JPH06109425A - Circuit for detecting center of ic lead pin - Google Patents

Abstract

PURPOSE:To achieve that, by utilizing the shade gradation of an image, the central position of a lead pin for an IC whose image is sensed by an image sensing device is detected at a resolution which is finer than the resolution of the image sensing device. CONSTITUTION:Images of lead pins 1A for an 1C are sensed by an image sensing device 2. They are changed into multivalued digital signals by an A/D converter 3 and stored in a memory 4. Data which have been stored in the memory 4 are input sequentially to a filter 5 for running average use. The filter length of the filter 5 for running average use is made nearly equal to the interval between the lead pins 1A for the IC 1, the fundamental wave component of the lead pins 1A is extracted by obtaining moving averages. The output of the filter 5 for obtaining moving averages is stored in a memory 6. The output of the memory 6 is input to a lead-pin center detection part 7, and the peak value of the fundamental wave component is detected and output.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for detecting the central position of a lead pin of an IC in an IC automatic inspection device when the IC is automatically mounted in a measuring socket. Is about. FIG. 5 shows the configuration of a center position detecting circuit for an IC lead pin according to the prior art. 5 in FIG. 5 is I
C, 1A is a lead pin, 2 is an image pickup device, 3 is an A / D converter, 4 is a memory, 8 is a binarization circuit, and 9 is a lead pin center detector. In FIG. 5, the image pickup device 2 scans the IC 1 with a CCD sensor or the like for each part to capture an image. The captured image is A / D converted into a multi-valued digital signal by the A / D converter 3.
It is converted and stored in the memory 4. The data stored in the memory 4 is converted into a binary signal by the binarization unit 8, and the lead pin center detection unit 9 outputs the lead pin center signal. Next, the process of obtaining the center of the lead pin 1A with the configuration of FIG. 5 will be described with reference to FIG. Figure 6
(A) shows a state in which the image pickup device 2 scans the lead pin 1A of the IC 1 and picks up an image, and the scanned position is a scanning line 37. 6A shows the scanning line 37 of FIG.
The brightness is shown above. The output of the lead pin 1A is at "H" level, and the other portion is at "L" level. Reference numerals 31a to 31d in FIG. 6A indicate positions corresponding to the centers of the lead pins. FIG. 6C shows an array of pixels of the CCD sensor of the image pickup device 2. 6D is an output signal of the image pickup apparatus 2. The signal of FIG. 6A is output to the A / D converter 3 for each pixel of FIG.
The pixel signal is stored in. 6E and 6F are output waveforms obtained by binarizing the pixel signals stored in the memory unit 4 by the binarization unit 8. FIG. 6E sets the threshold value for binarization to THa in FIG. 6 is a waveform when the threshold value for binarization is shown in FIG.
This is the waveform when THb is set to D. In the case of binarization, the waveform after binarization differs depending on the threshold level, as shown in FIGS. Keys in FIG. 6 are memory position coordinates of the memory 4 and are used by the lead pin center detection unit 9 to obtain the center of the "H" level portion of the output of the binarization unit 8. In FIG. 6, the center value of the “H” level portion of the pixel signal of the memory 4 is the center of the lead pin. As shown in 34a to 34d, the center of the "H" level portion in FIG. 6E is (Xi2 + X
i3) / 2, Xi6, (Xi9 + Xi10) / 2, Xi13. The center of the “H” level portion of FIG.
As shown in d, (Xi2 + Xi3) / 2, (Xi5 + Xi6)
/ 2, (Xi9 + Xi10) / 2, (Xi12 + Xi13) / 2
Becomes In the configuration shown in FIG. 5, the position of the lead pin 1A detected by the IC1 is different depending on the setting of the threshold level of the binarization unit 8, and the lead pin 1A is also different.
