed, the measuring unit 128 is again moved to the target measuring position by the XY moving gantry, and the image of the line light formed along the shape of the cream solder is transferred to the CCD camera 124. And then re-evacuate to the first expected escape position again.

From the above image data, the coordinates of the center of gravity of the pad surface of the wiring board in the height direction and the coordinates of the center of gravity of the cream solder portion in the height direction are calculated. Then, the subtraction between the coordinates of the center of gravity of the pad surface of the wiring board in the height direction and the coordinates of the center of gravity of the cream solder portion in the height direction is used to calculate the height of the cream solder portion after printing with reference to the pad surface of the wiring board. calculate. Then, the average height of the cream solder portion over each pad surface is calculated.

[0005] In order to obtain a three-dimensional shape, a plurality of data at different light-cut positions are required. For example, the length is 2mm
It is assumed that light cutting is performed at a pitch of 50 μm in order to obtain a three-dimensional shape of the cream solder printed on the pad. In this case, before printing the cream solder, the image of the line light formed on the pad surface of the wiring board is imaged 40 times by the CCD camera while changing the light cutting position. Further, after printing the cream solder, it is necessary to image the line light image formed along the shape of the cream solder 40 times while changing the light cutting position by the CCD camera. Therefore, CCD
The total number of times of imaging by the camera is 80 times. Similarly,
The total number of minute movements of the measurement unit is also 80.

[0006]

However, in a cream solder height measuring device that is used by being incorporated in a conventional cream solder printing machine, an image of a line light before printing and an image of a line light after printing are used. Must be imaged with a CCD camera to calculate the height of the cream solder. For this reason, there has been a problem that the tact time is lengthened and the performance of the entire semiconductor surface mounting system is reduced.

In addition, a heavy measuring unit equipped with a CCD camera must be moved to minutely change the position of light cutting. For an XY moving gantry, a skip function to a target measuring position is provided. In addition, there is a problem that the servo system for driving the XY movement gantry must be provided with two functions, that is, a minute movement at a measurement target position.

Accordingly, the present invention has been made in order to solve such a problem, and provides a height measuring method and apparatus capable of significantly improving the tact time and accurately measuring the height. Is the task.

[0009]

According to the present invention, in order to solve this problem, a line light is projected onto an object to be measured having a projection projecting from the flat portion, and a flat portion cut by the line light and In the height measurement method of measuring the height of the protrusion from the flat portion by imaging the protrusion and measuring the height of the protrusion from the flat portion, obtaining the height data of the protrusion from the image of the captured protrusion, the height data A configuration is employed in which primary differentiation and secondary differentiation or primary differentiation are performed, and height data of a flat portion is extracted from the differential value.

Further, in the present invention, a line light is projected onto an object to be measured having a protrusion projecting from the flat portion, the flat portion cut off by the line light and the protrusion are imaged, and the flat portion is cut by a light cutting method. In a height measuring device that measures the height of the protrusion from the, a light projection device that emits line light to the protrusion,
Means for capturing an image of the projecting object on which the line light is projected, means for processing image data of the projecting object by the line light to calculate height data of the projecting object, and a first derivative of the height data Means for calculating the height of the flat part from the differential value, and means for calculating the height of the flat part from the differentiated value, and means for calculating the height of the protrusion based on the height of the flat part. Has also been adopted.

In such a configuration, the height data of the flat portion of the object to be measured is obtained from the first derivative and the second derivative or the first derivative of the height data obtained by processing the image data of the object to be measured. Since the height data of the protrusion is calculated based on the height of the flat portion, there is no need to obtain the height data of the flat portion before the protrusion is formed, and the protrusion is formed on the flat portion. When the height of the protrusion must be measured every time, for example, cream solder is printed on the wiring board, and when the height of the cream solder must be measured, the tact time is significantly improved. be able to.

In the present invention, at the rising portion of the projecting portion,
Although it is based on the idea that the differential value increases, there is another problem that the differential value increases. This problem is solved by examining the flatness near the extracted height data and using the extracted height data as the height data of the flat portion if the flatness is not flatter than a predetermined value.

Also, the differential value may increase during the rising of the protruding portion. However, this problem is caused by the fact that when the height data is extracted, the flat portion is already selected from the plurality of height data before that. When the height data is adopted, the problem is solved by discarding the extracted height data.

