Camera unit and endoscope

Abstract

To provide a camera unit 1 having a wide visual field with a small diameter.SOLUTION: A camera unit 1 includes: a tip end lens 10 having a first face 10SA and a second face 10SB on an opposite side of the first face 10SA, in which the second face 10SB is a recessed face; a lens unit 20 having a third face 20SA and a fourth face 20SB on an opposite side of the third face 20SA, in which the third face 20SA is arranged in the recessed face of the tip end lens 10, the lens unit having a plurality of optical elements 21-26; and an imaging element 32 having a light receiving face 32SA for receiving the light emitted from the fourth face 20SB of the lens unit 20.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a camera unit comprising a tip lens, a lens unit into which light focused by the tip lens is incident, and an imaging unit into which the light focused by the lens unit is incident, and to an endoscope having the camera unit. [Background technology]

[0002] Japanese Patent Application Laid-Open Publication No. 9-222568 discloses an endoscopic camera unit having a first lens holder frame to which a negative lens is attached at the tip. The subsequent lens group is attached to a second lens holder frame. The first and second lens holder frames are fixed together by an insulator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-222568 Summary of the Invention [Problem to be solved by the invention]

[0004] To make endoscopes less invasive, it is important to reduce the diameter and size of camera units. There is also a need for an efficient method of manufacturing camera units with multiple specifications, such as different fields of view.

[0005] An object of an embodiment of the present invention is to provide a camera unit with a small diameter and a wide field of view, and an endoscope that is minimally invasive and has a wide field of view. [Means for solving the problem]

[0006] The camera unit of the embodiment comprises a tip lens having a first surface and a second surface opposite the first surface, the second surface being concave, a lens unit having a third surface and a fourth surface opposite the third surface, the third surface being disposed within the concave surface of the tip lens, the lens unit including a plurality of optical elements, and an imaging element having a light receiving surface that receives light emitted from the fourth surface of the lens unit.

[0007] The endoscope of the embodiment has a camera unit, the camera unit having a first surface and a second surface opposite to the first surface, the second surface being a concave tip lens, a third surface and a fourth surface opposite to the third surface, the third surface being disposed within the concave surface of the tip lens, the endoscope is equipped with a lens unit including a plurality of optical elements, and an imaging element having a light receiving surface that receives light emitted from the fourth surface of the lens unit. [Effects of the Invention]

[0008] According to the embodiments of the present invention, it is possible to provide a camera unit with a small diameter and a wide field of view, and an endoscope that is minimally invasive and has a wide field of view. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a camera unit according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is an exploded perspective view of the camera unit of the first embodiment. [Figure 5] FIG. 5 is an exploded cross-sectional view of the camera unit of the first embodiment. [Figure 6] FIG. 6 is an exploded perspective view of the camera unit of the first embodiment. [Figure 7] FIG. 7 is an exploded cross-sectional view of the camera unit of the first embodiment. [Figure 8]FIG. 8 is a transparent top view of the camera unit of the first embodiment. [Figure 9] FIG. 9 is an enlarged view of the rectangular area enclosed by the dashed line in FIG. [Figure 10] FIG. 10 is a diagram for explaining the optical characteristics of the camera unit of the first embodiment. [Figure 11] FIG. 11 is a perspective cross-sectional view of a camera unit according to a first modification of the first embodiment. [Figure 12] FIG. 12 is a transparent top view of a camera unit according to a second modification of the first embodiment. [Figure 13] FIG. 13 is a perspective view of the endoscope according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] First Embodiment 1 to 3, the camera unit 1 of this embodiment has a front lens 10, a lens unit 20, and an imaging unit 30. The symbol O indicates the optical axis of the camera unit 1.

[0011] In the following description, the drawings based on each embodiment are schematic. The relationship between the thickness and width of each part, the thickness ratio of each part, and the relative angle are different from the actual configuration. The drawings also include parts with different dimensional relationships and ratios. Some components are not shown.

[0012] The tip lens 10 has a first surface 10SA and a second surface 10SB opposite the first surface. The tip lens 10 is a plano-concave lens in which the first surface 10SA is flat and the second surface 10SB is concave. For example, the concave surface of the tip lens 10 made of resin is spherical or aspherical.

