JP2011163988A - Pattern light projection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple device capable of projecting pattern light with high definition which is used for the three-dimensional measurement of a human head or the like by a pattern projection method. <P>SOLUTION: The device is simply constituted by using a flash as a light source, and narrows a blurring width in a direction perpendicular to a projected image pattern by disposing wide and narrow slit-like diaphragms in a direction parallel with and a direction perpendicular to a linear pattern to be projected, respectively, thereby obtaining the high-definition pattern light. Also, the bright pattern light is obtained by using a light pipe, thus enabling the high-accuracy three-dimensional measurement. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pattern light projection apparatus used when a subject such as a still life, a human head, an upper body, or a whole body is measured three-dimensionally using a pattern projection method.

  As a 3D measurement system for converting the shape of an object into 3D data, the subject is photographed with a camera from a different angle from the projection source while projecting laser slit light or pattern light onto the subject, and the principle of triangulation A method using a method such as a light cutting method or a pattern projection method is known. In these systems, in general, a dedicated pattern light projection device for projecting pattern light, such as a laser and a projector, is required in addition to the camera. However, as in the invention described in Japanese Patent Application Laid-Open No. 2002-250613, a detachable attachment that uses a built-in flash of a camera as a light source and includes a pattern mask and a projection lens before the built-in flash of a commercially available compact camera Proposals have also been made for easily projecting pattern light simply by wearing the.

JP 2002-250613 A

  In the invention of Patent Document 1, the flash light emitted from the built-in flash of the camera is guided to the pattern mask on which a linear stripe pattern is drawn, and after passing through the pattern mask, the stripe pattern is formed on the subject using the projection lens. The pattern is imaged. In this state, the three-dimensional shape of the subject can be obtained by analyzing the distortion caused by the parallax between the projection lens and the camera of the pattern projected on the subject on the obtained image.

  This conventional example is effective when a subject with a small degree of unevenness placed at a short distance is converted into three-dimensional data at a low resolution. However, for the following reason, the subject is three-dimensionally measured. In addition, when including from the tip of the nose to the ear, there is a difference in depth of 10 Cm, and it is difficult to apply when a highly accurate measurement is required to some extent.

  The first problem is that the pattern light projected on the subject becomes very dark if the parallax is large enough to enable highly accurate three-dimensional measurement of a subject that is several tens of cm away from the camera. In order to measure the face of a person who is several tens of cm away with a precision sufficient to recognize the eyes and nose, the parallax between the camera and the pattern light irradiation source must be at least 10 to 20 Cm. The more accurate the three-dimensional measurement becomes possible. In the above conventional example, an example in which the parallax is increased is described, but the specific structure is not described. Assuming that the parallax is increased by using two reflectors like a periscope, the distance between the built-in flash as the light source and the projection lens increases, so it is inversely proportional to the square of the distance. As a result, the amount of light reaching the projection lens decreases, and a bright image cannot be obtained.

  FIG. 12 is an optical path diagram schematically illustrating how light travels in the conventional pattern light projector. Actually, the optical axis should be bent twice like a periscope, but here we will focus only on the spread due to the distance of the flash light, so the bent part is omitted and it is schematically shown as a straight optical path. Painted. In the figure, 3 is a flash, 12 is a pattern mask, 13 is a projection lens, and 4 is flash light emitted from the flash 3. The flash light is radiated radially from the flash 3 at a wide angle, but only the upper half of the light beam is shown in the drawing in order to avoid the complexity of FIG. Of the light rays shown in FIG. 12, the effective part contributing to the brightness of the image on the subject is drawn by a solid line, and the invalid part not contributing is drawn by a broken line.

  Effective light rays are only light rays that have passed through the pattern mask 12 and have reached the effective range of the projection lens 13. From FIG. 12, it can be seen that if the distance between the flash 3 and the projection lens 13 is increased in order to increase the parallax, the proportion of effective light rays becomes very small.

  The second problem is that using a lens with a large aperture as shown in the figure of the patent document of the conventional example in order to improve the brightness of the image, the depth of focus becomes very shallow, so that it looks like a human face. It is impossible to form a sharp image on the entire surface of a large uneven surface.

  FIG. 4 is an optical path diagram schematically showing how the flash light travels in the conventional pattern light projector. In the figure, 20 is the surface of the subject, 21 is the focal plane of the imaging optical system, 12P and 12Q are points on the pattern drawn on the pattern mask 12, and 12P1 and 12Q1 are points 12P and 12Q, respectively. It is an image projected on the subject 20 by the optical system.

