JPH0658330B2 - Light intensity setting circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is used in the field of optical devices.

The present invention relates to a light quantity setting circuit, and more particularly to an optimum light quantity setting circuit that automatically sets the optimum light quantity in an image capturing section of a visual inspection apparatus for printed wiring boards.

〔Overview〕

In the light quantity setting circuit for detecting the light quantity by the one-dimensional sensor and setting the optimum light quantity, the video signal detected by the one-dimensional sensor is binarized by two threshold values of different values, and within one scanning. By measuring the total sum of the "high" level widths of each binarized signal and making a comparison, and setting the light intensity at which they almost match as the optimum light intensity, the optimum light intensity can be set easily and accurately. This is done in a short time.

[Conventional technology]

Conventionally, a copper foil of a printed wiring board is obtained by using a plurality of one-dimensional cameras including one-dimensional sensors such as CCDs and a reflected light type appearance inspection device for a printed wiring board having a plurality of corresponding illumination light sources. When setting the optimum light intensity for capturing the surface image, the operator adjusts the light intensity of each device while observing the analog video signals output from multiple one-dimensional cameras using a waveform observation device such as an oscilloscope. The volume of light was set by operating the volume.

[Problems to be solved by the invention]

However, in the setting of the amount of light by the worker described above, the reflectance of light on the copper foil surface is different due to the treatment method of the copper foil surface at the time of pattern formation of the printed wiring board or the oxidation of the copper foil surface due to aging. Therefore, a uniform analog video signal cannot be obtained. Or, since there are variations in the illumination light source, it takes skill to obtain a balanced and uniform image for each one-dimensional camera. For this reason, (i) an accurate image cannot be captured unless the light amount is set accurately, and defects may be missed. Or the false recognition rate becomes high.

(Ii) It takes time to set the light amount.

There were problems such as.

Further, in setting the light amount, usually, an operation of setting the optimum light amount by gradually increasing the light amount from the state where the light amount is zero is performed. This is because the sensor is saturated when the high light level is set first, which adversely affects the light amount detection. Therefore, in order to set the light amount from zero for each printed wiring board that is a subject, it is required that the light amount can be set in a short time.

The object of the present invention is to solve the above problems by
An object of the present invention is to provide a light amount setting circuit which can easily obtain an accurate image, which makes it possible to eliminate defects from being seen, reduce the false recognition rate, and shorten the time for setting the light amount.

[Means for solving problems]

The first invention includes a one-dimensional sensor that detects the amount of light,
In a light quantity setting circuit including means for gradually increasing the light quantity of a light source applied to a subject and setting an optimum light quantity, an analog video signal output from the one-dimensional sensor is supplied with a first threshold value and a second threshold value, respectively. First binarization measurement circuit and second binarization circuit that binarizes values and measures the total width of "high" level signals in one scan and outputs the first measurement signal and the second measurement signal, respectively. And a rough match detection circuit that outputs a rough match signal when the difference between the first and second measurement signals is input and compared and is within a predetermined allowable range. And a light amount control circuit for inputting a signal and controlling the light amount of an optical system including the one-dimensional sensor.

The second invention includes a one-dimensional sensor that detects the amount of light,
In a light quantity setting circuit including means for gradually increasing the light quantity of a light source given to a subject and setting an optimum light quantity, an analog-digital conversion circuit for converting an analog video signal output from the one-dimensional sensor into a digital signal, and a converted signal. The digital signals are binarized with a first threshold value and a second threshold value, respectively, and the sum of the widths of the "high" level signals in one scan is measured to obtain the first measurement signal and the second measurement signal, respectively. A first binarized measurement circuit and a second binarized measurement circuit that output a measurement signal, and the first and second measurement signals are input and compared, and the difference between the two signals is a predetermined allowable range. And a light quantity control circuit for inputting the rough match signal and controlling the light quantity of the optical system including the one-dimensional sensor.

