Optical module and imaging device

Abstract

Provided is an optical module wherein a first prism is composed of a dichroic pentaprism that receives incident light on an incident surface and has five sides, at least a part of the incident light is reflected twice on a first side surface and a second side surface in the first prism, is emitted from an emission surface of the first prism, and is incident on a first imaging element, the first imaging element converts the incident light flux into an electric signal and extracts the electric signal as a first optical image, the incident light on the incident surface and the emission light from the emission surface are configured to be perpendicular to each other, a second prism receives transmitted light which is the other at least part of the incident light and is transmitted through a selected side surface of the first side surface or the second side surface in the first prism, and emitted from an emission surface of the second prism and made incident on a second imaging element, the second imaging element is configured to convert the incident light flux into an electric signal and extract the electric signal as a second optical image, and the first prism, the first imaging element, the second prism, and the second imaging element are integrated and arranged at the tip of a search scope.

Description

Optical module and imaging device

[0001] The present invention relates to an optical module and an imaging device.

[0002] Patent Document 1 describes "a dichroic prism assembly having four or five channels, an endoscope using the same, and a medical imaging system." Patent Document 2 describes "a four-plate camera using a four-color separation prism and four image sensors in the camera head of an endoscope." Patent Document 3 describes "the imaging unit 2 comprises a lens unit 20, a first prism 21, a second prism 22, and a visible light reflective film 27 (an example of a reflective film). The imaging unit 2 further comprises a first trimming filter 23, an infrared light blocking film 28, a first image sensor 24, and a first circuit board 32." [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Unexamined Patent Publication No. 2021-99522 [Patent Document 2] Japanese Unexamined Patent Publication No. 2021-013753 [Patent Document 3] Japanese Unexamined Patent Publication No. 2022-60992 General disclosure

[0003] In the first aspect, the optical module is an imaging optical module that acquires a plurality of optical images using a plurality of imaging elements. The optical module includes a first prism and a second prism disposed in close contact with the first prism. The first prism receives incident light on an incident surface and is composed of a dichroic pentaprism having five sides. At least a part of the incident light is reflected twice on the first side surface and the second side surface within the first prism, exits from the exit surface of the first prism, and enters the first imaging element. The first imaging element converts the incident light beam into an electrical signal and extracts it as a first optical image. The incident light on the incident surface and the exit light on the exit surface are configured to be perpendicular to each other. The second prism receives transmitted light, which is at least another part of the incident light, that has passed through either the first side surface or the second side surface within the first prism, exits from the exit surface of the second prism, and enters the second imaging element. The second imaging element is configured to convert the incident light beam into an electrical signal and extract it as a second optical image. The main feature is that the first prism, the first imaging element, the second prism, and the second imaging element are integrated.

[0004] Also, the optical module is the second prism disposed in close contact with the first side surface within the first prism. The second prism has a second prism beam separation surface that further reflects and transmits the transmitted light that has passed through the first side surface of the first prism. The reflected light reflected by the beam separation surface enters the second element. The second imaging element converts the second optical image into an electrical signal and outputs it. The transmitted light that has passed through the second prism beam separation surface enters the third imaging element. The third imaging element is configured to convert the third optical image into an electrical signal and output it. It is also possible to configure the module to acquire three optical images consisting of the first optical image, the second optical image, and the third optical image.

[0005] Furthermore, the optical module is configured to acquire four optical images consisting of the first optical image, the second optical image, the third optical image, and the fourth optical image. The third prism is incident on a second image sensor, and the second image sensor converts the second optical image into an electrical signal and outputs it. The second prism has a second prism beam separation surface that further reflects and transmits the transmitted light that has passed through the first side surface of the first prism. The reflected light reflected by the second prism beam separation surface is incident on a third image sensor, and the third image sensor converts the third optical image into an electrical signal and outputs it. The transmitted light that has passed through the second prism beam separation surface is incident on a fourth image sensor, and the fourth image sensor converts the fourth optical image into an electrical signal and outputs it.

[0006] Furthermore, the optical module may also be configured such that the first optical image and the second optical image in claim 1, the third optical image in claim 2, and the fourth optical image in claim 3 are images in the visible light wavelength band, the infrared light wavelength band, or the ultraviolet light wavelength band.

[0007] Furthermore, the optical module can also be configured to output optical images in which any two of the first, second, third, and fourth optical images have a central bandwidth of wavelengths of 415 nm and 540 nm.

[0008] Furthermore, the optical module can also be configured such that it includes a lens, a circuit board for an image sensor, and a prism for side-viewing, and is integrated and positioned at the tip of the search scope.

