JPH04105476A - Omni-directional image pickup device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an omnidirectional photographing device capable of photographing in all directions with equal resolution.

[Background Art] In recent years, research has been actively conducted on using intelligent mobile robots to autonomously travel to a destination.

The above-mentioned intelligent mobile robot is required to recognize the road, move without deviating from the road, avoid obstacles, and reach the destination.

In order to meet this requirement, intelligent mobile robots must be equipped with an image input device that can input images from all directions simultaneously.

Two types of image input devices have been proposed as the above-mentioned conventional image input devices.

One type of image input device is a vertically oriented television camera combined with a fisheye lens, such as ``Guidance of a Mobile Robot Using an Omnidirectional Vision''.
Navigation φ System J (Guidance
of a Mobile Robot'Using
An 0mn1directional Viaion
Navigation S7S75je, SJ, Oh a
nd E., L. Hall), N.P.
SPIE Vol, 852. Mobile Robot (M.

bile Robots) II (1987).

In this image input device, the camera can capture images in all directions using a fisheye lens.

However, since it also captures images of the ceiling, sky, etc. that do not need to be observed, there is a lack of images in the horizontal direction that are actually needed.

Another type of image input device has been proposed to compensate for the drawbacks of the image input device described above.

This image input device uses conical mirrors, industrial
Television Camera [(InduNriaTV c
amera) (hereinafter referred to as ITV camera) and an image processing device, for example, ``Omnidirectional environment recognition using Yagi and Yoto two conical projections''.

Confucian techniques PRU89-46. (1989).

The configuration of a conventional image input device using a conical mirror is shown in the 10th example.
As shown in the figure.

In the figure, the conical mirror 111 is arranged vertically downward, and the viewing area reflected by the conical mirror 111 is 360 degrees around the vertical axis in the horizontal plane.

The image reflected by the conical mirror 111 is captured by the ITV camera 112, as shown in FIG. are expressed as corresponding to each.

For example, as shown in Fig. 13, if the character ``sha'' is arranged vertically with the horizontal direction θ, the distance Δr corresponds to the vertical length of the character ``sha'', and the distance Δr corresponds to the vertical length of the character ``sha''. The horizontal length corresponds to the angle Δθ.

Here, the ITV camera 112 operates in an orthogonal coordinate system, but the image of the character "sha" taken by the ITV camera 112 has a fan shape as shown in FIG. 14, and is an image in a polar coordinate system.

The image processing device 113 cuts out the image captured by the ITV camera 112 into a fan shape as shown in FIG. 14, converts the coordinate system of the cut portion from the polar coordinate system to the orthogonal coordinate system, Correct the image as shown in .

With the above method, images of the ceiling, sky, etc. that do not need to be observed are removed by the conical mirror 111, and only images in the horizontal direction that are actually necessary are taken in all directions.

In addition, as an omnidirectional photographing device using a polar coordinate type photographing device, for example, ``A Study of Polar Coordinate Type Line CCD Camera for Ariga, Yoshino, Ogo, Rowers, and Temples'' Transactions of the Institute of Electrical Engineers of Japan Vol.
, 109-C, No. 5, pp. 394-399
(Mg2. 1989) J is known.

[Problems to be Solved by the Invention] However, in the conventional omnidirectional imaging device using a conical mirror, the image captured by the ITV camera is cut into a fan shape, so the number of pixels in the angular direction increases from the outer periphery toward the center. There are problems in that the resolution becomes worse from the outer periphery toward the center, and the sampling rate in the angular direction becomes coarser from the outer periphery toward the center.

In addition, in conventional omnidirectional imaging devices that interpolate pixels on the center side by interpolation so that the number of pixels on the outer periphery and the center are equal, the interpolation method is equivalent to a low-frequency region filter (low-pass filter). However, there is a problem in that the spatial resolution on the center side deteriorates.

Further, in conventional omnidirectional imaging devices, the image processing device performs complex processing at high speed, resulting in a large size, which makes it difficult to incorporate into a moving body such as a robot.

SUMMARY OF THE INVENTION In view of the problems of the conventional omnidirectional photographing device described above, an object of the present invention is to provide a compact omnidirectional photographing device that has clear spatial resolution over all pixels and does not require image processing.

