KR100585272B1 - Monochrome sinusoidal pattern phase shifting based system and method for range imaging from two images - Google Patents

Abstract

The present invention restores a phase at each point of two images by using phase shifting of a monochromatic sinusoidal pattern to obtain a distance image of a target object based on the phase shift of two images. The present invention relates to a distance image acquisition device and method using two transition-based images.

According to the present invention, there is an effect that relatively accurate phase restoration can be performed based on phase shift in two images, and thus, phase shift of sinusoidal wave, which previously required at least three images for phase restoration, is required. In this method, it is possible to acquire high resolution phase and distance images from two images, thereby enabling relatively accurate acquisition of high resolution phase and distance images in an easier manner at a lower cost and in a shorter time. .

Description

MONOCHROME SINUSOIDAL PATTERN PHASE SHIFTING BASED SYSTEM AND METHOD FOR RANGE IMAGING FROM TWO IMAGES}

1 is a view showing a schematic configuration of a distance image acquisition device using two images of the present invention

FIG. 2 is a block diagram schematically illustrating a configuration of a distance image restoration module in an apparatus for obtaining distance images using two images of FIG. 1;

3 is a diagram illustrating each luminance distribution curve and each pattern image of three sinusoidal phase shifts.

4 is a view illustrating an image captured by a camera by projecting a sine wave illumination pattern onto a surface of an object;

FIG. 5 is a diagram illustrating a method of taking luminance values at two positions to restore phase in the image of FIG. 4. FIG.

<Description of Symbols for Main Parts of Drawings>

100: object 200: lighting module

300: recording module 400: distance image restoration module

410: first brightness value calculator 420: first subtractor

430: second brightness value calculator 440: adder

450: inverse transform unit 460: second subtractor

470: Multiplier 480: Distance Image Restoration Unit

The present invention relates to an apparatus and method for obtaining a distance image using two images based on monochromatic sinusoidal phase shift. More specifically, the present invention relates to a method for obtaining a distance image based on phase shifting of a monochromatic sinusoidal pattern. The present invention relates to a distance image acquisition device and method using two monochrome sine wave phase shift based images for restoring a phase at a point to obtain a distance image of a target object.

In general, a method of obtaining a distance image is classified into a contact type and a non-contact type. Among them, the present invention relates to a non-contact method, and an optical method is representative of a non-contact method that does not contact a distance image acquisition target.

Among the optical distance image acquisition methods, in order to reconstruct the distance image in high resolution, an active vision method using a special lighting pattern is mainly used, and has a configuration including an illumination module and a photography module.

Representative technologies of the active vision method include color-encoded structured light by K.L. Boyer et al., P.S. Huang et al.'S color fringe pattern, C. Je et al's high-contrast color-stripe pattern, J. Tajima et al.'S rainbow pattern, Adaptive color structured light from D. Caspi et al., Black / white boundary codes from O. Hall-Holt et al.

Among the active vision technologies, the sinusoidal phase shifting method is effective when the area to be acquired is relatively larger than the height or depth.

Phase shifting is a well known technique in the field of 3D data acquisition, and is often combined with other 3D imaging techniques. Phase shifting can be used to increase precision in moire interferometry technology, or for continuous coding in structured lighting.

Various phase restoration methods based on the phase shift of sinusoids have been devised, and the range image acquisition technology applying them is also very diverse. In the phase shift method, the reconstruction of the phase is mainly performed from intensity information in which three to five phases are shifted, and the possible phase shift intervals are very limited. Although phase restoration methods have been proposed by Carre et al. That the value of the phase shift intervals is limited, the phase transition intervals that can be easily applied are still limited.

According to the prior art, a technique using a phase shift is disclosed in Patent Application Nos. 10-1997-0038312, 10-1997-0072162, 10-2000-0069549, 10-2002-0036183, and 10-2002- It was presented in 0036848.

The conventional techniques described above describe a technique of using phase shift in a plurality of images and a technique of measuring a three-dimensional shape.

However, according to the related art, various problems related to the phase shift occur when a distance image is obtained by using a plurality of phase shift images. In particular, there are limitations in application due to limitations in the phase shift intervals, it takes a lot of time to perform phase shifts and acquire images in each transition state, and it takes a long time to process a plurality of images. This happens.

On the other hand, the recent industrial applications of the distance image acquisition is increasingly demanding data acquisition, the conventional technology has a problem that is difficult to meet the demand.

