JPH09304034A - Lighting control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable setting of the optimum lighting conditions without skill to obtain a higher contrast image by calculating contrast values of an image taken under respective lighting conditions a plurality of times to set light conditions with the highest contrast value. SOLUTION: A detection area on an image of an object to be measured shown on a CRT display is specified by a mouse to be inputted into a CPU 35. The CPU 35 provides a command to a lighting control section 39 to photograph the object to be measured with a CCD camera, while increasing the quantity of illumination light at a specified pitch and performs an A/D conversion 31 of the image taken to be stored into a multi-valued image memory 32 as pixel comprising a number of gray level values. Then, a processing is performed to calculate a contrast value in a specified area from a gray level value pixel unit the altering of the quantity of light ends. The results are stored into a work memory 37. Then, after the end of altering the quantity of light, a contract curve is determined as obtained when the quantity of illumination light is changed. A function higher than second order is plotted to the curve by least square to set lighting conditions to maximize the contrast value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact image measuring device for performing image processing such as shape measurement by performing image processing on an image of an object to be measured picked up by an image pickup means,
In particular, it relates to a system for optimally setting the illumination condition at the time of edge detection.

[0002]

2. Description of the Related Art Conventionally, in this type of non-contact image measurement system, in order to detect an edge position reliably and accurately, a captured image is displayed on a monitor so that the contrast of this image becomes high while observing this image. In addition, the operator has sequentially changed and set the illumination light amount, the direction, and the like. If this setting is not suitable, the contrast near the edge may be low and the edge itself may not appear in the image. Even under the illumination conditions that are optimally set for edge detection, the contrast and brightness of the image will change over time due to the aging of the lamp and the influence of ambient light, and under certain conditions. Image measurement is difficult and it is necessary to constantly adjust lighting conditions.

[0003]

As described above, the work of adjusting and setting the illumination conditions such as the light intensity and direction of the illumination so as to obtain an image with high contrast requires a skilled person's experience and is extremely difficult. Moreover, it was a complicated task.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a system for adjusting and setting illumination conditions so that an image with high contrast can be obtained.

[0005]

In order to achieve the above-mentioned object, the present invention provides an illumination means for illuminating an object to be measured, an imaging means for imaging an object to be measured illuminated by this illumination means, and an imaging means for this imaging. An AD converter for converting the image picked up by the means into a gray value, a multivalued image memory for temporarily storing the gray value output from the AD converter as a gray value of pixels arranged in a matrix, and this multivalued image memory. A CPU that calculates the contrast value by squaring the difference in gray value between each pixel of the value image memory and the pixel adjacent to this pixel, and sends an illumination control command for changing the illumination condition at a predetermined pitch, and this illumination control An illumination control unit for inputting a command to drive and control the illumination unit, and the CPU calculates the contrast value of the image captured by the imaging unit under each illumination condition and Processing performed a plurality of times, and sets the highest contrast value lighting conditions.

In addition to the above means, the present invention can also be configured by including an area designating means for displaying an image temporarily stored in the multivalued image memory on a CRT display and designating an arbitrary area. is there.

Further, the present invention is characterized in that the illumination condition in the above means is an amount of illumination light emitted from the illumination means, a distance between the illumination means and an object to be measured, or a set angle of the illumination means. It is also possible to configure.

In addition to the above-mentioned means, the present invention calculates the contrast value of the image picked up by the image pickup means under each illumination condition, performs this processing a plurality of times, and uses a least square method to calculate a function of quadratic or higher order. Can be applied to set the illumination condition with the highest contrast value.

In addition to the above-mentioned means, the present invention calculates the contrast value of the image picked up by the image pickup means under each illumination condition and performs this processing a plurality of times to calculate the center of gravity, thereby obtaining the most contrast value. It is also possible to set so that a high illumination condition is set.

According to the present invention, an image is taken in while changing illumination conditions in predetermined steps, a contrast value of each image is calculated to obtain a contrast curve, and a quadratic or higher function is fitted to this by a least square method, or a center of gravity is applied. It is possible to automatically find and set the illumination condition that maximizes the contrast value.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In all the drawings, components denoted by the same reference numerals represent the same components. FIG. 1 is a perspective view showing the overall configuration of a non-contact image measuring system according to an embodiment of the present invention. This system includes a non-contact image measuring type three-dimensional measuring machine 1, a computer system 2 that drives and controls the three-dimensional measuring machine 1 and executes necessary data processing, and a printer 3 that prints out measurement results. It is configured.

The coordinate measuring machine 1 is configured as follows. That is, a measurement table 13 on which a work 12 is placed is mounted on the gantry 11.
3 is driven in the X and Y axis directions by an X and Y axis drive mechanism (not shown). A support arm 14 extending upward is fixed to a rear end portion of the gantry 11, and a Z-axis drive unit 1 having a Z-axis drive mechanism is provided above the support arm 14.
5 is attached. A CCD camera 18 for image pickup is mounted inside the Z-axis drive unit 15 so as to face the measurement table 13. This CCD camera 18
Can be driven and controlled in a direction perpendicular to the measurement table 13. A ring-shaped illumination device 19 for illuminating the object to be measured is provided at the lower end of the Z-axis drive unit 15, and the measurement table 13 is independent of the CCD camera 18.
The drive can be controlled in a direction perpendicular to. Further, light is guided from the illumination light source device 16 having a lamp inside to the ring-shaped illumination device 18 by a glass fiber. The power supply device 17 supplies power to the coordinate measuring machine 1 and the illumination light source device 16. In this way, the illumination light source device 1
By separating 6 and this power supply device 17 from the coordinate measuring machine 1, the adverse effect on the measurement accuracy due to heat is prevented.

