Objective optical system, imaging unit, endoscope and endoscope device

Abstract

Provided are an objective optical system, an imaging unit, an endoscope, and an endoscope device, whereby loss of light quantity can be reduced and an image having a wide dynamic range can be acquired.　An objective optical system 10 has a lens group 1 for forming an object image, a polarizing beam splitter 20 having an optical path dividing surface 21d for dividing into a first optical path A that intersects with the optical axis AX of the lens group 1 and a second optical path B that is present on an extension line of the optical axis AX, a first reflection surface REF1 provided on the first optical path A, a second reflection surface REF2 provided on the second optical path B, and a 1 / 4-wavelength plate 21e disposed between the polarizing beam splitter 20 and the first reflection surface REF1, and the objective optical system 10 satisfies conditional expression (1).　(1): (Tp + Ts) / (100 – Ts) ≥ 1.25. In conditional expression (1), Tp (unit%) is the transmittance of P-polarized light of the optical path division surface 21d, and Ts (unit%) is the transmittance of S-polarized light of the optical path division surface 21d.

Description

[Technical field]

[0001] The present invention relates to an objective optical system, an imaging unit, an endoscope, and an endoscope apparatus. [Background technology]

[0002] Conventionally, a technology called high dynamic range has been developed for imaging units to capture subjects with large differences in brightness. High dynamic range is a technology that creates an image with an expanded dynamic range by synthesizing multiple images with different exposures, i.e., different brightnesses. This makes it possible to obtain an image with a high dynamic range.

[0003] The endoscopic imaging system disclosed in the following Patent Document 1 generates a high dynamic range image from two images with different brightness obtained from a first frame data and two images with different brightness obtained from a second frame data. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6463573 Summary of the Invention [Problem to be solved by the invention]

[0005] It is generally known that it is preferable to combine three or more images to obtain a stable high dynamic range. In the configuration of Patent Document 1, an absorption filter such as an ND filter is used for one of the images in order to change the brightness of the two images. Therefore, the configuration of Patent Document 1 has a problem of losing the amount of light.

[0006] The present invention has been made in consideration of such problems, and aims to provide an objective optical system, an imaging unit, an endoscope, and an endoscopic device that can reduce loss of light and acquire images with a wide dynamic range. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, an objective optical system according to at least some embodiments of the present invention has a lens group that forms an object image, a polarizing beam splitter having an optical path splitting surface that splits the optical path into a first optical path that intersects the optical axis of the lens group and a second optical path that exists on an extension of the optical axis, a first reflecting surface provided on the first optical path, a second reflecting surface provided on the second optical path, and a quarter-wave plate arranged between the polarizing beam splitter and the first reflecting surface, and satisfies the following conditional formula (1). (Tp+Ts) / (100-Ts)≧1.25 (1) Where: Tp (unit: %) is the transmittance of P-polarized light at the optical path splitting surface, Ts (unit: %) is the transmittance of S-polarized light at the optical path splitting surface, It is.

[0008] Also, another imaging unit according to at least some embodiments of the present invention has the above-mentioned objective optical system and an imaging surface at the position of the formed object image, A comparison between an object image on the first optical path and an object image on the second optical path Capture two object images Single An imaging element.

[0009] Furthermore, an endoscope according to at least some embodiments of the present invention includes the imaging unit described above.

[0010] An endoscope apparatus according to at least some embodiments of the present invention includes the above-described endoscope and an image processing unit that synthesizes two object images. Effect of the Invention

