KR20040110887A - 3d shape measuring device and method using the correction of phase errors - Google Patents

Abstract

PURPOSE: A three dimensional shape measuring device and a method thereof are provided to improve measurement performance for a three dimensional shape by minimizing a measurement error according to variation of a surface reflective rate of an object to be measured. CONSTITUTION: A three dimensional shape measuring device includes a short-period sine wave irradiating device(10), which is a first light source. A short-period sine wave image is converted into a plane wave while passing through a collimate optical system(16). Then, the plane wave passes through mirrors(22,24,26) and irradiates onto a surface of an object(30) to be measured through a light emitting optical system(28). An optical system includes three collimate optical systems(16,18,20), beam route adjustment mirrors(22,24,26) and the light emitting optical system(28).

Description

3D surface shape measurement device and method using phase error correction {3D SHAPE MEASURING DEVICE AND METHOD USING THE CORRECTION OF PHASE ERRORS}

The present invention relates to a three-dimensional surface shape measurement system, and more particularly, to an apparatus and method for measuring three-dimensional shape using phase error correction.

The three-dimensional shape measurement technology is not limited to the engineering field, but its application range is gradually expanding, such as medicine, entertainment industry, and clothing industry. In the past, a contact measuring device using a three-dimensional coordinate measuring machine (CMM) was used as a three-dimensional shape measuring technology capable of satisfying the demands of various application fields, but recently, a non-contact three-dimensional shape measuring device based on optical theory is used. It is widely used.

The non-contact three-dimensional shape measuring device has a three-dimensional shape measuring device that extracts the three-dimensional surface shape information of the measurement object with only one image acquisition once again, or the three-dimensional surface of the measurement object after obtaining several images There is also a three-dimensional shape measuring apparatus for extracting shape information.

A shape measuring device that extracts three-dimensional surface shape information of a measurement object by acquiring only one image has a lower measurement resolution but less motion or vibration when compared to a three-dimensional shape measuring device that acquires a plurality of phase shifted images. There is an advantage in that the measuring object can be measured.

However, a shape measuring apparatus for extracting three-dimensional surface shape information of a measurement object by acquiring only one image may include phase information of the measurement object. Is ATAN (sin / cos ), The extracted phase information is obtained in a state of being broken in units of 2π height. Therefore, there is a disadvantage that a phase recovery algorithm is required to connect them. In addition, if a change in the surface reflectance of the measurement object occurs within one period of the sine wave of the sine wave image irradiated to the measurement object, a phase error may occur.

Accordingly, an object of the present invention is to provide an apparatus and method for measuring a three-dimensional surface shape using phase error correction, which can improve measurement performance of a three-dimensional shape by minimizing a measurement error caused by a change in surface reflectance of a measurement object.

Furthermore, another object of the present invention is to use a sine wave pattern of different periods to increase the resolution of the measurement object while the three-dimensional surface shape measurement apparatus using a phase error correction that can minimize the error caused during the phase restoration process And providing a method.

1 is a block diagram of a three-dimensional surface shape measuring apparatus according to an embodiment of the present invention.

2 is an exemplary view showing an image of a measurement object irradiated with a short-period sine wave according to an embodiment of the present invention.

3 is an exemplary view illustrating an image of a measuring object irradiated with a long period sine wave according to an embodiment of the present invention.

4 is an exemplary view illustrating an image of a measurement object irradiated with a DC illumination component according to an embodiment of the present invention.

5 is a diagram illustrating a phase error correction graph according to a surface reflectance change of a measurement object according to an exemplary embodiment of the present invention.

6 is a diagram illustrating a phase map image extracted from a long period sinusoidal pattern image according to an exemplary embodiment of the present invention.

7 is a diagram illustrating a phase map image extracted from a short-period sinusoidal pattern image according to an embodiment of the present invention.

8 illustrates an image before phase error correction according to a change in surface reflectance of a measurement object according to an exemplary embodiment of the present invention.

9 is a diagram illustrating an image after phase error correction according to a change in surface reflectivity of a measurement object according to an exemplary embodiment of the present invention.

Figure 10 is a simplified configuration example of a three-dimensional surface shape measurement apparatus using a sine wave pattern image according to an embodiment of the present invention.

11 is an exemplary low frequency sin phase image through modulation wave cancellation according to an embodiment of the present invention.

12 is a view illustrating a low frequency cosine (cos) phase image through modulation wave removal according to an embodiment of the present invention.

13 is an exemplary diagram of a phase map image extracted from a short-period sinusoidal pattern image after performing phase error correction according to an embodiment of the present invention.

14 is an exemplary view of a three-dimensional image measured after performing a phase error correction according to an embodiment of the present invention.

15 is an exemplary view illustrating a three-dimensional shape of an object measured after performing phase error correction according to an embodiment of the present invention.

Figure 16 is a block diagram of a three-dimensional surface shape measurement apparatus according to another embodiment of the present invention.

