JPH085193B2 - Wire stroke measuring device for wire dot printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Overview A wire stroke measuring device for a wire dot printer, which can automatically measure a wire stroke of a wire dot printer having pin rows arranged in two stages, is provided. For that purpose, in a wire stroke measuring device of a wire dot printer having a first-stage pin array and a second-stage pin array, a semitransparent thin plate is provided between the first-stage pin array and the second-stage pin array, A first camera for photographing the first illuminating device and the first-stage pin row is provided on one side of the thin plate, and a second camera for photographing the second illuminating device and the second-stage pin row is provided on the other side of the thin plate. And the first and second cameras are connected to the grayscale image processing device,
The first and second lighting devices, the first and second lighting devices are calculated by a computer.
It is configured to control the camera and the grayscale image processing apparatus.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire stroke measuring device for a wire dot printer.

A wire dot printer is one in which a printer head having a plurality of thin wires strikes a platen via a print sheet and an ink ribbon to form a character pattern with a point cloud on the print sheet. Simultaneous copying is possible and the running cost is easy because the type of printing paper is not selected, and it is widely used as an output device for OA equipment and personal computers. Since the print quality of a wire dot printer greatly depends on the stroke of the wire (the distance between the retracted position and the projected position of the wire), whether or not the wire extends within the specified allowable stroke when the printer head is assembled. Needs to be measured.

2. Description of the Related Art As for the structure of the printer head, a 9-pin printer head has been mainly used in the past, but a 24-pin printer head is now used to improve print quality. For 9-pin printer heads, automatic wire stroke measuring devices are currently in use. FIG. 9 shows the pin layout of the 9-pin printer head.
(A) is a top view and (B) is a front view. As shown in FIG. 9, a 9-pin printer head 1 has pins 2 arranged in a line.

Therefore, as shown in the measurement principle diagram of the 9-pin printer head in FIG. 10, the illumination device 3 illuminates the lower part of the pin 2 and the pin 2 is projected from the upper part of the pin by the camera 4 to obtain the image shown in FIG. The image shown in the top view of FIG. Then, this image is processed by the 9-pin measuring system employing the binary image processing apparatus shown in FIG. 11 in the procedure shown in FIG. 12 to automatically measure the wire stroke.

In FIG. 11, the print head 1 is attached to the jig 5. The video signal from the camera 4 is a binary image processing device 6
And image processing is performed. The camera image of the camera 4 can be monitored by the monitor 7. A CRT 9, a keyboard 10 and a floppy disk 11 are connected to the binary image processing device 6 via a path 8. Further, a pin driver 13 is connected to the bus 8 via a parallel IO 12, and the pin 2 of the printer head 1 is sequentially driven by the pin driver 13.

Next, the processing procedure of the above-described measurement system will be described with reference to the flowchart in FIG. In FIG. 12, H indicates a processing step using hardware, and S indicates a processing step using software. First, in step 101, the printer head is driven by the pin driver 13 to pin out a predetermined pin 2. This is photographed by the camera 4 (step 102), 2
Binarization is performed by the value image processing device 6 (step 10
3) After cutting out the target pin (step 10
4) Detect the vertical coordinate H ₁ of the pin tip (step 10)
Five).

Next, the pin is retracted (step 106), the retracted pin is photographed by the camera 4 (step 107),
Binarization is performed by the binary image processing device 6 (step 10
8), the vertical coordinate H _{2 of the} pin tip is detected (step 109).
Then in step 110, the pin stroke calculation,
That is, ΔH = H ₂ −H ₁ is calculated, and in step 111, the quality of the pin stroke is determined. That is,
If the pin stroke ΔH is within the predetermined range, it is determined to be acceptable, and if it is not within the predetermined range, it is determined to be unacceptable and the height of the pin is adjusted using a driver or the like (step 112). The processing from step 101 to step 112 is performed from the first pin to the ninth pin, and the automatic measurement of the pin stroke is completed.

Problems to be Solved by the Invention However, the wire stroke measuring system as described above cannot be directly applied to the wire stroke measurement of a 24-pin printer head. The pin arrangement of 24 pins is arranged in two stages with 12 pins as shown in FIG. FIG. 13 (A) is a front view of the printer head 20,
(B) is a top view and (C) is a bottom view. The printer head 20 has 12 pins 21 aligned in a straight line.
The first-stage pin row 22 and the second-stage pin row 24 are arranged in two upper and lower stages.