[Means for Solving the Problems] The above-mentioned object of the present invention is to provide a reflecting means for reflecting images in all directions in a predetermined direction, and a reflecting means that is arranged gradually from a first end toward a second end. and an imaging device that has an imaging device including a plurality of pixels and uses the imaging device to capture an image reflected by the reflecting device, and the imaging device rotates the imaging device about the central axis with respect to the central axis of the reflecting device. This is achieved by an omnidirectional imaging device configured to scan both in the direction and in the radial direction.

[Operation] The reflecting means reflects the omnidirectional image in a predetermined direction different from the direction in which the image is input, and the imaging means has a plurality of mirrors arranged gradually from the first end to the second end. An image sensor including pixels is scanned in the rotational direction of the central axis of the reflecting means and in the radial direction to capture an omnidirectional image reflected by the reflecting means with clear resolution.

[Example] Hereinafter, an example of an omnidirectional photographing device of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing the configuration of an omnidirectional imaging device according to a first embodiment of the present invention, and FIG. 2 is a schematic diagram showing the configuration of the embodiment device of FIG.

The omnidirectional photographing device shown in FIGS. 1 and 2 includes a reflecting mirror 11 as a reflecting means, a polar coordinate photographing device 12 as an imaging means, a condensing lens 13, and a rotating shaft 14 as a central axis.
The image pickup device is composed of a stepping motor 15 having a function of 1, and a fan-shaped image pickup device 16 as an element.

Next, the operation of the omnidirectional photographing device of this embodiment will be explained.

The reflecting mirror 11 has a conical shape, and is arranged downward in the vertical direction, that is, in the =2-axis direction when the Z-axis direction is the vertical direction.

In this embodiment, the reflective mirror booklet may be conical, polygonal pyramidal with reflective surfaces on its sides, or hemispherical.

The image reflected by the reflection mirror 11 is displayed by a radial distance r and a horizontal angle θ in a polar coordinate system (see FIG. 12).

In the vertical optical path reflected by the reflection mirror 11,
A polar coordinate photographing device 12 is arranged.

The image photographed by the polar coordinate photographing device 12 is directly outputted to a television camera or the like without going through an image processing device.

FIG. 3 shows the configuration of the polar coordinate photographing device 12 described above.

The polar coordinate photographing device 12 includes a condensing lens 13 and a rotating shaft 14.
The image sensor 16 is composed of a stepping motor 15 having a rotation axis 14, and a fan-shaped image sensor 16 attached to the rotating shaft 14 so as to extend in the radial direction.

Further, the configuration of the fan-shaped image sensor 16 described above is shown in FIG.

As shown in FIG. 4, the fan-shaped image sensor 16 has a plurality of pixels that are gradually arranged outward from the center of the rotation shaft 14 of the stepping motor 15.

Note that the first end of the fan-shaped image sensor 16 represents the end located on the center side of the rotating shaft 14, and the second end represents the end extending radially from the center.

The longer each pixel is disposed in the radial direction from the center of the rotation axis 14, the longer the length in the angular direction (θ direction).

Therefore, the area of each pixel increases as the pixel is arranged in the radial direction from the center of the rotation axis 14, and the width of each pixel in the radial direction is constant.

In this example, the pixel is a charge coupled device (hereinafter referred to as C
(referred to as CD).

Next, the operation of the above-mentioned polar coordinate photographing device 12 will be explained.

Every time the fan-shaped image sensor 16 scans in the radial direction of the rotating shaft 14 of the motor 15, the motor 15 slightly rotates the fan-shaped image sensor 16 in the angular direction (θ direction).

As shown in FIG. 4, the area of the pixels of the fan-shaped image sensor 16 is configured to increase from the center toward the outside, so that the image taken by the fan-shaped image sensor 16 is
As shown in the figure, the resolution in the angular direction and the resolution in the radial direction are the same.

In this case, an image expressed in a polar coordinate system is converted into an image in a rectangular coordinate system by extracting the electrical signal captured by the fan-shaped image sensor I6 using a slip ring, rotary transformer, etc., so it is not necessary to use an image processing device. do not have.

When photographing is performed using the polar coordinate type photographing device 12, a sample grid is generated in the shape of polar coordinates on the photographing surface of the fan-shaped image sensor 16.

The operation of how the generated sample grid samples the actual field of view will be explained below. Note that the operation of the sample grating will be described in terms of both the sample rate and the aperture opening ratio.