Figure 17 is a block diagram of a three-dimensional surface shape measuring apparatus according to another embodiment of the present invention.

The three-dimensional surface shape measuring apparatus according to an embodiment of the present invention for achieving the above object is three light sources for generating a short period sine wave, a long period sine wave and a DC illumination pattern image of different colors, respectively, The pattern image includes an optical system for irradiating the same area on the same position on the measurement object as parallel light,

Optical filters for passing short-period sinusoidal waves, long-period sinusoidal waves, and direct-current illumination pattern images of different colors in an image passing through a collimating optical system for obtaining measurement object images of different colors and mirrors positioned at a rear end thereof;

Cameras for converting the output pattern image of each of the optical filters into an electric video signal, and digitizers for digitizing the output of each of the cameras;

Phase error correction units for calculating the phase error correction value according to the surface reflectivity change of the measurement object from the DC light pattern image stored in one of the digitizers and thereby correcting the phase error of the short-period sinusoidal pattern image and the long-period sinusoidal pattern image, respectively. and;

Modulation frequency removal units for removing high frequency components from phase error corrected short and long period sinusoidal pattern images, respectively;

Phase map extractors for obtaining a phase map from each of the short- and long-period sinusoidal pattern images from which the high frequency components are removed;

And a phase restoring unit for restoring a phase from a phase map obtained from the short-period sinusoidal pattern image, and reconstructing the phase to have a value approximating a phase value obtained from the long-period sinusoidal pattern image when the phase is broken in 2π units. do.

On the other hand, the three-dimensional surface shape measurement method according to an embodiment of the present invention,

Irradiating a tricolor composite sinusoidal pattern having different periods and colors on the measurement object;

Obtaining a short-period sine wave pattern image, a long-period sine wave pattern image, and a direct-current illumination pattern image from the composite object image;

Calculating a phase error correction value according to a change in surface reflectivity of the measurement object from the obtained DC illumination pattern image;

Correcting a phase error of the short period sine wave pattern image and the long period sine wave pattern image by using the calculated phase error correction value;

Removing a high frequency component from each of the phase error corrected short- and long-period sinusoidal pattern images, and extracting a phase map from each of the high-frequency component removed pattern images;

And reconstructing the phase from the phase map obtained from the short-period sinusoidal pattern image, but reconstructing the phase to have a value close to the phase value obtained from the long-period sinusoidal pattern image when the phase is broken in 2π units.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

1 is a block diagram of a three-dimensional surface shape measurement apparatus according to an embodiment of the present invention, Figure 2 is an exemplary view showing an image of a measurement object irradiated with a short period sinusoidal wave according to an embodiment of the present invention, 3 is a diagram illustrating an image of a measuring object irradiated with a long period sine wave according to an embodiment of the present invention, and FIG. 4 is a diagram illustrating an image of a measuring object irradiated with a DC illumination component according to an embodiment of the present invention. .

First, referring to FIG. 1, the short-period sine wave irradiation apparatus 10, which is the first light source, generates an image composed of only red colors. As shown in FIG. There is no. The long-period sine wave irradiation apparatus 12, which is the second light source, is composed of only green color, and is composed of long-period sine waves as shown in FIG. The DC light irradiation apparatus 14, which is the third light source, is composed of only blue color, and the DC pattern is irradiated onto the surface of the measurement object as shown in FIG.

As shown in FIG. 1, the short-period sine wave image (color red) generated by the short-period sine wave irradiation apparatus 10 as the first light source passes through the collimation optical system 16 and is converted into a plane wave, and then mirrors 22, 24, and 26 After passing through the divergent optical system 28 and irradiated to the surface of the measurement object (30). For reference, three collimating optical systems 16, 18, and 20 which make the pattern image irradiated from each of the light sources 10 to 14 into parallel light, and each of the pattern images that become parallel light at the same location on the measurement object The beam path adjusting mirrors 22, 24, 26 and the diverging optical system 28 irradiated with each other may be represented by one optical system.

On the other hand, the long-period sine wave image (color green) generated by the long-period sine wave irradiation device 12, which is the second light source, passes through the collimation optical system 18, is converted into a plane wave, passes through mirrors 24 and 26, and then diverges optical system 28. And then irradiated to the surface of the object to be measured. At the same time, the DC illumination image (color blue) irradiated by the DC light irradiation device 14, which is the third light source, passes through the collimation optical system 20, converts into a plane wave, passes through the mirror 26, and then diverges the optical system 28. It is irradiated to the surface of the object to be measured.

The short-period sine wave pattern image irradiated onto the measurement object surface 30 passes through one collimation optical system 32 for acquiring the three-color measurement object image, and then passes through the mirrors 34, 36, 38, and the first optical ( RED) is passed through the filter 40, the camera 46 is converted into an electrical image value and output. The short period sinusoidal pattern image converted into an electrical image value is digitized and stored in the digitizer 56.