[0011] According to the present invention, it is possible to provide an objective optical system, an imaging unit, an endoscope, and an endoscope apparatus that can reduce loss of light amount and acquire an image with a wide dynamic range. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram showing an objective optical system, an imaging unit, and a processor according to the first embodiment. [Diagram 2] FIG. 2 is a diagram showing the configurations of a polarizing beam splitter and an image sensor in the first embodiment. [Diagram 3] FIG. 2 is a diagram showing an imaging region of an imaging element in the first embodiment. [Figure 4] (a), (b), and (c) show the transmittance characteristics of the optical path splitting surface, respectively. [Diagram 5] 6(a) and 6(b) show other transmittance characteristics of the optical path splitting surface. [Figure 6] FIG. 11 is a diagram showing the configuration of a polarizing beam splitter in the second embodiment. [Figure 7] FIG. 11 is a diagram showing an imaging region of an imaging element in a second embodiment. [Figure 8] 10 is a flowchart showing a flow when two object images are synthesized in the second embodiment. [Figure 9] 13A and 13B are diagrams illustrating an endoscope and an endoscope apparatus according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Prior to the description of the examples, the effects of an embodiment according to a certain aspect of the present invention will be described. In addition, when specifically explaining the effects of the present embodiment, specific examples will be shown. However, as in the case of the examples described later, the exemplified aspects are merely a part of the aspects included in the present invention, and there are many variations in the aspects. Therefore, the present invention is not limited to the exemplified aspects.

[0014] (First embodiment) FIG. 1 is a diagram showing a schematic configuration of an objective optical system 10, an imaging unit 60, and a processor 3 according to the first embodiment.

[0015] The objective optical system 10 includes a lens group 1 that forms an object image, a polarizing beam splitter 20 having an optical path splitting surface 21d (FIG. 2) that splits the optical path into a first optical path A (FIG. 2) that intersects with the optical axis AX of the lens group 1 and a second optical path B that exists on an extension of the optical axis AX, a first reflecting surface REF1 (FIG. 2) provided on the first optical path A, a second reflecting surface REF2 (FIG. 2) provided on the second optical path B, and a quarter-wave plate 21e arranged between the polarizing beam splitter 20 and the first reflecting surface REF1.

[0016] The polarizing beam splitter 20 satisfies the following conditional formula (1). (Tp+Ts) / (100-Ts)≧1.25 (1) Where: Tp (unit: %) is the transmittance of P-polarized light of the optical path splitting surface 21d, Ts (unit: %) is the transmittance of S-polarized light of the optical path splitting surface 21d, It is.

[0017] The transmittance is a value for an average wavelength in the visible range when the optical axis AX is incident on the optical path splitting surface 21d at an angle of 45 degrees.

[0018] The imaging unit 60 includes an objective optical system 10 and an imaging element 22 that has an imaging surface I at the position of the formed object image and captures two object images.

[0019] 2 is a schematic diagram of the polarizing beam splitter 20 and the image sensor 22. According to a preferred embodiment of the present invention, the objective optical system 10 includes a lens group 1 for forming an image of a light beam from an object, one image sensor 22 arranged in the vicinity of an image forming position of the lens group 1, and a polarizing beam splitter 20 arranged between the lens group 1 and the image sensor 22 and having an optical path splitting surface 21d for splitting the light beam from the lens group 1 into two light beams, a reflected light beam and a transmitted light beam.

[0020] The polarizing beam splitter 20 has a first reflecting surface REF1 for folding back and reflecting the light beam reflected by the optical path splitting surface 21d, and a second reflecting surface REF2 for reflecting the light transmitted through the optical path splitting surface 21d.

[0021] A first object image (image A) is formed on a first light receiving area 22a (FIG. 3) of the image sensor 22 by a light beam reflected by the first reflecting surface REF1 via the optical path splitting surface 21d. A second object image (image B) is formed on a second light receiving area 22b (FIG. 3) of the image sensor 22 that is different from the first light receiving area 22a (FIG. 3) by a light beam reflected by the second reflecting surface REF2.

[0022] 1 includes a pre-processing unit 33 which photoelectrically converts the first object image and the second object image and outputs them as a first imaging signal and a second imaging signal, respectively. The processor 3 will be described later.

[0023] The configuration of the polarizing beam splitter 20 will be described with reference to Fig. 2. The polarizing beam splitter 20 of this embodiment is configured to split a light beam by utilizing polarized light.

[0024] The light emerging from the lens group 1 enters the polarizing beam splitter 20. The polarizing beam splitter 20 splits the subject image into two object images by the optical path splitting surface 21d. An image sensor 22 is disposed on the exit side (image surface side) of the polarizing beam splitter 20 to capture the two object images formed and obtain two images.

