CN113267940A - Optical unit and imaging device - Google Patents

Abstract

The invention provides an optical unit and an image pickup apparatus, wherein a switching filter can be arranged between a bayonet on which an imaging lens is detachably mounted and a dichroic prism. The optical unit includes: a bayonet to which the imaging lens is detachably attached; and a dichroic prism for color-decomposing an incident light flux incident through the imaging lens. The flange pitch of the optical unit is 20mm or less in terms of air conversion length, and the optical unit has a switchable filter capable of switching filter characteristics, which is disposed between the bayonet and the dichroic prism.

Description

Optical unit and imaging device

Technical Field

The present invention relates to an optical unit and an imaging apparatus.

Background

The technique described in patent document 1 provides a color separation optical system, an imaging unit, and an imaging device that can suppress the occurrence of color shading. The dichroic optical system is configured by combining a 1 st prism for extracting B light, a 2 nd prism for extracting R light, a 3 rd prism for extracting IR light, and a 4 th prism for extracting G light. The 1 st prism reflects and separates the B light from the 2 nd surface of the 1 st prism. The 2 nd prism reflects and separates the R light by the 2 nd surface of the 2 nd prism. The 3 rd prism reflects and separates the IR light from the 2 nd surface of the 3 rd prism. The dichroic optical system is configured such that a surface on which the incident angle of light passing through the optical axis is maximized becomes the 2 nd surface of the 3 rd prism.

Patent document 1: international publication No. 2018/216386

Disclosure of Invention

One embodiment according to the present technology provides an optical unit and an imaging device in which a switching filter can be disposed between a bayonet on which an imaging lens is mounted and a dichroic prism.

A 1 st aspect according to the present technology is an optical unit including: a bayonet to which the imaging lens is detachably attached; and a dichroic prism for color-resolving an incident light flux incident through the imaging lens, wherein the flange pitch is 20mm or less in an air conversion length, and the optical unit has a switchable filter capable of switching filter characteristics, which is disposed between the bayonet and the dichroic prism.

A 2 nd aspect according to the technology of the present invention is the optical unit according to the 1 st aspect, wherein the bayonet satisfies the standard of the C bayonet.

A 3 rd aspect according to the technique of the present invention is the optical unit according to the 1 st or 2 nd aspect, wherein a distance from the bayonet surface of the bayonet to the incident surface of the dichroic prism is 8.2mm or more in actual length.

A 4 th aspect of the present invention is the optical unit according to the 3 rd aspect, including: a housing accommodating the switching type filter; a 1 st transparent plate disposed on an incident side of the switching filter in the housing; and a 2 nd transparent plate disposed on the emission side of the switching filter in the case.

A 5 th aspect of the present invention relates to the optical unit according to the 4 th aspect, wherein the bayonet is provided in the housing, and the 1 st transparent plate is provided on a surface of the bayonet facing the switching filter.

The 6 th aspect relating to the technique of the present invention is the optical unit according to any one of the 1 st to 6 th aspects, wherein an image sensor is disposed on each of the emission surfaces of the dichroic prism via an adhesive layer.

A 7 th aspect of the present invention relates to the optical unit according to the 6 th aspect, wherein the adhesive layer is formed on the entire surface or a part of each of the emission surfaces.

An 8 th aspect relating to the technology of the present invention is the optical unit according to the 7 th aspect, wherein a compensation filter is provided on each emission surface, and the image sensor is disposed on the compensation filter via an adhesive layer.

A 9 th aspect according to the present invention is the optical unit according to any one of the 1 st to 8 th aspects, wherein the switchable filter is a rotary switchable turret filter.

A 10 th aspect relating to the technology of the present invention is an imaging device including: the optical unit according to any one of claims 1 to 9; a camera body accommodating the optical unit; and an imaging lens detachably attached to the bayonet.

Drawings

Fig. 1 is a schematic perspective view showing a configuration of a camera as an example of an imaging apparatus.

Fig. 2 is an exploded perspective view of the optical unit as viewed from the entire surface side.

Fig. 3 is an exploded perspective view of the optical unit as viewed from the back side.

Fig. 4 is a perspective view of the optical unit as viewed from the back side.

Fig. 5 is a front view of the camera.

Fig. 6 is a sectional view taken along line a-a of fig. 5.

