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

Abstract

An image transmission unit (1) is provided with: a single objective lens (2) comprising a single lens formed as a spherical segment having a flat surface (2a) and a convex spherical surface (2b); an image transmission body (3) disposed on the convex spherical surface (2b) side of the objective lens (2); and a single holding member (4) for holding both the objective lens (2) and the image transmission body (3). The objective lens (2) and the image transmission body (3) satisfy formula (1), and the light passing through the plane (2a) includes the light passing through the outermost periphery 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). R / n < d < = r... (1)

Description

Technical Field

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

[0002] Conventionally, an optical unit including a plurality of spherical segment lenses and a cylindrical holding member for holding the plurality of spherical segment lenses has been known (for example, refer to Patent Document 1). A spherical segment lens is a lens having a three-dimensional shape formed by cutting a sphere with a plane. By using a spherical segment lens, it is easy to reduce the diameter of the optical unit, and it is possible to easily manufacture an optical unit suitable as an objective optical system for a thin-diameter endoscope.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: International Publication No. 2021 / 255929 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] An image of an object formed by an optical unit is transmitted through an image transmission body such as a fiber bundle or a relay optical system. In order to improve the resolution of the image transmitted through the image transmission body, it is preferable that the image height is large, and correspondingly, the effective radius of the image transmission body is large. However, in the case of the optical unit of Patent Document 1, since there is a second spherical segment lens, the image height is small relative to the diameter of the spherical segment lens, and it is difficult to increase the image height.

[0008] Moreover, in Patent Document 1, the optical unit and the image transmission body are inserted into a cylindrical member. That is, since the holding member and the cylindrical member are arranged in a double layer, the overall outer diameter becomes large.

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide an image transmission unit, an optical device, and a method for manufacturing an image transmission unit that can achieve a small diameter and high resolution.

[0010] Solutions to the Problems

[0011] One aspect of the present invention is an image transmission unit including: a single objective lens composed of a single lens formed in a spherical segment shape having a plane and a convex spherical surface; an image transmission body disposed on the convex spherical surface side of the objective lens; and a single holding member for holding both the objective lens and the image transmission body, wherein the objective lens and the image transmission body satisfy the following formula (1), and the light passing through the plane includes the light passing through the outermost periphery of the image transmission body.

[0012] r / n < d ≤ r...(1)

[0013] Here, 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 transmission body.

[0014] Another aspect of the present invention is an optical device including an image transmission unit and an optical element. The image transmission unit includes: a single objective lens formed of a single lens in the shape of a spherical segment having a flat surface and a convex spherical surface; an image transmission body disposed on the convex spherical surface side of the objective lens; and a single holding member for holding both the objective lens and the image transmission body. The optical element is disposed on the side of the image transmission body opposite to the objective lens. The objective lens and the image transmission body satisfy the following formula (1), and the light passing through the flat surface includes the light passing through the outermost periphery of the image transmission body.

[0015] r / n < d ≤ r…(1)

[0016] Here, 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 transmission body.

[0017] Another aspect of the present invention is a method for manufacturing an image transmission unit, including: 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 grinding the end of the holding member and the spherical lens; and positioning the spherical lens having the flat surface and the image transmission body at a position where the light passing through the flat surface includes the light passing through the outermost periphery of the image transmission body.

[0018] Effects of the Invention

[0019] According to the present invention, an effect of achieving a small diameter and high resolution can be obtained. Description of the Drawings

[0020] Figure 1A is a longitudinal sectional view showing the structure of the image transmission unit according to the first embodiment of the present invention.

[0021] Figure 1B is a front view showing Figure 1A the front end face of the image transmission unit.

[0022] Figure 2A is a diagram for explaining Figure 1A the image height of the objective lens in the image transmission unit.

[0023] Figure 2B is a diagram for explaining the image height of an existing objective lens having two spherical segment lenses.

[0024] Figure 3 is a diagram for explaining formula (2).

[0025] Figure 4AIt is a longitudinal sectional view of an example of an image transmission unit having a spacer.

[0026] Figure 4B It is a longitudinal sectional view of another example of an image transmission unit having a spacer.

[0027] Figure 5A It is a diagram showing step S1 of the manufacturing method of the image transmission unit.

[0028] Figure 5B It is a diagram showing step S2 of the manufacturing method of the image transmission unit.

[0029] Figure 5C It is a diagram showing step S3 of the manufacturing method of the image transmission unit.

[0030] Figure 5D It is a diagram showing step S4 of the manufacturing method of the image transmission unit.

[0031] Figure 5E It is a diagram showing step S5 of the manufacturing method of the image transmission unit.

[0032] Figure 5F It is a diagram showing step S5 of the manufacturing method of the image transmission unit.

[0033] Figure 6 It is a longitudinal sectional view showing the structure of the image transmission unit according to the second embodiment of the present invention.

[0034] Figure 7A It is a structural diagram of an example of an optical device according to the third embodiment of the present invention.

[0035] Figure 7B It is a structural diagram of another example of an optical device according to the third embodiment of the present invention.

[0036] Figure 8 It shows Figure 7A and Figure 7B The front view of the front end face of the optical device.

[0037] Figure 9 It has Figure 7A and Figure 7B The structural diagram of an example of the system of the optical device.

