KR100939679B1 - Apparatus and method for adjusting the focus automatically - Google Patents

Abstract

The present invention uses the distance between the laser spots as the primary means as the auto focusing means, and the shape of the laser spot is adopted as the secondary means, so that it is flexible to the problem of pattern influence and diffuse reflection which may be generated by the test specimen. It is possible to provide an autofocus control device capable of performing autofocus control in correspondence, and enabling accurate autofocus control by using length data calculated based on accurately measured coordinate values as the first focus control means.

The auto focusing apparatus according to the present invention is an optical system consisting of a laser light output unit, a collimating lens, a pinhole, a diffraction grating, a condenser lens, a light splitter, an objective lens, a cylindrical lens, and a light detector, and a laser beam spot detected by the light detector. An arithmetic device for reading the shape and the distance between the spots; A storage medium which stores a distance distance value (reference value) between spots when focus is achieved; A control device for controlling the distance between the shape and the spot at the time of focus by comparing the distance between the shape and the spot detected when loading a new test specimen to the reference value stored in the storage medium; And a drive motor driven according to the control signal by the control device.

Auto focus

Description

Auto focusing device and its method {APPARATUS AND METHOD FOR ADJUSTING THE FOCUS AUTOMATICALLY}

The present invention relates to an autofocus control apparatus and method that can be automatically attached to an optical device such as a microscope or used alone as an apparatus, and more specifically, a laser beam emitted from a laser light source unit. Three laser beam spots detected in the photodetector by dividing the light into a plurality of light rays through a diffraction grating and reflecting the light rays on the test specimen, and then randomly generating astigmatism on the reflected light beam and inputting the photodetector to the photodetector. The present invention relates to an auto focusing apparatus and a method for performing auto focusing by measuring a distance between spots and a shape of a spot.

A device that automatically adjusts the focus in a non-contact manner is used in CDP (Compact Disk Player) or Video Disk Player. The auto focusing device used in CDP or the like uses a laser beam to split the laser beam through a diffraction grating, and then irradiates the back of the CD using a polarizing prism and inputs the laser beam reflected therefrom back into the photo detector. Focus adjustment was performed through one laser beam spot collected at the light detector.

That is, in the conventional focusing method used in the CDP or the like, one laser beam spot is formed on the photodetector, and then the auto focus adjustment is performed by determining whether the formed spot shape is circular. In the case of the CDP, since the laser beam is irradiated to the back side of the CD having a good flatness and a uniform surface, the shape of the light reflected therefrom can be used to focus relatively accurately. However, when the auto focusing method described above was applied to a sample having a pattern such as an LCD panel, the focusing was not easy due to the interference caused by the diffuse reflection and the pattern. When inspecting a patterned LCD panel, it is necessary to automatically adjust the correct focus before the inspection. When the above method applied to the CDP is applied, irregular reflection is severely generated by the pattern formed on the LCD panel, and thus the shape of the spot is very uneven. It may be formed on the photo detector in a state of incomplete or incomplete, it is difficult to adjust the auto focus or there is a problem that the reliability is lowered.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to use the distance between laser spots as the primary means as the auto focusing means, and the shape of the laser spot is employed as the secondary means. By providing two kinds of focus adjustment means as described above, it is possible to flexibly respond to the pattern influence and diffuse reflection problem that can be generated by the test specimen, and to perform auto focus adjustment, based on the accurately measured coordinate values. It is an object of the present invention to provide an autofocus control apparatus and method capable of more accurate autofocus adjustment by using the calculated length data as the primary focus adjustment means.

The automatic focusing device according to the present invention for achieving the above object is to automatically focus by adjusting the focal length in a non-contact manner by reading the laser light reflected on the test specimen using a laser beam of the laser light output unit from the optical detector An apparatus for providing a light source, comprising: a laser light output unit for outputting a circular laser beam capable of adjusting a light amount; A collimating lens for focusing the output laser beam and outputting the parallel laser beam; A pinhole for reducing the size of parallel rays; A diffraction grating for dividing the emitted laser into a plurality of light rays; A focusing lens for injecting the divided light beam into the effective aperture of the objective lens; A beam splitter for injecting a light beam passing through the condenser lens into the specimen and sending a light beam reflected back to the specimen to the light detector; An objective lens for magnifying and observing the specimen; A cylindrical lens for arbitrarily generating astigmatism in the light beam from the light splitter to the light detector; A convex lens for collecting the light passing through the cylindrical lens to an area of a photo detector; A photo detector through which the laser light finally enters through the lenses; An arithmetic device for reading the shape of the laser beam spot detected by the light detector and the distance between the spots; A storage medium which stores a distance value (reference value) between spots when focus is achieved; A control device for controlling the distance between the shape and the spot at the time of focusing by comparing the distance between the shape and the spot detected when the test specimen is loaded with the reference value stored in the storage medium; And a drive motor driven according to the control signal by the control device.