On the other hand, the long-period sine wave pattern image irradiated onto the surface of the measurement object 30 passes through the collimation optical system 32, passes through the mirrors 34 and 36, passes through the second optical filter 42, and then the camera 48. After converted into an electrical image by the digitizer 54 is stored digitized.

In addition, the DC illumination pattern image irradiated onto the surface of the measurement object 30 passes through the collimation optical system 32, passes through the mirror 34, passes through the third optical filter 44, and then is electrically transmitted from the camera 50. After conversion to the video value, the digitizer 52 is digitized and stored.

Meanwhile, each of the two phase error correction units 58 and 60 calculates a phase error correction value according to the surface reflectivity change of the measurement object from the DC light pattern image stored in the digitizer 52 among the digitizers 52, 54 and 56, Through this, it plays a role of correcting (removing) the phase error of the short period sine wave pattern image and the long period sine wave pattern image, respectively. The phase error correction unit 58, 60 uses a phase error correction graph as shown in FIG.

In the phase error correction graph shown in FIG. 5, the DC light irradiation device 14 serving as the third light source sequentially irradiates the DC light to the measurement target surface 30 while increasing the brightness from 10 to 250 by 10, and then the digitizer 52. ) Shows the brightness distribution of the measurement target image.

For example, when the DC illumination device 14 shown in FIG. 1 irradiates with brightness 100, the measurement object image acquired by the digitizer 52 is an image as shown in FIG. The range is W and the average brightness value is V. In FIG. 4, the change in brightness at the dark pixel 'ga' pixel position is the 'fall' graph of FIG. 5, and the change in brightness at the brightest portion 'a' pixel position of FIG. 4 is the 'b' graph of FIG. 5. . 5 is an average brightness value of the image.

If the system for extracting three-dimensional surface shape information with a single image acquisition, as in the present invention, changes the pixel brightness due to a change in the surface reflectivity of the measurement object within one period of the sinusoidal measurement object image acquired by the digitizer, phase error. Occurs. Therefore, in the present invention, the phase error is corrected through the phase error correction units 58 and 60 shown in FIG.

The phase error correction unit 58, 60 calculates an average value V of the DC light image data stored in the digitizer 52, and then divides the current pixel intensity value I_i, j by this value and multiplies each pixel by a weight value. Calculate In other words . here Is the pixel intensity value at the DC illumination image (i, j) position. In the present invention, a weight value for phase error correction after removing high frequency components using a low pass filter on a DC light pattern image acquired by the digitizer 52 for smooth continuous phase error correction. Calculate

On the other hand, the phase error correction unit 58 is an intensity value of the (i, j) pixel position of each long-period sinusoidal pattern image stored in the digitizer 54 Phase error correction weight value obtained before Multiply by to correct for phase error. In addition, the phase error correction unit 60 is an intensity value of the (i, j) pixel position of each short-period sinusoidal pattern image stored in the digitizer 56 Phase error correction weight value obtained before Multiply by to correct for phase error. The phase error correction unit 58, 60 is the same as the phase error correction unit of the three-dimensional surface shape measurement apparatus using the three-color and dichroic sinusoidal patterns described later.

For reference, FIG. 8 is an image obtained by rotating the image shown in FIG. 2 by 90 degrees, which shows an image before phase error correction according to a change in surface reflectance, and FIG. 9 shows an image of the phase error correctors 58 and 60. Shows an image after phase error correction. As shown in FIG. 9, it can be seen that the S / N ratio is increased in the sine wave pattern in which the phase error correction is performed.

The short- and long-period sine wave pattern images corrected by the phase error correcting units 58 and 60 are input to the modulation frequency removing units 64 and 62, respectively, so that high frequency components are removed and sin phase and Only the cosine phase is extracted and then input to the phase map extractors 68 and 66. As described above, the principle of measuring the three-dimensional surface shape of the measurement object is explained before explaining the principle of the modulation frequency removal unit 64 or 62 for removing the modulation frequency from the image of the object to which the sine wave pattern is irradiated.

First, FIG. 10 briefly illustrates the configuration of a three-dimensional surface shape measuring apparatus using sinusoidal waves, and P and C located at the same distance L from the reference plane are located at the center of the sinusoidal pattern irradiation apparatus and the camera imaging optics. The distance d is the distance between P and C. In FIG. 8, the x axis is selected, the y axis is perpendicular to this plane and the reference plane, and the z axis is the distance between the measurement target surface and the reference plane. Assuming that P is very far, the irradiation light is parallel light and the pattern of this light has g _p (x, y) as shown in Equation 1 below.

In Equation 1, p means the period of the sine wave irradiated to the reference plane. If p is at a finite distance from O, the irradiation light emits, so a point far from point O moves farther than from point O. Suppose r (x) is the distance moved at point (x, y), where P is a sinusoidal pattern on the reference plane when E is moved from an infinite distance from point O.

