Multi-sensor system with optical beam splitter

Abstract

An imaging system comprising: a first image acquisition means, a second image acquisition means, a first imaging device configured to image a first scene on the first image acquisition means based on a light beam, and a second imaging device configured to image a second scene on the second image acquisition means based on the light beam, wherein the first imaging device comprises a forward optical unit including a forward lens, a beam splitter configured to split the light beam into a first light beam and a second light beam propagating in a different direction than the first light beam, and a first rear optical unit; and the second imaging device comprises the forward optical unit, the beam splitter, and the second rear optical unit, wherein a focus of one imaging device is a macro focus and a focus of the other imaging device is a wide-angle focus, the macro focus being within a range of 0 mm to 1 mm in front of the forward lens, and the wide-angle focus being at least 3 mm in front of the forward lens.

Description

[Technical field]

[0001] The present invention relates to a multi-sensor system with an optical beam splitter, which is preferably used in an endoscope, in particular an endoscope for insertion into a hollow space of the human body, although the use is not limited to endoscopes, even though the further description mainly relates to the use in endoscopes. [Background technology]

[0002] Endoscopes with fixed optics and with a zoom objective are known in which an image of a scene in the object space is acquired by a single image sensor. Summary of the Invention

[0003] The objective lens of the endoscope includes two or more imaging elements (image acquisition means). Each imaging element acquires an image formed of a respective scene on the imaging element by a respective imaging device. The imaging devices have a common front optical unit and a common beam splitter. Respective rear optical units follow the beam splitter. At least the front optical units have a non-zero optical refractive power. Furthermore, at least one of the rear optical units has a non-zero refractive power, but some or all of the rear optical units may have a non-zero refractive power. In this way, different images are acquired on the imaging elements. The light bundle may be split in a non-dichroic manner. The combinations of the imaging devices and the respective imaging elements are therefore different with respect to their focal points. One of the imaging devices ("macro") has its focus on or just before the frontmost lens (up to 1 mm in front of the apex of the frontmost lens on the subject side), while another one of the imaging devices ("wide angle") has its focus further away (more than 3 mm in front of the apex, preferably in the range of 3 mm to 12 mm in front of the apex). Furthermore, the imaging devices may differ by their focal width (i.e. the distance of the focus of each imaging device from the front focus of the respective imaging device), their focal length, their maximum viewing angle, their iris aperture, their average transmittance in the RGB wavelength range of visible light, and / or the average sensitivity of their imagers in the RGB wavelength range of visible light, where the RGB wavelength ranges are defined as 650 nm±5 nm, 532 nm±5 nm, and 460 nm±5 nm, respectively. For example, the rear optical units may have different values ​​for at least one of said parameters and / or the imagers may have different average sensitivities in the relevant wavelength ranges.

[0004] Imaging on the imager takes place without the need for intermediate imaging, in particular without the need for intermediate imaging on a beam splitter, which helps to avoid accumulation of imaging errors.

[0005] Since the front optical unit is identical for the imaging device, the imagers acquire certain scenes that are at least partially overlapping or even identical when viewed from the front optical unit. On the other hand, the images on the imagers are different, at least because the focus is different. If the images of at least two imagers are combined, a higher depth of field can be achieved than is possible with a single image. Another option is for the imaging device to allow different magnifications. For example, by switching the imagers, a multi-stage (e.g., two-stage) zoom can be formed. Notably, no moving parts are required for the imaging system for this type of zoom.

[0006] The combination of different focal points with different focal lengths is particularly advantageous since it results in different magnifications for imaging by the two imaging devices when the same scene is at the focus of each imaging device, where magnification is defined as the ratio of the imaging size to the object size. This can be utilized for example in endoscopy as follows:

[0007] The doctor can first inspect the area to be inspected by a sensor with a common magnification, from a larger distance, and with a relatively far focus (e.g., 3 mm or more). If the doctor wants to inspect the details in the observed scene more precisely, he can move the endoscope closer to the tissue, or even place it on the tissue. Then, the doctor utilizes another imaging device whose imaging device has a closer focus and a larger magnification. In this way, the doctor can inspect the site in question precisely. When the doctor places the endoscope on the site to be inspected, the site to be inspected is illuminated by scattered light from the illumination device of the endoscope that passes through the tissue to be inspected.

