Light beam separation optical system and imaging device

Abstract

To provide a beam separation prism structure which is suitable for acquiring a high dynamic range of images, and an imaging device that utilizes this prism structure.SOLUTION: The present invention comprises: a first prism for acquiring an incident image beam as a reflected light component due to the internal reflection of a reflection film or a glass material; a second prism for acquiring a residual light component from the first prism and arranged with the first prism via an air gap; a first imaging element for photoelectrically converting the reflected light component having been acquired by the first prism and outputting a first image signal; and a second imaging element for photoelectrically converting the residual light component having been acquired by the second prism and outputting a second image signal. The first and second image signals are subject to a synthesizing process to acquire an image signal having an extended dynamic range, as well as acquire a high-resolution or a P / S-polarized wave image signal by pixel shifting.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a beam separation optical system including a beam separation prism, an imaging element, etc., and an imaging device to which the same is applied, and particularly relates to a beam separation prism configuration suitable for obtaining a high dynamic range of an image and also obtaining a high resolution, and an image imaging device using the same.

Background Art

[0002] Advances in solid-state imaging devices used in video cameras, still cameras, etc. have enabled various types of miniaturized imaging devices, and various broadband multispectral cameras have been developed. These multispectral cameras are used in a wide variety of applications such as industrial cameras, surveillance cameras, in-vehicle cameras, medical endoscope cameras, and skin disease observation cameras.

[0003] As the use of multispectral cameras diversifies in this way, performance characteristics that can cope with use in various usage environments and conditions have come to be required. In surveillance cameras and in-vehicle cameras, clear images are required day and night, and in medical observation and diagnostic cameras such as endoscopes and dermoscopes, images that can distinguish bright and dark parts by a high-resolution and miniaturized device are required. In particular, when there is a high-brightness light-emitting part such as illumination in an imaging image at night or in low illuminance, in image shooting at the entrance and exit of a tunnel, image acquisition of an illumination reflection part in an endoscope, etc., the illumination light part jumps white or the dark part becomes blacked out, so it is necessary to further expand the dynamic range.

[0004] To expand the dynamic range, a common technique involves acquiring and combining low-light (low-luminance) and high-light (high-luminance) images. To acquire low-light and high-light images, methods exist that involve changing the illuminance or exposure for each frame, line, or pixel of multiple images to obtain two images: one low-light and one high-light. Patent Document 1 describes a method of alternately capturing low-exposure and high-exposure images for each frame and correcting the temporal shift during synthesis. Patent Document 2 discloses a technique that uses a DMD (Digital Mirror Device) to change the amount of reflection for each pixel of the acquired image, thereby acquiring low-luminance and high-luminance images with the changed light intensity. However, such techniques for acquiring and combining low-light and high-light images for each image frame or pixel present problems such as reduced temporal and spatial resolution.

[0005] Patent Document 3 describes a method in which microlenses are alternately arranged on the pixels of an image sensor, and incident light is collected by the microlenses. By combining high-sensitivity pixels and light-receiving areas without microlenses as low-sensitivity pixels, low-light and high-light images are secured. However, this configuration not only makes the image sensor and microlenses complex, but also presents manufacturing difficulties for high-resolution, multi-pixel images.

[0006] Furthermore, methods have been developed to expand the dynamic range through image synthesis, such as acquiring low-luminance and high-luminance images by changing the number of pixels in the image sensor, or acquiring images with different illumination levels by changing the amount of light transmitted using ND (Neutral Density) filters. However, all of these methods require complex circuits and component configurations to expand the dynamic range, degrade the performance and characteristics of the image sensor, or affect the resolution and signal-to-noise ratio during the image processing process. Therefore, they are not satisfactory for achieving high resolution, low noise, and advanced color reproduction, and a method that ensures a high resolution and expanded dynamic range is desired. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2013-118513 [Patent Document 2] Japanese Patent Publication No. 2003-8987 [Patent Document 3] Japanese Patent Publication No. 2005-259750 [Overview of the project] [Problems that the invention aims to solve]

[0008] This invention is provided in view of the above circumstances and primarily aims to provide a light beam separation optical system, an image processing device, and an imaging device capable of acquiring images such as the following. (1) To provide a light beam separation optical system suitable for acquiring images with an extended dynamic range using a simple light beam separation optical system configuration. (2) To provide a light beam separation optical system and an imaging device applying it, which can acquire high dynamic range and high resolution image signals in various imaging environments such as low light, high light, nighttime, daytime, and changing weather conditions, and can acquire images with excellent visibility, enabling use in a wide range of fields such as surveillance cameras, in-vehicle cameras, and medical cameras. [Means for solving the problem]

[0009] To solve these problems and achieve the above objective, the optical system for separating light beams in the present invention receives an image light beam focused by a lens and a reflective film Not applied Inside the glass material surface By reflection The reflected light component of the aforementioned image light beam A first prism to be acquired, and a second prism positioned with respect to the first prism via an air gap, wherein the acquisition from the first prism incident light A second prism that acquires components, a first image sensor that converts the reflected light components acquired by the first prism into photoelectric signals and outputs a first image signal, and the second prism Injected The aforementioned incident light It comprises a second image sensor that converts components into photoelectric signals and outputs a second image signal, The air gap is formed in a range such that the image due to the reflected light component does not become a double image, and the first image signal is a visible light component with less incident light than the second image signal. The first image signal Using this as a secondary image, The second image signal As the main image This method is characterized by acquiring an image signal that expands the dynamic range through synthesis processing.

[0010] Furthermore, the beam separation optical system in the present invention may also be configured such that the reflected light component additionally includes an external reflection component from the incident surface of the second prism.

[0011] Furthermore, the light beam separation optical system in the present invention may also be configured such that the air gap is composed of air or nitrogen gas within the air gap.

