JPS6234114A - Image processor - Google Patents

Abstract

PURPOSE:To automatic a line by moving a camera, finding the standard deviation of the histogram of an input image, and finding the focus position of the camera from the position where the deviation is minimum. CONSTITUTION:The camera 4 which inputs an image of an object 5 is fitted to a Z stage 3 and an elevating/lowering command for the Z stage 3 is supplied to a Z stage driving device 2 from the automatic focus adjusting circuit 1A in a processor 1. An automatic focus adjusting circuit 1A sends a command to the Z-stage driving device 2 so that the camera 4 moves at a constant speed in a focusing direction where a stand-by position where the object 5 is in the visual field and the image is inputted at constant intervals of time after the start of the movement to repeat a process for finding the histogram and calculating the standard deviation; when the current standard deviation exceeds the last standard deviation, the Z-stage driving device 2 is command to stops and return the Z stage 3 to the last image input position, thus performing automatic focus adjusting operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention includes a camera, a stage for moving the camera and focusing it on an object to be image processed, and a driving device for driving the stage. The present invention relates to an image processing device used in inspection lines for micro parts, etc.

[Conventional technology]

When using an image processing device on an inspection line for micro parts,
Enlarge and analyze the image using a microscope or close-up ring.

[Problem that the invention seeks to solve]

In this case, the depth of focus of the lens becomes very short, and even slight variations in parts can blur the image, requiring readjustment of the focus and making it difficult to automate the line.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image processing device that automatically moves a camera to optimally set the focus so that clear images can be captured regardless of variations in the manufacturing of target parts.

[Means for solving problems]

The image processing device of the present invention gives a command to the drive device so that the camera moves at a constant speed from a standby position where the object is within the field of view in a direction in which the camera is in focus, and inputs images at regular intervals after the start of movement. , the process of obtaining a histogram and calculating its standard deviation is repeated, and when the standard deviation calculated this time becomes larger than the standard deviation calculated last time, the drive device is commanded to stop the stage and return the stage to the previous image input position. The present invention is characterized in that it includes an automatic focus adjustment circuit that performs an automatic focus adjustment operation.

[Effect]

FIG. 3 shows an example of a grayscale image input from a camera to an image processing device. FIG. 4 is a histogram corresponding to this image, where the image input signal has a brightness level of 0''-X l1ax
, and the number f of pixels at each brightness level is plotted on the vertical axis. This figure is an example of using transmitted light for illumination, and the brightness of the background is higher than the brightness of the object, and the number of pixels is also large, so the histogram is like this.
When the camera is moved slightly and the focus is shifted, the outline of the object in Figure 3 becomes blurred and the degree of brightness change from the bright level of the background to the dark level of the object becomes gradual, and as a result, the histogram changes as shown in Figure 4. It becomes gradual as shown by the dotted line.

In other words, to focus the camera, all you need to do is find the camera position where the histogram changes most steeply. To do this, focus on one peak in the histogram, assume that the peak is a normal distribution, and find the standard deviation σ. , it is effective to find the camera position that minimizes the standard deviation σ.

In FIG. 4, the separation level of the background side and target side histograms is X min , and the level Xi (i=min~m
ax) is fi, and the number of images included in levels Xm1n to Xmax is n. Also, level Xm1n~X
When fitting a normal distribution using max data, the average level is m9. If the variance is S and the standard deviation is σ, then n = Σ fl 1 # ■ in l profit 1111 n I" + 111 σ = 5 and the standard deviation Find σ.

Note that when the object within the field of view is small (for example, when inspecting the surface of the object for scratches), the portion of the histogram corresponding to the object becomes very small. In this way, if there is an extreme difference in the size of the histogram peaks corresponding to the object and the background, it is necessary to find the standard deviation of the smaller peak.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an embodiment of the image processing apparatus of the present invention, and FIG. 2 is a flowchart showing the processing of the automatic focus adjustment circuit IA in FIG.

A camera 4 that inputs an image of the object 5 is attached to the Z stage 3, and a command to raise/lower the Z stage 3 is given to the Z stage driving device 2 from an automatic focus adjustment circuit LA in the processing device 1.

The automatic focus adjustment circuit IA gives a command to the Z stage driving device 2 so that the camera 4 moves at a constant speed from a standby position where the object 5 is within the field of view in the direction of focus, and at regular intervals after the start of movement. The process of inputting an image, obtaining a histogram, and calculating its standard deviation σ is repeated, and when the standard deviation σ calculated this time becomes larger than the standard deviation σ calculated last time, the Z stage 3 is stopped, and the Z stage 3 is stopped. The automatic focus adjustment operation is performed by instructing the Z stage driving device 2 to return the image to the previous image input position.

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

It is assumed that the camera 4 is initially waiting at a fixed position where the object 5 is within its field of view (step 11).
The initial value of ^ (this is a large value) is set (step 12), and the automatic focus adjustment circuit IA operates the stage drive device 2 so that the Z stage 3 moves at a constant speed from the standby position in the in-focus direction. Give command to (Step 13)
, the moving speed at this time is determined from the image processing speed and the focus search of the camera 4. The previous standard deviation σλ-I is set (step 14), and after the timer time T1 has elapsed (step 15), the automatic focus adjustment circuit IA inputs the image, calculates a histogram in real time, and calculates its standard deviation σ4 using the above formula. (Step 1B), and then compare the standard deviation σi with the standard σ^-1 obtained when inputting the previous image (Step 17). If σj-1≧σλ, return to Step 14 and repeat the same process. If σa−+ <σ4, it means that the previous image input position was optimal, and the automatic focus adjustment circuit IA outputs a command to stop the Z stage 3 to the Z stage driving device 2 (step 18), and the timer time T2 has elapsed. After (step +9), a command to reverse the Z stage 3 (move in the opposite direction) is output to the Z stage driving device 2 (step 20).

After the timer time T3 has elapsed (step 21), a command to stop the Z stage 3 is output to the Z stage driving device 2 (step 22), whereby the camera 4 returns to the previous image input position and the focus adjustment is completed.

〔Effect of the invention〕

As explained above, the present invention moves the camera, determines the standard deviation of the histogram of the input image, and determines the focal position of the camera from the minimum position. This method has the advantage of being able to automatically capture clear images without any problems, automating lines, and being able to be applied to automatic inspection of objects of different heights.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of the image processing apparatus of the present invention, FIG. 2 is a flowchart showing the processing of the automatic focus adjustment circuit IA of FIG. 1, and FIG. FIG. 4 is a diagram showing an example of a gray scale image, and FIG. 4 is a diagram showing a histogram for the image in FIG. 1: Processing device, IA: Automatic focus adjustment circuit, 2: Z stage drive device. 3: Z stage, 4: camera, 5: object. Figure 3 Figure 4 Ming V level)

Claims (1)

[Claims] In an image processing apparatus that includes a camera, a stage for moving the camera to focus on an object to be image processed, and a drive device for driving this stage, the image processing apparatus waits for the object to come within the field of view. A command is given to the drive device so that the camera moves at a constant speed from the position to the direction of focus, and after the start of movement, images are input at fixed intervals, the histogram is calculated, and the standard deviation is calculated.This process is repeated. When the standard deviation calculated is larger than the previously calculated standard deviation, the device is equipped with an automatic focus adjustment circuit that instructs the drive device to stop the stage and return the stage to the previous image input position, thereby performing automatic focus adjustment operation. Characteristic image processing device.