[0008] Conventionally, for such examinations, the physician would use an endoscope with zoom optics and an adjustable focus. Such endoscopes are relatively expensive and difficult to handle. In contrast, with an endoscope equipped with the imaging system according to the present invention, the physician simply needs to switch between the two image elements.

[0009] Furthermore, for example, the product of the transmittance of the respective imaging device and the sensitivity of the corresponding imager may differ for the two imaging devices, for example by 50%, preferably 100% or even 400% of the lower of the two sensitivities. In this way, a wide dynamic range can be covered for imaging. In particular, for example, the transmittance of the imaging devices can be made different. This can be achieved, for example, by the fact that the beam splitter does not split the light beam symmetrically and / or by the fact that differently sized apertures are used in the two rear optical units. This expands the dynamic range of imaging. However, (alternatively or additionally) the sensitivity of the imager may also be different. In such a configuration, for example, the two rear optical units may not have optical refractive power. The sensitivity represents the number of charges generated per photon impinging on the imager.

[0010] Some of the advantages that may be achieved by the present invention are summarized again in the following list: It should be observed that this list is not exhaustive and that not all of these advantages need to be achieved in each embodiment.

[0011] (A) Multi-focus system The combination of a single image achieves increased depth of field without the need for any moving parts.

[0012] Typically the distance of the sensor from the objective lens is changed (alternatively, there are solutions that dynamically change the objective lens properties such as the lens distance or lens shape). A drawback of previous solutions is that only one specific focus can be set at a time. Simultaneous acquisition of several images with different foci allows for artifact-free production of a very high depth of field while allowing for very low aperture stops (which increases the overall image resolution and possibly the sensitivity of the camera system).

[0013] (B) Optical multi-zoom (multiple magnification) Typically, a multi-zoom system is achieved by dynamically changing the distance of the lens groups. In principle, this can only be achieved with high technical expenditure and is often susceptible to interference. Non-moving systems are potentially less susceptible to interference and allow finer adjustment. Furthermore, fixed zoom stages can be easily switched.

[0014] (C) HDR (High Dynamic Range) Imaging Usually, several images with different exposure steps (illuminance) are acquired for the formation of HDR images by LDR (low dynamic range) sensors (light dependent resistors). As an alternative, there are systems that exploit pixels with different exposures in the same image at the expense of resolution. In the proposed system, at a constant resolution, HDR images are generated by multiple LDR sensors in an artifact-free manner (without time shifts of objects in moving scenes).

[0015] In some embodiments of the invention, two imaging devices with suitable imaging elements are used. In some embodiments of the invention, three or more imaging devices with suitable imaging elements can also be used. For example, the light beam can be split multiple times by multiple beam splitters connected in series. [Brief description of the drawings]

[0016] [Figure 1] 1 illustrates a schematic of an imaging system according to an embodiment of the present invention; [Diagram 2] 1 illustrates, in schematic form, an endoscope equipped with an imaging system according to an embodiment of the present invention; [Diagram 3] 1 illustrates a schematic representation of an endoscopic system including an imaging system according to an embodiment of the present invention; [Figure 4] 1 shows a cross-sectional view of an imaging system according to a first embodiment of the present invention. [Diagram 5]2 shows a cross-sectional view of an imaging system according to a second embodiment of the present invention. [Figure 6] 1A-1D show front and side views of a beam splitter used in some imaging systems according to embodiments of the present invention. [Figure 7] FIG. 2 shows a front view of a beam splitter used in some imaging systems according to embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The following provides further details of this type of imaging system.

[0018] 1 shows a schematic representation of an imaging system 1 according to some embodiments of the invention. The imaging system 1 comprises two imaging devices 11 and 12 which image a respective scene in a subject space onto respective imagers (image acquisition means) 51 and 52. The imaging device 11 is composed of a front optical unit 2, a beam splitter 3 and a rear optical unit 41. The imaging device 12 is composed of the same front optical unit 2, the same beam splitter 3 and a rear optical unit 42 which is different from the rear optical unit 41.

