JP2757890B2 - Light intensity adjustment device in optical inspection - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light amount adjusting device for optical measurement, and more particularly to a light amount adjusting device suitably used when comparing a reflected light amount pattern from an article with a reference pattern. Related to the device.
Such a light amount adjusting device is effectively used particularly in an optical inspection device which determines the presence or absence of a defect by detecting the appearance of a flat article such as an electronic component lead frame material, a printed matter or other shapes, scratches, dirt, and the like. .

[Problems to be Solved by the Related Art and the Invention] Conventionally, appearance inspections of various articles have often been performed visually by an operator using the naked eye or an optical microscope in some cases. However, such a visual inspection has the disadvantage that the judgment varies depending on the operator, and even if the operator is the same, the judgment varies depending on the working conditions, and the operator is tired. Further, the inspection speed cannot be improved. was there.

Then, in recent years, the automation of the inspection has been required. This automatic inspection consists of comparing a reference pattern with a pattern to be inspected and detecting a difference between the patterns. Although such an automatic inspection can be applied to the inspection of a three-dimensional article, in reality, the automatic inspection of a three-dimensional article is quite difficult, and particularly a flat article (an article which can be considered as a substantially flat pattern). For example, it can be most suitably applied to inspection of electronic component lead frame materials and printed matter.

In order to obtain the pattern to be inspected, an image is taken by a camera, and an area sensor camera or a line sensor camera can be used as the camera. When an area sensor camera is used, a memory of all pixels is required for a pattern to be inspected, but there is an advantage that imaging can be performed at a time. When a line sensor camera is used, scanning means is required, but there is an advantage that the number of memories is small and comparison can be performed in parallel with scanning, which is efficient.

By the way, in such an automatic inspection, even if it is the same kind of inspected object, the surface reflection is not always the same, and if the surface treatment state is slightly different or the material is different, the same illumination state is obtained. Even in this case, the amount of reflected light is different for each article to be inspected.

The above-mentioned reference pattern is generally obtained by imaging a reference inspected article under standard illumination. In the case of an inspected article having a surface reflection state different from that of the reference inspected article, the standard illumination is used. Even when the inspection is performed below, the reflected light amount is different as described above, so that a pixel is often determined to be a defective portion depending on the pixel.

Therefore, using a charge storage type sensor such as a CCD as a sensor, a light amount signal of a part of the inspected article is obtained in advance at a standard scanning speed, and this is compared with a light amount signal of a corresponding part of the reference pattern. It is conceivable to set the scanning speed so that an appropriate light amount signal is obtained based on the comparison result.

However, in this method, in the case of an inspected article having a small surface reflection, the scanning speed may be slow and the processing speed may be extremely reduced. In the case of an inspected article having a large surface reflection, the scanning speed may be extremely low. The comparison may not be able to catch up early. When the scanning speed is changed for each article to be inspected, it tends to be difficult to smoothly connect to the preceding and following processes.

Therefore, the present invention has been made in view of the above-mentioned problems of the prior art, and provides a light amount adjusting device capable of appropriately comparing a reference pattern with a reference pattern in a certain period of time, regardless of the surface reflection state of an inspected article. It is intended to provide.

[Means for Solving the Problems] According to the present invention, in order to achieve the object as described above, an image of an article to be inspected is scanned at a uniform speed while being formed on an optical sensor, and the sensor is appropriately scanned from the sensor. A signal is output at the timing of obtaining the pixel light amount signal of the image pattern of the inspected article, and the signal is compared with the corresponding pixel light amount signal of the previously stored reference image pattern, and the difference is detected. An apparatus for adjusting the amount of imaging light used in optical measurement for determining the quality of an article to be inspected, comprising: means for controlling the amount of illumination light of the article to be inspected; and at least a part of a surface portion of the article to be inspected. A light amount signal obtained from the optical sensor by image formation is compared with a light amount signal of a reference pattern portion corresponding to the surface portion, and an appropriate illumination light amount is set for the illumination light amount control means based on the comparison result. Means for issuing a command to cause the illumination light quantity control means to guide the light emitted from the light source to the article to be inspected after passing the light emitted from the light source through the polarizer and then the analyzer, and the polarizer and the analyzer Is controlled relative to the amount of light passing therethrough, the relative rotation between the polarizer and the analyzer is performed by a servo motor,
A command to set an appropriate illumination light amount to the illumination light amount control means is issued to a driver of the servo motor, and a polarizer and an analyzer for obtaining the appropriate illumination light amount by the servo motor based on the instruction are issued. A light amount adjusting device for optical inspection, characterized in that a relative rotation angle is realized.

EXAMPLES Hereinafter, specific examples of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a light amount adjusting device according to the present invention.

