JPS6220093A - Inspecting device for printed character or the like - Google Patents

Abstract

PURPOSE:To generate no fatigue of an eye without dropping the inspection accuracy, by combining a visual inspection and an optical inspection. CONSTITUTION:When executing the learning, at the time of an inspection for correcting a total value of addition of an adding circuit 12 by collating with the naked eye an image of a printed character part drawn on a video surface of a monitor 19 and an image of a printed character part in a standard pattern, a data signal corresponding to a pattern to be inspected is binary-coded, based as a reference on a set digital value in a digital value setting circuit 16 in case when an added value of an adding circuit 13 has coincided with the total value of addition of the adding circuit 12, an equivalent area is corrected automatically in accordance with variable density of the printed character. Further, binary-coding signals which have been read in a memory 18 and 20 are compared successively, by which the pattern to be inspected is inspected by position information. In this way, a result of inspection being extremely similar to an inspection by the naked eye can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to, for example, various electronic parts, various electronic devices, or other various products, or product names and manufacturing company names stamped or printed on name plates attached to these products. This invention relates to an inspection device for printed characters, etc., which inspects whether or not characters or trademarks (hereinafter abbreviated as printed characters) representing the above are clearly stamped or printed, and whether there are typos or omissions.

Conventionally, such inspections have been carried out with the naked eye or by using a photoelectric conversion sensor such as an imaging camera in a television, and binarizing the photoelectric conversion output signal to detect the skin area in a certain area around the printed characters. The total amount of signals corresponding to the printed character portion in the standard pattern is compared with the total amount of signals corresponding to the printed character portion in the pattern to be inspected. Inspection is performed using a device that determines the quality of printed characters based on the ratio.

Problems to be Solved by the Invention In the case of visual inspection, it is impossible to perform a large number of inspections in succession due to fatigue, and the above-mentioned inspection device avoids the following drawbacks. I can't do that.

In other words, when printing or stamping characters etc. continuously using a printing machine or stamping machine, etc., the printing or stamping will be done darker than necessary immediately after replenishing the ink, and as the amount of ink decreases, the printing or stamping will gradually become darker. It is normal for it to become pale.

Figure (a) in Figure 3 shows an example of printed characters,
(B) Figure shows an example of pale printed characters, (C) Figure shows (B) the inverted waveform of the detection output signal of the photoelectric conversion sensor corresponding to the scanning part indicated by the thin horizontal line in the figure, and ( D)
The figure shows the inverted waveform of the detection output signal of the photoelectric conversion sensor corresponding to the scanning part indicated by the thin horizontal line in (B), and the horizontal axes in (C) and (D) indicate the detection position P and each vertical axis. The axis is the gradation value T
However, as is clear from both figures, it is natural that the magnitude of the detection signal differs depending on the density of the printed character, but the rising and falling portions of the signal corresponding to the boundary between the background and the printed character There is a tendency that the lighter the printed character, the gentler the slope of the rising and falling portions. This is due to the detection characteristics of the photoelectric conversion sensor, and is a common phenomenon among currently available photoelectric conversion sensors.

Therefore, the signals shown in Figures () and (D) are binarized using the same reference level, and the digital signal '1°' corresponding to the signal above this reference level is converted into a signal corresponding to the printed character part. If we calculate the total number of digital signals "1°" within a certain range around the printed characters by using the digital signal "0°" corresponding to the signal below the reference level as the signal corresponding to the stratum, we can find that the printed characters are pale. Since the total number of digital signals "1 II" becomes smaller, all printed characters that are lighter or darker than the standard pattern are considered defective products, and the results are significantly different from the inspection results with the naked eye.

By varying the reference level for binarization up and down according to the shading of printed characters in the pattern to be inspected,
Although it is possible to expand the range of non-defective products, there is no way to grasp the relationship between the shading of printed characters and the fluctuation range of the standard level, so there is no choice but to set the fluctuation range of the standard level completely appropriately. When the width is expanded too much, there is a risk that defective products may be considered good products, and it is impossible to obtain results equivalent to inspection with the naked eye.