[0019] The imaging elements 51, 52 may be semiconductor sensors such as CMOS or CCD chips. The imaging elements 51, 52 are sensitive to the visible wavelength range, in particular to three wavelength ranges 650 nm±5 nm (red), 532 nm±5 nm (green) and 460 nm±5 nm (blue), hereinafter also referred to as RGB wavelength ranges. For example, for each of the imaging elements 51, 52 in at least one of the RGB wavelength ranges, for each wavelength, the sensitivity may be higher than 50% of the maximum sensitivity of the respective imaging element. Preferably, the sensitivity in at least one RGB wavelength range is higher than 60% of the maximum sensitivity of the respective imaging element. That is, in at least one RGB wavelength range, both image acquisition means have sufficient sensitivity for image detection of suitable quality. More preferably, the sensitivity in at least one wavelength range is higher than 70% or even higher than 80%. In some embodiments, the two imaging elements 51 and 52 have the same sensitivity over at least one RGB wavelength range. Preferably, the properties described herein for at least one of the RGB wavelength ranges are applicable to all three RGB wavelength ranges.

[0020] In some embodiments, at least one of the rear optical units 41, 42 deflects the respective light bundles (e.g. by one or more mirrors, and optionally also using relay optics) such that the image planes of the two imaging devices 11, 12 lie in one plane. Thus, instead of two separate imagers, only one imager can be used, with different areas of the one imager corresponding to the two image acquisition means 51, 52.

[0021] In some embodiments, the entire imaging system 1 in the RGB wavelength range is non-dichroic. Preferably, the entire imaging system is non-dichroic over the entire visible spectrum (405 nm to 700 nm), and possibly even beyond the visible spectrum, for example up to 380 nm and 900 nm (or 800 nm or 850 nm), respectively. In particular, the beam splitter 3 may also be non-dichroic in the respective wavelength range. For the purposes of this application, the term "non-dichroic" means that for each pair of a first wavelength in one wavelength range of the RGB wavelength range and a second wavelength in another wavelength range of the RGB wavelength range, the ratio of the product of the transmittance of the first imaging device 11 for the first wavelength and the sensitivity of the first image capture means 51 for the first wavelength to the product of the transmittance of the second imaging device 12 for the first wavelength and the sensitivity of the second image capture means 52 for the first wavelength does not differ by more than 50% from the ratio of the product of the transmittance of the first imaging device 11 for the second wavelength and the sensitivity of the first image capture means 51 for the second wavelength to the product of the transmittance of the second imaging device 12 for the second wavelength and the sensitivity of the second image capture means 52 for the second wavelength. Preferably, these ratios differ by less than 25%, and more preferably the ratios for each pair of two wavelengths from the relevant wavelength ranges are equal. The reference value for the above percentages is the lesser of the two ratios, except when the two ratios are equal.

[0022] The front optical unit 2 is common to the two imaging devices 11, 12. The front optical unit 2 has a non-zero refractive power. The front optical unit 2 has a front lens that is closest to the object space. Furthermore, the front optical unit 2 can determine the cross section of the light bundle from the scene. That is, the front optical unit 2 can have an aperture function. In this way, for example, the maximum possible field of view (FOV) is determined by the front optical unit 2.

[0023] Figure 6 shows an example of a beam splitter 3. The beam splitter 3 splits the light beam intensity and directs it in different directions towards the rear optical units 41 and 42, respectively. The beam splitter 3 may be non-dichroic. It may be, for example, a semi-transparent mirror or a beam splitter cube that splits the incoming light beam at the interface 30 according to the principle of frustrated total reflection. The beam splitter 3 may split the light beam intensity equally in both directions or may direct a higher intensity in one direction than the other.