[0025] 2, the polarizing beam splitter 20 has an object-side prism 21a, an image-side prism 21c, a mirror 21b, and a quarter-wave plate 21e. The object-side prism 21a (object-side prism) and the image-side prism 21c (image-side prism) both have an optical path splitting surface 21d that is inclined at 45 degrees with respect to the optical axis AX.

[0026] The optical path splitting surface 21d of the object-side prism 21a is formed of a polarization splitting film. The object-side prism 21a and the image-side prism 21c are in contact with each other via the polarization splitting films that are the optical path splitting surfaces 21d, thereby constituting the polarizing beam splitter 20.

[0027] The mirror 21b is provided near the end face of the prism 21a on the object side via a quarter-wave plate 21e. The image sensor 22 is attached to the end face of the prism 21c on the image side via a cover glass CG. I is an image forming surface (imaging surface).

[0028] The subject image from the lens group 1 is separated into P-polarized transmitted light and S-polarized reflected light by the optical path splitting surface 21d of the prism 21a on the object side, and is separated into two object images: an object image on the reflected light side and an object image on the transmitted light side.

[0029] The transmittance characteristics of the optical path splitting surface 21d will be described later.

[0030] The S-polarized object image is reflected by optical path splitting surface 21d to the opposite side to image sensor 22, passes through optical path A, and is reflected by first reflecting surface REF1 of mirror 21b and folded back towards image sensor 22. The folded object image passes through quarter-wave plate 21e again, whereby the polarization direction is rotated by 90°, and passes through optical path splitting surface 21d to be formed on image sensor 22 as low-exposure image A (FIG. 3).

[0031] The P-polarized object image passes through the B optical path that passes through the optical path splitting surface 21d, is reflected by the second reflecting surface REF2 provided on the transmission side of the optical path splitting surface 21d of the image-side prism 21c that bends vertically back toward the image sensor 22, and is formed as a high-exposure B image (Figure 3) on the image sensor 22.

[0032] Basically, it is desirable that the reflectance of the first reflecting surface REF1 and the reflectance of the second reflecting surface REF2 are high. Furthermore, the reflectance may be finely adjusted in order to finely adjust the light amount of the different exposure images.

[0033] In this manner, the object-side prism 21a and the image-side prism 21c separate the subject image into two object images with different brightnesses due to different exposure amounts.

[0034] FIG. 3 is a diagram showing a first light receiving region (effective pixel region) 22a and a second light receiving region (effective pixel region) 22b of the image sensor 22. As shown in FIG.

[0035] As shown in FIG. 3, the image sensor 22 has two light receiving areas (effective pixel areas) 22a and a second light receiving area (effective pixel area) 22b provided within the entire pixel area of ​​the image sensor 22 in order to individually receive and capture two object images having different brightnesses.

[0036] The first light receiving region 22a and the second light receiving region 22b are arranged to coincide with the image forming planes of the two object images so as to capture the two object images.

[0037] A correction pixel area 22c is provided around the first light receiving area 22a and the second light receiving area 22b to correct the geometric misalignment of the two divided object images. The geometric misalignment of the object images is eliminated by suppressing manufacturing errors in the correction pixel area 22c and performing correction through image processing in an image correction processing unit 32a (FIG. 1) described later.

[0038] As described above, in this embodiment, a quarter-wave plate 21e for changing the phase of the light beam reflected by the optical path splitting surface 21d is provided between the object-side prism 21a and the first reflecting surface REF1, and the light beam reflected by the first reflecting surface REF1 passes through the quarter-wave plate 21e and is imaged on the first light-receiving region 22a of the image sensor 22 via the polarizing beam splitter 20. This makes it possible to split the light beam and acquire the first object image while using a more effective amount of light.

[0039] Moreover, in this embodiment, the light beam transmitted through the optical path splitting surface 21d is reflected by the second reflecting surface REF2 provided on the transmission side of the optical path splitting surface 21d of the image-side prism 21c that perpendicularly turns back toward the image sensor 22, and is imaged on the second light receiving region 22b of the image sensor 22. This makes it possible to split the light beam and acquire the second object image while using a more effective amount of light.

