JP3689720B2 - 3D shape measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a three-dimensional shape measuring apparatus, and more particularly to a three-dimensional shape measuring apparatus for monitoring changes in the height and posture of an object or person in a target area.
[0002]
[Prior art]
Conventionally, as a monitoring device for knowing abnormalities without impairing the privacy of patients in hospital hospitals or toilets, a bright spot arranged in a grid pattern is projected on the monitored area, and the image is taken. , A device that detects the height change of the target area based on the change in position of the bright spot in the captured image from the reference position and monitors the presence / absence, height change, and posture change of objects and people in the target area has been proposed. ing.
[0003]
[Problems to be solved by the invention]
In such a conventional apparatus, the height of an object is calculated by examining the amount of movement of a bright spot when an object is present from the position of the bright spot when no object or the like is present in the monitoring target area. However, the height of the bright spot when the object is present moves to the position of the adjacent bright spot when the object is not present, making it difficult to distinguish the bright spots from each other, and further measurement is possible. There wasn't. FIG. 7A shows the state of the bright spot image when no object is present in the monitoring target area, and FIG. 7B shows that the bright spot at a certain location moves to the adjacent bright spot due to the presence of the object. Show the state. In FIG. 7 (b), the bright spots 111c and 111d have moved and moved to the positions of the adjacent bright spots 111a and 111b in FIG. 7 (a), causing further movement of the bright spots. A height object cannot be measured. For example, if 111c and 111d in FIG. 7B further move to the left, the bright spots cannot be distinguished from 111a and 111b.
[0004]
Therefore, an object of the present invention is to provide a three-dimensional shape measuring apparatus using a bright spot with a wide height measurement range of a monitoring object.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, a three-dimensional shape measuring apparatus 10 according to the first aspect of the present invention has a first direction (y′-axis) in an imaging region 2 where an imaging target object 1 is placed, for example, as shown in FIG. In a lattice pattern with a constant interval a in the direction (FIG. 2) and a constant interval b larger than the interval a in the second direction (x′-axis direction) perpendicular to the first direction (y′-axis direction). Projecting means 12 for projecting a plurality of arranged bright spots 13a; projected onto an imaging region 2 on which the imaging object 1 is placed, which is installed in a predetermined direction (y-axis direction) when viewed from the projecting means 12; An imaging unit 11 that images a plurality of bright spots 13a; a shape calculation that calculates a three-dimensional shape of the imaging target 1 by comparing the bright spot image 1a ′ captured by the imaging unit 11 with the reference image 2a ′ An angle θ formed by a predetermined direction (y-axis direction) and the first direction (y′-axis direction) is n When a natural number, approximately equal to arctan (b / (a · n)), and when the diameter of the bright spot is is c, said angle is configured to be larger than arcsin (c / a).
[0006]
The reference image is typically an image obtained by imaging a bright spot projected on an imaging area where an imaging object is not placed. Here, the bright spot image and the reference image are not limited to image images, and may be based on coordinates that specify the position of the bright spot.
[0007]
With this configuration, a lattice is formed at a constant interval a in the first direction (y′-axis direction (FIG. 2)) and at a constant interval b greater than the interval a in a second direction perpendicular to the first direction. And projecting a plurality of bright spots projected on the imaging area 2 on which the imaging target object 1 is placed, which is installed in a predetermined direction when viewed from the projection means. Imaging means. The angle between the predetermined direction and the first direction is approximately equal to arctan (b / (a · n)), where n is a natural number, and when the diameter of the bright spot is c, the angle is Since it is configured to be larger than arcsin (c / a), the measurement range of the imaging target can be further expanded.
[0008]
Further, as described in claim 2 and, for example, as shown in FIG. 2, in the three-dimensional shape measuring apparatus 10 according to claim 1, the projection unit 12 includes a light source L that generates coherent light L <b>1; And two diffraction gratings 13 that allow the coherent light L1 generated in step 1 to pass through; the two diffraction gratings 13 are arranged so that their diffraction directions are substantially orthogonal to each other.
[0009]
Further, as described in claim 3, the diffraction grating 13 may be a fiber grating. The coherent light that has passed through the diffraction grating generates a pattern by interference. In addition to the fiber grating, the diffraction grating may be, for example, a slit plate obtained by cutting a plurality of slits in parallel, or a cylindrical lens array. Further, instead of the two cylindrical lens arrays, a microlens array may be used.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In addition, in each figure, the same code | symbol or a similar code | symbol is attached | subjected to the mutually same or equivalent member, and the overlapping description is abbreviate | omitted.