[0024] Another possible beam splitter 3 is shown in Fig. 7. This beam splitter 3 splits the light beam geometrically. In this example, a mirror 31 (e.g. a circular mirror) is arranged in the center of the light beam (preferably symmetrically). The mirror is tilted at an angle (e.g. within the range of 45°±30°) with respect to the optical axis of the front optical unit 2 so as to direct the light to the second rear optical unit 42. The mirror has a reflectivity higher than 50%, preferably higher than 75%, even more preferably higher than 95%, at least in the RGB wavelength range (preferably in the entire visible spectrum, possibly even beyond the visible spectrum as mentioned above). The reflectivity may be 100%. The mirror may at the same time be a diaphragm of the imaging device 12.

[0025] Only a part of the light beam from the front optical unit 2 is incident on the mirror 31. The area 32 of the beam splitter 3, where the remaining part of the light beam is incident, is substantially transparent. For example, the beam splitter may be glass coated with a mirror reflective layer 31. This beam splitter therefore acts as an annular diaphragm for the imaging device 11. The transmission of the area 32 in the RGB wavelength range (preferably the whole visible spectrum, possibly even beyond the visible spectrum as mentioned above) is higher than 50%, preferably higher than 75% and even more preferably higher than 95%. The transmission may even be 100%.

[0026] There are no limitations on the shape of the mirror 31. It may, for example, be a rounded shape (for example a circle or an oval). However, the mirror may also have the shape of a polygon (triangle, square, ...).

[0027] 7, the central surface 31 is reflective and the surrounding surfaces 32 are transmissive. However, in some embodiments, the central surface may alternatively be transmissive and the surrounding surfaces reflective.

[0028] The reflectance and transmittance may each have a gradient and may decrease continuously outward such that a high reflectance (or transmittance) is achieved at the center of the light bundle (e.g., greater than 90%, or even 100%) and a low reflectance (or transmittance) is achieved at the edge (e.g., less than 10%, or even 0%).

[0029] If the beam splitter 3 is dichroic, in some embodiments at least one of the two imaging devices 41, 42 may be provided with components (e.g., color filters) that compensate for the dichroism of the beam splitter 3, such that the overall imaging system 1 is non-dichroic. The beam splitter 3 may be polarization dependent or polarization independent.

[0030] The rear optical units 41, 42 are located behind the beam splitter 3 in the direction of light propagation from the front optical unit 2 to the imagers 51, 52. In some embodiments, the rear optical units 41, 42 have a non-zero refractive power, or one of the rear optical units 41, 42 has zero refractive power and the other of the rear optical units 41, 42 has a non-zero refractive power. They comprise the effective aperture of the respective imaging device 41, 42 in case the beam splitter 3 or the front optical unit 2 does not constitute the effective aperture of at least one of the imaging devices 41, 42. They may comprise lenses and / or (curved) mirrors.

[0031] The focus of one imaging device is in the range of 0-1 mm in front of the subject-side apex of the front lens ("macro focus"), while the focus of the other imaging device is in the range of 3 mm-12 mm in front of the subject-side apex of the front lens ("wide focus"). The focus refers to the intersection of the optical axis of the respective imaging device 11, 12 with the subject surface (e.g., the subject plane) that is sharply imaged on the respective imager 51, 52. For imaging means with macro focus, the distance from the focus to the entrance pupil measured at the optical axis is larger than the focal width of the imaging means, for example in the range of 2-4 times the focal width. The focal plane is perpendicular to the optical axis and may be flat or convex. For a convex focal plane, the radius of curvature must not be smaller than the radius of curvature of the front lens.

[0032] Apart from the case where the beam splitter 3 splits the light flux intensity differently and thus causes different transmittances of the two imaging devices 11, 12, and the sensitivity of the image pickup elements differs, the two rear optical units 41, 42 are responsible for the fact that the two imaging devices 11, 12 may differ by at least one optical parameter (in addition to the position of the focal point). Naturally, the division of the light flux intensity by the beam splitter 3 may also be asymmetric and the two rear optical units 41, 42 may further differ by at least one optical parameter.

[0033] The optical parameters may be, for example, the focal width of each imaging device (i.e., the distance of the focal point of each imaging device from the front focus), the focal length of each imaging device 11, 12, the maximum viewing angle of each imaging device 11, 12, the aperture aperture of each imaging device 11, 12, and / or the average transmittance of each imaging device 11, 12 in the RGB wavelength range (or the entire visible spectrum and even beyond the visible spectrum as described above).