Fig. 7 is a sectional view of an enlarged main portion of the optical unit.

Fig. 8 is a schematic diagram showing an example of the structure of the G-light image sensor.

Fig. 9 is a table showing an example of the length and refractive index of a portion from the bayonet surface to the incident surface of the dichroic prism.

Fig. 10 is a table showing an example of the length and refractive index of each portion from the incident surface to the light receiving surface of the dichroic prism.

Fig. 11 is a block diagram showing an electrical configuration of the camera body.

Fig. 12 is a diagram showing a modification of the image sensor.

Detailed Description

An example of an embodiment according to the technology of the present invention will be described with reference to the drawings.

First, words used in the following description will be described.

ND is "Neutral Density: neutral density "for short. The CMOS is a Complementary Metal Oxide Semiconductor: complementary metal oxide semiconductor. CPU is "Central Processing Unit: the abbreviation of central processing unit. RAM is "Random Access memory y: random access memory ("ram") for short. ROM is "Read Only Memory: read-only memory.

Fig. 1 shows a configuration of a camera 2 as an example of an imaging apparatus. The camera 2 is a lens-interchangeable camera.

The camera 2 includes a box-shaped camera body 10, and an optical unit 20 is housed inside the camera body 10. The optical unit 20 is disposed at a predetermined position inside the camera body 10 via a bracket, not shown. The camera 2 is used as a monitoring camera, for example.

The camera body 10 has a 1 st opening 12 and a 2 nd opening 13 formed therein. The 1 st opening 12 is circular, and exposes a camera side mount 21 provided on the optical unit 20 to the outside of the camera body 10. The 2 nd opening 13 is circular, and exposes a rotation operation member 22 provided to the optical unit 20 to the outside of the camera body 10. The rotary operation member 22 can switch and operate a turret filter 60, which will be described later, provided inside the optical unit 20.

The imaging lens 30 is detachably attached to the camera mount 21. In the present embodiment, the camera side mount 21 satisfies the standard of the C mount, which is one of the screw mounts for fixing the camera and the lens with screws. The caliber of the C bayonet is 25.4mm (1 inch), the pitch of the screw threads is 0.794mm, and the flange pitch is 17.526mm (air converted length). The flange pitch is defined as an air-converted length of a distance from a bayonet surface of the bayonet to a light receiving surface of the image sensor.

The imaging lens 30 includes a barrel 31 and a lens mount 32. Lens mount 32 is provided at the base end of barrel 31. The lens mount 32 is configured to be connectable to the camera mount 21, because it satisfies the standard of the C mount.

Fig. 2, 3, and 4 show an example of the structure of the optical unit 20. Fig. 2 is an exploded perspective view of the optical unit 20 as viewed from the entire surface side. Fig. 3 is an exploded perspective view of the optical unit 20 as viewed from the back side. Fig. 4 is a perspective view of the optical unit 20 as viewed from the back side.

As shown in fig. 2 and 3, the optical unit 20 includes a base 40, a lid member 50, a turret filter 60, a rotation operation member 22, and a dichroic prism 70. The base 40 is a rectangular box-shaped member having an open entire surface. The cover member 50 has a rectangular flat plate shape, and is connected to the base 40 so as to cover the entire open surface side of the base 40.

Screw holes 41 into which screws 80 are screwed are formed at four corners of the base 40. Through holes 51 through which screws 80 are inserted are formed at four corners of the cover member 50 at positions corresponding to the screw holes 41. The cover member 50 is connected to the base 40 by inserting the screw 80 into the through hole 51 and screwing the screw into the screw hole 41. The turret filter 60 is accommodated in an internal space formed by the lid member 50 and the base body 40 being connected. The base 40 and the lid member 50 constitute a housing that accommodates the turntable filter 60. The turret filter 60 is an example of a switching filter capable of switching filter characteristics.

A shaft support portion 43 for rotatably supporting the turntable filter 60 is provided at the center portion of the inner bottom surface 42 of the base 40. The turntable filter 60 has a circular shape, and a shaft support hole 61 is provided at the center thereof. The shaft support portion 43 is inserted into the shaft support portion shaft support hole 61 of the turntable filter 60. The turret filter 60 rotates about the shaft support portion 43 as a rotation axis.