For this reason, as shown in FIG. 10, when the illumination is applied from below and the upper pin row 22 is projected by the camera 4 from above, the lower pin row 24
There is a problem in that the wire stroke cannot be accurately measured when the lower pin row 24 is measured, because the image becomes a blurred image due to lack of focus. Further, in the image in which the upper pin is not projected, the shadow of the lower pin influences and the tip portion is blurred, so that the contrast cannot be sufficiently obtained and accurate measurement cannot be performed. In addition, the conventional measurement system uses hardware until the image is binarized, but since the cutting of the pin and the detection of the vertical coordinates of the pin tip are performed by software, it takes time to measure. There is a problem of this. In the case of 9 pins, since the number of pins is small, it has been possible to cope with the problem even if it is lengthened on the manufacturing line. However, when the number of pins is 24, the number of pins is large, so that the inspection cannot be performed on the manufacturing line.

For this reason, in the current 24-pin printer heads, humans actually measure wire strokes manually. However, when humans perform measurement, there is a problem that measurement cannot be performed for all pins because it takes time, and the measurement accuracy is not very good.

The present invention has been made in view of the above circumstances, and an object of the present invention is to measure the wire stroke of a wire dot printer in which the pin rows are arranged in two stages, which is capable of automatically measuring the wire stroke. It is to provide a device.

Means for Solving the Problems FIG. 1 is a diagram of the measurement principle of the present invention, and FIG. 2 is a diagram of FIG. The printer head 20 has a first-stage pin row 22.
And a second stage pin row 24, and a semitransparent thin plate 28 is provided between the first stage pin row 22 and the second stage pin row 24. A first illumination device 30 and a first camera 32 that affects the first-stage pin row are provided on one side of the thin plate 28, and a second illumination device 34 and the second-stage pin row are imaged on the other side of the thin plate 28. A second camera 36 is provided.

As the image processing apparatus, a grayscale image processing apparatus that can execute image difference, convolution, horizontal projection distribution (histogram), etc. at high speed using hardware is adopted. Further, by using a computer such as a personal computer (hereinafter referred to as a personal computer), the first and second lighting devices 30, 3
4, the first and second cameras 32 and 36, and the grayscale image processing apparatus are controlled. In the illustrated principle diagram, the first lighting device 30 includes an upper lighting 30a and a lower lighting 30b, and a second lighting device 30b.
The illuminator 34 is divided into an upper illuminator 34a and a lower illuminator 34b for the purpose of making the illumination uniform, and the present invention is not limited to this configuration of the illuminator.

Action Multi-pin heads such as 24-pin printer heads have 2 pins
Since it is divided into stages, the first camera 32 is used to capture the pin image of the first stage pin row 22, and the second camera 36 is used to capture the pin image of the second stage pin row 24. For example, 1
When capturing an image of each pin 21 of the second row pin row 22, there are the following two methods depending on how the light is applied (the same applies to the second row pin row 24).

First, the first method is by using transmitted light using the second illumination device 34. If the transmitted light is used without using the semi-transparent thin plate, the shadow of the second-stage pin row 24 is affected as described above.
By using this semi-transparent thin plate 28, the second row of pin rows 24
In addition to eliminating the effect of the shadow of the, the background light of the first-stage pin row 22 can be made uniform by allowing the illumination light to pass through the semi-transparent thin plate 28, so that the contrast between the first-stage pin row 22 and the background light can be improved. Greatly improved. As the semitransparent thin plate 28, for example, a white plastic thin plate is used. As a result, the captured pin image has a very good contrast with the background, and accurate measurement is possible.

The second method uses reflected light from the first lighting device 30. Semi-transparent thin plate 28 to the first pin row 22
And the second pin row 24, the influence of the second-stage pin row 24 can be eliminated in the same manner as the first method described above. Moreover, since the background of the first pin row 22 can be made uniform light, an image with a large contrast can be obtained. However, this method is somewhat inferior to the above-mentioned first method using transmitted light, because specular reflection occurs from the pin surface because the light is directly applied to the pin, and the overall contrast is reduced. .

