JP4451233B2 - Multiband imaging device - Google Patents

Description

  The present invention relates to an imaging device mounted on a flying body such as a helicopter, an airplane, or an artificial satellite, and more particularly to a multiband imaging device configured to obtain a stereoscopic image and a color image of the ground surface.

  Conventionally, as a method for obtaining a two-dimensional color image of the ground surface, a plurality of line sensors respectively corresponding to a plurality of observation wavelength bands are arranged in parallel on the image plane of the imaging optical system, and a flying object such as an artificial satellite is connected to each line. A so-called image plane division method is known in which an image in each wavelength band is acquired while moving in a direction substantially perpendicular to the axial direction of the sensor (see Patent Documents 1 to 3 below).

  Further, in such a multiband imaging device using the image plane division method, the front perspective view (for the direction in which the flying object moves obliquely downward), the direct view (for the direction directly below the flying object), and the rear Three sets of line sensors for squint (for the direction of the aircraft moving backward and diagonally below) are mounted, and stereoscopic images of the ground surface based on the images with different line-of-sight directions captured by each set of line sensors Is known (high precision digital aviation sensor manufactured by Space Information Technology Laboratory Co., Ltd .; STARIMAGER (registered trademark)).

Japanese Examined Patent Publication No. 62-8731 JP-A-6-8897 JP 2002-214530 A

  In the image plane division method as described above, the timing for acquiring the image at the same position on the ground surface is slightly shifted between the line sensors in each wavelength band, so if the posture of the imaging camera changes due to the vibration of the flying object, etc. There is a problem that a positional shift occurs between the images in each wavelength band.

  Conventionally, in order to prevent such misalignment between images, a stabilizer with a built-in gyroscope is installed to stabilize the posture of the imaging camera, or a three-color line sensor is arranged in one CCD line sensor package. Measures such as reducing the deviation in acquisition timing are taken. However, since it is difficult to completely stabilize the posture of the imaging camera, it is inevitable that the image is misaligned due to the misalignment of the image acquisition timing. Even when image processing for correcting the misalignment is performed, each wavelength band It is difficult to obtain a highly accurate color image with a registration that is consistent.

  In order to prevent such positional shift between images in each wavelength band, a plurality of bands each belonging to each wavelength band of light beams from the same position, such as a color separation prism used in a three-plate color camera, etc. It is preferable to use a so-called coaxial color separation system that separates light into light beams. However, it is possible to avoid an increase in the size of the color separation prism by using a single color separation prism to obtain images required for obtaining a stereoscopic image that have different imaging directions. Therefore, it is difficult to secure an arrangement space in the apparatus, which is not realistic.

  The present invention has been made in view of such circumstances, and provides a multiband imaging device capable of obtaining a high-accuracy color image together with a stereoscopic image without positional deviation between images in each wavelength band. The purpose is to do.

  In order to achieve the above object, the multiband imaging device of the present invention is configured as follows. That is, in the multiband imaging device according to the present invention, in the multiband imaging device mounted on the flying object, the imaging lens system installed so as to be able to image the ground surface, and the direction from directly below the flying object, A direct-view color separation having a color separation prism that separates a light beam obtained through an imaging lens system into a plurality of band light beams having different wavelength bands and guides each light beam to an image sensor for each wavelength band An imaging system; and a perspective imaging system having a light guide prism that guides a light beam obtained through the imaging lens system obliquely from below the moving direction of the flying object to an imaging device for perspective, A direct-view color image is obtained from a direct-view image of each wavelength band obtained by the color separation imaging system, and a direct-view image of a predetermined wavelength band obtained by the direct-view color separation imaging system and the perspective imaging system Obtained perspective view That is configured to obtain a stereoscopic image from that characterized in.

  The “wavelength band” may include a wavelength band outside the visible range. Therefore, the “color separation prism” includes IR (infrared), other than a general one that separates white light into three wavelength bands of R (red), G (green), and B (blue). The color separation into a plurality of wavelength bands including UV (ultraviolet) is also included.

  In the present invention, each of the color separation prism and the light guide prism has a glass length for each band light flux passing through the color separation prism and a glass length for the light flux passing through the light guide prism. Preferably, the imaging lens systems are configured to be substantially telecentric on the image side.

  The “glass length” means that the principal ray of the light beam incident on the prism via a predetermined lens system is assumed to be parallel to the optical axis of the lens system. Means the length of the prism along the trajectory followed by

  In addition, the perspective imaging system includes a front perspective imaging system that guides a light beam from obliquely downward in the moving direction of the flying object to an imaging device for forward perspective through a forward light guide prism, and an obliquely backward in the moving direction of the flying object. A rear perspective imaging system that guides a light beam from below to a rear perspective imaging device via a rear light guide prism can be configured.

  In this case, the light guide prism for the rear, the color separation prism and the light guide prism for the front are arranged in this order from the front in the moving direction of the flying object, and the light flux from the immediately lower direction incident on the color separation prism is the imaging lens system. It is preferable to constitute so as to pass through the substantially central portion.

