JPS59606A - Discriminating method of distance, shape or the like using fiber grating - Google Patents

Abstract

PURPOSE:To discriminate the distance, shape, etc., of an object from a spot distribution state by allowing two fiber gratings to cross each other closely at right angles, and irradiating one surface with laser light and the object with a diffracted spot from the other surface. CONSTITUTION:The fiber gratings 2a and 2b formed by arraying numbers of optical fibers without any gap cross each other closely at right angles form a spot array projection part 5, which is irradiated with the laser beam to L to radiate light beams Lb in a secondary spot array to the object. When the object is at a long distance, one-several diffracted spots P reach the object and when the object is at a short distance, numbers of spots P are projected, so the number of spots P is counted by a photodetector 8 to know the distance. Further, the size is grasped from the number of spots P in an array and the shape is grasped from the direction of the array.

Description

Detailed Description of the Invention The present invention radially illuminates a target object with a light spot array and recognizes the spots with the naked eye or a photodetector, thereby determining the distance to the target object and the shape and size of the target object. The present invention relates to a method for identifying distance, shape, etc. using a fiber grating to extract features such as.

For example, in conventional endoscopic diagnosis in the medical field, it has been difficult to identify three-dimensional shapes such as the distance to an affected area and undulations. Furthermore, in the general industrial field, most industrial robots to date do not have an eye function for identifying objects, so it is difficult to achieve high functionality and high reliability. Even in industrial fields other than robots, there is currently a strong demand for a means to easily identify distance, shape, and size in three dimensions.

The purpose of the present invention was to meet the above-mentioned requirements, and the fiber grating is capable of projecting diffraction spots of tens of orders with the same brightness, and the spatial coordinates can be adjusted using a large number of radial laser beams. Fiber grating is a new method that detects the coordinates of a target object and extracts features such as the shape of the target object from the arrangement of spot arrays. The purpose is to provide a method for identifying the distance, shape, etc. of optical fibers that have the same diameter.
A laser beam is projected onto one surface of a set of fiber gratings, and diffraction spots emitted radially from the other surface at equal intervals are projected onto the surface of the target object, and the target object is determined from the array and distribution state of the diffraction spots. The feature is that at least one of the distance, shape, and size of the object is identified.

The present invention will be explained in detail below based on illustrated embodiments.

First, the fiber grating used in the present invention will be explained. As shown in Figure 1, in order to split a single light beam into a number of beams with equal light intensity using a transmission type diffraction grating l configured with a conventionally used slit array, the width of the slit must be needs to be narrowed to about the wavelength of light. However, in this case, most of the incident light is blocked by the shading band, and the diffraction efficiency is extremely low.Also, when the width of the slit is widened, the light is concentrated on the 0th diffraction order,
The intensity of each order tends to decrease rapidly as the order increases from the first order to the second order.

Therefore, in recent years, consideration has been given to using a phase grating to obtain high diffraction efficiency, or to using a holographic method to make the intensity of each order uniform.

However, these methods use a chemical etching process to form many rectangular or triangular grooves of various sizes on the glass surface, but it requires a sophisticated process to create fine patterns with high precision. It requires technology and is expensive.

The fiber grating 2 is as shown in Figure 2.
It is a single fiber array in which a large number of optical fibers 3 having the same outer diameter are arranged without gaps. When a plane wave of a single wavelength, for example, a laser beam L, is incident on one surface of the fiber grating 2, each optical fiber 3 acts as a spherical lens, and the laser beam L is focused onto a point F very close to each optical fiber 3. After that, it is transmitted as a spherical wave L' at a wide angle. That is, each focal point F acts as seven rays of a point light source that radiates spherical waves L' of mutually different phases with substantially the same intensity over a wide area. This interference of the individual spherical waves L' forms an array of diffraction spots of equal intensity. Input the wavelength of light, d the lattice constant, and m the diffraction order.
Then, the diffraction angle θ at this time is.

θ=sin’ (mλ/d) It is the same as the conventional diffraction grating l.

