JPS6030889B2 - Imaging type article detection or inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that obtains a video signal of an article using an imaging device and analyzes this signal to detect or inspect the article.

There are various types of photography equipment, but one is one in which a large number of light receiving elements are lined up, the outputs of these light receiving elements are stored in corresponding bits of a register, and then this register is shifted to sequentially output the stored contents. There is a method that uses an image sensor made of For example, a CCD image sensor is known as an image sensor used in such a system. According to this element, the video signal is a pulse train in which one pulse corresponds to one light receiving element, and the height of each pulse represents the brightness of the pixel in an analog manner. The sensitivity of this image sensor (generally any photoelectric device using a semiconductor) differs depending on the temperature. Therefore, it is necessary to take measures for temperature compensation. The present invention is directed to an article detection or inspection device using the above-mentioned image sensor, and is also related to the above-described temperature compensation means.

Therefore, in order to clarify the purpose of the present invention, the means for temperature compensation will be explained first. FIG. 1 shows an outline of the configuration of an image sensor used in the present invention.

A large number of PHs are light-receiving elements arranged in a line, and an image of the article is formed thereon. G is a gate, and a shift register S having bits corresponding to each light receiving element is provided across this gate. At the beginning of scanning, one pulse is given to the gate G to open it and the output of each light receiving element PH is stored in the corresponding bit of the shift register S. Next, while the gate G is closed, a shift pulse is applied to the register S to shift the stored contents and sequentially output the stored contents corresponding to each light receiving element. This is a video signal, which is a pulse train as shown in FIG. While the contents of the register S are being sequentially output, each light-receiving element integrates the photocurrent, and this becomes the output of the light-receiving element in the next scan. In such an element, if the number of shifts of the register S during one scan is greater than the number of light receiving elements PH, the shift register S will release all the memory received from the light receiving elements near the end of the scan, and the light receiving (Unless the output of the element is accepted), an empty transfer is performed, and an empty transfer bit is output. In FIG. 2, T is one scanning period, T' is the range of the video signal corresponding to each light receiving element PH, and the number of pulses is the same as the number of PHs. The part t is an empty transfer bit output, and originally the height should be 0, but it is not completely 0. Moreover, the height h of the output pulse of this idle bit is related to temperature and exhibits a change equal to the change in the output of the light receiving element due to temperature. Therefore, the output height h of this empty transfer bit
The use of the signal as a signal for temperature compensation was proposed by the applicant in a patent application of the same name on the same day as the present application. In other words, the output level h of this empty transfer bit is held, and the level obtained by adding an appropriate level to this is set as the slice level L, and the video signal shown in FIG. 2 is sliced, and video signals of the same level or higher are extracted and used for various determinations. By doing so, temperature compensation can be achieved by changing the height of h depending on the temperature. However, on the other hand, each light receiving element PH and each bit of the shift register S are separated by a gate G, and while G is closed, the output of PH should not affect the register S, but in reality, the gate G When the speed at which the shift register S is shifted is relatively slow due to leakage while the register is closed, each bit of the register is affected by the corresponding light receiving element. If we look at this effect on the data within each bit, the data in each bit is sequentially transferred to the adjacent bit and retrieved, so during idle transfer, the influence of each light receiving element is sequentially applied to the outside of each data and is averaged. Therefore, each bit output during idle transfer is almost the same even if the amount of light incident on each light receiving element is different, and the average illuminance over the entire surface of the image sensor is usually approximately constant over time. Therefore, the output of the idle transfer bit represents the effect of temperature. Figure 3 shows one of the light receiving elements PH and the shift register S when the amount of incident light is changed.
shows the relationship between the output of the corresponding bit and the output of the corresponding bit. Of course, this figure shows the case where the gate G between PH and S is closed, but since the output of one bit of the shift register cannot be taken out directly, each light receiving element is illuminated with uniform illuminance. The output of each light-receiving element during illumination is stored in the corresponding bit of the shift register, and each bit output is sequentially shifted and output, and the output when empty transfer is performed with the gate closed under the same conditions. This is a graph of data collected while changing the illuminance of the entire surface of the light receiving element to show the relationship with the corresponding bit output. The output of the PH increases as the intensity of the incident light increases, but it saturates when the output reaches about 3.75V. On the other hand, the output of the corresponding bit of register S (the output during the above-mentioned idle transfer) is P.
The H output is proportional to the PH output up to about 3V, and the ratio between the two is about 2:1. However, when the output of PH exceeds 3V, the output of the corresponding bit of the register suddenly increases and P
When the output of PH catches up with the output of H and reaches 3.75V, the output of the corresponding register also becomes approximately 3.75V. The above relationship is not related to temperature. In other words, the relationship shown in Fig. 3 is not related to temperature; for example, the intensity of incident light when the output of the light receiving element is 2V changes depending on the temperature, but when the output of the light receiving element is 2V and the gate G is closed,
The relationship that the idle transfer bit output becomes IV due to leakage does not change depending on the temperature. Since image pickup devices such as CCD image sensors have such properties, the following problems occur when the temperature compensation method described above is used. In other words, it is fine if the intensity of light that enters the image sensor from the object to be examined does not vary much from object to object, but if this changes significantly, for example, if the object is emitting its own light, and the intensity of that light emitted The output of the empty transfer bit will vary depending on the temperature and the brightness of the object. However, when a very bright object comes and the output of the light-receiving element approaches the saturation value, the output of the empty transfer bit itself becomes approximately equal to the output of the light-receiving element, and the slice level L (see Figure 2) is obtained by adding an appropriate level to it. ) moves above the video signal, making it impossible to obtain an article detection signal.The present invention is aimed at solving this problem.