Furthermore, when printing or stamping characters, etc. using a printing machine, stamping machine, or manually, if the background is uneven, the type surface will not be pressed uniformly to the background even if there is no unevenness on the background. In such cases, or in cases where dust or the like is present between the background and the typeface, a portion of the printed characters may be missing. By simply calculating the total number of signals corresponding to the area of a part, it is impossible to distinguish between cases where the printed characters are pale and cases where there is a missing part of the printed characters, and it is impossible to distinguish between a case where the printed characters are pale or a part of the printed characters is missing. There is a risk of incorrectly determining that the product is good.

Means for Solving Problems, Embodiment FIG. 1 is a block diagram showing an embodiment of the present invention.
2 is a light source, and 2 is a photoelectric conversion sensor configured to scan an imaging plane and sequentially send out electrical signals of a size corresponding to the darkness of the image, for example, like an imaging camera in a television. Consists of. In addition, a sensor that can exhibit the same effect as such a sensor, for example, a sensor that scans the subject 28 with the optical axis of an optical lens and sends out an electrical signal of a size according to the amount of incident light, or a sensor that scans the subject 28 with the optical axis of an optical lens, or An optical lens system is fixedly provided so as to be able to receive light from the light source 1, and the light emitted by the light source 1 is formed into a beam shape, and the object 28 is scanned by this beam ray, and the size is adjusted according to the amount of incident light. A sensor configured to send out an electrical signal may also be used. Note that although the figure shows an example of a configuration in which the reflected light from the subject 28 is made to enter the photoelectric conversion sensor 2, the present invention may also be implemented in a configuration in which transmitted light is made to enter the photoelectric conversion sensor 2 depending on the material of the subject 28. It can be implemented. 3 is an analog-to-digital conversion circuit;
Reference numeral 4 denotes a gradation image memory which reads the output digital signal of the analog-to-digital conversion circuit 3 and stores it at an address corresponding to the pixel distribution pattern of the subject. 5 is a gate circuit; 6 is a gradation value distribution calculation circuit; for example, a plurality of digital comparison circuits 71 to 7° (n is any positive integer);
, pulse counters 81 to 8n provided for each comparison circuit, and a cathode ray oscilloscope 9. It should be noted that the number of gradation values that can be expressed according to the number of bits of the output digital signal of the analog-to-digital conversion circuit 3 is made to match the number of comparison circuits 71 to 7n, and the comparison reference digital values of each comparison circuit are made to be different from each other. It is closed. (For example, when the digital output signal has an 8-bit configuration, the comparator circuit 7
Select 256 numbers from 1 to 7n. ) 10 is a scanning type closed circuit which sequentially selectively closes each output circuit of the pulse counters 81 to 8n every time an opening/closing control pulse signal is applied. ” is a changeover switch, 12 and 13 are addition circuits,
■4 is a digital comparison circuit, 15 is a z value conversion circuit, 16
is a digital value setting circuit, the binarization circuit 15 is made up of, for example, a digital type comparison circuit, and the digital value setting circuit 16 is made up of, for example, a pulse counter;
The value conversion circuit 15 compares the data signal read from the gradation image memory 4 with the set digital value of the digital value setting circuit 16, and when the data signal is greater than or equal to the set digital value, the digital signal "t" is set. When the data signal is smaller than the set digital value, a digital signal "°O゛' is sent out. 17 is a changeover switch, 1st is a memory, 18 is a monitor, which consists of a television receiver, and its l frame. A digital signal "1'" and a digital signal "0" read from the memory 18 are introduced in synchronization with the scanning period of . 20 is a memory, 21 is an exclusive OR circuit, 22 is a preset counter, and 23 is an alarm circuit. ,
Reference numeral 24 denotes an object detection sensor, for example, a photoelectric conversion type sensor that receives reflected or transmitted light from the object and sends out an electrical signal, or a magnetic body installed at intervals corresponding to the objects on a belt conveyor that sequentially conveys the objects. It consists of a reed switch, etc. that closes when a piece approaches. Reference numeral 25 denotes a control signal generation circuit, which includes, for example, a clock pulse oscillation circuit, a frequency division circuit for its oscillation output, a switching element for an output circuit in this frequency division circuit, and the like. 26 is a manual operation knob for the switching element of the output circuit in the frequency dividing circuit, and 27 is a manual operation knob for the switching element of the reset/signal sending circuit.

