JP2020064162A - Optical system and accessory device and imaging device equipped with the same - Google Patents

Abstract

To provide an optical system with which the aberration of a plurality of lens parts is suitably corrected, and an accessory device and an imaging device provided with this optical system.SOLUTION: An optical system 100 comprises a lens array 21 having a plurality of lens parts each forming the image of an object, and a filter array 22 having a plurality of filters arranged on the optical axes of the plurality of lens parts. The plurality of filters include three or more filters arrayed in a first direction, the three or more filters including a first filter F22 the center wavelength in transmission wavelength range of which is shortest among the plurality of filters and a second filter F12 the center wavelength in transmission wavelength range of which is longer than the first filter, with the first filter F22 arranged at a position closer to the center (AX0) of the filter array 22 than is the second filter F12.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical system including a plurality of lens units each forming an image of an object, and is suitable for an image pickup apparatus such as a digital still camera or a video camera.

  As an optical system used in an image pickup apparatus, there is known an optical system that forms a plurality of images of the same object (subject) with a plurality of lenses. In such an optical system, by providing a plurality of filters having different transmission characteristics on the optical axes of a plurality of lenses, it is possible to simultaneously obtain a plurality of different image information by a single image pickup.

  Patent Document 1 describes an optical system including a plurality of filters having mutually different center wavelengths in a transmission wavelength range.

JP, 2017-208761, A

  However, in Patent Document 1, no consideration is given to the relationship between the aberrations generated according to the transmission wavelength bands of the plurality of filters and the decentering aberrations of the plurality of lenses. Specifically, in the optical system of Patent Document 1, a filter corresponding to a short wavelength region where it is more difficult to correct aberration is arranged at a position largely separated from the optical axis of the objective lens. With this configuration, since eccentric aberration is combined with chromatic aberration caused by the filter, it becomes difficult to obtain good image information corresponding to the short wavelength region.

  An object of the present invention is to provide an optical system in which aberrations of a plurality of lens units are favorably corrected, an accessory device including the optical system, and an imaging device.

  In order to achieve the above object, an optical system according to one aspect of the present invention includes a lens array having a plurality of lens units each forming an image of an object, and an optical system arranged on the optical axes of the plurality of lens units. A filter array having a plurality of filters, wherein the plurality of filters include three or more filters arranged in the first direction, and the three or more filters are transmission wavelength bands of the plurality of filters. Includes a first filter having a shortest center wavelength and a second filter having a center wavelength in a transmission wavelength range longer than the first filter, the first filter having the It is characterized in that it is arranged at a position close to the center of the filter array.

  According to the present invention, it is possible to provide an optical system in which aberrations of a plurality of lens units are favorably corrected, an accessory device including the optical system, and an imaging device.

1 is a schematic view of a main part of an imaging system according to a first embodiment. FIG. 3 is a diagram showing MTF performance in Example 1 and a comparative example. FIG. 6 is a schematic view of a main part of a filter array according to a modification.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, each drawing may be drawn on a scale different from the actual scale for convenience. Further, in each drawing, the same reference numerals are given to the same members, and duplicate explanations are omitted.

[Example 1]
FIG. 1 is a schematic view (schematic diagram) of a main part of an imaging system 100 according to a first embodiment of the present invention. FIG. 1A shows a cross section (YZ cross section) including an optical axis of a part of a plurality of lens portions described later. The optical axis here means an axis passing through the center (vertex) of each optical surface (each lens surface) in each lens portion. FIG. 1A shows a marginal ray of an axial light flux that is condensed at the axial image height of each lens unit. In addition, FIG. 1B is a front view of a filter array 22 described below as viewed from the object side (−Z side). Note that an object (not shown) that is an imaging target is arranged on the object side of the imaging system 100.

  The imaging system 100 includes an imaging device (camera unit) 1, an optical device (array unit) 2, an adapter device (adapter unit) 4, and a lens device (lens unit) 3, which are arranged in order from the image side (+ Z side). Have.

  The imaging device 1 includes an imaging element (light receiving element) 11 including an imaging surface (light receiving surface) arranged on the image surface of the optical device 2, and a holding member (housing) 12 that holds the imaging element 11. As the image sensor 11, a photoelectric conversion element such as a CCD sensor or a CMOS sensor can be adopted. Further, the image pickup device 11 may be configured to photoelectrically convert not only visible light but also infrared light (near infrared light or far infrared light). For example, an image sensor using a material such as Si, InGaAs, InAsSb may be adopted depending on the wavelength band used. Further, it is desirable that the number of pixels of the image pickup device 11 be determined based on the resolution required in the image pickup system 100.

  The optical device 2 includes an optical system and a holding member (lens barrel) 23 that holds the optical system. The optical system according to the present embodiment includes a lens array 21 having a plurality of lens portions each forming an image of an object, and a filter array 22 having a plurality of filters arranged on the optical axis of each lens portion. As shown in FIG. 1B, the plurality of filters in the filter array 22 are arranged in the first direction (X direction or Y direction) perpendicular to the optical axis (main optical axis) AX0 of the lens device 3 and the adapter device 4. It contains three or more filters arranged.

