JPH04346305A - Focusing method of vision apparatus - Google Patents

Abstract

PURPOSE:To provide a focusing method for a vision apparatus which dispenses with a device for judging the extent of out-of-focus of a CCD camera besides a vision apparatus and thereby reduces cost. CONSTITUTION:In a vision apparatus provided with a CCD camera 3 for photographing a measured object 2, a binarization means 6 which binarizes an image signal sent from the CCD camera 3, based on a binarization reference value, into binary values of 'having an image' and 'no image', an image memory 7 which stores these binary data and an area calculation means 8 which calculates an image area from the binary data of one frame stored in the image memory 7, focusing adjustment of the CCD camera is performed until the calculated area value reaches its minimum.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for focusing a visual device equipped with a CCD camera.

0002

2. Description of the Related Art A visual device equipped with a CCD camera, for example, images a workpiece with a CCD camera, processes the image of the workpiece, calculates the size of the image, and uses the result of the calculation to detect a moving object. In a visual device used for sorting, etc., whether or not a CCD camera is in focus is determined by a synchro device (synchroscope) 11 or a differentiation circuit 12 and a lamp LED 1, as shown in FIG.
3 is used for discrimination. In the figure, 1 is a light source, 2 is a workpiece W, 3 is a CCD camera, 4 is a visual device body, 5 is an A/D converter, 6 is a comparator, 7 is an image memory, 8 is an area calculation unit, and 9 is a display Section 10A is a binarization reference generation section. Further, 14 is a simple, thin rod-like body such as a pencil.

[0003] When using the synchronizer 11, the CCD
The rod-shaped body 14 is imaged by the camera 3, and the waveform of the image signal is taken into the synchronizer 11 and observed. When the focus is out of focus, the width of the waveform is wider than the waveform when the focus is in focus (shown in B of FIG. 5), as shown in (A) in Figure 5. Determine whether it matches or not. Furthermore, when the differentiator circuit 12 is used, the LED 13 is caused to blink by its differential output, so when the object is out of focus, the blinking speed is slower than when the object is in focus. The reason why the thin rod-like body 14 with a simple shape is used is that when the workpiece 2 has a complicated outline, synchronization with the synchronizer 11 becomes difficult.

0004

As described above, in the conventional method, it is necessary to prepare the synchronizer 11 or the differential circuit 12, the lamp LED 13, etc. separately from the visual device 4, which is not only uneconomical but also , since an image of the rod-shaped body 14 unrelated to the actual workpiece 2 is used, troublesome work such as attachment and detachment of the rod-shaped body 14 is increased.

The present invention has been made to solve this problem, and is a method for focusing a visual device that eliminates the need to prepare a separate device for determining the degree of defocus of a CCD camera. The purpose is to provide a method.

[0006]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a CCD camera that images an object to be measured, and an image signal sent from the CCD camera that is converted into an "image" using a binarized reference value. The visual device is equipped with means for binarizing into two values of "with image" and "no image", and has an area calculation means for calculating the image area from this binary data, and the area value calculated is the minimum value. The focus of the CCD camera is adjusted until the point is reached.

[0007] According to a second aspect of the present invention, the image memory includes an image memory for storing binary data, and an area calculating means for calculating an image area from one frame of binary data stored in the image memory, and the calculated area value is a minimum value. The focus of the CCD camera is adjusted until the value is reached.

[0008] According to the third aspect of the present invention, during focusing, the binarization reference value is set closer to the white level than the steady state binarization reference value.

[0009] According to claim 4, the visual device has a display section,
When focusing, this display section displays the area value as the current focus degree.

According to a fifth aspect of the present invention, when the CCD camera has an automatic focus adjustment mechanism, the visual device is configured to generate a command signal for driving the automatic focus adjustment mechanism based on the area value.

[0011]

[Operation] In the present invention, as the degree of defocus increases, the area of the image increases, so the degree of defocus of the CCD camera is determined from the size of the image area and the focus is adjusted. To calculate this image area, the functions originally provided in the visual device are used.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a light source, 2 is a workpiece W,
3 is a CCD camera. 5 is an A/D converter, 6 is a comparator, 7 is an image memory, 8 is an area calculation section, 9 is a display section, 1
0 is the binarization reference generation part, 10A is the binarization reference value X during operation
10B is a binarization reference generation circuit during focusing that generates a binarization reference value X2 during focusing, and 14A and 14B are reference value changeover switches. During normal operation, turn on the reference value selector switch 14A.
Then, during operation, the binary reference value X1 is given to the comparator 6, and when focusing, the reference value changeover switch 14A is turned on, and the binary reference value X2 is given to the comparator 6 during focusing.