[0038] Figure 10A It is a diagram showing step S6 of the manufacturing method of the optical device.

[0039] Figure 10B It is a diagram showing step S21 of the manufacturing method of the optical device.

[0040] Figure 10C It is a diagram showing step S31 of the manufacturing method of the optical device.

[0041] Figure 10D It is a diagram for explaining steps S4 and S5 of the method for manufacturing an optical device.

[0042] Figure 11 It is a structural diagram of an optical device according to a fourth embodiment of the present invention.

[0043] Figure 12 It is a longitudinal sectional view showing the structure of a conventional image transmission unit. DETAILED DESCRIPTION

[0044] (First Embodiment)

[0045] An image transmission unit according to a first embodiment of the present invention will be described with reference to the drawings.

[0046] like Figure 1A and Figure 1B As shown, the image transmission unit 1 according to the present embodiment includes a single objective lens 2 , an image transmission body 3 , and a single cylindrical holding member 4 for holding both the objective lens 2 and the image transmission body 3 .

[0047] The image transmission unit 1 is in the shape of a long strip, and the objective lens 2 and the image transmission body 3 are respectively arranged on the front end side and the base end side of the image transmission unit 1 .

[0048] The objective lens 2 is composed of a single lens formed into a spherical segment having a plane 2a and a convex spherical surface 2b, and does not include other lenses. The spherical segment is a three-dimensional shape formed by cutting a sphere with a single plane. Therefore, the surface of the objective lens 2 is composed of a circular plane 2a and a convex spherical surface 2b. The plane 2a is arranged on the front end side, and when the image transmission unit 1 is used, the plane 2a is arranged to face the object. Preferably, the objective lens 2 is larger than a hemisphere, and the center of curvature of the convex spherical surface 2b exists on the inner side of the objective lens 2. The objective lens 2 has an optical axis A (refer to Figure 2A ). The objective lens 2 is formed of a glass material generally used for optical lenses, such as sapphire or BK7.

[0049] The objective lens 2 may be a perfect spherical segment, or may be a shape close to a spherical segment. That is, the plane 2a may be a perfect plane, and the convex spherical surface 2b may be a perfect spherical surface. Alternatively, the plane 2a and the convex spherical surface 2b may have errors relative to the perfect plane and the perfect spherical surface, respectively, as long as they satisfy the optical performance required as the image transmission unit 1. The errors may include, for example, wear, loss or deformation that may occur during the manufacturing process of the image transmission unit 1.

[0050] The image transmission body 3 is an optical member disposed on the convex spherical surface 2b side (base end side) of the objective lens 2 and extending in the longitudinal direction of the holding member 4. An example of the image transmission body 3 is a fiber bundle having a plurality of optical fibers. Another example of the image transmission body 3 is a relay optical system composed of one or more lenses.

[0051] The holding member 4 is a cylindrical member having openings at both end faces, and preferably has a constant inner diameter throughout its entire length. The holding member 4 is preferably a circular tube having a circular cross-section throughout its entire length. The holding member 4 is formed of a hard material such as metal or synthetic resin, and is preferably formed of a metal such as stainless steel or aluminum alloy.

[0052] The holding member 4 houses the objective lens 2 and the image transmission body 3 therein, and the objective lens 2 and the image transmission body 3 are respectively disposed on the front end side and the base end side of the holding member 4. The plane 2a and the annular front end face 4a of the holding member 4 are disposed in the same plane, and the optical axis A coincides with the central axis of the holding member 4. In the case where the image transmission body 3 is composed of a single optical member (for example, in the case where the image transmission body 3 is a fiber bundle), only a part of the front end side of the image transmission body 3 may be held in the holding member 4.

[0053] As Figure 2A shown, the convex spherical surface 2b is in contact with 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 of the holding member 4 is 2×r or less of the diameter of the objective lens 2, and is preferably slightly smaller than 2×r. r is the radius of the objective lens 2 (that is, the radius of curvature of the convex spherical surface 2b). Thus, by simply pressing the objective lens 2 into the holding member 4, the objective lens 2 can be fixed to the holding member 4 by friction. In order to prevent the objective lens 2 from being damaged during pressing, it is preferable to satisfy

[0054] The holding member 4 only needs to be able to hold the objective lens 2 by friction, and may have a shape other than a cylinder. For example, it may be a square tube having a polygonal cross-section.

[0055] The image transmission body 3 has a front end face 3a facing the convex spherical surface 2b. The front end face 3a is disposed on the focal plane P of the objective lens 2 or near the focal plane P, and is separated from the convex spherical surface 2b by a predetermined distance WD in the direction of the optical axis A.

[0056] The light emitted from the convex spherical surface 2b toward the image transmission body 3 includes expanding light that expands in the radial direction. Since the front end face 3a is separated from the convex spherical surface 2b by a predetermined distance WD, the expanding light reaches the outermost periphery of the front end face 3a or near the outermost periphery, and the light passing through the plane 2a includes the light passing through the outermost periphery of the image transmission body 3.

[0057] The objective lens 2 and the image transmission body 3 satisfy the following formula (1).