  In the imaging optical system, in order to obtain a sharp image, the light emitted from one point on the pattern mask must be focused on one point. However, when the lens diameter is large and the unevenness of the subject is large. Even if the position of the subject is adjusted so that the focal plane 21 is near the center of the unevenness of the subject 20, the positions where the images 12P1 and 12Q1 can be largely deviated back and forth from the focal plane 21, so that only a blurred image can be obtained. I can't. The diameter of the blur caused by this depth of focus can be obtained geometrically from the figure.

  In the case of measuring a human face three-dimensionally, the distance between the camera and the subject is preferably about 50 Cm to 100 Cm. For example, the effective diameter of the projection lens 13 is 20 mm as shown in the figure described in Patent Document 1. Assuming that the distance from the lens to the focal plane 21 is 50 Cm and the subject's front / rear deviation from the focal plane is plus or minus 5 Cm, the front / rear deviation is 10% of the distance to the focal plane, so it is farthest from the focal plane. At the position, the diameter of the blur caused by this depth of focus is also 10% of the projection lens diameter, that is, 2 mm. If the diameter of the blur is 2 mm, pattern light with a pitch finer than the interval of 2 mm cannot be projected on the subject, so that highly accurate three-dimensional measurement cannot be performed.

  The present invention is to solve the above-described problems, and includes means for receiving flash light emitted from a camera built-in or external flash, and linear striped pattern light extending in a direction perpendicular to the parallax direction. The main feature is that it includes a projection means and an imaging optical means having a light path that is wide in the direction parallel to the stripe pattern of the pattern light and narrow in the vertical direction.

  The pattern light projection apparatus of the present invention can project a bright and fine pattern onto an object with large irregularities by a simple operation that is only required to be attached to an external flash or a built-in flash of a compact camera. There is an advantage that dimension measurement becomes possible.

FIG. 1 is a partial cross-sectional top view showing a pattern light projector. Example 1 FIG. 2 is a schematic diagram showing a pattern mask pattern of the pattern light projector. Example 1 FIG. 3 is an optical path diagram showing how light travels in the pattern light projector. Example 1 FIG. 4 is an optical path diagram showing how light travels in a conventional pattern light projector. (Conventional example) FIG. 5 is an optical path diagram showing how light travels in the pattern light projector. Example 1 FIG. 6 is a top view showing a first photographing scene using the pattern light projector. Example 1 FIG. 7 is an image photographed using the pattern light projector. Example 1 FIG. 8 is a top view showing a second shooting scene using the pattern light projector. Example 1 FIG. 9 is a top view showing a third shooting scene using the pattern light projector. Example 1 FIG. 10 is a partial cross-sectional top view showing the pattern light projector. (Example 2) FIG. 11 is a front view showing the pattern light projector. (Example 2) FIG. 12 is an optical path diagram schematically illustrating how light travels in a conventional pattern light projector. (Conventional example) FIG. 13 is an optical path diagram schematically illustrating how light travels in the pattern light projector. (Example 2)

  We realized a pattern light projection device that can project bright and fine pattern light onto a subject with a simple structure and large irregularities.

  FIG. 1 is a partial cross-sectional top view showing Example 1 of the present invention. In the figure, 2 is a camera, 3 is a tall flash attached to an accessory shoe of the camera, 8 is a lens barrel of a pattern light projection device, 16 is a flash light inlet with a highly reflective inner wall, and 12 is a flash. A film-like pattern mask installed at the rear stage of the light entrance 16 and can be exchanged depending on the subject. 13 is a projection lens, 14 is provided in front of the projection lens 13, and is a diaphragm having a narrow slit in the vertical direction in the figure and a wide slit in a direction perpendicular to the drawing sheet, 15 is a calibration plate, and 4 is a pattern. The optical axis 5 of the light is the optical axis of the camera 2, and the distance between the roots of the two optical axes is the parallax from which the calculation of the three-dimensional measurement is based.

  FIG. 2 is a schematic diagram showing a pattern when the pattern mask of Example 1 of the present invention is viewed from the direction of the optical axis 4 of the pattern light. The pattern mask 12 is made of a transparent film, and is colored with different colors so that the area 12b without hatching and the area 12c shown with hatching can be distinguished. Reference numeral 12a denotes a plurality of lines drawn on the pattern mask and extending in a direction perpendicular to the parallax direction. Reference numeral 12M denotes a reference line serving as a reference for the position of the projected pattern light. . 12P is the line 12a farthest from the optical axis of the camera, and 12Q is the closest to the optical axis of the camera. In FIG. 2, the lines are schematically drawn with a rough pitch for easy understanding of the configuration, but in practice they are drawn with a finer pitch.