In Equation 2, R _r (x, y) represents a nonuniform reflectance distribution on the reference plane, which may be expressed by Equation 3 below.

In Equation 3, Bn (x, y) = Rr (x, y) An (x, y), Indicates that the phase is shifted on the reference plane.

As shown in FIG. 10, when a slightly deformed sinusoidal pattern is irradiated on the surface of the measurement object located slightly behind the reference plane, a more deformed pattern is obtained at the position C. FIG. For example, the height h on the surface of the measurement object is irradiated through b on the reference plane. When this is observed at position C, it is equal to a on the reference plane. On the optical axis, h and a are perceived as the same point on the image plane, so when we see what is recorded on the image plane, the intersection of the reference plane and the light appears to have moved from b to a. Now, when the distance moved further at the intersection point (x, y) is s (x, y), the sine wave pattern on the measurement object may be expressed by Equation 4 or 5 below.

In Equation 4, 5, R o (x, y) represents the reflectance of the non-uniform distribution of the surface of the measurement object. Meanwhile (x, y) = (x, y) An (x, y) Indicates phase shifted on the surface of the measurement object.

The phase difference between the reference plane and the surface of the measurement object is expressed by Equation 6 below.

In Equation 6, s (x, y) for the height h on the surface of the measurement object is a distance between b and a in FIG.

In the method for extracting the phase information from the measurement object image modulated by the sinusoidal modulation frequency, the technique up to now is the method of extracting the TAN phase component by extracting the COS phase component and the SIN phase component. have.

Hereinafter, the principle of the modulation frequency removing unit 62 or 64 for removing the modulation frequency from the measured object image irradiated with the sine wave pattern, the modulation frequency removing unit 62 or 64 according to the embodiment of the present invention is cosine ( In order to extract the modulation phase of the COS) component, the cosine (COS) modulation frequency is multiplied by the measurement object image. Considering one sinusoidal pattern in the measurement object image, it is shown in Equation 7 below, and considering the equation obtained by multiplying the cosine (COS) modulation frequency by this one sinusoidal pattern is shown in Equation 8 below.

Phase in Equations 7 and 8 (x, y) contains the desired information that changes slowly compared to 2πx / p. In Equation 8, only Only the term is a low frequency component.

Therefore, the modulation frequency removal unit 62, 64 uses a low pass filter to separate the low frequency components, and the cosine phase components can be expressed as shown in Equation 9 below.

In order to obtain the phase information, it is now necessary to extract the sin phase component from the object image. In order to extract the modulation phase of the sinusoidal components, the modulating frequency removing units 62 and 64 multiply the sin modulation frequency by the measurement object image. Considering an expression obtained by multiplying the sinusoidal modulation frequency sin (2πx / p) in the measurement target image, it is expressed by Equation 10 below.

Similarly in Equation 10 Since only the term is a low frequency component, the modulation frequency remover 62 or 64 separates the sine phase component using the low pass filter as shown in Equation 11 below.

Then, phase information as shown in Equation 12 may be extracted.

Phase information on the surface shape of the object to be measured When (x, y) is extracted, the actual height value may be calculated as in Equation 14 by using a relational expression as in Equation 13.

For reference, FIG. 11 is a result of obtaining a sine phase image by removing a modulating frequency and then performing low pass filtering on the image of FIG. 9, and FIG. 12 is a cosine by removing a modulating frequency and then performing low frequency filtering on the image of FIG. 9. This is the result of the phase image.

Meanwhile, each of the phase map extractors 66 and 68 extracts a phase map from each of the short- and long-period sinusoidal pattern images from which high frequency components are removed. 6 and 7 show examples of the phase maps extracted by the phase map extractors 66 and 68. 6 and 7 illustrate phase map images obtained from long and short period sinusoidal pattern images. For reference, FIG. 13 also shows a phase map image acquired using a short period sinusoidal pattern.

Finally, the phase restoring unit 70 restores the phase from the phase map obtained from the short-period sinusoidal pattern image, and restores the phase to have a value closest to the phase value obtained from the long-period sinusoidal pattern image when the phase is broken in 2π units. Do this. The phase restoration unit 70 will be described in detail.

First, the phase map information stored in the phase map extractor 68 is a phase map extracted from a short-period sine wave pattern image as shown in FIG. 7. As shown in FIG. 7, the phase map information extracted from the short-period sine wave pattern image has excellent measurement resolution but is obtained in the form of being broken in units of 2π as shown in FIG. 7. Therefore, a phase restoration process inevitably connecting broken phase information is necessary. This phase restoration process is likely to include a lot of errors due to realistic technical limitations and ambient noise effects.