In FIG. 1, reference numeral 2 denotes an article to be inspected, and in this embodiment, a lead frame material is used. The lead frame material is obtained by forming a plurality of lead frame patterns by performing patterning by etching a copper or iron plate. The lead frame material is disposed horizontally on the table 4 (that is, in the xy plane).

Reference numeral 12 denotes a line sensor camera, and in this embodiment, a CCD line sensor 14 is used as a sensor. The direction of the line sensor is the y direction. 16 is a line sensor camera
There are 12 imaging lenses.

Reference numeral 18 denotes a light source for illumination, and reference numeral 20 denotes a reflecting mirror attached to the light source.

Reference numeral 22 denotes illumination light amount control means, the details of which are shown in FIG. In FIG. 2, 24 is an inner sleeve, 26 is an outer sleeve, and these are bearings 28.
Are connected so as to be relatively rotatable in the circumferential direction. A polarizer 30 is mounted in the inner sleeve 24, and an analyzer 32 is mounted in the outer sleeve 26. A gear 34 is formed on the outer periphery of the outer sleeve 26. On the other hand, reference numeral 36 denotes a servomotor, and a gear 38 that meshes with the gear 34 is attached to a rotary shaft thereof.

In FIG. 1, reference numeral 40 denotes a light guide, the details of which are shown in FIG. In FIG. 3, reference numeral 42 denotes an optical fiber bundle whose end on the light incident side is bundled in a circular shape by a holding ring 44 and whose end on the light emitting side is a holding member 46.
Are arranged in a line.

As shown in FIG. 1, the light source 18, the light amount control means 22
The inner sleeve 24 and the motor 36, and the holding ring 44 of the light guide 40 are fixed to a common support member 48, and the light emitted from the light source 18 emits the light from the polarizer 30, then the analyzer.
The light passes through 32 and enters the light incident side end of the light guide 40. As shown in FIG. 3, the optical fiber bundle 42 is aligned in the y direction at the light exit side end of the light guide 40, and the light emitted from the light exit side end is connected to the lead frame material. The light is reflected by the light source 2 and enters the line sensor camera 12.

In FIG. 1, reference numeral 50 denotes the output of the line sensor camera 12.
This is a converter for A / D conversion, and the output of the converter is input to the CPU 52. Reference numeral 54 denotes a memory in which a reference pattern is stored. 56 is the light amount control means
It is a motor driver for driving 22 motors 36,
The driver is controlled by the CPU 52.

Although only one line sensor camera is shown in the drawing, similar cameras are actually arranged in a similar posture at appropriate intervals in the y direction.

Such inspection of the lead frame material itself is described in, for example, JP-A-63-15141 and JP-A-63-15380.

FIG. 4 is a diagram for explaining the operation of the light amount control means.

The light incident on the polarizer 30 from the light source side becomes linearly polarized light, exits the polarizer, and enters the analyzer 32. When the analyzer has the same directionality as the polarizer 30 (when the rotation angle is 0 degree), the incident light exits from the analyzer without attenuation. Then, as the rotation angle is increased, the analyzer 32 gradually increases.
The amount of light passing through is reduced, and the light does not pass at all at a rotation angle of 90 degrees. Relationship between the rotation angle θ and the amount transmittance of such analyzer 32 becomes like FIG. 4, therefore in advance, as desired standard illumination of the lead frame material when the transmittance p ₂ is made setting the emission intensity of the light source (the rotation angle of the analyzer at that time is theta _2), for example, the rotation angle in the case of obtaining the transmittance p ₁ in order to increase the amount of illumination light theta ₁ Tosureba well, it is sufficient to the rotation angle and theta ₃ in case of obtaining the transmittance p ₃ in order to reduce the amount of illumination light.

FIG. 5 is a view showing an optical correspondence between the lead frame material 2 and the line sensor 14 of the camera 12. As shown in FIG. Where 14 '
Is a line sensor image projected on the surface of the lead frame material 2. At the time of inspection, the camera 12 and the illumination system move integrally in the x direction. As a result, 14 'moves at a constant speed V in the x direction. .

FIG. 6 is a flowchart for explaining the operation of the present embodiment apparatus. Hereinafter, the operation will be described with reference to FIG. 6 while referring to FIGS.

First, the operation is started (START) with the lead frame material 2 positioned and fixed at a predetermined position on the table 4 as shown in FIG.

First, the camera 12 and the illumination system are integrally moved to a predetermined position in the x direction by a drive mechanism (not shown) (ST
1). The predetermined position is a position where 14 'comes to the edge 2a of the lead frame material 2, as shown in FIG. In this position, all the light receiving elements of the sensor 14 correspond to the uniform surface of the lead frame material.