Note that, except for the control signal generation circuit from the control signal generation circuit 25 to the scanning closed quantity circuit 10 and the digital value setting circuit 16, and the detection signal transmission circuit from the subject detection sensor 24 to the control signal generation circuit 25, photoelectric conversion is performed. The illustration of the control signal sending circuit to each necessary circuit after the sensor 2 is omitted.

Switch "changeover switch" and 17 to the contact S side, and select subject 2.
When the standard pattern 8 is selected and placed in front of the photoelectric conversion sensor 2, a detection signal from the object detection sensor 24 is applied to the control signal generation circuit 25 to start it, and the control signal generation circuit 25 outputs a photoelectric conversion sensor. Required control signals are sequentially sent out at required timings to required circuits below the conversion sensor 2.

When a camera similar to an imaging camera in a television is used as the photoelectric conversion sensor 2, the photoelectric conversion sensor 2
When signals synchronized with each other are added as horizontal and vertical synchronization signals to be applied to the analog-to-digital conversion circuit 3, conversion control signals to be applied to the analog-to-digital conversion circuit 3, and read signals to be applied to the gradation image memory 4, the imaging plane of the photoelectric conversion sensor 2 is scanned. The output signal taken out is converted into a digital signal by the analog-to-digital conversion circuit 3, and read into the gradation image memory 4,
The data is stored in correspondence with the pixel distribution pattern of the subject 28.

Next, when a readout start signal is sent to the gradation image memory 4 and at the same time a gate opening/closing control signal is sent to the gate circuit 5, the gate circuit 5 becomes conductive and the gradation image memory 4 is sent to the gradation image memory 4. The data signals stored in the memory 4 are sequentially read out and sent to the gradation value distribution calculation circuit 6 via the gate circuit 5.
A coincidence signal (j) is applied in parallel to the digital comparison circuits 71 to 7n in the pulse counters 81 to 8n, and a coincidence signal (j) is sent from the comparison circuit that matches the comparison reference digital value. The pulses are introduced into a pulse counter corresponding to the comparison circuit and counted.

If the comparison reference digital values of the comparator circuits 71 to 7n are selected to be equal to each other from 71 to 70, for example, then when the final count values of the pulse counters 81 to 8n are introduced into the cathode ray oscilloscope 9, For example, a histogram as shown in FIG. 2 is drawn on the image plane.

In Figure 2, the horizontal axis is the gradation value T, and the vertical axis is the count value C of pulse counters 8I to 8n. In one example, the chevron distribution on the right side of the drawing corresponds to a printed character portion, and the chevron distribution on the left side corresponds to a stratum portion.

When the reading and sending of data signals from the gradation image memory 4 has completed one cycle, the control signal generation circuit 25 sends a repeated readout signal to the gradation image memory 4, and at the same time, a gate opening/closing control signal is sent to the gate circuit 5. The gate circuit 5 is disconnected.

That is, the storage data signals of the zero address to the final address of the image memory with gradation 4 are introduced into the gradation value distribution calculation circuit 6 only once, but the data signals of the image memory with gradation 4 are introduced into the binarization circuit 15. Storage data signals from the zero address to the final address are repeatedly applied.

Next, when the control signal generation circuit 25 repeats the suppression recovery of the manual opening/closing operation knob 26 of the opening/closing element and sends the opening/closing control pulse signal to the scanning type quantity closing circuit 10, the output circuits of the pulse counters 81 to 8n, for example, 8o side is selectively closed sequentially, and each counting signal is sequentially connected to the adding circuit 12 via the scanning type closed circuit lO and the contact S side of the changeover switch.
added to.

The opening/closing control pulse signal from the control signal generation circuit 25 is sent to the scanning type closed circuit 0, and is also introduced into the pulse counter that constitutes the digital value setting circuit IS and is counted, so the counted value increases sequentially from the start of counting. However, the number of additions always matches the number of additions by the adding circuit 12.

