Multi-lens optical system and imaging device

Abstract

To provide a single optical unit for turret-type or slide-type lens switching in an imaging device using multiple lenses, and a small, lightweight imaging device using the same.SOLUTION: An imaging device includes a plurality of prime lenses, prism means, an imaging element that converts a light beam acquired through the prism means into an image electrical signal and outputs it, and memory means that stores flange back values of the plurality of prime lenses, and the prism means and the imaging element are integrated into a single optical unit, and the optical unit is configured so as to be moved by drive means in response to switching between the plurality of prime lenses such that the predetermined flange back value of the lens stored in the memory means is set.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a single optical unit that is used in an imaging device that uses multiple lenses and involves turret-type or slide-type lens switching, and to a small, lightweight imaging device that uses the same. [Background technology]

[0002] Advances in solid-state imaging elements (sensors) and optical components used in video cameras, still cameras, and other devices have made it possible to create a wide variety of small, lightweight, high-resolution imaging devices. This has expanded the variety of imaging options available, from high-resolution wide-angle images to super-telephoto images, and imaging devices are now used for a wide variety of purposes, from general photography to in-vehicle use, medical use, production equipment, military use, commercial use, and broadcasting, as well as for image analysis, object detection, measurement and surveying, and surveillance and monitoring.

[0003] High-resolution imaging devices have become lighter and smaller thanks to the high integration of semiconductors and the miniaturization and high performance of component materials, but there are physical limitations to how light and compact a high-performance optical lens can be. In particular, telephoto lenses and zoom lenses, etc., have become smaller and lighter in size and weight than the imaging device itself, but the imaging device as a whole cannot be made lighter and lighter when these lenses are attached.

[0004] As an example of a technology for obtaining an enlarged image by electronic zoom (or digital zoom) technology using a prime lens (or fixed focus lens) without using a zoom lens, the present applicant has proposed Patent Document 1, etc. Although it is possible to obtain images with angles of view ranging from telephoto to wide angle by electronic zoom using multiple prime lenses such as telephoto, medium angle, and wide angle, it is common to provide each lens with a beam separation optical system that matches the values ​​specified for each lens or lens mount for optical processing of the beam focused by the lens, due to differences in flange back (FB) specific to each lens and lens mount.

[0005] In other words, in a light beam separation optical system equipped with multiple lenses and a multi-plate imaging element, it is necessary to design an optical unit that is compatible with each lens and use the lenses in combination with the optical unit, which is not in line with the goals of making the entire device smaller and lighter, and of improving the efficiency of design and manufacturing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2023-026270 A [Patent Document 2] Japanese Patent Application Publication No. 5-173225 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and has as its main object to provide an imaging device as described below. (1) An imaging device equipped with multiple lenses that can be made inexpensive, compact, and lightweight. (2) An imaging device that can be appropriately adapted to switching between multiple lenses of various types. (3) An imaging device that facilitates back focus and auto focus settings suitable for a wide variety of lenses. [Means for solving the problem]

[0008] In order to solve such problems and achieve the above-mentioned object, the imaging device of the present invention is an imaging device including a plurality of prime lenses, a prism means, an imaging element that converts the light beam acquired through the prism means into an image electrical signal and outputs it, and a memory means that stores the flange back values ​​of the plurality of prime lenses, wherein the prism means and the imaging element are integrated to form a single optical unit, and the optical unit is configured to be movable by a driving means so that, in response to switching between the plurality of prime lenses, the optical unit is set to a predetermined flange back value of the lens stored in the memory means.

[0009] In addition, in the imaging device of the present invention, the multiple prime lenses can be arranged on a lens switching means using a lens switching turret plate or slide plate, and lens switching can be performed by rotating the turret plate or moving the slide plate.

[0010] In the image pickup apparatus of the present invention, the flange back value of the lens stored in the storage means may be set in synchronization with lens switching by the lens switching means.

[0011] In the image pickup device of the present invention, the plurality of fixed focal lenses may be configured to have different focal lengths.

[0012] In the imaging device of the present invention, the prism means may be configured to separate the incident light beam into light beams having different wavelength bands or different phases.

[0013] In addition, in the imaging device of the present invention, an attachment switching means having a plurality of filters or conversion lenses corresponding to each of the plurality of fixed focal length lenses can be configured to be disposed on the incident light beam side of the lens switching means.