  Each of the plurality of lens units according to the present embodiment includes one or more lenses, and each forms an image of an object on the image pickup surface of the image pickup element 11. In other words, on the image plane of the lens array 21, a plurality of images of the object (image array) are formed by the plurality of lens portions. That is, according to the lens array 21, the images of the same object can be duplicated. It should be noted that the plurality of lens portions may be integrally formed for facilitating manufacturing or arrangement, or may be separately formed for enabling individual position adjustment (focus adjustment, etc.). Good.

  The plurality of filters (optical filters) according to the present embodiment include a plurality of filters having different transmission characteristics. Specifically, it includes two or more filters having wavelength bands (transmission wavelength bands) different from each other. Further, among the three or more filters arranged in the first direction, the first filter having the shortest center wavelength in the transmission wavelength band in the filter array 22 and the filter having the center wavelength in the transmission wavelength band more than the first filter A long second filter is included.

  Note that the transmission characteristics here include not only the wavelength band of transmitted light (transmitted wavelength region), but also the direction and type of polarized light to be transmitted (polarization state), the intensity of transmitted light with respect to the intensity of incident light (transmittance). It is an optical characteristic that changes the state of incident light, including the above. That is, the filter array 22 may include a plurality of polarizing filters having different types, a plurality of filters having different transmittances, and the like. By configuring the filter array 22 with a plurality of filters having different transmission characteristics, it is possible to simultaneously obtain a plurality of different image information for the same object.

  Specifically, by using a plurality of filters (bandpass filters) having different central wavelengths in the transmission wavelength range, it is possible to simultaneously obtain a plurality of image information corresponding to a plurality of wavelength bands. At this time, it is desirable to configure the imaging system 100 as a multi-spectral camera capable of acquiring image information corresponding to four or more types of wavelength bands, which is larger than the wavelength band (RGB) of a general camera. Furthermore, it is more preferable to configure the imaging system 100 as a hyperspectral camera capable of acquiring image information corresponding to 100 or more wavelength bands. Instead of the bandpass filter, a wavelength conversion filter that converts the wavelength of incident light and emits it may be used.

  Alternatively, by using a plurality of polarization filters of different types, it is possible to simultaneously acquire a plurality of image information corresponding to a plurality of polarization states. For example, three linear polarization filters that transmit linearly polarized light in directions parallel to the X direction (horizontal direction), the Y direction (vertical direction), the direction of 45 ° with respect to the X direction and the Y direction, and circularly polarized light. It is conceivable to use a circular polarization filter that transmits the light. In this way, by using a plurality of types of polarization filters that change the polarization state of incident light, it is possible to acquire polarization information such as the polarization characteristic (Stokes parameter) of the object and the two-dimensional distribution of the polarization state of the object. it can.

  Further, by configuring the filter array 22 with a plurality of filters having different types of transmission characteristics, it is possible to simultaneously obtain different types of information such as wavelength information, polarization information, brightness information, and parallax information. At this time, the plurality of filters of different types are not limited to being arranged on the optical axes of different lens parts, but may be arranged on the same optical axis. In the latter case, the acquired image information can be separated into different types of image information by filtering with an image processing unit (not shown).

  Further, the image pickup device 11 which is generally made of a silicon material used in the visible wavelength band has a higher sensitivity to the central wavelength band (near 550 nm) than to the short wavelength band (450 nm or less) and the long wavelength band (750 nm or more). It has a higher sensitivity characteristic. Therefore, when using a plurality of bandpass filters corresponding to each of these wavelength bands, it is preferable to arrange the neutral density filter on the optical axis where the bandpass filter corresponding to the central wavelength band is arranged. At this time, by using the polarization filter as a neutral density filter, not only can the brightness balance of each image information be corrected, but also wavelength information and polarization information can be acquired at the same time.

  The filter array 22 only needs to include at least two filters having different central wavelengths in the transmission wavelength range. In other words, the filter array 22 may include a plurality of filters having the same transmission characteristics. For example, when the image pickup system 100 is used as a distance measuring device (stereo camera), since the distance information of the object is acquired using two pieces of image information having different parallax, the transmission characteristics of the two filters corresponding to each piece of image information are calculated. It is desirable to make them approximately equal. However, in order to acquire a plurality of different pieces of image information in a single image pickup, it is desirable that all the transmission characteristics of the plurality of filters be different from each other.

  The filter array 22 according to the present embodiment includes nine filters F11 to F33 arranged in the X direction and the Y direction, as shown in FIG. Further, the lens array 21 includes nine lens portions corresponding to nine filters. That is, assuming that the lens unit and the filter arranged on the same optical axis are combined into one image forming unit, the optical device 2 has nine image forming units. The plurality of image forming units are collectively referred to as an image forming unit array.

  The number of image forming units is not limited to this, and the optical device 2 may include at least three image forming units arranged in the first direction. However, in order to acquire image information corresponding to more transmission characteristics in one image pickup, it is desirable to provide four or more image forming portions, and nine or more image forming portions are provided as in the present embodiment. Is more preferable. The light from the object reaches the image pickup surface of the image pickup device 11 via the lens array 21 and the filter array 22 in order. At this time, nine images (replica images) are formed on the imaging surface according to each image forming unit.