  FIG. 3 is an optical path diagram showing how the light travels from when the light beam projected on the line 12P is emitted from the flash 3 and enters the projection lens 13. As shown in FIG. Light rays effective for forming an image of the line 12P are only light rays in the range shown by hatching in the drawing, which pass through the line 12P, pass through the opening of the stop 14 after being refracted by the projection lens. Therefore, it can be seen that the direct light directly irradiated onto the line 12P from the flash 3 is not effective, and only the light reflected once by the inner surface of the flash light entrance 16 is effective. Since the inner surface of the flash light entrance 16 is made highly reflective, the flash light is efficiently reflected and the line 12P is illuminated brightly.

  FIG. 5 is an optical path diagram showing how light travels in the pattern light projection apparatus according to the first embodiment of the present invention, and the vertical direction in the figure is the parallax direction. Since the light that has passed through the pattern mask 12 is narrowed down to a thin beam by the diaphragm 14 having a narrow slit in the parallax direction, the depth of focus in the parallax direction becomes deep, and even if the surface of the subject 20 deviates greatly from the focal plane back and forth. The images 12P1 and 12Q1 of the image lines 12P and 12Q are not so blurred, and an extremely sharp image is obtained.

  As in the case of the conventional example, assuming that the distance from the projection lens to the focal plane 21 is 50 Cm, the subject's back-and-forth deviation from the focal plane is plus or minus 5 Cm, and the slit width is 2 mm, the blur width due to the focal depth is The slit width is 10%, that is, 0.2 mm.

  The narrower the slit width of the stop 14 is, the narrower the blur width due to the depth of focus is. However, if the slit width is made too narrow, the narrower this time, the greater the blur due to diffraction. When the blur width due to diffraction is calculated with the above parameters, the blur width due to diffraction is about 0.2 mm when the distance from the projection lens to the focal plane 21 is about 1 mm as in the case of blur due to the depth of focus. It becomes about 4 mm. Also, narrowing the slit width directly leads to darkening the image on the subject, so it is not preferable to make the slit too narrow from this point of view.

Therefore, when these are taken into consideration, when the distance of the subject is about 50 to 100 Cm, as in the case of measuring a human head, it is well balanced that the slit width is about 2 to 3 mm. If the slits are used, it is possible to project fine pattern light of about 1 mm pitch on the subject and about 0.5 mm pitch if the optical system is designed more carefully. If this level of resolution can be realized, it is sufficient for three-dimensional measurement that can grasp the characteristics of a human face. When the slit width is smaller than 1 mm or larger than 4 mm, the blur due to diffraction and the blur due to the depth of focus respectively increase, so that it is impossible to project fine pattern light, which is suitable for three-dimensional measurement of a human face. Absent.

  The pattern light projected onto the subject has never been brighter. The width of the slit in the parallax direction needs to be 4 mm or less for the above reasons, but when projecting a linear striped pattern extending in the vertical direction with respect to the parallax, no matter how much the vertical direction of the parallax is blurred, there is no harm. Therefore, in order to brighten the image, it is better to use a projection lens having a large aperture and a diaphragm having a wide slit in the direction perpendicular to the parallax.

  FIG. 6 is a top view showing an example of a first photographing scene using the pattern light projector according to this embodiment. The camera is used sideways and the face of the subject person 20 is photographed at an angle as if looking up from the lower right.

  FIG. 7 is an image taken in the state of FIG. 20P is an image of a subject on which vertical stripe pattern light is projected, and 20MP is a projection of a reference mark 12M. A line 12a that is a straight line on the pattern mask is distorted by the unevenness and parallax of the subject. By analyzing the distortion with reference to the image 20MP of the reference mark, the three-dimensional shape of the subject can be obtained.

