Image transmission unit, optical device, and method for manufacturing image transmission unit

Abstract

An image transmission unit (1) comprises: a single objective lens (2) consisting of a single lens formed as a spherical segment having a flat surface (2a) and a convex spherical surface (2b); an image transmission body (3) that is disposed on the convex spherical surface (2b) side of the objective lens (2); and a single holding member (4) that holds both the objective lens (2) and the image transmission body (3). The objective lens (2) and the image transmission body (3) satisfy expression (1). Light that passes through the flat surface (2a) includes light that passes through the outermost circumference of the image transmission body (3). r is the radius of the objective lens (2), n is the refractive index of the objective lens (2), and d is the radius of the image transmission body (3). (1): r / n < d ≤ r

Description

Image transmission unit, optical device, and method of manufacturing image transmission unit

[0001] The present invention relates to an image transmission unit, an optical device, and a method for manufacturing an image transmission unit.

[0002] Conventionally, optical units have been known that include multiple sagittal lenses and a cylindrical holding member that holds the multiple sagittal lenses (see, for example, Patent Document 1). A sagittal lens is a lens with a three-dimensional shape formed by cutting a sphere along a single plane. The use of sagittal lenses makes it easy to reduce the diameter of the optical unit, and optical units suitable for use as objective optical systems in small-diameter endoscopes can be easily manufactured.

[0003] International Publication No. 2021 / 255929

[0004] The image of an object formed by the optical unit is transmitted by an image transmitter such as a fiber bundle or a relay optical system. To increase the resolution of the image transmitted by the image transmitter, it is desirable for the image height to be large and for the effective radius of the image transmitter to be correspondingly large. However, in the optical unit of Patent Document 1, the presence of the second aspheric lens makes the image height small relative to the diameter of the aspheric lens, making it difficult to increase the image height. Furthermore, in Patent Document 1, the optical unit and image transmitter are inserted into a tubular member. In other words, the dual arrangement of the holding member and tubular member increases the overall outer diameter.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide an image transmission unit, an optical device, and a method for manufacturing an image transmission unit that can achieve high resolution despite its small diameter.

[0006] One aspect of the present invention is an image transmission unit comprising a single objective lens consisting of a single lens formed into a spherical depression having a flat surface and a convex spherical surface, an image transmitter disposed on the convex spherical surface side of the objective lens, and a single holding member that holds both the objective lens and the image transmitter, wherein the objective lens and the image transmitter satisfy the following formula (1), and light passing through the flat surface includes light passing through the outermost periphery of the image transmitter: r / n<d≦r (1), where r is the radius of the objective lens, n is the refractive index of the objective lens, and d is the radius of the image transmitter.

[0007] Another aspect of the present invention is an optical instrument comprising: a single objective lens consisting of a single lens formed into a spherical depression having a flat surface and a convex spherical surface; an image transmitting body arranged on the convex spherical surface side of the objective lens; and a single holding member for holding both the objective lens and the image transmitting body; and an optical element arranged on the side of the image transmitting body opposite the objective lens, wherein the objective lens and the image transmitting body satisfy the following formula (1), and light passing through the flat surface includes light passing through the outermost periphery of the image transmitting body: r / n<d≦r (1), where r is the radius of the objective lens, n is the refractive index of the objective lens, and d is the radius of the image transmitting body.

[0008] Another aspect of the present invention is a method for manufacturing an image transmission unit, which includes inserting a single spherical lens into a cylindrical holding member, inserting an image transmission body into the holding member, forming a flat surface on the spherical lens by polishing the end of the holding member and the spherical lens, and positioning the spherical lens with the flat surface formed and the image transmission body relative to each other in a position where light passing through the flat surface includes light passing through the outermost periphery of the image transmission body.

[0009] According to the present invention, it is possible to achieve high resolution despite the small diameter.

[0010] 1A is a longitudinal sectional view showing the configuration of an image transmission unit according to a first embodiment of the present invention; FIG. 1B is a front view showing the tip surface of the image transmission unit of FIG. 1A; FIG. 1C is a view explaining the image height of an objective lens in the image transmission unit of FIG. 1A; FIG. 1D is a view explaining the image height of a conventional objective lens including two aspheric lenses; FIG. 1E is a view explaining formula (2); FIG. 1F is a longitudinal sectional view of an example of an image transmission unit including a spacer; FIG. 1G is a longitudinal sectional view of another example of an image transmission unit including a spacer; FIG. 1H is a view explaining step S1 of a method for manufacturing an image transmission unit; FIG. 1I is a view explaining step S2 of a method for manufacturing an image transmission unit; FIG. 1I is a view explaining step S3 of a method for manufacturing an image transmission unit; FIG. 1I is a view explaining step S4 of a method for manufacturing an image transmission unit; FIG. 1I is a view explaining step S5 of a method for manufacturing an image transmission unit; FIG. 1I is a longitudinal sectional view showing the configuration of an image transmission unit according to a second embodiment of the present invention; FIG. 1I is a view explaining the configuration of an example of an optical device according to a third embodiment of the present invention; FIG. 1I is a view explaining the configuration of another example of an optical device according to the third embodiment of the present invention; FIG. 1I is a front view showing the tip surface of the optical device of FIGS. 7A and 7B; FIG. 1I is a view explaining the configuration of an example of a system including the optical device of FIGS. 7A and 7B; FIG. 1I is a view explaining step S6 of a method for manufacturing an optical device. It is a diagram explaining step S21 of the manufacturing method of the optical device. It is a diagram explaining step S31 of the manufacturing method of the optical device. It is a diagram explaining steps S4 and S5 of the manufacturing method of the optical device. It is a configuration diagram of the optical device related to the fourth embodiment of the present invention. It is a longitudinal sectional view showing the configuration of a conventional image transmission unit.