  In order to reduce the size of the image pickup apparatus 1, it is desirable to provide a common (single) image pickup element for each lens unit like the image pickup element 11 according to the present embodiment. Further, by using a common image pickup element for each lens unit, good image information can be acquired even when the number or arrangement of the lens units changes due to replacement of the optical device 2. At this time, in order to improve the utilization efficiency of the image pickup device 11, it is desirable that the plurality of pixels (photodiodes) forming the image pickup device 11 are uniformly arranged with as little space as possible.

  However, if necessary, an image sensor may be provided for each lens unit. In this case, in order to reduce the size of the entire apparatus, it is desirable to arrange the image pickup elements uniformly with as little space as possible. Further, in order to reduce the size of the optical device 2, it is desirable to arrange each lens unit according to the shape of the image pickup surface of the image pickup device 11. Specifically, it is desirable to arrange each lens portion in a square shape in the XY cross section. When the image pickup surface of the image pickup device 11 is not square, the aspect ratio of the arrangement of each lens unit may be changed.

  The order of arrangement of the lens array 21 and the filter array 22 in the optical axis direction is not limited to that shown in FIG. For example, when an interference type bandpass filter is used, the filter array 22 is placed closer to the object side than the lens array 21 so that the incident angle of light with respect to each filter becomes small in view of its angle characteristic (angle dependency). It is preferable to arrange them. However, when each lens part in the lens array 21 has sufficient telecentricity, even if the filter array 22 is arranged on the image side (+ Z side) of the lens array 21, the light for each filter is The incident angle can be reduced.

  Further, when the filter array 22 is arranged closer to the object side than the lens array 21, there is a possibility that off-axis rays entering the lens array 21 may be chipped (vignetting). Therefore, for example, when a filter having a small angle dependency such as an absorption bandpass filter is used, or when the light utilization efficiency is prioritized over the angle dependency of the filter, the filter array 22 is arranged closer to the image side than the lens array 21. It is preferable to arrange them in

  In the present embodiment, the lens array 21 and the filter array 22 are integrally held by the holding member 23, so that the displacement of their relative positions is suppressed. Further, the holding member 23 has a first mount portion (first coupling portion) 24 for coupling with the imaging device 1. Accordingly, the optical device 2 can be attached to and detached from the imaging device 1 via the first mount portion 24 as an accessory device. That is, it becomes possible to simultaneously replace the lens array 21 and the filter array 22 with respect to the imaging device 1 while holding them integrally.

  According to this configuration, it is possible to change the type and resolution of the image information to be acquired while suppressing the displacement of the relative positions of the lens array 21 and the filter array 22. Specifically, when the filter array 22 is replaced with one having a different transmission characteristic, the lens array 21 can be replaced with a corresponding one (optimized) corresponding to each filter array at the same time. This makes it possible to suppress aberrations and changes in focus of each lens. Also, the resolution of the imaging system 100 can be changed by replacing the lens array 21 with one having a different number of lens units. Also in this case, the filter array 22 can be simultaneously replaced with one corresponding to each lens array.

  As described above, according to the imaging system 100 according to the present embodiment, the optical device 2 can be exchanged according to the image information to be acquired. In particular, since the lens array 21 is replaceable, the type of image information (the number of bands, etc.) and the resolution can be increased or decreased by increasing or decreasing the number of lens units. Further, since the lens array 21 and the filter array 22 can be integrally replaced, it is possible to suppress a change in optical performance at the time of replacement. As a result, regardless of the configuration of the optical device 2, it becomes possible to simultaneously obtain a plurality of good image information by the common imaging device 1.

  The shape of the first mount section 24 may be a shape corresponding to the mount section 13 provided in the imaging device 1. For example, a coupling portion (a convex portion, a concave portion, a magnet, or the like) provided on the circumference surrounding the imaging surface when viewed from the optical axis direction (Z direction) can be adopted as the first mount portion 24. In FIG. 1A, the first mount portion 24 is shown as a concave portion and the mount portion 13 of the imaging device 1 is shown as a convex portion, but the shape of each mount portion is not limited to this. Further, it is preferable to provide the first mount portion 24 with an electrical contact (terminal) for electrically connecting to the image pickup apparatus 1. As a result, the optical device 2 can communicate with the imaging device 1 and receive power from the imaging device 1 via the electrical contacts.

  As shown in FIG. 1A, the holding member 23 includes not only the first mount portion 24 provided on the image side but also the second mount portion (second coupling portion) 25 provided on the object side. May have. Accordingly, accessory devices such as the lens device 3 and the adapter device 4 can be attached to and detached from the optical device 2. In FIG. 1A, the second mount portion 25 is shown as a convex portion, but the shape of the second mount portion 25 is not limited to this, and it may be changed according to the shape of the mount portion in the accessory device to be mounted. Just set it. Note that it is preferable that the second mount portion 25 also be provided with an electrical contact for performing communication and receiving and supplying power to the accessory device.