  FIG. 8 is a top view showing an example of a second shooting scene using the pattern light projector. In the figure, 30 is a mirror fixed to a vertical wall, and 20R is a virtual image of the subject 20 reflected in the mirror 30. The pattern light and the optical axis of the camera are in the middle of the subject 20 and the virtual image 20R of the subject 20, and the flash light that is reflected directly on the mirror and the left half of the subject's face mainly reflected by the camera line of sight. The camera's line of sight measures mainly the right half of the subject's face. At this time, on the subject, the pattern light passing through the optical path directly projected and the pattern light passing through the optical path reflected by the mirror are projected and overlapped, but the region 12b corresponding to each pattern light on the pattern mask and Since 12c is colored with different colors, the pattern light projected through the respective optical paths can be distinguished by color at the time of image analysis.

  FIG. 9 is a top view showing a third photographing scene of the pattern light projector. In the figure, 15 is a calibration plate attached to the pattern light projection device so that the circular surface faces the front, 30 is a mirror, and the photographer takes a picture of himself / herself using the mirror. The angle of view of the camera is adjusted so that a calibration plate is captured in addition to the subject. Since the shape of the calibration plate is already known, if the calibration plate is shown at the same time as the subject in the image obtained in this shooting scene, the camera parameters such as the camera angle and distance from the subject are calculated from the shape, and image analysis is performed. It can be used as basic data.

  Shooting with illumination light other than the flash at short time intervals, shooting with the flash fired, and performing an operation to find the difference between the two images will detect the projected pattern more clearly I can do it.

  In the above embodiment, the imaging optical means having a long optical path in a direction parallel to the linear stripe pattern and a narrow optical path in the vertical direction is formed by providing a circular convex lens and an elongated slit-shaped stop. The same effect can be obtained by using a shaped lens, a long and thin Fresnel lens, a long and narrow concave reflecting mirror, and the like.

  In the above embodiment, the two areas of the pattern mask are colored with different colors in order to distinguish the flash light corresponding to the two optical paths. However, when using a plurality of mirrors, the number of optical paths to be distinguished is large. Sometimes, in order to distinguish the flash light corresponding to each optical path, the corresponding pattern mask regions may be color-coded with different colors.

  In the above embodiment, the two regions 12b and 12c are colored with different colors so that the two regions 12b and 12c can be distinguished. However, the grounds of 12b and 12c are both transparent, and the line 12a is distinguished with a color that can be distinguished for each region. It may be colored. Further, the line 12a and the ground color need not be aligned with each other even within a single region, and various colors may be mixed and used so that each line can be distinguished.

  In the above embodiment, the reference mark is formed by cutting out the line 12a. However, the reference mark can be distinguished from other lines by changing the thickness, color, interval, length, etc. of the line or the place where the line is not drawn. You may do it.

  Moreover, in the said Example, although the pattern mask was comprised with the film, you may comprise the line 12a by tensioning a thread | yarn without using a film.

  FIG. 10 is a partial cross-sectional top view of a pattern light projection apparatus showing Embodiment 2 of the present invention, and FIG. 11 is a front view thereof. In the figure, 2 is a compact camera, 3 is a built-in flash built in the compact camera 2, 4 is an optical axis of flash light emitted from the flash, 11 is a light pipe made of a transparent material and having a smooth surface, 11a Is a flash light entrance of the light pipe 11 disposed so as to face the built-in flash, 11b is a light collecting means, and an optical axis bending portion having a reflecting surface having a parabolic cross section, and 11c is a second light. The axial bent portion 11d is a flash light emission port, and the other portions are the same as in the first embodiment.

  Since some flash light leaks from the vicinity of the flash light entrance and other places, the cover and pattern light projection device for preventing the leaked flash light from being emitted in front of the camera in a certain position. A bracket or the like for fixing so as to be in a relationship is necessary, but it is not an essential part and is omitted in the drawing.

  The built-in flash of a compact camera has a structure in which a diffuser plate with fine irregularities is put on an elongated arc tube whose longitudinal direction is directed to the left and right direction of the camera body, but the width of the diffuser plate is several mm. There are many narrow items as follows. Therefore, even if the effect of the diffusing plate is ignored and it is considered that light is emitted radially in the radial direction of the arc tube, it seems that there is not much difference in the light pipe focusing effect. Assuming this, the flash light is collimated by the optical axis bent portion 11b and close to parallel light if the arc tube is arranged so that the central axis thereof is at the focal point of the parabolic reflecting surface of the optical axis bent portion 11b. Thus, it is guided in the direction of expanding the parallax on the right side of the figure. Parallel light is an effect that can be realized only by light emitted accurately in the radial direction of the arc tube. However, even if the direction of light is slightly scattered by the diffuser, most of the light is too large from the optical axis. It proceeds in the direction of expanding the parallax without having an angle difference. Even when the light enters the side surface of the light pipe, it is incident at a shallow angle, so that the light pipe is efficiently totally reflected toward the inside of the light pipe. For this reason, the rate of leakage outside the light pipe is reduced.