The clear image thus captured is processed by the procedure shown in FIG. FIG. 4 is a schematic diagram showing a change in an image when the processing is performed by the procedure of FIG. In the flowchart of FIG. 3, the pin-out image A is captured in step 202, and the pin-spill image B is captured in step 204. Next, the extended pin portion can be cut out by taking the difference AB between the pinned out image A and the pin retracted image B (step 205). This is binarized with a certain threshold (step 206), and after processing such as isolated point removal is performed, a horizontal projection distribution (histogram) is obtained (step 207) and the extraction points are read (step 208).

Next, in step 209, a certain threshold value is set, and when the number of horizontal images exceeds that value, the end points H ₁ , H
Detect as ₂ . Then, the wire stroke can be measured by multiplying the difference between the end points H ₁ and H ₂ by the length per pixel. The above process is performed for 24 pins one after another, the respective wire strokes are measured, and a pass / fail judgment is made based on the result (step 211). If there is a defect, the pin position is adjusted appropriately in step 212.

EXAMPLES Hereinafter, the present invention will be described in detail based on the examples shown in the drawings.

FIG. 5 is a block diagram of the 24-pin measuring system according to the embodiment of the present invention. The printer head 20 is similar to the principle diagram shown in FIG.
Is attached to a jig (head mount) 26. The printer head 20 is a first-stage pin row 22 composed of 12 pins.
And a second row of pin rows 24 which is also composed of 12 pins. A semi-transparent thin plate 28 such as a white plastic thin plate is provided between the first-stage pin row 22 and the second-stage pin row 24 by using a jig 27. A first lighting device 30 and a first camera 32 for photographing the first-stage pin row 22 are provided on one side of the semitransparent thin plate 28, and a second lighting device is provided on the other side of the semitransparent thin plate 28. The second camera that shoots 34 and the second row of pin rows 24
36 are provided.

The video signals of the cameras 32 and 36 are input to the grayscale image processor 40 and subjected to image processing. The camera images of the cameras 32 and 36 can be monitored by the monitor 42. Reference numeral 44 denotes a personal computer, which is connected to the CRT 48, keyboard 50, and floppy disk 52 via the bus 46. PC
The grayscale image processor 40 is connected to the bus 46 of 44 through a parallel IO (PIO) 54. Gray image processor
The personal computer 40 is controlled via the PIO 54 by the personal computer 44, and data can be read from and written to the personal computer. Switching of the cameras 32 and 36 is controlled by the personal computer 44 via the grayscale image processor 40. Furthermore, a pin driver 58 and lighting devices 30 and 34 are connected to a bus 46 of the personal computer 44 via a parallel IO (PIO) 56. With this configuration, the lighting of the lighting devices 30 and 34 and the insertion / removal of the pins of the printer head 20 are performed by the PC 44 through the PIO5.
Can be controlled via 6.

FIG. 6 is a block diagram of a 24-pin measuring system according to another embodiment of the present invention. In this embodiment, the gray-scale image processor 40 is directly connected to the bus 46 of the personal computer 44, which is shown in FIG. Data can be read and written at a higher speed than in the embodiment. The other structure of FIG. 6 is the same as that of the embodiment shown in FIG.

Using the apparatus having the configuration shown in FIG. 5 or 6, the measurement process is performed according to the procedure shown in FIG. When actually measuring the wire stroke, the projection distribution in the horizontal direction is not taken immediately after the binarization is performed. For example, as shown in FIG. 7, binarization is performed and then processing such as isolated point removal is performed. rear,
An image of only the contour portion of the extended pin is extracted by performing differential processing. This is binarized again, and after processing such as isolated point removal is performed, the projection distribution in the horizontal direction is obtained. The pin stroke length is calculated from this horizontal projection distribution. Regarding the calculation of the respective end points H ₁ and H ₂ , for example, in the case of H ₁ , as shown in FIG. Therefore, a fixed threshold value is provided, and this threshold value detects the coordinates P ₁ and P _{2 at} which the impulse is cut. Here, the threshold is the seventh
It must be greater than 0 shown in FIG. From the P ₁ and P ₂ detected in this way, the end point H ₁ can be obtained using the formula H ₁ =, (P ₁ + P ₂ ) / 2. The end point H ₂ can be similarly obtained.