  When the optical device 2 is attached to the image pickup apparatus 1, an attachment error may occur depending on the manufacturing accuracy of each mount portion, and an error may occur in the positional relationship between the lens array 21 and the filter array 22 and the image pickup element 11. There is a nature. When such an error occurs, defocus of the lens array 21 with respect to the image pickup surface of the image pickup device 11 occurs. Therefore, it is desirable to provide a moving mechanism for moving the lens array 21 in the optical axis direction so that the focus of the lens array 21 can be adjusted.

  Alternatively, instead of the lens array 21, a moving mechanism for moving the image pickup device 11 in the optical axis direction may be provided so that focus adjustment (sensor focus) can be performed by moving the image pickup device 11. Note that the image plane of the lens array 21 may be tilted with respect to the image pickup plane due to a mounting error of the optical device 2, and thus field curvature and different focus shifts for each lens unit may occur. Therefore, it is preferable that the inclination (tilt angle) of the image sensor 11 with respect to the optical axis can be changed. Further, image blur correction (camera shake correction) may be performed by moving the image sensor 11 in a direction including a component in a direction perpendicular to the optical axis.

  It is desirable that all the lens parts in the lens array 21 include lens surfaces of the same shape. This facilitates the manufacture of each lens unit and reduces the cost of the lens array 21. At this time, it is more preferable that the shape of each lens portion is the same as each other, but the shape of each lens portion may be different from each other if necessary. In addition, the chromatic aberration may be better corrected by configuring each lens unit with a plurality of lenses arranged on the optical axis. In addition, when the difference in the transmission wavelength range of each filter (the wavelength band used by the imaging system 100) is large and it is difficult to correct the chromatic aberration, the respective imaging positions (axial chromatic aberration) are moved by individually moving each lens. You may adjust.

  The lens device 3 according to the present embodiment includes an optical system 31 having one or more lenses that are common to each image forming unit of the optical device 2 and a holding member (lens barrel) 32 that holds the optical system 31. I have it. The lens device 3 plays a role of converting the angle of view (image pickup angle of view) of the image pickup system 100. That is, by exchanging the lens device 3 with one having a different configuration of the optical system 31, it is possible to acquire image information corresponding to various angles of view. It should be noted that the angle of view of the imaging system 100 can be changed by configuring each lens unit in the lens array 21 with a plurality of lens groups without using the lens device 3 and changing the interval between adjacent lens groups. Is also possible. However, in that case, the difficulty of manufacturing and controlling the lens array 21 becomes high, and the configuration of the optical device 2 becomes complicated and large.

  Therefore, in order to simplify and downsize the optical device 2, it is desirable that the angle of view of the imaging system 100 can be changed by replacing the lens device 3 as in the present embodiment. Note that focus adjustment (focusing) may be performed by making at least one lens included in the optical system 31 of the lens device 3 movable. Further, the optical system 31 may be composed of a plurality of lens groups, the distance between adjacent lens groups may be changed, and the focal length of the imaging system 100 may be changed to adjust the angle of view and the imaging magnification. .

  The adapter device 4 according to this embodiment includes a diffusing element 41 that diffuses light, an optical system (optical unit) 42 having one or more lenses, and a holding member 43 that holds the diffusing element 41 and the optical system 42. ing. The diffusing element 41 is arranged at the position of the intermediate image plane (primary image plane) formed by the lens device 3, and plays a role as a screen. As the diffusing element 41, a diffusing member (diffusing plate) having a diffusing surface (rough surface), a microlens array including a plurality of fine lenses, or the like can be used. The optical system 42 has a function as a collimator optical system that converts the light from the diffusion element 41 into parallel light and guides it to the optical device 2. However, parallel light here is not limited to strict parallel light, and includes substantially parallel light (weakly divergent light or weakly convergent light).

  As described above, the transmission wavelength of the interference type bandpass filter has angle dependence, and generally, the variation of the central wavelength of the transmission wavelength band becomes larger as it goes to the longer wavelength side. Further, when the bandpass filter is arranged at a position distant from the main optical axis AX0, the angle of light incident on the bandpass filter is likely to be large, so that the variation angle of the central wavelength in the transmission wavelength range can be large. There is a nature. Therefore, by making the light incident on the filter array 22 into parallel light by the adapter device 4, the incident angles of the light with respect to the respective filters become substantially the same regardless of the position, so that the change of the angle dependence due to the arrangement of the respective filters is suppressed. can do.

  The holding member 32 in the lens device 3 and the holding member 43 in the adapter device 4 have a mount portion 33 and a mount portion 45 for coupling with each other. Accordingly, the lens device 3 can be attached to and detached from the optical device 2 via the adapter device 4. Further, the holding member 43 of the adapter device 4 has a mount portion 44 for coupling with the second mount portion 25 of the optical device 2. As a result, the adapter device 4 can be attached to and detached from the optical device 2 via each mount. At this time, even if the lens device 3 cannot be directly attached / detached to / from the imaging device 1 and the optical device 2, it can be attached / detached indirectly via the adapter device 4.

