KR100901536B1 - 3-d measuring method by using wide band reference phase - Google Patents

Abstract

A three-dimension measuring method in which a wide band reference phase is applied is provided to broaden measurement area and to increase measurement performance. A three-dimension measuring method in which a wide band reference phase is applied is composed of steps of: projecting lattice patterns having a constant cycle to the measurement object; obtaining an image of the projected lattice patterns; projecting lattice patterns to the measurement object after moving lattice patterns; obtaining an image of the projected lattice patterns; projecting the even multiplication of lattice patterns to the measurement object; obtaining an image of the projected lattice patterns; calculating the folded phase of the measurement object by using lattice patterns having a constant cycle; calculating the space code value of the measurement object by using the even multiplication of lattice patterns; and calculating the phase of the measurement object by applying the folded phase and the space code value.

Description

3-D measuring method using wideband reference phase {3D measuring method by using wide band reference phase}

The present invention relates to a three-dimensional measurement method using a broadband reference phase, and more particularly, to project a certain period of time gratings and grids having an even multiple of the same period to any measurement object to obtain the projected image The present invention relates to a measurement method that increases the measurement resolution and widens the measurement area by combining the moiré measurement method and the spatial encoding method by measuring the spatial coding method and the moire measurement method.

Recently, if we look around us, the three-dimensional shape measurement techniques that have been partially used for quality inspection of products or detection of defective products in assembly lines are not limited to the engineering field, but the medical, film and entertainment industries. It is not difficult to find a way to expand the scope of application to the fields that are more closely related to our lives, such as clothing and clothing industry.

Three-dimensional shape measurement has already established itself as an important field in the engineering field, and more demand is being generated in the element of engineering.

In the medical field, three-dimensional shape measurement technology has been used effectively to check the abnormality of the body through three-dimensional shape measurement of the human body, and to restore the bone shape perfectly in the big accidents in which the bone is damaged.

In the film industry, the difficult acts that are impossible for humans to do or pose a lot of risks are different from those used in stuntmen in the past. The actor's body is measured through 3D shape measurement, and CAD is used in computer graphics. This solves many problems.

In addition, in the entertainment and character industries, three-dimensional shape measurement technology is effectively used for more natural and natural movement and appearance.

In recent years, the scope of application is rapidly increasing, such as the three-dimensional shape measurement of the consumer's body shape and the recommendation of the most suitable clothes or shoes for the consumer by extending the scope to the clothing and footwear industries. In order to meet the demands of the recent three-dimensional shape measurement technology, high speed, high precision, and non-contact measurement have emerged as indispensable elements.

The moire technique and the spatial encoding method are widely used in the high speed and high precision non-contact measurement.

The moiré technique is a measurement technique that is widely used for precise measurement such as PCB substrates and semiconductors, and specific measurement techniques are described in detail in Korean Patent Publication No. 2000-75148. The air coding method is also described in detail in Korean Laid-Open Publication No. 2001-54287.

Figure 1 is a simplified illustration of the prior art, the projection of the grid pattern having a predetermined period on the reference plane, and then moving the position of the grid to obtain an image and obtain the phase of the reference plane therefrom, and similarly to the measurement object Projection results in the phase of the measurement object.

However, since the moiré technique measures under the assumption that the object is continuous, it is possible to measure the phase of adjacent positions between -π and + π, but the measurement resolution is higher than that of the spatial coding method. This narrow and spatial coding method, on the other hand, has a low measurement resolution but a wide measurement range.

Attempts have been made to combine the moiré technique with the spatial coding method to increase the measurement resolution and widen the measurement area. However, the measurement takes a lot of time because the moiré technique and the spatial coding method are measured differently.

Therefore, the present invention has been devised to solve the above problems, and the grid pattern having a period applied to the moiré technique and the even pattern of the grid pattern having an even multiple of the period while being applied to the spatial encoding method is projected to By measuring the gratings obtained from the Moire technique and the spatial coding method, it provides a measurement method that increases the measurement resolution and widens the measurement area.

In addition, the present invention solves the problem that the limitation of the moiré measurement technique, that is, the phase of the adjacent position of the measurement object must exist between -π and + π by applying the spatial coding method.