[0011]
FIG. 1 is a conceptual perspective view showing an overall image of a three-dimensional shape measuring apparatus 10 according to an embodiment of the present invention. In the figure, a measurement object or a rectangular parallelepiped object 1 as an imaging object is placed on a plane 2 as a measurement object area or an imaging object area. The orthogonal coordinate system XYZ is taken so that the XY axis is placed in the plane 2, and the object 1 is placed in the first quadrant of the XY coordinate system. A person may be used as an imaging object instead of an object.
[0012]
On the other hand, an imaging optical system 11 as an imaging means is disposed above the plane 2 on the Z axis in the figure. Here, for the sake of convenience, the imaging optical system is illustrated as being composed of one convex lens 11a as an imaging lens. The imaging lens 11a of the imaging optical system 11 is arranged so that its optical axis coincides with the Z axis. An imaging plane (image plane) 15 on which the imaging lens 11a forms an image of the plane 2 or the object 1 is a plane orthogonal to the Z axis. An xy orthogonal coordinate system is taken in the image plane 15 so that the Z axis passes through the origin of the xy coordinate system.
[0013]
A fiber grating (FG) element 13 is disposed at an equal distance from the plane 2 with the imaging lens 11a and a distance d away from the imaging lens 11a in the negative direction of the Y axis. A luminescent spot projecting optical system 12 as a projecting unit is configured including the FG element 13. Here, a line connecting the center of the imaging plane 15 and the center of the FG element is called a base line. The baseline is directed in the y-axis direction, and d is the distance in the baseline direction (baseline length). As will be described later with reference to FIG. 2, the laser beam L1 generated by the light source L is incident on the FG element 13 in the Z-axis direction, and a pattern 13a in which dots are arranged in a lattice shape is irradiated onto the plane 2 Is done. That is, the object 1 and the plane 2 are illuminated with the pattern illumination light. The imaging optical system 11 is electrically connected with a computer 14 as image processing means. The shape calculation means is built in the computer 14. That is, for example, an arithmetic program installed in a storage unit such as a hard disk or a RAM.
[0014]
Further, the principle of three-dimensional shape measurement will be described with reference to FIG. In the bright spot pattern 13a projected onto the plane 2 by the FG element 13 described in detail later, a portion where the object 1 exists is blocked by the object 1 and does not reach the plane 2. Here, if the object 1 does not exist, the bright point to be projected to the point 2a (X, Y, Z) on the plane 2 is projected to the point 1a (X1, Y1, Z1) on the object 1. When the bright spot is moved from the point 2a to the point 1a and the imaging lens 11a and the FG element 13 are separated from each other by the distance d, the point on the imaging plane 15 is connected to the point 2a ′ (x, y). A place to be imaged is imaged at a point 1a ′ (x, y + δ). That is, it moves by a distance δ in the y-axis direction. Actually, if the point 1a ′ is not a point on the y-axis, it moves by δx also in the x-axis direction, but the display thereof is omitted here.
[0015]
By measuring this δ, the position of the point 1a on the object 1 can be specified three-dimensionally. Thus, if a certain bright point does not exist, the difference between the point to be imaged on the imaging plane 15 and the actual imaging position on the imaging plane 15 is measured. The three-dimensional shape of the object 1 can be measured. Alternatively, it may be said that the three-dimensional coordinates of the object 1 can be measured. If the pitch of the pattern 13a, that is, the pitch of the bright spot is made fine enough that the correspondence of the bright spot is not unknown, the three-dimensional shape of the object 1 can be measured in detail.
[0016]
The center of the FG element 13 and the center of the imaging lens 11a are arranged parallel to the plane 2 by a distance d, and the distance from the imaging lens 11a to the imaging plane 15 is 1 (el) (as an imaging lens). The distance from the imaging lens 11a to the plane 2 is h, and the height of the point 1a of the imaging object 1 from the plane 2 is Z (shown as Z1 in FIG. 1). As a result of the imaging object 1 being placed on the plane 2, the point 2 a ′ on the image plane 15 has moved to a point 1 a ′ separated by δ.