[0011] First Embodiment An image transmission unit according to a first embodiment of the present invention will be described with reference to the drawings. As shown in Figures 1A and 1B, an image transmission unit 1 according to this embodiment includes a single objective lens 2, an image transmitter 3, and a single cylindrical holding member 4 that holds both the objective lens 2 and the image transmitter 3. The image transmission unit 1 is long, and the objective lens 2 and the image transmitter 3 are located at the distal end and proximal end of the image transmission unit 1, respectively.

[0012] The objective lens 2 is composed of a single lens formed in a spherical cavity having a flat surface 2a and a convex spherical surface 2b, and does not include any other lenses. A spherical cavity is a three-dimensional shape formed by cutting a sphere with a single plane. Therefore, the surface of the objective lens 2 consists of a circular flat surface 2a and a convex spherical surface 2b. The flat surface 2a is located at the tip and faces the object when the image transmission unit 1 is in use. Preferably, the objective lens 2 is larger than a hemisphere, and the center of curvature of the convex spherical surface 2b is located inside the objective lens 2. The objective lens 2 has an optical axis A that passes through the center of the flat surface 2a and is perpendicular to the flat surface 2a (see FIG. 2A). The objective lens 2 is formed from a glass material commonly used for optical lenses, such as sapphire or BK7.

[0013] The objective lens 2 may be a perfect sagittal or a shape close to a sagittal. That is, the flat surface 2a may be a perfect flat surface, and the convex spherical surface 2b may be a perfect spherical surface. Alternatively, the flat surface 2a and the convex spherical surface 2b may have deviations from a perfect flat surface and a perfect spherical surface, respectively, as long as they satisfy the optical performance required for the image transmission unit 1. The deviations include, for example, wear, defects, deformation, and the like that may occur during the manufacturing process of the image transmission unit 1.

[0014] The image transmitter 3 is an optical member that is disposed on the side (proximal end side) of the convex spherical surface 2b of the objective lens 2 and extends in the longitudinal direction of the holding member 4. One example of the image transmitter 3 is a fiber bundle having multiple optical fibers. Another example of the image transmitter 3 is a relay optical system consisting of one or more lenses.

[0015] The holding member 4 is a cylindrical member that is open at both ends and preferably has a constant inner diameter φ along its entire length. The holding member 4 is preferably a round pipe that has a circular cross section along its entire length. The holding member 4 is made of a hard material such as metal or synthetic resin, and is preferably made of a metal such as stainless steel or an aluminum alloy.

[0016] The holding member 4 accommodates the objective lens 2 and the image transmitter 3 therein, and the objective lens 2 and the image transmitter 3 are disposed on the distal end and proximal end sides, respectively, of the holding member 4. The flat surface 2a is disposed on the same plane as the annular distal end surface 4a of the holding member 4, and the optical axis A coincides with the central axis of the holding member 4. When the image transmitter 3 is formed of a single optical member (for example, when the image transmitter 3 is a fiber bundle), only the distal end portion of the image transmitter 3 may be held within the holding member 4.

[0017] As shown in FIG. 2A , the convex spherical surface 2b contacts the inner surface 4b of the holding member 4, and the objective lens 2 is fixed to the holding member 4 by friction between the convex spherical surface 2b and the holding member 4. The inner diameter φ of the holding member 4 is equal to or less than 2×r, which is the diameter of the objective lens 2, and preferably slightly smaller than 2×r, where r is the radius of the objective lens 2 (i.e., the radius of curvature of the convex spherical surface 2b). This allows the objective lens 2 to be fixed to the holding member 4 by friction simply by press-fitting the objective lens 2 into the holding member 4. To prevent damage to the objective lens 2 during press-fitting, it is preferable to satisfy the relationship 0.8×2r<φ≦2r. The holding member 4 may have a shape other than a cylinder, as long as it can hold the objective lens 2 by friction. For example, it may be a rectangular pipe with a polygonal cross section.

[0018] The image transmitter 3 has a tip surface 3a facing the convex spherical surface 2b. The tip surface 3a is located at or near the focal plane P of the objective lens 2, and is separated from the convex spherical surface 2b by a predetermined distance WD in the direction along the optical axis A. The light emitted from the convex spherical surface 2b toward the image transmitter 3 includes expanded light that expands in the radial direction. Because the tip surface 3a is separated from the convex spherical surface 2b by the predetermined distance WD, the expanded light reaches the outermost periphery of the tip surface 3a or nearby, and the light passing through the flat surface 2a includes light that passes through the outermost periphery of the image transmitter 3.

[0019] The objective lens 2 and the image transmitter 3 satisfy the following formula (1): r / n<d≦r (1), where r is the radius of the objective lens 2 (the radius of curvature of the convex spherical surface 2b), n is the refractive index of the objective lens 2, and d is the radius of the image transmitter 3 (specifically, the effective radius of the tip surface 3a). Preferably, the outer diameter of the image transmitter 3 is equal to or approximately equal to the outer diameter of the objective lens 2.