FIG. 2 shows that the CCD camera 2 has one scanning line HN.
(However, N = 1, 2,...N) indicates the image (signal) to be extracted. When the CCD camera 3 is in focus, it becomes image A shown by the broken line, but when the focus is If not, the image becomes a so-called out-of-focus image B shown by a solid line.

The image signal from this scanning line HN is A/
It is converted into a digital value by the D converter 4 and input to the comparator 5. The comparator 5 compares the input value with the binarization reference value X2,
If it is larger than the binarization reference value X2, "1" (image present) is output, and if it is smaller, "0" (image not present) is output. This binary data of "1" and "0" is sequentially written into a predetermined address of the image memory 7. The binarization reference value X2 is set to be closer to the white level than the binarization reference value X1 during driving.

Now, the total number of effective horizontal pixels of the CCD camera 3 is M, and the image A (signal) taken out by the scanning line HN
If the number (number of pixels) of the outputs of the comparator 6 that are "1" (image present) is mN0 (=N-m00), then the image B ( The number (number of pixels) mN of the outputs of the comparator 5 that are "1" for the signal) satisfies mN > mN0.

Therefore, basically, it is possible to determine whether or not the focus is on based on the number of "1"s in the binary data, but it is difficult to determine whether the focus is on based only on the image signal of one scanning line. Since misjudgment is likely to occur due to noise or the like, in this embodiment, binary data of the image signal from all scanning lines HN is used as shown in FIG. That is, from the binary data for one frame stored in the image memory 7, the area calculation unit 8 calculates the area (m1 +m2 +m3 . . . +mN-1 +m
N) is calculated, and the area value S thereof is displayed on the display section 9.

The operator can focus the CCD camera 3 on the workpiece 2 by operating the focus adjustment section of the CCD camera 3 so that the displayed area value S is minimized.

If the CCD camera 3 is equipped with an automatic focus adjustment mechanism, the area value S may be given in the form of a signal as a focus control command to drive the automatic focus adjustment mechanism.

Note that setting the binarization reference value X2 during focusing to be closer to the white level than the binarization reference value X1 during driving is as follows:
This is because the driving binarization reference value X1 is normally set to avoid the vicinity of the rising and falling edges of the image in order to prevent noise. Of course, the binarization reference value during focusing may be set to X3, which is closer to the black level than X1, depending on the brightness of the workpiece 2.

[0021] Furthermore, when the work 2 is of intermediate color,
It is preferable to use a combination of X2 and X3 as the binarization reference value during focusing.

Furthermore, when focusing is completed, the value displayed on the display section 9 at that time is stored in a memory (not shown), and the stored value is displayed on the display section 9 as a reference value at the next time of focusing. You can.

Further, in the above embodiment, the area is calculated by the area calculation section 8 from one frame of binary data stored in the image memory 7, but the output of the comparator 5 is directly used for area calculation by a counter or the like. The area may be calculated by guiding the area to a means.

[0024]

[Effects of the Invention] As explained above, since the present invention utilizes the functions originally provided in the visual device, there is no need to separately prepare a device for focusing the CCD camera, which makes it easier to use than the conventional device. , the price can be lowered, and focusing can be performed using the image of the actual workpiece, reducing the burden on the operator during focusing, making it easy to achieve accurate focusing. becomes.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the above embodiment.

FIG. 3 is a waveform diagram for explaining the operation of the above embodiment.

FIG. 4 is a block diagram for explaining a conventional focusing method.

FIG. 5 is a waveform diagram for explaining a conventional focusing method.

[Explanation of symbols]

1 Light source 2 Work 3 CCD camera 4 Visual device main body 6 Comparator 7 Image memory 8 Area calculation section 9 Display section 10A Binarization reference generation circuit during operation

Claims (5)

[Claims] Claim 1: A CCD camera that images the object to be measured, and an image signal sent by the CCD camera that is converted into a binary standard value.
The visual device is equipped with a means for binarizing into two values of "with image" and "without image", and has an area calculation means for calculating an image area from this binary data, and the calculated area value is a minimum value. A method for focusing a visual device, comprising adjusting the focus of the CCD camera until the CCD camera becomes . [Claim 2] An image memory for storing binary data;
A claim characterized by comprising an area calculation means for calculating an image area from one frame of binary data stored in an image memory, and adjusting the focus of the CCD camera until the calculated area value becomes a minimum value. Section 1. Focusing method of the visual device. 3. The focusing method for a visual device according to claim 1, wherein during focusing, the binarization reference value is set closer to a white level than the steady state binarization reference value. 4. The focus of the visual device according to claim 1, wherein the visual device has a display section, and when focusing, the display section displays an area value as the current focus degree. How to match. 5. When the CCD camera has an automatic focus adjustment mechanism, the visual device generates a command signal for driving the automatic focus adjustment mechanism based on the area value. How to focus the visual apparatus.