JPS62291512A - Distance measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain an apparatus available constantly for high-accuracy measurements and 3-dimensional informations, etc. of an object in comparatively short time, by installing a mask forming a pattern light flux and an elliptical reflecting mirror etc., oriented to the mask to the mask of a beam of light from a light source. CONSTITUTION:A light flux that passed light-transmitting unit 61, 65 from a light source 3 develops light images in positions P1, P2 on an object 5 after passing through a lens 1. Next, after passing through a lens 3 respectively, it develops light images in positions D1, D2 in an image sensor 4. An output wave form of this sensor 4 is observed by an image-processing apparatus for obtaining distance up to an image position on the surface of the object 5. And, on this apparatus, the light source 3 is set part from the mask 6 and outside a light path of a light flux reflected by an elliptic reflecting mirror 7 oriented to the mask 6 of a beam of light from the light source 3. Thus, only such a light flux which came from the specified direction is admitted into a light-transmitting unit 61, 62,...65. Further, the light-source 3 is set in the first focus of the reflecting mirror 7 and the center of incident pupil of the lens 1 in rough vicinity of the second focus of the mirror 7 and thus, all light fluxes obtainable by the mask 6 is irradiated on the object 5.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a distance measuring device, and in particular, it is capable of measuring the distance to an arbitrary position of an object using an active method, and is also applicable to measuring the three-dimensional shape of an object. This invention relates to a distance measuring device.

[Prior art]

BACKGROUND ART Conventionally, light cutting methods (slit methods), stereo methods, and the like have been known as methods for acquiring distance information and information regarding three-dimensional shapes using image sensors and the like.

In the optical sectioning method, a slit light is projected onto the surface of an object, and the projection line on the object surface is observed from a direction different from the projection direction to obtain information such as the cross-sectional shape and distance of the object. In this method, the imaging side is fixed, and three-dimensional information is acquired by capturing a plurality of images for each slit while changing the slit projection direction little by little.

In addition, in the stereo method proposed by the applicant in Japanese Patent Application No. 59-44920, a two-dimensional image pickup device combined with an optical system with equal image magnification is placed apart by a predetermined baseline length, and two-dimensional images viewed from different directions are arranged. Obtain a dimensional image, and calculate the height of each position of the object based on the deviation of the two image information (the distance to the imaging system)
is calculated.

However, in the optical cutting method, there is a problem that controlling the slit projection direction during imaging is troublesome, and imaging takes time. Also,
Since three-dimensional information is obtained from a plurality of slit images, there is a large amount of information to be processed, and the disadvantage is that it takes a long time to finally obtain the information.

In addition, although the stereo method does not require controls such as slit scanning, conventional methods are generally passive methods, so if the object surface is smooth and has uniform brightness,
The contrast of images obtained with two image sensors decreases, and two
Distance by comparing two images.

There is a problem that distance measurement becomes impossible. Cases in which such measurements become impossible occur frequently at short distances where the image magnification increases, and therefore have the disadvantage that the shape, color, size, distance, etc. of the object are limited. was.

[Summary of the invention]

In view of the above-mentioned conventional problems, it is an object of the present invention to be able to always measure accurately regardless of the type of object, and to obtain distance to any position of the object and three-dimensional information of the object in a relatively short time. The object of the present invention is to provide a distance measuring device capable of obtaining the following.

A further object of the present invention is to provide a distance measuring device that satisfies the above objects and has a wide distance measuring range.

In order to achieve the above object, a distance measuring device according to the present invention includes a plurality of optical systems arranged with optical axes parallel to each other and spaced apart by a baseline distance, and a plurality of patterned light fluxes through one of the optical systems. A light source means for irradiating the object, and an image sensor that receives an image of the pattern light beam on the object through a different optical system, and a light image of the pattern light beam on the object detected by the image sensor. A device for measuring the distance from a position to a predetermined position of an object, wherein the light source means includes a light source and a mask that receives light from the light source to form a patterned light beam, and directs the light from the light source to the mask. It has an elliptical reflecting mirror, and is characterized in that the light source is arranged outside the optical path of the light beam directed toward the mask.

Further features of the present invention are described in the Examples shown below.