According to the auto focusing device and the method according to the present invention, by using the length data calculated based on the accurately measured coordinate values as the primary focusing means, more accurate autofocusing is possible, By employing two factors as a means for achieving this, there is a remarkable effect that it is possible to flexibly cope with pattern influences and diffuse reflection problems that may be generated by the test specimen and to perform auto focus adjustment.

Hereinafter, with reference to the accompanying drawings, the specific content for the practice of the present invention will be described in detail.

1 is a schematic view showing the configuration of an auto focusing device according to the present invention.

Referring to FIG. 1, the auto focusing apparatus 120 according to the present invention condenses a laser beam output unit 10 that outputs a circular laser beam capable of adjusting the amount of light, and outputs a parallel beam by condensing the output laser beam. The collimating lens 20, the pinhole 30 for reducing the size of parallel rays, the diffraction grating 40 for dividing the emitted laser into three rays, and the divided rays of the objective aperture. A light splitter for injecting the light condenser lens 50 and the light beams passing through the light condenser lens 50 into the specimen 80 and for transmitting the light beam reflected back to the specimen 80 to the photodetector 110. 60, an objective lens 70 for magnifying and observing the specimen 80, cylindrical lenses 90 and 91 for generating astigmatism randomly on the light beams output from the optical splitter 60, and the cylinder Light passing through the lenses 90 and 91 is directed to the area of the photo detector 110. Very it is constructed to include a light detector 110 that is a laser light to reach the final via the convex lens 100 and the lens.

In addition, in the above description, although the diffraction grating 40 in which the incident laser beam is divided into three beams has been described and illustrated, the autofocus control according to the present invention is provided with a diffraction grating for splitting the beam into two or more than four beams. Of course it can also achieve the purpose of.

In the auto focusing apparatus 120 according to the present invention, the laser light generated from the laser light source unit 10 is emitted as a diverging beam rather than a collimated beam. Therefore, in front of the laser light source unit 10, a collimating lens 20 for condensing a laser beam and outputting the same as a parallel beam should be provided, and for forming a laser beam for more precise focusing and for entering the diffraction grating, The pinhole 30 was further provided in front of the collimation lens 20. Using the pinhole 30 can be arbitrarily adjusted the size of the laser light to be used.

The laser beam converted into parallel light through the above process is divided into three beams (one main beam and two auxiliary beams) by using the diffraction grating 40.

In addition, the beam split through the diffraction grating 40 is configured to reach the objective lens 70 via the condenser lens 50 so that the three divided laser beams can be incident on the effective aperture of the objective lens 70 accurately. To help.

The beam splitter 60 of the auto focusing apparatus 120 according to the present invention injects the light beam passing through the condenser lens 50 to the place where the test specimen 80 is located, and at the same time from the test specimen 80. By reflecting the reflected light back at a right angle to the incident light incident in the direction in which the detector 110 is located.

After reflecting from the test specimen 80, the laser beam reflected through the light splitter 60 in the direction of the light detector 110 is positioned as a cylindrical lens provided between the light detector 110 and the light splitter 60. 90, 91 and the convex lens 100 finally reach the photodetector 110.

The cylindrical lenses 90 and 91 randomly induce astigmatism in the light beams output from the light splitter 60 to perform auto focus adjustment from the spot shape of the laser light reaching the photo detector 110 and the distance between the spots. It is meant for. In the cylindrical lenses 90 and 91, one or two cylindrical lenses are arranged in a line on the path of the laser light.

The light passing through the cylindrical lenses 90 and 91 is collected through the convex lens 100 to the photodetector 110 region and finally forms an image on the photodetector 110.

Looking at the spot of the laser beam formed on the photo detector 110 through the above process in more detail as shown in FIG.