On the contrary, the phase map information stored in the phase map extractor 66 is a phase map extracted from a long period sinusoidal pattern image as shown in FIG. 6. As shown in FIG. 6, the phase map information extracted from the long-period sine wave pattern image has low measurement resolution, but it can be seen that the phase map is connected without disconnection. Therefore, the phase restoring unit 70 obtains the phase information using the phase map 68 information obtained from the short-period sinusoidal image having high measurement resolution, and the phase map 66 of the phase is not broken in the phase restoration process for the broken portion. By restoring the phase in the direction that is closest to), it is possible to restore the phase with high measurement resolution but without error. FIG. 14 is three-dimensional shape information in which the phase information restored by the phase restoring unit 70 is expressed by pixel intensity values, and FIG. 15 is an image when the display of FIG. 14 is three-dimensionally displayed.

As described above, the phase restoring unit 70 of the apparatus for measuring a three-dimensional surface shape according to an exemplary embodiment of the present invention uses a short-period sine wave having a high measurement resolution in the process of restoring a phase from a phase map. The information is extracted, and in the part broken by 2π height unit, the phase restoration is attempted to have the closest phase by using three-dimensional shape information using a long-period sine wave pattern as a reference comparison target, thereby increasing the resolution of the measurement object and the error of phase restoration is increased. Less phase reconstruction can be performed.

Hereinafter, a three-dimensional surface shape measuring apparatus according to another embodiment of the present invention will be described.

First, FIG. 16 is a block diagram of an apparatus for measuring a three-dimensional surface shape according to still another embodiment of the present invention, and more specifically, illustrates a configuration of an apparatus for measuring a three-dimensional surface shape using a tricolor composite sinusoidal pattern.

Referring to FIG. 16, the tricolor composite sinusoidal pattern irradiation device 80, which is a light source, is a tricolor in which a short period sine wave pattern consisting of R, G, and B color colors, a long period sine wave pattern, and a DC lighting pattern are combined. One configured color pattern image is generated and irradiated to the measurement object 30. The tricolor composite sinusoidal pattern irradiation apparatus 80 should generate a long-period sinusoidal pattern image having a long period of uninterrupted 2π units in a phase map of a measurement object for implementing the present invention. Except for the three-color composite sinusoidal pattern irradiation device 80 is the same as the configuration shown in Figure 1, the detailed description thereof will be omitted, and the following three color composite sinusoidal pattern through the image processing process of the measurement object The operation of the three-dimensional surface shape measuring apparatus used will be described.

First, the image of the measurement object passes through the collimation optical system 32 and then passes through the mirrors 34, 36, 38. The image passing through the first optical (R) filter 40 in the composite color measurement object image is a short-period sine wave pattern image. The image forms an image on the camera 46 and is electrically digital by the digitizer 56. Is converted to. In addition, the image passing through the second optical (G) filter 42 in the composite color measurement object image is a long-period sine wave pattern image, and the image is formed on the camera 48 and is electrically digital by the digitizer 54. Is converted to. Finally, the image passing through the third optical (B) filter 44 is a DC illumination pattern image, which is also an image formed on the camera 50 and converted into an electrical digital value by the digitizer 52.

The phase error correction unit 60 corrects the phase error of the short-period sinusoidal pattern image stored in the digitizer 56 using the phase error correction graph as shown in FIG. 5. In the short-period image whose phase error is corrected, the high frequency component is removed by the modulating frequency removing unit 64, and only the SIN phase and the COS phase are extracted, and then the phase map extractor 68 displays the phase map as shown in FIG. Obtained. In the same manner, the phase error correction unit 58 also corrects the phase error of the long-period sinusoidal pattern image stored in the digitizer 52 using the phase error correction graph. In the long-period image whose phase error is corrected, the high frequency component is removed by the modulation frequency remover 62 and only the SIN phase component and the COS phase component are extracted, and then the phase map extractor 66 shows the phase map as shown in FIG. 6. Is obtained.

When the phase maps of the two images are obtained, the phase restoring unit 70 calculates the height information of the measurement target by extracting the optimal phase information without increasing errors in the phase restoration while increasing the measurement resolution. That is, the phase restoring unit 70 extracts three-dimensional shape information of the measurement object by using a short period sine wave having a high measurement resolution in the process of restoring the phase from the phase map, and extracts a long period sine wave pattern at a portion broken by 2π height units. By reconstructing the phase to have the most approximate phase by using the three-dimensional shape information used as the reference comparison target, it is possible to increase the resolution of the measurement object and perform phase reconstruction with less error in phase recovery.

17 illustrates a three-dimensional surface shape measurement apparatus using a dichroic sinusoidal pattern according to another embodiment of the present invention.

The three-dimensional surface shape measuring apparatus shown in FIG. 17 includes a first light source 90 for generating a short-period sinusoidal pattern image Red including a DC illumination image, and a color different from that of the first light source 90. The second light source 100 generating a long-period sine wave pattern image including the DC illumination image and the pattern image irradiated from each of the light sources 90 and 100 are parallel light and are identical at the same position on the measurement object 30. Basically, the optical system 16, 18, 22, 24, 28 for irradiating an area is included.