In such a relationship, Z is expressed by an expression including δ as in Expression 1 below. By using this equation, the posture of a person in the toilet can be known three-dimensionally.
Z = (h ² · δ) / (d · l + h · δ) Equation 1
[0017]
The FG element 13 will be described with reference to FIG. The FG element 13 is formed by arranging about 100 optical fibers having a diameter of several tens of microns and a length of about 10 mm in a sheet shape, and superposing them so that two fibers are orthogonal to each other. In the FG element, the sheet is arranged in parallel to the plane 2 (perpendicular to the Z axis). Laser light L1 generated by the laser light source L is incident on the FG element 13 in the Z-axis direction. Then, the laser beam L1 is collected at the focal point of each optical fiber, then spreads as a spherical wave, interferes, and shines in a square lattice pattern on the plane 2 which is a projection surface as a measurement region or an imaging region. A bright spot pattern 13a which is a point matrix is projected. In other words, the plane 2 or the object 1 thereon is illuminated with the bright spot pattern illumination light by projecting the bright spot pattern 13a.
[0018]
According to such an FG element 13, it is possible to obtain a sharp illumination pattern with good contrast of point light (bright spot) regardless of the distance from the grating due to the light diffraction effect, which is suitable for pattern imaging. It is. When such an FG element is used, the three-dimensional shape can be measured simply by measuring and calculating the amount of movement of the bright spot, so that the measurement of the three-dimensional shape can be realized with a relatively simple calculation means. Further, since the amount of light can be concentrated, it is possible to easily capture an illumination pattern (here, bright spots) even in a bright surrounding.
[0019]
The optical fiber of the FG element 13 does not necessarily face the base line direction (the y-axis direction in the figure), and the rotation axis is an axis parallel to the xy plane and parallel to the Z-axis direction passing through the center of the FG element 13. , Θ is rotated. In the figure, if the coordinates parallel to the orthogonal optical fiber are x′y ′ coordinates, the y ′ axis is inclined with respect to the y axis and the x ′ axis is inclined with respect to the x axis by an angle θ. That is, the angle formed by one lattice direction and the base line is θ.
[0020]
Here, the interval in the direction parallel to the y ′ axis of the lattice-like bright spot pattern on the plane 2 is a, and the interval in the direction parallel to the x ′ axis is b. The diameters of the orthogonal optical fibers are substantially equal to each other. However, when the diameter of the optical fiber in the y′-axis direction is larger than the diameter of the optical fiber in the x′-axis direction, the interval between the bright spots of the bright spot pattern is a <B. The bright spot pattern in FIG. 1 shows a case where θ = 0.
[0021]
FIG. 3 is a bright spot image when an FG element having bright spot intervals of a and b (a <b) is used. Such a bright spot image can be realized by using elements having different fiber diameters, that is, fiber pitches in the vertical and horizontal directions of the FG element as described with reference to FIG. Since the calculation formula of the position of the bright spot by the laser and the FG element can be considered similarly to the formula of interference fringes due to interference by multiple slits as shown in the following formula 2, if the slit interval p, that is, the fiber pitch is changed, the interference The stripe spacing can be changed. Here, y _m is the y-axis direction position providing periodic sharp maxima, m is a natural number, lambda is the distance of the wavelength of light, h is from FG element to the illumination surface (the plane of the imaging area), p is the slit spacing To do.
y _m = m · λ · h / p Equation 2
[0022]
The angles formed by the lattice direction having a short luminescent spot interval in the luminescent spot array (the interval is a in FIG. 3) and the base line can be set as θ0, θ1, θ2,. In FIG. 3, for the sake of explanation, up to θ4 is shown, and illustration of θ5 and above is omitted. By setting the direction of the base line in this way, the interval between a certain bright spot and the adjacent bright spot in the base line direction can be increased, and the height measurement range of the object 1 can be widened. If the size of the bright spot is ignored, the distance from the adjacent bright spot is expressed by the following formula.
For θ0: a
In the case of θ1 (a ² + b ² ) ^1/2
In the case of θ2 ((2 · a) ² + b ² ) ^1/2
In the case of θ3: ((3 · a) ² + b ² ) ^1/2
In the case of θ4: ((4 · a) ² + b ² ) ^1/2
[0023]
As described above, when the grid is tilted with respect to the base line, the distance between adjacent bright spots is larger than when the grid is not tilted. Here, even when the luminescent spot is sufficiently small, n of θn is not actually infinite, but is limited by the spot diameter of the luminescent spot, fluctuation, or the like. Here, θ is expressed by a general formula as follows. When θ is substantially equal to such a value, the distance from the adjacent bright spot can be increased.