When comparing the unfocused and focused cases, the distance between the spot shape of the detected laser beam and the center point of the spot is different. That is, when the distance from the objective lens 70 to the test specimen 80 is longer than the focal lengths L1, L2, and L3 where the focal points are matched, the distance between the spot center points when the focal point is matched (L4). , L5 and L6 are short, and the shape also appears as an ellipse in the longitudinal direction on the detector 110. In addition, when the distance from the objective lens 70 to the test specimen 80 is shorter than the focal length of the objective lens 70, the distances L7, L8, L9 between the center points of the spots are farther away, and the shape is horizontal. Appears elliptical.

In the conventional auto focusing apparatus, only one spot shape or the direction of the shape formed in the photodetector 110 is used as a means for focusing. The focus control method as described above is vulnerable to the pattern or diffuse reflection of the specimen 80 by focusing on the specimen at a point, so that when the shape of the spot is formed on the photo detector 110 in a very non-uniform or incomplete state, Difficult to adjust the focus or there was a problem that the reliability is lowered.

However, the automatic focusing method according to the present invention can reduce the influence of the pattern or diffuse reflection of the specimen 80 by forming three different focal points on the specimen, so that three laser beam spots are formed on the photo detector 110. Therefore, as well as the shape of the spot, the information on the distance between the center spot spot is also read and calculated and used as a means for auto focus adjustment.

That is, in the auto focus adjusting method according to the present invention, the distance between the laser spot center points is used as the primary means for focusing, and the shape of the laser spot is used as the secondary means.

In more detail, the auto focus adjustment according to the present invention basically performs focus adjustment using at least one or more spot interval distances, and if the laser beam spot is formed on the photo detector 110 under the influence of the test specimen 80, When only one is formed, the distance distance between the spot center points becomes impossible, so in this case, focusing is performed using the shape of the spot as a secondary means.

Therefore, by providing the above two adjusting means, it is possible to flexibly cope with the pattern influence and the diffuse reflection problem that may be generated by the test specimen 80, and the interval length data calculated based on the accurately measured coordinate values. By employing as a primary means for focusing, more accurate auto focusing becomes possible.

In addition, the auto focusing apparatus 120 according to the present invention employs a CCD as the light detector 110. The photo detector refers to a device that detects an optical signal and converts it into an electrical signal having the same information.

CCD (Charge-Coupled Device) is a sensor that converts light into electric charge and obtains an image. It is also called a charge-coupled device. A CCD consists of a circuit in which several capacitors are interconnected in pairs, with each capacitor in the circuit delivering charges charged to the battery around it.

CCD chips are chips that have many photo-diodes. When light is emitted to each photodiode, electrons are generated according to the amount of photons, and the amount of electrons of the photodiode represents the brightness of the light, thereby reconstructing the information to form image information that forms a screen.

In addition, of course, CMOS may be applied to the photo detector instead of the CCD.

Referring to Figure 1 will be described with respect to the auto focus adjustment method according to the present invention. The laser beam emitted at an arbitrary size is converted into a parallel beam focused at a desired size while passing through the collimating lens 20 and the pin hole. The laser beam passes through the transmission diffraction grating 40 to cause a diffraction phenomenon and is divided into three, and enters the light splitter 60 through the condenser lens 50 to match the size of the effective aperture of the objective lens 70. do. The three light beams incident on the light splitter 60 go straight to the objective lens 70, and the light beams incident on the center of the objective lens 70 are reflected by the test specimen 80 and are again reflected by the objective lens 70. Pass through. At this time, the chief ray of the three light beams passes along the optical axis and passes through the center of the effective aperture of the objective lens 70, and the remaining two auxiliary light rays pass through the objective lens 70 effective aperture at a constant angle.

The main and auxiliary beams, which are reflected by the test specimen 80 and then pass through the objective lens 70 and enter the light splitter 60, are output after the traveling direction is reflected by the light splitter 60 by 90 °. .

The three light beams rotated by 90 ° from the optical splitter 60 generate astigmatism by the two cylindrical lenses 90 and 91 and finally reach the photo detector 110, respectively.

Then, the auto focus adjustment according to the present invention is performed through the following process.