Further, when the object to be measured has a warp in the direction along the line light of the object to be measured, accurate measurement cannot be performed. The problem is solved by obtaining an approximate expression of the height data of the flat portion using multiple linear regression based on the height data of the flat portion, and correcting the inclination in the direction along the line light of the flat portion from the approximate expression.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

[Basic Configuration] FIG. 1 is a basic configuration diagram of main optical components of a three-dimensional measuring apparatus showing an embodiment of the present invention, and FIG. 2 is a side view thereof. In each figure, the reference numeral 1 denotes a laser diode as a laser light source.
The laser light emitted from the laser diode 1 is converted by the collimator lens 2 into a parallel light beam 1a parallel to the optical center axis. This laser parallel light beam 1a enters a light projecting unit 7 in which a focus lens 3, a light projecting mirror 4, and a line generator lens 5 are incorporated. The laser beam is narrowed down to a spot light by the focus lens 3 in the light projecting unit 7, reflected by the light projecting mirror 4 at an angle of 45 degrees with respect to the vertical axis (Z direction), and is reflected by the line generator lens 5. 14 to 20 μm in width,
A line light 9 having a length of 10 mm is formed, and the line light 9 is formed in the X direction on the DUT (cream solder or a wiring board on which it is printed) 11.

The scattered reflected light from the DUT 11 is reflected on the optical axis 6.
6.4 mm × 4.8 arranged so that a is the vertical axis
The image is picked up by a non-interlaced CCD camera 6 having a mm visual field. The light projecting unit 7 is attached to a shaft 8a of a linear motor 8, and the linear motor 8 performs a linear motion with a stroke of about 10 mm in the Y direction, so that the linear Luminous flux 1
Reciprocate in parallel with a. The movement of the light projecting unit 7 causes the line light 9 to move in a direction perpendicular to the X direction in which the line light extends.

[Circuit Configuration (Data Acquisition)] FIG. 3 is a block diagram showing a circuit configuration for acquiring image data of an object to be measured in a three-dimensional measuring apparatus. In the figure, a linear motor drive commander 31 receives a start signal from a CPU 44, outputs a linear motor drive command pulse train to a linear motor driver 32, and sets the linear motor 8 to 1
Move 0.25 μm per pulse. The linear motor drive commander 31 simultaneously sends forward / reverse signals to an LD (laser diode) on / CCD trigger timing decoder (hereinafter referred to as a timing decoder) 35, and the linear motor 8 moves in either the forward or reverse direction. Let them know.

The linear motor driver 32 drives the linear motor in response to the command pulse train, and adjusts the supply voltage to the linear motor 8 in response to the signal indicating the actual position from the position encoder 8b built in the linear motor 8. Feedback control of the position of the linear motor.

The position counter 34 has an A-phase signal having a phase difference of 90 degrees by the position encoder 8b of the linear motor 8,
Upon receiving the B-phase signal, a position signal indicating the position of the linear motor 8 is output as digital data. The position counter 34
Is reset by an origin reset signal from the position encoder 8b.

The timing decoder 35 receives the position data from the position counter 34 and outputs an LD-on timing signal (160 μm pitch). In response to the rise of this signal, the one-shot multivibrator (M
S) 46 outputs an LD ON pulse having a width of 2 ms to the laser diode driver 36 to turn on the laser diode 1 in a pulsed manner. The laser diode 1 has a built-in light amount monitor photodiode (not shown), and the light amount of the laser diode 1 is controlled to be constant.

Since the linear motor 8 is moving even while the LD is on, the line light position is deviated depending on the moving direction, and a half pitch (in the embodiment, 80 μm In order to shift, the forward / reverse direction signal is input from the linear motor drive commander 31 as described above.

The position latch 37 latches the position data output from the position counter 34 at the rise of the LD on timing, and synchronizes the position of the line light in the Y direction at that time with the fall timing of the LD on pulse from the MS 46. To the CPU 44. The line light moves while the LD is on, causing a deviation from the actual line light position. This is corrected in the CPU 44 by the line light moving speed, the LD on time, and the forward / reverse signal. I have.

On the other hand, the synchronization signal timing generator 39
C from the timing decoder 35 via the OR circuit 35 '
In response to the CD camera synchronization timing signal, it outputs a VD vertical synchronization signal synchronized with the HD horizontal synchronization signal. In connection with this VD vertical synchronizing signal, reading of light amount data of each pixel of the previous frame is started. At the same time, the accumulation of light quantity in each pixel starts, and the image by the line light 9 is CC
It is acquired on the CCD area image sensor 38 of the D camera 6.

The image on the CCD area image sensor 38 is read out as a light amount value (analog value) of each pixel via a driver 33 by a vertical register transfer clock, a horizontal register transfer clock or the like from a synchronization signal timing generator 39. . This is, via the amplifier 47, the A / D
The data is input to the converter 48 and converted into digital data as VR data.
It is input to the AM image memory 40.

The horizontal address counter 42 is reset after a predetermined number of horizontal clocks from the fall of the horizontal synchronizing signal from the synchronizing signal timing generator 39, and counts the horizontal clocks thereafter to determine the horizontal position of the current pixel in the effective screen. Outputs the direction position (horizontal address). This horizontal address value is supplied to V-
It is input to the horizontal address of the RAM image memory 40.