[0009] Furthermore, an imaging device to which the above optical module is applied may also be configured such that the image processing means for the first optical image and the second optical image in claim 1, the third optical image in claim 2, and the fourth optical image in claim 3 includes memory means for storing the output signals of any of the image sensors, and the memory means is configured to read out the image so that it matches the reproduced image of the other image sensor when the field of view of the reproduced image differs due to the size of the image sensor, and to read out the image in a way that converts the reproduced image to an upright image if it is an inverted image.

[0010] This is an explanatory diagram showing a two-plate configuration example of the optical module according to Example 1. This is an explanatory diagram showing a modified configuration example of the two-plate optical module according to Example 1. This is an explanatory diagram showing another modified configuration example of the two-plate optical module according to Example 1. This is an explanatory diagram showing a three-plate configuration example of the optical module according to Example 2. This is an explanatory diagram showing a four-plate configuration example of the optical module according to Example 3. This is an explanatory diagram of the image processing circuit configuration block for the optical module according to this embodiment. An endoscope imaging device 100 is schematically shown.

[0011] Hereinafter, embodiments of the optical module and imaging device to which

[0012] The optical module positioned at the tip of the exploration scope is configured with an elongated shape along its longitudinal direction. This is primarily intended for insertion into internal organs, such as in medical endoscopy, and the optical module is configured to be as compact as possible in cross-section compared to its longitudinal length. However, industrial endoscopes, not just medical endoscopes, do not necessarily have to be elongated along their longitudinal direction. For pipe exploration, observation of the inside of machinery or vehicles, and imaging, it is desirable to have a shape configuration that is appropriate to the specific exploration purpose and the orientation of the object or observation surface.

[0013] Figure 1 is an explanatory diagram showing an example of a two-plate optical module (composed of two image sensors, also referred to as a two-channel module) according to Embodiment 1. Figure 1 shows a cross-section of the optical module 1. This optical module 1 is a two-plate optical module composed of at least a first prism 11, a second prism 12, a first image sensor 13, and a second image sensor 14.

[0014] The first prism 11 is a dichroic pentaprism having five sides (five faces and corners). Here, this pentaprism is a pentagonal prism, and each of its faces is a plane, and it is not a pentadach prism that forms a roof called a roof face.

[0015] A lens joint 17 for attaching a lens 16 is positioned on the incident surface 15 of the first prism 11. This lens joint 17 may be directly bonded to the prism, or it may be configured as a lens mount joint for interchangeable lenses. The light beam acquired by the lens 16 enters the incident surface 15 and is reflected by the first side surface 18 of the first prism. This first side surface 18 is made of an aluminum coating or silver coating so that the entire amount of the incident light beam is reflected. A portion of the light beam reflected by the first side surface 18 is further reflected by the second side surface 19, and the remaining portion of the light beam is transmitted. The light beam that has been reflected twice within the first prism 11 exits from the exit surface 20 of the first prism 11 and enters the first image sensor 13.

[0016] Here, the incident light beam to the first prism is incident perpendicular to the incident surface 15, and the exit light beam from the first prism is emitted from the exit surface 20 which is at a right angle to the incident surface 15. The first side surface 18 and the second side surface 19 of the first prism are positioned such that the incident light beam and the exit light beam are perpendicular to each other.

[0017] The first image sensor 13 converts the incident light beam into an electrical signal and extracts it as a first optical image. This first optical image is obtained as an erect image because the incident light beam is reflected twice within the first prism 11. The first image sensor 13 is located on a circuit board 25 which includes part of the image processing circuit.

[0018] The second prism 12 is positioned in close contact with the second side surface 19 of the first prism 11. For example, the first prism 11 and the second prism 12 are positioned in close contact by bonding their peripheral edges with adhesive. Not only the peripheral edges, but the entire surface, or any region, may be bonded with adhesive. The same method may be used for bonding other optical components together. It should be noted that when optical components are bonded together, there are no other optical components interposed between them. The second side surface 19 separates and reflects a portion of the incident light beam reflected by the first side surface 18 at a predetermined wavelength or wavelength band, and transmits the remaining incident light beam to enter the second prism 12. This second side surface 19 is composed of a wavelength separation film that reflects a desired wavelength or wavelength band depending on the application. Such a wavelength separation film obtains reflection and transmission properties by layering dielectric films or metal thin films having specific reflection characteristics. The reflection and transmittance ratio of this reflection separation film is usually 50:50, but is not limited to this.

[0019] The transmitted light that passes through the second side surface 19 of the first prism 11 (which is also the incident surface of the second prism 12) and enters the second prism 12 exits from the exit surface 21 of the second prism 12 and enters the second image sensor 14. This second image sensor 14 is arranged on a circuit board 26 which includes part of the image processing circuit.

