KR100281594B1 - Automatic lighting control device for image inspection system and method - Google Patents

Abstract

The present invention is to maintain the robustness to the deterioration of the lighting device or the change of the surrounding environment by the feedback control method according to the time or task scheduling after the initial optimization work such as adjusting the illumination angle, adjusting the ratio of total reflection and diffuse reflection, and adjusting the amount of light of the light source. The present invention relates to an automatic lighting control device of an image inspection system and a method thereof.

In the conventional image inspection system, the lighting unit and the sensor unit are fixed at arbitrary positions according to the lighting unit position and the sensor angle position calculated by many trial and error, and there is a problem in that it cannot cope with environmental changes because the image is inspected.

In order to solve this problem, the present invention provides a light amount detecting unit for detecting the amount of light reflected from an inspection object, a light amount measuring unit for measuring the amount of light detected by the light amount detecting unit and converting the light into a data that can be processed by a computer; In the computing computer for generating a control signal for adjusting the incident angle of the illumination and the sensor angle of the light detection sensor according to the amount of light obtained from the light, and the control signal for adjusting the total reflection and diffuse reflection light quantity and the total reflection and diffuse reflection ratio adjustment control signal, Position control mechanism control unit for adjusting the incident angle of the illumination and the sensor angle of the light detection sensor according to the control signal of the incident light and the sensor angle of the output light, and the total reflection and diffuse reflection of the lighting unit according to the light amount control control signal output from the calculation computer Lighting unit light amount control unit to adjust the amount of light, and to adjust the ratio of total reflection and diffuse reflection And a.

Description

Automatic lighting control device for image inspection system and method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image inspection system, and in particular, after an initial optimization operation such as adjusting an illumination angle, adjusting a total reflection and diffuse reflection, and adjusting an amount of light of a light source is performed initially, a lighting device deteriorates or surrounds with a feedback control method according to time or task scheduling. The present invention relates to an automatic lighting control device of an image inspection system and a method for maintaining robustness against environmental changes.

As shown in FIG. 1, a conventional image inspection system includes an illumination unit 2 for projecting illumination onto an inspection object 1 and a sensor unit 3 for sensing an amount of light reflected from the inspection object 1, have.

The operation of the conventional image inspection system configured as described above will be described with reference to FIG. 2.

First, the conventional image inspection system adjusts the angle of illumination with respect to the target surface in which total reflection occurs, as shown in FIG. 1 of the accompanying drawings, and selects a position where the sum of the amount of light received by the sensor unit 3 is maximized. It is set, and fixed to the inspection device manufacturing.

If the object is composed of different materials, the ratio of total reflection and diffuse reflection according to the ratio table determined by the trial and error method in order to increase the contrast between the parts to be distinguished due to the difference in reflective properties between the materials. The operator adjusts.

In other words, inspect the object by fixing and fixing the lighting angle, the total reflection and the diffuse reflection ratio before the inspection. And when a new model is introduced or the environment of the object to be inspected changes due to the lighting environment of the workplace, dust generation, etc., the inspection is stopped and the operator changes the new lighting parameters manually before working.

However, such a conventional image inspection system uses a fixed angle of the lighting unit and the sensor unit and uses a fixed ratio of total reflection and diffuse reflection so that it is not possible to promptly cope with the degradation of the system caused by deterioration of the entire system or changes in the surrounding environment. Therefore, there is a problem that there is a limit in ensuring stable performance of the system.

In particular, the above-mentioned fundamental limitations are taken into account in the software part, resulting in an increase in the calculation amount of the computing device that processes the sensed image, resulting in a long system execution time.

In addition, a general inspection object is a combination of different dissimilar materials and forms different images according to the type of illumination for forming an image, an illumination angle, a sensing angle, and a ratio of total reflection and diffuse reflection complex lighting. These factors can be found to be optimal when applied independently, but in practical applications these factors work together and include unknown elements that are unpredictable at the level of system development. In addition, as a method of judging when these elements appear in combination, the image unit may determine a combination indicating the maximum value in the CCD device or use current and voltage visualization equipment such as an oscilloscope. However, this is through the CCD elements, and there is a possibility that an error may intervene by targeting the values that have already been converted once, and the judgment is also subjective.

Therefore, due to these various factors, the conventional image inspection system is difficult to select the optimal value caused by using independent fixed values for multivariable adjustment, the possibility of immediate response by the operator and the possibility of operator's involvement, and the optimum. There have been a number of problems such as low reliability, lack of robustness to the environment of use of the device, and lack of information for the user for optimal lighting conditions.