Furthermore, the three-dimensional surface shape measurement apparatus using a dichroic sinusoidal pattern is a cross-sectional optical system 32 for acquiring the image of the measurement object of different colors and the image passing through the mirrors 36 and 38 positioned at the rear end of each other. Optical filters 40 and 42 for passing short and long period sinusoidal pattern images of different colors, and cameras for converting output pattern images of the optical filters 40 and 42 into electrical image signals, respectively. (46,48) and digitizers (54,56) for digitizing the output of each of the cameras.

The apparatus further includes image signal dividers 110 and 120 which separate the short-cycle sine wave pattern image and the long-cycle sine wave pattern image stored in each of the digitizers 54 and 56 into a DC image and an AC sine wave pattern, respectively. The image signal splitters 110 and 120 cover a low pass filter (LPF) directly in the frequency domain to separate the lighting component of the DC component and the sinusoidal pattern of the AC component. The image signal splitters 110 and 120 may extract a DC image that is an illumination component by convoluting and smoothing the averaging window.

On the other hand, the three-dimensional surface shape measuring apparatus is a DC image and sinusoidal image storage unit (130, 140, 150, 160) for storing each of the DC image and the AC sine wave pattern image divided by the image signal dividing unit (110, 120) and each of the storage unit Phase error correction units 58 and 60 for calculating phase error correction values according to surface reflectance changes of the measurement object based on the stored DC images, and correcting phase errors of the short period AC sine wave pattern image and the long period AC sine wave pattern image, respectively. Phase modulation for removing high frequency components from the short- and long-period sinusoidal pattern images, respectively, which are phase error corrected, and phase maps for obtaining a phase map from the respective short- and long-period sinusoidal pattern images for which high-frequency components have been removed. Reconstruct a phase from a phase map obtained from the extractors 66 and 68 and the short-period sinusoidal pattern image, wherein 2π When broken up, the phase restoration includes a phase recovery unit 70 for phase-restore to have the closest match to the phase values obtained from the long-cycle sinusoidal pattern image with no broken.

In more detail, the operation of the device having the above-described configuration,

First, the short-period sine wave image (color red) generated by the short-period sine wave irradiation device 90 including the DC lighting component is converted into plane wave through the collimation optical system 16, and then passes through the mirrors 22 and 24. After passing through the divergent optical system 28 is irradiated to the surface of the measurement object (30). In addition, a long period sine wave image (color green) generated by a long period sine wave irradiation apparatus 100 including a DC lighting component is also converted into a plane wave through the collimation optical system 18 and then passed through the mirror 24 and then a diverging optical system 28 Is irradiated to the surface of the measuring object.

The short-period sine wave pattern image irradiated on the surface of the measurement object 30 passes through the collimating optical system 32 and the mirrors 36 and 38, passes through the first optical filter 40, and then is electrically imaged by the camera 46. After conversion to the digitizer 46 is converted to a digital value and stored. The image signal dividing unit 110 divides the image stored in the digitizer 56 into a DC component and an AC component, and stores the DC component in the DC image storage unit 130 and stores the AC component in the pattern image storage unit 140. .

In the same principle, the long-period sine wave pattern image irradiated onto the surface of the measurement object is also passed through the collimation optical system 32 and the mirror 36 to pass through the second optical filter 42 and then converted into an electrical image value by the camera 48. The digitizer 54 is then stored as a digital value. The image signal dividing unit 120 divides the image stored in the digitizer 54 into a DC component and an AC component, and stores the DC component in the DC image storage unit 150 and stores the AC component in the pattern image storage unit 160. . The above-described DC image storage unit and the pattern image storage unit may be implemented as a single memory.

On the other hand, the phase error correction unit 60 multiplies the image error stored in the pattern image storage unit 140 by the phase error correction value obtained from the image stored in the DC image storage unit 130 on the same principle as in FIG. Correct the phase error within 1 cycle caused by the change. Similarly, the phase error correction unit 58 multiplies the phase error correction value obtained from the image stored in the DC image storage unit 150 by the image stored in the pattern image storage unit 160 to generate one cycle caused by the change in the surface reflectance of the measurement object. Correct the phase error inside.

In the short-period pattern image having the phase error corrected, only the SIN phase and the COS phase are extracted after the high frequency component is removed by the modulation frequency removing unit 64, which is the phase as shown in FIG. The map is obtained. In addition, the long period image of which phase error is corrected is obtained by removing the high frequency components by the modulating frequency removing unit 62, and then extracting the SIN phase and the COS phase components, and then, by the phase map extracting unit 66, a phase map as shown in FIG. Is obtained.

The phase restoring unit 70, which obtains a phase map of two images, calculates the height information of the measurement object by extracting optimal phase information from the two images while increasing the measurement resolution and without error in the phase restoration. That is, the phase restoring unit 70 extracts three-dimensional shape information of the measurement object by using a short period sine wave having a high measurement resolution in the process of restoring the phase from the phase map, and extracts a long period sine wave pattern at a portion broken by 2π height units. By reconstructing the phase to have the most approximate phase by using the three-dimensional shape information used as the reference comparison target, it is possible to increase the resolution of the measurement object and perform phase reconstruction with less error in phase recovery.