  However, it is desirable that the first mount portion 24 of the optical device 2 and the mount portion 33 of the lens device 3 have the same shape, and the mount portion 13 of the imaging device 1 and the mount portion 45 of the adapter device 4 have the same shape. . In other words, it is desirable that the lens device 3 that is attachable to and detachable from the image pickup device 1 be also attachable to and detachable from the adapter device 4. This makes it possible to configure an imaging system that can simultaneously acquire a plurality of pieces of image information by one-time imaging by using the imaging device 1 as a general camera and the lens device 3 as a general interchangeable lens. .

  Further, the imaging system 400 according to the present embodiment adopts a configuration in which parallel light is incident on the optical device 2 by using the adapter device 4. As a result, the optical device 2 according to the present embodiment can be applied to a lens device that does not form an intermediate image of an object. Therefore, in order to ensure compatibility between the optical device 2, the lens device 3, and the adapter device 4, the mount portion of each device may have the same shape regardless of the configuration of each optical system. desirable.

  When using a lens device that forms an intermediate image of an object like the lens device 3 of the present embodiment, it is desirable to dispose a field stop at the position of the intermediate image plane. Thereby, the shape and size of the boundary of each image formed on the image pickup surface of the image pickup device 11 can be appropriately set. For example, when the lights from the respective image forming units interfere with each other on the imaging surface, the size of the aperture (aperture diameter) provided in the field stop may be reduced. At this time, in order to improve the utilization efficiency of the image pickup device 11, it is desirable that the aperture of the field stop has a shape such as a rectangle that can equally divide the image pickup surface.

  Further, the boundary of each image on the image pickup surface becomes clearer as the field stop is closer to the position of the intermediate image plane. Therefore, when the diffusion element 41 is arranged at the position of the intermediate image plane as in the present embodiment, the field stop is reduced. Is preferably arranged so as to be in close contact with the diffusing element 41. At this time, when the diffusing element 41 has a thickness, it is more preferable to arrange the field stop on the image side of the diffusing element 41 in order to reduce the influence of scattering inside the diffusing element 41. In the present embodiment, a light-shielding member (light-shielding paint) is provided in addition to the central portion (rectangular portion) of the diffusing element 41, so that the diffusing element 41 can have a function as a field stop. Alternatively, the field stop and the diffusing element 41 may be integrally configured by disposing the diffusing element 41 in the opening provided in the light shielding member that constitutes the field stop.

  When the diffusing element 41 is arranged at the position of the intermediate image plane, the light from the lens device 3 is diffused by the diffusing element 41, so information about the incident angle of the light from the lens device 3 is lost, and the parallax of each image is reduced. Occurrence can be suppressed. However, when the imaging system 400 according to the present embodiment is used as a distance measuring device to be described later, since the information about the distance to the object is acquired by using the parallax of each image, the incident angle of the light from the lens device 3 is related. You need to leave the information. In that case, by arranging a positive lens as a field lens instead of the diffusing element 41 immediately before the field stop, it is possible to realize the same function as in the present embodiment while leaving the information on the incident angle.

  Next, a processing system in the imaging system 100 will be described. As described above, the characteristics of the image information output from the image pickup element 11 change depending on the configuration of the optical device 2 mounted on the image pickup apparatus 1. Therefore, it is desirable to realize a system for appropriately processing image information, no matter what optical device 2 is attached to the imaging device 1. Specifically, it is preferable that the optical device 2 includes a communication unit for transmitting and receiving information to and from the imaging device 1, and a recognition unit for recognizing the connection with the imaging device 1.

  FIG. 1A shows a case where the imaging device 1 has the processing unit 14 and the optical device 2 has the processing unit 27. The processing unit 14 has at least functions as a communication unit and a recognition unit. The processing unit 27 has at least a function as a communication unit (storage unit). The processing unit 14 and the processing unit 27 are electrically connected to each other when the optical device 2 is attached to the imaging device 1, and can transmit and receive information (signal) to and from each other. The processing unit 14 and the processing unit 27 can send and receive information via electrical contacts provided on the mount units of the imaging device 1 and the optical device 2, respectively. However, if no electrical contact is provided on each mount, wireless communication such as optical communication may be performed.

  The processing unit 27 stores unique information about the optical device 2, and the processing unit 14 recognizes that the optical device 2 is attached to the imaging device 1 by receiving the unique information. The unique information of the optical device 2 is, for example, an identifier (ID) such as an identification number for each of the lens array 21 and the filter array 22, or an identifier for a combination of the lens array 21 and the filter array 22. The processing unit 27 can recognize the type or individual of the optical device 2 based on the received unique information.

  In the image pickup system 100 according to the present embodiment, the image pickup apparatus 1 has a power supply and the optical apparatus 2 does not have a power supply. Therefore, the processing unit 14 of the image pickup apparatus 1 recognizes the mounting of the optical apparatus 2. Is desirable. In this case, the processing unit 27 has only a function as a storage unit (communication unit) that stores unique information. However, when the processing unit 14 and the processing unit 27 perform wireless communication, a configuration may be adopted in which a power source is provided for each of the imaging device 1 and the optical device 2 and each of them is individually recognized.