The present invention for achieving the above object, the step of projecting a grid pattern having a predetermined period (λa) to the measurement object to obtain the measurement object phase (Po) of the measurement object; and the image of the grid pattern projected on the measurement object And obtaining a projected grid pattern by moving the grid pattern having a predetermined period (λa) to the measured object; and obtaining an image of the projected grid pattern by moving the measured object; Projecting a lattice pattern having an even multiple of λ a to a measurement object; and obtaining an image of the lattice pattern having an even multiple of λ a projected onto the measurement object; Obtaining a folded phase Pa of an object to be measured using a lattice pattern having a predetermined period λa; and using a lattice pattern having an even multiple of λa. Obtaining a spatial code value (Na); and obtaining the measured object phase (Po) of the measurement object by applying the obtained folded phase (Pa) and the spatial code value (Na). A pattern and a phase of the object to be measured are obtained by applying a grid pattern having a repeating cycle in the ON / OFF form.

In addition, the present invention comprises the steps of projecting a grid pattern having a predetermined period (λa) to the reference plane to obtain a reference phase (Pr) of the reference plane; and obtaining an image of the grid pattern projected on the reference plane; and Moving a lattice pattern having a predetermined period λa to be projected onto the reference plane; and moving the lattice pattern to the reference plane to obtain an image of the projected lattice pattern; The method may include: projecting a lattice pattern with an even multiple of λa to a measurement object; and obtaining an image in which the lattice pattern with an even multiple of λa is projected onto the measurement object; and the obtained constant period (λa) Obtaining a folded phase Pa of the reference plane by using a lattice pattern having;) and obtaining a spatial code value Na of the reference plane by using a lattice pattern of which the period is an even multiple of λa; and the Obtaining the reference phase (Pr) of the reference plane by applying the folded folded phase (Pa) and the space code value (Na), including the moiré from the difference between the measured phase (Po) and the reference phase (Pr) Obtain the phase Pm.

As described above, the three-dimensional measurement method according to the present invention projects a grid pattern having a period corresponding to a moiré technique and a spatial encoding method and a grid pattern having an even multiple of the period to a measurement object and obtains the grids obtained therefrom. It is effective to increase the measurement resolution and widen the measurement area by applying to moiré method and spatial coding method.

In addition, the present invention has the effect of raising the measurement area by applying a spatial coding method that must be present between the limits of the moiré measurement technique, that is, the phase of the adjacent position of the measurement object from -π to + π.

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

This embodiment is not intended to limit the scope of the present invention, but is presented by way of example, various modifications may be made without departing from the technical spirit thereof.

The present invention comprises the steps of: projecting a grid pattern having a predetermined period (λa) to the measurement object to obtain the measurement object phase (Po) of the measurement object; and obtaining an image of the grid pattern projected on the measurement object; and Moving a lattice pattern having a predetermined period λa to be projected onto the measurement object; and obtaining an image of the projected lattice pattern by moving to the measurement object; and lattice pattern in which the brightness change is repeated in the ON / OFF form Wherein the period is a step of projecting a lattice pattern of even multiples of λa to the reference plane; and obtaining an image of the lattice pattern of even multiples of λa projected onto the reference plane; and the obtained constant period (λa Obtaining a folded phase Pa of the measurement object by using a lattice pattern having?) And calculating a spatial code value Na of the measurement object by using a lattice pattern of which the period is an even multiple of λa. And a step of obtaining the measured object phase (Po) of the measurement object by applying the obtained folded phase (Pa) and the space code value (Na). By applying a lattice pattern having a repetitive period to obtain the measured object phase (Po) of the measurement object.

In addition, the present invention comprises the steps of projecting a grid pattern having a predetermined period (λa) to the reference plane to obtain a reference phase (Pr) of the reference plane; and obtaining an image of the grid pattern projected on the reference plane; and constant Moving a lattice pattern having a period λa and projecting it onto a reference plane; and moving the lattice pattern to a reference plane to obtain an image of the projected lattice pattern; and lattice pattern in which brightness variation is repeated in an ON / OFF form. Projecting a grid pattern of even multiples of λa to a measurement object; and obtaining an image in which the grid pattern of even multiples of λa is projected onto the measurement object; and the obtained constant period λa Obtaining a folded phase Pa of the reference plane using a lattice pattern having a shape; and obtaining a space code value Na of the reference plane using a lattice pattern of which the period is an even multiple of λa; and the phrase Obtaining the reference phase (Pr) of the reference plane by applying the folded folded phase (Pa) and the space code value (Na), including the moiré from the difference between the measured phase (Po) and the reference phase (Pr) Obtain the phase Pm.

The folded phase Pa is referred to as the folded phase because the measured phase value exists between −π and + π.

Hereinafter, the grid pattern projected on the measurement object or the reference plane will be described.