On the other hand, the vertical address counter 43 is reset after a predetermined number of pulses of the horizontal synchronizing signal from the fall of the vertical synchronizing signal from the synchronizing signal timing generator 39, and thereafter is enabled by counting the pulses of the horizontal synchronizing signal. The vertical position (vertical address) of the current pixel in the screen is output. This vertical address value is input to the vertical address of the V-RAM image memory 40 via the multiplexer 45.

The write timing generator 49 outputs a signal between an effective horizontal scanning section signal from the horizontal address counter 42 and an effective vertical scanning section signal from the vertical address counter 43.
A write signal is output to the V-RAM image memory 40 in synchronization with the horizontal clock. Thereby, the V-RAM image memory 40 stores each pixel data in the effective screen determined by the effective horizontal scanning section signal and the effective vertical scanning section signal.

The horizontal / vertical address generator 50 outputs the horizontal address signal to the multiplexer 41, the vertical address signal to the multiplexer 45, and the read signal to the V-RAM.
Output to the image memory 40. Multiplexers 41, 45
Is switched to the reading side in response to the switching signal from the CPU 44, and the image data of the V-RAM image memory 40 at the address determined by the horizontal address signal and the vertical address signal is sequentially read in synchronization with the reading signal. The reading of the image data is performed after the writing of the image data to the V-RAM image memory 40 is completed. This is because the multiplexer 4 receives a switching signal from the CPU 44.
1, 45 are guaranteed by switching from write to read mode.

[Circuit Configuration (Data Processing)] FIG.
3 illustrates a circuit configuration for processing image data stored in the RAM image memory 40. The circuit configuration centering on the V-RAM image memory 40 is the same as that illustrated in FIG. ing.

The multiplexers 41 and 45 are switched according to the switching signal.
Is switched to readout, the image data read out from the V-RAM image memory 40 in synchronization with the readout signal is input to the gradation data filter processing block 60 to remove noise. The gradation data filter processing block 60 is provided with two one-line buffers 61 and 62, whereby three lines of image data can be obtained simultaneously. These three lines of image data are input to the arithmetic circuit 63, where the flatness F of the image data is calculated, and is also input to the arithmetic circuit 64, where the maximum gradation value MAX and the minimum gradation value MIN are calculated. The difference ΔB is calculated. Further, the image data for three lines is also input to the band elimination filter 68 and is subjected to the band elimination filter. The output of the one-line buffer 61 is input to the delay circuit 69, and a delay corresponding to the operation processing time is applied. The arithmetic circuit 6
3, 64 and the processing of the band elimination filter 68 are 3
The processing is performed in units of × 3 pixel blocks.

The arithmetic circuit 65 calculates the ratio of the flatness F of the image data to the difference ΔB, and the comparator 66 compares the calculation result with a threshold value 66 ′. If it is less than the threshold value, the multiplexer 67 selects the image data that has been subjected to the band elimination filter processing by the band elimination filter 68, and if it is more than the threshold value, the delay circuit 69 applies a delay corresponding to each operation time The selected image data is output to the binarization processing block 70.

In the binarization processing block 70, an average value x (with a bar above) is calculated for each line by the average value calculation circuit 71 for the image data from the gradation data filter processing block 60. The deviation calculation circuit 72 calculates a standard deviation ρ for each line, and the threshold calculation circuit 74 calculates a threshold value (x + 1.5ρ). The comparator 75 is
This threshold value and 1 held in the one-line buffer 73
The image data for the lines is compared, and the image data is binarized.

The binarized image data from the binarization processing block 70 is converted into a binarized data filter processing block 80
Noise removal processing circuit 83 and two one-line buffers 8
1 and 82 are input. Noise removal filter processing circuit 8
3 receives three lines of image data simultaneously from the two one-line buffers 81 and 82 on the input side and the direct image data, and examines each 3 × 3 image block for small projections and isolated data; If so, a process for removing the data is performed. The output of the noise removal processing circuit 83 is
The data is input to the line buffer 85. The judgment circuit 87
It is determined whether all the lines are 0. If all the lines are 0, the output of the OR circuit 88 is selected by the multiplexer 89, and if not, the output of the 1-line buffer 85 is selected.
It is input to the one-line buffer 86. Since the image data of the one-line buffer 85 corresponds to the current image data, and the output of the noise removal processing circuit 83 and the image data of the one-line buffer 86 correspond to the image data before and after that,
If all the lines are 0, image data filled by OR processing of data at the same horizontal position of the previous and next lines is output.

The binarized image data from the binarized data filter processing block 80 is input to a centroid position calculation processing block 90, where the centroid position is calculated for each line. Rise detection circuit 9 of center-of-gravity position calculation processing block 90
1 detects that the binarized image data changes from “0” to “1”, and latches the horizontal address value of the horizontal address counter 93 at that time in the latch circuit 94. Also,
The falling detection circuit 92 detects that the binarized image data changes from “1” to “0”, and latches the horizontal address value of the horizontal address counter 93 at that time in the latch circuit 95. The center-of-gravity position calculating circuit 96 calculates the center-of-gravity position by averaging the horizontal address values at the time of the rise and the time of the fall.
The value is stored in the centroid position calculation result memory 100. The horizontal address counter 93 counts a horizontal clock for reading from the V-RAM image memory in order to obtain a horizontal address value. The horizontal address counter 93 is reset at the time of switching one line of image data.