The computer system 2 comprises a computer main body 21, a keyboard 22, a joystick box 23, a mouse 24 and a CRT display 25. The computer main body 21 is configured, for example, as shown in FIG. That is, CCD camera 1
The image information input from 8 is stored in the multi-valued image memory 32 via the AD conversion unit 31. Multi-valued image memory 32
The multi-valued image information stored in is displayed on the CRT display 25 via the display control unit 33. On the other hand, mouse 2
The position information on the image input from 4 is I / F3.
4 is input to the CPU 35. The CPU 35 executes image processing according to the program stored in the program memory 36. The work memory 37 provides a work area for various processes in the CPU 35. Further, a control command is sent to the illumination control unit 39 to control the amount of lamp light inside the illumination light source device 16 and the vertical position of the ring-shaped illumination device 19. The storage device 38 stores a measurement operation procedure including measurement results and various parameters, and is configured by a hard disk device or the like.

Next, the procedure for setting the optimum light amount in the non-contact image measuring system configured as described above will be described. FIG. 3 is a flowchart showing an optimum light amount setting process for edge detection of the system, and FIGS. 4 and 5 are graphs showing a change in contrast value when the illumination light amount is changed to explain this process. .

First, in step S1, the mouse 24 designates, for example, a rectangular area so as to include a portion on the image of the object to be measured displayed on the CRT display 25 where edge detection is to be performed. The shape of the region that can be designated is not limited to a rectangular shape, but may be a circular shape or a fan shape. It is also possible to use the entire image as it is without specifying the area.

Next, in step S2, a control command is sent to the illumination control unit 39 to increase the illumination light amount at a predetermined pitch, and the illumination light amount is set. More specifically, the amount of illumination light can be set by increasing or decreasing the voltage value applied to the lamp inside the illumination light source device 16 at a predetermined pitch.

Next, in step S3, the image is taken from the CCD camera 18 and temporarily stored in the multi-valued image memory 32. This multi-valued image is formed from gray values in the range of 0 to 255 in a large number of pixels arranged in a matrix of the CCD camera 18.

Next, in step S4, the contrast value in the designated area on the image designated by the mouse 24 is calculated. There are various methods for calculating the contrast value, but the following method is the most general. For example, using the conceptual diagram of the multi-valued image memory 32 in FIG. 6,
The contrast value SE in E is 8 neighboring pixels A,
The gray value a at B, C, D, E, F, G, H, I,
Using b, c, d, e, f, g, h, i, for example, it can be obtained by the following calculation formula.

SE = (e−a) ² + (e−b) ² + (e−c) ² + (e−d) ² + (e−f) ² + (e−g) ² + (e− h) ² + (e-i) ² (1)

The calculation of (1) is performed for all the pixels in the designated area designated in step S1, and all the obtained values are summed up. In this way, it is possible to obtain the contrast value of the designated area in the illumination light amount set in step S2. Further, in order to increase the speed, for example, the following calculation formula may be simply used.

SE = (e−b) ² + (e−d) ² + (e−f) ² + (e−h) ² (2)

Any calculation formula other than the calculation formulas (1) and (2) can be used as long as the contrast value can be calculated. The information of the illumination light amount set in step S2, for example, the command information used when the illumination light amount is set, and the contrast value in the designated area obtained by the equation (1) or (2) are paired with each other. It is temporarily stored in the memory 37.

Next, in step S5, it is checked whether or not the change of the light amount is all completed. If not completed, the process returns to step S2, and if completed, the process proceeds to step S6.

Next, in step S6, a graph as shown in FIG. 4 is obtained from the information obtained by the processing so far. Next, a function of degree 2 or higher is applied to this graph by the method of least squares. For example, a quadratic function as shown in FIG. 5 can be applied. The illumination light amount at the maximum value of the fitted function is the illumination light amount for obtaining the image with the highest contrast value.

The position of the maximum value can be specified by calculating the center of gravity in this graph in addition to using the function of the second or higher order, and the amount of illumination light at this position can be easily obtained. Therefore, in the next step S7, the illumination light amount obtained here can be set as the optimum light amount.

As described above, the optimum amount of illumination light was obtained by gradually changing the amount of illumination light from dark to light at a predetermined pitch, but conversely, even if the amount of illumination light is changed from light to dark, it is also optimal. It is possible to obtain various illumination light amount values. It is also possible to combine both. In that case, the predetermined pitch when changing the illumination light amount from dark to light is made coarse, and the most suitable illumination light amount is obtained in advance, and then the predetermined pitch is made finer in the vicinity of this illumination light amount. It is also possible to change the illumination light amount toward darkness to obtain the optimum illumination light amount. Further, the same effect as changing the amount of illumination light can be obtained by moving the illumination device such as the ring-shaped illumination device 19 to change the distance to the DUT 12.