〔Example〕

FIG. 1 is a schematic diagram of an optical system showing an embodiment of a distance measuring device according to the present invention. In the figure, lenses 1 and 2 are arranged with a baseline distance apart, their optical axes are parallel to each other, and the object-side principal planes of each lens 1 and 2 lie on the same plane. Further, in this embodiment, lenses 1 and 2 are used that have the same focal length. Reference numeral 3 denotes a light source, which preferably has a relatively small light emitting portion 3'. Reference numeral 4 denotes an image sensor composed of a CCD or the like, 5 an object for distance measurement, and 6 a mask for pattern projection, which includes a light-shielding member and a plurality of light-transmitting parts 61, 62 . ...
An open rotor pattern consisting of 65 is provided and is located near the focal point of the lens 1. Also, 7 is an elliptical reflector and light source 3
reflects some of the light from the Figure 2 shows the opening of the mask 6.
．． A plurality of thin rectangular slit-shaped light transmitting parts 61, 62, 63, . . . are arranged on the upper mask 6. As shown in FIG. In the figure, transparent parts 61, 62. . . . have a sparse arrangement in the horizontal direction and a comparatively dense arrangement in the vertical direction, as shown by the thin line AX at their lateral centers, and as a result form slit rows extending in the diagonal direction. Translucent part 6
1,62. The density and arrangement of ... can be determined according to the required measurement accuracy and the vertical and horizontal resolution of the image sensor used, so it is not limited to the above configuration (various patterns can be used). The reason why the density in the horizontal direction of the transparent parts 61, 62, etc. of the mask 6 is made relatively low as shown in FIG. This is because the position of the optical image moves in the horizontal direction, so the distance range in which detection can be performed is widened.

In the configurations shown in FIGS. 1 and 2, the light beams illuminated by the light source 3 and passed through the transparent parts 6+ and 6s pass through the lens l, and depending on the position of the object 5, the light beams PI and PI on the object 5, respectively. P
Focus the optical image at the position shown in 2. And P.I.

The light images on P2 each pass through the lens 2 and reach the image sensor 4.
A light image is focused on the upper positions DI and D2.

As can be seen from the principle of the stereo method, the position of the optical image Dn (n=1°2...) depends on the distance of the reflection point, that is, the distance between the positions PI and P2 of the object 5, and the direction in which the lens 1.2 is arranged. It will move on a straight line parallel to (baseline direction).

Therefore, it is possible to detect the distance distribution of the surface of the object 5 from the measuring device as a horizontal density distribution of the optical image Dn (n=1.2...). That is, by observing the output waveform of the image sensor 4 with an image processing device using a computer system or the like, the distance to the light image position (light beam projection point) on the surface of the object 5 can be easily determined based on the principle of triangulation. be able to.

Now, in this embodiment, in order to expand the measurable distance range, not only the depth of field of the lens 1.2 is increased, but also the pattern light beam irradiated onto the object 5 is devised. . That is, in FIG. 1, the transparent parts 61, 62,
63, 64, and 65 can be regarded as point light sources, and when illuminating the open pattern of the mask 6 using a normal illumination method, the light emitted from the respective transparent parts 61, 62...65 is diffused and the lens The light passes through the entire pupil of L and is directed to the object 5 via the lens 1. When the object 5 is irradiated with a patterned light beam in this way, there is a limit to the distance measurement range that can be obtained even if a lens l with a large depth of field is used, and an open pattern on the image sensor 4 is used. A blurred optical image is formed, making it difficult to detect the optical image position.

However, in this embodiment, the light source 3 is placed at a position away from the mask 6 and outside the optical path of the light beam reflected by the elliptical reflector 7 for directing the light from the light source 3 toward the mask 6. The light-transmitting portion 6+ of the mask 6 is defined as follows.

62, . . . , 65 so that only light beams coming from a predetermined direction are incident thereon. Furthermore, in this embodiment, the light source 3 (small light emitting section 3') is arranged at the first focal point of the elliptical reflecting mirror 7, and the second focal point of the elliptical reflecting mirror 7 is arranged so as to substantially coincide with the center of the entrance pupil of the lens 1. By doing so, all of the plurality of patterned light beams obtained by the mask 6 are irradiated onto the object 5 through the lens 1.