In order to achieve this object, the present invention, in addition to the above-described temperature compensation method, outputs an article detection signal regardless of the operation of the temperature compensation circuit when the output of the image sensor exceeds a certain limit. I made it. As long as the light incident on the light-receiving element becomes strong enough that the output of the light-receiving element approaches saturation, there will be no problem even if an article is present, regardless of the temperature. The present invention will be explained below with reference to Examples. FIG. 4 shows an embodiment of the present invention.

Reference numeral 1 denotes a timing pulse generation circuit which generates a pulse to open the gate G of the image pickup device shown in FIG.

2 is an image sensor shown in FIG. 1, which uses a CCD image sensor.

The output of the image sensor 2 is amplified by an amplifier AMP and sent to a comparison circuit 4. The slice level indicated by L in FIG. 2 is also applied to the comparator circuit 4 as a reference level. A
The output of the MP is also sent to the sample hold circuit 3. On the other hand, a sampling pulse is sent to the same circuit from the pulse generating circuit 1 at an appropriate timing during the period t during which the idle transfer bit is output as shown in FIG. 2, and the level h of the output pulse of the idle transfer bit is read. hold. This held signal is applied to the adder circuit 5. On the other hand, a level appropriately set by a setter 6 is also applied to the adder circuit 5, which is added to the output of the sample and hold circuit 3, and the added output is sent to the comparator circuit 4 as the aforementioned slice level. In this way, normally only pulses higher than level L in FIG. 2 are selected from the comparator circuit 4 and sent to a discrimination circuit (not shown) via the OR circuit OR. Further, the signal held in the sample and hold circuit 3 is sent to a second comparison circuit 7, where it is compared with a reference level set to a certain value, and the output of the sample and hold circuit 3 is higher than the reference level. In this case, a signal is output from the comparator circuit 7 and sent to a discriminator circuit (not shown) through an OR circuit OR.

The reference level set in the comparator circuit 7 in this step is determined with reference to FIG. For example, if the slice level L is set to IV under a certain standard temperature, the output of the light receiving element PH in the image sensor 1 when the standard article is present is 1.5.
Suppose that V. In this case, the output of the empty transfer bit is 0.7
Since the voltage is 5V, the output of the setter 6 applied to the adder circuit 5 to obtain the slice level L=IV is determined to be 0.2W. This item is lighter in color than the standard item (this is also a good item)
is sent, and the output of the light receiving element in the image sensor is 3.
Suppose it becomes 5V. At this time, the output of the idle transfer bit is approximately 2V according to Figure 3, but from this point onwards the curve in Figure 2 suddenly dips, and due to slight variations in the elements and slight temperature changes, the output of the idle transfer bit is approximately 2V. It is expected that the output will vary greatly and may reach 3V or more. If it is 3V, the slice level is 3.25V by adding 0.25V to it, and the difference from the output of the light receiving element of 3.5V is only 0.25V, and there is a possibility that the article cannot be detected. Therefore, the comparison circuit 7 is set at a reference level of about 1.2V, with a margin above the 1.5V output of the idle transfer bit when the curve in FIG. 3 starts to curve.
Set to . In this way, it is possible to stably detect objects with a higher degree of texture than the standard object. The imaging type article detection or inspection device of the present invention has the above-mentioned configuration, in which a large number of light receiving elements are arranged, the output of each light receiving element is stored in the corresponding bit of a register, and the memory of this register is shifted to output sequentially. A configuration is used in which the video signal is extracted and the video signal is sliced at an appropriate slice level to obtain the detection signal, and the output of the empty transfer bit of the register described above is used as the temperature compensation signal, so the temperature compensation is performed. Therefore, the number of elements can be reduced compared to using a separate temperature sensing element, and this configuration also has the disadvantage that the detection test of bright objects becomes uncertain if the brightness of the object changes significantly. The thing is,
This problem could be easily solved by simply providing a second comparison circuit.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the outline of the configuration of the image sensor used in the present invention, Fig. 2 is a diagram of a video signal obtained by the above-mentioned element, and Fig. 3 is a diagram of the light-receiving element and empty transfer bit of the register in the above-mentioned element. FIG. 4, which is a diagram showing the interrelationship of outputs, is a block diagram of an embodiment of the present invention. PH... Light receiving element, G... Gate, S
...Shift register. Next 1 Next 2 Figures Next 3 Figures 4

Claims (1)

[Claims] 1 Arrange a large number of light-receiving elements, store their outputs in corresponding bits of a register, shift the memory of the register and take them out sequentially to make a video signal, and slice the video signal according to an appropriate slice level to slice the product or inspect it. Using a configuration in which the signal is used to determine the presence or absence of a target defect, the above register is made to perform a shift operation more times than the number of light receiving elements during one scan to obtain an empty transfer bit output, and this empty transfer bit is output. The transferred bit output is sampled and held at appropriate timing and added to the above slice level as a temperature compensation signal, and the sampled and held value of the same transferred bit output is sent to a comparator circuit and compared with an appropriately set level. An imaging type article detection or inspection device, wherein when the same value exceeds the set level, the signal output from the comparison circuit is also used as a signal for determining the presence or absence of a defect in the article or the object to be inspected.