KR101261694B1 - 3d measuring apparatus using coherent and the measuring method thereof - Google Patents

Abstract

The present invention enables to selectively scan white light or monochromatic light using a monochromatic filter and to adjust the height of the optical path of the measurement light to obtain a three-dimensional image using a deaxis hologram method and a height measurement method using white light. The purpose of the present invention is to provide a three-dimensional measuring apparatus using interference characteristics that can overcome the limitation of the measuring speed and the measuring speed.
In addition, the present invention by selecting a light source (monochrome light or white light) according to the height and surface conditions of the object, and by enabling the monochrome filter to be used on / off according to, according to the size and measurement speed of the object to be measured Another object of the present invention is to provide a three-dimensional measuring apparatus using interference characteristics to select and use an appropriate measuring method.

Description

3D measuring apparatus using the interference interference and its measuring method {3D MEASURING APPARATUS USING COHERENT AND THE MEASURING METHOD THEREOF}

The present invention relates to a three-dimensional measuring apparatus using a coherence characteristic and a measuring method thereof, and more specifically, the conventional off-axis method by the on / off operation of the monochromatic filter and the on / off operation of the micro actuator The present invention relates to a three-dimensional measuring apparatus using a coherent characteristic and a measuring method thereof, which make it possible to compensate for the limitation of the measuring height and the slow measuring speed.

In general, a method of obtaining a 3D stereoscopic image of a small object has been widely used for measuring equipment for off-axis illumination using digital holography.

Here, the off-axis illumination method refers to an illumination method that causes light to be incident obliquely, unlike conventional illumination, in which the same shape is formed on a projection lens when exposed through a circular aperture. Such an illumination method is also called an incidence illumination method, and is widely used to measure a three-dimensional image in real time on a fine shape and a structure.

1 is a conceptual diagram showing the configuration of a digital holographic deaxis measurement device using a conventional deaxial illumination method.

The digital holographic off-axis microscope includes a light source unit 10, a beam splitter 20 for dividing the light scanned from the light source unit 10 into reference light and measurement light, and the measurement light and the reference light, respectively. The first mirror 30 and the second mirror 40 to reflect, and the imaging device 50 to obtain the required image by comparing the wavelength of the reflected measurement light and the reference light.

The deaxial measurement apparatus receives the reference light and the measurement light transmitted through the object, and separates the reference light and the measurement light by a digital method to obtain stereoscopic information of the object. Therefore, there is a merit that such stereoscopic information can be obtained in real time. However, since the short wavelength is used, there is a limit in the measurement height of the object (1/4 of the wavelength).

On the other hand, a white light interferometer is widely used as one method for overcoming the constraint on the measurement height.

2 is a schematic diagram schematically showing an example of a measuring apparatus using a conventional white light interferometer.

The white light interference measuring device includes a light source 10 ', a beam splitter 20' that separates the light scanned from the light source into a reference light and a measurement light, a reference mirror 30 'for reflecting the reference light, and a measurement passing through the object. And a measurement mirror 40 'for reflecting light, and an image pickup device 50' for detecting the shape of the object through the reflected reference light and the measurement light.

In particular, the measurement mirror 40 'is provided with a piezo actuator 41 so that the height can be adjusted by a minute unit. The piezo actuator 41 moves in a constant minute unit to obtain an interference fringe. At this time, the interference fringe is obtained by a sinusoidal brightness value, and the interferogram has a shape of a Gaussian function.

When the highest vertex of the measurement displacement section is obtained from the interference fringes thus obtained, the relative distance with the piezo actuator 41 can be obtained for a point of the object, and this value is changed to height displacement and is three-dimensional over the entire acquisition interval of the image. You can get the height.

The white light interferometer thus formed is widely used in nanometer precision shape measurement and surface analysis mainly for micro-patterns. However, there was a problem that a lot of point noise occurs in the three-dimensional measurement image due to the noise or the distortion of the vibration of the piezo actuator when measuring the interference fringe. In addition, the measurement takes a long time because the scan of the height is required in addition to the scan of the entire surface.