[0013] Furthermore, the optical system for separating light beams in the present invention may also be configured to acquire an infrared light separating prism positioned on the image light beam incident side of the first prism, an infrared light image sensor that converts the infrared light component emitted by the infrared light separating prism into photoelectric signals and outputs an infrared light image signal, and to acquire an infrared light image signal with an expanded dynamic range from the infrared light image signal output by the infrared light image sensor.

[0014] Furthermore, in the optical system for separating light beams in the present invention, the second prism is composed of a combination of multiple prisms, and is provided in correspondence with each of the multiple prisms, and the light emitted by the multiple prisms Outgoing light component The system comprises multiple image sensors that convert photoelectric signals and output image signals, wherein one of the multiple image sensors is fixed to the multiple prisms with its pixel pitch shifted by half a pixel pitch from the other image sensors.

[0017] Furthermore, the optical beam separation optical system in the present invention may also be configured such that the second prism is composed of P-polarized wave and S-polarized wave separation prisms, and includes a P-wave image sensor corresponding to the P-polarized wave separation prism that outputs a P-polarized wave image signal, and an S-wave image sensor corresponding to the S-polarized wave separation prism that outputs an S-polarized wave image signal.

[0018] Moreover, it can also be configured as an imaging device including any of the above-described beam separation optical systems. Note that the means for solving the above problems can be used in combination as much as possible.

Advantages of the Invention

[0019] By obtaining the main image component without the reflection film (or separation film) of the beam separation prism in order to obtain the main image component and the sub-image component at different illuminances for dynamic range expansion, the main image can be obtained without loss or noise due to the reflection film. By obtaining the low-illuminance sub-image obtained by the internal reflection of the beam separation prism material and synthesizing it with the high-illuminance main image, it is possible to secure an image with an expanded dynamic range. Also, compared to alternately obtaining images with different illuminances for each field or each pixel, the main image and the sub-image can be separated and obtained in real time by the beam separation prism, so there is no time shift and a color or black-and-white (B / W) image with little reduction in spatial resolution can be obtained. Furthermore, by also performing signal acquisition with pixel shifting between a plurality of main image pickup elements, a high-resolution image with an expanded dynamic range can be obtained.

Brief Description of the Drawings

[0020] [Figure 1] It is an explanatory diagram showing a configuration example of the beam separation optical system of Example 1 according to the present invention. [Figure 2] It is an explanatory diagram showing the sensor output characteristics with respect to the illuminance of the imaging device according to the present invention. [Figure 3] It is an explanatory diagram showing a configuration example of the beam separation optical system of Example 2 according to the present invention. [Figure 4] It is an explanatory diagram showing a configuration example of the beam separation optical system of Example 3 according to the present invention. [Figure 5] It is an explanatory diagram showing a configuration example of the dynamic range expansion block circuit of the beam separation optical system of Example 3 according to the present invention. [Figure 6] It is an explanatory diagram showing a configuration example of the block circuit by pixel shifting in the beam separation optical system of Example 3 according to the present invention. [Figure 7]This is an explanatory diagram showing an example configuration of the optical beam separation optical system of Embodiment 4 according to the present invention. [Figure 8] This is an explanatory diagram showing a modified configuration example of the optical beam separation optical system of Embodiment 4 according to the present invention. [Figure 9] This is an explanatory diagram showing an example configuration of the optical beam separation optical system of Embodiment 5 according to the present invention. [Figure 10] This is an explanatory diagram showing a modified configuration example of the optical beam separation optical system of Embodiment 5 according to the present invention. [Modes for carrying out the invention]

[0021] Hereinafter, embodiments of the light beam separation optical system and imaging apparatus equipped therewith according to the present invention will be described in detail with reference to the drawings. Note that all explanatory diagrams and drawings described in the following embodiments are schematic or representative diagrams for the purpose of explaining the present invention, and do not particularly limit the actual dimensions or shapes. Furthermore, the system configurations, block diagrams, dimensions, materials, shapes, relative arrangements, and usage examples used in the embodiments are not intended to limit the technical scope of the invention to those unless otherwise specified.

[0022] In this invention, the system consists of a first prism (prism for secondary images) and a second prism (prism for primary images) positioned after it via an air gap. In the first prism, the incident light component is acquired by utilizing the internal reflection of the prism without a reflective film to separate the incident light beam, and the secondary image light output is acquired by the image sensor. In the second prism, the residual light component that has passed through the first prism is acquired, and the primary image light output is acquired by the image sensor. The reflected light component acquired by the first prism is acquired by internal reflection (internal reflection) utilizing the difference in refractive index between the prism and the air gap without using a reflective film (optical thin film) with wavelength-selective characteristics. As a result, a portion of the incident light beam (approximately 4% to slightly over 10%) is reflected as a reflected component, and the remaining residual light component, approximately 90% or more, is transmitted to the second prism.

[0023] The image obtained from the internally reflected light component of the first prism has a lower amount of incident light flux compared to the image obtained from the second prism, allowing for a higher saturation level of the image sensor. This difference in the amount of incident light flux can be utilized. The dynamic range of the acquired image is expanded using TIFF0007837495000001.tif13170. Hereinafter, for convenience, the first prism will also be referred to as the sub-image prism, and the second prism as the main image prism. In this invention, the main image and sub-image are assumed to be visible light images, either color images or black and white (B / W) images, but are not limited to these unless otherwise specified. Furthermore, the sub-image and main image may be color images, black and white images, or a combination thereof. [Examples]