There is a problem that the accuracy of the position of is limited to the pixel width of the image pickup device. According to the present invention, a signal stored in the memory unit 4 as a multi-valued digital signal is processed by a moving average filter to extract lead pin position information, and a lead pin position detection circuit for accurately detecting the position of the lead pin is disclosed. For the purpose of provision. In order to achieve this object, according to the present invention, an image pickup device 2 for picking up an image of an IC 1 having a lead pin 1A and an image signal output of the image pickup device 2 are converted into a multilevel digital signal. A / D converter 3, a memory 4 that stores the output of the A / D converter 3 in pixel units, and a moving average filter 5 that receives the output of the memory 4 and performs moving average processing.
And a memory 6 that receives the output of the moving average filter 5
And a lead pin center detection unit 7 for detecting the center of the lead pin 1A by using the output of the memory 6 as an input, and the filter length of the moving average filter 5 is made substantially equal to the interval between the lead pins 1A of the IC1 and The fundamental wave component of the output waveform of the memory 4 is extracted, recorded in the memory 6, and the coordinates of the maximum value of the fundamental wave component waveform stored in the memory 6 are detected as the center position of the lead pin 1A. The structure of the lead pin center position detection circuit according to the present invention is shown in FIG. In FIG. 1, 5 is a moving average filter, 6
Is a memory, 7 is a lead pin center detector, and others are shown in FIG.
Is the same as. In FIG. 1, the moving average filter 5 includes, for example, a shift register for inputting the pixel values of the memory 4 to each of the registers A1 to A40 in a pipeline manner, a multiplier B0 connected to the output of the memory 5, and each register. Multipliers B1 to B40 connected to the outputs of A1 to A40 and multipliers B0 to B40
It consists of an adder that adds 40 outputs. The output of the adder is stored in the memory 6. EXAMPLE A process for obtaining the center of the lead pin 1A in the configuration of FIG. 1 will be described with reference to FIG. Figure 2
Noa scans the lead pin 1A of the IC1 with the imaging device 2,
The imaged state is shown, and the scanned position is the scanning line 70. 2A shows the brightness at the scanning line 70 in FIG. 2A, the output is "H" level at the lead pin 1A portion, and the "L" level is at the other portion.
Reference numerals 61a to 61d in FIG. 6A indicate positions corresponding to the centers of the respective lead pins, and each cycle is a rectangular wave having a length of T61. 2C shows the waveform of the fundamental wave component of the waveform shown in FIG. 2A, and the length of the period T62 is the distance between the centers of the lead pins. 2D shows an array of pixels of the CCD sensor on the image pickup surface of the image pickup apparatus 2. 2 is an image pickup device 2
The output signal of the memory 4 is output to the A / D converter 3 for each pixel shown in FIG.
The pixel signal is stored in. FIG. 2F shows the spatial coordinates of the memory 4 when the signal of FIG. 2E is stored in the memory 4, and corresponds to the pixel unit of the CCD sensor. 2 shows the waveform of the moving average filter, and here shows the waveform of the Hamming window function. Figure 2
The distance between the lead pins 1A is required to be about 4 pixels per pixel of the CCD sensor. In FIG. 1, since the fineness of reading the pixel value of the moving average filter 5 is 10 times, the shift register A of the moving average filter 5 is used.
Is 40 and the number of multipliers B is 41. Therefore, the length of the Hamming window function is set to 4 pixels, and the count of the Hamming window function is set in each multiplier. In FIG. 2, the position coordinates of the multiplier of the moving average filter 5 are shown by B1 to B40. In the moving average filter 5 of FIG. 1, the data from the memory 4 are sequentially input to the shift registers A1 to A41 by a pipeline method, and are respectively calculated by the multipliers B0 to B40 and added. It is added by the device 54 and input to the memory 6. Coefficients are set in advance in the arithmetic units B1 to B40. In FIG. 1, the Hamming window function is used as the coefficient. 2 is a spatial coordinate of the memory 6 when the output of the moving average filter 5 is loaded into the memory 6,
It is ten times finer than the memory 4. The fundamental wave component can be extracted by multiplying and adding this coefficient to the data of the memory 4 that is sequentially input by the pipeline method and taking the moving average. 2C shows the output waveform of the moving average filter 5 recorded in the memory 6, which substantially coincides with the waveform of FIG. Next, the operation of the moving average filter 5 will be described. When the moving average filter 5 performs moving average processing on the pixel values on the memory 4, the harmonic components are attenuated and the fundamental sine wave is extracted. The waveform of the Hamming window function 71 is shown in FIG. In FIG. 3, when the period of the Hamming window function 71 is To, the fundamental frequency component is fo. Next, the frequency characteristic of the Hamming window function is shown in FIG.