Therefore, the present invention has been proposed to solve all the problems occurring in the conventional image inspection system as described above, and the present invention is performed in the early stages of optimization work such as adjusting the illumination angle, adjusting the ratio of total reflection and diffuse reflection, and adjusting the amount of light of the light source. It is an object of the present invention to provide an automatic lighting control device of an image inspection system and a method for maintaining robustness against deterioration of a lighting device or a change in the surrounding environment by a feedback control method according to time or task scheduling.

Technical means of the present invention for achieving this object, the light amount detecting means for detecting the amount of light reflected from the object to be dried; Light amount measuring means for measuring the amount of light detected by the light amount detecting means, converting the light amount into data which can be processed by a computer, and outputting the light; A computing computer for generating a control signal for adjusting the incident angle of illumination and the sensor angle of the light detection sensor according to the amount of light obtained by the light quantity measuring means, and generating a total reflection and diffuse reflection light quantity adjustment and a total reflection and diffuse reflection ratio adjustment control signal; Position control mechanism control means for adjusting the incidence angle of the illumination and the sensor angle of the light detection sensor according to the incidence angle and sensor angle adjustment control signal of the illumination output from the computing computer; The light amount control means for controlling the total amount of light and total reflection of the lighting unit according to the light amount control control signal output from the calculation computer, and the light amount control means for adjusting the ratio of the total reflection and the diffuse reflection.

The method according to the present invention for achieving the above object comprises the steps of setting the position of the initial illumination and sensor, and measuring the amount of light of the fixed reflection angle while constantly changing the incident angle in the state of setting the initial illumination value; Measuring the amount of light at a fixed angle of incidence while constantly changing the reflection angle; Selecting an optimal total reflection position candidate point according to the two measured amounts of light; Measuring the amount of light while adjusting the ratio of total reflection and diffuse reflection at the optimal total reflection position candidate point, and optimizing an optimal incident angle, a sensor angle, a ratio of total reflection and diffuse reflection; Perform the inspection under the optimized lighting conditions, measure the quantity of light during the inspection and if the deviation is out of the specified deviation, adjust the quantity of light, adjust the ratio of total reflection and diffuse reflection, and change the sensor angle in order to optimize the lighting conditions. Characterized in that the step consists of performing.

1 is a schematic configuration diagram of a conventional image inspection system.

2 is a flowchart showing an image inspection process of a conventional image inspection system.

3 is a block diagram of the automatic lighting control device of the image inspection system according to the present invention.

4 is a control flowchart showing a method for automatically adjusting illumination of an image inspection system according to the present invention.

5 is a flowchart illustrating a process of determining an incident angle and a reflection angle, and determining total reflection and diffuse reflection in the present invention.

6 is a schematic structural diagram of a mechanism part of the image inspection system in the present invention.

<Explanation of symbols for main parts of drawing>

10: light amount detection unit 20: light amount measurement unit

30: computer for calculation 40: mechanical control unit for position control

50: lighting unit light amount control unit 60: lighting unit

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram of the automatic lighting control device of the image inspection system according to the present invention, and includes a light amount detection unit 10 for detecting an amount of light reflected from an inspection object and a light amount detected by the light amount detection unit 10. The light amount measuring unit 20 converts the data into data that can be processed by the computing computer 30 and outputs the light, and adjusts the incident angle of the illumination and the sensor angle of the light detection sensor according to the light quantity obtained by the light quantity measuring unit 20. A control computer 30 for generating a control signal for generating a control signal and generating a total reflection and diffuse reflection light quantity control and a total reflection and diffuse reflection ratio adjustment control signal, and controlling the incident angle and sensor angle adjustment of the light output from the calculation computer 30. Position control mechanism control unit 40 for adjusting the incident angle of the illumination and the sensor angle of the light detection sensor according to the signal, and the light amount regulator output from the calculation computer 30 According to the signal is adjusted to the amount of light of the total reflection and diffused reflection of the illumination portion 60, and consists of illumination light quantity control section 50 for adjusting the ratio of the total reflection and diffused reflection.

Referring to Figures 3 to 6 attached to the operation and effect of the present invention configured as described above are as follows.

First, as shown in FIG. 4, in the state where the initial illumination unit position and the sensor position are set, and the initial illumination value is set, the light quantity detection unit 10 is controlled while constantly changing the incident angle by controlling the position control mechanism control unit 40. And measures the amount of light of the reflection angle fixed through the light amount measuring unit 20.