On the other hand, the data signals sequentially and repeatedly read out from the gradation image memory 4 are converted into digital signals (
It is compared with the set digital value of the v setting circuit 16, and if the data signal is greater than or equal to the iiQ constant digital value, a digital signal "I" is sent out, and if the data signal is smaller than the set digital value. A digital signal "0pa" is sent to the signal.

The digital signal “1” and the digital signal “O” from the z-value conversion circuit 15 are read into the memo 8 via the contact S side of the changeover switch 17, and are synchronized with the scanning cycle of one frame on the monitor 19. Then, the stored signal in the memory 18 is read out and introduced into the monitor 19.

The digital signal read into the memory 18 is converted into a digital signal "Part of 1 is a digital signal" Q " according to changes in the set digital value of the digital value setting circuit 1B.
In response to this change, the image drawn on the screen of the monitor 18 also changes, gradually approaching the standard pattern.

The image on the screen of the monitor 19 is compared with the standard pattern, and when it is confirmed that they match or almost match, the suppression of the knob 2B in the control signal generation circuit 25 is stopped, and the scanning type quantity closed circuit 10 and Digital value setting circuit 1
6, the digital signal read into the memory 18 will not be updated, and the digital signal "1" stored in the memory 18 will be the same as the distribution pattern of the printed character part in the standard pattern. It will match or almost match.

At this point, except for the standard pattern, change the changeover switch `` and 17 to the contact T side, and send the pattern to be inspected intermittently to the front of the optical/E conversion sensor 2 using a belt conveyor, etc., and the pattern to be inspected will be transferred to the photoelectric conversion sensor. Each time the object comes to rest in front of the subject, a detection signal from the object detection sensor 24 is sent to the control signal generation circuit 25 to start it, and a reset signal sent from the control signal generation circuit 25 calculates the gradation value distribution. The pulse counters 8I to 8o, the scanning closed circuit 10, the addition circuit 13, the digital value setting circuit 16, and the preset counter 22 in the circuit 6 are reset, and then the gradation image memory 4 is reset in exactly the same manner as in the learning process. A digital signal corresponding to the pattern to be inspected is read in, and the stored contents are replaced with those corresponding to the pixel distribution pattern of the pattern to be inspected.

The data signal read out from the image memory with gradation 4 is used to calculate the frequency of each gradation in the gradation value distribution calculation circuit 6 in exactly the same manner as during learning, and then the frequency of each gradation is determined by the automatic opening/closing control pulse signal from the control signal generation circuit 25. When the scanning closed circuit 10 is opened or closed, each count signal of the pulse counters 8I to 8n becomes 8.
From the 0 side, it is sequentially introduced into the adding circuit I3 through the scanning type closed circuit 10 and the contact T side of the changeover switch, and this added count value is stored in the adding circuit 12 in the digital comparing circuit I4. is successively compared with the final counted value of 100, and when the 100 counted values match, a matching signal is sent from the comparison circuit 14 to the control signal generation circuit 25, and from then on, an automatic opening/closing control pulse signal is sent to the scanning type quantity closing circuit 10. At the same time, the transmission of pulses to the pulse counter constituting the digital value setting circuit 1B is also stopped.

On the other hand, the data signal repeatedly read out from the gradation image memory 4 is introduced into the binarization circuit 15, where it is compared with the set digital value of the digital value setting circuit 16, and whether the data signal is larger than the set digital value or If they match, the digital signal ``1'' is sent out, and if the data signal is smaller than the set digital value, the digital signal ``0'' is sent out, and is sent to the memory 2 via the contact T side of the changeover switch 17.
Read to 0.

In this case as well, the digital value setting circuit 16
The memory 20
The memory contents of are updated sequentially, but as mentioned above, in response to the sending of the match signal from the digital comparison circuit 14, the sending of pulses to the digital value setting circuit 18 is stopped and the setting digital value is held constant. When this happens, the contents of the memory 20 will not be updated and will become stable.