[0014] In the imaging device of the present invention, the optical unit may be configured to be movable so as to perform autofocusing using the driving means in accordance with distance measurement information acquired by a distance measurement sensor. Effect of the Invention

[0015] According to the present invention, an optical unit integrating an image sensor and an optical prism is constructed as a single unit, and this optical unit is movably controlled and set to a pre-stored flange back value in response to switching between multiple lenses. This makes it possible to obtain a single optical unit that is compatible with various types of lenses and lens mounts, resulting in a small, lightweight, and inexpensive image pickup device, while also providing freedom in the design and manufacture of the optical system.

[0016] Furthermore, by arranging a plurality of fixed focal length lenses with different focal lengths on a turret plate or slide plate and automatically setting the flange back value in synchronization with lens exchange, an imaging device with excellent operability can be constructed.

[0017] Furthermore, it is possible to configure autofocus by controlling the movement of the optical unit based on the distance measurement value obtained from the autofocus sensor, and autofocusing by driving the optical unit is possible. [Brief description of the drawings]

[0018] [Figure 1] 1 is an explanatory diagram showing an example of the configuration of an imaging device according to the present invention; [Diagram 2] FIG. 2 is an explanatory diagram showing a configuration example of an optical unit suitable for the present invention. [Diagram 3] FIG. 2 is an explanatory diagram showing an attachment switching means that can be used in the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, embodiments of an imaging device including a lens configuration and an optical system related to the present invention will be described in detail with reference to the drawings. Note that any explanatory diagrams and drawings described in the following examples are drawn as schematic or schematic diagrams for the purpose of explaining the present invention, and the actual dimensions and shapes are not particularly limited. Furthermore, the system configurations, block diagrams, dimensions, material shapes, relative positions thereof, and examples of use used in the examples are not intended to limit the technical scope of the invention to only those unless otherwise specified.

[0020] Fig. 1 is an explanatory diagram showing an example of the configuration of the optical system of an imaging device according to the present invention. In Fig. 1, multiple lenses, namely a wide lens 11, a middle lens 12, and a telephoto lens 13, are arranged on a lens switching means 10. This lens switching means 10 is composed of a turret plate or a slide plate. When multiple lenses are arranged on a turret plate, the turret plate is rotated to sequentially switch between each lens (wide, middle, and telephoto lenses in this embodiment) to perform a desired image acquisition operation. Also, when multiple lenses are arranged on a slide plate, the slide plate is slid to perform a lens switching operation.

[0021] The wide lens 11, the middle lens 12, and the telephoto lens 13 correspond to the lens mounts 21, 22, and 23 (hereinafter collectively referred to as the lens mount 20), respectively, and are arranged on the lens switching means 10. The lens switching means 10, which has a plurality of lenses, is attached in close contact with the imaging device body 1, and causes light beams acquired by switching the respective lenses to enter the imaging device 1. In FIG. 1, an optical unit 32 including a prism means 30 for separating light beams and image sensors 31R, 31G, and 31B (hereinafter collectively referred to as image sensor 31) is provided on the optical axis of the image light beams acquired by the middle lens 12. The prism means 30 in this embodiment includes, as an example, a three-plate light beam separating optical system for separating the image light beams into red (R), green (G), and blue (B) wavelength bands.

[0022] The incident light beam passes through a first prism 30B, which reflects the blue band light beam and transmits the other light beams (mainly green and red band light beams), and a blue image is extracted as an electrical signal (B output) from the imaging element 31B. The light beam transmitted through the first prism 30B enters a second prism 30R, which reflects the red band light beam and transmits the other light beams (mainly green band light beams). The red image reflected by the second prism 30R is extracted as an electrical signal (R output) from the imaging element 31R. The light beam transmitted through the second prism 30R transmits through a third prism 30G and is extracted as an electrical signal (G output) from the imaging element 31G.

[0023] The extracted R, G, and B image output signals are subjected to a series of image processing such as noise reduction, gain correction, detail, and gamma by a video processing means (not shown) that processes the image signals obtained by the respective imaging elements, and are then supplied to a matrix circuit (not shown) where they are formed into image signals such as component signals and composite signals, and are displayed on a monitor or screen. Note that in the prism means 30 of the embodiment, the incident light beams of the blue and red images are inverted once within the prism to obtain them, so the images are inverted from the green image. Therefore, the necessary image inversion processing is performed electrically at the image processing stage before use.