Next, the rotation angle θ of the analyzer 32 of the illumination light amount control means 22 is set to a standard value (ST2). The standard value is the theta ₂ of FIG. 4, for example.

Next, imaging is performed by the camera 12 for a certain period of time (ST
3). That is, the amount of charge (light amount signal) accumulated in each light receiving element of the line sensor 14 within the above-mentioned fixed time is taken out, and each pixel signal is digitized by the A / D converter 50 and input to the CPU 52. . Here, an averaging process of all pixel signals is performed (ST4), and the result is stored in the memory 54. Each pixel signal of the reference pattern is stored in the memory, and the signal of each pixel of the portion corresponding to the above 14 '(all of them are the same and M is called) is compared with the above m. (ST5) to obtain (m−M).

Next, it is determined whether or not | m−M | is within the allowable range (ST6). Here, if it is determined that it is out of the allowable range,
According to (m−M), the analyzer 32 is rotated based on the characteristics shown in FIG. 4 so as to obtain a desired change in transmittance (ST).
7). For example, to reduce the rotation angle theta to theta ₁ if (m-M) increases the negative in transmittance p _1, (m-M)
Is positive and the transmittance is reduced to p ₃ , the rotation angle is increased to θ ₃ . Next, the above ST3 and subsequent steps are executed.

On the other hand, when it is determined in the above ST6 that it is within the allowable range, the analyzer rotation angle θ is determined to the value at that time (ST6).
8) The light amount adjustment operation ends (END).

In the above embodiment, since the plurality of pixel signals are averaged in ST4, even if there is a partial defect at the edge portion of the inspection lead frame material, the influence on the determination of the appropriate illumination light amount is obtained. It is sufficiently reduced.

In the above embodiment, the output signals of all the light receiving elements of the line sensor are used. However, this is not always necessary, and the number of light receiving elements to be used can be determined as appropriate.

Of course, it goes without saying that the present invention can also be applied to inspection of articles other than the lead frame material.

[Effects of the Invention] As described above, according to the light quantity adjusting device of the present invention, any object to be inspected with a simple configuration and with a surface reflection state of almost no increase in the memory capacity of the inspection device. The comparison with the reference pattern can be properly performed in a fixed time. In other words, the processing speed does not decrease in the case of the inspected article having a small surface reflection, and the comparison determination cannot be overtaken in the case of the inspected article having a large surface reflection. Since the scanning speed is not changed for each article to be inspected, a smooth connection with the preceding and following processes is possible.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a light quantity adjusting device according to the present invention. FIG. 2 is a detailed view of the illumination light amount control means. FIG. 3 is a detailed view of the light guide. FIG. 4 is a diagram for explaining the operation of the light amount control means. FIG. 5 is a diagram showing an optical correspondence between a lead frame material and a line sensor of a camera. FIG. 6 is a flowchart for explaining the operation of the apparatus of the present invention. 2: Lead frame material, 4: Table, 12: Line sensor camera, 14: Line sensor, 18: Light source, 22: Light intensity control means, 30: Polarizer, 32: Analyzer, 36: Motor, 40: Light guide, 42: optical fiber bundle, 48: support member.

Claims (2)

(57) [Claims] 1. An image of an article to be inspected is scanned at a uniform speed while being formed on an optical sensor, and a signal is output from the sensor at an appropriate timing to obtain a pixel light quantity signal of an image pattern of the article to be inspected. Comparing the signal with a pixel light quantity signal corresponding to a previously stored reference image pattern, and detecting the difference to adjust the imaging light quantity used in the optical measurement for judging the quality of the article to be inspected. An apparatus, comprising: means for controlling the amount of illumination light of the article to be inspected; a light quantity signal obtained from an optical sensor by imaging at least a part of the surface of the article to be inspected; and a reference pattern corresponding to the surface. Means for performing a comparison with the light amount signal of the portion and issuing a command for setting an appropriate illumination light amount to the illumination light amount control means based on the result of the comparison. Led to the article to be inspected side Luo emitted light after passing through the polarizer then the analyzer,
The light amount is controlled by rotating the polarizer and the analyzer relatively, and the relative rotation between the polarizer and the analyzer is performed by a servomotor, and the rotation of the A command to set an appropriate illumination light amount is issued to the driver of the servo motor,
A light amount adjusting device in an optical inspection, wherein a relative rotation angle between a polarizer and an analyzer for obtaining the appropriate amount of illumination light by the servo motor based on the command is realized. 2. An average of pixel light quantity signals obtained from a plurality of light receiving elements of an optical sensor, and comparing the average value with an average value of light quantity signals of a plurality of pixels corresponding to a reference pattern. The light amount adjusting device according to claim 1, wherein the light amount is adjusted.