[0020] In order to increase the resolution of the image transmitted by the image transmitter 3, it is preferable that the radius d of the image transmitter 3 is large. For example, if the image transmitter 3 is a fiber bundle, the larger the radius d, the greater the number of optical fibers constituting the fiber bundle, and the higher the resolution of the transmitted optical image. When the radius d is within the range of formula (1), the image formed by the objective lens 2 can be transmitted with high resolution.

[0021] FIG. 2A illustrates the image height of the objective lens 2 of this embodiment, which is composed of a single sagittal lens, while FIG. 2B illustrates the image height of a conventional objective lens 102, which is composed of two sagittal lenses 2A and 2B. Considering an object-side telecentric ray as the chief ray, the maximum image height hmax of the conventional objective lens 102 is r1 / n1, which is smaller than the radius r1 of the proximal sagittal lens 2B. n1 is the refractive index of the sagittal lens 2B. Therefore, when an image transmitter 3 with a radius d greater than r1 / n1 is used, the peripheral region of the distal end surface 3a, where light from the objective lens 102 does not enter, does not contribute to image transmission, resulting in reduced image resolution. On the other hand, in the objective lens 2 of this embodiment, the image height is greater than r / n, and the maximum image height hmax can be increased to a dimension equal to the radius r. Therefore, when an image transmitter 3 with a radius d greater than r / n is used, high-resolution images can be transmitted without wasting the peripheral region of the distal end surface 3a.

[0022] As shown in FIGS. 1A and 1B , the image transmission unit 1 may further include a light-blocking member 5 between the tip surface 4 a of the holding member 4 and the flat surface 2 a. The light-blocking member 5 is formed from a black adhesive that is filled and hardened in the annular space between the inner surface of the tip of the holding member 4 and the convex spherical surface 2 b. The adhesive is, for example, a resin adhesive such as an epoxy resin or an ultraviolet-curing resin. The annular light-blocking member 5 that surrounds the entire periphery of the flat surface 2 a forms an aperture 6 on the tip surface 1 a of the image transmission unit 1. The aperture 6 limits the light incident on the image transmitter 3 from the object, and can eliminate light rays that could become stray light through total reflection at the convex spherical surface 2 b.

[0023] It is preferable that the objective lens 2 satisfy the following formula (2): R is the radius of the flat surface 2a. R≦r / n (2) As shown in Fig. 3, in the absence of the diaphragm 6, the on-axis marginal ray that passes from infinity through the flat surface 2a and enters the objective lens 2 is determined by the total reflection condition of the convex spherical surface 2b. Therefore, in order for the flat surface 2a to function as the diaphragm 6, it is necessary to satisfy n × sin θ≦sin 90°, that is, to satisfy R≦r / n.

[0024] 4A and 4B , the image transmission unit 1 may further include a spacer 7 disposed between the objective lens 2 and the image transmission body 3. The spacer 7 is an optical member that transmits light and preferably has a diameter equal to or approximately equal to that of the objective lens 2. The convex spherical surface 2 b and the distal end surface 3 a are in contact with the distal end surface and the proximal end surface of the spacer 7, respectively. Therefore, the thickness of the spacer 7 is designed based on the distance WD and the refractive index of the spacer 7.

[0025] One example of the spacer 7 is a parallel plate having flat surfaces perpendicular to the optical axis A on the objective lens 2 side (distal end) and the image transmitter 3 side (proximal end) (see FIG. 4A). Another example of the spacer 7 is a lens having a curved surface on at least one of the objective lens 2 side and the image transmitter 3 side, such as a plano-convex lens having a convex surface on the objective lens 2 side (see FIG. 4B). The lens 7 has positive refractive power for light incident on and passing through the lens 7 from the objective lens 2, and focuses the light from the objective lens 2 on the distal end surface 3a. This improves the angle of view.

[0026] Next, the operation of the image transmission unit 1 will be described. The image transmission unit 1 is used as an objective optical system in various devices, for example, as an imaging optical system that images an object or an illumination optical system that illuminates an object. When the image transmission unit 1 is used as an imaging optical system, light from the object enters the objective lens 2 through the flat surface 2a and exits from the convex spherical surface 2b, forming an image on the focal plane P. The image is transmitted by the image transmitter 3, whose tip surface 3a is located on or near the focal plane P. The transmitted image is captured by the image sensor 13 (see FIG. 7A ) located on the base end side of the image transmitter 3.

[0027] In this case, according to the image transmission unit 1 of this embodiment, the objective lens 2 is composed of only one sagittal lens, and the distal end surface 3a of the image transmitter 3 is located at or near the focal plane P of the objective lens 2. Therefore, light emitted from the convex spherical surface 2b is incident on the distal end surface 3a without image height reduction. Furthermore, the image transmitter 3 has a radius d greater than r / n, and light is also incident on the outermost periphery of the distal end surface 3a. This effectively utilizes the inner diameter φ of the holding member 4, which is determined by the diameter of the objective lens 2, to transmit a high-resolution image. In particular, when the outer diameter of the image transmitter 3 is equal to or approximately equal to the inner diameter of the holding member 4, all or approximately all of the inner diameter φ of the holding member 4 can contribute to resolution, effectively improving resolution.