[Measurement of Height Data] Next, in such a configuration, a process of obtaining height data of the wiring board or the cream solder is described with reference to an example in which the object to be measured is cream solder printed on the wiring board. A description will be given with reference to the flow of FIG.

First, after it is confirmed in step S40 that the cream solder has been printed, in step S41, the CPU 44 generates a position command signal and a start signal to the linear motor drive commander 31, and causes the linear motor 8 to Is moved to the height measurement position where is printed.
When the actual height measurement position is reached, a CCD camera synchronization timing pulse is sent from the CPU 44 via the OR circuit 35 '(step S42), and an LD ON signal is generated to turn on the laser diode 1, for example, for 2 ms (step S42). Step S43).

The laser light emitted from the laser diode 1 is condensed by a collimator lens 2 to form a parallel light beam 1a parallel to the optical center axis.
Is narrowed down to a spot light. This laser spot light is reflected by the light projecting mirror 4 in the direction of 45 degrees with respect to the incident angle, and
Incident on. With this lens 5, the laser spot light is
The light is expanded in one direction (X direction) by the prism effect, and becomes a line light 9 having a width of 14 μm and a length of 10 mm on the DUT 11. This line light has a field of view of 6.4 mm × 4.
The image is picked up by a non-interlaced CCD camera 6 of 8 mm.

After waiting for the time T1 in step S44,
In step S45, a CCD camera synchronization timing pulse is sent, and the synchronization signal timing generator 39 is driven to drive the CCD camera.
The image data of the image sensor 38 of the camera 6 is read into the V-RAM image memory 40 in synchronization with the output of the write timing generator 49 (step S46). FIG. 6 shows the image data acquired in this way. In the figure, the image of high brightness protruding to the right is the cream solder portion 113a, and the straight line portion of low brightness therebetween is the resist surface or pad surface 113b of the wiring board.

This image data undergoes each image processing in step S47. First, the multiplexers 41 and 45 are switched to the read mode by the switching signal of the CPU 44, and V is synchronized with the horizontal address and the vertical address according to the read signal from the horizontal / vertical address generator 50.
Image data is read from the RAM image memory 40;

The read image data is subjected to gradation data filtering in a gradation data filtering block 60. The arithmetic circuit 63 sets the pixel at the center of each 3 × 3 pixel block as the pixel of interest, and sets the flatness F
Is calculated. The flatness F is obtained as an average value of absolute values of differences between pixels around the target pixel, and the pixel columns are represented by A, B, and C.
.., The pixel rows are 1, 2, 3,...

[0042]

(Equation 1)

The flatness F is calculated by calculating The arithmetic circuit 64 calculates the difference ΔB between the maximum value of the pixels of each 3 × 3 pixel block and the minimum value of the gradation, and the arithmetic circuit 65 calculates F / ΔB. When F / ΔB is smaller than the threshold value 66 ′, the comparator 66 switches the multiplexer 67 because the image data is not flat. As a result, the band elimination filter circuit 68

[0044]

(Equation 2)

The data subjected to the band elimination filter processing is output. On the other hand, when ΔB = 0 or F / ΔB is larger than the threshold value, the data from delay circuit 69 is selected and band elimination filter processing is not performed. Data is output.

The image data that has been subjected to the gradation data filter processing is binarized by a binarization processing block 70. For this purpose, the arithmetic circuits 71 and 72 calculate the average value x (with a bar above) and the standard deviation ρ of the gradation of each line. The comparator 75 sets the current pixel value to 1 when the gradation data of the pixel is greater than the average value x + ρ × 1.5 of the gradation of each line for each pixel of the one-line buffer 73.
In the following cases, the current pixel value is set to 0 and binarized.

Each of the binarized image data is sent to a binarized data filter processing block 80, and a noise removal processing circuit 83 removes small projection data and isolated data as noise for each 3 × 3 pixel block. I do. This noise removal corresponds to performing the filtering processes a to f as shown in FIG. When the pattern of FIG. 7 appears with the pixel at the center of 3 × 3 as the target pixel, the value of the target pixel is set to 0. The five types of filters other than f are rotated by 90 degrees and executed. The binarized image data thus subjected to the noise processing is sent to the one-line buffers 85 and 86. When all the pixels in one line are 0, the determination circuit 87 performs padding with reference to the preceding and following lines. For example, if all the pixels on the second line are 0, and if there is one pixel on the preceding and succeeding lines (first and third lines), the location of the one pixel is set to one.