The present invention has been made in view of this point, and it is possible to selectively scan the white light or monochromatic light using a monochromatic filter and to adjust the height of the optical path of the measurement light to measure the height using the deaxial hologram method and the white light. It is an object of the present invention to provide a three-dimensional measuring apparatus using a coherent characteristic and a method of measuring the same, by which a three-dimensional image can be obtained using a method, thereby overcoming the limitation of the measuring height and the measuring speed.

In addition, the present invention by selecting a light source (monochrome light or white light) according to the size and surface state of the object, and by using a monochromatic filter on / off according to, according to the size and measurement speed of the object to be measured Another object of the present invention is to provide a three-dimensional measuring apparatus using a coherent characteristic and a measuring method thereof so that an appropriate measuring method can be selected and used.

Three-dimensional measurement apparatus using the interference characteristics according to the present invention for achieving this object, the light source; A monochromatic filter for transmitting light of a predetermined wavelength band from the light generated from the light source; A beam splitter for dividing the light transmitted through the monochromatic filter into reference light and measurement light; A reference light reflecting mirror for reflecting the reference light back to the beam splitter; A measurement light reflection mirror which reflects the measurement light back to the beam splitter and whose height is adjustable; And an image pickup device for detecting an interference between the measurement light reflected by the beam splitter and the reference light and obtaining an image.

In particular, the light source is capable of selectively scanning a short wavelength laser and white light.

In addition, the monochromatic filter is selectively turned on and off, and the monochromatic filter uses a Fabry-Perot type interference filter.

In addition, the measuring light reflecting mirror is further characterized in that the linear actuator type micro actuator driven by an electrostatic type, piezoelectric type, electronic drive type or precision motor for height adjustment. Such a micro actuator is characterized in that the height adjustment is made in a minute unit of 3 ~ 200㎛.

The imaging device may be a solid state image sensing device, a CMOS, or a charge coupled device (CCD).

The measurement apparatus according to the present invention separates the reference light and the measurement light by using a Digital Fourier Transform on the hologram obtained by the off-axis method using a short wavelength laser. A 3D stereoscopic image may be obtained by applying a digital fresnel transform to light.

In addition, when scanning white light, it is characterized in that the peak is detected by scanning while adjusting the height of the measurement light reflection mirror.

On the other hand, in the three-dimensional measurement method using the interference characteristics according to the present invention, when using a short wavelength laser, the monochromatic filter is turned on (ON), the micro actuator of the measurement light reflecting mirror is turned off (OFF), and the monochromatic light beams from the light source After scanning the splitter, the light is divided into the measurement light and the reference light, and the divided reference light and the measurement light are reflected by the beam splitter from the reference light reflecting mirror and the measurement light reflecting mirror, respectively, and the interference between the reflected measuring light and the reference light is detected. An image is obtained from an imaging device.

In addition, another three-dimensional measurement method using the interference characteristics according to the present invention, the monochromatic filter is turned off (OFF), the micro actuator of the measurement light reflecting mirror (ON), the white light from the light source is measured by scanning the beam splitter The light is divided into the reference light and the reference light, and then the divided reference light and the measurement light are reflected by the beam splitter from the reference light reflecting mirror and the measuring light reflecting mirror, respectively, and the interference between the reflected measuring light and the reference light is detected to obtain an image from the image pickup device. It is characterized by.

Finally, another three-dimensional measuring method using the interference characteristics according to the present invention, the monochrome filter is turned on (ON), the micro actuator of the measurement light reflecting mirror (ON), and scanning white light from the light source to the beam splitter And split the divided reference light and the reference light into the beam splitter from the reference light reflecting mirror and the measuring light reflecting mirror, and detect the interference of the reflected measuring light and the reference light to detect the image from the image pickup device. It is characterized by detecting the peak (peak) by high-speed scanning the micro actuator at 3 ~ 99㎛. At this time, the coherent width of the light transmitted through the monochromatic filter is characterized in that 100 ~ 200㎛.

According to the three-dimensional measuring apparatus and its measuring method using the interference characteristics of the present invention has the following effects.

1) 3D image can be obtained by using short wavelength laser or white light according to the size of object. That is, if the object is small, the short wavelength laser which is less affected by the measurement height is used as the light source, and if the object is large, the image is measured using white light, which is advantageous for the measurement height, so that the quality is high in a short time regardless of the object size. Can obtain an image.