In conclusion, in the embodiments of the present invention, the 3D shape information of the measurement object is extracted by using the short period sine wave with high measurement resolution, and the reference comparison object is based on the 3D shape information using the long period sine wave pattern at the portion broken by 2π height. By attempting to restore the phase to have the most approximate phase, it is possible to restore the phase with less phase error while increasing the resolution of the measurement object.

As described above, the present invention uses the sinusoidal patterns of different periods to increase the measurement resolution of the measurement object while minimizing the incidence of errors occurring during the phase restoration process. There is an advantage that can be improved to minimize the measurement performance of the three-dimensional shape.

On the other hand, the present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be defined only by the appended claims.

Claims (11)

Three light sources for generating short-period sine wave, long-period sine wave, and DC illumination pattern images of different colors, and an optical system for irradiating the pattern image irradiated from each light source to the same location on the measurement object as parallel light In the three-dimensional surface shape measuring apparatus having, Optical filters for passing short-period sinusoidal waves, long-period sinusoidal waves, and direct-current illumination pattern images of different colors in an image passing through a collimating optical system for obtaining measurement object images of different colors and mirrors positioned at a rear end thereof; Cameras for converting the output pattern image of each of the optical filters into an electric video signal, and digitizers for digitizing the output of each of the cameras; Phase error correction units for calculating the phase error correction value according to the surface reflectivity change of the measurement object from the DC light pattern image stored in one of the digitizers and thereby correcting the phase error of the short-period sinusoidal pattern image and the long-period sinusoidal pattern image, respectively. and; Modulation frequency removal units for removing high frequency components from phase error corrected short and long period sinusoidal pattern images, respectively; Phase map extractors for obtaining a phase map from each of the short- and long-period sinusoidal pattern images from which the high frequency components are removed; A phase restoring unit for restoring a phase from a phase map obtained from a short-period sine wave pattern image and reconstructing the phase to have a value approximating a phase value obtained from a long-period sine wave pattern image when the phase is broken in units of 2π. 3D surface profile measuring device. The method according to claim 1, wherein each of the phase error correction unit, The average value (V) of the DC light image averaged by the low pass filter is calculated, and the pixel intensity value of the current DC light image ( ) By dividing by and multiplying each pixel (i, j) position in the AC sine wave pattern image ( And calculate the intensity value of the (i, j) pixel position of each AC sine wave pattern image. ), The phase error correction weight value ( 3) surface shape measuring device, characterized in that for correcting the phase error occurring within one period of the AC sine wave pattern by multiplying by). 3. The 3D surface shape measurement of claim 1, wherein one of the three light sources generates a long-period sinusoidal pattern image having a long period of unbroken length in units of 2π in a phase map of the measurement object. Device. In the three-dimensional surface shape measurement apparatus using a three-color composite sinusoidal pattern, A tricolor composite sinusoidal pattern light source for generating and irradiating one color pattern image in which a short period sinusoidal pattern composed of different colors, a long period sinusoidal pattern, and a direct current lighting pattern are combined; Optical filters for passing short-period sinusoidal waves, long-period sinusoidal waves, and direct-current illumination pattern images of different colors in an image passing through a collimating optical system for obtaining measurement object images of different colors and mirrors positioned at a rear end thereof; Cameras for converting the output pattern image of each of the optical filters into an electric video signal, and digitizers for digitizing the output of each of the cameras; Phase error correction units for calculating the phase error correction value according to the surface reflectivity change of the measurement object from the DC light pattern image stored in one of the digitizers and thereby correcting the phase error of the short-period sinusoidal pattern image and the long-period sinusoidal pattern image, respectively. and; Modulation frequency removal units for removing high frequency components from phase error corrected short and long period sinusoidal pattern images, respectively; Phase map extractors for obtaining a phase map from each of the short- and long-period sinusoidal pattern images from which the high frequency components are removed; A phase restoring unit for restoring a phase from a phase map obtained from a short-period sine wave pattern image, and reconstructing the phase to have a value closest to a phase value obtained from a long-period sine wave pattern image when the phase is broken in units of 2π. 3D surface shape measurement apparatus using a three-color composite sinusoidal pattern. The method according to claim 4, wherein each of the phase error correction unit, The average value (V) of the DC light image averaged by the low pass filter is calculated, and the pixel intensity value of the current DC light image ( ) By dividing by and multiplying each pixel (i, j) position in the AC sine wave pattern image ( And calculate the intensity value of the (i, j) pixel position of each AC sine wave pattern image. ), The phase error correction weight value ( Three-dimensional surface shape measurement apparatus using a three-color composite sinusoidal pattern characterized in that to correct the phase error occurring in one cycle of the AC sine wave pattern by multiplying the multiplier by. The method of claim 4 or 5, wherein the