The image data processed in this manner is sent to the center-of-gravity position calculation processing block 90, and the calculation circuit 96 calculates the center-of-gravity position (average value). This position of the center of gravity is shown in FIG.
As shown in FIG. 1, 1 for pixel rows A, B, C.
This is performed by assigning serial numbers such as 2, 3,. In this example, regarding the first and second rows, the values of the pixels in the I and J columns are 1, and the number of the I column is 9 and the number of the J column is 10, so the centroid value of the first and second rows is 9. It becomes 5. Also 3,
For the fourth and fifth rows, the pixels in the I, H, and G columns are 1, and the barycentric value of each row is 9, which is the same as the number assigned to each column.
8 and 7. Hereinafter, the barycenter value of each row is obtained in the same manner.

FIG. 8 shows a graph in which the vertical axis is the barycentric value and the horizontal axis is the line number. This result is stored in the memory 100 as height data in step S48.

Next, the height data of FIG. 8 is read out from the memory 100 and differentiated to obtain the height of the flat portion (resist surface), and the height of the cream solder with reference to this flat portion is obtained.

FIG. 9A is a graph of the first derivative of the height data of FIG. 8, and FIG. 9B is a graph of a second derivative obtained by further differentiating the first derivative. Differentiation is performed from the left. Therefore, FIG.
Is scanned from left to right, the upward projection is the rising portion of the cream solder portion, and the downward projection is the falling portion. Since the protrusion level at the falling portion is small, only the rising portion was used. Differentiation from the right direction was also performed, and a rising portion when scanning from the right (corresponding to a falling portion when scanning from the left) was used. The height of the flat portion and the height of the cream solder are measured by the processing described below.

First, at step S50 in FIG. 10, a height correction memory (not shown) is provided and cleared. Subsequently, in step S51, the variable x is set to 2 and in step S52
Then, the ratio h'x of the height data to the previous line of the height data hx at that time is obtained, and the ratio is stored in the h 'memory (not shown) (step S53). h'x is threshold value 1.25
If it is larger (step S54), step S5
In step 5, hx-1 is stored in the height correction memory using (x-1) as an address. In step S56, x is incremented by 1 and the above processing is repeated until x = i + 1 (step S5).
7).

When the primary differentiation is completed, x = 3 in step S58, and a secondary differential value h "x is obtained in step S59.
If this secondary differential value is larger than the threshold value 1.25 (step S60), hx-1 is changed to (x-
1) is stored in the height correction memory as an address. Subsequently, in step S62, x is incremented by one, and the above processing is performed as x = i +
It repeats until it becomes 1 (step S63).

While FIG. 10 shows the differentiation from the left,
FIG. 11 shows the differentiation from the right. In step S71, a variable x is set to i-1, and in step S72, a ratio h'x of the height data to the next line of the height data hx at that time is obtained. Is stored in the h ′ memory (step S7).
3). If h'x is larger than the threshold value 1.25 (step S74), hx + 1 is changed to (x + 1) in step S75.
Is stored in the height correction memory as an address. In step S76, x is decremented by one, and the above processing is repeated until x = 0 (step S77).

When the primary differentiation is completed, x = i−2 is set in step S78, and a secondary differential value h ″ x is obtained in step S79. If the secondary differential value is larger than the threshold value 1.25, ( In step S81, hx + 1 is stored in the height correction memory using (x + 1) as an address in step S81, and x is decremented by one in step S82, and the above processing is repeated until x = 0 (step S83). ).

FIG. 12 is a table showing the measured height data of the cream solder portion of FIG. 8 and a part of the first derivative and second derivative data thereof (data near the line 45 in FIG. 8). . The first column in FIG. 12 is the height data, the second column is the first derivative from the left, the third column is the second derivative from the left, the fourth column, the fifth column is the first derivative, the second derivative from the right, The sixth column is the extracted data. For example, the first derivative h'x of the second row is 9.5 / 9.4 = 1.01 (step S52 in FIG. 10). The second derivative h "x is the ratio of the first derivative 1.01 /
0.99 = 1.02 (Step S5 in FIG. 10)
9). Looking at the row of the height data 19 in FIG. 12, the first derivative is 1.81, the second derivative is 1.72, and the threshold value is 1.2.
5 or more (steps S54 and S60). Therefore, the height data 10.5 of the row before this row is extracted (exemplified in the sixth column of FIG. 12).

The height data at which the differential value becomes larger as described above is stored in the height correction memory in steps S55 and S61 in FIG. 10 or steps S75 and S81 in FIG. 11, and is stored in step S84 in FIG. It is obtained as an average value hAV. In the image data shown in FIG. 8, this average value was 9.33. Since this average value corresponds to the height data of the flat portion (resist surface) on which the cream solder is printed, the height data (hAV) of this flat portion is subtracted from the height data (hx) in step S85. Actual height of cream solder from flat part (average height is 102μ)
m) is calculated. This is illustrated in FIG. The average height of the cream solder previously measured with another measuring instrument is also 10
Since it was 2 μm, it was confirmed that the height of the cream solder obtained by the above treatment was accurate.