[0040] The ID memory 40 shown in FIG. 1 stores different exposure amount information for the first object image and the second object image in the image sensor 22.

[0041] Next, a description will be given of the processor 3 (FIG. 1). The processor 3 has a control unit 31, an image processing unit 32, a pre-processing unit 33, and a CCD driving unit .

[0042] The control unit 31 controls various circuits including a pre-processing unit 33, a power supply circuit, a signal processing circuit, and a CCD driving unit .

[0043] The pre-processing unit 33 receives the image signal (image signal related to two object images with different exposure amounts) from the image sensor 22 and performs predetermined pre-signal processing. The pre-processing unit 33 is composed of a known signal amplifier, a process circuit, an A / D converter, a white balance circuit, etc.

[0044] The image processing unit 32 has an image correction processing unit 32a that performs image correction, an image synthesis processing unit 32b that performs image synthesis processing to synthesize two corrected images, and an image output unit 32c that outputs the synthesized image to the display device 5.

[0045] The image correction processing unit 32a corrects the images relating to the two object images formed on the first light receiving region 22a and the second light receiving region 22b of the image sensor 22, respectively, so that the relative positions, angles, and magnifications are approximately identical.

[0046] The CCD driving unit 34 drives the image pickup device 22 in the endoscope 2 (FIG. 9).

[0047] Geometric differences may occur when the subject image is split into two and each is formed on the image sensor 22. That is, the object images formed on the first light receiving region 22a and the second light receiving region 22b (FIG. 3) of the image sensor 22 may have relative magnification deviation, position deviation, angle (i.e., rotational direction deviation), and the like.

[0048] It is difficult to completely eliminate these differences during manufacturing, etc. If the amount of deviation becomes large, the composite image may become a double image, or unnatural brightness unevenness may occur. For this reason, the image correction processing unit 32a corrects the above-mentioned geometric differences and brightness differences.

[0049] The image synthesis processing unit 32b performs post-stage image processing such as synthesis of two images into one image, color matrix processing, edge enhancement, gamma correction, etc. The image output unit 32c outputs the image that has been subjected to the post-stage image processing. The image output from the image output unit 32c is output to the image display unit 5.

[0050] In this embodiment, two images with different exposure amounts are synthesized using the configuration specifically described below. By satisfying the following conditional expression (1), the dynamic range can be expanded without losing the amount of light. (Tp+Ts) / (100-Ts)≧1.25 (1)

[0051] The dynamic range can be expanded by combining images with different exposures. If conditional expression (1) is satisfied, the dynamic range can be expanded by 25% or more. This makes it possible to obtain images with different exposures without losing light. Compared to when the dynamic range is not expanded, it becomes possible to resolve structures in dark areas that are buried in noise in particular.

[0052] Furthermore, since no element for reducing the amount of light is required, manufacturing costs can be reduced and space can be increased.

[0053] Furthermore, it is preferable to replace conditional expression (1) with conditional expressions (1'), (1'', and (1''').

[0054] (Tp+Ts) / (100-Ts)≧1.5 (1') This has the effect of reducing noise in dark areas of the image (dark noise).

[0055] (Tp+Ts) / (100-Ts)≧2 (1'') This makes it possible to sufficiently reduce halation in bright areas of an image.

[0056] (Tp+Ts) / (100-Ts)≧3 (1''') This provides the effect of sufficiently reducing noise in dark areas of an image.

[0057] Figure 4(a), (b), and (c) are respectively optical path 4 shows the transmittance characteristics of dividing surface 21d.

[0058] Figure 4(a) shows the dynamic range expansion ratio (expanded D range ratio) when it is 1.0x. optical path The P-polarized light transmittance and the S-polarized light transmittance at the dividing surface 21d are shown.

[0059] Figure 4(b) shows the dynamic range expansion ratio (expanded D range ratio) when it is 1.25 times. optical path The P-polarized light transmittance and the S-polarized light transmittance at the dividing surface 21d are shown.