First, as shown in FIG. 2 (a), when the test specimen 80 is at a focused distance, the main and auxiliary rays are circular images due to astigmatism caused by the cylindrical lenses 90 and 91. 2 (b) and (c), when the test specimen 80 is at an unfocused distance, an elliptical or straight line image may be displayed and the cylinder may be detected by the photo detector 110. The distance between the lenses 90 and 91 and the photo detector 110 is specified.

That is, when the distance from the objective lens 70 to the test specimen 80 is in the focal point of the objective lens 70 by the above setting, the circular laser beam is detected by the photodetector 110 and is out of focus. Alternatively, the reference image may be set such that a straight ray of light is detected by the photo detector 110.

After this step, when the distance is in focus, i.e., the shape when the laser beam spot represents a circular image and the distance between the spots L1, L2, L3 are read and stored in the storage medium. The shapes and distances L1, L2, L3 stored in the storage medium are used as comparison factors which serve as reference values for auto focusing later. When the distance between the shape or the spot detected by the photo detector 110 is different from the reference value, the motor is controlled to match the stored position and shape, that is, the reference value, so that the camera automatically focuses on the focal length at all times.

The shape and distance of the spot formed on the photo detector 110 are read through the following method.

First, when using the shape of the spot, it is performed by measuring the ratio of the horizontal / vertical length of the square to the rectangle corresponding to the circular or oval formed on the photo detector 110.

That is, when the focus is in focus, a circular spot is formed and the circular spot has a length / length ratio of 1: 1. Therefore, by reading the length ratio of the spot shape formed in the photo detector 110 and driving the motor so that the length ratio is 1: 1 relationship, the auto focus is adjusted by adjusting the distance between the objective lens 70 and the test specimen 80. The adjustment is possible.

Second, when the distance between the spots is used, focusing is performed by calculating a distance between at least two spots and comparing the distance between the spots (reference value) corresponding to the case where the focus is achieved.

In other words, when comparing the case of out of focus with the case of in focus, the distances between the spots of the detected laser beams are different. That is, when the distance from the objective lens 70 to the test specimen 80 is shorter than the focused focal length, the distance between the spots is far greater than that when the focus is focused, and the test specimen 80 from the objective lens 70. The distance between the spots becomes shorter when the distance to () is longer than the focal length of the objective lens 70.

Accordingly, when the coordinate value of the center point of each spot formed when the focus is in focus is calculated and calculated, the distance between the spots is calculated, and the calculated interval length is set as a reference value and stored in the storage medium. Subsequently, each time the loading of the test specimen 80, the distance between the laser beam spots detected is calculated in the same manner as described above, and the motor is driven so that the distance between the spots matches the reference value stored in the storage medium. By adjusting the distance between the 70 and the test specimen 80, auto focus adjustment is possible.

In the case of FIG. 2 (b), the distance between the objective lens and the specimen is located far from the focal point, and the distance between L4 and L5 is larger than that of L1 and L2 when the focal point of FIG. The size is small and the beam shape is elongated up and down. In the case of FIG. 2 (c), the distance between the objective lens and the specimen is located close to the focal point and not close to the focal point. When the focal point of FIG. 2 (a) coincides, the size of L7 and L8 The size is large and the beam shape is elongated from side to side.

In addition, the automatic candle control device 120 according to the present invention further comprises a knife edge (Knife Edge) to form a laser spot having a semi-circular or semi-elliptic shape on the photo detector 110 and from the auto focus from the spot Of course, adjustments can also be made.

In addition, in the above description, although the diffraction grating 40 in which the incident laser beam is divided into three light beams has been described and illustrated, the autofocus control according to the present invention is provided with a diffraction grating for splitting the light into two or more light beams. It is also possible to achieve the purpose, of course, the plurality of spots divided into a number can be arranged in various forms without being arranged in a straight line.

3 is an application state diagram showing a state in which the auto focusing device according to the present invention is applied to an optical device such as a microscope.

The auto focusing apparatus 120 according to the present invention further adds a plurality of light splitters 61, 62, 63, and 64 to the basic components of the present invention shown in FIG. Attached to an optical device such as 200) to perform an auto focusing function. The microscope 200 irradiates the light emitted from the light source to the specimen 80 through the objective lens 70, generates the light reflected from the specimen into an image through a CCD, and then magnifies and visually observes it. Device. In the LCD panel process, the pattern is inspected by a microscope, and when a defective pattern is found, the pattern is removed by laser repair and a new pattern is inserted.