In the above processing, the first derivative and the second derivative are used. However, the height data of the flat portion can be extracted only by the first derivative. Alternatively, height data may be extracted using only one differential value on the left or right side.

[Other Embodiments] With only the above-described processing, the differential value becomes large even in a portion other than the rising portion of the cream solder, and the height data of the flat portion may be extracted. Rather, the differential value becomes large even during the rise, and the height may be extracted.If the board has warpage, the light-cut image is captured at an angle and the height cannot be calculated correctly. May occur. Therefore, these problems are solved by the following processing.

The first problem is that when the height data is extracted, the flatness before and after the height data is checked, and if the height is flat, the height is not used. To solve. The second problem is that when the height of interest is adopted, it is checked whether height data has already been extracted before a plurality of heights, and if not adopted, the current height of interest data is newly added. And if it is adopted, the current attention height data is discarded. For this purpose, the processing shown in FIGS. 14A and 14B is provided between step S54 (S60) and step S56 (S62) in FIG.

In step S90 of FIG. 14 (a), if the primary differential value or the secondary differential value is greater than or equal to the threshold value in step S54 (S60) and the height data is extracted as the height data of the flat part, Flatness F 'in the vicinity

[0062]

(Equation 3)

(In the case of the second derivative, h ′ is used instead of h). Subsequently, in step S91, it is determined whether or not the flatness is larger than the threshold value (2). If the flatness is larger than the threshold value (2), the extracted height data of interest is adopted, and the others are not adopted. When actually calculated using the data in the table of FIG. 12, the extracted height data is 10.5, and the flatness F ′ according to Equation 3 is F ′ = (| 9.5−10 | + |
10-19 | + | 19-20 | + | 20-9.5 |) /
4 = 5.25> 2 (threshold). Therefore, it is adopted as attention height data and stored in the height correction memory in step S55 (S61).

The second problem can be solved by providing the processing of step S92 shown in FIG. 14B between step S91 and step S55 (S61). In this step, for example, it is checked whether the height data has been adopted up to five times before, that is, from (x−2) to (X−6). If not adopted, it is adopted as attention height data, and stored in the height correction memory in step S55 (S61).

FIG. 15 shows processing corresponding to the case where the differentiation is made from the right side with respect to the case where the differentiation is made from the left side in FIG.
Flatness F "

[0066]

(Equation 4)

In order to solve the second problem, in step S96, (x + 2) to (X + 6)
FIG. 14 is different from FIG. 14 in that it is checked whether the height data is used.

As a solution to the third problem, height data extracted and adopted by the above-described differential processing and the means for solving the first and second problems is calculated by multiple linear regression, and an approximate straight line is obtained to obtain an approximate straight line. Make corrections. To this end, as shown in FIG. 16, after step S83 in FIG. 11, the number n of hx in the height correction memory, that is, the number of extracted and adopted height data is checked (step S100). Subsequently, in step S101, hx = y in the height correction memory is set, and

[0069]

(Equation 5)

Are obtained, and then in step S102

[0071]

(Equation 6)

A0 and a1 are obtained from the equation, and the approximate expression a0 + a1x is obtained.
= Y.

For example, if the extracted height data of interest is (6
(2, 9) (151, 10) (184, 10.5) (23
8, 11.5) (362, 12) (449, 13), n = 6, Σx = 1446, Σy = 66, Σx ＾ 2
(Σ of the square of x) = 449790, Σxy = 16918
From this, a0 = 8.592474 and a1 = 0.00999 are calculated. Therefore, the approximate expression is: 8.592474+
0.00999x = y.

Next, in steps S103 to S106, x of the approximate expression is calculated from 1 to y values from the number of height data (i + 1), and hx is corrected in step S104. Assuming now that the number of height data is 480,
If the difference between the height data and the 480 y values is obtained, the difference is 480 height data whose inclination has been corrected. FIG.
(A) and (b) show the calculation results.

FIG. 18 shows an example in which the measurement is performed on a warped substrate and the zero point is corrected without correcting the inclination (step S85 in FIG. 11). The graph of the height data is rising to the right. I understand. When the inclination is corrected in accordance with the processing in FIG. 16, a result similar to that in FIG. 13 is obtained.

[Data Processing by Spreadsheet Software] In the above-described embodiment, the image data of the V-RAM image memory 40 was image-processed by the circuit configuration shown in FIG.
The image data in the AM image memory 40 can be loaded into spreadsheet software to perform the processing. V-RAM image memory 40
Image data is a bitmap image of 640 pixels in width × 480 pixels in height, and after converting each pixel into gradation data of 256 gradations, it is taken into the spreadsheet software of the cell of 640 columns × 480 rows. . Since the resolution between pixels is 10 μm, the pitch between cells is 10 μm when read into spreadsheet software because the pixels correspond to cells. However, since the actual spreadsheet software has a functional limitation of a maximum number of columns of 256 columns, the processing is performed by taking in 200-column × 480-row gradation data.