[0060] Figure 4(c) shows the dynamic range expansion ratio (expanded D range ratio) when it is 1.5 times. optical path The P-polarized light transmittance and the S-polarized light transmittance at the dividing surface 21d are shown.

[0061] Figure 5(a) and (b) are respectively optical path 4 shows other transmittance characteristics of the dividing surface 21d.

[0062] Figure 5(a) shows the dynamic range expansion ratio (expanded D range ratio) when it is 2.0 times. optical path The P-polarized light transmittance and the S-polarized light transmittance at the dividing surface 21d are shown.

[0063] Figure 5(b) shows the dynamic range expansion ratio (expanded D range ratio) when it is 3.0 times. optical path The P-polarized light transmittance and the S-polarized light transmittance at the dividing surface 21d are shown.

[0064] The specifications for each expanded D range ratio are shown in Table 1 below. In Table 1, the units for transmittance and reflectance are %, and the units for A image intensity and B image intensity are arbitrary relative units.

[0065] [Table 1]

[0066] In a preferred aspect of this embodiment, it is desirable to satisfy the following conditional expression (2). 80≦Tp (2)

[0067] Conditional expression (2) is optical path An appropriate value for the P-polarized light transmittance at the dividing surface 21d is defined. By satisfying the conditional expression (2), the loss of the light amount can be further reduced, and the light amount can be effectively utilized.

[0068] In addition, in a preferred aspect of this embodiment, it is desirable that the object image on the first optical path A and the object image on the second optical path B are formed on the same plane I (imaging plane) on the exit side of the polarizing beam splitter 20.

[0069] This makes it possible to obtain images with different exposure amounts using a single imaging element 22 (single plate).

[0070] Second embodiment 6 is a diagram showing the configuration of a polarizing beam splitter 120 included in an objective optical system according to the second embodiment. The same components as those in the first embodiment are given the same reference numerals, and duplicated explanations will be omitted.

[0071] This embodiment is configured to achieve the high dynamic range as described above in the first embodiment, and further increase the depth of field. The device configuration is the same as that shown in Fig. 1. However, the processing flow of the obtained object image is different from that of the above-mentioned embodiment.

[0072] In this embodiment, the optical path length of the first optical path A1 from the optical path splitting surface 21d to the plane I (imaging plane) and the optical path length of the second optical path B1 from the optical path splitting surface 21d to the plane I are different.

[0073] 6 shows the configuration of the polarizing beam splitter 120 in this embodiment. The object-side prism 221a and the image-side prism 221c split the subject image into two optical images with different focus positions, i.e., object images. The polarizing beam splitter 120 is configured so that the optical path length on the reflected light side from the optical path splitting surface 21d to the image sensor 22 is shorter (smaller) than the optical path length (glass path length) on the transmitted light side from the optical path splitting surface 21d to the image sensor 22.

[0074] 7, the first light receiving region 222a and the second light receiving region 222b are arranged to coincide with the image forming plane of the object image in order to capture two object images. In the image sensor 22, the focus position of the first light receiving region 222a is shifted (displaced) relatively to the near point side with respect to the second light receiving region 222b, and the focus position of the second light receiving region 222b is shifted relatively to the far point side with respect to the first light receiving region 222a. This allows two object images with different focuses to be formed on the light receiving surface of the image sensor 22.

[0075] The image sensor 22 receives light from two object images AA and BB, which are focused on different positions, and captures them separately. For example, the near point side is an AA image with low exposure, and the far point side is a BB image with high exposure.

[0076] In addition, by making the refractive indexes of the glass materials of the object-side prism 221a and the image-side prism 221c different, the optical path length to the image sensor 22 can be changed to relatively shift the focal positions for the first light-receiving area 222a and the second light-receiving area 222b.

[0077] The image synthesis processing unit 32b (FIG. 1) of this embodiment has a function of expanding the depth of field in addition to the function of expanding the high dynamic range described above. The image synthesis processing unit 32b generates a synthetic image by selecting an image with a relatively high contrast in a corresponding predetermined area between two images. In other words, the contrast in each of the spatially identical pixel areas in the two images is compared, and the pixel area with the relatively high contrast is selected to generate a synthetic image as a single image synthesized from the two images.