[0034] Preferred minimum values ​​for each difference are set forth below.

[0035] Where the optical parameter is a distance of a focus from a front focus, the distance of one of the foci of the first imaging device and the second imaging device from the front focus of one of the first imaging device and the second imaging device differs by at least 25% from the distance of the other of the foci of the first imaging device and the second imaging device from the front focus of the other of the first imaging device and the second imaging device. If the optical parameter is a focal length, the focal length of the first imaging device 11 differs from the focal length of the second imaging device 12 by at least 10%, and even more preferably the difference is at least 30%, or even at least 50%. Where the optical parameter is the maximum viewing angle, the maximum viewing angle of the first imaging device 11 differs from the maximum viewing angle of the second imaging device 12 by at least 20%, and even more preferably the difference is at least 35%, or even 50%. If the optical parameter is the aperture, the surface of the aperture of the first imaging device 11 differs from the surface of the aperture of the second imaging device 12 by at least 25%, and even more preferably the difference is at least 50%, or at least 75%, or at least 100%. If the optical parameter is transmittance, the average transmittance of the first imaging device 11 in at least one of the RGB wavelength ranges (preferably all three RGB wavelength ranges or the entire visible spectrum) differs from the average transmittance of the second imaging device 12 in the respective wavelength range by at least 50%, and even more preferably the difference is at least 100%, or at least 400%. If the average sensitivity of the first image acquisition means 51 in at least one of the RGB wavelength ranges (preferably all three RGB wavelength ranges or the entire visible spectrum) differs from the average sensitivity of the second image acquisition means 52 in the respective wavelength range, the average sensitivity of the first image acquisition means 51 differs from the average sensitivity of the second image acquisition means 52 by at least 25%, even more preferably the difference is at least 50%, at least 100% or at least 400%.

[0036] The averages of each of the transmittance, sensitivity, and the product of the transmittance and sensitivity are each formed over a respective wavelength range. The nominal value of each of the above percentages is the smaller of the corresponding values ​​for the first and second imaging devices and associated imagers, respectively.

[0037] The characteristics described above for the RBG wavelength ranges of 650 nm ± 5 nm (red), 532 nm ± 5 nm (green), and 460 nm ± 5 nm (blue) are preferably also applicable to one or both of the wavelength ranges between these, 465 nm to 527 nm and 537 nm to 645 nm. Furthermore, they are preferably also applicable to at least one of the adjacent wavelength ranges above and below 380 nm to 455 nm and 655 nm to 900 nm, which also include UV or infrared light. Furthermore, these ranges may also be limited by a lower wavelength of 405 nm and an upper wavelength of 850 nm or 800 nm or 700 nm, respectively.

[0038] FIG. 2 shows an example of an imaging system 1 according to some embodiments of the present invention housed in an endoscope tip 110. The endoscope tip may be suitable for insertion into a cavity (such as a cavity of the human body). Thus, the front optical unit 2 is closer to the distal end of the endoscope tip 110 than the two rear optical units 41, 42. In the example shown in FIG. 2, the endoscope tip 110 is connected to an insertion shaft 120 of an endoscope. However, the endoscope tip 110 according to some embodiments of the present invention may also be used alone without an insertion shaft (so-called capsule endoscopy). The insertion shaft 120 may be either a rigid insertion shaft (pipe or tube) or a flexible tube. An angle segment may be provided between the endoscope tip 110 and the insertion shaft 120 (not shown) such that the endoscope tip 110 is only indirectly connected to the insertion shaft 120.

[0039] As shown in FIG. 2, when the imaging system 1 is housed in the endoscope tip 110 such that the first imaging device 11 extends parallel to the axis of the endoscope tip while the second imaging device 12 is bent relative to the axis of the endoscope tip, the first imaging device 11 preferably has a relatively large focal length and the second imaging device 12 preferably has a relatively small focal length.