Since the diffraction shown in Figure 2 is Fraunhofer diffraction,
A sufficient distance is required to obtain a Fourier transform image. Therefore, in order to obtain a diffraction spot array as an ideal Fourier transform image over a short distance, a collimator lens 4 with a focal length f and a positive power that focuses on a point F is used as shown in Fig. 3. do it. That is, if the focal point F of the fiber grating 2 is placed to coincide with the front focal plane of the collimator lens 4, the collimator lens 4
An array of diffraction spots of uniform brightness is obtained at the back focal plane. When the point light source array behind the fiber grating 2 is expressed by the comb function comb(x/d), the diffraction image observed as this spot array is expressed by the comb function comb(dξ/input f) as its Fourier transform. where the spacing of the spot array is in/d.

The diffraction image obtained with one fiber grating 2 is a one-dimensional array, but as shown in FIG. 5 and irradiate it with the laser beam L.

A two-dimensional spot array A is obtained. Note that the two-dimensional spot array A that does not use the collimator lens 4 is not formed on a flat surface but on a spherical surface as shown in FIG.

FIG. 6 shows an embodiment of the method according to the invention, in which collimated light from a laser light source 6 is directed onto a spot array projection section 5 consisting of orthogonally arranged fiber gratings 2a, 2b. When irradiated, the spot array projection section 5 emits a large number of light beams Lb of uniform intensity over a wide area.

Each beam Lb has a respective diffraction order m.

The order m of each beam Lb can be found by a method described later. This means that a large number of radial beams L
This corresponds to drawing spatial coordinates by b, and when the target object 7 is located in this space, one to several small diffraction spots P are projected onto the surface of the target object 7 at a long distance among the spot array A. At close range, many diffraction spots P
will be projected.

If the distribution of the projected diffraction spot P is observed with the naked eye,
The direction and shape of the target object 7 can be roughly recognized, and if the photodetector 8 is used, the direction of the target object 7 can be determined from the order m of the diffraction spora) P, and the number of diffraction spora) P can be counted. The distance can be determined by the method described later, and the coordinates of the target object 7 can be determined. Furthermore, the length in that direction can be detected from the number of diffractive sporae P arranged in a row, and if the optical axes of the spot array projection unit 5 and the photodetector 8 are tilted, the target object 7 can be detected. It is possible to identify the three-dimensional shape of For example, if the target object 7 is a cube, the shape of the pattern observed by the photodetector 8 can be determined because the direction in which the diffraction spots P are arranged differs for each face of the cube.

In the embodiment shown in FIG. 7, a lens 9 and an optical fiber 10 are interposed between the laser light source 6 and the spot array projection unit 5, and the laser beam L is passed through the optical fiber 10 to the spora I.
...A lens 11 and a fiber scope 12 are used to guide light to the array projection section 5 and to guide a diffraction image to the photodetector 8.

This embodiment can be effectively used to identify three-dimensional shapes inside organs that are difficult to directly observe, such as with medical endoscopes. That is, optical fiber IO or fiber scope 1
2. The miniaturized optical system is housed in a freely bendable tube with a diameter of about 1 cm, and can be inserted into complex organs such as the esophagus and stomach.

FIGS. 8(a) to 8(c) are explanatory diagrams when features of the shape of the target object 7 are extracted and recognized by simple arithmetic processing in the detection unit. That is, when the spot array projection unit 5 and the photodetector 8 are gradually brought closer to the target object 7, the diffraction spora l-P is initially projected as shown in (a), but as it approaches, As shown in (b), the number of diffraction spots P projected onto the target object 7 increases. At this time, it is easy to select only the newly generated spoiler) P by the arithmetic circuit built into the photodetector 8. Since this new array of diffraction spots p corresponds to the outline of the target object 7 as shown in (C), the number of these outlines is
Depending on the way they intersect, the shape of the target object 7 can be recognized as a cube, a regular tetrahedron, etc.

Note that stereoscopic recognition in the calculation unit can be performed in the following order.

(1) Determination of line segment equation A straight line is applied to the set of green pixels, and the line segment that best matches is determined as the contour equation.