Although the present invention has been described above with reference to the preferred embodiments, the present invention is not limited to these embodiments, and modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the adjustment setting of the illumination light amount is limited, but instead of this, the height position of the illumination device may be adjusted and set. In this case, it is possible to obtain the same graph as in FIG. 4 by keeping the illumination light amount constant and calculating the contrast value in the designated area every time the height position of the illumination device is moved at a predetermined pitch. Therefore, it is possible to determine the height position of the illuminating device so that the contrast value becomes the highest as well.

Further, instead of the height position of the lighting device, the angle of the lighting device can be similarly adjusted and set. Further, it is possible to combine any one of the amount of illumination light, the height position of the illuminating device, and the angle of the illuminating device, or use all of them. In addition, when the lighting device has a plurality of lighting members that can be individually designated to be turned on, one or more of these lighting members are turned on, the contrast value at that time is calculated, and the most contrast value is calculated. It is also possible to set the lighting pattern of the illumination member when it is high.

[0029]

According to the present invention, even an unskilled person can set optimum illumination conditions for obtaining a high-contrast image. Further, even if the lamp is aged or the ambient light is changed, the illumination condition can be automatically and optimally set, and it is possible to compensate for the image contrast reduction due to the insufficient or excessive light amount of the illumination.

[Brief description of drawings]

FIG. 1 is a perspective view showing an overall configuration of a non-contact image measuring system according to the present invention.

FIG. 2 is a block diagram of a computer system according to the present invention.

FIG. 3 is a flowchart showing a procedure of optimizing an illumination light amount according to the present invention.

FIG. 4 is a contrast value in a designated area when the amount of illumination light is changed.

5 is a quadratic function fitted to the graph of FIG.

FIG. 6 is a conceptual diagram of a multi-valued image memory according to the present invention.

[Explanation of symbols]

 1 Non-contact image measuring 3D measuring machine 2 Computer system 3 Printer 11 Frame 12 Workpiece 13 Measuring table 14 Support arm 15 Z-axis drive unit 16 Illumination light source device 17 Power supply device 18 CCD camera 19 Ring-shaped illumination device 21 Computer body 22 Keyboard 23 Joystick Box 24 Mouse 25 CRT Display

Claims (7)

[Claims] 1. An illuminating means for illuminating an object to be measured, an image capturing means for capturing an image of an object to be measured illuminated by the illuminating means, and an AD conversion section for converting an image captured by the image capturing means into a gray value. A multivalued image memory for temporarily storing the grayscale values output from the AD conversion unit as the grayscale values of pixels arranged in a matrix, and the grayscale of each pixel of the multivalued image memory and a pixel adjacent to this pixel. A CPU that sends a lighting control command that changes a lighting condition at a predetermined pitch by calculating a contrast value by squaring the difference between the values, and a lighting control unit that inputs the lighting control command to drive and control the lighting means. The CPU calculates the contrast value of the image picked up by the image pickup means under each illumination condition and performs this process a plurality of times to obtain the illumination with the highest contrast value. A lighting control system characterized by setting conditions. 2. An illuminating means for illuminating an object to be measured, an image capturing means for capturing an image of an object to be measured illuminated by the illuminating means, and an AD conversion section for converting an image captured by the image capturing means into a gray value. A multivalued image memory for temporarily storing the grayscale values output from the AD converter as the grayscale values of pixels arranged in a matrix, and displaying the image temporarily stored in the multivalued image memory on a CRT display. An area designating means for designating an arbitrary area, and a contrast value is calculated by squaring the difference in gray value between each pixel in the designated area and a pixel adjacent to this pixel, and an illumination condition is set at a predetermined pitch. A CPU for sending a lighting control command to be changed and a lighting control unit for driving and controlling the lighting means by inputting the lighting control command are provided, and the CPU is under each lighting condition. Lighting control system, wherein a serial performed a plurality of times this process to calculate the contrast value of the image captured by the imaging means, for setting the highest contrast value lighting conditions. 3. The illumination control system according to claim 1, wherein the illumination condition is an amount of illumination light emitted from the illumination means. 4. The illumination control system according to claim 1, wherein the illumination condition is a distance between the illumination means and an object to be measured. 5. The lighting control system according to claim 1, wherein the lighting condition is a set angle of a lighting unit. 6. The CPU according to claim 1,
Calculates the contrast value of the image picked up by the image pickup means under each lighting condition, performs this processing a plurality of times, and applies a quadratic or higher function by the least square method to determine the lighting condition with the highest contrast value. Lighting control system characterized by setting. 7. The CPU according to claim 1 or 2,
Is characterized by calculating the contrast value of the image picked up by the image pickup means under each lighting condition and performing this process a plurality of times to set the lighting condition having the highest contrast value by calculating the center of gravity. Lighting control system.