[0040] In FIG. 2, the entire imaging system 1 is located inside the endoscope tip 110, but a part of the imaging system 1 may be located outside the endoscope tip 110. In this case, a relay optical system transmits the light beam between a part of the imaging system 1 located inside the endoscope tip 110 and a part of the imaging system 1 located outside the endoscope tip 110. In particular, the entire imaging system 1 may be arranged outside the endoscope tip 110. As shown in FIG. 3, in this case, the relay optical system 130 transmits the light beam from the subject space to the forward optical unit 2 outside the endoscope tip 110. As the relay optical system 130, for example, a rod optical system such as a glass fiber or Hopkins optical system is conceivable. Even though it is shown diagrammatically in FIG. 3, the endoscope tip 110, the insertion shaft 120, and the imaging system 1 may be aligned in a line, but do not have to be aligned in a line.

[0041] Figures 4 and 5 show in detail a first and a second embodiment of the imaging system 1 according to the invention. The parameters of the individual lenses, diaphragms and beam splitters are given in Tables 1 and 2 (for Figure 4) and Tables 4 and 5 (for Figure 5). The optical properties of the systems are given in Tables 3 (for Figure 4) and 6 (for Figure 5). The length values ​​in Tables 1 to 6 are given in mm. With the exception of the beam splitter 3, the optical components of the two imaging systems 1 of Figures 4 and 5 have a circular cross section in the light propagation direction. Figure 6 shows the front and side views of the beam splitter 3 for the two imaging devices. The latter is cubic in shape (i.e. square in cross section) and in the side view the partially reflecting surfaces of the beam splitter are located diagonally.

[0042] Table 7 shows the refractive index nd and Abbe coefficient vd of the types of glass used. The refractive index is given for a wavelength of 587.6 nm. The Abbe coefficient is vd=(nd-1) / (n F -n C ) where n, n F , and n C are the refractive indices of the material at the wavelengths of the Fraunhofer d, F, and C spectral lines (587.6 nm, 486.1 nm, and 656.3 nm, respectively).

[0043] The refractive elements in the imaging device 1 are not limited to spherical lenses. The lenses may be aspheric. Catadioptric elements such as curved mirrors may also be used. The lenses or mirrors may be made, for example, from glass or plastic. The lenses or mirrors may be coated. If the imaging device or at least the forward optical unit of the imaging device is housed in the tip of an endoscope, it is desirable for at least the frontmost element of the forward optical unit (e.g., the lens) to have sufficient resistance to scratches and impacts as well as resistance to the surrounding medium.

[0044] [Table 1]

[0045] [Table 2]

[0046] First imaging device: Large focal length (microscope) System aperture F / #=4 Effective focal length: 0.8670161 Total length: 14.50188 Second imaging device: Small focal length (wide-angle objective lens) System aperture F / #=4 Effective focal length: 0.5218 Total length: 13.05297 Table 3: Optical parameters of the first embodiment

[0047] [Table 3]

[0048] [Table 4]

[0049] First imaging device: Large focal length (microscope) System aperture F / #=4 Effective focal length: 0.9331866 Total length: 14.48277 Second imaging device: Small focal length (wide-angle objective lens) System aperture F / #=2.8 Effective focal length: 0.5462332 Total length: 12.33006 Table 6: Optical parameters of the second embodiment

[0050] Glass name Refractive index nd Abbe coefficient vd BSM51Y 1.60311 60.65 L-TIM28P 1.69453 30.66 N-FK51A 1.48656 84.47 N-FK58 1.456 90.9 N-LAF21 1.788 47.49 N-LASF31A 1.883 40.76 N-LASF35 2.022 29.06 N-LASF9HT 1.8502 32.17 N-SK16 1.62041 60.32 N-SK5 1.58913 61.27 N-ZK7 1.50847 61.19 S-BSM10 1.6228 57.05 S-BSM16 1.62041 60.29 S-FTM16 1.5927 35.31 S-LAH55VS 1.83481 42.74 S-LAH58 1.883 40.76 S-LAH60MQ 1.834 37.17 S-LAL14 1.6968 55.5 S-LAL58 1.6935 50.81 S-NBH56 1.85478 24.8 S-NPH1 1.80809 22.76 S-NPH3 1.95906 17.47 S-PHM52 1.618 63.4 S-TIL27 1.57501 41.5 S-TIM28P 1.69453 30.66 Table 7: Refractive index and Abbe coefficient of the types of glass used