[0058] r / n < d ≤ r …(1)

[0059] Here, 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 transmission body 3 (specifically, the effective radius of the front end face 3a). Preferably, the outer diameter of the image transmission body 3 is equal to or approximately equal to the outer diameter of the objective lens 2.

[0060] In order to improve the resolution of the image transmitted through the image transmission body 3, it is preferable that the radius d of the image transmission body 3 is large. For example, in the case where the image transmission body 3 is a fiber bundle, the larger the radius d, the more the number of optical fibers constituting the fiber bundle, and the higher the resolution of the transmitted optical image. Since the radius d is within the range of the formula (1), the image formed by the objective lens 2 can be transmitted with high resolution.

[0061] Figure 2A The image height of the objective lens 2 composed of a single spherical segment lens according to the present embodiment has been described. Figure 2B The image height of the conventional objective lens 102 composed of two spherical segment lenses 2A and 2B has been described.

[0062] If the chief ray of the object-side telecentric light is considered, the maximum image height hmax of the conventional objective lens 102 is r1 / n1, which is smaller than the radius r1 of the spherical segment lens 2B on the base end side. n1 is the refractive index of the spherical segment lens 2B. Therefore, in the case where an image transmission body 3 with a radius d larger than r1 / n1 is used, the region of the peripheral edge of the front end face 3a that is not incident with light from the objective lens 102 does not contribute to the transmission of the image, and the resolution of the image is reduced.

[0063] On the other hand, in the objective lens 2 of the present embodiment, the image height is larger than r / n, and the maximum image height hmax can be increased to a size equal to the radius r. Therefore, an image transmission body 3 with a radius d larger than r / n can be used to transmit the image with high resolution without wasting the region of the peripheral edge of the front end face 3a.

[0064] As Figure 1A and Figure 1B shown, the image transmission unit 1 may also include a light-shielding member 5 for shielding light between the front end face 4a of the holding member 4 and the plane 2a.

[0065] The light-shielding member 5 is formed of a black adhesive that has solidified in the annular space filled between the inner surface of the front end portion of the holding member 4 and the convex spherical surface 2b. The adhesive is, for example, a resin adhesive such as an epoxy resin or an ultraviolet curable resin. By the annular light-shielding member 5 that surrounds the entire circumference of the plane 2a, a diaphragm 6 is formed on the front end face 1a of the image transmission unit 1. The light incident from the object to the image transmission body 3 is restricted by the diaphragm 6, thereby enabling the exclusion of light rays that may become stray light due to total reflection at the convex spherical surface 2b.

[0066] The objective lens 2 preferably satisfies the following formula (2). R is the radius of the plane 2a.

[0067] R ≤ r / n…(2)

[0068] As Figure 3 shown, in the absence of the diaphragm 6, the marginal ray on the axis incident on the objective lens 2 from infinity through the plane 2a is defined by the total reflection condition of the convex spherical surface 2b. Therefore, in order for the plane 2a to function as the diaphragm 6, it is necessary to satisfy n × sinθ ≤ sin90°, that is, to satisfy R ≤ r / n.

[0069] As Figure 4A and Figure 4B shown, the image transmission unit 1 may also 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 the diameter of the objective lens 2. The convex spherical surface 2b and the front end face 3a are in contact with the front end face and the base end face 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.

[0070] An example of the spacer 7 is a parallel flat plate having planes orthogonal to the optical axis A on the objective lens 2 side (front end side) and the image transmission body 3 side (base end side) (refer to Figure 4A ).

[0071] 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 transmission body 3 side. For example, it is a plano-convex lens having a convex surface on the objective lens 2 side (refer to Figure 4B ). The lens 7 has a positive refractive power for the light incident on the lens 7 from the objective lens 2 and passing through the lens 7, and focuses the light from the objective lens 2 onto the front end face 3a. Thereby, the viewing angle can be increased.

[0072] Next, the operation of the image transmission unit 1 will be described.

[0073] The image transmission unit 1 is used as an objective optical system for various devices, for example, as an imaging optical system for photographing an object or an illumination optical system for illuminating an object.

[0074] When the image transmission unit 1 is used as an imaging optical system, light from an object is incident on 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 transmission body 3 having a front end surface 3a disposed on the focal plane P or near the focal plane P. The transmitted image is captured by an imaging element 13 (see Figure 7A ) disposed on the base end side of the image transmission body 3.

[0075] In this case, according to the image transmission unit 1 according to the present embodiment, the objective lens 2 is composed of only one spherical segment lens, and the front end surface 3a of the image transmission body 3 is disposed on the focal plane P of the objective lens 2 or near the focal plane P. Therefore, the light exiting from the convex spherical surface 2b is incident on the front end surface 3a without reducing the image height. Further, the image transmission body 3 has a radius d larger than r / n, and the light is also incident on the outermost periphery of the front end surface 3a. Thereby, the inner diameter dimension of the holding member 4 defined by the diameter of the objective lens 2 can be effectively utilized to transmit a high-resolution image.

[0076] In particular, when the outer diameter of the image transmission body 3 is equal to or substantially equal to the inner diameter of the holding member 4, all or substantially all of the inner diameter of the holding member 4 can contribute to the resolution, and the resolution can be effectively improved.