Therefore, an apparatus and a technology capable of significantly reducing the number of images required for obtaining distance image data are required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its object is to perform phase restoration through two images and to use the two images based on monochrome sine wave phase shift to obtain a distance image accordingly. An accurate distance image acquisition device and method are provided.

Another object of the present invention is to provide an apparatus and method for obtaining distance images using two images based on monochrome sine wave phase shift, which can drastically reduce image acquisition time and image processing time by using two images.

In addition, another object of the present invention is to apply a sinusoidal phase shift based on two images, so that high-resolution data can be obtained more easily, faster, and at a lower cost. To provide a distance image acquisition device and method using the.

According to a first aspect of the present invention for achieving the above object, an illumination module for projecting a target object, two monochromatic sinusoidal patterns of two phases different from each other on the target object in turn; A photographing module for capturing a state in which each illumination pattern is projected on the target object in order to obtain first and second images, and a distance image restoring module connected to the photographing module to process a photographed image to obtain a distance image; In the distance image acquisition device is configured to include, and to restore the phase (phase) at each point of the two images using the phase shifting of the sine wave pattern based on this distance image acquisition device,

The distance image reconstruction module may include: a first luminance value calculator for calculating first luminance values at the same arbitrary position of the first and second captured images; and a first subtraction process for the calculated first luminance values. A subtractor, a second luminance value calculator for calculating second luminance values by applying a value set to the result of the first subtractor, an inverse transformer for performing reciprocal processing on the result of the second luminance value calculator, and the first A multiplier performing a multiplication process on the result of the light intensity calculator and the result of the inverse transform unit, and a distance image restoring unit obtaining a distance image of the object by using phase information obtained through the multiplier result. The present invention provides a distance image acquisition device using two images based on monochromatic sinusoidal phase shift.

In this case, according to an additional feature of the present invention, the distance image reconstruction module is installed between the second brightness value calculator and the inverse converter to perform an addition process on the second brightness values of the second brightness value calculator. It is preferable that the apparatus further includes an adder and a second subtractor disposed between the second intensity value calculator and the multiplier to subtract the second intensity values of the second intensity value calculator.

)를 갖는 정현파 패턴을 조명모듈을 통해 위상을 달리하여 2회에 걸쳐 대상물체 표면에 영사한 후 그 장면을 촬영모듈로 촬영하는 제1 과정;According to a second aspect of the present invention for achieving the above object, a predetermined spatial frequency (

A first step of projecting a sinusoidal wave pattern having a) to a surface of an object two times by changing a phase through an illumination module and then photographing the scene with a photographing module;

A second process of obtaining two first luminance values according to a specific phase difference at an arbitrary point of the image photographed in the first process, according to the following equation;

A third step of subtracting the two first brightness values obtained in the second step to obtain a value such as the following equation;

이다.here,

to be.

을 적용하여 하기의 식과 같은 2개의 제2 광도값들을 얻는 제4 과정;Two constant displacement values at the point in the equation obtained in the third step

A fourth process of obtaining two second luminance values by the following equation;

의 역수를 취해 값을 얻는 제5 과정;Obtained in the fourth step

A fifth process of obtaining a value by taking an inverse of the number;

과 제5 과정에서 얻어진

의 역수에 대하여 곱셈을 실행하여 하기의 식을 얻어 위상을 복원하는 제6 과정;Obtained in the fourth step

Obtained in step 5 and

Performing a multiplication on the reciprocal of to obtain the following equation to restore the phase;

A distance image acquisition method using two images, comprising a seventh process of acquiring a distance image of a target object through geometric correction based on the obtained phase information.

At this time, according to an additional feature of the present invention, it is preferable that the phase difference between the sinusoidal patterns in the first process is π.

가 충분히 작을 때, 상기 지점으로부터 변위

만큼 떨어진 위치에서 주어지는 광도값에 관한 하기의 식이Further, according to another additional feature of the present invention, the equation of the second brightness value given in the fourth process is

Is small enough, the displacement from the point

The following equation for the intensity value given at

Characterized in that the results are approximated by the following equation,

이고, 형상(geometry)이나 반사특성(reflectance)이 x에서

까지의 영역에서 급격하게 변하지 않는 것으로 가정하고 상기

를

으로 두는 것이 바람직하다.here,

Where the geometry or reflection is at x

Assuming that it does not change abruptly in the area up to

To

It is preferable to leave.