First, the taken-in gradation data is taken out for each 3 × 3 cell, and the filter processing is performed by checking the flatness of the gradation. The cell at the center of the 3 × 3 cell is set as the cell of interest, and the flatness of the gradation around the cell is calculated. The average of the absolute values of the differences between the cells around the cell of interest is determined. Columns A, B, C
.., The rows are 1, 2, 3,..., For example, the cell of interest is B2, and the flatness F is calculated according to Equation 1 (corresponding to the calculation by the calculation circuit 63 in FIG. 4). Then 3 × 3
The ratio to the difference ΔB between the maximum value of the gray scale and the minimum value of the gray scale in the cell No. is obtained (corresponding to the arithmetic circuit 65). The cell is subjected to the band elimination filter of Equation 2 (corresponding to the filter circuit 68). If ΔB = 0 or if F / ΔB is greater than the threshold, do nothing. Next, the cell of interest is moved to B3, the above processing is executed, and the processing is performed as B4, B5,. Then, the processing shifts to the next line and the processing is sequentially performed as in C2, C3,.

When the filtering process of the gradation data is completed as described above, the process proceeds to the next binarization process. The average value and the standard deviation of the gradation of each row are calculated (corresponding to the arithmetic circuits 71 and 72).
Then, for each cell, when the gradation data of the cell is larger than the average of the gradation of the row + 1.5 × standard deviation (comparator 75
) Rewrites the current cell value to 1, and erases the current cell value in the following cases. Cells A1, B1, C1,...
For the cell A
For 2, 2, B2, C2,..., The average value and standard deviation in the second row are used. Each cell is either 1 or blank.

After the value of each cell is binarized in this way, the small projection data and the isolated data are considered to be noise, so that the data is erased to remove the noise. That is, the filter processing of a to f as shown in FIG. 7 is performed. Assuming that the cell at the center of 3 × 3 is the cell of interest, FIG.
, The value of the cell of interest is deleted.
The five types of filters other than f are rotated by 90 degrees and executed (corresponding to the noise removal processing circuit 83).

Next, each row is referred to, and if all are blank, padding is performed by referring to the array of cells of numerical value 1 in the upper and lower rows (corresponding to the determination circuit 87). Next, the center of gravity value is calculated for the cell of numerical value 1 in each row. This means that for columns A, B, C,... As shown in FIG.
The numerical value becomes the value of the center of gravity (corresponding to the center of gravity position calculation circuit 96). In this example, the values of the cells in columns I and J are 1 for the first and second rows, and the number of column I is 9,
Since the number in column J is 10, the centroid value of the first and second rows is 9.5.
Becomes For the third, fourth and fifth rows, I column, H column, G column
The cell in the column is 1, and the barycentric value of each row is 9, 8, 7 which is the same value as the number assigned to each column. Hereinafter, the barycenter value of each row is obtained in the same manner.

As described above, each processing block 60 in FIG.
70, 80, 90 can also be processed by software.

In the calculation of the flatness in step S90 in FIG. 14, in the spreadsheet calculation, for example, when the cell of H3 is extracted as the height of interest, F ′ = (| H1-H2 | + | H2-H
4 | + | H4-H5 | + | H5-H1 |) / 4. Assuming that the threshold value is S, attention height data extracted when F ′> S is adopted, and the other values are not adopted. In the embodiment, S = 2. In addition, processing for solving the second or third problem can be similarly performed using a spreadsheet.

[0083]

As described above, according to the present invention, the height data of a protruding object is obtained from a captured image of the protruding object, and the height data is subjected to a first derivative and a second derivative or a first derivative.
Since the height data of the flat part is obtained from the differential value, there is no need to obtain the height data of the flat part before the protrusion is formed, and every time a protrusion is formed on the flat part, the protrusion is obtained. If you need to measure the height of
The tact time for measurement can be significantly improved.

In the height data processing according to the present invention, the gradation data of the imaged pixel is binarized after being subjected to the flattening processing, so that stable height data can be obtained. In addition, when a blank line is generated as a result of performing a filtering process on the binarized data, the data is embedded in the blank line according to the array of the binarized data in the preceding and succeeding lines. Height data is required.

Further, according to the present invention, even if the differential value becomes large except at the rising portion of the protruding portion, the flatness near the extracted height data is checked. Is the height data of the flat part,
Reliable height data can be obtained.

Even if the differential value increases during the rising of the protruding portion, if the height data of the flat portion has already been adopted from the plurality of height data before that, the extraction is performed. By discarding the height data that has been set, similarly reliable height data is assured.

Further, when the object to be measured has a warp in the direction along the line light of the object to be measured, multiple linear regression is performed based on a plurality of height data adopted as height data of the flat portion. The approximate expression of the height data of the flat part is obtained using the approximate expression, and the inclination is corrected in the direction along the line light of the flat part from the approximate expression. And correct height measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a height measuring device used in the present invention.