2) When measuring, use the light source (white light and short wavelength laser) and measure the peak of the Gaussian distribution generated by scanning the monochromatic filter by turning on the monochromatic filter to have more coherent characteristics than the white light. It overcomes the limitations of the measurement height of the light source and compensates for the limitation of image acquisition due to the scanning speed by white light. This enables the measurement of high steps at a faster rate than white light.

1 is a conceptual diagram showing the configuration of a digital holographic deaxis measurement device using a conventional deaxial illumination method.
2 is a schematic diagram schematically showing an example of a measuring apparatus using a conventional white light interferometer.
Figure 3 is a schematic diagram schematically showing the configuration of the three-dimensional measuring apparatus according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined.

Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention. Therefore, various equivalents It should be understood that water and variations may be present.

(Configuration)

3 is a conceptual diagram schematically showing the configuration of a three-dimensional measuring apparatus according to the present invention.

In the measuring apparatus according to the present invention, the light source selectively scanned from the light source 100 is transmitted to the monochromatic filter 200, and then separated into the reference light and the measurement light in the beam splitter 200, and the reference light reflecting mirror 400. And analyzing the light reflected from the measurement light reflection mirror 500 to obtain a three-dimensional image from the image pickup device 600.

In particular, the light source 100 may selectively scan white light and short wavelengths, and the measurement light reflection mirror 500 may be selectively adjusted in height.

Hereinafter, this configuration will be described in more detail as follows.

The light source 100 typically uses short-wavelength lasers, which are commonly used to obtain images of fine objects, and white light, which is frequently used for height measurement.

Preferably, the light source 100 uses white light, and the white light is converted into white light or monochromatic light according to the on / off operation of the monochromatic filter 200 which will be described later, and scanned by the beam splitter 300. That is, when the monochrome filter 200 is off, the white light is scanned as it is, and when the monochrome filter 200 is on, the monochromatic light is scanned by the beam splitter 300.

In the drawing, reference numeral 110 denotes a parallel light lens that guides the light source scanned by the light source 100 to be scanned in parallel.

The monochromatic filter 200 can be used as long as it is a filter causing interference polarization. Among these filters, in a preferred embodiment of the present invention, a Fabry-Perot type interference filter is used as an example.

In particular, the monochromatic filter 200 is for obtaining monochromatic light having excellent coherence, and in the present invention, a coherent interference width of about 3 to 200 μm is used to secure a wide transfer distance at high speed. Of course, such a coherent interference width can be used even wider than this, but for the measurement of the fine object is used to have such a coherence bandwidth.

In addition, the monochromatic filter 200 may be one that can be selectively turned on / off. This is because the light scanned from the light source 100 is transmitted to the beam splitter 300 by passing through the monochromatic filter 200, so that the transmitted light has a different wavelength.

For example, when the light source 100 scans white light, the white light is transmitted through the monochromatic filter 200, and when the monochromatic filter 200 is off, it is transmitted as white light, and the monochromatic filter 200 is turned on. If it is, it transmits with monochromatic light.

The beam splitter 300 divides the light transmitted through the monochrome filter 200 into reference light and measurement light. At this time, the beam splitter 300 directs the reference light to the reference light reflecting mirror 400 which will be described later without any interference, and directs the measurement light to the measuring light reflecting mirror 500 by transmitting the object.

At this time, the light transmitted through the monochromatic filter 200 becomes white light or monochromatic light according to the on / off operation of the monochromatic filter 200.

The reference light reflection mirror 400 reflects the reference light toward the image pickup device 600 so that the wavelength of the reference light can be obtained by the image pickup device 600 to obtain a 3D image. In this case, the reference light reflection mirror 400 scans the reference light to the image pickup device 600 through the beam splitter 300.

The measurement light reflection mirror 500 reflects the measurement light transmitted through the object toward the imaging device 600. In this case, the measurement light reflection mirror 500 is installed so that the measurement light is scanned to the image pickup device 600 through the beam splitter 300, so that the measurement light and the reference light is scanned side by side in the image pickup device 600.