[0077] Figure 12 An existing image transmission unit 101 is shown. The image transmission unit 101 includes two spherical segment lenses 2A and 2B, a first holding member 4A for holding the two spherical segment lenses 2A and 2B, an image transmission body 103, and a second holding member 4B for holding the first holding member 4A and the image transmission body 103. The second holding member 4B is disposed outside the first holding member 4A.

[0078] In the image transmission unit 101, there is a spherical segment lens 2B on the base end side, so that the image height h is small with respect to the diameter of the spherical segment lens 2A. Therefore, when an image transmission body 103 having a radius d equal to the image height h is used, a region Δ that is not projected and does not contribute to the resolution is generated on the radially outer side of the image transmission body 103. On the other hand, when an image transmission body 103 having a radius d equal to the inner diameter is used, as described above, the peripheral region of the image transmission body 103 does not contribute to the transmission of the image. Therefore, in any case, the inner diameter of the holding member 4B cannot be effectively utilized to improve the resolution.

[0079] When the image transmission unit 1 is used as an illumination optical system, illumination light is provided from the light source device to the image transmission body 3 through the base end surface 3b. The illumination light transmitted by the image transmission body 3 is emitted from the front end surface 3a, enters the objective lens 2 through the convex spherical surface 2b, and is irradiated toward the object from the flat surface 2a.

[0080] In this case, it is also advantageous to use the image transmission body 3 having a radius d larger than r / n. That is, as the radius d increases, the amount of illumination light that can be transmitted by the image transmission body 3 increases. Also, the illumination light emitted from the front end surface 3a efficiently passes through the objective lens 2 and is irradiated toward the object. Therefore, the inner diameter dimension of the holding member 4 defined by the diameter of the objective lens 2 can be effectively utilized to achieve bright illumination.

[0081] Further, according to the image transmission unit 1 according to the present embodiment, both the objective lens 2 and the image transmission body 3 are held within a single holding member 4. Thereby, miniaturization of the image transmission unit 1 can be achieved.

[0082] Assume that the image transmission unit 1 includes two holding members 4A and 4B as in the conventional image transmission unit 101. In this case, the outer diameter of the image transmission unit 1 increases by an amount corresponding to the thickness of the side wall of the second holding member 4B, and a region Δ that does not contribute to the resolution is generated between the outer peripheral surface of the image transmission body 3 and the inner peripheral surface of the second holding member 4B.

[0083] Further, since the objective lens 2 is larger than a hemisphere, an aperture stop 6 formed of a light-shielding member 5 can be formed between the front end surface 4a and the flat surface 2a on the front end surface 1a of the image transmission unit 1, and the objective lens 2 can be firmly fixed to the holding member 4 by frictional force.

[0084] An embodiment of the image transmission unit 1 is shown below.

[0085] [Table 1]

[0086]

[0087]

[0088] Next, a manufacturing method of the image transmission unit 1 will be described.

[0089] As Figures 5A to 5F shown, the manufacturing method of the image transmission unit 1 includes the following steps: Step S1, inserting a single spherical lens 2' into the holding member 4; Step S2, applying an adhesive 5' on the front end surface of the spherical lens 2'; Step S3, forming the flat surface 2a on the spherical lens 2' to fabricate the objective lens 2; Step S4, inserting the image transmission body 3 into the holding member 4; and Step S5, positioning the objective lens 2 and the image transmission body 3 relative to each other.

[0090] In step S1, a ball lens 2' is press-fitted into the front end portion of the holding member 4 to form an assembly composed of the ball lens 2' and the holding member 4 (see Figure 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.

[0091] Next, in step S2, a black adhesive 5' is disposed on the front end face of the assembly, and the adhesive 5' is filled into the gap between the front end face of the ball lens 2' and the inner surface of the front end portion of the holding member 4 (see Figure 5B ). Then, the adhesive 5' is cured. In the case of manufacturing the image transmission unit 1 that does not include the light-shielding member 5, step S2 can also be omitted.

[0092] Next, in step S3, the front end portion of the assembly is ground using a tool (see Figure 5C ). The grinding direction is the direction orthogonal to the long side axis of the holding member 4. By grinding, the front end portion of the holding member 4 and a part of the ball lens 2' are removed to form a flat surface 2a. In the case where the black adhesive 5' is filled in step S2, the adhesive 5' is also ground together with the ball lens 2' and the holding member 4, and a diaphragm 6 composed of the light-shielding member 5 is formed while forming the flat surface 2a. In step S3, a plurality of assemblies arranged in parallel can also be ground simultaneously.

[0093] Next, in step S4, an image transmission body 3 is inserted into the base end portion of the holding member 4 (see Figure 5D ). Optionally, an adhesive for fixing the image transmission body 3 to the holding member 4 can be applied to at least one of the outer peripheral surface of the image transmission body 3 and the inner peripheral surface of the holding member 4.

[0094] Next, in step S5, the distance WD is adjusted to position the front end face 3a of the image transmission body 3 at or near the focal plane P. An optical index is used in the adjustment of the distance WD. In one example, as Figure 5E shows, an object O is disposed in front of the objective lens 2, and an image of the object O is formed behind the image transmission body 3. The image transmission body 3 is positioned at the position where the image is in focus. In another example, as Figure 5F shows, illumination light is provided to the image transmission body 3, and the illumination light is irradiated onto a screen S in front of the objective lens 2. The image transmission body 3 is positioned at the position where the image of the illumination light on the screen S becomes the clearest.