[0024] Figure 1 is an explanatory diagram showing Embodiment 1 of the light beam separation optical system (light beam separation prism) 1 according to the present invention. The image light beam incident from the lens section 2 is incident on the secondary image prism 3 (P1) which acts as the first prism. A portion of the incident light beam is reflected by the reflective surface 4 of the prism 3, totally reflected by the total reflective surface 5 of the prism 3, exits from the secondary image prism 3, and then incident on the secondary image sensor 7 via the correction filter 6. The image sensor 7 converts the acquired image light beam into photoelectric energy. TIFF0007837495000002.tif7170 No reflective photoelectric thin films such as films or dielectric multilayer films are applied, and internal reflection of the prism glass material is not performed. TIFF0007837495000003.tif683

[0025] Following the secondary image prism 3 (P1), a primary image prism 8 (P2) is provided via an air gap 9, acting as a second prism. Reflection of the incident light beam also occurs on the outer surface (air gap side incident surface) 10 of the primary image prism 8 (P2), and this reflected image is also used for the secondary image. The incident light beam component that passes through prism 3 (P1) is emitted from the main image prism 8 (P2) and incident on the main image image sensor 12 via the correction filter 11. The image sensor 12 converts the acquired image into a photoelectric signal and outputs the main image signal V.

[0026] This air gap 9 is provided to prevent optical path interference between prisms and to effectively acquire the internal reflected light beam of the secondary image prism 3 (P1). When the secondary image prism 3 (P1) and the primary image prism 8 (P2) are in close contact, the refractive indices of the prism glass materials are the same or only slightly different, resulting in minimal reflection. However, by providing the air gap 9, the internal reflectivity is increased by utilizing the difference in reflectivity between the refractive index of air (1.0 in a vacuum) and the refractive index of the prism glass material. With ordinary refractive index glass, a reflected light beam of slightly over 4% of the incident light beam is acquired, and it has been confirmed that a surface reflection of slightly over 10% can be acquired by using high refractive index glass (refractive index of 1.67 or higher) to increase the reflectivity ratio. Therefore, the separation ratio of reflected light beam to transmitted light beam can be approximately 4%:96% with ordinary glass materials that are not high index, and approximately 10%:90% with high refractive index glass materials referred to as high index type.

[0027] This air gap 9 allows the light beam component incident on the secondary image prism 3 to be acquired not only from the internal reflection component by the reflective surface 4 of the prism 3, but also from the external reflection from the outer surface of the incident surface 10 (outside) of the main image prism 8. While good results have been obtained with an air gap 9 of approximately 5-30 μm, it is desirable to have an air gap small enough that mutual interference (beats) or double images do not occur between the internal reflection image of the secondary image prism 3 and the external reflection image of the main image prism 8 (P2). Furthermore, applying an anti-reflective coating (ARC) to the incident surface 10 (air gap side) of the main image prism 8 (P2) can reduce these beats and double images. In this way, without forming a reflective film by vapor deposition or coating, approximately 4% or more of the reflected component of the incident light beam component incident on the light beam separation prism 1 can be acquired through internal reflection of the secondary image prism 3 and external reflection on the incident side of the main image prism 8. TIFF0007837495000005.tif7167

[0028] Alternatively, the prism glass surface can be configured to prevent oxidation by filling the air gap 9 with nitrogen gas. In this case, the refractive index of nitrogen is 1.000297, and the refractive index of air is 1.000293. Since these refractive indices are nearly the same, the reflectivity can be considered to be the same as that of air.

[0029] With this configuration, the image of the reflected light component obtained by internal reflection of the prism (secondary image) The residual light component (main image signal V) obtained in TIFF0007837495000006.tif7170 can be acquired in a quantity of over 90%. Details will be described later. By combining and interpolating the saturation in the main image using a secondary image from different low-light and high-light images of TIFF0007837495000007.tif7170, it becomes possible to acquire a color image with an expanded dynamic range in real time without time lag. Furthermore, because the acquired main image does not have metal films or coating interference films, it is not affected by these optical thin films, and compared to methods that acquire low-light images using optical thin films, it is possible to acquire a main image V with excellent visibility, free from noise and loss caused by optical thin films.

[0030] Next, we will explain the extension of the dynamic range using the beam separation optical system described above. This explanation assumes that TIFF0007837495000008.tif12170 was obtained. Figure 2 is an explanatory diagram showing the output sensor level of the visible light image sensor for the main image signal and the sub-image signal as a function of illuminance. Each visible light image sensor is assumed to have the same characteristics, and its saturation level is set to 300% as an example. This is because knee processing is applied to keep the signal amplitude within the normalized range of a video signal, even when only white light is input. This illustrates the case where the saturation level is set to several times (300%) relative to the specified level (100% level) (curve V main image characteristics).

[0031] The file is TIFF0007837495000009.tif6170, and the illuminance input to each image sensor is 90:10. Therefore, assuming the performance of the image sensors is the same and the saturation level of the image sensor set by the main image V signal is 300%, (TIFF0007837495000010.tif7170 Sub-image characteristics). In other words, even when the main image output reaches a saturation level, the sub-image output, which has lower illumination, will not be saturated up to about 10 times the illumination of the main image.

[0032] TIFF0007837495000011.tif7170 By correcting and gamma processing, the compressed signal (curve V+) is compressed to the specified level of 100%. TIFF0007837495000012.tif11170 Set the sensor to the specified 100% level to prevent saturation (such as overexposure) of the sensor image acquired by processing and combining it with the image signal.