On the other hand, the measurement light reflecting mirror 500 is further provided with a micro actuator 510 to adjust the height for the optical path difference. The micro actuator 510 is used to measure the height of the measurement object through the step according to the height change while moving up and down. The micro actuator 510 may be any type that can be height-adjusted in small units (for example, 3 to 200 μm).

Examples thereof include electrostatic type, piezoelectric type, electronic drive type, and linear drive type micro actuators driven by a precision motor.

Among these, it is most inexpensive to use the linear actuator type driven by the precision motor as the micro actuator 510.

The imaging device 600 detects the measurement light and the reference light reflected by the beam splitter 300 and obtains a 3D image based on the measurement light.

As the image pickup device 600, a solid state image sensing device, a CMOS, and a charge coupled device (CCD), which are commonly used to acquire a 3D microscopic image based on reference light and measurement light, are used. Can be.

On the other hand, the imaging device 600 obtained the reference light and the measurement light as described above acquires a three-dimensional image as follows.

First, when a short wavelength laser (monochromatic light) is used as a light source (for a finer object), it is used as a digital hologram method using an off-axis method. In this case, the short wavelength laser is separated into a reference light and a measurement light through a digital Fourier transform method. In addition, the reference light and the measured light obtained by the reflection obtain a 3D stereoscopic image by a digital Fresnel transform method.

When the white light is scanned (in the case of a relatively large fine object), the height of the measurement light reflection mirror 500 is adjusted in micro units, that is, for example, about 3 μm. Scan as you adjust. The highest peak among them is detected to obtain a 3D stereoscopic image.

The technique of acquiring a 3D image using such a short wavelength laser and white light is made of a conventional technique, and a detailed description thereof will be omitted.

(How to measure)

In the three-dimensional measuring apparatus according to the present invention, the measuring method varies depending on whether the monochrome filter 200 is turned on or off and whether the micro actuator 510 is driven. That is, the monochromatic filter 200 and the micro actuator 510 operate by the operation as shown in Table 1 below.

division
Monochromatic filter

Micro actuator
compare
One
ON

OFF The light source is monochromatic light
Fixed distance between reference light and reference light
Measurement by digital holography
2
OFF

ON The light source is white light
Changing the light path of the reference light to detect peaks
Same function as the white light scanning interferometer
3
ON

ON The light source is monochromatic light
Changing the light path of the reference light to detect peaks
Monochromatic Coherent Scanning Interferometer

In the above table, it is assumed that the light source scans white light, and the light source scanned by the wavelength change according to the on / off operation of the monochromatic filter 200 is transmitted as monochromatic light or white light. In addition, the peak of the object is detected by changing the length of the optical path of the measurement light according to the operation of the micro actuator 510.

In particular, in the measuring method according to the present invention, in the above table, (Division 1) and (Division 2) are made by the same method as in the prior art.

That is, in the case of (Division 1), it is performed by the conventional technique of performing three-dimensional measurement by holographic method using monochromatic light without changing the optical path.

In the case of (Section 2), the three-dimensional image is detected through the peak detection when the difference between the measurement light and the reference light is the same by scanning white light and adjusting the height difference of the optical path of the measurement light. This measuring method is the same as a conventional white light scanning interferometer.

However, in the measuring method of (Section 3) according to the present invention, it is a kind of monochromatic light scanning interferometer that varies the optical path length of the measurement light while converting white light into monochromatic light.

In particular, since the light source is monochromatic light unlike the white light scanning interferometer (Division 2), the interference increases as much. That is, in the case of the white light scanning interferometer, the interference width is about 3 μm, but the interference width obtained through the monochromatic filter 200 is about 200 μm.

Therefore, the micro actuator 510 can determine the micro movement distance that can be moved at one time within the range of 3 ~ 99㎛. Accordingly, the measurement can be performed at a much faster speed than the fine moving distance (3 to 5 μm) of the white light scanning interferometer. Of course, such a micro-actuator 510 can also be moved in the same manner as the fine movement distance of a white light scanning interferometer.