[0095] When manufacturing the image transmission unit 1 having the spacer 7, between step S3 and step S4, the spacer 7 is inserted into the holding member 4. The image transmission body 3 is inserted into the holding member 4 until the convex spherical surface 2b and the front end surface 3a abut against both surfaces of the spacer 7, whereby the front end surface 3a is positioned at an appropriate position. Therefore, there is no need to perform the adjustment operation of the distance WD as in Figure 5E and Figure 5F that.

[0096] Thus, according to the manufacturing method according to the present embodiment, by simply press-fitting the ball lens 2' into the holding member 4, the center of curvature of the convex spherical surface 2b is arranged on the central axis of the holding member 4. That is, there is no need to adjust the position of the ball lens 2' relative to the holding member 4, and high positional accuracy of the objective lens 2 relative to the holding member 4 can be achieved.

[0097] In addition, according to the manufacturing method according to the present embodiment, by simply press-fitting the ball lens 2' into the holding member 4, the ball lens 2' is fixed to the holding member 4, and as described above, there is no need to adjust the position of the ball lens 2' relative to the holding member 4. And since both the ball lens 2' and the image transmission body 3 are inserted into one holding member 4, the number of assembled components and the number of assembly processes are small. Therefore, the image transmission unit 1 can be easily assembled.

[0098] In the present embodiment, it is assumed that the image transmission body 3 is a fiber bundle or a relay optical system, but instead, it may be an imaging element.

[0099] In this case, the imaging surface (front end surface) of the imaging element is arranged on the focal plane P of the objective lens 2 or near the focal plane P. The optical image of the object formed on the imaging surface is converted into an electrical signal by the imaging element and transmitted in the form of an electrical signal through a signal cable. The radius d of the imaging element is, for example, the radius of the circumscribed circle of the rectangular imaging surface.

[0100] In the present embodiment, it is assumed that the light-shielding member 5 is composed of a black adhesive, but instead, it may be composed of other members.

[0101] For example, it may also be that in step S2, a transparent adhesive is used instead of the black adhesive 5', and after step S3, a light-shielding member 5 composed of a light-shielding film is formed on the front end surface 1a.

[0102] (Second Embodiment)

[0103] Next, the image transmission unit according to the second embodiment of the present invention will be described with reference to the drawings.

[0104] As Figure 6As shown, the image transmission unit 10 according to this embodiment uses a relay optical system composed of a GRIN (gradient index) lens 8 as an image transmission body.

[0105] In this embodiment, structures different from those of the first embodiment will be described, and the same reference numerals will be given to the structures identical to those of the first embodiment and the description thereof will be omitted.

[0106] 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 for holding both the objective lens 2 and the GRIN lens 8.

[0107] The GRIN lens 8 is arranged along the optical axis A on the convex spherical surface 2b side (base end side) of the objective lens 2. The GRIN lens 8 has a front end surface 8a facing the convex spherical surface 2b. The front end surface 8a may be in contact with the convex spherical surface 2b or may be away from the convex spherical surface 2b.

[0108] The front end surface 8a may also be a flat surface.

[0109] The front end surface 8a may also be a spherical surface convex toward the convex spherical surface 2b. In this case, the front end surface 8a is arranged 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 front end surface 8a is a convex surface that functions as a lens, thereby enabling the viewing angle of the image transmission unit 10 to be expanded. The convex surface 8a is formed, for example, on the flat front end surface of the GRIN lens by an optical adhesive.

[0110] The light emitted from the convex spherical surface 2b toward the GRIN lens 8 includes expanding light that expands in the radial direction. The expanding light reaches the outermost periphery within the GRIN lens 8, and the light passing through the plane 2a includes the light passing through the outermost periphery of the GRIN lens 8.

[0111] The objective lens 2 and the GRIN lens 8 satisfy the following formula (1).

[0112] r / n < d ≤ r…(1)

[0113] 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, since the radius d is within the range of formula (1), the image formed by the objective lens 2 can be transmitted with high resolution.

[0114] The image transmission unit 10 may also include a light-shielding member 5.

[0115] The image transmission unit 10 may also not include a light-shielding member 5 (i.e., the diaphragm 6). The light that can propagate within the GRIN lens 8 is limited by the vignetting on the side surface of the GRIN lens 8. Thus, even if the diaphragm 6 does not exist, the brightness of the image transmission unit 10 can be defined by the GRIN lens 8. Correlatively, as Figure 6 shown, the radius R of the plane 2a may also be greater than r / n, or may satisfy the formula (2) as in the first embodiment.

[0116] The image transmission unit 10 of the present embodiment is used as an objective lens optical system in the same way as the image transmission unit 1 of the first embodiment, and is used as a camera optical system or an illumination optical system, for example.

[0117] According to the image transmission unit 10, the objective lens 2 is composed of only one spherical segment lens, and the light emitted from the convex spherical surface 2b enters the front end surface 8a without reducing the image height. And the GRIN lens 8 has a radius d larger than r / n, and the light also enters the outermost periphery of the GRIN lens 8. Thus, when used as a camera optical system, the inner diameter dimension of the holding member 4 defined by the diameter of the objective lens 2 can be effectively utilized to transmit a high-resolution image.