값은 서로 π/2 의 위상차가 나는 것이 바람직하다.In addition, according to another additional feature of the invention,

It is preferable that the values have a phase difference of π / 2 with each other.

가 일반적인 값들일 때, 제4 과정에서 얻어진 2개의 제2 광도값들에 대하여 가산처리를 행하여 얻어진 값을 제5 과정에서 역수를 취하도록 하는 단계를 더 포함하는 것이 바람직하다.Furthermore, according to another additional feature of the invention,

When is general values, it is preferable to further include the step of taking the reciprocal in the fifth process the value obtained by performing the addition process on the two second luminous intensity values obtained in the fourth process.

가 일반적인 값들일 때, 제6 과정의 곱셈처리를 실행하기 전에, 상기 제4 과정에서 얻어진 2개의 제2 광도값들에 대하여 감산처리를 행한 후 제6 과정으로 넘겨주는 단계를 더 포함하는 것이 바람직하다.Furthermore, according to another additional feature of the invention,

When is general values, before performing the multiplication process of the sixth process, it is preferable to further include performing a subtraction process on the two second luminous intensity values obtained in the fourth process and then passing over to the sixth process. Do.

The above objects and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings by those skilled in the art.

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

1 is a view showing a schematic configuration of a distance image acquisition device using two images of the present invention, Figure 2 is a schematic view of the configuration of a distance image restoration module in the distance image acquisition device using the two images of FIG. Fig. 3 is a diagram showing the luminosity distribution curves and three pattern images of three sinusoidal phase shifts, and Fig. 4 is a view showing images taken by a camera by projecting the sine wave illumination pattern onto the surface of an object. FIG. 5 is a diagram illustrating a method of taking luminance values at two positions to restore phase in the image of FIG. 4.

Referring to FIG. 1, the object object 100, an illumination module 200 for projecting an illumination pattern onto the object object 100, and a photographing module 300 for acquiring an image of the object object 100. And a distance image restoration module 400 connected to the photographing module 300 to obtain a distance image from the image of the target object 100.

In this case, the illumination module 200 includes an appropriate combination of an illumination source, an illumination pattern, a lens, a mirror, a prism, a filter, and the like, and the photographing module 300 includes an appropriate combination of a camera, a lens, a filter, and the like.

In the illumination module 200, a sine wave pattern as shown in FIG. 3 is projected. The sine wave pattern may be generated by various types of lighting systems such as a beam projector and a grating slide.

In the present invention, when the sine wave pattern is projected from the illumination module 200 to the target object 100, the scene is photographed by the photographing module 300. By this operation, an image as shown in FIG. 4 is obtained, and the distance image restoration module 400 analyzes the image to restore a phase at each point (pixel) of the image and based on the target object. A distance image of is obtained.

)이 위상천이에 따라 달라진다.In the general sinusoidal phase shift method, as shown in FIG.

) Depends on the phase shift.

는 x 위치에서의 위상값,

는 각 위상천이에서의 천이값을 나타낸다. 여기서 3개의 미지수, a, b,

가 있으므로, 위상을 복원하기 위해서는 일반적으로 3개 이상의 식이 필요하다. 즉, 동일 위치에서 얻은 3개 이상의 위상천이 광도 정보가 필요한 것이다.Where a, b are constants, x is a positional coordinate,

Is the phase value at position x,

Represents a transition value in each phase shift. Where three unknowns, a, b,

Therefore, three or more equations are generally required to restore the phase. That is, three or more phase shift luminance information obtained at the same position is required.

The phases of three well known phase shifts can be obtained by the following equation.

이다. 이렇게 해서 일반적으로 3개 이상의 위상천이로 각각의 영상을 얻으면, 이를 통해 각 위치에서의 위상을 복원할 수 있다. 위상을 복원한 뒤에는 적절한 기하학적 보정(geometric calibration)을 통해 거리영상을 획득할 수 있다.Where the three transitions are

to be. In this way, if each image is generally obtained by three or more phase shifts, it is possible to restore the phase at each position. After reconstructing the phase, distance images can be acquired through appropriate geometric calibration.