tricolor composite sinusoidal pattern light source; A three-dimensional surface shape measurement apparatus using a three-color composite sinusoidal pattern, characterized in that to generate a long-period sinusoidal pattern image having a long period in the phase map for the object to be measured in 2π uninterrupted. A first light source for generating a short period sinusoidal pattern image including a direct current illumination image, a second light source having a color different from the first light source but generating a long period sinusoidal pattern image including a direct illumination image, and light sources In the three-dimensional surface shape measurement apparatus using a dichroic sinusoidal pattern having an optical system for irradiating the pattern image irradiated from each of the same image on the same position on the measurement object as parallel light, Optical filters for passing short-period sinusoidal and long-period sinusoidal pattern images of different colors in an image passing through a collimation optical system for obtaining measurement object images of different colors and mirrors positioned at the rear end thereof; Cameras for converting the output pattern image of each of the optical filters into an electric video signal, and digitizers for digitizing the output of each of the cameras; Image signal dividing units for dividing the short-period sinusoidal pattern image and the long-period sinusoidal pattern image stored in each of the digitizers into DC and AC sinusoidal patterns, respectively; DC image and sinusoidal image storage units for storing each of the DC image and AC sine wave pattern image divided by each image signal divider; Phase error correction units for calculating the phase error correction value according to the surface reflectivity change of the measurement object from the DC image stored in each of the storage unit, and correcting the phase error of the short period AC sine wave pattern image and the long period AC sine wave pattern image, respectively; ; Modulation frequency removal units for removing high frequency components from phase error corrected short and long period sinusoidal pattern images, respectively; Phase map extractors for obtaining a phase map from each of the short- and long-period sinusoidal pattern images from which the high frequency components are removed; A phase restoring unit for restoring a phase from a phase map obtained from a short-period sinusoidal pattern image, and reconstructing the phase to have a value closest to a phase value obtained from a long-period sinusoidal pattern image without breaks when the phase is broken in units of 2π; 3D surface shape measurement apparatus using a dichroic sine wave pattern characterized in that. The method of claim 7, wherein each of the phase error correction unit, The average value (V) of the DC light image averaged by the low pass filter is calculated, and the pixel intensity value of the current DC light image ( ) By dividing by and multiplying each pixel (i, j) position in the AC sine wave pattern image ( And calculate the intensity value of the (i, j) pixel position of each AC sine wave pattern image. ), The phase error correction weight value ( 3D surface shape measurement apparatus using a dichroic sinusoidal pattern, characterized in that for correcting the phase error occurring in one cycle of the alternating sinusoidal pattern by multiplying). The method of claim 7 or 8, wherein the second light source; A three-dimensional surface shape measurement apparatus using a dichroic sinusoidal pattern, characterized in that to generate a long-period sinusoidal pattern image having a long period of continuous in 2π unit in the phase map for the measurement object. In the method for measuring the three-dimensional surface shape of the measurement object, Irradiating a tricolor composite sinusoidal pattern having different periods and colors on the measurement object; Obtaining a short-period sine wave pattern image, a long-period sine wave pattern image, and a direct-current illumination pattern image from the composite object image; Calculating a phase error correction value according to a change in surface reflectivity of the measurement object based on the average value of the obtained DC illumination pattern image; Correcting a phase error of the short period sine wave pattern image and the long period sine wave pattern image using the calculated phase error correction value; Removing a high frequency component from each of the phase error corrected short- and long-period sinusoidal pattern images, and extracting a phase map from each of the high-frequency component removed pattern images; Reconstructing a phase from a phase map obtained from a short-period sinusoidal pattern image, but reconstructing the phase to have a value close to the phase value obtained from the long-period sinusoidal pattern image when the phase is broken in units of 2π. 3D surface shape measurement method using. In the method for measuring the three-dimensional surface shape of the measurement object, Irradiating the measurement object with a short period and a long period sine wave pattern having different colors and each comprising a DC lighting component; Obtaining a short period sinusoidal pattern and a long period sinusoidal pattern image from the measurement object image, respectively; Separately storing a DC image and an AC sine wave pattern from the acquired short period sinusoidal pattern and long period sinusoidal pattern image, respectively; Calculating a phase error correction value according to a change in surface reflectivity of the measurement object based on the average value of the stored DC image; Correcting phase errors of the short-cycle AC sine wave pattern image and the long-cycle AC sine wave pattern image using the calculated phase error correction values; Removing a high frequency component from each of the phase error corrected short- and long-period sinusoidal pattern images, and extracting a phase map from each of the high-frequency component removed pattern images; Restoring a phase from a phase map obtained from a short-period sinusoidal pattern image, and reconstructing the phase to have a value closest to a phase value obtained from a long-period sinusoidal pattern image without interruption when the phase is broken in units of 2π. 3D surface shape measurement method using a dichroic sine wave pattern.