[0028] FIG. 12 shows a conventional image transmission unit 101. The image transmission unit 101 includes two spheroidal lenses 2A and 2B, a first holding member 4A that holds the two spheroidal lenses 2A and 2B, an image transmission body 103, and a second holding member 4B that holds the first holding member 4A and the image transmission body 103. The second holding member 4B is positioned outside the first holding member 4A. In the image transmission unit 101, the presence of the spheroidal lens 2B at the base end reduces the image height h relative to the diameter of the spheroidal lens 2A. Therefore, when an image transmission body 103 with a radius d equal to the image height h is used, a region Δ is created radially outside the image transmission body 103 where the image is not projected and does not contribute to resolution. On the other hand, when an image transmission body 103 with a radius d equal to the inner diameter φ is used, as described above, the peripheral region of the image transmission body 103 does not contribute to image transmission. Therefore, in either case, the inner diameter φ of the holding member 4B cannot be effectively utilized to improve the resolution.

[0029] When the image transmission unit 1 is used as an illumination optical system, illumination light is supplied from the light source device to the image transmitter 3 through the base end surface 3b. The illumination light transmitted by the image transmitter 3 exits from the distal end surface 3a, passes through the convex spherical surface 2b, enters the objective lens 2, and is irradiated toward the object from the flat surface 2a. In this case, too, it is advantageous to use an image transmitter 3 having a radius d greater than r / n. That is, the larger the radius d, the greater the amount of illumination light that can be transmitted by the image transmitter 3. Furthermore, the illumination light emitted from the distal end surface 3a is irradiated toward the object through the objective lens 2 with high efficiency. Therefore, the inner diameter φ of the holding member 4, which is determined by the diameter of the objective lens 2, can be effectively utilized to achieve bright illumination.

[0030] Furthermore, according to the image transmission unit 1 of this embodiment, both the objective lens 2 and the image transmission body 3 are held within a single holding member 4. This makes it possible to reduce the diameter of the image transmission unit 1. If the image transmission unit 1 were to include two holding members 4A and 4B, as in the conventional image transmission unit 101, the outer diameter of the image transmission unit 1 would increase by the thickness of the side wall of the second holding member 4B, and a region Δ that does not contribute to resolution would be created between the outer peripheral surface of the image transmission body 3 and the inner peripheral surface of the second holding member 4B.

[0031] Furthermore, since the objective lens 2 is larger than a hemisphere, an aperture 6 made of a light-shielding member 5 can be formed between the tip surface 4a on the tip surface 1a of the image transmission unit 1 and the plane 2a, and the objective lens 2 can be firmly fixed to the holding member 4 by frictional force.

[0032] An embodiment of the image transmission unit 1 will be described below.

[0033] Next, we will explain a manufacturing method of the image transmission unit 1. As shown in Figures 5A to 5F, the manufacturing method of the image transmission unit 1 includes step S1 of inserting a single ball lens 2' into the holding member 4, step S2 of applying adhesive 5' to the tip surface of the ball lens 2', step S3 of forming a flat surface 2a on the ball lens 2' to prepare the objective lens 2, step S4 of inserting the image transmitter 3 into the holding member 4, and step S5 of positioning the objective lens 2 and the image transmitter 3 relative to each other.

[0034] In step S1, the ball lens 2' is press-fitted into the tip of the holding member 4 to form an assembly consisting of the ball lens 2' and the holding member 4 (see FIG. 5A). The ball lens 2' is fixed to the holding member 4 by friction between the outer surface of the ball lens 2' and the inner surface of the holding member 4. Next, in step S2, a black adhesive 5' is placed on the tip surface of the assembly, and the adhesive 5' fills the gap between the tip surface of the ball lens 2' and the inner surface of the tip of the holding member 4 (see FIG. 5B). The adhesive 5' is then cured. When manufacturing an image transmission unit 1 that does not include a light-blocking member 5, step S2 may be omitted.

[0035] Next, in step S3, a tool is used to polish the tip of the assembly (see FIG. 5C). The polishing direction is perpendicular to the longitudinal axis of the holding member 4. The tip of the holding member 4 and a portion of the spherical lens 2' are removed by polishing, forming a flat surface 2a. If a black adhesive 5' is filled in step S2, the adhesive 5' is polished along with the spherical lens 2' and holding member 4, and an aperture 6 made of the light-blocking member 5 is also formed at the same time as the flat surface 2a. In step S3, multiple assemblies arranged parallel to each other may be polished simultaneously.

[0036] Next, in step S4, the image transmitter 3 is inserted into the base end of the holding member 4 (see FIG. 5D). If necessary, an adhesive may be applied to at least one of the outer circumferential surface of the image transmitter 3 and the inner circumferential surface of the holding member 4 to secure the image transmitter 3 to the holding member 4.

[0037] Next, in step S5, the distance WD is adjusted to position the tip surface 3a of the image transmitter 3 at or near the focal plane P. An optical index is used to adjust the distance WD. In one example, as shown in FIG. 5E, an object O is placed in front of the objective lens 2, and an image of the object O is formed behind the image transmitter 3. The image transmitter 3 is positioned at a position where the image is in focus. In another example, as shown in FIG. 5F, illumination light is supplied to the image transmitter 3, and the illumination light is projected onto a screen S in front of the objective lens 2. The image transmitter 3 is positioned at a position where the image of the illumination light on the screen S is sharpest.

[0038] When manufacturing an image transmission unit 1 including the spacer 7, the spacer 7 is inserted into the holding member 4 between steps S3 and S4. The image transmission element 3 is inserted into the holding member 4 until the convex spherical surface 2b and the tip surface 3a abut against both sides of the spacer 7, thereby positioning the tip surface 3a at an appropriate position. Therefore, the adjustment of the distance WD as shown in Figures 5E and 5F is not necessary.