The auto focusing apparatus 120 according to the present invention can be applied to various optical inspection apparatuses as well as silk microscopes. That is, by adding a plurality of light splitters, mirrors, and the like to the basic components of the present invention described in FIG. 1, various modifications may be made by those skilled in the art without departing from the technical spirit of the present invention. It is obvious. Such modified embodiments should not be understood individually from the spirit and scope of the invention, but should fall within the claims appended to the invention.

1 is a schematic view showing the configuration of an auto focusing device according to the present invention;

2 (a), (b) and (c) is a screen output the distance between the laser spot shape and the center point of the spot detected by the optical detector of the autofocus control device according to the present invention.

3 is an application state diagram showing a state in which the auto focusing device according to the present invention is applied to an optical device such as a microscope.

** Description of symbols for the main parts of the drawing **

10 laser output portion 20 collimating lens

30 pinhole 40 diffraction grating

50: condenser lens 60: light splitter

70: objective lens 80: test specimen

90, 91: cylindrical lens 100: convex lens

110: light detector 120: auto focusing device

Claims (7)

In the auto-focus control method of irradiating a laser beam to the test specimen, the laser light reflected from the test specimen is read by a photo detector to automatically adjust the focus by adjusting the focal length in a non-contact manner, Converting a laser beam into a parallel beam, splitting the laser beam converted into the parallel beam into a plurality of laser beams, and passing the split plurality of laser beams through an objective lens to reach an inspection specimen; A second step of receiving a plurality of laser beams reflected from the test specimen to a photo detector to form a plurality of laser spots on the photo detector; In the second step, the distance between the objective lens and the test specimen is adjusted to place the test specimen on the focal point of the objective lens, and at this time, an interval distance between the plurality of laser spots formed on the light detector is calculated, and A third step of setting the interval distance as a reference value and storing the interval distance in a storage medium; A fourth step of performing a process of the first and second steps as new test specimens are loaded so that a plurality of laser spots are formed on the light detector; A fifth step of identifying the shapes of the plurality of laser spots formed on the photodetector by the fourth step, and calculating the distance between the plurality of laser spots; And  The distance adjustment direction between the objective lens and the test specimen is determined using the shapes of the plurality of laser spots identified in the fifth step, and the inspection with the objective lens in the distance adjustment direction is performed so that the calculated distance is consistent with the reference value. And a sixth step of adjusting the distance between the specimens. The method of claim 1, The shape detection of the laser spot performed in the fifth step is performed using a square or a rectangle made by drawing a tangent to the circular or elliptical laser spot formed on the photo detector. In an auto focusing device for irradiating a laser beam to read the laser light reflected on the test specimen from the photodetector to adjust the focal length in a non-contact manner to automatically focus. A laser light output unit configured to output a circular laser beam capable of adjusting the amount of light; A diffraction grating for dividing the emitted laser into a plurality of light rays; An optical splitter for injecting the divided light beams into the specimen and simultaneously sending the reflected light beams back to the photo detector; An objective lens for magnifying and observing the specimen; A cylindrical lens for arbitrarily generating astigmatism in the light beam reflected from the light splitter; A convex lens for collecting the light passing through the cylindrical lens to an area of a photo detector; A photo detector to which laser light is finally input via the lenses; An arithmetic device for reading the shape of the laser beam spot detected by the light detector and the distance between the spots; A storage medium which stores a distance distance value (reference value) between spots when focus is achieved; A control device for controlling the distance between the detected shape and the spot when loading a new test specimen to have a distance between the shape and the spot when in focus by comparing with the reference value stored in the storage medium; And a drive motor driven according to a control signal by the control device. The method of claim 3, wherein Autofocus control, characterized in that it further comprises a collimating lens for condensing the laser beam output between the light output unit and the diffraction grating to output as a parallel beam, and a pinhole for adjusting the size of the parallel beam Device. The method according to claim 3 or 4, And the photodetector uses any one selected from a CCD and a CMOS. The method according to claim 3 or 4, The auto focusing device further comprises a knife edge to form a semi-circle or semi-elliptical laser spot on the light detector. The method according to claim 3 or 4, The cylindrical lens is configured such that two cylindrical lenses are arranged in a row, or one cylindrical lens and one convex lens are arranged in a line to have the same effect.

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