[0013] The lens unit 20 has a third surface 20SA and a fourth surface 20SB opposite the third surface 20SA, and is a rectangular parallelepiped containing multiple optical elements 21-26. The first optical element 21 is a hybrid lens element with negative power, consisting of a glass plate 21A and a resin lens 21B. The hybrid lens element is manufactured using a molding method in which an appropriate amount of uncured resin is placed on a glass wafer, and a mold with a recessed portion having a predetermined inner surface shape is pressed against the resin. The molding method allows for the outer surface shape of the resin lens to be transferred to the inner surface shape of the mold, making it easy to manufacture aspherical lenses.

[0014] The second optical element 22 and the fourth optical element 24 are spacers. The third optical element 23 and the fifth optical element 25 are hybrid lens elements similar to the first optical element 21. The sixth optical element 26 is a glass filter that removes unnecessary infrared rays (for example, light with a wavelength of 700 nm or more). The multiple optical elements 21-26 are each bonded with an adhesive layer (not shown) made of transparent resin. The lens unit also has an aperture layer (not shown). The configuration of the lens unit of the present invention is not limited to the configuration of lens unit 20, but is set according to specifications.

[0015] The rectangular parallelepiped lens unit 20 is a so-called wafer-level optical system (WLO) that is fabricated by cutting a laminated wafer in which optical element wafers, each including a plurality of optical elements, are stacked.

[0016] The imaging unit 30 has a cover glass 31 and an imaging element 32 such as a CMOS image sensor. The imaging element 32 has a rectangular light-receiving surface 32SA that receives light emitted from the fourth surface 20SB of the lens unit 20. The imaging unit 30 is bonded to the fourth surface 20SB of the lens unit 20 with an adhesive layer (not shown) made of transparent resin. The lens unit 20 having the imaging unit 30 disposed therein may be produced by cutting a laminated wafer in which multiple optical element wafers and an imaging element wafer including multiple imaging elements 32 are bonded together.

[0017] The lens unit 20 has a so-called complete optical system that is designed to have optical properties that allow the lens unit 20 to focus a subject image on the image sensor 32. In other words, the lens unit 20 can be used alone as the optical system of a camera unit.

[0018] In camera unit 1, third surface 20SA of lens unit 20 is disposed within second surface 10SB (spherical recess R10) of tip lens 10, which is a concave surface.

[0019] The camera unit 1 has a lens system 29 (FIG. 1) in which a tip lens 10 having negative power is added to a lens unit 20 having complete optical characteristics. In other words, the lens unit 20 in which the tip lens 10 is disposed is called the lens system 29.

[0020] A camera unit 1 having lens system 29 has a wider field of view than a camera unit having lens unit 20. Furthermore, by combining multiple tip lenses 10 with different negative powers with multiple lens units 20 with the same optical characteristics, multiple lens systems 29 (camera units 1) with different viewing angles can be easily produced. Tip lens 10 is not limited to a plano-concave lens, and may be, for example, a convex-concave lens with curved surfaces on both sides.

[0021] As shown in FIGS. 4 and 5, the second surface 10SB and the third surface 20SA are fixed in place by connecting members 40. The four connecting members 40 are convex portions made of, for example, resin, and are arranged at the center positions of the four sides of the rectangular third surface 20SA. On the other hand, the concave second surface 10SB (spherical recess R10) has four concave portions 40R into which the convex portions of the four connecting members 40 fit. Although not shown, the connecting members 40 and the concave portions 40R are fixed with an adhesive. To easily insert the convex portions into the concave portions 40R, the convex portions of the connecting members 40 are preferably smaller than the openings of the concave portions 40R.

[0022] When the rectangular third surface 20SA of the rectangular parallelepiped lens unit 20 is pressed against the second surface 10SB (spherical recess R10) of the tip lens 10, the four corners C20 of the third surface 20SA abut against the second surface 10SB. As a result, there are gaps between the corners (sides) of the second surface 10SB and the third surface 20SA. Taking this gap into consideration, the depth of the recess 40R is set to be smaller than the length of the connecting member 40.

[0023] 6 and 7, connecting member 40 may be a protrusion disposed on second surface 10SB, which is a concave surface, and may have recesses 40R on third surface 20SA that fit with connecting member 40. In other words, four connecting members 40 may be disposed on second surface 10SB at positions corresponding to the centers of the four sides of rectangular third surface 20SA.

[0024] Alternatively, second surface 10SB may have a convex portion and a concave portion, and third surface 20SA may have a concave portion that fits with the convex portion of second surface 10SB, and a convex portion that fits with the concave portion of second surface 10SB.