[0039] Thus, according to the manufacturing method of this embodiment, simply by press-fitting the ball lens 2' into the holding member 4, the center of curvature of the convex spherical surface 2b is positioned on the central axis of the holding member 4. In other words, high positional accuracy of the objective lens 2 with respect to the holding member 4 can be achieved, without the need to adjust the position of the ball lens 2' with respect to the holding member 4.

[0040] Furthermore, according to the manufacturing method of this embodiment, the ball lens 2' is fixed to the holding member 4 simply by press-fitting the ball lens 2' into the holding member 4, and further, as described above, there is no need to adjust the position of the ball lens 2' relative to the holding member 4. Furthermore, because both the ball lens 2' and the image transmitter 3 are inserted into one holding member 4, the number of parts to be assembled and the number of assembly steps are reduced. Therefore, the image transmission unit 1 can be easily assembled.

[0041] In this embodiment, the image transmitter 3 is a fiber bundle or a relay optical system, but it may instead be an image sensor. In this case, the imaging surface (tip surface) of the image sensor is located at or near the focal plane P of the objective lens 2. The optical image of the object formed on the imaging surface is converted into an electronic signal by the image sensor and transmitted in the form of the electronic signal via a signal cable. The radius d of the image sensor is, for example, the radius of the circumscribed circle of the rectangular imaging surface.

[0042] In this embodiment, the light-shielding member 5 is made of a black adhesive, but it may be made of another material instead. For example, in step S2, a transparent adhesive may be used instead of the black adhesive 5', and after step S3, the light-shielding member 5 made of a light-shielding film may be formed on the tip surface 1a.

[0043] Second Embodiment Next, an image transmission unit according to a second embodiment of the present invention will be described with reference to the drawings. As shown in Fig. 6, an image transmission unit 10 according to this embodiment uses a relay optical system including a GRIN (gradient index) lens 8 as an image transmitter. In this embodiment, only configurations different from the first embodiment will be described, and configurations common to the first embodiment will be denoted by the same reference numerals and will not be described again.

[0044] The image transmission unit 10 includes a single objective lens 2 , a GRIN lens (image transmission body, relay optical system) 8 , and a single holding member 4 that holds both the objective lens 2 and the GRIN lens 8 .

[0045] The GRIN lens 8 is disposed along the optical axis A on the convex spherical surface 2b side (proximal end side) of the objective lens 2. The GRIN lens 8 has a tip surface 8a facing the convex spherical surface 2b. The tip surface 8a may be in contact with the convex spherical surface 2b or may be spaced apart from the convex spherical surface 2b.

[0046] The tip surface 8a may be a flat surface. The tip surface 8a may also be a spherical surface convex toward the convex spherical surface 2b. In this case, the tip surface 8a is disposed between the focal plane P and the convex spherical surface 2b, and the focal plane P is located inside the GRIN lens 8. In this way, the tip surface 8a is a convex surface that functions as a lens, which can widen the angle of view of the image transmission unit 10. The convex surface 8a is formed, for example, on the flat tip surface of the GRIN lens using an optical adhesive.

[0047] Light emitted from the convex spherical surface 2b toward the GRIN lens 8 includes expanded light that expands in the radial direction. The expanded light reaches the outermost periphery within the GRIN lens 8, and light that passes through the flat surface 2a includes light that passes through the outermost periphery of the GRIN lens 8. The objective lens 2 and the GRIN lens 8 satisfy the following formula (1): r / n<d≦r (1) In this embodiment, d is the effective radius of the GRIN lens 8. Preferably, the outer diameter of the GRIN lens is equal to or approximately equal to the outer diameter of the objective lens 2. In this way, by having the radius d within the range of formula (1), the image formed by the objective lens 2 can be transmitted with high resolution.

[0048] The image transmission unit 10 may further include a light-blocking member 5. The image transmission unit 10 may not include the light-blocking member 5 (i.e., the diaphragm 6). Light that can propagate through the GRIN lens 8 is limited by vignetting at the side surfaces of the GRIN lens 8. Therefore, even if the diaphragm 6 is not present, the brightness of the image transmission unit 10 can be determined by the GRIN lens 8. In this regard, as shown in FIG. 6 , the radius R of the plane 2 a may be greater than r / n and may satisfy equation (2) as in the first embodiment.

[0049] Like the image transmission unit 1 of the first embodiment, the image transmission unit 10 of this embodiment is used as an objective optical system, for example, an imaging optical system or an illumination optical system. According to the image transmission unit 10, the objective lens 2 is composed of only one sagittal lens, and light emitted from the convex spherical surface 2b is incident on the distal end surface 8a without image height reduction. Furthermore, the GRIN lens 8 has a radius d larger than r / n, and light is also incident on the outermost periphery of the GRIN lens 8. This allows for effective use of the inner diameter φ of the holding member 4, which is determined by the diameter of the objective lens 2, when used as an imaging optical system, thereby transmitting a high-resolution image. Furthermore, since the GRIN lens 8 has a radius d larger than r / n, bright illumination can be achieved when used as an illumination optical system.