[0033] In the light beam separation prism according to the present invention, there is no deposited metal thin film or coating film, and the secondary image component is acquired solely by internal reflection of the prism glass material. In other words, the main image component does not pass through reflective films such as metal thin films or dielectric multilayer films and is incident on the prism for acquiring the main image, making it possible to acquire an image with an expanded dynamic range, less noise and loss due to the separation film, without being affected by the reflective film for acquiring the image signal. Naturally, the synchronization of the image phase of each image signal is ensured by a synchronization signal generation means (not shown), reducing timing errors and other issues. [Examples]

[0034] Figure 3 is an explanatory diagram showing an example configuration of the light beam separation optical system (light beam separation prism) 20 of Embodiment 2 according to the present invention. In the light beam separation prism 20 of Embodiment 2, an infrared light separation prism is placed on the incident light side of the light beam separation prism of Embodiment 1 described above, and a three-plate separation prism consisting of an infrared light image sensor, a secondary image image sensor, and a primary image image sensor is constructed. In Figure 3, the shapes of the secondary image prism 3 (P1) as the first prism and the primary image prism 8 (P2) as the second prism differ from those of Embodiment 1 and Figure 1, but the component configuration corresponding to the components in Figure 1 is given the same numbers. The image light beam incident from the lens section (not shown) is incident on the infrared light separation prism 21 (PIR), and the infrared light component is separated and reflected by the reflective surface 22 of the infrared light separation prism 21, while the visible light band component is transmitted. The reflective surface 22 is coated with an optical film such as a thin metal film or a dielectric film that has wavelength selectivity to reflect the infrared light band component and transmit the visible light component. The infrared light component reflected by the infrared light reflecting surface 22 is totally reflected by the total reflection surface 23 of the infrared light separation prism 21, exits the infrared light separation prism 21, and is incident on the infrared light image sensor 25 via the infrared light correction filter 24. The infrared light image sensor 25 converts the acquired infrared light component into photoelectric data and outputs it as an infrared light image (IR). Here, the infrared light correction filter 24 is a band filter that cuts out the visible light component and extracts the desired infrared light band (for example, only the near-infrared light component), and is a filter that limits the extraction to the necessary infrared light band according to the purpose of use.

[0035] A prism configuration similar to that in Example 1 is provided downstream of the infrared light separation prism 21 via an air gap 26. The air gap 26 here is a gap to prevent optical path interference between the infrared light prism (PIR) and the secondary image prism (P1). The visible light component transmitted through the infrared light separation prism 21 enters the secondary image prism 3 (P1), as in Example 1, undergoes internal reflection by the reflective surface 4 of the prism 3, undergoes total internal reflection by the total reflection surface 5 of the prism 3, exits the prism 3, and enters the secondary image sensor 7 via the correction filter 6. TIFF0007837495000013.tif8170 The reflective surface 4 of the secondary image prism 3 (P1) does not have any optical thin films such as wavelength-selective metal thin films applied to it, and the difference in refractive index between the prism glass material and the air gap is utilized. TIFF0007837495000014.tif6170 These optical thin films allow for the acquisition of highly visible images without loss or influence.

[0036] A main image prism 8 (P2) is located downstream of the secondary image prism 3 (P1) via an air gap 9. The visible light component that passes through the secondary image prism 3 (P1) exits through the main image prism 8 (P2) and enters the main image sensor 12 via a correction filter 11. The image sensor 12 converts the acquired visible light image into photoelectric signals and outputs a main image signal V. TIFF0007837495000015.tif12170

[0037] In Example 2, a visible light (color or black and white) image with an expanded dynamic range is used. The ability to acquire both TIFF0007837495000016.tif7170 images and high dynamic range visible light image signals significantly expands the range of applications for multispectral cameras. Imaging devices that acquire infrared light images are used in surveillance cameras, in-vehicle cameras, medical cameras, and military cameras, but in cases where the contrast between light and dark areas differs drastically, it becomes necessary to expand the dynamic range. For example, in extremely bright images such as those created by backlighting, overexposure occurs, and in dark areas, underexposure occurs, making it impossible to capture details of the image. In in-vehicle cameras and military surveillance cameras, it is necessary to avoid these overexposure and underexposure phenomena as much as possible. By applying the light beam separation prism according to Example 2, it is possible to synthesize a visible light image with an expanded dynamic range that eliminates these problems with an infrared light image, making it possible to obtain an imaging device with superior visibility in day and night and backlit shooting conditions. [Examples]

[0038] Figure 4 is an explanatory diagram showing the light beam separation optical system (optical separation prism) 30 of Embodiment 3 according to the present invention. In the light beam separation prism 30 of Embodiment 3, the sub-image prism 3 (P1), which corresponds to the first prism, is the same as the sub-image prism in Figure 1, and the same component configuration is given the same number. In Embodiment 3, a single-chip color image sensor 7 is mounted on the sub-image prism 3 (P1). Following that, the main image prism, which corresponds to the second prism, has a four-chip (four-image sensor) configuration consisting of a red separation prism 32 (PR), a blue separation prism 33 (PB), and a green separation prism 34 (PG). In other words, while Embodiment 1 uses a single-chip color image sensor as the main image prism, Embodiment 3 extracts three-color image signals by combining three color separation prisms of R, G, and B. Furthermore, Embodiment 3 presents a method that utilizes the three-color separation prism configuration to acquire a high-resolution main image by pixel shifting and then expand the dynamic range.

[0039] The incident image light beam enters the secondary image prism 3 (P1), and a portion of the image light beam is internally reflected by the reflective surface 4 of the prism 3. The internally reflected light beam is configured at various reflection angles so that it is fully reflected by the total reflective surface 5 of the secondary image prism 3. The image light beam that has been totally reflected by the total reflective surface 5 exits the secondary image prism 3 and enters the secondary image prism image sensor 7 of the single-chip color image sensor via the correction filter 6. TIFF0007837495000017.tif7152

[0040] The reflective surface 4 of the secondary image prism 3 does not have any wavelength-selective optical thin film applied to it, and the reflected light beam is obtained by internal reflection of the prism glass material. Behind the secondary image prism 3, R, G, and B three-color separation prisms are arranged for the main image, and the image light beam that passes through the secondary image prism 3 is incident on the red separation prism 32 (PR). An air gap 9 is provided between the secondary image prism 3 and the red separation prism 32.