)를 갖는 정현파 패턴을 사용한다. 이 패턴을 대상 표면에 영사한 후 그 장면을 카메라로 촬영한다. 그 뒤, 상기 거리영상 복원모듈(400)을 통해 상기 대상물체(100)의 거리영상이 획득된다.In the present invention, to restore the phase from the two images. First, a sufficiently high spatial frequency (

Use a sinusoidal pattern with Project this pattern onto the target surface and shoot the scene with a camera. Thereafter, the distance image of the object 100 is obtained through the distance image restoration module 400.

Referring to FIG. 2, the configuration and function of the distance image restoration module 400 will be described in detail. Reference numeral 410 denotes a first luminance value calculator, 420 denotes a first subtracter, and 430 denotes a second. A luminance value calculator, 440 is an adder, 450 is an inverse transformer, 460 is a second subtractor, 470 is a multiplier, and 480 is a distance image reconstruction unit.

First, the illumination module 200 projects a sine wave pattern having a phase difference to each other twice on the object, and the photographing module 300 photographs each resultant image. It is preferable that the said phase difference is (pi). Thereafter, the first luminance value calculator 410 of the distance image reconstruction module 400 calculates the first luminance values at the position x of each image photographed based on Equation 1 below.

In this case, when the phase difference between the sinusoidal patterns is π, the first intensity value calculator 410

First luminous intensity values are obtained.

두면 이차원 좌표로 확장이 가능하다.Where x

It can be expanded to two-dimensional coordinates.

The first subtractor 420 subtracts the remaining value from one of the two values obtained by the first luminance value calculator 410 to calculate a value as shown in Equation 2 below.

에서

로 정의하여 산출된 값이다.Equation 2 is

in

It is calculated by defining.

만큼 떨어진 위치에서의 광도값을 나타내는 아래의 수학식 3을 산출하고 미리 설정된

값 2개를 적용하여 제2 광도값들을 산출한다.The second brightness value calculator 430 has a constant displacement small enough at x based on Equation 2 calculated by the first subtractor 420.

Equation 3 below, which represents the luminance values at the positions separated by

The second luminance values are calculated by applying two values.

만큼 떨어진 위치를 상기 수학식 2에 적용하여

가 되고,

가 충분히 작은 값이므로 근사(approximation)된 수학식 3이 산출된다. 이때,

이고, 형상(geometry)이나 반사특성(reflectance)이 x에서

까지의 영역에서 급격하게 변하지 않는 것으로 가정한다.Referring to the calculation process of Equation 3 in detail, the constant displacement in x

By applying a position separated by

Become,

Since is a sufficiently small value, an approximated equation (3) is calculated. At this time,

Where the geometry or reflection is at x

It is assumed that it does not change drastically in the area up to.

값에 의하여

의 값이 정의되고, 상기

값을

로 두면 아래와 같은 제2 광도값들을 얻을 수 있다.The preset angle

By value

Is defined, and

Value

By setting the second luminance values as follows.

In other words,

Get

The adder 440 adds the second luminance values obtained by the second luminance value calculator 430 to each other.

를 산출한다.The inverse transform unit 450 takes an inverse of the result obtained by the adder 440.

To calculate.

The second subtractor 460 subtracts the remaining value from one of the second luminance values obtained by the second luminance value calculator 430.

The multiplier 470 multiplies the result of the inverse transformer 450 and the result of the second subtractor 460.

That is, the same value as in Equation 4 below is calculated.

일 때, 상기 곱셈기(470)는 상기 덧셈기(440)와 제2 뺄셈기(460) 없이 상기 제2 광도값 산출부(430) 및 역변환부(450)의 결과값을 이용하여 아래의 수학식 5와 같은 계산량이 적은 위상복원 등식에 의해 위상값을 산출할 수 있다.Here, since the spatial frequency of the sine wave pattern can be adjusted in some cases,

In this case, the multiplier 470 uses Equation 5 below without using the adder 440 and the second subtractor 460 using the result values of the second luminance value calculator 430 and the inverse transformer 450. The phase value can be calculated by a phase restoration equation with a small amount of calculation.

이면

가 되고,

이면

가 된다.In other words,

Back side

Become,

Back side

Becomes

는

이므로,

가 되어 상기 수학식 5가 얻어진다.remind

Is

Because of,

Equation 5 is obtained.

The distance image reconstructor 480 obtains the distance image of the target object by performing an appropriate geometric correction based on the phase information obtained through the result value of the multiplier 470.