[0050] Furthermore, both the objective lens 2 and the GRIN lens 8 are held within a single holding member 4. This allows for a smaller diameter of the image transmission unit 10. Furthermore, because the objective lens 2 is larger than a hemisphere, the objective lens 2 can be firmly fixed to the holding member 4 by frictional force.

[0051] An embodiment of the image transmission unit 10 will be described below.

[0052] Next, a method for manufacturing the image transmission unit 10 according to this embodiment will be described. The method for manufacturing the image transmission unit 10 includes steps S1 and S2, step S31 for inserting the GRIN lens 8 into the holding member 4, and step S41 for positioning the objective lens 2 and the GRIN lens 8 relative to each other. In step S41, the GRIN lens 8 is positioned so that its tip surface 8a is located closer to the convex spherical surface 2b than the focal plane P. For example, the GRIN lens 8 is positioned so that its tip surface 8a abuts against the convex spherical surface 2b or is located near the convex spherical surface 2b. Therefore, unlike step S4 in the first embodiment, fine adjustment of the position of the GRIN lens 8 is not necessarily required.

[0053] According to the manufacturing method of this embodiment, similar to the manufacturing method of the first embodiment, it is possible to achieve high positional accuracy of the objective lens 2 with respect to the holding member 4, while eliminating the need for position adjustment of the ball lens 2' with respect to the holding member 4. Furthermore, similar to the manufacturing method of the first embodiment, it is possible to easily assemble the image transmission unit 10.

[0054] Third Embodiment Next, an optical device according to a third embodiment of the present invention will be described. In this embodiment, configurations different from those of the first and second embodiments will be described, and configurations common to the first and second embodiments will be described with the same explanations and will not be described again. As shown in Figures 7A and 7B, an optical device 20 according to this embodiment is an endoscope, and includes an image transmission unit 11, an illumination optical system 12, an image sensor (optical element) 13, and a cylindrical member 14. Figure 7A shows a rigid endoscope, and Figure 7B shows a flexible endoscope.

[0055] The image transmission unit 11 is used as an imaging optical system of the endoscope 20. The image transmission unit 11 is the image transmission unit 1 of the first embodiment or the image transmission unit 10 of the second embodiment. The image transmission unit 11 in the referenced drawings is an image transmission unit 1 including an image transmission body 3 such as a fiber bundle or a relay optical system, but may instead be an image transmission unit 10 including a GRIN lens 8. The objective lens 2 is disposed at the tip of the long insertion section 21 of the endoscope 20 and forms an image of an object. The image transmission body 3 extends along the longitudinal direction of the insertion section 21 and transmits the image of the object to the imaging element 13.

[0056] The illumination optical system 12 has one or more, preferably multiple, optical fibers 12a. As shown in FIG. 8 , the multiple optical fibers 12a are arranged between the holding member 4 and the cylindrical member 14 along the longitudinal direction of the members 4, 14, and are arranged circumferentially around the image transmission unit 11. The cylindrical member 14 is a long, tubular member that houses the image transmission unit 11 and the illumination optical system 12 therein. The tip of each optical fiber 12a is arranged on the tip surface of the insertion section 21 (the tip surface of the cylindrical member 14), and the base end of each optical fiber 12a is optically connected to a light source device. Each optical fiber 12a guides illumination light supplied from the light source device to its base end and irradiates the illumination light from its tip toward an object.

[0057] The imaging element 13 is disposed on the base end side of the image transmitter 3, captures an image transmitted by the image transmitter 3, generates an image signal, and outputs the image signal. An imaging lens 15 may be disposed between the base end surface 3b of the image transmitter 3 and the imaging element 13. The imaging lens 15 forms an image of the object transmitted by the image transmitter 3 on the imaging surface 13a of the imaging element 13.

[0058] 9 shows an example of an endoscopic system 100 including an endoscope 20. The endoscopic system 100 includes the endoscope 20, a housing 30, and a display 40. The endoscope 20 has a long insertion section 21 and an imaging section 22 connected to the proximal end of the insertion section 21. The image transmission unit 11 and the illumination optical system 12 are disposed within the insertion section 21, and the imaging element 13 and imaging lens 15 are disposed within the imaging section 22.

[0059] The imaging unit 22 is detachably connected to the base end of the insertion unit 21 by the connection unit 23, thereby making the insertion unit 21 replaceable. The imaging unit 22 may be integrated with the housing unit 30. That is, the housing unit 30 may be connected to the base end of the insertion unit 21, and the imaging element 13 and the imaging lens 15 may be disposed within the housing unit 30.

[0060] The housing 30 includes an illumination section (light source device) 31 and an image processing section 32. The illumination section 31 has a light source 31a, and the proximal ends of the plurality of optical fibers 12a drawn out from the proximal end of the insertion section 21 are optically connected to the light source 31a. The illumination section 31 may further include a focusing lens 31b arranged between the light source 31a and the proximal ends of the plurality of optical fibers 12a. The focusing lens 31b focuses the light emitted from the light source 31a onto the proximal ends of the optical fibers 12a.

[0061] The image processing unit 32 includes, for example, a processor and a memory. The image processing unit 32 generates an image of the object from the image signal output from the imaging element 13 and outputs the image to the display unit 40. The display unit 40 is any display device such as a liquid crystal display, and displays the image input from the image processing unit 32.