[0041] This air gap 9 is similar to the air gap provided between the secondary image prism and the primary image prism in Examples 1 and 2. No optical thin film is used on the reflective surface 4 of the secondary image prism 3. Instead, internal reflection of the image light beam is obtained due to the difference in refractive index between the air or nitrogen gas in this air gap and the secondary image prism glass material. Therefore, the transmitted primary image light beam component is free from loss or influence by the optical thin film, improving optical characteristics. Furthermore, the reflected component from the incident surface 40 (gap side) of the red separation prism 32 (PR) can also be used as the secondary image light beam. The incident surface 40 (gap side) can also be configured to reduce beats and double images by applying an anti-reflective coating.

[0042] The residual component of the light beam of incident light that enters the red separation prism 32 (PR) is separated and reflected by the separation reflective surface 41 of the prism 32, with the red light band component being separated and reflected, while the other band components are transmitted and incident on the subsequent prisms. The separation reflective surface 41 of the red separation prism 32 is formed by a vapor deposition coating of a metal thin film or a dielectric multilayer film coating that has wavelength-selective characteristics that reflect the red light component and transmit the other band components. The red light component reflected by the separation reflective surface 41 is configured to be reflected across the entire surface by the inner total reflection surface 40 of the red prism. The red light component reflected across the entire surface by the total reflection surface 40 (inner) exits the red separation prism 32 and enters the red image sensor 43 via the correction filter 42. This image sensor 43 converts the incident red light component into an electrical signal and outputs a red light image signal (R). The correction filter 42 is a filter that selectively extracts the red light band.

[0043] The transmitted light component that passes through the red separation prism 32 (PR) consists of wavelength band components other than the red band (mainly blue and green band components), and is incident on the blue separation prism 33 (PB) located after the red separation prism 32. The light beam incident on the prism 33 has its blue light component reflected by the blue light separation reflective surface 44, while the other bands (mainly green light components) are transmitted. The blue light separation reflective surface 44 is formed of an optical thin film that selectively reflects the blue light band. At the blue light separation reflective surface 44, the wavelength band of the blue component is reflected as reflected light, while the other green components are transmitted and incident on the next stage green prism 34 (PG). Here, an air gap 45 is provided between the red separation prism 32 (PR) and the blue separation prism 33 (PB), configured to prevent mutual interference between the optical paths of each prism.

[0044] The blue light component reflected by the separation reflection surface 44 of the blue separation prism 33 (PB) is totally reflected by the inner reflection surface 46 of the blue separation prism 33, and the prism shape is configured so that the blue light component reflected by the total reflection surface 46 is incident on the blue image sensor 48 via the correction filter 47. The image sensor 48 converts the incident blue light component into an electrical signal and outputs a blue light image signal (B). The correction filter 47 is a filter that selectively extracts the blue light band.

[0045] The visible light band transmitted through the blue separation prism 33 (PB) is mainly the green wavelength band component and is incident on the green prism 34 (PG), which is positioned closely behind the blue separation prism 33. This green light component passes through the green prism 34 and exits, and is incident on the green image sensor 50 via the green correction filter 49. The image sensor 50 converts the incident green light component into an electrical signal and outputs a green light image signal (G). The green correction filter 49 is a filter that selectively extracts the green light band.

[0046] In this prism configuration, the secondary image is created by internal reflection of the secondary image prism 3 (P1). TIFF0007837495000018.tif7170(PB), with the green prism 34(PG), outputs the R, G, and B visible light components respectively for the main image.

[0047] In this embodiment 3, the visible light components are separated and acquired in the order of red (R), blue (B), and green (G) in the main image prism, which corresponds to the second prism, but the order in which each visible light component is acquired does not matter. The important point here is that, prior to the visible light prism combination consisting of R, G, and B that constitutes the main image prism, the reflective surface 4 of the sub-image prism 3 (P1), which corresponds to the first prism, does not have a reflective film made of an optical thin film, and internal reflection of light is generated within the prism. The incident light beam on TIFF0007837495000019.tif7170 minimizes losses and influences from the reflective film, enabling the acquisition of the main image component.

[0048] TIFF0007837495000020.tif6170 The main image components R, G, and B are acquired as the remaining residual luminous flux components, and by utilizing this difference in the amount of incident luminous flux, a color image with an expanded dynamic range is acquired. Figure 5 is a block diagram showing an example of a circuit for expanding the dynamic range in this embodiment 3. The red image output R, blue image output B, and green image output G acquired by the luminous flux separation optical system 30 are supplied to the dynamic range (DR) expansion processing means 51 for each output.

[0049] TIFF0007837495000021.tif12170 is supplied to means 51. Within DR extension processing means 51, the R, G, B output signals and demosaicing are performed. In TIFF0007837495000022.tif7170 and 55, synthesis processing and other related processing are performed. The output signals synthesized by each image synthesis processing means 53, 54, and 55 are supplied to the image signal processing means 56. This image processing means 56 is an image signal processing processor that applies a series of image processing, such as noise reduction, gain correction, detail, and gamma, to the image signals obtained by each image sensor and outputs them.

[0050] The outputs of the R, B, and G image processing means 56 are supplied to the matrix circuit 57, which outputs a component signal consisting of a luminance signal (Y) and a chrominance signal. Depending on the purpose of use, this chrominance signal outputs signals such as (U, V), (Pb, Pr), and (Cb, Cr). Here, the matrix circuit 56 generates the chrominance signal, but the component signal can be any of the R, G, and B image outputs, or it can be (Y / U / V), (Y / PB / PR), (Y / Pb / Pr), (Y / Cb / Cr), etc., consisting of a luminance signal and a chrominance signal.