After the storage contents of the memory 20 are stabilized, the control signal generation circuit 25
The stored information is sequentially and synchronously read out from the corresponding addresses of the memories 18 and 20 by the read signal sent from the memory 18 and 20, and compared in the exclusive OR circuit 21. If the two signals do not match, a mismatch signal is sent from the circuit 21. A signal is introduced into the preset counter 22, and the alarm circuit 23 is activated by the carry signal sent out when the counted value reaches the preset value.
operates to notify that the pattern to be inspected is a defective product, and further sends out a removal command signal for the defective pattern to be inspected as required. In addition, the preset value of the preset counter 22 is set to 1 appropriately depending on the required inspection accuracy. If particularly high inspection accuracy is required, the preset value is set to zero and exclusive OR is performed. The alarm circuit 23 may be configured to be activated immediately by the first discrepancy signal from the circuit 21.

After completing the inspection of the required number of test patterns by repeating the above steps, when learning another standard pattern,
First, the manual operation knob 27 is pressed to apply a reset signal to the adder circuit 12 to reset it, and thereafter perform the same operation as in the learning time.

In the above example, the digital signals corresponding to the printed character portions are introduced into the adder circuits 12 and 13 and the memories 18 and 20, respectively, but the pulse counters 81 to 8n
The count output signals from the pulse counter (8+ in the above example) on the lower side (dark side) of the gradation value are sequentially sent out, and the comparison result in the binarization circuit 15 is sent to the digital value setting circuit. When the data signal from the gradation image memory 4 is smaller than the set digital value of 18, or when the two match, the digital signal "1 II is sent out,
The present invention may also be applied to a configuration in which the digital signal +40'' is sent out when the data signal is larger than the set digital value, and signals corresponding to the stratum portion are introduced into the adder circuits 12 and 13 and the memories 18 and 20, respectively. can be carried out.

Further, instead of the oscilloscope 9, for example, an XY recorder may be used to draw a histogram, and the present invention can be practiced even if these are omitted.

Further, in the above, the gradation value distribution calculation circuit 6 is replaced by a plurality of digital comparison circuits 71 to 7n, A) a response counter 81
8n to 8n and a cathode ray oscilloscope 9,
Although the case where the value converting circuit 15 is configured with a digital comparison circuit and the digital value setting circuit 16 is configured with a pulse counter has been illustrated, both of them exhibit the same effect and can achieve the object of the present invention. If necessary, it may be configured with other suitable circuits known in the art, and in addition, an adder circuit 12.13, a memo 8.20, a digital comparison circuit 14, an exclusive OR circuit 21, and a preset counter 22. The present invention can also be carried out by having a combination or lZ-tor operate the control signal generating circuit 25 and the like.

Effects of the Invention In the present invention, during learning, the image of the printed character portion (or background portion) drawn on the image screen of the monitor 19 is compared with the image of the printed character portion (or background portion) in the standard pattern with the naked eye. to correct the added total value of the adding circuit 12, and at the time of inspection, the pattern to be inspected is set based on the set digital value in the digital value setting circuit 16 when the added value of the adding circuit 13 matches the added total value of the adding circuit 12. Since it is configured to binarize the corresponding data signal, the equivalent area of the printed characters is automatically corrected according to the e-lightness of the printed characters in the pattern to be inspected, and the thickness of the printed characters can be adjusted accordingly. z, which is always made to almost equivalently match the thickness of printed characters in the standard pattern, and is further read into the memories 18 and 20.
By sequentially comparing the digitized signals, the pattern to be inspected can be inspected using positional information, so abnormalities in the darkness or lightness of printed characters, the presence or absence of missing parts, typographical errors, or omissions can be accurately determined. With this, it is possible to obtain test results that are extremely close to those obtained with the naked eye, and i1! ! JIF is capable of automatically inspecting patterns consisting of any combination of colors, not just black and white, as well as combinations of colors between skin and printed characters.