θ = arctan (b / (a · n)) Equation 3
[0024]
With such a configuration, the decrease in the number of bright spots per unit area can be reduced compared to the method of expanding the height measurement range by simultaneously increasing the bright spot interval in the vertical and horizontal directions of the bright spot array, Since the object height measurement points are less sparse, more accurate three-dimensional measurement of the object becomes possible. Further, since the baseline length d is not changed, the height measurement range can be expanded without lowering the sensitivity of the low height.
[0025]
When a <b, as described below with reference to FIG. 4, even when the bright spot lattice direction is tilted with respect to the base line and the interval between adjacent bright spots in the base line direction is increased, the bright spot position is moved by the object. Sometimes it is possible to avoid hitting a bright spot other than the adjacent bright spot.
[0026]
An embodiment of the present invention will be described with reference to FIG. In the figure, the bright spot interval has a relationship of a <b, and the angle between the direction of the interval a and the base line is θ = arctan (b / (3 · a)). In the case of such an arrangement of the base line and the bright spot grid, the bright spot 0 at the lower left corner in the figure moves in the direction of the bright spot 1 at the position of the fourth row from the left in the second row in accordance with the height of the object. However, in the middle of this, there is a possibility that it is located immediately next to the bright spot 2 in the second column from the left in the drawing (or the bright spot 3 in the second row from the left in the drawing to the third column). As shown in the figure, when the bright spot lattice spacing is defined as a and b, and the bright spot diameters c and n are natural numbers, the gap s between the bright spots when the bright spot 0 is closest to the bright spot 2 is shown. Is expressed by the following equation.
s = a · b / ((a · n) ² + b ² ) ^1/2 −c Equation 4
[0027]
For example, when a = b = 5 mm and c = 1 mm, the distance l ₀₁ (el) between the bright spots 0-1 obtained by subtracting the size of s and the bright spots is as shown in Table 1 of FIG. Thus, when n = 5 or more, it can be seen that the bright spots overlap and it is difficult to distinguish. In order to avoid this, s> 0 may be set in Equation 4. In other words, the following equation should be satisfied.
θ> arcsin (c / a) Equation 5
[0028]
Here, if b is changed to 8 mm (> a = 5 mm), as shown in Table 2 of (b), if there is no influence of noise or the like, the angle can be reduced to an angle of n = 7. At this time, the value of l ₀₁ is also increased, indicating that the height measurement range is expanded. Thus, by using bright spot images with different bright spot intervals in the vertical and horizontal directions, adjacent bright spots in the baseline direction can be extended, and the height measurement range can be expanded.
[0029]
As described above with reference to FIG. 3, when the angles are made shallower with θ1, θ2, θ3,... (But not 0 degrees), the distance between adjacent bright spots in the base line direction increases, and the height measurement range is increased. Although it can be magnified, this angle cannot actually be made too shallow due to the size of the bright spot. Therefore, the angle can be made shallow by arranging the bright spots as described in FIG.
[0030]
In the embodiments described so far, FG (fiber grating) elements having different fiber diameters in the vertical and horizontal directions are used to realize the bright spot array having different lattice spacings. This can also be realized by stacking two original diffraction gratings so that the gratings are orthogonal to each other. In this case, different diffraction grating pitches are used so that the lattice spacing of the bright spots is different vertically and horizontally. A bright spot made using a diffraction grating or an FG element is suitable because it has less blur and is hardly affected by the distance between the element and the object. In the case of an FG element, since there is no place to be shielded and most of the light incident on the FG element can be used for generating a bright spot, it is highly energy efficient and suitable.
[0031]
Furthermore, as shown in the plan view of FIG. 6A and the schematic configuration diagram of the microlens array shown in the AA sectional view, a microlens array (MLA) in which small lenses are laid vertically and horizontally without gaps may be used. realizable. In this case as well, the lattice spacing of the bright spots can be made different vertically and horizontally by using elements having different lens pitches in the vertical and horizontal directions. Such an MLA is suitable because it can be easily manufactured by pressing with a mold using a synthetic resin as a material. If an MLA having no gap between the lenses as shown in the figure is used, most of the incident light beam can be used for generating a bright spot, which is preferable because of high energy efficiency.