[0118] In addition, since the GRIN lens 8 has a radius d larger than r / n, when used as an illumination optical system, bright illumination can be achieved.

[0119] In addition, both the objective lens 2 and the GRIN lens 8 are held within a single holding member 4. Thus, miniaturization of the image transmission unit 10 can be achieved.

[0120] In addition, since 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.

[0121] Next, an embodiment of the image transmission unit 10 is shown.

[0122] [Table 2]

[0123]

[0124] Next, a manufacturing method of the image transmission unit 10 according to the present embodiment will be described.

[0125] The manufacturing method of the image transmission unit 10 includes step S1, step S2, step S31, and step S41. In step S31, the GRIN lens 8 is inserted into the holding member 4, and in step S41, the objective lens 2 and the GRIN lens 8 are positioned relative to each other.

[0126] In step S41, the GRIN lens 8 is positioned such that the front end face 8a is disposed on the convex spherical surface 2b side with respect to the focal plane P. For example, the GRIN lens 8 is positioned such that the front end face 8a abuts against the convex spherical surface 2b or is disposed in the vicinity of the convex spherical surface 2b. Therefore, unlike step S4 of the first embodiment, it is not necessarily required to perform fine position adjustment of the GRIN lens 8.

[0127] According to the manufacturing method according to the present embodiment, similarly to the manufacturing method of the first embodiment, it is not necessary to perform position adjustment of the spherical lens 2' with respect to the holding member 4, and high position accuracy of the objective lens 2 with respect to the holding member 4 can be achieved. In addition, similarly to the manufacturing method of the first embodiment, the image transmission unit 10 can be easily assembled.

[0128] (Third Embodiment)

[0129] Next, an optical device according to a third embodiment of the present invention will be described.

[0130] In the present embodiment, a structure different from those of the first and second embodiments will be described, and the same descriptions as those of the first and second embodiments will be denoted by the same reference numerals and the descriptions thereof will be omitted.

[0131] As Figure 7A and Figure 7B shown, the optical device 20 according to the present embodiment is an endoscope, and includes an image transmission unit 11, an illumination optical system 12, an imaging element (optical element) 13, and a cylindrical member 14. Figure 7A A rigid endoscope is shown, Figure 7B A flexible endoscope is shown.

[0132] 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 the image transmission unit 1 including an image transmission body 3 such as a fiber bundle or a relay optical system, but instead, it may be the image transmission unit 10 including a GRIN lens 8. The objective lens 2 is disposed at the front end of the long insertion portion 21 of the endoscope 20 and is used to form an image of an object. The image transmission body 3 extends in the longitudinal direction of the insertion portion 21 and is used to transmit the image of the object to the imaging element 13.

[0133] The illumination optical system 12 has one or more optical fibers 12a, preferably a plurality of optical fibers 12a. As Figure 8As shown, a plurality of optical fibers 12a are arranged between the holding member 4 and the cylinder member 14 along the long side direction of the members 4 and 14, and are arranged circumferentially around the image transmission unit 11. The cylinder member 14 is a long tubular member, and the image transmission unit 11 and the illumination optical system 12 are accommodated therein.

[0134] The front ends of the respective optical fibers 12a are arranged on the front end face of the insertion portion 21 (the front end face of the cylinder member 14), and the base ends of the respective optical fibers 12a are optically connected to the light source device. Each optical fiber 12a guides the illumination light provided from the light source device to the base end, and irradiates the illumination light from the front end toward the object.

[0135] The imaging element 13 is arranged on the base end side of the image transmission body 3, and is configured to capture the image transmitted by the image transmission body 3 to generate an image signal and output the image signal. An imaging lens 15 may also be arranged between the base end face 3b of the image transmission body 3 and the imaging element 13. The imaging lens 15 is configured to form an image of the object transmitted by the image transmission body 3 on the imaging surface 13a of the imaging element 13.

[0136] Figure 9 An example of an endoscope system 100 including an endoscope 20 is shown.

[0137] The endoscope system 100 includes an endoscope 20, a housing portion 30, and a display portion 40.

[0138] The endoscope 20 has a long insertion portion 21 and an imaging portion 22 connected to the base end of the insertion portion 21. The image transmission unit 11 and the illumination optical system 12 are arranged in the insertion portion 21, and the imaging element 13 and the imaging lens 15 are arranged in the imaging portion 22.

[0139] The imaging portion 22 is detachably connected to the base end of the insertion portion 21 through a connection portion 23, whereby the insertion portion 21 can be replaced.

[0140] The imaging portion 22 may also be integrated with the housing portion 30. That is, the housing portion 30 may be connected to the base end of the insertion portion 21, and the imaging element 13 and the imaging lens 15 may be arranged in the housing portion 30.

[0141] The housing portion 30 includes an illumination portion (light source device) 31 and an image processing portion 32.