(2) Determination of intersection coordinates Find the intersection point using the line segment equation and obtain the coordinates of the intersection point.

(3) Determination of surface elements Find the surface elements that constitute the target solid from the line segment equation and the intersection coordinates.

(4) Classification of line elements, surface elements, and intersections The number, angle, and coordinates of line elements, surface elements, and intersections that make up the target solid are classified.

(5) Matching with reference solid features The classification table of the features of the reference solid in the storage device is compared with the above classification, and the solid with the closest features is selected.

(8) Recognition The embodiments shown in FIGS. 9 to 12 show a modulation section that labels the diffraction order m on the radial beam Lb emitted from the spot array projection section 5 in FIGS. 6 and 7. There is. In the embodiment shown in FIG. 9, a light shielding plate 15 having a handle 14 having a different natural frequency or length is arranged in each beam Lb, and the vibration of each light shielding plate 15 is changed by externally induced vibration. By amplitude modulating each beam Lb and knowing its frequency, the order m of the beam Lb can be identified.

In the embodiment shown in FIG. 10, a Fabry-Perot type resonator 16 whose natural frequency changes depending on the thickness etc. is arranged for each beam Lb, and when vibration is applied from the outside by a vibrator 17, each beam has its own natural frequency. The opposing mirror 18 of the resonator 16 vibrates, and the amplitude of each beam Lb is modulated by repeating resonance and anti-resonance.

In the embodiment shown in Fig. Ml1, each beam L is
By arranging the beams Lb for each beam Lb, each beam Lb is labeled by the polarization direction.

In the embodiment shown in FIG. 12, each beam Lb is transmitted through a conversion element 20 that converts light into different wavelengths, thereby labeling each beam Lb with different wavelengths such as f+ΔfO1f+Δf1, . . . . Such a conversion element 20
In this method, fluid is flowed in the direction of the arrow through two plates whose distance is gradually changed, or through a tube whose inner diameter is gradually changed.
The flow velocity changes depending on the location, thereby changing the Doppler shift.

In the embodiment shown in FIG. 13, in order to label each radial beam Lb with the diffraction order m in the embodiment shown in FIGS.
An optical system is used that irradiates the spot array projection section 5 with the light beam 2. The diffraction angle for each wavelength input 1 and input 2 is 01, θ2
Then, for both, θ=θ5 −02= sin−1(m in 1/d)−s
An angular difference θ of in-I (m in 210) is generated, and θ takes a different value for each diffraction order m. If this difference in angle is detected by a photodetector, 1,
The diffraction order m of each beam Lb can be identified. Moreover, if the diffraction order m of each beam Lb has already been linked by the method shown in FIGS. 9 to 12,
The distance from the spot array projection unit 5 to the target object can be identified by the interval between the diffraction spots of each wavelength irradiated onto the target object.

The embodiment shown in FIG. 14 is a combination of the embodiments shown in FIGS. 6 and 7 with one laser light source 6a, 6b, one spot Φ array projection unit 5a, 5b, and one photodetector 8a, 8b.
This is a method of identifying the position coordinates of the target object 7. That is, the target object 7 has the first . a second spot array projection section 5a;
Assuming that diffraction spots Pm and Pn with diffraction orders m and n are projected as the diffracted light by 5b,
When the wavelength is input and the distance between the first spot array projection section 5a and the second spot array projection section 5b is D, the position coordinates of the target object 7 are x = (D/2) (m (d2- n 2 people 2) L'2 + n (d2 - m2 input 2) L'2) / (m (d2 - n2 input 2) '2 - n (d2 - m2 people 2) gin1 y = (D / input) ( m (d2- n', input 2
)L'2·n(d2-m2 people2)'-)/(m(d2-n2 people2)2-n(d2-m2 people2)L'2).