[0020] The second image sensor 14 converts the incident light beam into an electrical signal and extracts it as a second optical image. This second optical image is obtained by reflecting the incident light beam once within the first prism 11, so it is obtained as an inverted image. To obtain this inverted second optical image as an upright image, known methods such as reverse reading from the pixel memory can be used in the image processing stage after the conversion to an electrical signal.

[0021] In this embodiment 1, the optical path lengths from the reference position of the lens joint 17 to the first image sensor 13 and the second image sensor 14 are both predetermined optical path lengths set for each lens. When a C-mount or CS-mount is used as the lens mount, the lengths are configured to be the same based on the flange back length set for the lens, with the rear end of the lens as the reference position, depending on the back focus length or the type of lens.

[0022] Furthermore, in Figure 1, a side-viewing prism 27 is positioned on the incident light side of the lens 16. This side-viewing prism 27 can be composed of a wedge prism, a triangular or trapezoidal prism, etc., for acquiring images of walls and sides for use in endoscopes or tubular internal inspections. The optical module 1 includes a first prism 11, a second prism 12, a first image sensor 13, and a second image sensor 14, which are integrated together. Integration includes bonding adjacent optical components of the optical module 1 with adhesive, attaching the optical components to components such as housings, and combinations thereof. The optical module 1 may also include and integrate the side-viewing prism 27, lens 16, circuit boards 25 and 26.

[0023] Figure 2 is an explanatory diagram showing a modified two-plate configuration example of the optical module of Embodiment 1. The same parts as in Figure 1 are numbered the same. The difference from Figure 1 is that while the second optical image in Figure 1 is acquired as an inverted image, in the optical module 2 of Figure 2, the second optical image can be acquired as an upright image. The function and configuration of the first prism 11 are the same as in Figure 1, and the fact that the second prism 22 is positioned in close contact with the second side surface of the first prism 11 is also the same.

[0024] In Figure 2, the second prism 22 has a second prism side surface 23 inside the second prism 22, and the light beam incident from the incident surface 19 of the second prism 22 (which is also the second side surface of the first prism 11) is reflected by the second prism side surface 23. The light beam reflected by the second prism side surface 23 exits from the second prism exit surface 24 and is incident on the second image sensor 14. The light beam incident on the second image sensor 14 is converted electrically by the second image sensor 14 and electrically extracted as a second optical image. Here, the second optical image is acquired as an erect image because it is reflected twice by the first side surface 18 of the first prism and the second prism side surface 23.

[0025] In Figure 2, the optical path lengths from the lens joint to the first image sensor 13 and the second image sensor 14 are the same as in Figure 1, both being predetermined optical path lengths specified for the lens. In the case of a lens mount, they are configured to be the same length as the back focus length or flange back length from the mount reference plane.

[0026] In Figure 2, the second prism 22 is made up of a triangular prism with a triangular cross-section, but any prism shape is acceptable as long as the optical path length to the first image sensor 13 and the second image sensor 14 is maintained at a predetermined optical path length (back focus length or flange back length).

[0027] Furthermore, in Figure 2, as in Figure 1, a side-viewing prism 28 is positioned on the incident light side of the lens 16. This side-viewing prism 28 is a prism for acquiring images of walls and sides, and can be made up of a wedge prism, triangular prism, or trapezoidal prism. While the side-viewing prism 27 in Figure 1 reflects the incident light image twice to acquire an upright image which is then incident on the lens 16, the side-viewing prism 28 reflects the incident light image once using a triangular prism which is then incident on the lens 16 as an inverted image. The optical module may include these side-viewing prisms 28 and be integrated into a single unit.

[0028] Figure 3 is an explanatory diagram showing another modified configuration example of the two-plate optical module of Embodiment 1. The same numbering is used for the same components as in Figure 1. The difference between Figures 1 and 2 and Figure 3 is that in Figures 1 and 2, the second prism is positioned in close contact with the second side surface 19 of the first prism 11, whereas in the configuration of Figure 3, the second prism 31 is positioned in close contact with the first side surface 18 of the first prism 11.

[0029] The first side surface 18 of the first prism 11 is composed of a wavelength-separating film that separates and reflects a portion of the incident light beam at a predetermined wavelength or wavelength band, while transmitting the remaining incident light beam to the second prism 31. Similar to the second reflective film in Figure 1, this wavelength-separating film achieves its reflection and transmission properties by layering dielectric films or thin metal films with specific reflection characteristics. Furthermore, the second side surface 19 is coated with aluminum or silver so that the entire incident light beam is reflected.