The turntable filter 60 has a disk shape, and a tooth 62 is formed on the outer periphery thereof. The tooth 62 engages with a gear 22A provided at the base end of the rotary operation member 22. The turret filter 60 rotates in accordance with the rotation of the rotation operation member 22. That is, the turret filter 60 is a rotary switching filter.

A through hole 44 into which the base end side of the rotational operation member 22 is inserted is formed in the inner bottom surface 42 of the base 40. A through hole 52 into which the distal end side of the rotation operation member 22 is inserted is formed in the cover member 50. The base end of the rotational operation member 22 is accommodated in an internal space formed by the base 40 and the lid member 50, and the tip end is exposed to the outside.

In this example, the turret filter 60 is provided with four types of filters, i.e., a 1 st filter 63A, a 2 nd filter 63B, a 3 rd filter 63C, and a 4 th filter 63D. Each filter is circular and disposed at a position rotationally symmetrical about the shaft support hole 61 of the shaft support portion. The filters sequentially pass through the optical axis Lz as the turret filter 60 rotates. The optical axis Lz is an optical axis of the imaging lens 30 attached to the camera mount 21.

The 1 st filter 63A, the 2 nd filter 63B, and the 3 rd filter 63C are, for example, light amount attenuation (N D) filters. For example, the 1 st filter 63A is an ND4 filter that reduces the amount of light to 1/4, the 2 ND filter 63B is an ND16 filter that reduces the amount of light to 1/16, and the 3 rd filter 63C is an ND64 filter that reduces the amount of light to 1/64. The 4 th filter 63D is a light-transmitting plate (e.g., transparent glass) having no light-reducing function.

The type of the filter provided in the turret filter 60 is not limited to the ND filter. As the filter of the turret filter 60, a color temperature conversion filter can be used. The color temperature conversion filter is a filter that attenuates red light and transmits blue light, thereby increasing the color temperature. In this case, for example, the 1 st filter 63A is a filter for raising the color temperature from 3200K to 4300K, the 2 nd filter 63B is a filter for raising the color temperature from 3200K to 6300K, and the 3 rd filter 63C is a filter for raising the color temperature from 3200K to 8000K. The 4 th filter 63D is a light-transmitting plate (for example, transparent glass) having no color temperature conversion function.

The types of filters provided in the turret filter 60 are not limited to the ND filter and the color temperature conversion filter. As the optical filter provided in the turret filter 60, a special effect filter, a wavelength selective filter, or the like can be used. The special effect filter includes a cross filter for providing a light bar (radial light beam) to a light source in a field of view, a diffusion filter for diffusing light of a bright portion to provide a soft impression, and the like. The wavelength selective filter includes a short wavelength transmission filter, a long wavelength transmission filter, a band pass filter, an infrared cut filter, and the like.

The plurality of filters provided in the turret filter 60 may be different types of filters or may be a combination of different types of filters. The number of filters included in the turret filter 60 is not limited to four, and may be three or less.

The cover member 50 is provided with the camera side mount 21 described above. The 1 st transparent plate 24 is provided on the bottom surface 23 of the camera mount 21. The 1 st transparent plate 24 is a circular cover glass centered on the optical axis Lz and faces the turret filter 60. The 1 st transparent plate 24 may be a filter having optical characteristics such as an infrared cut filter. The 1 st light-transmitting plate 24 may be transparent glass having no optical conversion function.

A2 nd transparent plate 45 is provided on the inner bottom surface 42 of the base 40 at a position corresponding to the 1 st transparent plate 24. The 2 nd transparent plate 45 is, for example, rectangular cover glass, and faces the turret filter 60. The 2 nd transparent plate 45 may be a filter having optical characteristics such as an infrared cut filter. A dichroic prism 70 is attached to the rear surface side of the base 40 so that an incident surface 71A faces the 2 nd transparent plate 45 via a frame-shaped spacer 46 (see fig. 3). The spacer 46 is attached to the back surface side of the base 40 so as to surround the periphery of the 2 nd transparent plate 45.

The 1 st transparent plate 24 and the 2 nd transparent plate 45 are provided in a housing including the base 40 and the lid member 50, which houses the turret filter 60, and dust-proof is provided for the turret filter 60.