[Action]

The analog video signal from the one-dimensional sensor is converted to a digital signal as it is or by an analog-digital conversion circuit, and the first and second binarization measurement circuits make it possible to convert the binary value by the first threshold value in one scan. The measured value of the sum of the "high" level widths of the binarized signal and the measured value of the sum of the "high" level widths of the binarized signal by the second threshold are compared by the coarse match detection circuit, and the Detection is performed so that the difference is within a certain allowable range (hereinafter, this detection is referred to as rough match detection), and a rough match detection signal is output. As a result, the light amount control circuit stops the light amount increase control and sets the light amount when the rough coincidence signal is input using the circuit that gradually increases the light amount.

That is, binarization is performed with two different thresholds, and the sum of the "high" level widths of the two binarized signals (corresponding to power)
Since the non-uniformity of the analog video signal from the one-dimensional sensor is eliminated by making the values substantially coincide with each other, it is possible to accurately set the optimum light amount. Moreover, the control can be automatically performed and the setting becomes easy.

EXAMPLES Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the first invention, and FIGS. 2 (a), 2 (b) and 2 (c) are explanatory views showing a process until obtaining the optimum light amount.

In this embodiment, a one-dimensional sensor 1 composed of a line sensor for capturing the reflected light on the copper foil surface, and an analog video signal 6 output from the one-dimensional sensor 1 are converted into a first threshold value 13 shown in FIG. A first binarization measurement circuit 2 that binarizes and measures the sum of the "high" level widths of the first binarization signal 15 in one scan, and in parallel with the first binarization measurement circuit 2. The second binarization, which is provided in FIG. 3 and binarizes with the second threshold 12 shown in FIG. 3, and measures the sum of the widths of the “high” level of the second binarized signal 14 in one scan Measurement circuit 3, first measurement signal 7 output from first binarization measurement circuit 2, and second binarization measurement circuit 3
The second measurement signal 8 output from the above is input, the two are compared, coarse coincidence detection is performed, and a coarse coincidence signal 9 is output, and the light amount of the light source 16 is controlled by the coarse coincidence signal 9. The light amount control circuit 5 is included. Reference numeral 17 is a printed wiring board under test.

The feature of the first invention is that, in FIG. 1, first and second binarization measurement circuits 2 and 3 and a rough match detection circuit 4 are provided.
And the light amount control circuit 5 is provided.

Next, the operation of this embodiment will be described with reference to FIG.

First, the light amount control circuit 5 gradually increases the light amount of the light source 16. As shown in FIG. 2 (a), when the analog video signal 6 converted according to the reflected light from the copper foil surface reaches the level of the first threshold 13, the first binary signal 15 is obtained. To be In this case, since the non-uniform reflection of light on the surface of the copper foil is binarized, the first binarized signal 15 becomes discontinuous and an accurate image cannot be obtained. Further, since the second binarized signal 14 by the second threshold 12 is not output, the measured values of the sum of the widths of the “high” level of the binarized signals 14 and 15 within one scanning are roughly the same. Not detected.

Then, the light amount control circuit 5 increases the light amount of the light source 16 again.
FIG. 2 (b) shows a case where the analog video signal 6 converted according to the reflected light from the surface of the copper foil reaches the second threshold 12 level. In this case, the first binarized signal 15 by the first threshold value 13 is regarded as an almost accurate image, but the second binarized signal 14 by the second threshold value 12 is the copper foil surface. Since the non-uniform portion of the light reflection of 2 is binarized, a discontinuous signal is not obtained and an accurate image cannot be obtained. Therefore, the sum of the "high" level widths within one scanning of both is determined by the coarse coincidence detection circuit 4. The coarse match signal 9 is not output because the rough match does not occur even when compared with.

Therefore, the light amount of the light source 16 is further increased. Fig. 2 (c)
Is a case where the output of the analog video signal 6 is entirely increased and exceeds the second threshold 12 level even if there is unevenness in the reflected light from the surface of the copper foil. At this time, the total sum of the widths of the “high” level of the first binarized signal 15 and the total sum of the widths of the “high” level of the second binarized signal 14 in one scan roughly agrees for the first time. Then, the rough match signal 9 output from the rough match detection circuit 4 is input to the light quantity control circuit 5 to stop the light quantity increase control of the light source 16, and the series of operations for setting the light quantity is completed.