First, the radial direction of the imaging plane will be explained.

The distance from the center of the imaging plane (that is, the center of the rotating shaft 14 of the motor 15) is proportional to the angle in the vertical direction (vertical direction) in the actual field of view.

Therefore, samples in the vertical and angular directions within the viewing area are CC
It is determined by the arrangement of pixels in D.

By the way, the arrangement of pixels of a CCD is determined by the mechanical constants of the CCD and is uniform.

Therefore, the fan-shaped image sensor 16 operates so that the sample grid is uniform with respect to the actual field of view, so that the sample rate and aperture opening ratio are the same at each location.

Further, the sample rate in the angular direction is constant because it corresponds to a unit rotation angle of the step motor 15 on the imaging surface. Since the image is also projected in polar coordinates, it operates to sample in equal steps horizontally relative to the actual field of view, so it is the same at each location.

Further, since the area of a CCD pixel increases as it is arranged from the center toward the outer periphery, the angle at which the center of the CCD is viewed from each pixel is also constant. That is, the aperture opening ratio of the sample in the angular direction is also the same from the center of the CCD to the outer periphery.

As a result of (2), the fan-shaped image sensor 16 operates to generate a sample grid so as to produce a sample pattern 17 having an equal aperture ratio at the top and bottom of the screen, as shown in FIG.

According to the embodiment described above, the sampling rate and aperture opening ratio of the polar coordinate imaging device 12 are constant in both the radial direction and the angular direction of the imaging surface. Therefore,
Amplitude characteristics [modulation transfer function (Modulati)]
on T+ans [e+ Function), henceforth, M
TF] is constant.

FIG. 6 shows the configuration of a second embodiment of the polar coordinate photographing apparatus of the present invention.

In FIG. 6, the optical path of a reflecting mirror 11 similar to that of the first embodiment shown in FIGS. A photographing device 19 is arranged.

The filter 18 is configured such that the amplitude characteristic (MTF) decreases as it moves away from the center, as shown in FIG. As the filter 18, a commercially available optical filter can be used. In addition, instead of a commercially available optical filter, fine scratches, minute protrusions, dents, unevenness, etc. may be added to a glass plate or plastic plate, etc. Also, the same treatment may be applied to the condenser lens +3 (see Figure 3). may be applied.

The polar coordinate photographing device 19 shown in FIG. 8 includes the condensing lens 13 shown in FIG. It has a line-type image sensor 20 attached extending in the direction.

The line type image sensor 20 is a fan-shaped image sensor 1 shown in FIG.
6, a plurality of pixels are sequentially arranged from the end closest to the center of the rotation axis 14 as the first end toward the end farthest from the center in the radial direction as the second end. It is placed.

However, in the line type image sensor 20, the area of each pixel is
It is the same from the center to the outside, and the length in the radial direction is also constant.

The output signal of the line-type image sensor 20 is ignored for the central region where pixels overlap during rotation.

When photographing with the polar coordinate type photographing device 1119, the fan-shaped image pickup element 1 shown in FIG.
6, a polar sample grid is generated.

The operation of how the generated sample grid samples the actual field of view will be explained below. Note that the operation of the sample grating will be described in terms of both the sample rate and the aperture opening ratio.

First, the radial direction of the imaging plane will be explained.

In the actual field of view, the distance from the center of the imaging plane is the vertical direction (
vertical) angle.

Therefore, the samples in the vertical and angular directions within the field of view are CO
It is determined by the arrangement of pixels in D.

By the way, since the arrangement of pixels in a COD is determined by the mechanical constants of the CCD and is uniform, a line-type image sensor is used to generate a sample grid so that both the sample rate and aperture ratio are uniform with respect to the actual field of view. 2θ works.

The sampling rate in the angular direction is constant because it corresponds to a unit rotation angle of the step motor 15 on the imaging plane.

Since the image is also projected in polar coordinates, the line-type image sensor 20 operates to sample the actual field of view at equal steps in the horizontal direction. The sample is therefore uniform everywhere.

On the other hand, since the pixel size of COD is constant, COD
The angle from which the center is viewed from the pixel changes between the center and the outer periphery. That is, the aperture opening ratio of the sample in the angular direction is different between the center and the outer circumference of the COD. As a result, as shown in FIG. 9, the line type image sensor 20 operates so as to produce sample patterns 212223 having different aperture opening ratios at the top and bottom of the screen.