[0024] Here, the prism means 30 is formed by a first prism 30B, a second prism 30R, and a third prism 30G. The imaging elements 31R, 31B, and 31G that convert the R, G, and B image bands into electronic signals are integrated with the prism means 30 to form a single optical unit 32. In this optical unit 32, the optical path lengths to the imaging elements 31R, 31B, and 31G are formed to be substantially the same in the prism means. In addition, the prism means 30 and the imaging elements 31R, 31B, and 31G are configured to be movable back and forth in the optical axis direction (X-X') as a single optical unit 32. As the integration density and size of imaging elements improve and imaging elements become smaller, optical components such as prisms are also becoming smaller to fit the imaging elements, so this optical unit can be configured to be movable at a relatively high speed as a small and lightweight block.

[0025] The flange back (FB) value of each of the multiple lenses on the lens switching means 10 is specified for each lens mount, and each numerical value is stored in advance in a memory unit (ROM) 41 in the control means 40. In response to lens switching by the lens switching means 10, a switching signal detection unit 42 detects a signal indicating which lens is in an operational state, and the flange back value of the corresponding lens is set to a predetermined flange back value by moving the optical unit 32 by the optical unit driving means 43 via the control unit 40.

[0026] The control means 40 retrieves from a memory section (ROM) 41 a flange back value corresponding to the operating lens detected by a switching signal detection section 42, and sets the movement value of the optical unit 32 by an optical unit driving means 43 to the flange back value from the reference point of the lens mount, and these settings are controlled by a CPU 44 within the control means 40. Also, the optical unit driving means 43 may be any driving source such as a pulse motor as long as it is a driving source that performs accurate positioning over a small distance, but it can be realized by a linear stepping motor.

[0027] As described above, the blue image output (B output) from the imaging element 31B, the red image output (R output) from the imaging element 31R, and the green image output (G output) from the imaging element 31G are respectively output from the optical unit 32, and the output R, G, and B image outputs are displayed on a monitor or screen via a downstream image processing means, but the pixels of these imaging elements can also be used for autofocus (AF) detection. Autofocus detection is performed by the image plane phase difference method using some pixels of one of the imaging elements 30 (blue imaging element 31B in FIG. 1).

[0028] In this image plane phase difference method, the phase difference of the image is detected by using some of the multiple pixels horizontally and / or vertically spaced from the microlenses of the image sensor, and is sent as distance measurement information to an autofocus (AF) detection unit 50 to output an AF signal. The AF signal is sent to an AF control unit 51, which calculates the amount of displacement of the optical unit 32 as an AF control signal and operates to move the driving means 43 of the optical unit. The AF signal indicating distance measurement information uses some of the pixels of the image sensor and is extracted separately from the image information signal. AF detection using the image plane phase difference method allows for faster processing than the contrast AF detection method, and the optical unit 32 according to the present invention can be designed and manufactured to be relatively small and lightweight, making high-speed AF response possible.

[0029] Conventionally, autofocusing by moving the back focus has been used in some cases in film cameras (for example, Patent Document 2), but in film cameras, the need to move the film surface, which is the imaging plane, requires a complex mechanism, which has the disadvantage that it is difficult to achieve high-speed AF response.However, according to the present invention, by making the optical unit 32, which can be made small and lightweight, movable, high-speed response autofocusing is achieved by driving the back focus.

[0030] In this embodiment, good results are obtained by implementing the image plane phase difference method as the autofocus detection method, but it is not limited to the image plane phase difference method, and can be implemented using other phase difference methods or contrast methods. Also, instead of using the image sensor for autofocus detection, a reflecting mirror or prism may be inserted on the optical axis as shown in Figure 3 (described later) to provide a separate AF sensor to detect the focus distance measurement value.

[0031] By making the optical unit movable in this way, the back focus setting and AF setting associated with switching between multiple lenses can be configured as simultaneous functions, eliminating the need to perform back focus adjustment each time multiple lenses are switched as in the past, and enabling accurate autofocus to be maintained at all times, providing a multiple-lens imaging device with excellent operability.

[0032] Even with the same lens mount, the settings of the flange back value and autofocus value may change due to variations in component precision and aging during use. To adjust the focus and flange back of such a lens, a focus calibration chart or the like is used for each lens to confirm the focal point at the infinity point or zero point of the lens. If a deviation occurs due to calibration of the flange back value, the flange back value that serves as the focus reference can be corrected in the storage device (ROM) 41 according to the present invention, so that precise flange back and focus suitable for each lens can be obtained even when the lens is switched.