  The processing unit 14 also has a function as an image processing unit (processor), and processes the image information output from the image sensor 11 according to the received unique information. At this time, information about the lens array 21 in the optical device 2 (the number and arrangement of the lens portions) and information about the filter array 22 (transmission characteristics and arrangement of the filter) are associated with the unique information in advance, and the data table is used as a processing unit. It is desirable to record in 14 or an external device. Thereby, the processing unit 14 can recognize what kind of configuration (characteristic) the optical device 2 is attached by comparing the received unique information with the data table.

  In addition, if necessary, the information itself of the lens array 21 and the filter array 22 as described above is recorded in the processing unit 27 as unique information, and the processing unit 14 acquires the information from the processing unit 27. You may. However, in order to simplify and miniaturize the optical device 2, the information to be recorded in the processing unit 27 has the minimum information such as the identification number for discriminating the type of the optical device 2 and the individual as described above. It is desirable to make it.

  For example, when the filter array 22 is composed of bandpass filters, the processing unit 14 appropriately divides and reconstructs one image information output from the image sensor 11 based on the information of the lens array 21 and the filter array 22. Arrange. Accordingly, it is possible to generate a plurality of image information (multispectral image) for each wavelength band corresponding to the bandpass filter. At this time, one multispectral image may be generated by superimposing (recombining) a plurality of pieces of image information as necessary.

  The image information output from the image sensor 11 may be transmitted to an external device so that the image processing as described above is performed by the external device instead of the processing unit 14. In this case, in order to make the correspondence between the information of the optical device 2 and the image information easy to understand, it is preferable that the information stored in the processing unit 27 is added to the image information and then transmitted to the external device. Alternatively, the processing unit 27 may be provided as an external device outside the imaging device 1.

  Further, it is desirable that the lens device 3 includes a processing unit 34 similar to the processing unit 27 in the optical device 2. The processing unit 34 stores unique information about the lens device 3, and can transmit the unique information to the processing unit 14 in the imaging device 1 via the processing unit 27 in the optical device 2 or directly. The processing unit 14 can recognize the type or individual of the lens device 3 based on the unique information of the lens device 3. The processing unit 14 can process the image information output from the image sensor 11 according to the unique information of the lens device 3 and the unique information of at least one of the optical devices 2.

  Further, the adapter device 4 preferably includes a processing unit 46 similar to the processing unit 27 in the optical device 2. The processing unit 46 stores unique information about the adapter device 4, and can transmit the unique information to the processing unit 14 in the imaging device 1 via the processing unit 27 in the optical device 2 or directly. The processing unit 14 can recognize the type or individual of the lens device 3 based on the unique information of the adapter device 4. Further, the processing unit 14 can process the image information output from the image sensor 11 according to the unique information of at least one of the lens device 3, the adapter device 4, and the optical device 2. At this time, the influence on the image information due to the aberration generated in the lens device 3 may be corrected by using the unique information of the lens device 3.

  Next, the arrangement of the filters in the filter array 22 according to this embodiment will be described in detail. As shown in FIG. 1B, the filter F22 is arranged on the center (main optical axis AX0) of the filter array, but the other filters are arranged at positions apart from the main optical axis AX0. There is. That is, as compared with the lens portion corresponding to the filter F22, large decentering aberration occurs in the lens portions corresponding to the filters other than the filter F22.

  Further, in a general glass material used for the lens array 21, the rate of change of the refractive index (the amount of change of the refractive index per transmission wavelength width) increases as the wavelength of the transmitted light decreases. Therefore, as the center wavelength of the transmission wavelength range of the filter becomes shorter, it becomes more difficult to correct the aberration (chromatic aberration) of the lens portion corresponding to the shorter center wavelength. That is, when a filter corresponding to the short wavelength region is arranged at a position distant from the main optical axis AX0, the eccentric aberration is combined with the aberration caused by the transmission wavelength, so that good image information corresponding to the short wavelength region can be obtained. It will be difficult.

  Therefore, in the present embodiment, the filter having the shortest center wavelength in the transmission wavelength region of the filter array 22 is arranged at the position closest to the center of the filter array 22. Specifically, in FIG. 1B, the filter F22 arranged at the position closest to the center of the filter array 22 (position on the main optical axis AX0) is the filter having the shortest center wavelength in the transmission wavelength range. As a result, it is possible to reduce the decentering aberration of the lens portion corresponding to the short wavelength region, and it is possible to obtain good image information regardless of the transmission wavelength region of the filter.

  As described above, the filter array 22 may include filters whose center wavelengths in the transmission wavelength range are equal to each other. The filter having the shortest center wavelength in the transmission wavelength range (first filter) does not necessarily have to be arranged at the position closest to the center of the filter array 22. That is, the effect of the present invention can be obtained by arranging the first filter closer to the center of the filter array 22 than the second filter having a longer central wavelength in the transmission wavelength range than the first filter. Therefore, in at least three filters arranged in the first direction, the first filter may be arranged closer to the center of the filter array 22 than the second filter.