Claims

1. A first image acquisition means; A second image acquisition means; a first imaging device configured to image a first scene in a subject space onto the first image capture means based on a light beam; a second imaging device configured to image a second scene in the subject space based on the light beam onto the second image capture means; Equipped with The first imaging device is configured to: a front optical unit including a front lens having a first non-zero refractive power and closest to the object space; a beam splitter configured to split the light beam and / or the intensity of the light beam into a first light beam that is transmitted through a peripheral portion of an optical path and a second light beam that is reflected by a reflective surface disposed in a central portion of the optical path and propagates in a direction different from the first light beam; and a first rear optical unit having a first non-zero refractive power and configured such that the first scene is imaged by the first light bundle onto the first image capture means without the need for an intermediate image; It is composed of The second imaging device is configured to: The front optical unit, the beam splitter, and a second rear optical unit configured such that the second scene is imaged by the second light bundle onto the second image acquisition means without the need for an intermediate image. It is composed of a focal point of either the first imaging device or the second imaging device is a macro focal point; the other focal point of the first imaging device and the second imaging device is a wide-angle focal point; the macro focus is within a range of 0 mm to 1 mm in front of the vertex of the front lens on the subject space side; the wide-angle focus is at least 3 mm forward of the vertex of the front lens on the subject space side; a value of at least one optical parameter of the first imaging device and / or an average sensitivity of the first image acquisition means differs from a value of said at least one optical parameter of the second imaging device and an average sensitivity of the second image acquisition means, the at least one optical parameter belongs to the group consisting of a focal width of the respective imaging device, a focal length of the respective imaging device, a maximum field of view angle of the respective imaging device, and an aperture of the respective imaging device; the focal width of each of the imaging devices is the distance of the focal point of each of the imaging devices from the front focal point of each of the imaging devices; Imaging system.

2. The imaging system of claim 1 , wherein the second posterior optical unit has a second non-zero refractive power.

3. The following conditions: a distance of the focal point of one of the first imaging device and the second imaging device from the front focal point of the one of the first imaging device and the second imaging device differs by at least 25% from a distance of the focal point of the other of the first imaging device and the second imaging device from the front focal point of the other of the first imaging device and the second imaging device; if the optical parameter is a focal length, the focal length of one of the first imaging device and the second imaging device differs from the focal length of the other of the first imaging device and the second imaging device by at least 10%; and when the optical parameter is a maximum viewing angle, the maximum viewing angle of one of the first imaging device and the second imaging device differs from the maximum viewing angle of the other of the first imaging device and the second imaging device by at least 20%. if the optical parameter is aperture, a surface of the aperture of one of the first imaging device and the second imaging device differs from a surface of the aperture of the other of the first imaging device and the second imaging device by at least 25%; for at least one wavelength range among one of the wavelength ranges of 460 nm±5 nm, 532 nm±5 nm, and 650 nm±5 nm, when the average sensitivity of one of the first image acquisition means and the second image acquisition means in said respective wavelength range differs from the average sensitivity of the other of the first image acquisition means and the second image acquisition means in said respective wavelength range, the average sensitivity of the one image acquisition means differs from the average sensitivity of the other image acquisition means by at least 25%; The imaging system of claim 1 , wherein at least one of the following is satisfied:

4. The imaging system of claim 1 , wherein the focal lengths of the first and second imaging devices are different from one another.