Furthermore, in the lighting method using an elliptical reflector used in conventional projectors, etc., a method is adopted in which both direct light and reflected light from the light source illuminate the mask, thereby increasing the amount of light hitting the mask surface. There is. In this case, there is a difference in the direction in which the reflected light and the direct light enter the mask. Therefore, when the object 5 is located at a position shifted from the focal point position like P2, there will be a difference in the position at which the reflected light and the direct light illuminate the object, and two points will be illuminated, resulting in an image This also causes a difference in the position of the light image received by the sensor 4, which is a hindrance to detecting the position of the light image and measuring the object distance. In addition, there are cases where the reflected light passes through the glass tube that seals the light source and illuminates the mask 6, and the spread (NA) of the light beam illuminating the open pattern of the mask on the object 5 increases, making it difficult to focus. As described above, the amount of blur of the open pattern of the mask 6 irradiated onto an object located at a distance from the object is increased.

On the other hand, in the arrangement shown in FIG. 1 according to the invention, the light emitted from the light source 3 and directly illuminating the mask 6 does not enter the lens l. Therefore, the light beam that irradiates the object with the open pattern of the mask 6 comes out from the light source 3 and is reflected by the elliptical reflector 7.
Only the light that passes through the peak of the entrance pupil of No. 1, 1 cm x 4 lbs., and the spread of the light flux that passes through one point of the light-transmitting part 61, 62 of the mask 6, is seen from this point. The viewing angle is the size of the minute light emitting part 3' of the light source 3 reflected on the reflecting mirror, and the light that passes through one point of the transparent part 53 as shown in the figure is a luminous flux with a small spread angle as shown by the solid line. Become. The size of the blur at the position P2 away from this united focal point position is d
′ and can be made smaller. Furthermore, due to the properties of the elliptical reflector described above, the light that passes through the transparent window 55 at the edge of the mask 6 also goes toward the center of the entrance pupil of the lens 1, so that vignetting by the lens 1 does not occur (the aperture of the lens is made small). Furthermore, it becomes possible to remove the holding member and glass sealing body of the light source 3 from the optical path of the light beam reflected by the elliptical reflector 7 and incident on the lens 1, so that the amount of light transmitted through the transparent window of the mask 6 can be reduced. It is possible to reduce unevenness.

Figure 3 shows a two-dimensional CC for a TV camera as the image sensor 4.
One scanning line when using the D sensor (thin line A in Figure 2)
This figure shows the output waveform O (corresponding to X). Here, the horizontal direction of the figure corresponds to the horizontal distance of the image sensor 4. As is clear from the above, the transparent portion 6n of the mask plate 6 (n=1.2.
), the output value shows the local maximum value M. The left and right positions of the maximum value of the output waveform that appears corresponding to one transparent part 6n (n=1.2...) are limited, and the range in which the maximum value appears due to other transparent parts is limited. Since the light transmitting portion 6n (n=1.2, . . . ) is separated from the light transmitting portion 6n (n=1.2, . . . ), the incident position of the light beam passing therethrough onto the image sensor 4 can be easily correlated.

Therefore, the distance to an arbitrary position of the object 5 and three-dimensional information can be reliably acquired without causing problems such as inability to measure due to a decrease in contrast at short distances as in the conventional stereo method. Furthermore, unlike the conventional stereo system, an active system is adopted in which illumination is performed using a light source, which has the advantage that the amount of light from the light source can be small when measuring objects at short distances. Furthermore, it is also possible to estimate the inclination angle of the optical image position of the object from the magnitude of the maximum value of the image sensor output.

As described above, the distance of the surface of the object 5 from the measurement system can be measured via the two-dimensional image sensor 4.

According to the above configuration, three-dimensional information on the entire surface of the object 5 can be extracted by one image reading without the need for mechanical scanning as in the optical cutting method.

In addition, since subsequent image processing only needs to be performed on the distribution of the light image in the left and right direction, simple and luminous processing is possible.

Further, according to this embodiment, the image of the structure on the image sensor 4 can be directly binarized and output to a CRT display or a hard copy device to provide a visual three-dimensional representation.

The distance measurement method or three-dimensional information processing power method according to this embodiment is an optical non-contact method in which a large number of styli are pressed against an object and the shape of the object is perceived by changes in the amount of protrusion of the stylus from a reference surface. Since it is possible to perform high-speed and accurate processing, it can be used as a visual sensor for robots and other devices that require real-time processing. This is particularly effective when perceiving the shape, posture, etc. of an object placed at a relatively close distance, and causing actions such as grasping and avoiding the object.