This means that the MTF of the polar coordinate imaging device 19 differs for each part of the image. Since the aperture opening ratio increases at the bottom of the screen, the MTF decreases at the bottom of the screen. Note that the sample rate is constant.

If the filter 18 is not arranged, as shown in FIG. 9, a sample pattern with different aperture opening ratios will be generated at the top and bottom of the photographic screen, or the filter 18 will reversely correct this amplitude characteristic (MTF), so the field of view will change. The amplitude characteristic (MTF) becomes constant in the entire region.

In the two embodiments described above, the fan-shaped image sensor 16 or the line-type image sensor 20 is attached to the rotating shaft 14 of the motor 15 so as to extend in the radial direction from the rotating shaft 14 .

However, the fan-shaped image sensor 16 or the line-type image sensor 20
Instead, a cross-shaped image sensor extending perpendicularly to the radial direction, a *-shaped image sensor extending toward the radial direction, or the like may be used.

Further, the fan-shaped image sensor 16 or the line-type image sensor 20 does not have to be arranged at right angles in the radial direction from the rotation axis 14 of the motor 15, but may be arranged so that it rotates at the same angle as a cone-shaped or polygonal pyramid-shaped reflecting mirror. It may be placed in Furthermore, instead of rotating the fan-shaped image sensor 16 or the line-type image sensor 20, a two-dimensional image sensor having polar coordinate addresses as shown in FIG. 10 may be used.

[Effects of the Invention] A reflecting means for reflecting an omnidirectional image in a predetermined direction;
and an imaging device for capturing an image reflected by the reflecting device with the imaging device, the imaging device including a plurality of pixels arranged gradually from the end of the mirror toward the second end;
The imaging means is configured to scan the imaging element in the rotational direction of the central axis and in the radial direction with respect to the central axis of the reflecting means, so that the resolution at the center of the element and the resolution at the outside are the same.

As a result, an image processing device that converts an image captured in a specific coordinate system to another coordinate system is not required, and a miniaturized omnidirectional imaging device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a schematic configuration of an omnidirectional photographing device according to a first embodiment of the present invention, FIG. 2 is a schematic diagram showing a schematic configuration of the embodiment device of FIG. 1, and FIG. FIG. 4 is an explanatory diagram showing the schematic configuration of the fan-shaped image sensor in FIG. 3, and FIG. 5 is a perspective view showing the schematic configuration of the polar coordinate imaging device in the first embodiment. An explanatory diagram showing the resolution, FIG. 6 is a schematic diagram showing the schematic configuration of an omnidirectional imaging device in the second embodiment of the present invention, FIG. 7 is a graph showing the characteristics of the filter in FIG. 6, and FIG. is an explanatory diagram showing the configuration of the line type image sensor of the polar coordinate type photographing device in FIG. 6,
Fig. 9 is an explanatory diagram showing the resolution of the polar coordinate photographing device in Fig. 6 without a filter, Fig. 10 is an explanatory diagram showing the pixels of a two-dimensional image sensor, and Fig. 11 is an explanatory diagram showing the resolution of the polar coordinate type photographing device in Fig. 6. FIG. 12 is an explanatory diagram of each variable of the polar coordinate system in a polar coordinate photographing device, FIG. 13 is an explanatory diagram showing a reflected image of the conical mirror in FIG. 11, and FIG. 14 is an image of FIG. 11. FIG. 15 is an explanatory diagram showing the operation of the processing device, and FIG. 15 is an explanatory diagram showing the resolution of the omnidirectional photographing device of FIG. 11...Reflection mirror, 12.19...Polar coordinate photographing device, 13...Condensing lens, 14...Rotation axis, 15
...Stepping motor, 16... Fan-shaped image sensor,
18... Filter, 20... Line type image sensor. Figure 2 Figure 31

Claims (1)

[Claims] a reflecting means for reflecting an omnidirectional image in a predetermined direction;
and an imaging device that has an imaging device including a plurality of pixels arranged gradually from an end toward a second end, and the imaging device captures the image reflected by the reflecting device, The omnidirectional photographing device is characterized in that the imaging means is configured to scan the imaging element in the rotational direction and radial direction of the central axis of the reflecting means.