[0030] The light beam that passes through the first side surface 18 of the first prism (which is also the incident surface of the second prism) and enters the second prism 31 exits from the exit surface 32 of the second prism and enters the second image sensor 14. The light beam that enters the second image sensor 14 is converted electrically by the second image sensor 14 and is electrically extracted as a second optical image. The second optical image here is the same as the incident light beam of the first prism and is acquired as an erect image.

[0031] In Figure 3, the optical path lengths from the lens joint to the first image sensor 13 and the second image sensor 14 are configured to be the same as in Figures 1 and 2, with both having the same optical path length determined by the lens, or by the back focus length or flange back length.

[0032] The optical module configurations shown in Figures 1, 2, and 3 above provide a two-plate optical module that uses a first prism 11, which is a pentaprism, as a base, and allows for the selection of one of the two sides of the first prism depending on the application and purpose of use, thereby obtaining different shapes for the optical module.

[0033] This type of optical prism configuration is suitable for remote observation in extremely confined spaces because its shape can be appropriately deformed and selected, whether it is long or short in the longitudinal direction, and because it can be integrated with multiple image sensors and placed at the tip of a search scope, and the signal is extracted as an electrical signal rather than an optical fiber as a chip-on-chip type as described below.

[0034] To integrate the optical module, image sensors such as CMOS (Complementary Metal Oxide Semiconductor) or CCD (Charge Coupled Device), and some of the image processing means, are integrated using a stacked chip-on-chip structure and arranged on their respective circuit boards, and the captured optical image is output as an electrical signal. The output electrical signal is extracted via lead wires, making remote observation easy. Extracting optical images using optical fibers presents problems such as limitations on cable length due to optical attenuation and flexibility limitations, as well as maintenance and hygiene issues. However, by electrically extracting the signal using lead wires instead of optical fibers, miniaturization can be achieved with ultra-fine lead wires of a few millimeters or less, and various issues such as flexibility and signal attenuation loss can be solved.

[0035] For example, if we calculate the dimensions of the optical module in the configuration of Figure 3 using only the prism component excluding the image sensor and circuit board, the length L in the longitudinal direction is determined by the optical path length specified for the lens. If we assume that a lens with an optical path length of 12.168 mm is used, then L can be 12.168 mm and the height H can be approximately 4.44 mm. Under similar conditions, the prism in Figure 1 can be configured with a length L of 6.92 mm and a height H of 6.8 mm, and the prism in Figure 2 can be configured with a length L of 5.47 mm and a height H of 6.8 mm. In other words, the optical module in Figure 3 is long in the longitudinal direction (L) and thin in the thickness direction (H), whereas the configurations in Figures 1 and 2 are approximately half the length in the longitudinal direction (L) and about 50% taller in the height direction (H) compared to Figure 1.

[0036] This two-plate (two-image sensor) optical prism configuration allows for the extraction of two optical images as a first optical image and a second optical image. The wavelength or wavelength band of these optical images is extracted by reflecting and separating one of the visible light wavelength band, infrared light wavelength band, or ultraviolet light wavelength band based on the wavelength characteristics of the side (reflective surface) 18 or 19. For example, it can be applied to a wide range of imaging devices such as dermatoscopes that extract a near-infrared light image as the first optical image and a visible light (color) image as the second optical image, day and night surveillance cameras, and surface temperature detection cameras for objects and the human body.

[0037] In Embodiment 1, the first optical image from the first image sensor 13 and the second optical image from the second image sensor 14 may be captured simultaneously. Here, "captured simultaneously" includes cases where the exposure time of the first image sensor 13 and the exposure time of the second image sensor 14 coincide, or where a portion of their exposure times overlap. Furthermore, coaxial images, that is, images with the same center position in the imaging range, are incident on the first image sensor 13 and the second image sensor 14. Therefore, images of the same subject can be captured on both the first image sensor 13 and the second image sensor 14.

[0038] In this embodiment, variations and options are available in the shape of the optical module, and it is possible to make it smaller and lighter, thus enabling various applications adapted to extremely confined spaces. For observing tubular objects, the elongated shape shown in Figure 3 is applied, and for structures that cannot be extended in the longitudinal direction, the shape shown in Figure 1 or Figure 2 can be used. This makes it possible to incorporate it not only into search scopes but also into measuring devices with installation space limitations, enabling a wide range of applications to structures, flying objects, precision instruments, and more.