[0051] In this embodiment 3, in addition to dynamic range expansion using the main image signal and sub-image signal acquired as described above, the system is configured to acquire a high-resolution image by pixel shifting. In the light beam separation optical system 30 of the present invention, the green light image sensor 50 attached to the green prism 34 (PG) is positioned shifted by half a pixel pitch relative to the red image sensor 43 of the other red separation prism 32 (PR) and the blue image sensor 48 of the blue separation prism 34 (PB).

[0052] Figure 6 is a block diagram illustrating the pixel shifting process of such a light beam separation optical system 30 configuration. The R, G, and B image signals extracted by the respective R, G, and B image sensors are supplied to the pixel shifting processing means 60. The image signals extracted by each image sensor are synchronized in terms of image phase by a synchronization signal generation means (not shown). In the pixel shifting processing means 60, the green light image output G and the other R and B image output signals are used to sample the luminance signal (Y). As a result, the extracted luminance signal (Y) sample can acquire three primary color (R, G, B) signals with twice the resolution due to the pixel shifting effect. The three primary color signals with doubled resolution are combined with the sub-image signal as described above in the dynamic range expansion means 51, expanding the dynamic range, and supplied to the image processing means 56.

[0053] In other words, if a 2K image sensor is used as the image sensor, an image signal equivalent to a resolution of 4K can be obtained. The dynamic range is expanded using the image signal obtained by increasing the resolution through pixel shifting processing in this way by the dynamic range expansion processing means 51. This dynamic range expansion processing means is the DR expansion processing means 51 shown in Figure 5 and The TIFF0007837495000023.tif6170 signal is combined with the R, G, and B main image signals.

[0054] Because it does not use optical thin films such as vapor-deposited films or coating films, it is possible to obtain visible light images with excellent visibility without loss or noise caused by optical films, and visible light images with an expanded dynamic range, as well as visible light images with improved resolution due to pixel shifting.

[0055] In this embodiment 3, the main image is acquired using a three-primary-color (R, G, B) separation prism as the second prism. However, by additionally providing a green separation prism to acquire four colors (R, G1, G2, B), and shifting the G1 and G2 pixels by half a pixel pitch, and sampling and extracting the luminance signal, an image signal with twice the resolution (an image signal called a dual-green pixel-shifted image signal) can be acquired. Furthermore, the main image prism used as the second prism is not limited to the three-plate (R, G, B) or four-plate (R, G1, G2, B) system exemplified above. Any system using multiple main image prisms or multiple image sensors that allows for pixel-shifted arrangement of specific main image sensors with other main image sensors to increase resolution through pixel shifting is acceptable. [Examples]

[0056] Figure 7 is an explanatory diagram showing the light beam separation optical system 70 using a three-chip image sensor in Example 4. The light beam separation optical system 70 acquires P-polarized and S-polarized wave images of visible light using a P / S separation prism in the main image prism, which corresponds to the second prism of the light beam separation optical system 1 in Figure 1. The same component configuration as the light beam separation optical system 1 in Figure 1 is given the same numbers. In Figure 7, the image light beam focused by the lens section (not shown) is incident on the sub-image prism 3 (P1), which corresponds to the first prism. The image light beam incident on the prism 3 is shown in Figure 1 Output TIFF0007837495000025.tif7170V. Similar to Figure 1, this prism 3 does not use an optical thin film for light beam reflection on its reflective surface 4, but instead obtains the reflected light beam by utilizing the difference in reflectivity between the prism 3 and the air gap 9. Therefore, the transmitted main image light beam component can be obtained without loss or influence from the optical thin film. This image was obtained solely through internal reflection in TIFF0007837495000026.tif61703(P1), where a portion of the incident light beam is reflected within the prism, and the remaining light beam is transmitted and incident on the subsequent main image prism.

[0057] The image light beam that passes through the secondary image prism 3 is incident on the primary image prism, which is positioned behind the secondary image prism 3 (P1) with an air gap 9 in between. This primary image prism is a P / S separation prism composed of an S-wave prism 71 (PS) that acquires the S-polarized wave image of the primary image and a P-wave prism 76 (PP) that acquires the P-polarized wave image. This P / S separation prism can be configured as an integrated polarizing beam splitter (PBS). The light beam incident on the S-wave prism 71 (PS) is separated into the S-polarized wave component and the P-polarized wave component of the primary image by the P / S separation film 72, the S-polarized wave component is reflected and the P-polarized wave component is transmitted. The S-polarized wave component reflected by the P / S separation film 72 is totally reflected by the total reflection surface 73 of the prism 71 and incident on the primary image S-wave image sensor 75 via the correction filter 74. The image sensor 75 converts the incident light beam into photoelectric signals and outputs a main image S-wave image signal (V / S).

[0058] The light beam (mainly the P-wave component of the main image) that has passed through the P / S separation film 72 exits from the P-wave prism 76 (PP) and enters the main image P-wave image sensor 78 via the P-polarization wave correction filter 77. The image sensor 78 converts the incident light beam into photoelectric signals and outputs the main image P-wave image signal (V / P). Here, the correction filters 74 (for S-polarization waves) and 77 (for P-polarization waves) are S-wave polarizing filters and P-wave polarizing filters that transmit their respective polarized waves, and as needed... The TIFF0007837495000027.tif7170 signal V / S and the main image P-wave signal V / P are acquired. Here, P / S polarization wave separation by the separation film 72 is generally based on uniform separation, but the separation ratio between the S-polarized wave image and the P-polarized wave image can be changed depending on the purpose of use.