[0025] The connecting member 40 is a rectangular parallelepiped pillar, but is not limited to this and may be, for example, cylindrical or hemispherical. The camera unit 1 having the connecting member 40 can accurately position the lens unit 20 at a predetermined position of the tip lens 10.

[0026] In camera unit 1, third surface 20SA, which is the tip surface of lens unit 20, is disposed inside second surface 10SB, which is the concave surface of tip lens 10. Therefore, camera unit 1 has a small length in the direction of optical axis O. Furthermore, because lens unit 20 does not have a holding frame for holding tip lens 10 at a predetermined position, camera unit 1 has a small diameter.

[0027] In the camera unit 1, the light receiving surface (effective imaging area) 32SA of the image sensor 32 is rectangular (square). Therefore, the four corners of the effective imaging area are the longest from the optical axis O (center), and the length (diagonal) of the four corners is 1, and the vertical and horizontal lengths of the effective imaging area are, for example, 0.7. In other words, the length from the optical axis O to the four corners of the effective imaging area is the maximum image height, and the vertical and horizontal lengths from the optical axis O are the 0.7 image height. Light rays are determined for each image height. Specifically, at the maximum image height, light rays that form a field of view of 120 degrees are determined, and at the 0.7 image height, light rays that form a field of view of, for example, 80 degrees are determined.

[0028] 8 and 9, the hatched periphery of the effective area EA indicates the height (ray height) of a ray corresponding to each image height when it crosses the first surface 10SA of the tip lens 10 when each image height of the image sensor 32 is captured two-dimensionally. This ray is affected by distortion of the optical system. Because the optical system of the lens unit 20 is wide-angle, the distortion is generally barrel-shaped. In contrast, the ray height at the first surface 10SA of the tip lens 10 is pincushion-shaped, as shown in FIG. 8. As the barrel-shaped distortion acts on the pincushion-shaped ray height of the tip lens 10, the ray received at the light-receiving surface 32SA has a rectangular image height.

[0029] The connecting member 40 of the camera unit 1 is disposed outside the effective area EA of the optical path. Therefore, the connecting member 40 does not affect the optical characteristics of the camera unit 1, and light outside the connecting member 40 can be collected. In other words, the distance L1 from the optical axis O of the connecting member 40 is smaller than the distance L2 of the maximum light ray from the optical axis O. In other words, the maximum light ray of the effective area EA is located outside the connecting member 40.

[0030] <Optical properties> As already explained, lens unit 20 has a complete optical system that can be used by itself. Therefore, in order to construct an optical system with new wider-angle characteristics by providing front lens 10 with negative power in lens unit 20, lens system 29 preferably has the following configuration.

[0031] <Configuration 1> To increase the angle of view of the lens system 29 while minimizing fluctuations in the image plane of the lens unit 20 and maintaining the aberration correction performance of the complete lens unit 20, it is preferable that the front lens 10 has a small refractive power and a long focal length fL2. For this reason, it is preferable that the ratio between the focal length fL2 of the front lens 10 and the focal length fL1 of the lens unit 20 is large.

[0032] Specifically, it is preferable that the focal length fL1 of the lens unit 20 and the focal length fL2 of the front lens 10 are configured to satisfy the following (Equation 1).

[0033] (Formula 1) -0.072 <fL1 / fL2<-0.035

[0034] If the focal length ratio (fL1 / fL2) is below the above range, the focal length fL2 becomes small, and therefore image plane fluctuations caused by the front lens 10 cannot be ignored. If the focal length ratio (fL1 / fL2) is above the above upper limit, the focal length fL1 becomes large, and therefore, if the focal length fL2 is reduced to widen the angle, image plane fluctuations caused by the front lens 10 also cannot be ignored.

[0035] <Configuration 2> If the viewing angle W1 of lens unit 20 is small, tip lens 10 requires a greater refractive power. For example, if the viewing angle W1 of lens unit 20 is 90 degrees, tip lens 10 that can obtain a viewing angle W2 of 140 degrees as lens system 29 will have too much refractive power, resulting in large fluctuations in the image plane and making it impossible to ensure an appropriate depth of field. For this reason, the viewing angle W1 is preferably 100 degrees or more, and particularly preferably 115 degrees or more.

[0036] Furthermore, if lens system 29 has a large field of view W2, the field of view W1 must be increased to prevent light vignetting, resulting in a larger diameter for tip lens 10. For this reason, the field of view W2 of lens system 29 is preferably 175 degrees or less, and particularly preferably 145 degrees or less.