Next, the position control mechanism control unit 40 is controlled to measure the amount of light at a fixed incident angle through the light amount detecting unit 10 and the light amount measuring unit 20 while constantly changing the position (reflection angle) of the light quantity detecting sensor. do.

In this way, when the brightness data according to each change in the light quantity detector is obtained, the computing computer 30 performs an algorithm for determining the coefficient values of the total reflection and the diffuse reflection according to the reflection model to determine the coefficient values of the total reflection and the diffuse reflection, After the ratio adjustment data of the diffuse reflection is obtained, the ratio optimization algorithm of the total reflection and the diffuse reflection is performed to optimize the ratio of the total reflection and the diffuse reflection.

Here, the algorithm for determining the ratio of total reflection and diffuse reflection and determining the angle of incidence and the angle of reflection is as shown in FIG. 5.

As shown therein, the light quantity is measured using a light quantity sensor, and is substituted into the light quantity calculation formula. Here, the surface roughness constant is also substituted.

After that, one of the coefficients is fixed, and the other is added to determine the coefficient of minimum error, thereby determining the incident angle and the reflection angle.

Next, the total reflection and the diffuse reflection ratio at which the error is minimized are determined by comparing the amount of light each obtained by constantly changing the total illumination and constantly changing the diffuse reflection, with the design reference value of the object.

By determining the ratio of incidence angle, reflection angle, diffuse reflection, and total reflection in this manner, the lighting conditions are optimized by adjusting the ratio of total reflection and diffuse reflection at each fixed optimal total reflection position candidate point, and adjusting the optimum incident angle and sensor angle. .

The inspection object is inspected in an optimized lighting condition as described above, and the light quantity is continuously measured during the inspection of the inspection object to determine whether the deviation is within a predetermined deviation. As a result of this check, if the deviation is out of the defined deviation, the lighting conditions are manufactured in the order of adjusting the amount of light, adjusting the ratio of total reflection and diffuse reflection, and changing the sensor angle to maintain the optimized lighting conditions at all times.

FIG. 6 shows a mechanism part of the image inspection system in the present invention.

Here, reference numerals 111 and 112 serve to approach the virtual hemisphere 125 as the axis for vertical movement and horizontal movement of the line illumination, and 113 is coupled to the end of the axis for illumination vertical movement 111 and is rotatable. It is an axis of illumination rotation designed to match line illumination to the tangent of the hemisphere.

In addition, 114 is a full-use line illumination, 115 is an inspection object, 116 is a moving hemisphere of the light quantity sensor, 117 is a light quantity sensor to move along the moving hemisphere, and with respect to the tangent of the moving hemisphere The axis for rotating the light quantity sensor to maintain verticality.

In addition, 118 is a light amount sensor for measuring the amount of light, 119 is an effective path of the total reflection light, 120 is a linear camera.

In addition, 121 is a diffused illumination, 123, 124 is a light mirror of the illumination is a half mirror to semi-transparent, semi-reflective because it matches the optical path of the camera.

Referring to the method of controlling the actual lighting using such a device as follows.

First, the position of the linear illumination of the linear camera 120 is controlled on the axis (axis for vertical movement of illumination, axis for horizontal movement of illumination, axis of illumination rotation) for determining the position of illumination. In this way, the reference point located at the center of the line light 114 is located at the tangent of the hemisphere 125 having a constant radius, R, from the center of the line light 114 irradiated to the object 115.

Under constant radius conditions, the line illumination 114 is parallel to axis X (the centerline 126 and the X axis of the line illumination are parallel), and the reference point of the illumination is coincident with the tangent at a point on the imaginary hemisphere 125 having a constant radius. By moving, the incident angle of the line light 114 is changed.

Similarly, the reflection angle, that is, the input angle of the sensor, can be changed.

In this way, the light amount of the fixed reflection angle is measured while the incident angle is constantly changed, and the light amount of the fixed incident angle is measured while the reflection angle is constantly changed, and the amounts of light thus measured are input to the computer 30 for calculation.

At this time, the measurement of the amount of light is converted to a current value using the light amount sensor and transmitted to the computer 30 for calculation.

The computing computer 30 stores the amount of light transmitted until all of the initial values have been transmitted at a predetermined position. The types of information stored here are incident angle, reflection angle, and light amount.

These pieces of information are used to adjust the coefficient value of the following equation which determines the magnitude L _r of the quantity of light.