  In the optical axis bending portion 11b, the side surface in the longitudinal direction of the flash arc tube is also a parabolic reflecting surface, and the flash light emitted from the flash arc tube at an angle in the longitudinal direction is efficiently collimated. It has become like that.

  FIG. 13 is an optical path diagram schematically illustrating how the flash light travels in the light pipe. As in FIG. 12, the folded portion is omitted and only the upper half of the light beam is shown as a straight light path, and the effective portion contributing to the brightness of the image on the subject is drawn with a solid line and the invalid portion not contributing is drawn with a broken line. It was. From FIG. 13, light having an excessively large angle difference from the optical axis leaks from the light pipe without being totally reflected at the wall surface of the light pipe, but light until the incident angle on the wall surface reaches the critical angle is totally reflected and light. It can be seen that the light travels in the direction of the flash light exit while being confined in the pipe. For this reason, compared with the case where a light pipe is not used, the ratio of the light which can be utilized effectively can be increased significantly.

  In the optical axis bending portions 11b and 11c, if the direction of the optical axis is greatly bent, the incident angle of a lot of light on the reflecting surface becomes small, and the rate of leakage without being totally reflected increases. Therefore, the change in the direction of the optical axis is made smaller than the right angle at any of the bent portions of the optical axis.

  In the second embodiment, the optical axis bent portion 11b is provided with a reflecting surface having a parabolic cross section as a condensing means. However, the rotating paraboloidal surface is extended in the longitudinal direction of the flash arc tube, or a spherical surface is reflected. A surface may be provided. Moreover, you may provide a concave mirror also in the optical axis bending part 11c. Further, the condensing means does not need to be a single concave mirror, and a mirror surface finely divided like a Fresnel mirror may be used.

  In the above embodiment, the pattern mask is formed of a transparent film. However, a pattern mask function may be provided by engraving a concavo-convex pattern in a flash light emission port of a light pipe and utilizing refraction and reflection in the concavo-convex pattern.

  You can build a 3D model of a person or still life based on the measured data and publish it on the Internet or send it to a close friend or family member for viewing. Moreover, you may make it exist as a real avatar in the three-dimensional virtual space which is expanding as a business on the net.

2 Camera 3 Flash 11 Light Pipe 12 Pattern Mask 12a Line 12M Reference Mark 13 Projection Lens 14 Aperture 15 Calibration Plate 16 Flash Light Entrance 20 Subject 30 Mirror

Claims (9)

  Flash light introducing means for introducing flash light emitted from a shooting flash, and transmission on which a linear pattern is drawn to project a linear pattern light extending in a direction perpendicular to the parallax direction on the subject A pattern light projection apparatus comprising: a pattern mask of a mold; and imaging optical means having a wide optical path in a direction parallel to a linear pattern light formed by the pattern mask and a narrow optical path in a vertical direction.   The pattern light projector according to claim 1, further comprising a function of reflecting the flash light in an inner direction of the optical path on a side surface of the optical path from the flash to the pattern mask.   2. The pattern light projector according to claim 1, further comprising a diaphragm having an elongated slit-shaped opening having a width in a range of 1 mm to 4 mm in a direction perpendicular to the linear pattern light.   2. The pattern light projector according to claim 1, further comprising a reference mark serving as a reference for the position of the projected pattern light on the pattern mask.   A flash light entrance for introducing flash light emitted from a flash for photographing, a plurality of optical axis bending portions that bend the optical axis of the flash light by reflection, and an optical path for guiding the flash light in the direction of expanding parallax, The pattern light projector according to claim 1, further comprising a light pipe made of a transparent material and preventing light leakage using total reflection.   6. The pattern light projector according to claim 5, further comprising a light collecting unit in an optical path for guiding the flash light.   6. The pattern light projector according to claim 5, wherein the direction change of the optical axis in all the optical axis bent portions is made smaller than a right angle.   6. The pattern light projector according to claim 5, wherein a pattern mask is formed by unevenness carved in a flash light emission port of the light pipe.   A pattern light projection apparatus comprising a function of projecting pattern light having a plurality of areas that can be distinguished from other areas by different colors.

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