In the step of projecting a pattern having a certain period (λa) on the measurement object or the reference plane, the first to third grid patterns are projected. The first pattern is a regular stripe pattern in which the brightness variation is repeated in a sine wave shape. The first pattern is a pattern shifted by 1/3 of λa in the first pattern, and the third pattern is a pattern shifted by 2/3 of λa in the first pattern.

In the step of projecting a lattice pattern with an even multiple of λa, the 4th to 6th lattice pattern is projected, and the 4th pattern is λa in the step of projecting a lattice pattern with an even multiple of λa. The 5th pattern is 4 times the ON / OFF period is λa, and the 6th pattern is the 8 times of the ON / OFF period is λa. After projecting the 1st to 6th patterns, Acquire images of the first to sixth patterns.

2 is a diagram showing each grid pattern. As described above, the first to third grating patterns have the same period λa, but the fourth to sixth grating patterns have an even multiple of λa.

Hereinafter, the steps for obtaining the folded phase value Pa will be described.

In the step of obtaining the folded phase value Pa,

식을 적용해서 구하되

To find the equation

here

IR ₁ : Pixel brightness of the image obtained from the first pattern

IR ₂ : Pixel brightness of the image obtained from the second pattern

IR ₃ : Pixel brightness value of the image obtained from the third pattern

  to be.

3 shows a folded phase Pa obtained from + π to -π for a measurement object having a length in an arbitrary direction (x direction), and it can be seen that it exists between + π and -π.

The folded phase Pa is named above because the calculated phase is between + π and -π.

The steps for obtaining the space code value Na will be described below.

Finding the space code value (Na)

를 적용해서 구하되

Apply to find

here

Iavg = (I ₁ + I ₂ + I ₃ ) / 3,

I ₁ : Pixel brightness of the image obtained from the first pattern

I ₂ : Pixel brightness of the image obtained from the second pattern

I ₃ : Pixel brightness of the image obtained from the third pattern

Ib ₄ : Binary value assigned as “1” if the brightness value obtained from the pixel of the image obtained in the 4th pattern is larger than the corresponding pixel Iavg.

Ib ₅ : Binary value that is assigned as “1” if the brightness value obtained from the pixel of the image obtained in the fifth pattern is larger than the corresponding pixel Iavg.

Ib ₆ : Binary value that is assigned as “1” if the brightness value obtained from the pixel of the image obtained in the 6th pattern is larger than the corresponding pixel Iavg.

to be.

4 shows a space code value Na, which varies depending on the shape according to the fourth to sixth pixel values, and has a value between 0 and 7. FIG.

Then, the present invention calculates the measurement phase Po of the measurement object, and obtains the folded phase value Pa obtained from the measurement object + 2π × the space code value Na obtained from the measurement object.

That is, the measurement phase (Po) of the measurement object = folded phase value (Pa) obtained from the measurement object + [2π × space code value (Na) obtained from the measurement object].

The reference phase Pr of the reference plane can be obtained in the same manner, that is, the reference phase is obtained by the folded phase value Pa obtained from the reference plane + 2π × the spatial code value Na obtained from the reference plane.

That is, the reference phase Pr of the reference plane = the folded phase value Pa obtained from the reference plane + [2π × space code value Na obtained from the reference plane].

Next, the present invention obtains the moiré phase value (Pm), which is calculated as the difference between the measured object phase (Po) and the reference phase (Pr) of the reference plane, that is, Pm = Po-Pr (Pm <-π). In this case, (Pm + 16) is set as the Pm value, and (Pm> +15?), The (Pm-16?) Is determined as the moiré phase value Pm.

Since the moiré phase value Pm corresponds to the same shape as the actual shape of the measurement object, the height value of the measurement object can be known.

5 shows the shape of the measured object, except for the inclination value, to obtain the actual shape of the measured object.

As described above, the present invention not only performs fast measurement but also measures resolution by projecting a lattice pattern having a constant period and an even multiple of the period to the measurement object and applying the moiré technique and the spatial coding method from the obtained grid pattern. The height relates to a measuring method which simultaneously widens the measuring area.

  In the present invention, only three grid patterns, which are the fourth to sixth patterns, are used as the spatial coding pattern, but it is naturally the same as that of the present invention to expand the measurement area by adding the pattern.

In addition, in the present invention, only three grid patterns, which are the first to third patterns, are used to obtain the folded phase Pa, but the addition of the grid pattern is, of course, substantially the same as the present invention.

In addition, although the spatial coding pattern of the binary code concept is used as a means of unfolding the folded phase in the present invention, it is a well-known technique to calculate a spatial code value using a gray code. Naturally, it is also substantially the same as this invention.