[0039] Figure 4 is an explanatory diagram showing an example configuration of a three-plate optical module 4 according to Embodiment 2. While Figures 1, 2, and 3 show a two-plate system that acquires two optical images, Embodiment 2 in Figure 4 has a three-plate configuration that acquires three optical images: a first optical image, a second optical image, and a third optical image. The optical module 4 in Embodiment 2 is composed of three prisms: a first prism 11, a second prism 41, and a third prism 42. The first prism 11 is the same as the first prism 11 in Embodiment 1, and in Figure 4, the same components as in Figure 3 are given the same numbers.

[0040] The first prism 11 is composed of a dichroic pentaprism with five sides, and the light beam incident on the first prism 11 is reflected twice by the first side surface 18 and the second side surface 19 inside the first prism 11, and then incident on the first image sensor 13, outputting the first optical image as an electrical signal, as in Figure 1. The second prism 41 is positioned in close contact with the first side surface 18 of the first prism. The first side surface 18 of the first prism is composed of a wavelength-separating film that separates and reflects a portion of the incident light beam at a predetermined wavelength or wavelength band, and transmits the remaining incident light beam to the second prism 41. The configuration of such a wavelength-separating film is similar to the first reflective film in Figure 3 above, and the reflection and transmission characteristics are obtained by layering dielectric films or thin metal films having specific reflection characteristics.

[0041] The light beam that passes through the first side surface 18 of the first prism 11 (which is also the incident surface of the second prism 41) and enters the second prism 41 has a portion of the incident light reflected at a right angle by the light beam separation surface 43 of the second prism 41, and enters the second image sensor 45 via the auxiliary prism 44. Here, the auxiliary prism 44 is an auxiliary prism used to adjust the optical path length of the incident light beam to a predetermined optical path length.

[0042] The light beam separation surface 43 of the second prism 41 is angled 45 degrees with respect to the incident light beam and is composed of a wavelength separation film that separates and reflects a portion of the incident light beam at a predetermined wavelength or wavelength band, while transmitting the remaining incident light beam to the third prism 42. The second image sensor 45 converts the incident light beam into an electrical signal and extracts it as a second optical image. This second optical image is acquired as an inverted image, and, similar to the second optical image in Figure 1, is extracted as an upright image in subsequent image processing.

[0043] The transmitted light that passes through the reflective surface of the second prism 41 (which is also the incident surface of the third prism) and enters the third prism 42 exits from the exit surface 46 of the third prism 42 and enters the third image sensor 47. The third image sensor 47 converts the incident light beam into an electrical signal and outputs it as a third optical image (erect image). The image sensors 48 and 49 are arranged on circuit boards 48 and 49, respectively, which include part of the image processing circuit, as in Embodiment 1.

[0044] The first optical image, the second optical image, and the third optical image obtained by the optical module 4 are, as in the first embodiment, separated and extracted by reflecting the wavelength or wavelength band of the optical image according to the wavelength characteristics of the first side surface 18 of the first prism 11 and the reflecting surface 43 of the second prism 41, either in the visible light wavelength band, the infrared light wavelength band, or the ultraviolet light wavelength band. In the three-plate type of the second embodiment, since three different wavelengths or wavelength bands can be extracted, for example, three optical images of 415 nm (blue light image), 540 nm (green light image), and a visible light image can be extracted and applied to narrow-band light observation (NBI; Narrow Band Imaging) of a medical exploration scope or the like.

[0045] In the second embodiment, the first optical image of the first imaging element 13, the second optical image of the second imaging element 45, and the third optical image of the third imaging element 47 may be simultaneously extracted. Here, being simultaneously extracted includes cases where the exposure times of the first imaging element 13, the second imaging element 45, and the third imaging element 47 coincide, or cases where a part of their exposure times overlaps. Also, coaxial images, that is, images with the same central position of the imaging range, are incident on the first imaging element 13, the second imaging element 45, and the third imaging element 47. Therefore, images of the same subject can be captured by each of the first imaging element 13, the second imaging element 45, and the third imaging element 47.

[0046] FIG. 5 is an explanatory diagram showing a configuration example of a four-plate type optical module 5 according to the third embodiment. In the third embodiment, it is configured to obtain four optical images: the first optical image, the second optical image, the third optical image, and the fourth optical image. The optical module 5 in the third embodiment is composed of four prisms by further adding a fourth prism 51 to the first prism 11, the second prism 41, and the third prism 42 in the second embodiment. The first prism 11, the second prism 41, and the third prism ings 42 are the same as those in the second embodiment. Also, the configuration of extracting the first optical image with the first prism 11 composed of a pentaprism that incident light beams are incident on, the second optical image with the second prism 41, and the third optical image with the third prism 42 is the same as that in the second embodiment. In FIG. 5, the same members as those in FIG. 4 are labeled with the same numbers.