[0142] The illumination portion 31 has a light source 31a, and the base ends of a plurality of optical fibers 12a led out from the base end portion of the insertion portion 21 are optically connected to the light source 31a. The illumination portion 31 may also further include a focusing lens 31b arranged between the light source 31a and the base ends of the plurality of optical fibers 12a. The focusing lens 31b focuses the light emitted from the light source 31a on the base end of the optical fiber 12a.

[0143] The image processing unit 32 has, for example, a processor and a memory. The image processing unit 32 generates an image of an object based on the image signal output from the imaging element 13 and outputs the image to the display unit 40.

[0144] The display unit 40 is an arbitrary display device such as a liquid crystal display, and is configured to display the image input from the image processing unit 32.

[0145] Thus, according to the present embodiment, the endoscope 20 can be configured by combining the image transmission unit 11 and the illumination optical system 12. In addition, the endoscope 20 having either a rigid or a flexible property can be manufactured by appropriately selecting the image transmission body 3 or 8.

[0146] In addition, by using the image transmission unit 11 as the imaging optical system, it is possible to easily realize the endoscope 20 having a thin insertion portion 21 and a high image resolution. Therefore, the endoscope 20 and the endoscope system 100 are suitable for use in a slender lumen such as a ureter.

[0147] In the present embodiment, the image transmission body 3 may be the imaging element 13. In this case, the imaging element 13 and the objective lens 2 are disposed at the front end portion of the insertion portion 21. The image signal output from the imaging element 13 is transmitted to the image processing unit 32 through a signal cable passing through the insertion portion 21.

[0148] Next, a method for manufacturing the optical device 20 will be described.

[0149] Figures 10A to 10D A part of the manufacturing method of the optical device 20 is shown. The manufacturing method of the optical device 20 includes the following steps: Step S1, inserting a single spherical lens 2' into the holding member 4; Step S6, inserting the assembly and the optical fiber 12a into the cylindrical member 14; Step S21, coating an adhesive 5' on the front end surface of the spherical lens 2'; Step S31, forming a flat surface 2a on the spherical lens 2' to fabricate the objective lens 2; Step S4, inserting the image transmission body 3 into the holding member 4; and Step S5, positioning the objective lens 2 and the image transmission body 3 with respect to each other.

[0150] Steps S1, S4, and S5 are as described in the first embodiment.

[0151] After Step S1, in Step S6, the first assembly composed of the spherical 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 Figure 10A ). Thereby, a second assembly composed of the spherical lens 2', the holding member 4, the cylindrical member 14, and one or more optical fibers 12a is formed.

[0152] Next, in step S21, a black adhesive 5' is disposed on the front end face of the second assembly, and the adhesive 5' is filled in the space between the front end face of the ball lens 2' and the inner surface of the front end portion of the holding member 4, and in the space between the optical fiber 12a and the members 4 and 14 (see Figure 10B ). Next, the adhesive 5' is cured.

[0153] Next, in step S31, the front end portion of the second assembly is polished using a tool (see Figure 10C ). The polishing direction is a direction orthogonal to the long side axis of the holding member 4. By polishing, the end portions of the members 4 and 14, a part of the ball lens 2', and the front end portion of the optical fiber 12a are removed, and at the same time, a flat surface 2a and a diaphragm 6 are formed.

[0154] Next, steps S4 and S5 are performed in the same manner as in the first embodiment (see Figure 10D ). Optionally, a spacer 7 can be inserted into the holding member 4 between step S31 and step S4.

[0155] Thus, according to the manufacturing method according to the present embodiment, in step S21, the holding member 4, the cylinder member 14, and the optical fiber 12a are fixed all at once by coating and curing the adhesive 5' for forming the light-shielding member 5. Further, in step S31, the ball lens 2', the holding member 4, the cylinder member 14, and the optical fiber 12a are all polished at once. Thereby, the number of processes can be reduced and the optical device 20 can be easily manufactured.

[0156] (Fourth Embodiment)

[0157] Next, an optical device according to a fourth embodiment of the present invention will be described.

[0158] In the present embodiment, a structure different from those of the first to third embodiments will be described, and the same descriptions as those of the first to third embodiments will be given the same reference numerals and the descriptions thereof will be omitted.

[0159] As Figure 11 shown, the optical device 50 according to the present embodiment is a light scanning type illumination device, and includes an image transmission unit 11 and a light source device (optical element) 16.

[0160] 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 alternatively, it may be the image transmission unit 10 including a GRIN lens 8.

[0161] The light source device 16 is an optical scanner disposed on the proximal end side of the image transmission body 3, and includes a light source 16a and a scanning mechanism 16b that scans the 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 can scan the light incident on the base end surface 3b in the direction along the base end surface 3b (refer to the double-headed arrow), and preferably, can scan the light over the entire surface of the base end surface 3b.

[0162] 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 constitute a collimating optical system. The first lens 16c converts the light output from the light source 16a into a parallel light beam, and the second lens 16d converts the parallel light scanned by the scanning mechanism 16b into focused light.

[0163] The light scanned by the scanning mechanism 16b enters the image transmission body 3 through the base end surface 3b, is transmitted by the image transmission body 3, exits from the front end surface 3a, enters the objective lens 2 through the convex spherical surface 2b, and irradiates the object from the flat surface 2a.