[0078] The image output unit 32c outputs the image that has been subjected to the post-stage image processing. The image output from the image output unit 32c is output to the image display unit 5.

[0079] This makes it possible to obtain images of two objects with different focal lengths, and to synthesize these images in the image synthesis processing unit 32d to obtain a synthetic depth of field. Distant observation is suitable for screening a wide area in an endoscopic examination, while close observation is suitable for observing the details of a lesion or for diagnosing it.

[0080] Here, it is preferable to set the dark side of the near point side and the bright side of the far point side as the near point and the bright side as the far point, because the near point side is brighter than the far point side and the far point side is darker than the near point side.

[0081] Next, FIG. 8 is a flowchart showing a flow when two object images are combined to extend the depth of field in this embodiment.

[0082] In step S101, the image correction processing unit 32a performs correction processing for two images, one for a far point image and one for a near point image, which are different in focus and are acquired by the image sensor 22. That is, the two images are corrected according to preset correction parameters so that the relative positions, angles, and magnifications of the optical images of the two images become substantially the same, and the corrected image is output to the image synthesis processing unit 32b. Note that the difference in brightness and color between the two images may be corrected as necessary.

[0083] In step S102, the two images that have been subjected to the correction process are synthesized by the image synthesis processing unit 32b. At this time, the contrast values ​​are calculated and compared in the corresponding pixel regions of the two perspective and near images.

[0084] In step S103, it is determined whether or not there is a difference of a predetermined value or more between the compared contrast values. If there is a difference in contrast, the process proceeds to step S105, where an area with a high contrast value is selected and combined.

[0085] Here, if the difference in the contrast values ​​to be compared is small or almost the same, it will cause instability in the process of selecting one of the two images, near or far. For example, if there is signal fluctuation such as noise, it will cause problems such as discontinuous areas appearing in the composite image or the subject image that is originally resolved becoming blurred.

[0086] Therefore, the process proceeds to step S104, where weighting is performed. In step S104, if the contrast values ​​in the pixel region for which contrast comparison is performed are almost the same in the two images, one of the pixels is weighted, and the weighted images are added together to eliminate instability in image selection. In step 105, a pixel region with a high contrast value is selected and image synthesis is performed.

[0087] Thus, according to this embodiment, in both close-up and far-away observation, it is possible to obtain an image with an extended depth of field while preventing discontinuous areas from appearing in the composite image or blurring of the optical image due to noise, etc.

[0088] By adopting such a configuration, it is possible to achieve a high dynamic range and to expand the depth of field without reducing the resolution even when an image sensor with a larger number of pixels is used.

[0089] Numerical examples of the lens group 1 will now be described.

[0090] (Numerical Example)

[0091] Lens group 1 consists of, in order from the object side, a plano-concave negative lens L1 with its flat surface facing the object side, a parallel plate L2, a biconcave negative lens L3, a positive meniscus lens L4 with its convex surface facing the object side, a positive meniscus lens L5 with its convex surface facing the object side, a biconvex positive lens L6, a negative meniscus lens L7 with its convex surface facing the image side, an aperture stop S, a biconvex positive lens L8, a biconvex positive lens L9, and a negative meniscus lens L10 with its convex surface facing the image side.

[0092] Here, the negative lens L3 and the positive meniscus lens L4 are cemented together, the positive lens L6 and the negative meniscus lens L7 are cemented together, and the positive lens L9 and the negative meniscus lens L10 are cemented together.

[0093] A polarizing beam splitter 20 is disposed on the image side of the lens group 1. In the prism in the polarizing beam splitter 20, the optical path is bent at the optical path splitting surface. The parallel plate L2 is a filter coated to cut a specific wavelength, for example, 1060 nm for a YAG laser, 810 nm for a semiconductor laser, or the infrared range. I is the image plane (imaging plane).