  According to the multiband imaging device according to the present invention, the color separation prism is arranged in the direct-view color separation imaging system and the light guide prism arranged in the perspective imaging system is used in combination. This makes it easy to secure the arrangement space.

  The direct-view images in each wavelength band obtained by the direct-view color separation imaging system are obtained by each band light beam that is color-separated on the same axis by the color separation prism. Misalignment does not occur. Therefore, it is possible to obtain a highly accurate nadir color image.

  It is also possible to obtain a stereoscopic image in combination with a direct-view color image by providing a perspective imaging system that guides the light beam obliquely from below in the moving direction of the flying object to the perspective imaging device by the light guide prism. It is.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram schematically showing an overall configuration of a multiband imaging apparatus according to an embodiment of the present invention.

  A multiband imaging device according to the present embodiment (hereinafter sometimes referred to as “the present embodiment device”) is a flying object (not shown) that travels in a relatively low sky such as a helicopter (the movement direction is indicated by an arrow A). The imaging lens system 10, the direct-view color separation imaging system 20, the front perspective imaging system 30, the rear perspective imaging system 40, and the image signal processing means 50 are mounted in an apparatus housing (not shown). I have.

  The imaging lens system 10 is installed so as to be able to image a ground surface (not shown) located below the plane of the paper, and is incident from the ground surface obliquely from the front in the traveling direction of the flying object (indicated by an arrow α in the figure). Direction) light beam, a light beam from directly below the aircraft (indicated by arrow β in the figure), and a light beam from obliquely forward (indicated by arrow γ in the figure) in the moving direction of the flying object. 40, the direct-view color separation imaging system 20 and the front perspective imaging system 30 are configured to emit light respectively.

  The direct-view color separation imaging system 20 includes a color separation prism 22 composed of six prisms 22a to 22f, and wavelength bands each composed of a CCD line sensor and the like disposed on each light emitting end face side of the prisms 22c to 22f. Image sensors 24a to 24d (24a is for the blue (B) wavelength band, 24b is for the green (G) wavelength band, 24c is for the red (R) wavelength band, and 24d is the infrared (IR) wavelength. The light beam from directly below the flying object emitted from the imaging lens system 10 is color-separated into each of the band light beams belonging to the four wavelength bands of B, G, R, and IR, Each is configured to be guided to each of the imaging elements 24a to 24d. Note that predetermined joints (not shown) are provided at the joints of the prisms 22b and 22c, the joints of 22c and 22d, and the joints of 22d and 22e.

  The front perspective imaging system 30 includes a front light guide prism 32 including two prisms 32a and 32b, and a front perspective (red wavelength band) imaging device 34 disposed on the light emission end face side of the prism 32b. The light beam emitted from the imaging lens system 10 and obliquely forward and downward in the moving direction of the flying object is guided to the imaging element 34 via the front light guide prism 32. . A filter (not shown) that selectively transmits light in the red wavelength band is provided between the prism 32b and the image sensor 34, and a junction between the prisms 32a and 32b is provided. A predetermined gap (not shown) is provided.

  The rear perspective imaging system 40 includes a rear light guide prism 42 composed of two prisms 42a and 42b, and a rear perspective imaging (for red wavelength band) imaging element 44 disposed on the light exit end face side of the prism 42b. And is configured to guide a light beam emitted from the imaging lens system 10 from obliquely downward and rearward in the moving direction of the flying object to the imaging element 44 via a rear light guide prism 42. . A filter (not shown) that selectively transmits light in the red wavelength band is provided between the prism 42b and the imaging device 44, and a junction between the prisms 42a and 42b is provided. A predetermined gap (not shown) is provided.

  The image signal processing means 50 includes an image input interface for inputting image signals photoelectrically converted and output by the image pickup devices 24a to 24d, 34, and 44, a memory, a CPU, a graphics board, and the like. A computer (both not shown) is provided. Then, the image signal processing means 50 performs a direct view color image based on the image signals from the three image pickup devices 24a to 24c of the direct view color separation image pickup system 20, and a direct view based on the image signal from the image pickup device 24f. While obtaining each visible infrared image, the image signal from the imaging device 34 of the front perspective imaging system 30, the image signal from the imaging device 44 of the rear perspective imaging system 40, and the imaging of the direct-view color separation imaging system 20 A stereoscopic image of the ground surface is obtained based on the image signal from the element 24c.

  According to the apparatus of the present embodiment described above, the color separation prism 22 disposed in the direct-view color separation imaging system 20 and the front light guide prism 32 disposed in the front perspective imaging system 30 and the rear perspective imaging system 40, respectively. Further, by using the light guide prism 42 in combination with the rear light guide prism 42, it is easy to secure the arrangement space by avoiding the enlargement of the color separation prism 20.