5. for each pair of a first wavelength in a first wavelength range or a second wavelength range or a third wavelength range and a second wavelength in the first wavelength range or the second wavelength range or the third wavelength range, a ratio of a product of a transmittance of the first imaging device for the first wavelength and a sensitivity of the first image capture means for the first wavelength to a product of a transmittance of the second imaging device for the first wavelength and a sensitivity of the second image capture means for the first wavelength does not differ by more than 50% from a ratio of a product of a transmittance of the first imaging device for the second wavelength and a sensitivity of the first image capture means for the second wavelength to a product of a transmittance of the second imaging device for the second wavelength and a sensitivity of the second image capture means for the second wavelength, the first wavelength range is 460 nm ± 5 nm; the second wavelength range is 532 nm ± 5 nm; The third wavelength range is 650 nm ± 5 nm. The imaging system of claim 1 .

6. for each wavelength in the first wavelength range, the second wavelength range and the third wavelength range, the respective value of the at least one optical parameter of the first imaging device and / or the average sensitivity of the first image acquisition means differs from the respective value of the at least one optical parameter of the second imaging device and the average sensitivity of the second image acquisition means, 6. The imaging system of claim 5.

7. 7. The imaging system of claim 6, wherein the optical parameter is a transmittance, and the beam splitter is configured such that, for at least one of the first wavelength range, the second wavelength range, and the third wavelength range, an average transmittance of the beam splitter in the respective wavelength range for one of the first light beam and the second light beam is at least 25% higher than an average transmittance of the beam splitter in the respective wavelength range for the other of the first light beam and the second light beam.

8. for at least one selected wavelength range selected from a fourth wavelength range, a fifth wavelength range, a sixth wavelength range, and a seventh wavelength range, for each pair of a third wavelength and the first wavelength in the selected wavelength range, a ratio of a product of a transmittance of the first imaging device for the first wavelength and a sensitivity of the first image capture means for the first wavelength to a product of a transmittance of the second imaging device for the first wavelength and a sensitivity of the second image capture means for the first wavelength does not differ by more than 50% from a ratio of a product of a transmittance of the first imaging device for the third wavelength and a sensitivity of the first image capture means for the third wavelength to a product of a transmittance of the second imaging device for the third wavelength and a sensitivity of the second image capture means for the third wavelength; the fourth wavelength range is 380 nm to 455 nm; the fifth wavelength range is from 465 nm to 527 nm; the sixth wavelength range is 537 nm to 645 nm; The seventh wavelength range is 655 nm to 900 nm.

7. The imaging system of claim 6.

9. for each wavelength of at least one of the fourth wavelength range, the fifth wavelength range, the sixth wavelength range and the seventh wavelength range, a respective value of the at least one optical parameter of the first imaging device and / or the average sensitivity of the first image acquisition means differs from a respective value of the at least one optical parameter of the second imaging device and the average sensitivity of the second image acquisition means, respectively.

9. The imaging system of claim 8.

10. 10. An endoscope tip portion or a capsule endoscope housing the imaging system according to any one of claims 1 to 9, wherein the front optical unit is closer to a distal end of the endoscope tip portion than the first rear optical unit and the second rear optical unit.

11. The endoscope tip portion according to claim 10, An insertion shaft for insertion into the hollow space; Equipped with The proximal end of the endoscope tip is directly or indirectly connected to the distal end of the insertion shaft. Endoscopic device.

12. an insertion shaft for insertion into the hollow space; an endoscope tip for insertion into the hollow space; An imaging system according to any one of claims 1 to 9, Relay optical system Equipped with a proximal end of the endoscope tip is directly or indirectly connected to a distal end of the insertion shaft; the relay optical system is configured to guide the light beam to the front optical unit; An endoscopic apparatus, wherein the imaging system is positioned external to the tip of the endoscope.

13. an insertion shaft for insertion into the hollow space; an endoscope tip for insertion into the hollow space; An imaging system according to any one of claims 1 to 9, Relay optical system Equipped with a proximal end of the endoscope tip is directly or indirectly connected to a distal end of the insertion shaft; the front optical unit is located at the tip of the endoscope, the relay optical system is configured to guide the light beam from the forward optical unit to the beam splitter; An endoscopic apparatus, wherein the beam splitter, the first rear optical unit, and the second rear optical unit are disposed outside the tip of the endoscope.

14. At least the first posterior optical unit and the second posterior optical unit are disposed outside the insertion shaft. The endoscope apparatus according to claim 12.

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