L _r = K _diff cos θ _i + (K _spec / cos θ _i ) e- ^{(α2 / 2σ2α)}

In the above, θ _i is the angle of incidence, θ _r is the reflection angle, and α is (θ _i + θ _r ) / 2.

In this equation, the measured values are L _r , θ _i and θ _r .

These measurements are used to determine the values of diffuse reflection coefficient K _diff , total reflection coefficient K _spec , and surface roughness σ _α .

The above equation is a nonlinear equation, and it is difficult to find a general solution. Therefore, the meaning of sigma _α represents a surface roughness, so the range can be determined according to the object.

If σ _α is assumed to be a constant, the above equation becomes a linear equation. By using the error minimization method using experimental values, the value of coefficient, K _diff , K _spec , can be calculated.

In this order, the K _diff and K _spec values can be obtained in that the error is minimized by substituting the measured value of the light intensity sensor into the above equation and substituting it in the possible range of σ _α .

Since the above equation is a linear equation, when the maximum value for each term is shown, the light quantity L _r also has the maximum value, and the incidence angle θ _i and the reflection angle θ _r can be obtained. You can get it.

Also, considering the ratios of the two coefficients K _diff and K _spec , the initial ratio of total reflection and diffuse reflection can be obtained.

Experimenting with a range of these calculations can provide a reliable lighting ratio.

Once the lighting ratio is obtained, the optimum lighting conditions can be maintained at all times by performing fine adjustment of the incident angle and the reflection angle and adjusting the total reflection non-reflective ratio.

As described above, the present invention can automatically adjust the illumination of the image inspection object, thereby obtaining a good image, thereby improving the performance of the entire image inspection system.

In addition, the automatic lighting experiments to find the optimal lighting conditions for the image inspection in the set order has the advantage of eliminating the operator's intervention and easy to find the optimal lighting conditions for materials of unknown properties.

In addition, the present invention has the advantage that it is possible to maintain the robustness against environmental changes and to maintain the maintenance because the continuous monitoring and correction of the lighting conditions are made during the operation of the image inspection system.

Claims (2)

An image inspection system comprising: an amount of light detecting means for detecting an amount of light reflected from an object to be inspected; and an amount of light measuring means for measuring the amount of light detected by the light amount detecting means, converting the light amount into data that can be processed by a computer, and outputting the image; The inspection system generates a control signal for adjusting the incident angle of illumination and the sensor angle of the light detection sensor according to the amount of light obtained by the light quantity measuring means, and calculates a total reflection and diffuse reflection light amount adjustment and a total reflection and diffuse reflection ratio adjustment control signal. A computer 30; A position control mechanism controller 40 for adjusting the incident angle of the illumination and the sensor angle of the light detection sensor according to the incident angle and the sensor angle adjustment control signal of the illumination output from the computing computer; An illumination unit light amount control unit 50 is configured to adjust the total reflection and the diffuse reflection light amount of the lighting unit according to the light amount adjustment control signal output from the computing computer, and adjust the ratio of the total reflection and the diffuse reflection, and the position control mechanism includes a peripheral object to be inspected. In order to set the virtual hemisphere 125 and to approach the hemisphere in the horizontal and vertical movement axis of the light for guiding the vertical movement and horizontal movement (111, 112) and the vertical movement axis of illumination 111 Designed to be rotatable and coupled to the end of the auto-adjusting device of the image inspection system, characterized in that consisting of an illumination rotation axis 113 to match the line illumination to the tangent of the hemisphere. Setting the position of the initial illumination and the sensor, measuring the amount of light of the fixed reflection angle while constantly changing the angle of incidence with the initial illumination value set, and measuring the amount of light of the fixed angle of incidence while constantly changing the reflection angle A method of automatically adjusting illumination of an image inspection system, the method comprising: selecting an optimal total reflection position candidate point according to the measured two amounts of light; Measuring the amount of light while adjusting the ratio of total reflection and diffuse reflection at the optimal total reflection position candidate point, and optimizing an optimal incident angle, a sensor angle, a ratio of total reflection and diffuse reflection; Perform the inspection under the optimized lighting conditions, measure the volume during the inspection and if the deviation is out of the specified deviation, adjust the light quantity, adjust the ratio of total reflection and diffuse reflection, and change the sensor angle in order to optimize the lighting conditions. Automatic lighting device of the image inspection system, characterized in that the automatic lighting method of the image inspection system comprising a step of performing.

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