[0033] The optical unit 32 in Fig. 1 is an example of a three-plate sensor module including a light beam splitting prism means 30 that splits an incident light beam into R, G, and B, and image pickup elements 31R, 31G, and 31B, but this optical unit 32 can be compatible with any optical unit such as a single-plate, two-plate, three-plate, or four-plate sensor depending on the purpose of use of the imaging device, as long as it is an integrated unit of the prism means 30 and the image pickup element 31. Figs. 2(A), (B), and (C) show examples of prism configurations for a single-plate sensor, a two-plate sensor, and a four-plate sensor, respectively. In Fig. 2, the same members as in Fig. 1 are assigned the same numbers.

[0034] 2A is an optical unit for a single-chip sensor that integrates a single prism 61 and a single-chip image sensor 62. This image sensor 62 is composed of a single-chip CCD or CMOS visible light color or black and white image sensor. In the case of a single-chip color image sensor, video signals corresponding to each color of RGB are obtained by a Bayer array optical filter, which is then calculated and synthesized to form a color image, which is taken out as the C output.

[0035] The optical unit for a two-plate sensor in FIG. 2(B) is integrated with a first prism 63 and a first imaging element 64 for electrically converting an output image of the first prism, and a second prism 65 and a second imaging element 66 for electrically converting an output image of the second prism. Such a two-plate sensor optical unit can be used as an infrared / visible light imaging camera for day and night surveillance cameras and vehicle-mounted cameras by reflecting and separating an infrared wavelength band by the first prism 63, extracting an infrared image (C1 output) by the first imaging element 64, acquiring a visible wavelength band by the second prism, and extracting a color image (C2 output) by the second imaging element 66. It is also possible to separate P-polarized and S-polarized waves of visible light by the first prism 63, and extracting images of different phases of the P-polarized wave image (C1 output) and the S-polarized wave image (C2 output) from the same visible light color image for comparison and analysis.

[0036] The four-chip sensor optical unit in Fig. 2C is formed by integrating a first imaging element 68, a second imaging element 70, a third imaging element 72, and a fourth imaging element 74 arranged in a first prism 67, a second prism 69, a third prism 71, and a fourth prism 73, respectively. As an application of such a four-chip sensor optical unit, for example, a blue image output (B output), a red image output (R output), and two kinds of green outputs (G1 output) and (G2 output) can be extracted from each prism and imaging element. In this case, the two kinds of green outputs (G1 output and G2 output) are obtained by arranging the pixel pitches of the imaging elements so as to shift each other, thereby forming an image acquisition optical unit by so-called dual green pixel shifting.

[0037] 2 exemplarily shows combinations and application examples of optical units used for single-chip to multi-chip sensors, and if the prism means and the imaging element are integrally formed, application to various light beam separation optical systems that extract multiple light beams with different wavelength bands or light beams with different phases is possible. In addition, in such a movable optical unit method based on the present invention, by providing an optical unit that can be used with various sensors from single-chip sensors to multi-chip sensors, it becomes easier to design and manufacture a wide variety of imaging devices that can be adapted to multiple lenses, and this configuration also contributes to the efficiency of designing and manufacturing imaging devices.

[0038] 3 shows an embodiment in which various attachment switching means 80 are provided in parallel with the lens switching means 10 on the incident light beam side of the lens switching means 10. In FIG. 3, the same members as those in FIG. 1 are given the same numbers. This attachment switching means 80 can be operated independently of the lens switching means 10. An auxiliary optical system (e.g., a first optical filter 81, a second optical filter 82, and a third optical filter 83, etc.) that provides variation to image capture, such as a filter or a conversion lens, is attached to the attachment switching means 80 for use. As the filter, an ND filter, a color filter, a polarizing filter, a bandpass filter, etc. can be used.

[0039] In addition to switching between optical filters, it is also possible to switch between a number of attachments, such as teleconversion and wide conversion lenses, and extension lenses for adjusting magnification and angle of view. When using a conversion lens, the specified flange back value differs, so it is necessary to calibrate the lens as described above, correct the flange back value, and set a flange back value that is suitable for switching the conversion lens. Of course, if a filter or conversion lens is not required above the attachment switching means 80, a space is provided.

[0040] This attachment switching means 80 has the same shape as the turret plate or slide plate of the multiple lens switching means 10, and the filters and conversion lenses are attached by means of a screw mount or the like on the attachment switching means 80. The attachment switching means 80 can be switched manually or in synchronization with the lens switching means 10, and the lens switching means 10 and the attachment switching means 80 are arranged so as to match the optical axis of a predetermined lens.