  Since the direct-view image in each wavelength band obtained by the direct-view color separation imaging system 20 is obtained by each band light beam that is color-separated coaxially by the color separation prism 22, There will be no misalignment. Therefore, it is possible to obtain a highly accurate nadir color image.

  In addition to the direct-view color separation imaging system 20 that obtains an image directly below the flying object, a front perspective imaging system 30 that obtains an image that is obliquely forward and downward in the moving direction of the flying object; By providing the rear perspective imaging system 40 for obtaining an image, it is also possible to obtain a highly accurate stereoscopic image of the ground surface.

  The color separation prism 22, the front light guide prism 32, and the rear light guide prism 42 described above have their respective prism lengths, that is, the glass lengths of the respective band light fluxes passing through the color separation prism 22, and the front guides. The glass lengths of the light beams respectively passing through the optical prism 32 and the rear light guide prism 42 are configured to be substantially equal to each other. Thereby, it is possible to obtain an image in which the occurrence of various aberrations is suppressed by the single imaging lens system 10.

  The imaging lens system 10 is configured to be substantially telecentric on the image side. Thereby, the difference in the incident angle in the direction perpendicular to the paper surface of the light beams emitted from the imaging lens system 10 and incident on the prisms 22, 32, 42 can be reduced. , 42 can suppress a change in characteristics due to a difference in incident angle of each light beam.

  Further, the rear light guide prism 42, the color separation prism 22 and the front light guide prism 32 described above are arranged in this order from the front in the moving direction of the flying object, and are directly below the flying object which enters the color separation prism 22. A light beam from the direction is configured to pass through a substantially central portion of the imaging lens system 10. Thereby, when the single imaging lens system 10 is used, the direct-view color separation imaging system 20, the front perspective imaging system 30, and the rear perspective imaging system 40 can be arranged in a compact manner. It is possible to further improve the accuracy of the visual color image.

  In the above-described embodiment, the color separation prism 22 is configured with four bands of R, G, B, and IR. However, the color separation prism according to the present invention has a three-band configuration of R, G, and B. Various types can be used, such as those having a five-band configuration in which UV (ultraviolet) is added to the four bands.

  Further, in the above-described embodiment, the front perspective imaging system 30 and the rear perspective imaging system 40 are provided, which makes it possible to obtain a highly accurate stereoscopic image, but in the present invention, A configuration in which either one of these is omitted is also possible.

  In the above-described embodiment, a helicopter is illustrated as a flying object. However, the present invention can be applied to a multiband imaging device mounted on various flying objects such as airplanes, airships, and artificial satellites. .

1 is an overall configuration diagram of a multiband imaging device according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Imaging lens system 20 Direct-view color separation imaging system 22 Color separation prisms 22a-22f (The color separation prism is comprised) Prism 24a-24d, 34, 44 Image pick-up element 30 Front perspective imaging system 32 Front light guide prism 32a, 32b (Constructs a light guide prism for the front) Prism 40 Rear perspective imaging system 42 Light guide prisms for the rear 42a, 42b Prism (configures the light guide prism for the rear) 50 Image signal processing means A Traveling direction α, β , Γ Direction of light flux from the ground surface

Claims (5)

In a multiband imaging device mounted on a flying object,
An imaging lens system installed so that the ground surface can be imaged;
The light beam obtained through the imaging lens system from the direction directly below the flying object is color-separated into a plurality of band light beams having different wavelength bands, and each band light beam is used as an imaging device for each wavelength band. A direct-view color separation imaging system having a color separation prism for guiding;
A perspective imaging system having a light guide prism that guides a light beam obtained through the imaging lens system obliquely from below the moving direction of the flying object to a perspective imaging device;
A direct-view color image is obtained from a direct-view image in each wavelength band obtained by the direct-view color separation imaging system, a direct-view image in a predetermined wavelength band obtained by the direct-view color separation imaging system, and the perspective view A multiband imaging device configured to obtain a stereoscopic image from a perspective image obtained by an imaging system.   In the color separation prism and the light guide prism, each glass length for each band light beam passing through the color separation prism is substantially equal to a glass length for the light beam passing through the light guide prism. The multiband imaging device according to claim 1, wherein the multiband imaging device is configured as described above. The perspective imaging system is
A front perspective imaging system that guides a light beam from obliquely downward in the moving direction of the flying object to an imaging device for front perspective through a front light guide prism;
3. The multi-purpose camera according to claim 1, further comprising a rear perspective imaging system that guides a light beam from obliquely lower rear in the moving direction of the flying object to a rear perspective imaging device via a rear light guide prism. Band imaging device. The rear light guide prism, the color separation prism, and the front light guide prism are arranged in this order from the front in the moving direction of the flying object,
4. The multiband imaging device according to claim 3, wherein the light beam from the immediately lower direction incident on the color separation prism is configured to pass through a substantially central portion of the imaging lens system. The multiband imaging device according to any one of claims 1 to 4, wherein the imaging lens system is configured to be substantially telecentric on an image side.

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