A support 47 is bonded to a side surface of the dichroic prism 70. The dichroic prism 70 is attached to the base 40 by connecting the support body 47 to the support column 48 provided upright on the rear surface side of the base 40 (see fig. 4). The support body 47 and the support 48 are screwed by screws not shown.

Fig. 5 is a front view of the camera 2. Fig. 6 is a sectional view taken along line a-a of fig. 5. The cross section includes an optical axis Lz.

As described above, the camera side mount 21 provided on the camera body 10 satisfies the standard of the C mount, and the aperture D is 25.4mm (1 inch). Further, a female screw portion 21A is provided on an inner surface of the camera mount 21. The pitch of the female screw portion 21A is 0.794 mm.

Similarly, the lens-side bayonet 32 provided in the imaging lens 30 satisfies the standard of the C bayonet, and thus the aperture D is 25.4mm (1 inch). A male screw portion 32A is provided on an outer surface of the lens mount 32. The pitch of the male screw portion 32A is 0.794 mm.

The barrel 31 of the imaging lens 30 has a diameter larger than the lens mount 32, and houses a lens, a diaphragm, and the like therein. The imaging lens 30 is attached to the camera body 10 by screwing the male screw portion 32A of the lens mount 32 into the female screw portion 21A of the camera mount 21. When the imaging lens 30 is attached to the camera body 10, the rear end of the lens barrel 31 abuts against the bayonet surface 21B of the camera-side bayonet 21. The bayonet surface 21B is a plane including the end surface on the distal end side of the camera side bayonet 21 and perpendicular to the optical axis Lz. That is, the bayonet surface 21B is a reference surface that defines the position of the lens barrel 31 with respect to the optical axis direction of the camera body 10 by coming into contact with the lens barrel 31.

In the present embodiment, the dichroic prism 70 is a three-color dichroic prism that splits an incident light beam incident via the imaging lens 30 into red light (hereinafter, referred to as R light), green light (hereinafter, referred to as G light), and blue light (hereinafter, referred to as B light). The dichroic prism 70 is provided with an R-light image sensor 90R for receiving R light, a G-light image sensor 90G for receiving G light, and a B-light image sensor 90B for receiving B light.

The R-light image sensor 90R, G and the B- light image sensor 90G and 90B are each configured by the same image sensor. Hereinafter, when it is not necessary to distinguish between the R-light image sensor 90R, G and the B-light image sensor 90B, these sensors are simply referred to as image sensors. Each image sensor includes a cover glass 91 and a sensor substrate 92. Each image sensor is, for example, a 1/2.8 type (diagonal 6.43mm) CMOS image sensor.

The flange distance FB is a distance from the bayonet surface 21B to the light receiving surface of each image sensor in terms of air-converted length. Under the standard of C bayonet, the flange distance FB is 17.526mm (air conversion length). Thus, under the standard of the C bayonet, the flange distance FB is shorter. Conventionally, since the image sensor is attached to the dichroic prism 70 via a spacer or the like, the distance L from the bayonet surface 21B to the incident surface 71A of the dichroic prism 70 is short, and it is difficult to accommodate the switching filter such as the turret filter 60 in the optical unit 20.

In the technique of the present invention, each image sensor is directly connected to the dichroic prism 70, and the distance L is made longer than in the conventional technique by moving the incident surface 71A of the dichroic prism 70 to the rear end side. In the technique of the present invention, the distance L is set to a length that allows the switchable filter such as the turret filter 60 to be accommodated inside the optical unit 20. For example, the distance L is 9.811mm in actual length.

Fig. 7 is a sectional view of an enlarged main portion of the optical unit 20. As shown in fig. 7, the dichroic prism 70 is configured by combining three prisms, i.e., a 1 st prism 71, a 2 nd prism 72, and a 3 rd prism 73. The three prisms are arranged in the order of the 1 st prism 71, the 2 nd prism 72, and the 3 rd prism 73 from the light incident side along the optical axis Lz. Each prism is formed of, for example, barium flint glass (e.g., BaFD7 manufactured by HOYA Corporation). In the dichroic prism 70 of the present embodiment, B light is extracted by the 1 st prism 71, R light is extracted by the 2 nd prism 72, and G light is extracted by the 3 rd prism 73.