As explained in detail above, the method for identifying distance, shape, etc. using the fiber grating according to the present invention involves irradiating collimated light from a laser light source onto the fiber φ grating, and then emitting a large number of light beams emitted from the fiber grating. By projecting diffraction spots of various intensities onto the target object,
The distance, coordinates, and shape of the target object are identified based on the distribution state of the projected diffraction spots, and it is extremely effective in that information about the target object can be easily recognized. In addition, since the method is simple, it can be easily miniaturized and can be applied even in a narrow area.

In particular, the present invention makes it possible to easily obtain information such as the size and three-dimensional shape of an affected area, which has been difficult until now, in endoscopic diagnosis, etc., and can also be applied to industrial applications such as the eyes of industrial robots. It can also be used very effectively as a cheap and simple method for identifying features of target objects.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a conventional diffraction grating, Figure 2 and the following diagrams show an example of the method for identifying distances, shapes, etc. using the fiber grating according to the present invention, and Figure 2 shows the fiber grating used in the present invention.・Explanatory diagram of the grating. Figure 3 is an explanatory diagram of the state in which the collimator lens is inserted between the fiber grating and the target object. Figure 4 is the spot array projection part and the target object where two fiber gratings are orthogonally crossed. Spot with collimator lens inserted between
An explanatory diagram of the projection of the array; FIG. 5 is an explanatory diagram of the projection of the spot array in a state in which the collimator lens of FIG. 4 is not used;
Figures 6 and 7 are illustrations of this measurement method, Figures 8 (a) to (c) are illustrations of three-dimensional recognition, and Figures 9 to 14 identify the order of the emitted beam, respectively. FIG. 2.2a, 2b are fiber gratings, 3 is a fiber, 4 is a collimator lens, 5 is a spot array projection unit, 6 is a laser light source, 7 is a target object, 8 is a photodetector, 1O is an optical fiber/to , 12 is a fiber scope. Patent applicant Machida Opto Giken Co., Ltd. Figure 1! [51!1 Figure 8 (0) Figure 8 (b)

Claims (1)

[Claims] 1. A laser beam is projected onto one surface of two sets of fiber gratings in which optical fibers of the same diameter are arranged closely in parallel and superimposed orthogonally to each other, and an equal beam is emitted from the other surface. A fiber that projects diffraction spots emitted radially at intervals onto the surface of a target object, and identifies at least one of the distance, shape, and size of the target object from the array distribution state of the diffraction spots. A method for identifying distance #: Φ shape, etc. using gratings. 2. Distance and shape using the fiber grating according to claim 1, in which a lens having positive power is inserted between the fiber grating and the target object, and the diffraction spot is emitted as a parallel beam. etc. identification method. 3. A method for identifying distance, shape, etc. using a fiber grating according to claim 1, wherein the laser beam projected onto the fiber grating is guided using an optical fiber. 4. Distance/shape using the fiber grating according to claim 1, wherein the array distribution state of the diffraction spots on the surface of the target object is used to identify the distance to the target object using a photodetector. etc. identification method. 5. Adjusting the distance, shape, etc. using the fiber grating according to claim 5, which guides the array distribution state of the diffraction spots on the surface of the target object to a photodetector using an optical fiber. Identification method. 6. Distance and shape using a fiber grating according to claim 5, wherein the frequency of the emitted diffraction spot is changed for each diffraction order, and the diffraction spots are identified for each diffraction order. etc. identification method. ? The distance, shape, etc. using the fiber grating according to claim 5, wherein the polarization state of the emitted diffraction spot is changed for each diffraction order, and the diffraction spot I is identified for each diffraction order. How to identify. 8. Identification of distance, shape, etc. using the fiber grating according to claim 5, wherein the wavelength of the emitted diffraction spot is changed for each diffraction order, and the diffraction spot is identified for each diffraction order. Method. 9. Distance and shape using the fiber grating according to claim 5, in which the diffraction angle is changed for each diffraction order of laser beams of two different wavelengths, and diffraction spots are identified for each diffraction order. etc. identification method. 10. Distance measurement using a fiber grating according to claim 5, which uses two sets of a fiber grating that emits the diffraction spot and a photodetector to determine the position coordinates of the diffraction spot on the surface of the target object. How to identify shapes etc.