[0041] 3 shows an example in which autofocus detection is obtained not by the imaging element of the optical unit 32 but by an AF sensor system provided separately. An AF reflecting prism 91 is inserted on the incident optical axis of the imaging device 1, and a focus distance measurement value is detected by an AF sensor 92. This AF distance measurement method can use a known contrast method or phase difference method. The detected focus distance measurement value is used to move the optical unit 32 by the optical unit driving means 43 via the AF control means 51, thereby performing autofocus control.

[0042] The flange back value of each lens varies widely depending on the type of camera: still camera, smartphone camera, video camera, cine camera (industrial camera). For example, the flange back of the C mount, which is widely used in industrial surveillance cameras and medical cameras, is 17.526 mm, while the flange back value for still cameras, known as short flange back, varies from 16 mm to 20 mm, and lenses with flange backs of 100 mm or more are also available for professional cameras such as those used for broadcasting.

[0043] Currently, there are more than several dozen different flange backs and back focuses set for the reasons that by setting the flange back short, it is possible to design a brighter and smaller wide-angle lens, and it is possible to make the imaging device smaller, lighter, and more powerful. In other words, the flange backs and back focuses set for each mount, manufacturer, and lens product are different and not compatible with each other. Furthermore, various lens adapters are provided to make these lenses compatible so that several lenses can be used with a common lens mount, but the use of such lens adapters can cause a state in which the focal point at the infinity point is different (over infinity) or a state in which the accurate flange back and back focus values ​​cannot be maintained.

[0044] In the present invention, by making the optical unit 32, in which the imaging element and the prism are integrated, movable, the optical unit 32 can move at high speed and set the flange back value to a preset value even for the wide variety of lenses as described above in response to lens switching by the multiple lens switching means 10. Therefore, it is not necessary to provide an optical unit for each lens, and a single optical unit can be formed, making it possible to provide an imaging device that is smaller, lighter, and easier to design and manufacture. [Industrial Applicability]

[0045] According to the multiple lens optical system and the imaging device using the same of the present invention, it is not necessary to provide multiple optical units that are compatible with multiple lenses, but a single optical unit can be configured, and it can be compatible with various lenses. Therefore, it can be used in a wide range of applications such as surveillance cameras, vehicle-mounted cameras, weather cameras, aircraft cameras, and endoscope cameras, and it can be used in a wide range of industrial applications such as business, consumer, industrial, and military. [Explanation of symbols]

[0046] 1 Imaging device (main body) 10 Lens switching means (turret plate or slide plate) 11 Wide-angle lens 12 Mid-angle lens 13 Telephoto lens 20 Lens mount 21 Wide lens mount 22 Mid-lens mount 23 Telephoto lens mount 30 Prism Means 31 Image sensor 32 Optical unit 40 Control Means 41 Memory unit (ROM) 42 Switching signal detector 43 Optical unit driving means 44 CPU 50 AF detection section 51 AF control section 80 Attachment switching means 91 AF reflector prism 92 AF sensor

Claims

1. An imaging device including a plurality of fixed focal length lenses, a prism means, an imaging element that converts a light beam acquired through the prism means into an image electrical signal and outputs the signal, and a storage means that stores flange back values ​​of the plurality of fixed focal length lenses, an imaging device characterized in that the prism means and the image sensor are integrated into a single optical unit, and the optical unit is configured to be movable by a driving means in response to switching between the multiple fixed focal length lenses so that the optical unit is set to a predetermined flange back value of the lens stored in the memory means.

2. 2. The imaging device according to claim 1, wherein the plurality of fixed focal lenses are arranged on a lens switching means using a turret plate or a slide plate for switching lenses, and the lenses are switched by rotating the turret plate or moving the slide plate.

3. 3. The image pickup apparatus according to claim 2, wherein the flange focal length value of the lens stored in the memory means is set in synchronization with lens switching by the lens switching means.

4. 2. The image pickup apparatus according to claim 1, wherein the plurality of fixed focal lenses have different focal lengths.

5. 2. The imaging device according to claim 1, wherein said prism means separates the incident light beam into light beams of different wavelength bands or different phases.

6. 2. The imaging device according to claim 1, wherein an attachment switching means having a plurality of filters or conversion lenses corresponding to the plurality of fixed focal length lenses is disposed on the incident light beam side of the lens switching means.

7. 2. The image pickup apparatus according to claim 1, wherein said optical unit is movable so as to perform autofocusing by using said driving means in accordance with distance measurement information obtained by a distance measurement sensor.

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