[0047] In Example 3, the fourth prism 51 is disposed in close contact with the second side surface 19 of the first prism 11, and the transmitted light transmitted through the second side surface 19 of the first prism 11 is emitted from the emission surface 52 of the fourth prism 51 and made incident on the fourth image pickup device 53. The fourth image pickup device 53 converts the incident light beam into an electric signal and outputs it as a fourth optical image (inverted image). Since this fourth optical image is acquired as an inverted image, it is taken out as an upright image in the subsequent image processing, similar to the second optical image in FIG. 1. The first image pickup device 13, the second image pickup device 45, the third image pickup device 47, and the fourth image pickup device 53 are respectively disposed on circuit boards 25, 48, 49, and 50 including a part of an image processing circuit.

[0048] The first optical image, the second optical image, the third optical image, and the fourth optical image acquired by the optical module 5 are output as electric signals, and the optical images are, as in Example 1 and Example 2, the wavelength or wavelength band of the optical image is the visible light wavelength band, the infrared light wavelength band, or the ultraviolet light wavelength band. Any of them is separated by reflection according to the wavelength characteristics of the first side surface 18 of the first prism 11, the second side surface 19 of the first prism 11, and the reflection surface 43 of the second prism 41 and taken out.

[0049] In the four-plate type of Example 3, since four different wavelengths or wavelength bands can be taken out, it can be applied to a multispectral camera and developed for various applications. Exemplarily, the first optical image, the second optical image, the third optical image, and the fourth optical image are taken out as four optical images composed of the wavelength bands of red light (R), green light (G), blue light (B), and infrared light, and the R, G, and B images are synthesized to obtain a high-definition color image. By combining with the infrared light image, a wider range of applications such as a day-and-night surveillance camera, an endoscope, a foreign object detection camera, and a biological surface temperature measurement camera become possible.

[0050] In Embodiment 3, the first optical image from the first image sensor 13, the second optical image from the second image sensor 45, the third optical image from the third image sensor 47, and the fourth optical image from the fourth image sensor 54 may be captured simultaneously. Here, "captured simultaneously" includes cases where the exposure times of the first image sensor 13, the second image sensor 45, the third image sensor 47, and the fourth image sensor 54 coincide, or where a portion of their exposure times overlap. Furthermore, coaxial images, that is, images with the same center position in the imaging range, are incident on the first image sensor 13, the second image sensor 45, the third image sensor 47, and the fourth image sensor 54. Therefore, images of the same subject can be captured on each of the first image sensor 13, the second image sensor 45, the third image sensor 47, and the fourth image sensor 54.

[0051] In this embodiment, the optical module is assumed to be an integrated unit containing at least a plurality of light beam separation optical prisms and an image sensor for acquiring the respective optical image, and is positioned at the tip of a search scope or the like. However, it may also be configured to include an optical system such as a circuit board on which the image sensor is mounted, a lens for acquiring the optical image, and a side-oblique viewing prism (triangular prism or edge prism) positioned at the tip of the lens for acquiring images of walls or sides.

[0052] Furthermore, when applying this embodiment to narrow-band imaging (NBI), where two or more optical images obtained are extracted as specific wavelengths, for example, in a medical optical module that extracts 415 nm (blue light image) and 540 nm (green light image), it is desirable to provide an optical filter that transmits these wavelengths between the prism emission surface and the image sensor. Moreover, it is possible to form an integrated optical module that includes a filter that cuts out bandwidths other than the wavelength band to be extracted, not limited to cases where a specific wavelength is extracted.

[0053] Figure 6 shows an example of a block diagram of the image processing circuit configuration for a multispectral camera to which each optical module of Examples 1-3 is applied. The optical modules are used as ultra-miniature endoscopes for various applications such as observation, imaging, and analysis, not only inside the body. Therefore, among the components, lenses and prisms are becoming miniaturized. However, although image sensors have been miniaturized and made more densely densified to sizes such as 1 / 11th of an inch and 1 / 9th of an inch, there may not be a variety of versatile sensors that are suitable for specific applications. Therefore, an example of a configuration for image processing optical modules that can handle image sensors of different sizes is shown.

[0054] Figure 6 illustrates the image processing of the first image sensor. The first optical image, extracted as an electrical signal from the first image sensor 61, undergoes analog processing in the signal processing circuit 62, including signal amplification and adjustment by a video amplifier and noise processing, and is then converted to digital in the analog-to-digital converter circuit 63. The digitized signal is sent to the memory means 64. The memory means 64 is composed of a frame memory or a field memory and temporarily stores the input first optical image pixel by pixel. The stored image signal is read out in the memory reading means 65 according to the timing pulses of the timing generator generated, formed as an image signal, and output.