[0062] As described above, according to this embodiment, the endoscope 20 can be configured by combining the image transmission unit 11 with the illumination optical system 12. Furthermore, by appropriately selecting the image transmitter 3 or 8, either a rigid or flexible endoscope 20 can be manufactured. Furthermore, by using the image transmission unit 11 as the imaging optical system, an endoscope 20 with a slim insertion section 21 and high image resolution can be easily realized. Therefore, the endoscope 20 and the endoscope system 100 are suitable for use in a long, narrow lumen such as the ureter.

[0063] In this embodiment, the image transmitter 3 may be an image sensor 13. In this case, the image sensor 13 is disposed at the tip of the insertion portion 21 together with the objective lens 2. An image signal output from the image sensor 13 is transmitted to the image processing unit 32 via a signal cable passing through the insertion portion 21.

[0064] Next, a method for manufacturing the optical device 20 will be described. FIGS. 10A to 10D show a portion of the method for manufacturing the optical device 20. The method for manufacturing the optical device 20 includes step S1 of inserting a single ball lens 2′ into the holding member 4, step S6 of inserting the assembly and the optical fiber 12a into the cylindrical member 14, step S21 of applying adhesive 5′ to the tip surface of the ball lens 2′, step S31 of forming a flat surface 2a on the ball lens 2′ to prepare the objective lens 2, step S4 of inserting the image transmitter 3 into the holding member 4, and step S5 of positioning the objective lens 2 and the image transmitter 3 relative to each other. Steps S1, S4, and S5 are the same as those described in the first embodiment. After step S1, in step S6, a first assembly consisting of the ball lens 2′ and the holding member 4 is inserted into the cylindrical member 14, and then one or more optical fibers 12a are inserted into the cylindrical space between the holding member 4 and the cylindrical member 14 (see FIG. 10A ). As a result, a second assembly is formed, which is made up of the ball lens 2', the holding member 4, the cylindrical member 14, and one or more optical fibers 12a.

[0065] Next, in step S21, a black adhesive 5' is placed on the tip surface of the second assembly, and the adhesive 5' is filled into the space between the tip surface of the ball lens 2' and the inner surface of the tip of the holding member 4, and into the space between the optical fiber 12a and the members 4 and 14 (see FIG. 10B). Then, the adhesive 5' is hardened.

[0066] Next, in step S31, a tool is used to polish the tip of the second assembly (see FIG. 10C). The polishing direction is perpendicular to the longitudinal axis of the holding member 4. The ends of the members 4 and 14, a portion of the ball lens 2', and the tip of the optical fiber 12a are removed by polishing, and the plane 2a and the diaphragm 6 are simultaneously formed. Next, steps S4 and S5 are performed as in the first embodiment (see FIG. 10D). If necessary, a spacer 7 may be inserted into the holding member 4 between steps S31 and S4.

[0067] Thus, according to the manufacturing method of this embodiment, in step S21, the holding member 4, the tubular member 14, and the optical fiber 12a are fixed at the same time by applying and curing the adhesive 5' to form the light-blocking member 5. Furthermore, in step S31, the ball lens 2', the holding member 4, the tubular member 14, and the optical fiber 12a are all polished at the same time. This reduces the number of steps, making it possible to easily manufacture the optical device 20.

[0068] (Fourth Embodiment) Next, an optical device according to a fourth embodiment of the present invention will be described. In this embodiment, configurations different from those of the first to third embodiments will be described, and configurations common to the first to third embodiments will be described with the same explanations provided and will not be described again. As shown in Fig. 11 , an optical device 50 according to this embodiment is an optical scanning type illumination device, and includes an image transmission unit 11 and a light source device (optical element) 16.

[0069] The image transmission unit 11 is the image transmission unit 1 of the first embodiment or the image transmission unit 10 of the second embodiment, and is used as an illumination optical system. The image transmission unit 11 in the referenced drawings is the image transmission unit 1 including an image transmission body 3 such as a fiber bundle or a relay optical system, but may instead be the image transmission unit 10 including a GRIN lens 8.

[0070] The light source device 16 is an optical scanner disposed on the proximal end side of the image transmitter 3, and includes a light source 16a and a scanning mechanism 16b that scans light (e.g., laser light) output from the light source 16a. The scanning mechanism 16b is, for example, a scanning mirror such as a galvanometer mirror. The scanning mechanism 16b scans the light incident on the proximal end surface 3b in a direction along the proximal end surface 3b (see the double arrow), and preferably can scan the light over the entire surface of the proximal end surface 3b.

[0071] The optical scanner 16 may further include a first lens 16c disposed between the light source 16a and the scanning mechanism 16b, and a second lens 16d disposed between the scanning mechanism 16b and the base end surface 3b. The lenses 16c and 16d are biconvex lenses that form a collimating optical system. The first lens 16c converts the light output from the light source 16a into a parallel beam, and the second lens 16d converts the parallel light scanned by the scanning mechanism 16b into a convergent beam.

[0072] The light scanned by the scanning mechanism 16b passes through the base end surface 3b and enters the image transmitter 3, is transmitted by the image transmitter 3, exits from the tip end surface 3a, passes through the convex spherical surface 2b and enters the objective lens 2, and is irradiated toward the object from the flat surface 2a.

[0073] The scanning mechanism 16b may be an optical fiber scanner that scans light by vibrating the tip of an optical fiber. The optical fiber scanner includes an optical fiber and a piezoelectric or electromagnetic scanner that vibrates the tip of the optical fiber. The base end of the optical fiber is optically connected to the light source 16a, and light is incident from the vibrating tip of the optical fiber to the base end surface 3b while being scanned. In this case, the first lens 16c is a focusing lens that focuses the light output from the light source 16a on the base end surface of the optical fiber, and the second lens 16d is a magnifying lens that expands the scanning range of the light so that the light scans the entire surface of the base end surface 3b.