Shown in. From FIG. 4, the cycle T of the lead pitch shown in FIG.
If 61 is made to substantially match the period To of the Hamming window function 71 of FIG. 3, the output of the moving average filter 5 can attenuate the fundamental wave fo by 8 dB and the second harmonic or higher by 42 dB or more. As a result, the lead pin 1 on the memory 4
The fundamental wave of A can be extracted. Although the Hamming window function is used in the embodiment, the fundamental wave can be extracted by other functions. When the output after the calculation by the moving average filter 5 of FIG. 1 is taken into the memory 6, a fundamental wave component substantially equal to the fundamental wave component 62 of the light quantity on the image pickup surface shown in FIG. , Are reproduced as shown in FIG. In FIG. 2, the positions of the maximum values of the waveform are 68a to 68d. The lead pin detection unit 7 in FIG. 1 can obtain the coordinates of the center position of the lead pin 1A by obtaining the coordinates of the pixel on the memory having the maximum pixel value in the X-axis direction of the memory 6. At this time, the coordinate position accuracy is 10 times the coordinate position accuracy determined by the memory unit 4. Although the moving average filter 5 is composed of a shift register, a multiplier and an adder in FIG. 1, it can be realized by software. The present invention focuses on the fact that the lead pins of the IC are arranged at equal intervals so that the light quantity on the imaging surface becomes a rectangular wave with a constant period. The rectangular wave is the principle of the Fourier series. Has a sine wave 62 equal to the period of the rectangular wave as a fundamental wave component, the sine wave component is extracted from the output signal of the image pickup apparatus 2 without distortion, and the maximum values 61a to 6a of the waveform are obtained.
Since the center of the lead pin is obtained by calculating 1d, the center of the lead pin 1A is accurately obtained by the process after the image signal of the image pickup device is captured in the memory without increasing the number of pixels of the image pickup device used for image pickup. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of an IC lead pin center position detection circuit according to the present invention. FIG. 2 is an explanatory diagram of a process of obtaining the center of the lead pin according to the present invention. FIG. 3 is a waveform diagram of a Hamming window function. FIG. 4 is a frequency characteristic diagram of a Hamming window function. FIG. 5 is a configuration diagram of a center position detection circuit for an IC lead pin according to a conventional technique. FIG. 6 is an explanatory diagram of a process of obtaining a center of a lead pin according to a conventional technique. [Description of Reference Signs] 1 IC 1A IC lead pin 2 Imaging device 3 A / D converter 4 Memory 5 Moving average filter 6 Memory 7 Lead pin center detection unit 8 Binarization unit 9 Lead pin center detection unit

Claims (1)

An image pickup device 2 for picking up an image of an IC 1 having a lead pin 1A, and an image pickup device 2 for converting an image signal output from the image pickup device 2 into a multilevel digital signal A
/ D converter 3 and memory 4 for storing the output of the A / D converter 3 in pixel units
And the output of the memory 4 as an input, the moving average filter 5 for performing the moving average processing, the memory 6 having the output of the moving average filter 5 as an input, the output of the memory 6 as an input, and the center of the lead pin 1A A lead pin center detection unit 7 for detecting, a filter length of the moving average filter 5 is made substantially equal to an interval between the lead pins 1A of the IC 1, a fundamental component of an output waveform of the memory 4 is extracted by the moving average process, and the memory 6 The IC lead pin center position detection circuit, which detects the coordinates of the maximum value of the fundamental wave component waveform stored in the memory 6 as the center position of the lead pin 1A.