[0059] TIFF0007837495000028.tif7169 represents a portion of the incident light beam, and the main image signals V / S and V / P allow us to obtain the amount of light beam of the residual component that has been transmitted relative to the amount of incident light. By utilizing this difference in image light beam amounts, the main image S-wave signal V / S and P-wave signal V / P are combined with the sub-image signal using the same method as described above. TIFF0007837495000029.tif12170

[0060] Figure 8 is an explanatory diagram showing a modified configuration example (light beam separation optical system 80) of the light beam separation optical system of Figure 7 according to the present invention, in which modified polarizing beam splitters 71' and 76' are applied as P / S separation prisms. The same component configuration as in Figure 7 is given the same numbers. The P / S separation film 72' of the optical beam splitter is composed of a reflection / separation surface at a 45° angle to the incident optical axis. The S-polarized wave component is reflected by this P / S separation film 72' and incident on the S-polarized wave image sensor 75 via the correction filter 74, outputting the S-polarized wave image component (V / S). On the other hand, the P-polarized wave component that has passed through the separation film 72' is incident on the P-polarized wave image sensor 78 via the correction filter 77, outputting the P-polarized wave image component (V / P). Here, the acquired S-polarized wave image component is acquired as the reverse image (opposite image) of the other output images because it is an image of the light beam that has been reflected once by the P / S separation film 72'. Therefore, the acquired S-wave image output V / S is inverted by the image inversion circuit 89 and used as the same front image as the other images.

[0061] The light beam separation optical systems 70 and 80 in this embodiment 4 can be applied in various situations that utilize the characteristics of S-wave and P-wave images. For example, in traffic monitoring, when it is difficult to see the driver inside a car due to light reflection from the windshield, a P-wave image with suppressed surface reflection can be acquired as a high dynamic range image, allowing for confirmation with a more visible image. In practice, it is also possible to switch between the acquired S-wave and P-wave images with expanded dynamic range, or to combine the acquired S-wave and P-wave images to create a more sensitive composite image, which can then be compared, analyzed, and used. In particular, it can be effectively applied to image analysis of scenes involving glass or water surface reflections where high-intensity lights are reflected. [Examples]

[0062] Figure 9 is an explanatory diagram showing a light beam separation optical system 90 using a four-plate image sensor. In Figure 9, an infrared light separation prism 21 (PIR) is placed on the incident side of the image light beam of the three-plate image sensor in Figure 7. TIFF0007837495000031.tif6170 acquires an ambient light image signal (IR). This beam separation optical system 90 acquires S-polarized and P-polarized wave images of visible light by using a P / S separation prism (PBS) instead of the main image prism corresponding to the second prism of the beam separation optical system 20 in Figure 3, and the same component configuration as the beam separation optical system 20 in Figure 3 is given the same numbers.

[0063] In Figure 9, the image light beam focused by the lens unit (not shown) first enters the infrared light separation prism 21 (PIR). The incident image light beam is separated and reflected by the reflective surface 22 of the infrared light separation prism 21. The reflective surface 22 is coated with an optical thin film, such as a metal thin film or dielectric film, which has wavelength selectivity to reflect infrared light band components and transmit visible light components. The infrared light components reflected by the infrared light reflective surface 22 are totally reflected by the total reflection surface 23 of the infrared light separation prism 21, exit the infrared light separation prism 21, and enter the infrared light image sensor 25 via the correction filter 24. The infrared light image sensor 25 converts the acquired infrared light image components into photoelectric data and outputs it as an infrared light image (IR). The correction filter 24 is a band filter that cuts out the visible light component and extracts the desired infrared light band (for example, only the near-infrared light component), and is a filter that restricts the extraction to the necessary infrared light band according to the purpose of use.

[0064] The visible light component that has passed through the infrared light separation prism 21 is incident on the secondary image prism 3 (P1), which corresponds to the first prism and is positioned across the air gap 26. The image light beam incident on the secondary image prism 3 is reflected by the reflective surface 4 inside the prism, totally reflected by the total reflection surface 5, exits the prism 4, and is incident on the secondary image sensor 7 via the correction filter 6. In TIFF0007837495000032.tif7170, the reflected light beam is obtained solely by internal reflection of the prism, without applying an optical thin film for separate reflection to the reflective surface 4 within the prism. Therefore, a portion of the incident light beam is reflected and transmitted, and the majority of the remaining light beam (main image beam) is transmitted without the influence of the optical thin film and enters the subsequent main image prism across the air gap 9.

[0065] The main image prism is a polarizing beam splitter (PBS) and consists of an S-wave prism 81 (PS) for acquiring the S-polarized wave image of the main image and a P-wave prism 86 (PP) for acquiring the P-polarized wave image. The light beam incident on the S-wave prism 81 (PS) is separated into the S-polarized wave component and the P-polarized wave component of the main image by the P / S separation film 82, the S-polarized wave component is reflected and the P-polarized wave component is transmitted. The S-polarized wave component reflected by the P / S separation film 82 is totally reflected by the total reflection surface 83 of the prism 81 and incident on the main image S-wave image sensor 85 via the S-polarized wave correction filter 84. The image sensor 85 converts the incident light beam into photoelectric signals and outputs the main image S-wave image signal (V / S).

[0066] The light beam (mainly the P-wave component of the main image) that has passed through the P / S separation film 82 exits from the P-wave prism 86 and enters the main image P-wave image sensor 88 via the P-polarized wave correction filter 87. The image sensor 88 converts the incident light beam into photoelectric signals and outputs the main image P-wave image signal (V / P). Here, the correction filters 84 (for S-polarized waves) and 87 (for P-polarized waves) are S-wave polarizing filters and P-wave polarizing filters that transmit their respective polarized waves, and are arranged as needed. The TIFF0007837495000033.tif6170 and the main image P-wave signal V / P are acquired, and these signals are combined as described above to perform dynamics analysis. Retrieve TIFF0007837495000034.tif7170V+V / P).