[0032]
Further, as shown in the plan view of FIG. 6B and the schematic configuration diagram of the micro cylindrical lens array shown in the BB cross-sectional view, a micro cylindrical lens having a configuration similar to the FG element and in which small cylindrical lenses are arranged without gaps. Two arrays may be stacked. At this time, between the two arrays, it is preferable that the directions having refractive power are substantially orthogonal to each other. That is, it arrange | positions so that each diffraction direction may cross substantially orthogonally. In this case, too, two overlapping arrays having different lens pitches are used so that the lattice spacing of the bright spots is different vertically and horizontally.
[0033]
The above-described three-dimensional shape measuring apparatus according to the embodiment of the present invention is used in, for example, a toilet in an elderly care facility, and when an abnormality occurs in the toilet, the abnormality is not impaired without compromising privacy. Can be detected.
[0034]
Moreover, it is good also considering the use wavelength of a light source as wavelengths other than visible light. If comprised in this way, when the imaging target object is a person, it can image without being noticed by the person who becomes object.
[0035]
As an example of the image sensor, a CMOS structure element may be used in addition to the CCD. In particular, some of the elements themselves have inter-frame difference calculation and binarization functions, and it is preferable to use these elements.
[0036]
【The invention's effect】
As described above, according to the present invention, the data are arranged in a lattice pattern at a constant interval a in the first direction and at a constant interval b larger than the interval a in the second direction perpendicular to the first direction. Projection means for projecting a plurality of bright spots, and imaging means for imaging a plurality of bright spots projected in an imaging area on which the imaging object 1 is placed, which is installed in a predetermined direction when viewed from the projection means. The angle between the predetermined direction and the first direction is approximately equal to arctan (b / (a · n)), where n is a natural number, and when the diameter of the bright spot is c, the angle is Since it is comprised so that it may be larger than arcsin (c / a), it becomes possible to provide the three-dimensional shape measuring apparatus which expanded the measurement range of the imaging target object.
[Brief description of the drawings]
FIG. 1 is a conceptual perspective view of a three-dimensional shape measuring apparatus according to an embodiment of the present invention.
FIG. 2 is a conceptual perspective view illustrating an FG element used in the embodiment of FIG.
FIG. 3 is a plan view showing an angle formed between a bright spot group and a base line.
4 is a plan view for explaining by extracting θ3 of FIG. 3; FIG.
FIG. 5 is a diagram showing a table of bright spot intervals and distances between two bright spots in an example of the present invention.
FIG. 6 is a schematic diagram showing a microlens array and a microcylindrical lens array among diffraction gratings that can be used in the embodiment of the present invention.
FIG. 7 is a plan view showing a bright spot image when there is no object and an image with a bright spot that moves to an adjacent bright spot by the object.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Imaging target object 2 Imaging region 10 Three-dimensional shape measuring apparatus 11 Imaging optical system 11a Imaging lens 12 Projection optical system 13 FG element 15 Imaging surface 14 Image processing apparatus

Claims (3)

In the imaging area where the imaging object is placed, the pixels are arranged in a grid pattern at a constant interval a in the first direction and at a constant interval b larger than the interval a in a second direction perpendicular to the first direction. Projection means for projecting a plurality of bright spots;
Imaging means for imaging a plurality of bright spots projected on an imaging area where the imaging object is placed, which is installed in a predetermined direction when viewed from the projection means;
Comprising a shape calculation means for calculating a three-dimensional shape of the imaging object by comparing a bright spot image captured by the imaging means with a reference image;
The angle formed between the predetermined direction and the first direction is substantially equal to arctan (b / (a · n)), where n is a natural number, and when the diameter of the bright spot is c, the angle Is greater than arcsin (c / a);
Three-dimensional shape measuring device. A light source for generating coherent light;
Two diffraction gratings for passing coherent light generated by the light source;
The two diffraction gratings are arranged such that their diffraction directions are substantially orthogonal;
The three-dimensional shape measuring apparatus according to claim 1. The three-dimensional shape measuring apparatus according to claim 2, wherein the diffraction grating is a fiber grating.

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