[0055] Here, the control of the memory readout means 65 is performed by the control means 66. This control means 66 generates timing pulses for readout and driving the image sensor, and drives the image sensor 61 via the driver (drive circuit) 67 for the image sensor 61. Here, signal readout control is performed according to a preset or inputted readout pattern of the image sensor 61. This readout pattern is set by the setting means 68, which sets various conditions such as the field of view selection according to the image sensor size (1 / 3, 1 / 6, 1 / 9, 1 / 11 inch, etc.), the number of pixels (SD / HD / Full HD / VGA, etc.), and whether the image is inverted or upright. These memory readout setting conditions are set to match the images extracted from each other image sensor and are stored in advance in a storage means 69 such as ROM.

[0056] The signal readout control sets the memory readout conditions using the setting means 68 so that the image output by the image sensor is the same image. However, this is only applicable when the specifications of the image sensor (size, number of pixels) are different or when the acquired image is an inverted image, and it is not necessarily required to be applied to all output images.

[0057] The video signal read out according to the set conditions is sent to the image processing means 70. The image processing means 70 performs a series of image processing processes as needed, such as gain correction, gamma correction, detail processing, and noise reduction, and outputs the first optical image 71. This first optical image 71 is processed with the same field of view and format as the other optical images and is sent to the image synthesis means 72. Figure 6 only describes the image signal processing of the first image sensor 61, but the image processing of the second to fourth optical images from the other image sensors (second to fourth image sensors) can be configured similarly. However, in the image processing of optical images that do not require memory means, it is desirable to match them to the memory output image using a delay circuit or buffer. What is important here is that all of the multispectral output images (first to fourth optical images in a four-chip configuration) maintain the same field of view regardless of the size of the image sensor.

[0058] Multiple optical images maintaining the same field of view are combined by the image combining means 72 and displayed as a combined image on the display device (image monitor) 73. Furthermore, each optical image can be displayed separately, or simultaneously displayed and compared / observed using the split-screen display function of the multi-screen display device 74.

[0059] The method for unifying the images output by each image sensor to images with the same field of view is not limited to the above. Alternatively, pixel values ​​may be read independently for each image sensor to generate a temporary image (e.g., a RAW image) for each image sensor, and then each image may be compressed or enlarged using the compression or enlargement ratio set by the setting means 68 for each image sensor so that they have the same field of view, thereby generating images with the same field of view across image sensors.

[0060] Figure 7 schematically shows an endoscopic imaging device 100. The endoscopic imaging device 100 is an example of a reconnaissance scope. The endoscopic imaging device 100 has an insertion section 120 that is inserted into the body of the subject, and an operation section 140 connected to one end of the insertion section 120 and operated by the observer.

[0061] An optical module 110 according to the above embodiments 1 to 3 is attached to the tip 122 of the insertion section 120 opposite to the operating section 140. The electrical signal of the optical image from the optical module 110 is transmitted to the operating section 140 via a signal line 130, such as a metal wire, which is arranged inside the insertion section 120.

[0062] As described above, according to this embodiment, incident light is reflected twice by the first side (reflecting surface) and the second side (reflecting surface) inside the first pentagonal prism to acquire a first optical image with the first image sensor, and the transmitted light from either the first or second side of the first prism is incident on the second prism to acquire a second optical image with the second image sensor. By selecting either the first or second reflecting surface of the first prism, the prism assembly can be configured in different shapes, providing an optical module with a shape suitable for the imaging environment. Furthermore, by integrating these prism and image sensor configurations as an optical module, it can be placed at the tip of a search scope, enabling imaging in extremely narrow imaging environments. In addition, by further separating the light beam received by the second prism, it is possible to provide an optical module for a multi-channel multispectral camera that can acquire more multiple images.

[0063] Such multispectral cameras are used for comparing, analyzing, and measuring multiple optical images acquired at different wavelengths or wavelength bands through image synthesis or multi-screen image display, as well as for detecting foreign objects. Therefore, the wavelength or wavelength band of the optical image to be extracted is set according to the purpose of use, and the size and resolution of components and materials such as lenses, prisms, and image sensors are individually selected accordingly, requiring the satisfaction of a wide variety of design conditions. However, the optical module according to this embodiment has a configuration that expands the design freedom of the overall shape, and not only reduces design and manufacturing costs by standardizing optical module component materials and enabling the use of different image sensors, but also enables the application of such an optical module to small multispectral cameras in a wide range of uses, including medical endoscopic cameras, surveillance cameras, cameras for observation and analysis microscopes, in-vehicle cameras, weather cameras, aircraft cameras, and endoscope cameras, expanding the range of industrial applications to include professional, consumer, industrial, and medical use.