  For example, focusing on the filters F12, F22, and F32 arranged in the Y direction, the filter F22 may be the first filter, and the filter F12 or the filter F32 may be the second filter. Alternatively, focusing on the filters F22, F22, F23 arranged in the X direction, the filter F22 may be the first filter and the filter F21 or the filter F23 may be the second filter. Note that, for example, when the center wavelength of the transmission wavelength band of the filter F23 is the shortest, the filter F23 serves as the first filter, and thus the filter F13 or the filter F33 may be used as the second filter.

  In this embodiment, three filters are arranged in the X direction and three filters in the Y direction, but the same can be considered in a configuration in which four or more filters are arranged in at least one of the X direction and the Y direction. That is, paying attention to four or more filters arranged in one direction including the first filter and the second filter, and disposing the first filter closer to the center of the filter array 22 than the second filter. If so, the same effect can be obtained.

  In addition, it is desirable that the filter having the longest center wavelength in the transmission wavelength range is arranged in the filter array 22 at the farthest position from the center of the filter array 22. This is because it is easier to correct the aberration of the lens portion corresponding to the filter having the longest center wavelength in the transmission wavelength range as compared with the other lens portions, so that even if the lens portion is arranged at a position where the eccentric aberration is relatively large. This is because good image information can be obtained. As a result, a filter having a shorter central wavelength in the transmission wavelength range can be arranged closer to the center of the filter array 22, and good image information can be obtained regardless of the position of each filter. In this embodiment, the filter F11 arranged at the farthest position from the center of the filter array 22 is the filter having the longest center wavelength in the transmission wavelength range.

  Next, in order to explain the effect of the imaging system 100 according to the present embodiment, an imaging system according to a comparative example will be described. The image pickup system according to the comparative example has the same configuration as the image pickup system 100 according to the present embodiment except the arrangement of the filters. In this embodiment, the center wavelength of the transmission wavelength band of the filter F22 shown in FIG. 1B is the shortest, and the center wavelength of the transmission wavelength band of the filter F11 is the longest. On the other hand, in the comparative example, the center wavelength of the transmission wavelength band of the filter F11 shown in FIG. 1B is the shortest, and the center wavelength of the transmission wavelength band of the filter F22 is the longest.

  Here, the shortest transmission wavelength of the filter is λmin, the longest transmission wavelength is λmax, the transmission wavelength width is Δλ = λmax−λmin, and the center wavelength of the transmission wavelength band is λ. In this embodiment, λmin = 400 nm, λmax = 450 nm, Δλ = 50 nm, λ = 425 nm for the filter F22, and λmin = 700 nm, λmax = 750 nm, Δλ = 50 nm, λ = 725 nm for the filter F11. On the other hand, in the comparative example, λmin = 400 nm, λmax = 450 nm, Δλ = 50 nm, λ = 425 nm for the filter F11, and λmin = 700 nm, λmax = 750 nm, Δλ = 50 nm, λ = 725 nm for the filter F22.

  FIG. 2 is a diagram showing the MTF characteristics (MTF for the axial light flux) of the imaging systems according to the present example and the comparative example. As shown in FIG. 2, in the comparative example, the MTF for the filter F11 was reduced to nearly 0% at 30 lp / mm, and the resolving power in the short wavelength region was remarkably low. On the other hand, in this embodiment, the MTF for the filter F22 is 10 to 20% at 30 lp / mm, and the resolving power is significantly improved as compared with the comparative example. Although the MTF for the filter F11 is slightly lower than that of the comparative example, a sufficient resolution can be maintained.

  When the ratio of the difference between the transmission wavelength widths of two arbitrary filters in the filter array 22 to the transmission wavelength width of one of the two filters is 20% or less, that is, the transmission wavelength width of each filter is When they are close to each other, the effect of the present invention becomes large, which is preferable. Further, in order to acquire image information in a shorter wavelength range, it is desirable that the central wavelength of the transmission wavelength range of the first filter be 555 nm or less. In this case, although the difficulty of aberration correction becomes high, good image information can be obtained by adopting the configuration according to the present embodiment. Further, when the transmission wavelength width of each filter is common, aberration correction becomes more difficult as the value of Δλ / λ increases. Therefore, it is more preferable to arrange filters from the outer side to the inner side of the filter array 22 in the order of smaller Δλ / λ. preferable.

  As described above, according to the imaging system 100 according to the present embodiment, by disposing the filter corresponding to the short wavelength region in which aberration correction is difficult, outside the filter array 22, the good image information is obtained regardless of the filter. be able to.

[Modification]
Although the preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications and changes are possible within the scope of the gist thereof.

  Although the case where 3 × 3 filters are arranged has been described in the first embodiment, the number and arrangement of the filters are not limited to this. For example, 2 × 3 filters as shown in FIG. 3A, 4 × 3 filters as shown in FIG. 3B, and 4 × 4 filters as shown in FIG. 3C. A filter may be adopted. Also in this case, the same effect as that of the first embodiment can be obtained by disposing the first filter in the central region of the filter array 22 (region surrounded by the thick line shown in FIG. 3).