The light amount setting described above is performed for each one-dimensional camera.

FIG. 3 is a block diagram showing an embodiment of the second invention. In this embodiment, the analog video signal 6 output from the one-dimensional sensor 1 described in the embodiment of the first invention of FIG. One binary measurement circuit 2
At a, digital binarization is performed using a digital threshold value (not shown), and the sum of the widths of the "high" level of the first binarized signal in one scan is measured. Similar processing is performed in the second binarization measurement circuit 3a. After that, the optimum light amount is set by performing the increase control of the light amount of the light source 16 in the same procedure as the embodiment of the first invention. In this case, the binarized signal is generated more accurately, and more accurate setting is performed.

A feature of the second invention is that the analog-digital conversion circuit 10 in FIG. 3 is added to the circuit of FIG.

〔The invention's effect〕

As described above, the present invention gradually increases the light amount,
A rough match is detected by comparing the measured values of the binarized signal with the first threshold value and the second threshold value. Then, the light quantity increase control is stopped by the rough coincidence detection signal and the optimum light quantity is automatically set. (I) It is possible to easily obtain a balanced and accurate image for each one-dimensional camera. It has the effect of reducing the misrecognition, lowering the false recognition rate, and (ii) shortening the time for setting the optimum light intensity that differs for each subject.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the first invention. FIG. 2 is an explanatory view showing the process of setting the light quantity. FIG. 3 is a block diagram showing an embodiment of the second invention. 1 ... One-dimensional sensor, 2 and 2a ... 1st binarization measurement circuit, 3 and 3a ... 2nd binarization measurement circuit, 4 ... Coarse coincidence detection circuit, 5 ... Light quantity control circuit, 6 ... analog video signal, 7 ... first measurement signal, 8 ... second measurement signal,
9 ... Coarse coincidence signal, 10 ... Analog-digital conversion circuit, 11 ... Digital video signal, 12 ... Second threshold value, 13 ... First threshold value, 14 ... Second binary value Signal,
15 …… first binarized signal, 16 …… light source, 17 …… printed wiring board.

Claims (2)

[Claims] 1. A light quantity setting circuit including a one-dimensional sensor for detecting a light quantity, comprising means for gradually increasing the light quantity of a light source applied to an object to set an optimum light quantity, wherein an analog video output from the one-dimensional sensor The signals are binarized with the first threshold and the second threshold, respectively, and the sum of the widths of the "high" level signals in one scan is measured to obtain the first measurement signal and the second measurement signal, respectively. The first binarized measurement circuit and the second binarized measurement circuit for outputting, and the first and second measurement signals are input and compared, and the difference between the two signals is within a predetermined allowable range. In this case, the light quantity setting circuit includes a rough match detection circuit that outputs a rough match signal, and a light quantity control circuit that receives the rough match signal and controls the light quantity of an optical system including the one-dimensional sensor. 2. A light quantity setting circuit including a one-dimensional sensor for detecting a light quantity, and comprising means for gradually increasing the light quantity of a light source applied to an object to set an optimum light quantity, wherein an analog video output from the one-dimensional sensor An analog-to-digital conversion circuit for converting a signal into a digital signal, and the converted digital signal is binarized by a first threshold value and a second threshold value, respectively, to obtain "high" in one scan.
A first binarization measurement circuit and a second binarization measurement circuit for measuring the sum of the widths of the level signals and outputting the first measurement signal and the second measurement signal, respectively, and the first and second A coarse match detection circuit that outputs a rough match signal when a difference between the two signals is within a predetermined allowable range by inputting a measurement signal, and an optical system including the one-dimensional sensor that receives the rough match signal And a light amount control circuit for controlling the light amount of the light amount setting circuit.