[0074] As described above, according to this embodiment, it is possible to manufacture an illumination device 50 that irradiates or projects light onto an object by combining the image transmission unit 11 with the light source device 16. The illumination device 50 can efficiently transmit light from the light source device to the object despite its small diameter, and is therefore particularly useful in situations such as robotic medical treatment where the illumination device 50 is inserted into the treatment tool channel of an endoscope and projects light onto tissue inside a living body.

[0075] In the present embodiment, the illumination device 50 is a scanning illumination device, but it may be a non-scanning illumination device. That is, the light source device 16 does not need to include the optical scanner 16. In this case, the light output from the light source 16a is simultaneously incident on the entire or substantially the entire base end surface 3b, and is simultaneously irradiated onto the entire illumination range of the object.

[0076] The above describes in detail the embodiments of the present invention and their modifications, but the present invention is not limited to the above embodiments and their modifications, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

[0077] REFERENCE SIGNS LIST 1, 10, 11 Image transmission unit 2 Objective lens 3 Image transmission body 3a Tip surface 4 Holding member 4a Tip surface 5 Light-blocking member 7 Spacer 8 GRIN lens (image transmission body, relay optical system) 12 Illumination optical system 13 Image pickup element (optical element) 13a Image pickup surface 14 Cylinder member 15 Imaging lens 16 Optical scanner (optical element, light source device) 20 Endoscope (optical device) 50 Illumination device (optical device) 100 Endoscope system

Claims

1. a single objective lens consisting of a single aspheric lens having a flat surface and a convex spherical surface; an image transmitting body disposed on the side of the convex spherical surface of the objective lens; a single holding member that holds both the objective lens and the image transmitting element; The objective lens and the image transmitting body satisfy the following formula (1): An image transmission unit, wherein the light passing through the plane includes light passing through the outermost periphery of the image transmission element. r / n<d≦r...(1) where: r is the radius of the objective lens, n is the refractive index of the objective lens, d is the radius of the image transmitter is.

2. the holding member is a cylindrical member that houses the objective lens and the image transmitting body, the objective lens and the image transmitting body being disposed on a distal end side and a proximal end side of the holding member, respectively; 2. The image transmission unit according to claim 1, further comprising a light-shielding member between the tip end surface of said holding member and said flat surface, said light-shielding member surrounding said flat surface.

3. 2. The image transmission unit according to claim 1, wherein the objective lens satisfies the following formula (2): R≦r / n...(2) where: R is the radius of the plane is.

4. The image transmission unit of claim 1 , further comprising a spacer disposed between the objective lens and the image transmission body.

5. 5. The image transmission unit according to claim 4, wherein said spacer has a positive refractive power for light incident on said spacer from said objective lens and passing through said spacer.

6. the image transmitting body is a fiber bundle, a relay optical system, or an image pickup element, and has a tip surface disposed at a distance from the convex spherical surface; The image transmission unit of claim 1 , wherein the distal end surface is located at or near the focal plane of the objective lens.

7. 2. The image transmission unit of claim 1, wherein the image transmission element is a GRIN lens.

8. 8. The image transmission unit according to claim 7, wherein the tip surface of said GRIN lens is a spherical surface convex toward said convex spherical surface.

9. An image transmission unit as described in claim 1, wherein the aspherical lens is a lens formed by cutting out a part of a spherical lens to form a flat surface.

10. an image transmission unit including a single objective lens consisting of a single aspheric lens having a flat surface and a convex spherical surface, an image transmission body disposed on the side of the convex spherical surface of the objective lens, and a single holding member for holding both the objective lens and the image transmission body; an optical element disposed on the opposite side of the image transmitting body from the objective lens, The objective lens and the image transmitting body satisfy the following formula (1): The optical apparatus wherein the light passing through the plane includes light passing through the outermost periphery of the image transmitting element. r / n<d≦r...(1) where: r is the radius of the objective lens, n is the refractive index of the objective lens, d is the radius of the image transmitter is.

11. 11. The optical instrument according to claim 10, wherein the optical element is an image pickup element that captures the image of the object formed by the objective lens and transmitted by the image transmission body.

12. Further comprising an illumination optical system, 11. The optical instrument of claim 10, wherein the illumination optics comprises one or more optical fibers arranged circumferentially around the image transmission unit.

13. 11. The optical apparatus according to claim 10, wherein the optical element is a light source device that supplies light to the image transmitting body.

14. The optical instrument according to claim 13 , wherein the light source device is an optical scanner that scans the light.

15. An optical device as described in claim 10, wherein the aspherical lens is a lens formed by cutting out a part of a spherical lens to form a flat surface.

16. Inserting a single spherical lens into a cylindrical holding member; inserting an image transmitter into said holding member; Polishing the end of the holding member and the ball lens to form a flat surface on the ball lens; and and positioning the ball lens on which the flat surface is formed and the image transmitting body relative to one another at a position where light passing through the flat surface includes light passing through the outermost periphery of the image transmitting body.

17. 17. The method for manufacturing an image transmission unit according to claim 16, further comprising filling a space between the inner surface of the holding member and the outer surface of the ball lens with a light-blocking material before forming the flat surface.