[0164] The scanning mechanism 16b may also be an optical fiber scanner that scans light by vibrating the front end of an optical fiber. The optical fiber scanner includes an optical fiber and a piezoelectric or electromagnetic scanner that vibrates the front end of the optical fiber. The proximal end of the optical fiber is optically connected to the light source 16a, and while scanning the light, the light is incident on the base end surface 3b from the vibrating front end of the optical fiber. In this case, the first lens 16c is a condenser lens that converges the light output from the light source 16a to the proximal end surface of the optical fiber, and the second lens 16d is an enlarging lens that enlarges the light scanning range so that the light is scanned over the entire surface of the base end surface 3b.

[0165] Thus, according to the present embodiment, an illumination device 50 that irradiates or projects light onto an object can be manufactured by combining the image transmission unit 11 and the light source device 16. The illumination device 50 has a small diameter and can efficiently transmit light from the light source device to the object, and is thus particularly useful in scenarios such as robotic medicine where it is inserted into the treatment instrument channel of an endoscope and projects light onto tissues inside a living body.

[0166] In the present embodiment, it is assumed that the illumination device 50 is a scanning type illumination device, but it may also be a non-scanning type illumination device. That is, the light source device 16 may not include the optical scanner 16. In this case, the light output from the light source 16a is incident on all or substantially all of the base end surface 3b at the same time, and the entire illumination range of the object is irradiated at the same time.

[0167] As described above, the embodiments of the present invention and their modified examples have been described in detail. However, the present invention is not limited to the above-described embodiments and their modified examples, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

[0168] Description of Reference Numerals

[0169] 1, 10, 11: Image transmission unit; 2: Objective lens; 3: Image transmission body; 3a: Front end face; 4: Holding member; 4a: Front end face; 5: Light shielding member; 7: Spacer; 8: GRIN lens (image transmission body, relay optical system); 12: Illumination optical system; 13: Imaging element (optical element); 13a: Imaging surface; 14: Cylindrical member; 15: Imaging lens; 16: Light scanner (optical element, light source device); 20: Endoscope (optical device); 50: Illumination device (optical device); 100: Endoscope system.

Claims

1. An image transmission unit includes: A single objective lens composed of a single lens in the shape of a spherical segment having a flat surface and a convex spherical surface; An image transmission body disposed on the convex spherical surface side of the objective lens; and A single holding member for holding both the objective lens and the image transmission body, Among them, The objective lens and the image transmission body satisfy the following formula (1), The light passing through the flat surface includes the light passing through the outermost periphery of the image transmission body, r / n < d ≤ r … (1) Herein, r is the radius of the objective lens, n is the refractive index of the objective lens, d is the radius of the image transmission body.

2. The image transmission unit according to claim 1, wherein The holding member is a cylindrical member that houses the objective lens and the image transmission body, and the objective lens and the image transmission body are respectively disposed on the front end side and the base end side of the holding member, A light-shielding member that surrounds the flat surface is further provided between the front end surface of the holding member and the flat surface.

3. The image transmission unit according to claim 1, wherein The objective lens satisfies the following formula (2), R ≤ r / n … (2) Herein, R is the radius of the flat surface.

4. The image transmission unit according to claim 1, wherein A spacer disposed between the objective lens and the image transmission body is further included.

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

6. The image transmission unit according to claim 1, wherein The image transmission body is a fiber bundle, a relay optical system, or an imaging element, and has a front end surface disposed at a distance from the convex spherical surface, The front end surface is disposed at or near the focal plane of the objective lens.

7. The image transmission unit according to claim 1, wherein The image transmission body is a gradient refractive index lens, i.e., a GRIN lens.

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

9. An optical device includes an image transmission unit and an optical element, wherein The image transmission unit includes: a single objective lens composed of a single lens in the shape of a spherical segment having a flat surface and a convex spherical surface; an image transmission body disposed on the convex spherical surface side of the objective lens; and a single holding member for holding both the objective lens and the image transmission body, The optical element is disposed on the side of the image transmission body opposite to the objective lens, The objective lens and the image transmission body satisfy the following formula (1), The light passing through the flat surface includes the light passing through the outermost periphery of the image transmission body, r / n < d ≤ r … (1) Herein, r is the radius of the objective lens, n is the refractive index of the objective lens, d is the radius of the image transmission body.

10. The optical device according to claim 9, wherein The optical element is an imaging element that captures an image of an object formed by the objective lens and transmitted by the image transmission body.

11. The optical device according to claim 9, wherein An illumination optical system is further included, The illumination optical system has one or more optical fibers arranged circumferentially around the image transmission unit.

12. The optical device according to claim 9, wherein the optical element is a light source device that provides light to the image transmission body.

13. The optical device according to claim 12, wherein the light source device is an optical scanner that scans the light.

14. A method for manufacturing an image transmission unit, comprising: 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 grinding an end portion of the holding member and the spherical lens; and positioning the spherical lens having the flat surface and the image transmission body relative to each other at a position where light passing through the flat surface includes light passing through the outermost periphery of the image transmission body.

15. The method for manufacturing an image transmission unit according to claim 14, wherein before forming the flat surface, the method further includes: filling a space between an inner surface of the holding member and an outer surface of the spherical lens with a light-shielding member.

Images