1 is a view showing a prior art,

2 is a view showing a grid pattern according to the present invention,

3 shows a folded phase Pa according to the invention,

4 is a diagram showing a space code value Na according to the present invention.

5 is a diagram showing the obtained moiré phase value Pm according to the present invention.

<Description of Symbols for Main Parts of Drawings>

Claims (7)

 In the three-dimensional measuring method having an arbitrary shape, Projecting a grid pattern having a predetermined period [lambda] a onto the reference plane; Obtaining an image of the grid pattern projected on the reference plane; Moving a grid pattern having a predetermined period λa and projecting the grid pattern to a reference plane; Moving to the reference plane to obtain an image of the projected grid pattern; Projecting a lattice pattern in which the brightness change is repeated in the ON / OFF form, the period of which is projected on the reference plane a lattice pattern of an even multiple of? A; Acquiring an image of the grid pattern whose period is an even multiple of lambda a projected onto a reference plane; Obtaining a folded phase Pa of a reference plane using the obtained grid pattern having a predetermined period λa; Obtaining a space code value (Na) of a reference plane by using a lattice pattern of which the period is an even multiple of lambda a; Obtaining a reference phase Pr of a reference plane by applying the obtained folded phase Pa and a space code value Na; And     Projecting a grid pattern having a predetermined period [lambda] a onto the measurement object; Obtaining an image of the grid pattern projected on the measurement object; Moving the grid pattern having a predetermined period λa and projecting the same to a measurement object; Moving to the measurement object to obtain an image of the projected grid pattern; Projecting a grid pattern having a brightness change repeated in the ON / OFF form, the period being an even multiple of? A to the measurement object; Obtaining an image of the grid pattern having the period of an even multiple of lambda a projected onto the measurement object; Obtaining a folded phase Pa of an object to be measured using the obtained grid pattern having a predetermined period λa; Obtaining a spatial code value (Na) of the measurement object by using a lattice pattern of which the period is an even multiple of lambda a; Obtaining the measured object phase (Po) of the measurement object by applying the obtained folded phase (Pa) and the space code value (Na); three-dimensional measurement method applying a wideband reference phase comprising a. delete The method of claim 1 In the step of projecting a pattern having a certain period (λa) on the measurement object or the reference plane, the first to third grid patterns are projected. The first pattern is a regular stripe pattern in which the brightness variation is repeated in a sine wave shape. The first pattern is a pattern shifted by 1/3 of λa in the first pattern, and the third pattern is a pattern shifted by 2/3 of λa in the first pattern, and has a lattice pattern in which brightness variation is repeated ON / OFF. In the step of projecting a lattice pattern with an even multiple of λa, the fourth and sixth lattice patterns are projected, with the fourth pattern being twice the ON / OFF period of λa and the fifth pattern being the ON / OFF period. Is 4 times λa, and the 6th pattern has ON / OFF period 8 times λa, And projecting the first to sixth patterns and then obtaining images of the first to sixth patterns by using a color camera. delete The method of claim 3. Obtaining the space code value Na obtained from the above

Apply to find here Iavg = (I1 + I2 + I3) / 3, I ₁ : Pixel brightness of the image obtained from the first pattern I ₂ : Pixel brightness of the image obtained from the second pattern I ₃ : Pixel brightness of the image obtained from the third pattern Ib ₄ : The brightness value obtained from the pixels of the image obtained in the fourth pattern is equal to that of the corresponding pixel. If the value is large, it means “1”. If the value is small, it means “0”. Ib ₅ : The brightness value obtained from the pixels of the image obtained in the fifth pattern is equal to that of the corresponding pixel. If the value is large, it means “1”. If the value is small, it means “0”. Ib ₆ : The brightness value obtained from the pixels of the image obtained in the sixth pattern is If the value is large, it means “1”. If the value is small, it means “0”. Three-dimensional measurement method applying a broadband reference phase characterized in that. The method of claim 5 The measured phase (Po) of the measuring object is the folded phase value (Pa) + obtained from the measuring object. A three-dimensional measurement method using a broadband reference phase, characterized in that obtained by the space code value (Na) obtained from a measurement object. The method of claim 6 The moiré phase value (Pm) is the reference phase of the measured object phase (Po) and the reference plane of the measurement object. Obtain the difference between phases (Pr), that is, Pm = Po-Pr.If (Pm <-π), (Pm + 16π) is the Pm value, and if (Pm> + 15π), (Pm-16π) is the Pm value. Three-dimensional measurement method applying a broadband reference phase, characterized in that.

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