FIG. 8 shows another convolution processing procedure. FIG. 7 shows that the differential processing is performed only in the vertical direction after binarizing the difference and removing the isolated points. The processing procedure is different. A normal differential image extracts the entire contour of the object, but in the measurement of the wire stroke, since only the vertical contour of the image is necessary information, it is possible to measure only the vertical differentiation. When only the vertical differentiation is performed in this way, when the horizontal projection distribution is taken, only the end points become the impulse-like peaks. The horizontal projection distribution when the normal differentiation process is performed has a distribution between the end points as shown in FIG. 7, and therefore the threshold cannot be set too low. For this reason, when there are variations in peak values, if the threshold value is too high, it may not be possible to detect end points. On the other hand, the projection distribution during vertical differentiation is
Since there is a distribution only for the peak value part of the end point, the threshold value is
It may be set to a certain low value, and the end points can be detected stably.

The difference between the coordinates H ₁ and H ₂ of the end points obtained as described above is obtained, and the difference is multiplied by the length per pixel to obtain the wire stroke, and after 24 pins are measured, the quality is determined.

The method of performing the convolution processing such as the differential image has more processing than the method of only binarization shown in FIG. 4, but since the convolution processing is performed in real time using the grayscale image processor, the time There is little loss.

EFFECTS OF THE INVENTION Since the present invention is configured as described above in detail, there is an effect that the wire stroke of the printer head in which the pin rows are arranged in two stages can be automatically measured at high speed. Therefore, even for a printer head having a large number of pins such as 24 pins, all pins can be automatically measured, and the reliability of the printer head is improved. Further, since uniform measurement can be performed at all times, there is an effect that variations in products can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing the principle of measurement of the present invention, FIG. 2 is a view as seen from the arrow A in FIG. 1, FIG. 3 is a flowchart showing the processing procedure of the present invention, and FIG. 4 shows an example of image processing of the present invention. FIG. 5 is a schematic diagram, FIG. 5 is a block diagram of a 24-pin measurement system according to an embodiment of the present invention, FIG. 6 is a block diagram of a 24-pin measurement system according to another embodiment of the present invention, and FIG. 7 is a diagram showing a processing procedure of convolution. And (A) is a flow chart, and (B) is a processing procedure schematic diagram. FIG. 8 is a diagram showing another convolution processing procedure. FIG. 8A is a flowchart and FIG. 8B is a schematic processing procedure diagram. FIG. 9 is a pin arrangement diagram of a 9-pin printer head,
(A) is a top view and (B) is a front view. FIG. 10 is a measurement principle diagram of a 9-pin printer head, FIG. 11 is a 9-pin measurement system configuration diagram, FIG. 12 is a 9-pin inspection flowchart, and FIG. 13 is a pin arrangement diagram of a 24-pin printer head.
(A) is a front view, (B) is a top view, and (C) is a bottom view. 20 …… Printer head, 21 …… Pin, 22 …… First stage pin row, 24 …… Second stage pin row, 28 …… Semi-transparent thin plate, 30 …… First illumination device, 32 …… First camera , 34 …… Second lighting device, 36 …… Second camera, 40 …… Gray image processor, 44 …… Personal computer.

Claims (1)

[Claims] 1. A wire stroke measuring device for a wire dot printer having a first row pin (22) row and a second row pin row (24), wherein a first row pin row (22) and a second row pin row ( The semi-transparent thin plate (28) is supported by a supporting means so that the semi-transparent thin plate (28) is interposed between the first illuminating device (30) and one side of the thin plate (28). And a first camera (32) for photographing the first-stage pin row, and a second illumination device (34) on the other side of the thin plate (28) and a second camera (36) for photographing the second-stage pin row. And the first and second cameras (32, 36) are connected to the grayscale image processing device (4
0), and by the computer (44) the first and second lighting devices (30,3)
4), a wire stroke measuring device for a wire dot printer, which controls the first and second cameras (32, 36) and the grayscale image processing device (40).