In addition, inspection accuracy can be increased arbitrarily by scanning the object more closely, increasing the number of bits of the output digital signal of the analog-to-digital conversion circuit 3, and adapting the configuration of each digital circuit to this number of bits. It has the following features and has great practical effects.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
The figure is a waveform diagram for explaining its operation, and FIG. 3 is a waveform diagram for explaining the operation of the conventional device. 1: Light source, 2: Photoelectric conversion sensor, 3: Analog-to-digital conversion circuit, 4: ”
)3' Adjustment image memory, 5: Gate circuit, 6: Gradation value distribution calculation circuit, 71 to 7n and 14: Digital comparison circuit, 81 to 1: Pulse counter, 9: Cathode ray oscilloscope, 10: Scanning type 17: changeover switch, 12 and 13: addition circuit, 15: binarization circuit, 18: digital value setting circuit, 18 and 20: memory, 19: monitor, 21: exclusive OR circuit, 22: nib reset counter; 23: alarm circuit; 24: subject detection sensor; 25: control signal generation circuit; 26 and 27: manual opening/closing operation knobs for opening/closing elements; 28: subject.

Claims (4)

[Claims] (1) A photoelectric conversion sensor that scans a certain range of a subject and sends out an electrical signal according to its gradation; an analog-to-digital conversion circuit that converts the output analog signal of this photoelectric conversion sensor into a digital signal; an image memory with gradation for storing the output signal of the analog-to-digital conversion circuit in correspondence with the pixel distribution pattern of the object; and a gradation for calculating the frequency of each gradation value of the data signal read from the image memory with gradation. a tone value distribution calculation circuit, and when the subject is a standard pattern, each tone value in the range from the highest tone value to an appropriate tone value among the frequencies for each tone value determined by the tone value distribution calculation circuit; a first addition circuit that adds and stores the frequencies of a second addition circuit that starts and performs addition until the addition value reaches the addition value of the first addition circuit; and when the subject is a standard pattern, a digital value corresponding to the number of additions of the first addition circuit; and when the object is a pattern to be inspected, a digital value setting circuit that sets a digital value according to the number of additions of the second addition circuit; It compares with the set digital value of the digital value setting circuit, and when the data signal is larger than or coincides with the set digital value, a digital signal "1" is sent out, and when the data signal is smaller than the set digital value, the digital signal is sent out. a binarization circuit that sends out a signal "0"; a first memory that reads an output digital signal of the binarization circuit when the subject is a standard pattern; and a digital signal read out from the first memory. a monitor consisting of a television receiver, a second memory for reading the output digital signal of the binarization circuit when the object is a pattern to be inspected, and a second memory for reading the output digital signal from the first and second memory; Inspection of printed characters, etc., characterized by comprising an exclusive OR circuit into which the read digital signal is introduced, and a circuit that determines the quality of the pattern to be inspected based on the mismatch signal sent from the exclusive OR circuit. Device. (2) The first addition circuit adds and stores the frequency of each tone value in the range from the lowest tone value to an appropriate tone value among the frequencies for each tone value found in the tone value distribution calculation circuit. , second
The adding circuit starts adding from the frequency of the lowest tone value among the frequencies for each tone value found in the tone value distribution calculation circuit, and continues adding until the added value reaches the added value of the first adding circuit. The binarization circuit sends out a digital signal "1" when the data signal read from the gradation image memory is smaller than or equal to the set digital value of the digital value setting circuit, and the data signal is set as the set digital value. An apparatus for inspecting printed characters, etc., according to claim 1, each of which is configured to send out a digital signal "0" when the value is greater than the value. (3) a gradation value distribution calculation circuit is connected to a plurality of digital comparison circuits to which the data signals read from the gradation image memory are applied in parallel, each having different comparison reference digital values;
2. The apparatus for inspecting printed characters, etc. according to claim 1, comprising a plurality of pulse counters provided corresponding to each comparison circuit and counting the coincidence signals sent out from each corresponding comparison circuit. (4) The printing system according to claim 1, wherein the binarization circuit comprises a digital comparison circuit, and the digital value setting circuit comprises a pulse counter to which addition control pulses of the first and second adder circuits are applied. Inspection device for characters, etc.