In addition, in the above explanation, for the sake of simplicity, only the main parts of the device are illustrated, and illustrations of the signal processing system, the housing for the connections, etc. are omitted, but these parts can be explained by those skilled in the art as necessary. An appropriate one may be provided in the conventional manner. Further, although only a single lens is shown as an optical system, an optical system including a plurality of elements, a mirror, etc. can also be used.

Further, in each of the above embodiments, a configuration is shown in which two optical systems having the same focal length are used, but it is also possible to use three or more optical systems having different focal lengths, if necessary. However, it is easiest to use the same optical system with the same focal length and with the same aberrations.

Furthermore, in the embodiments described above, a method was shown in which measurement was performed by detecting an optical image of an open pattern having a plurality of transparent parts arranged two-dimensionally with a two-dimensional image sensor such as a CCD. For example, an open pattern in which a plurality of transparent parts are arranged one-dimensionally at predetermined intervals is set to an orange D+1. It is also possible to detect the shape of the object along a specific direction by receiving the image of the robot pattern 4'11 with an image sensor having sensor rows in 1,000 directions.

In addition, the second optical system that receives the pattern light beam from the object is
It is also possible to widen the field of view for distance measurement by using two or more optical systems, and it is also possible to widen the field of view for distance measurement by moving the second optical system in parallel using a predetermined drive device.

Alternatively, the same function can be obtained by moving the first optical system that irradiates the object with a plurality of patterned light beams and the light source means in parallel using a predetermined drive device.

According to the present invention, it is preferable that the pattern light beam irradiated onto the object be a narrow light beam with a spread angle as small as possible, but since its limit depends mainly on the sensitivity of the image sensor, the sensitivity of the available sensor It is decided in conjunction with the light source output, required measurement accuracy, and specifications.

In addition, the magnification and baseline length of the optical system, that is, the distance between the first optical system and the second optical system in Figure 1, the pitch of the light-transmitting part of the mask, etc., determine the distance measurement range to be measured. You should take this into consideration when deciding.

Further, the image sensor referred to in the present invention includes all photoelectric conversion elements such as photodiodes and CODs, and there is no limitation to the arrangement state such as a one-dimensional array or a two-dimensional array.

Further, as shown in FIG. 1, the elliptical mirror used in the present invention may be constructed from a part of the elliptical mirror, or may be constructed by arranging the entire elliptical mirror as it is. By locating the first optical system, preferably its entrance pupil, near the second focal point of the mask, it is possible to obtain a narrow light beam that is less affected by aberrations.In other words, most of the light flux emitted from the mask It is preferable to configure it so that it passes near the front axis of the first optical system.

〔Effect of the invention〕

As described above, the distance measuring device according to the present invention achieves short-time and highly accurate distance measurement regardless of the type or position of the object by adopting an active method, and also uses a mask, a small light emitting source, a mirror, etc. A wide measurement range is provided by making the pattern light beam diameter irradiated onto the object a narrow light beam.

Further, according to the present invention, it is possible to acquire three-dimensional information from an object in a short time and with high precision, making the device suitable as a visual sensor for robots and the like.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical system showing an embodiment of a distance measuring device according to the present invention. FIG. 2 is a diagram showing an example of an open pattern of a mask. FIG. 3 is a diagram showing the output waveform of one scanning line when a CDD is used as an image sensor. 1.2... Len Y, 3... E light source device, 3 s, 32.・, 3n...small light emitting source, 4...
... Disgusting sensor, 5... E object, 6... E mask, 61.62.・, 6n... Translucent part, 7... Circular reflecting mirror.

Claims (2)

[Claims] (1) A plurality of optical systems arranged with their optical axes in parallel and separated by a baseline distance, and a light source means for irradiating the object with a plurality of patterned light beams through one of the optical systems; an image sensor that receives an image of the patterned light beam through an optical system different from the above, and a distance from a position of the light image of the patterned light beam on the object detected by the image sensor to a predetermined position of the object; The light source means includes a light source, a mask that receives light from the light source to form a patterned light beam, and an elliptical reflector that directs the light from the light source toward the mask, and the light source is directed toward the mask. A distance measuring device characterized in that it is arranged outside the optical path of a light beam. (2) The distance measuring device according to claim 1, wherein a light source and one of the optical systems are arranged at two focal positions of the elliptical reflecting mirror, respectively.