FIG. 2 is a side view of the height measuring device of FIG.

FIG. 3 is a circuit diagram showing a circuit configuration for acquiring image data from an image obtained by projecting line light.

FIG. 4 is a circuit diagram showing a circuit configuration for processing acquired image data.

FIG. 5 is a flowchart illustrating a flow of processing of an image obtained when line light is projected on a cream solder portion.

FIG. 6 is an explanatory diagram showing an image obtained when a line light is projected on a cream solder portion.

FIG. 7 is an explanatory diagram showing filter data used for filtering image data.

FIG. 8 is a diagram showing height data of cream solder.

FIG. 9 is a diagram showing first and second derivatives of height data of the cream solder of FIG. 8;

FIG. 10 is a flowchart illustrating a flow of differentiating height data from a left side to obtain a differential value.

FIG. 11 is a flowchart illustrating a flow of differentiating height data from a right side to obtain a differential value.

FIG. 12 is a table showing a process of obtaining height data of a flat portion of a wiring board from a differential value.

FIG. 13 is a diagram showing height data of cream solder measured from a flat portion of a wiring board obtained based on a differential value.

FIG. 14 is a flowchart showing a process for removing unreliable data extracted from portions other than the rising portion of the cream solder.

FIG. 15 is a flowchart illustrating a process when differentiation is performed from the opposite side in the same process as in FIG. 14;

FIG. 16 is a flowchart showing a flow for correcting a warp of a substrate.

FIG. 17 is a table showing processing data when the substrate has warpage.

FIG. 18 is a diagram showing height data when the substrate has warpage.

FIG. 19 is an explanatory diagram showing an example for obtaining a barycentric value from pixel or cell information.

FIG. 20 is a perspective view showing a configuration of a conventional three-dimensional measuring device.

[Explanation of symbols]

 1 laser light source 5 line generator 6 CCD camera 9 line light

Claims (10)

[Claims] A line light is projected onto an object to be measured having a protrusion projecting from the flat portion, and the flat portion and the protrusion which are cut by the line light are imaged, and the protrusion from the flat portion is detected by a light cutting method. In a height measuring method for measuring the height of a protruding object, obtaining height data of the protruding object from a captured image of the protruding object, performing first-order differentiation and second-order differentiation or first-order differentiation on the height data, and flattening from the differential value A height measuring method characterized by extracting height data of a part. 2. The method according to claim 1, wherein the first derivative and the second derivative or height data before the first derivative exceeds a threshold value are extracted and used as height data of a flat portion. Height measurement method. 3. The flatness in the vicinity of the extracted height data is checked, and if the height is not flatter than a predetermined value, the extracted height data is used as the height data of the flat portion. Or the height measuring method according to 2. 4. When height data of a flat portion is already adopted from a plurality of height data before the height data is extracted, the extracted height data is discarded. The height measuring method according to any one of claims 1 to 3, wherein the height is measured. 5. An approximate expression of height data of a flat portion is obtained by using multiple linear regression based on a plurality of pieces of height data adopted as height data of the flat portion, and a flat portion height data is obtained from the approximate expression. The height measuring method according to any one of claims 1 to 4, wherein inclination correction in a direction along the line light is performed. 6. A projecting object having a protrusion projecting from a flat portion, projecting line light onto the measured object, imaging the flat portion and the projecting object cut by the line light, and projecting from the flat portion by a light cutting method. A height measuring device for measuring the height of the light, a light projecting device for projecting line light on the projecting object, a unit for capturing an image of the projecting object on which the line light is projected, and a projecting object by the line light. Means for processing the image data to calculate the height data of the protruding object; means for performing primary differentiation and secondary differentiation or primary differentiation of the height data; means for calculating the height of the flat portion from the differential value And a means for calculating the height of the protruding object based on the height of the flat portion. 7. A means for calculating the height of the flat portion, wherein the first derivative and the second derivative or height data before the first derivative exceeds a threshold value are extracted to be the height of the flat portion. The height measuring device according to claim 6, characterized in that: 8. The means for calculating the height of the flat portion examines flatness near the extracted height data, and calculates the height data of the flat portion if the height data is not flatter than a predetermined value. The height measuring device according to claim 6, wherein the height measurement data is used as height data. 9. The means for calculating the height of the flat portion includes: when the height data is extracted, when the height data of the flat portion is already adopted from a plurality of pieces of height data before the height data is extracted. The height measuring device according to any one of claims 6 to 8, wherein the device discards the extracted height data. 10. An approximate expression of height data of a flat portion is obtained by using multiple linear regression based on a plurality of height data adopted as height data of the flat portion, and a flat portion height data is obtained from the approximate expression. The height measuring device according to claim 6, further comprising a correction unit configured to perform a tilt correction in a direction along the line light.