[0094] Numerical data for each of the above examples is shown below. Symbols: r is the radius of curvature of each lens surface, d is the distance between each lens surface, nd is the refractive index of the d-line of each lens, νd is the Abbe number of each lens, FNO is the F-number, and ω is the half angle of view. Also, back focus fb is the distance from the optical surface closest to the image side to the paraxial image surface converted into air. Total length is the distance from the lens surface closest to the object side to the optical surface closest to the image side (not converted into air) plus the back focus. The aperture is the aperture stop.

[0095] Numerical examples Unit: mm Surface Data Surface number rd nd νd 1 ∞ 0.49 1.88300 40.76 2 1.812 0.79 3 ∞ 0.84 1.52100 65.12 4 ∞ 0.34 5 -4.881 0.56 1.88300 40.76 6 1.866 2.13 1.84666 23.78 7 77.332 Variable 8 2.010 0.81 1.48749 70.23 9 2.149 Variable 10 3.354 1.13 1.64769 33.79 11 -1.665 0.32 2.00330 28.27 12 -9.987 0.04 13(Aperture) ∞ 0.56 14 512.363 0.95 1.69895 30.13 15 -3.552 0.36 16 9.128 0.94 1.48749 70.23 17 -2.180 0.39 1.92286 18.90 18 -4.093 4.59 19 (imaging surface) ∞ Various data Focal length 1.00 FNO. 3.58 Angle of view 2ω 144.9 fb (in air) 4.59 Overall length (in air) 17.15 d7 0.47 d9 1.43

[0096] Third embodiment 9 shows the configuration of an endoscope 2 and an endoscope device 1 according to a third embodiment. This embodiment provides an endoscope 2 and an endoscope device 1 that reduce loss of light amount, expand the dynamic range, and also expand the depth of field.

[0097] The endoscope 2 has the imaging unit 60 described in the first embodiment.

[0098] The endoscope device 1 includes an endoscope 2 and an image processor 32 that synthesizes two object images.

[0099] As shown in Figure 9, the endoscopic device 1 of the third embodiment includes an endoscope 2, a processor 3 to which the endoscope 2 is detachably connected and which performs predetermined signal processing, a light source device 4 to which the endoscope 2 is detachably connected and which supplies illumination light to the endoscope 2, and a display device 5 which displays the image signal generated by the processor 3 as an endoscopic image.

[0100] The endoscope 2 has a long and thin insertion section 6 to be inserted into a body cavity, an operation section 7 provided at the rear end of the insertion section 6, and a universal cord 8 extending from the operation section 7. The universal cord 8 branches into a light guide cord 9 and a signal cord (signal cable) 10a near its base end or midway.

[0101] A light source connector 11 at the end of the light guide cord 9 is detachably connected to the light source device 4, and a signal connector 12 at the end of the signal cord 10a is detachably connected to the processor 3.

[0102] Further, the signal connector 12 is provided with an ID memory 40 which is a storage unit for storing individual information for each endoscope 2, for example, individual information relating to the polarizing beam splitter 20 and the image pickup element 22.

[0103] A light guide 13 for transmitting illumination light is inserted into the insertion portion 6, the operation portion 7, and the universal cord 8. By connecting the light source connector 11 to the light source device 4, illumination light from the light source device 4 is transmitted through the light guide 13, and the transmitted illumination light is emitted from a light guide tip surface 13a attached to an illumination window provided in the tip portion 14 of the insertion portion 6.

[0104] In addition, a connector combining the light source connector 11 and the signal connector 12 may be connected to the light source device 4, and the signal from the signal connector 12 may be exchanged with the processor 3 via a cable connecting the light source device 4 and the processor 3.

[0105] An observation window (imaging window) is provided adjacent to the illumination window in the tip portion 14, and the observation window is provided with an imaging unit 60 including an objective optical system 1 that captures an optical image of a subject such as an illuminated affected area (see FIG. 1).

[0106] The imaging element 22 is configured by, for example, a CCD image sensor, and is connected to the processor 3 via a cable inserted into the insertion portion 6 and the universal cord 8 and then via the signal connector 12 .

[0107] In addition, as described above, in this embodiment, the image sensor 22 is configured to form a first object image and a second object image, which are separate optical images, in predetermined areas corresponding to each object image on the same imaging surface of the CCD.