  It should be noted that, in the central region surrounded by the thick line shown in FIG. 3, it can be considered that decentering aberrations of substantially the same degree occur in consideration of the manufacturing error of each filter. As described above, when the filter array 22 has a plurality of central regions, it is desirable to arrange the filters in the central region in order from the filter having the shorter central wavelength in the transmission wavelength region. For example, when λ = 350 nm for the filter having the shortest center wavelength and λ = 400 nm for the filter having the second shortest center wavelength, the positions of F21 and F22 in FIG. 3A and 22 in FIG. , F23.

  In the above-described embodiments, the case where the lens section also serves as the aperture stop, that is, the case where the effective diameter of the lens section is determined by the lens section itself has been described, but the aperture stop may be provided as a separate member. In addition, in one image forming unit, when the lens unit includes a plurality of lenses or when the filter includes a plurality of filter elements, the lenses and the filter elements may be alternately arranged in the optical axis direction.

  Further, in the above-described embodiment, the optical axis of each lens unit is parallel to the main optical axis AX0, but the optical axis of each lens unit may be made non-parallel to the main optical axis AX0 if necessary. You may For example, in FIG. 1, the lens portion arranged farthest from the main optical axis AX0 has a large decentering aberration as compared with the other lens portions. Therefore, the optical axis AX11 of this lens portion is changed to the main optical axis AX0. The eccentric aberration may be corrected by inclining with respect to. Specifically, by tilting the optical axis AX11 so that the image side is located farther from the optical axis of the main optical axis AX0 than the object side, decentering aberration can be favorably corrected.

  Further, an image forming unit including a plurality of filters arranged so as to divide the pupil of the lens unit in the XY cross section may be adopted. At this time, the image pickup system can be used as a plenoptic camera by providing a minute lens array in a region corresponding to the image forming portion on the image pickup surface. According to this configuration, the light passing through the pupil of one lens unit is separated and enters the different pixels on the imaging surface, so that it is possible to acquire more image information.

  In the imaging system according to the above-described embodiment, the optical device 2 and the lens device 3 or the adapter device 4 are attachable to and detachable from each other. The generation may be suppressed. For example, the optical device 2 and the lens device 3 are integrally configured, or the optical device 2, the lens device 3, and the adapter device 4 are integrally configured, so that the optical device 2 and the lens device 3 can be attached to and detached from the imaging device 1. It may be a single lens device (accessory device). Alternatively, the optical device 2 and the adapter device 4 may be integrally configured to form one adapter device (accessory device) that is attachable to and detachable from the imaging device 1 and the lens device 3.

21 lens array 22 filter array F22 first filter F12 second filter

Claims (19)

A lens array having a plurality of lens portions each forming an image of an object;
A filter array having a plurality of filters arranged on the optical axis of the plurality of lens units,
The plurality of filters includes three or more filters arranged in a first direction,
The three or more filters include a first filter having the shortest center wavelength in the transmission wavelength range of the plurality of filters and a second filter having a center wavelength in the transmission wavelength range longer than that of the first filter. Including,
The optical system, wherein the first filter is arranged closer to the center of the filter array than the second filter.   The optical system according to claim 1, wherein the second filter is arranged at a position farthest from the center of the filter array in the first direction.   The optical system according to claim 1, wherein the lens portions corresponding to the first and second filters include optical surfaces of the same shape.   The optical system according to any one of claims 1 to 3, wherein all of the plurality of lens units include optical surfaces having the same shape.   The optical system according to any one of claims 1 to 4, wherein the first filter is arranged at a position closest to the center of the filter array.   The filter having the longest center wavelength in the transmission wavelength region among the plurality of filters is arranged at a position farthest from the center of the filter array. Optical system.   7. The ratio of the difference between the transmission wavelength widths of any two filters in the plurality of filters to the transmission wavelength width of one of the two filters is 20% or less. The optical system according to any one of 1.   8. The optical system according to claim 1, wherein the central wavelength of the transmission wavelength band of the first filter is 555 nm or less.   The optical system according to any one of claims 1 to 8, further comprising: an optical unit that guides light from the object to the plurality of lens units and is common to the plurality of lens units. .   The optical system according to claim 9, wherein the optical axis of the optical unit passes through the center of the filter array.   The optical system according to claim 9 or 10, wherein the first filter is arranged on an optical axis of the optical unit.   The optical system according to any one of claims 9 to 11, wherein the optical unit converts light from the object into parallel light.   10. The optical axis of the lens section arranged at the position farthest from the optical axis of the optical section among the plurality of lens sections is non-parallel to the optical axis of the optical section. 13. The optical system according to any one of items 1 to 12.   Among the plurality of lens units, the optical axis of the lens unit arranged at the position farthest from the optical axis of the optical unit is arranged so that the image side is farther from the optical axis of the optical unit than the object side. The optical system according to claim 13, wherein the optical system is inclined to.   An accessory device comprising the optical system according to any one of claims 1 to 14 and being attachable to and detachable from an imaging device.   The accessory device according to claim 15, further comprising a first mount portion for coupling with the imaging device.   The accessory device according to claim 16, wherein the first mount portion includes an electrical contact for electrically connecting to the imaging device.   An image pickup apparatus comprising: the optical system according to any one of claims 1 to 14; and an image pickup element that receives light from the optical system.   The imaging device according to claim 18, wherein the imaging element is common to the plurality of lens units.

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