[0037] It is preferable that the viewing angle W1 of the lens unit 20 and the viewing angle W2 of the lens system 29 are configured to satisfy the following (Equation 2).

[0038] (Formula 2) 0.7 <W1 / W2<0.86

[0039] If the ratio (W1 / W2) between the viewing angle W1 and the viewing angle W2 is below the lower limit, the viewing angle W1 becomes too small and image plane fluctuations cannot be ignored.If the ratio (W1 / W2) is above the upper limit, the viewing angle W1 becomes large and the diameter of the tip lens 10 becomes large.

[0040] <Configuration 3> It is preferable that the distance D between the tip lens 10 and the lens unit 20 on the optical axis O is small. Because the tip lens 10 has a small power (its focal length fL2 is long), the distance D has little effect on aberration and the focal position, but if the distance D is too large, the ray height increases and the diameter of the tip lens 10 becomes large.

[0041] It is preferable that the ratio (D / fL1) of the distance D between the front lens 10 and the lens unit 20 to the focal length fL1 of the lens unit 20 is configured to satisfy the following (Equation 3).

[0042] (Formula 3) 0.2 <D / fL1<0.5

[0043] If the ratio (D / fL1) of the distance D to the focal length fL1 is below the lower limit, the focal length fL1 becomes large, and aberrations and image plane fluctuations become unignorable. If the ratio (D / fL1) is above the upper limit, the ray height becomes high, and the diameter of the tip lens 10 becomes large.

[0044] The optical characteristics of the lens system 29 (lens unit 20 in which the tip lens 10 is disposed) are, for example, as follows. Viewing angle of lens unit 20: W1 = 120 degrees Lens system 29 field of view: W2 = 140 degrees W1 / W2=0.857 The focal length of the lens unit 20: fL1 = 0.418 mm Focal length of tip lens 10: fL2 = -10.640 mm fL1 / fL2=-0.039 Distance between tip lens 10 and lens unit 20: D = 0.100 mm D / fL1=0.239

[0045] <Modification of the first embodiment> Camera units 1A and 1B of the modified examples of the first embodiment are similar to camera unit 1 of the embodiment and have the same effects as camera unit 1. For this reason, components with the same functions as camera unit 1 are given the same reference numerals and descriptions thereof will be omitted.

[0046] <Modification 1 of the First Embodiment> 11 shows a front lens 10A of a camera unit 1A that is cylindrical with a circular shape in the direction perpendicular to the optical axis. Furthermore, front lens 10A is a hybrid lens made up of a glass plate 11 and a resin lens 12. In camera unit 1, front lens 10 may also be cylindrical or a hybrid lens.

[0047] Furthermore, the camera unit 1A includes a transparent resin 50 that fills the space between the second surface 10SB of the tip lens 10A and the third surface 20SA of the lens unit 20. The refractive index of the transparent resin 50 is smaller than the refractive index of the resin lens 12.

[0048] After uncured transparent resin is disposed on the second surface 10SB of the tip lens 10A, a curing process (UV irradiation, heat treatment) is performed with the third surface 20SA of the lens unit 20 in contact with the second surface 10SB. Alternatively, a dummy member that is slightly larger than the lens unit 20 and is easy to release may be disposed on the second surface 10SB, and then the transparent resin may be disposed and cured. After the dummy member is removed, the lens unit 20 may instead be inserted and fixed in a hole in the transparent resin formed by the dummy member.

[0049] In camera unit 1A, transparent resin 50 functions as a connecting member. Camera unit 1A may further include a connecting member similar to that of camera unit 1 in addition to transparent resin 50.

[0050] <Modification 2 of the First Embodiment> 12, the light receiving surface 32SA (effective imaging area) of the image sensor 32 is circular, although this is not shown. Three hemispherical connecting members 40 are arranged rotationally symmetrically around the optical axis O in the spherical recess R10 of the end lens 10B, which is cylindrical like the end lens 10A. Three recesses 40R are provided on the third surface 20SA of the lens unit 20 at positions corresponding to the three hemispherical connecting members 40.

[0051] In camera unit 1B, effective area EA on first surface 10SA is circular. Length L1 of connecting member 40 from optical axis O is smaller than second length L2 from optical axis O of the maximum light ray.

[0052] Like the camera units 1 and 1A, the camera unit 1B is short in the direction of the optical axis O and also short in the direction perpendicular to the optical axis O.