[0108] In this embodiment, the polarizing beam splitter 20 stores in the ID memory 40 information on the difference in exposure between the first object image with a low exposure amount and the second object image with a high exposure amount.

[0109] In addition, the control unit 31 controls the various circuits within the processor 3 as described above, and when the endoscope 2 is connected to the processor 3, obtains imaging position information and exposure amount difference information, which are individual information of the endoscope 2, stored in the ID memory 40 in the signal connector 12.

[0110] As described above, this embodiment provides an endoscope and an endoscope apparatus that reduce loss of light amount and expand the dynamic range.

[0111] Furthermore, in the third embodiment, by using the polarizing beam splitter 120 described in the second embodiment, it is possible to obtain an endoscope and an endoscope apparatus that reduce loss of light, expand the dynamic range, and also expand the depth of field.

[0112] The objective optical system, imaging unit, endoscope, and endoscope apparatus described above may satisfy a plurality of configurations at the same time. This is preferable for obtaining a good endoscope apparatus. Furthermore, the combination of preferable configurations is arbitrary. Furthermore, for each conditional expression, only the upper limit or lower limit of the numerical range of the more restrictive conditional expression may be limited.

[0113] Various embodiments of the present invention have been described above, but the present invention is not limited to these embodiments. Within the scope of the spirit of the present invention, embodiments that are formed by appropriately combining the configurations of these embodiments also fall within the scope of the present invention. [Industrial Applicability]

[0114] INDUSTRIAL APPLICABILITY As described above, the present invention is suitable for an objective optical system, an imaging unit, an endoscope, and an endoscope apparatus which reduce loss of light amount and expand the dynamic range. [Explanation of symbols]

[0115] 1 Endoscopic device 2 Endoscope 3 Processors 4 Light source device 5 Display device 6 Insertion section 7 Control section 8 Universal Code 9 Light Guide Cord 10a Signal Code 10 Objective optical system 11 Light source connector 12 Signal Connector 13 Light Guide 13a Light guide tip surface 14 Tip 20, 120 Polarizing Beam Splitter 21a, 221a Object side prism 21c, 221c Image side prism 21b Mirror 21e 1 / 4 wave plate AX optical axis 21d Optical path splitting plane REF1 1st reflective surface REF2 2nd reflective surface 22 Image sensor 22a, 222a 1st light receiving area 22b, 222b second light receiving area 31 Control Unit 32 Image processing section 32a Image correction processing unit 32b Image synthesis processing unit 32c Image output section 33 Pretreatment section 34 CCD drive 40 ID Memory 60 Imaging unit A, A1 1st optical path B, B1 2nd optical path I plane, imaging surface

Claims

1. A lens group that forms an object image; a polarizing beam splitter having an optical path splitting surface that splits the optical path into a first optical path that intersects with an optical axis of the lens group and a second optical path that exists on an extension of the optical axis; a first reflecting surface provided on the first optical path; a second reflecting surface provided on the second optical path; a quarter-wave plate disposed between the polarizing beam splitter and the first reflecting surface; An objective optical system that satisfies the following condition (1): (Tp+Ts) / (100-Ts)≧1.25 (1) Where: Tp (unit: %) is the transmittance of P-polarized light of the optical path splitting surface, Ts (unit: %) is the transmittance of S-polarized light of the optical path splitting surface, It is.

2. 2. The objective optical system according to claim 1, which satisfies the following condition (2): 80≦Tp (2)

3. 3. The objective optical system according to claim 1, wherein the object image on the first optical path and the object image on the second optical path are formed on the same plane.

4. 4. The objective optical system according to claim 3, wherein an optical path length of the first optical path from the optical path splitting surface to the flat surface is different from an optical path length of the second optical path from the optical path splitting surface to the flat surface.

5. The objective optical system according to claim 3 or 4; an imaging unit having an imaging surface at the position of the formed object image, and a single imaging element configured to capture two object images, the object image on the first optical path and the object image on the second optical path.

6. An endoscope comprising the imaging unit according to claim 5 .

7. The endoscope according to claim 6 , and an image processing unit that combines the two object images.

Images