[0064] 1, 2, 3, 4, 5 Optical module 11 First prism 12, 22, 31, 41 Second prism 13 First image sensor 14 Second image sensor 15 Incident surface of first prism 16 Lens 17 Lens joint (or lens mounting part) 18 First side surface of first prism 19 Second side surface of first prism 20 Exit surface of first prism 21, 24 Exit surface of second prism 23 Reflecting side surface of second prism 25, 26, 48, 49, 50 Circuit board 27, 28 Side oblique viewing prism 32 Exit surface of second prism 42 Third prism 43 Light beam separation surface of second prism 44 Auxiliary prism 45 Third image sensor 46 Exit surface of third prism 47 Third image sensor 51 Fourth prism 52 Exit surface of fourth prism 53 62 Fourth image sensor 63 Signal processing unit 64 A / D conversion circuit 65 Memory 66 Memory read unit 66 Control means 67 Drive unit 68 Setting unit 69 ROM 70 Image processing unit 71 First optical image 72 Image synthesis unit 73 First to fourth optical image composite image 74 First, second, third, and fourth divided images

Claims

1. In an optical module for a search scope that acquires multiple optical images using multiple image sensors, the optical module comprises a first prism and a second prism positioned in close contact with the first prism, the first prism receiving incident light at its incident surface and consisting of a dichroic pentaprism having five sides, at least a portion of the incident light being reflected twice by the first and second sides within the first prism, and exiting from the exit surface of the first prism and incident on a first image sensor, the first image sensor converting the incident light beam into an electrical signal and extracting it as a first optical image, and the incident light from the incident surface and the exit light from the exit surface are configured perpendicular to each other. The optical module is characterized in that the second prism receives transmitted light, which is at least another portion of the incident light that has passed through either the first or second side of the first prism, and emits from the exit surface of the second prism as incident light to the second image sensor, the second image sensor is configured to convert the incident light beam into an electrical signal and extract it as a second optical image, and the first prism, the first image sensor, the second prism, and the second image sensor are integrated and positioned at the tip of the search scope.

2. The optical module according to claim 1, wherein the second prism is arranged in close contact with the first side surface within the first prism, the second prism has a second prism beam separation surface that further reflects and transmits transmitted light that has passed through the first side surface of the first prism, the reflected light reflected by the beam separation surface is incident on a second image sensor, the second image sensor converts the second optical image into an electrical signal and outputs it, the transmitted light that has passed through the second prism beam separation surface is incident on a third image sensor, the third image sensor converts the third optical image into an electrical signal and outputs it, and three optical images are obtained.

3. The optical module according to claim 1, comprising a second prism positioned in close contact with a first side surface within the first prism and a third prism positioned in close contact with a second side surface within the first prism, wherein the third prism is incident on a second image sensor, and the second image sensor converts a second optical image into an electrical signal and outputs it, the second prism has a second prism beam separation surface that further reflects and transmits transmitted light that has passed through the first side surface within the first prism, the reflected light reflected by the second prism beam separation surface is incident on a third image sensor, and the third image sensor converts a third optical image into an electrical signal and outputs it, and the transmitted light that has passed through the second prism beam separation surface is incident on a fourth image sensor, and the fourth image sensor converts a fourth optical image into an electrical signal and outputs it, thereby acquiring four optical images consisting of the first optical image, the second optical image, the third optical image and the fourth optical image.

4. The optical module according to any one of claims 1 to 3, characterized in that the first optical image and the second optical image in claim 1, the third optical image in claim 2, and the fourth optical image in claim 3 are composed of a visible light wavelength band, an infrared light wavelength band, or an ultraviolet light wavelength band.

5. The optical module according to claim 4, characterized in that any two of the first optical image, the second optical image, the third optical image, and the fourth optical image output optical images with a central bandwidth of wavelength 415 nm and wavelength 540 nm.

6. The optical module according to claim 1, characterized in that the optical module includes a lens, a circuit board for an image sensor, and a prism for side-viewing, and is integrated and positioned at the tip of the search scope.

7. The imaging device applying the optical module according to any one of claims 1 to 3, wherein the image processing means for the first optical image and the second optical image in claim 1, the third optical image in claim 2, and the fourth optical image in claim 3 comprises memory means for storing the output signals of any of the image sensors, and the memory means reads out the image so that it matches the reproduced image of the other image sensor when the field of view of the reproduced image differs due to the size of the image sensor, and reads out the image so that it is converted to an upright image when the reproduced image is an inverted image.

8. An endoscopic imaging device comprising any of the optical modules described in claims 1 to 6.

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