[0053] Second Embodiment 13, an endoscope 9 of this embodiment includes an insertion section 9A, a grip section 9E extending from the base end of the insertion section 9A, and a universal cord 9F extending from the grip section 9E. The insertion section 9A includes a tip section 9B, a bending section 9C extending from the tip section 9B for changing the direction of the tip section 9B, and a flexible section 9D extending from the bending section 9C. A camera unit 1 (1A, 1B) is provided at the tip section 9B.

[0054] The universal cord 9F is connected to the light source device 8 and the processor 7. Illumination light generated by the light source device 8 passes through a light guide (not shown) that passes through the universal cord 9F and the insertion portion 9A, and is emitted from the distal end portion 9B to illuminate the subject. The processor 7 controls the entire endoscope system 2, performs signal processing on the imaging signal, and outputs an image signal. The monitor 6 displays the image signal output by the processor 7 as an endoscopic image. The endoscope 9 is a so-called flexible endoscope, but a rigid endoscope may also be used. The endoscope 9 may be for either medical or industrial use.

[0055] The endoscope 9 of the embodiment is minimally invasive and has a wide field of view because it has a small and thin camera unit 1. Furthermore, a plurality of types of endoscopes 9 with different viewing angles can be easily manufactured.

[0056] The ranges of the numerical values ​​described above are not limited to the ranges described above and can be increased or decreased as appropriate. Furthermore, the present invention is not limited to the above-described embodiments, and various changes and modifications can be made within the scope of the present invention. [Explanation of symbols]

[0057] 1, 1A, 1B...Camera unit 2. Endoscope system 9. Endoscopy 10, 10A, 10B... Tip lens 11. Glass plate 12. Resin lens 20 Lens unit 21...First optical element 21A Glass plate 21B···Resin lens 22...Second optical element 23...Third Optical Element 24...Fourth Optical Element 25. The fifth optical element 26...6th Optical Element 29 Lens System 30 Imaging unit 31. Cover glass 32. Image sensor 32SA... Light receiving surface 40....Connecting member 40R recess 50···Transparent resin

Claims

1. a tip lens having a first surface and a second surface opposite to the first surface, the second surface being concave; a lens unit including a third surface and a fourth surface opposite to the third surface, the third surface being disposed within the concave surface of the tip lens, and including a plurality of optical elements; an imaging element having a light receiving surface that receives light emitted from the fourth surface of the lens unit.

2. 2. The camera unit according to claim 1, wherein four corners of the rectangular third surface abut against the second surface.

3. a connecting member connecting the second surface and the third surface, the connecting member is a convex portion on the second surface or the third surface, 3. The camera unit according to claim 2, wherein the second surface or the third surface has a recess that fits with a protrusion of the connecting member.

4. the light receiving surface of the imaging element is rectangular, 4. The camera unit according to claim 3, wherein a first length from the optical axis of the connecting member is smaller than a second length from the optical axis of the outermost maximum light ray through which light incident on the image sensor passes on the first surface.

5. 4. The camera unit according to claim 3, wherein the connecting member is disposed at a center position of a side of the rectangular third surface or at a position corresponding to the center position of the second surface.

6. 3. The camera unit according to claim 2, further comprising a transparent resin filling a space between the second surface of the tip lens and the third surface of the lens unit.

7. 2. The camera unit according to claim 1, wherein a focal length fL1 of the lens unit and a focal length fL2 of the tip lens are configured to satisfy the following (Equation 1): [Equation 1] -0.072<fL1 / fL2<-0.035

8. 2. The camera unit according to claim 1, wherein a field of view W1 of the lens unit and a field of view W2 of the lens unit in which the tip lens is disposed satisfy the following (Equation 2): [Equation 2] 0.7<W1 / W2<0.86

9. The viewing angle W1 is 100 degrees or more, 9. The camera unit according to claim 8, wherein the viewing angle W2 is equal to or greater than 120 degrees and equal to or less than 150 degrees.

10. 2. The camera unit according to claim 1, wherein a distance D between the tip lens and the lens unit and a focal length fL1 of the lens unit are configured to satisfy the following (Equation 3): [Equation 3] 0.2<D / fL1<0.5

11. a camera unit, the camera unit comprising: a tip lens having a first surface and a second surface opposite to the first surface, the second surface being concave; a lens unit including a third surface and a fourth surface opposite to the third surface, the third surface being disposed within the concave surface of the tip lens, and including a plurality of optical elements; an imaging element having a light receiving surface that receives light emitted from the fourth surface of the lens unit.

Images