As described above, the present invention enables the on / off operation of the monochromatic filter and the on / off operation of the micro actuator to be selectively performed, so that not only the same measurement effect as the three interferometer devices can be obtained but also the measurement that the short wavelength laser has The limitation of the height and the measurement speed due to the scan of white light can be eliminated.

100: light source 110: parallel light lens
200: monochrome filter 300: beam splitter
400: reference light reflection mirror 500: measurement light reflection mirror
510: micro actuator 600: image pickup device

Claims (13)

delete delete delete A light source 100;
A monochromatic filter 200 for transmitting light of a predetermined wavelength band from the light generated by the light source 100;
A beam splitter 300 for dividing the light transmitted through the monochromatic filter 200 into reference light and measurement light;
A reference light reflection mirror 400 for reflecting the reference light back to the beam splitter 300;
A measurement light reflection mirror 500 which reflects the measurement light back to the beam splitter 300 and whose height is adjustable; And
And an image pickup device 600 for detecting an interference between the measurement light reflected by the beam splitter 300 and the reference light to obtain an image.
The monochrome filter 200 is used to selectively turn on / off,
The monochromatic filter 200 is a three-dimensional measurement apparatus using the interference characteristics, characterized in that the Fabry-Perot type interference filter.
delete delete delete A light source 100;
A monochromatic filter 200 for transmitting light of a predetermined wavelength band from the light generated by the light source 100;
A beam splitter 300 for dividing the light transmitted through the monochromatic filter 200 into reference light and measurement light;
A reference light reflection mirror 400 for reflecting the reference light back to the beam splitter 300;
A measurement light reflection mirror 500 which reflects the measurement light back to the beam splitter 300 and whose height is adjustable; And
An imaging device 600 for detecting an interference between the measurement light reflected by the beam splitter 300 and the reference light to obtain an image;
The measuring device separates the reference light and the measurement light using a digital Fourier transform on the hologram obtained by the off-axis method using a short wavelength laser, and the digital Fresnel transform 3D measurement apparatus using interference characteristics, characterized in that to obtain a three-dimensional stereoscopic image by applying Digital Fresnel Transform.
A light source 100;
A monochromatic filter 200 for transmitting light of a predetermined wavelength band from the light generated by the light source 100;
A beam splitter 300 for dividing the light transmitted through the monochromatic filter 200 into reference light and measurement light;
A reference light reflection mirror 400 for reflecting the reference light back to the beam splitter 300;
A measurement light reflection mirror 500 which reflects the measurement light back to the beam splitter 300 and whose height is adjustable; And
An imaging device 600 for detecting an interference between the measurement light reflected by the beam splitter 300 and the reference light to obtain an image;
The measuring device is a three-dimensional measuring device using a coherent characteristic, characterized in that when scanning the white light, the peak is detected by scanning while adjusting the height of the measuring light reflection mirror (500).
delete delete delete A light source 100;
A monochromatic filter 200 for transmitting light of a predetermined wavelength band from the light generated by the light source 100;
A beam splitter 300 for dividing the light transmitted through the monochromatic filter 200 into reference light and measurement light;
A reference light reflection mirror 400 for reflecting the reference light back to the beam splitter 300;
A measurement light reflection mirror 500 which reflects the measurement light back to the beam splitter 300 and whose height is adjustable; And
In the measuring method using a three-dimensional measuring apparatus using a coherence characteristic comprising a; image pickup device 600 for detecting the interference of the measurement light reflected by the beam splitter 300 and the reference light to obtain an image;
The monochromatic filter 200 is turned on and the micro actuator 510 of the measurement light reflection mirror 500 is turned on.
After scanning the white light from the light source 100 to the beam splitter 300 to be divided into the measurement light and the reference light,
The divided reference light and the measurement light are reflected from the reference light reflection mirror 400 and the measurement light reflection mirror 500 to the beam splitter 300, respectively.
Using the reflected measurement light and the reference light to obtain the image pickup device 600, the micro-actuator 510 is scanned at a high speed of 3 ~ 99㎛, the peak is detected,
Three-dimensional measurement method using the interference characteristics, characterized in that the coherence width of the light transmitted through the monochromatic filter 200 is 100 ~ 200㎛.

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