The present invention is not limited to the above described embodiments, and various modifications and changes can be made by those skilled in the art, which are included in the spirit and scope of the present invention as defined in the appended claims.

For example, the phase restoration method proposed in the present invention and the acquisition of the distance image through the same can also be applied to an interferometer in which two or more sinusoidal patterns overlap. In addition, in order to obtain a more accurate phase and distance image, two or more phase or distance image data are acquired through variation of all the lighting components, all the camera components, and the object, and based on this, more accurate phase or distance image acquisition is obtained. It is possible.

As described above, if the distance image acquisition device and method using the two sine-phase sine wave phase shift based image according to the present invention is applied, it is possible to obtain a relatively accurate phase and distance image based on the phase shift in the two images It is effective.

In addition, it is possible to obtain relatively accurate high resolution phase and distance images from two images in the sinusoidal phase shifting method, which requires at least three images in order to restore the phase. It is possible to obtain a relatively accurate high resolution phase and distance image acquisition in a more easy manner in a short processing time.

In addition, accordingly, there is an effect of increasing the diversity of the field utilizing the phase restoration technology.

Claims (8)

A lighting module for projecting a target object, two different monochromatic sinusoidal patterns of different phases on the target object, and a state in which each lighting pattern is projected on the target object in sequence And a photographing module for acquiring first and second images, and a distance image restoring module connected to the photographing module and processing a photographed image to obtain a distance image, using phase shifting of a sine wave pattern. In the distance image acquisition device for restoring the phase (phase) at each point of the two images to obtain a distance image of the object based on this, The distance image reconstruction module may include: a first luminance value calculator for calculating first luminance values at the same arbitrary position of the first and second captured images; and a first subtraction process for the calculated first luminance values. A subtractor, a second luminance value calculator for calculating second luminance values by applying a value set to the result of the first subtractor, an inverse transformer for performing reciprocal processing on the result of the second luminance value calculator, and the first A multiplier performing a multiplication process on the result of the light intensity calculator and the result of the inverse transform unit, and a distance image restoring unit obtaining a distance image of the object by using phase information obtained through the multiplier result. An apparatus for obtaining distance images using two images based on monochrome sine wave phase shift. The method of claim 1, The distance image reconstruction module includes an adder installed between the second intensity value calculator and the inverse transform unit to perform an addition process on the second intensity values of the second intensity value calculator, and the second intensity value calculator. And a second subtractor disposed between the multipliers and performing a subtraction process on the second luminance values of the second luminance value calculator. 2. . Predetermined spatial frequency (

A first step of projecting a sinusoidal wave pattern having a) to a surface of an object two times by changing a phase through an illumination module and then photographing the scene with a photographing module; A second process of obtaining two first luminance values according to a specific phase difference at an arbitrary point of the image photographed in the first process, according to the following equation;

A third step of subtracting the two first brightness values obtained in the second step to obtain a value such as the following equation;

here,

to be. Two constant displacement values at the point in the equation obtained in the third step

A fourth process of obtaining two second luminance values by the following equation;

Obtained in the fourth step

A fifth process of obtaining a value by taking an inverse of the number; Obtained in the fourth step

Obtained in step 5 and

Performing a multiplication on the reciprocal of to obtain the following equation to restore the phase;

And a seventh process of obtaining a distance image of the target object through geometric correction based on the obtained phase information. The method of claim 3, wherein The distance image acquisition method using two images, characterized in that the phase difference between the sinusoidal patterns in the first step is π. The method of claim 3, wherein The second intensity value given in the fourth process is

Is small enough, the displacement from the point

The following equation for the intensity value given at

Characterized in that the results are approximated by the following equation,

here,

Where the geometry or reflection is at x

Assuming that it does not change abruptly in the area up to

To

Distance image acquisition method using two images, characterized in that the left. The method of claim 3, wherein Two set

The value is a distance image acquisition method using two images, characterized in that the phase difference of π / 2 mutually. The method of claim 3, wherein

Is a general value, adding the two second luminance values obtained in the fourth process to take the inverse of the value obtained in the fifth process. Distance image acquisition method. The method of claim 3, wherein

Is a general value, before performing the multiplication process of the sixth process, performing a subtraction process on the two second luminance values obtained in the fourth process, and then passing the process to the sixth process. Distance image acquisition method using two images.

Images