[0067] Figure 10 is an explanatory diagram showing a beam separation optical system 100 as a modified configuration example of Figure 9 according to the present invention, in which modified polarizing beam splitters 81' and 86' are applied as P / S separation prisms. In Figure 10, the same component configurations as in Figure 9 are given the same numbers. The file is TIFF0007837495000035.tif6170. The P / S separation film 72' of the polarizing beam splitter is composed of a reflection / separation surface at a 45° angle to the incident optical axis. The S-polarized wave component is reflected by this P / S separation film 82' and incident on the S-polarized wave image sensor 85 via the correction filter 84, outputting the S-polarized wave image component (V / S). On the other hand, the P-polarized wave component that has passed through the separation surface 82' is incident on the P-polarized wave image sensor 88 via the correction filter 87, outputting the P-polarized wave image component (V / P). Here, the acquired S-polarized wave image component is acquired as a reverse image (opposite image) because it is an image of the light beam that has been reflected once by the separation surface 82'. Therefore, the acquired S-wave image output V / S is inverted by the image inversion circuit 89 and used as the same front image as the other images.

[0068] In the beam separation optical systems 90 and 100 of this embodiment 5, the dynamic range was expanded. TIFF0007837495000036.tif6170 acquires an image signal (IR). Examples of applications for imaging devices incorporating such a light beam separation prism 80 include medical skin observation cameras such as endoscopes and dermatoscopes (dermoscopy). In the observation and analysis of skin diseases, observing the subcutaneous condition in addition to the surface condition of the skin allows for a more detailed and accurate diagnosis. For this purpose, the subcutaneous condition can be observed using infrared light images, or high dynamic range S-polarized wave images and P-polarized wave images can be acquired by irradiating liquid-like skin diseases with a light, and then compared, observed, and evaluated to confirm the condition of the skin lesion.

[0069] The above describes a configuration in which a secondary image signal is acquired by internal reflection of a prism without a reflective film, combined with the main image signal for dynamic range expansion, and where a pixel shifting technique for the main image signal is applied to increase image resolution or to acquire a P / S polarized wave image. However, it goes without saying that the present invention can be applied to multiple sensor configurations such as 2-plate, 3-plate, 5-plate, and 6-plate systems, without being limited by the bandwidth of the acquired image signal or the number of image sensors and prisms, as long as it does not depart from the spirit of the present invention. [Industrial applicability]

[0070] The optical system for separating light beams according to the present invention makes it possible to acquire images with high dynamic range and high resolution that are highly visible. When combined with infrared light images or P / S polarized wave images, it has a wide range of applications, including FA cameras, surveillance cameras, observation cameras, in-vehicle cameras, weather cameras, aircraft cameras, and endoscope cameras, expanding its potential for use in a wide range of industries, including professional, consumer, industrial, medical, and military applications. [Explanation of Symbols]

[0071] 1. Light beam separation optical system, 2. Lens section, 3. Prism for secondary image (P1), 4. P1 reflective surface, 5. P1 total reflection surface, 6. Correction filter for P1, 7. Image sensor for secondary image, 8. Prism for primary image (P2), 9. Air gap, 10. P2 incident surface (outer) / P2 total reflection surface (inner), 11. Correction filter for P2, 12. Image sensor for primary image, 21. Infrared light separation prism (PIR), 22. PIR reflective surface (separation surface), 23. PIR total reflection surface, 24. Correction filter for PIR, 25. Infrared light imaging Element, 26. Air gap, 32. Red separation prism (PR), 33. Blue separation prism (PB), 34. Green prism (PG), 51. Dynamic range (DR) expansion processing means, 52. Demosaicing processing means, 56. Image processing means, 57. Matrix circuit, 60. Pixel shifting processing means, 71. S-wave prism (PS), 72. P / S separation film, 75. S-wave image sensor, 76. P-wave prism (PP), 78. P-wave image sensor, 82. P / S separation film, 89. Image inversion circuit

Claims

1. A first prism receives an image light beam focused by a lens and obtains the reflected light component of the image light beam by internal reflection of a glass material without a reflective coating, A second prism is positioned with the first prism via an air gap, and the second prism acquires the incident light component from the first prism, A first image sensor that converts the reflected light component acquired by the first prism into photoelectric power and outputs a first image signal, The system comprises a second image sensor that converts the incident light component incident on the second prism into photoelectric power and outputs a second image signal, The air gap is formed in such a range that the image due to the reflected light component does not become a double image. The first image signal is a visible light component with less incident light than the second image signal, and the first image signal is used as a secondary image and the second image signal as a primary image, and the optical beam separation optical system is characterized by combining them to obtain an image signal that expands the dynamic range.

2. The beam separation optical system according to claim 1, characterized in that the reflected light component additionally includes an external reflection component from the incident surface of the second prism.

3. The light beam separation optical system according to claim 1, characterized in that the air gap is composed of air or nitrogen gas within the air gap.

4. An infrared light separation prism is positioned on the image beam incidence side of the first prism. The system includes an infrared image sensor that converts the infrared light component emitted by the infrared light separation prism into an infrared light image signal. The optical beam separation optical system according to claim 1, characterized in that it acquires an infrared light image signal output by the infrared light image sensor and an image signal with an expanded dynamic range.

5. The aforementioned second prism is composed of a combination of multiple prisms, The system comprises multiple image sensors, each provided in correspondence with the plurality of prisms, which convert the emitted light components from the plurality of prisms into photoelectric signals and output an image signal. The optical beam separation optical system according to claim 1, characterized in that one of the plurality of image sensors is fixed to the plurality of prisms with its pixel pitch shifted by half a pixel pitch from the other image sensors.

6. The second prism is composed of a P-polarized wave and an S-polarized wave separation prism. A P-wave imaging sensor that outputs a P-polarized wave image signal corresponds to the P-polarized wave separation prism, The optical beam separation optical system according to claim 1, comprising an S-wave imaging sensor that outputs an S-wave polarized image signal and corresponds to the S-wave polarized wave separation prism.

7. An imaging apparatus comprising any of the light beam separation optical systems described in claims 1 to 6.

Images