The 1 st prism 71 has a 1 st surface 71A, a 2 nd surface 71B, and a 3 rd surface 71C. The 1 st surface 71A is disposed so as to be orthogonal to the optical axis Lz, and functions as the incident surface 71A described above. The light incident on the dichroic prism 70 from the imaging lens 30 is transmitted through the 1 st surface 71A.

The 2 nd surface 71B intersects the optical axis Lz and is disposed so as to be inclined with respect to the optical axis Lz. A dichroic film (not shown) that reflects B light is formed on the 2 nd surface 71B. Of the light incident on the 2 nd surface 71B along the optical axis Lz, only the B light is selectively reflected by the 2 nd surface 71B. In this way, the 2 nd surface 71B functions as a photodecomposition surface. The B light reflected by the 2 nd surface 71B is incident on the 1 st surface 71A at a predetermined angle. The 1 st surface 71A also functions as a reflection surface. The 1 st surface 71A totally reflects the incident B light toward the 3 rd surface 71C.

The 3 rd surface 71C functions as a 1 st emission surface. The B light incident on the 3 rd surface 71C is emitted from the 3 rd surface 71C. The 1B-th and 2B-th optical compensation filters 75B1 and 75B2 are provided on the 3 rd surface 71C via the adhesive layer 74B. The 1B-th optical compensation filter 75B1 and the 2B-th optical compensation filter 75B2 are stacked. The 1B-th light compensation filter 75B1 and the 2B-th light compensation filter 75B2 cut off the light of the excessive color component from the B light to improve the color reproducibility of the B light. The compensation filter provided on the 3 rd surface 71C is not limited to a multilayer type, and may be a single layer.

The 2 nd prism 72 has a 1 st surface 72A, a 2 nd surface 72B, and a 3 rd surface 72C. The 1 st surface 72A functions as an incident surface. The 1 st surface 72A intersects the optical axis Lz and is arranged parallel to the 2 nd surface 71B of the 1 st prism 71. The 1 st surface 72A also functions as a bonding surface with the 1 st prism 71. The 1 st surface 72A is joined to the 2 nd surface 71B of the 1 st prism 71 via, for example, a frame-shaped spacer 76. In this way, the 1 st surface 72A and the 2 nd surface 71B are joined via the air gap 77. The light transmitted through the 2 nd surface 71B of the 1 st prism 71 enters the 1 st surface 72A of the 2 nd prism 72 via the air gap 77.

The 2 nd surface 72B intersects the optical axis Lz and is disposed so as to be inclined with respect to the optical axis Lz. A dichroic film (not shown) that reflects the R light is formed on the 2 nd surface 72B. Of the light incident on the 2 nd surface 72B along the optical axis Lz, only the R light is selectively reflected by the 2 nd surface 72B. In this way, the 2 nd surface 72B functions as a photodecomposition surface. The R light reflected by the 2 nd surface 72B is incident on the 1 st surface 72A at a predetermined angle. The 1 st surface 72A also functions as a reflection surface. The 1 st surface 72A totally reflects the incident R light toward the 3 rd surface 72C.

The 3 rd surface 72C functions as an emission surface. The R light incident on the 3 rd surface 72C exits from the 3 rd surface 72C. The 3 rd surface 72C is provided with an R optical compensation filter 75R via an adhesive layer 74R. The R light compensation filter 75R cuts off light of an excessive color component from the R light to improve color reproducibility of the R light.

The 3 rd prism 73 has a 1 st surface 73A and a 2 nd surface 73B. The 1 st surface 73A functions as an incident surface. The 1 st surface 73A intersects the optical axis Lz and is disposed parallel to the 2 nd surface 72B of the 2 nd prism 72. The 1 st surface 73A also functions as a bonding surface with the 2 nd prism 72. The 1 st surface 73A is bonded to the 2 nd surface 72B of the 2 nd prism 72 via an adhesive layer (not shown). The light transmitted through the 2 nd surface 72B of the 2 nd prism 72 is incident on the 1 st surface 73A.

The 2 nd surface 73B functions as an emission surface. The 2 nd surface 73B intersects the optical axis Lz and is disposed so as to be inclined with respect to the optical axis Lz. The light incident on the 1 st surface 73A is directly emitted from the 2 nd surface 73B. The light emitted from the 2 nd surface 73B is G light. The 2 nd surface 73B is provided with a G optical compensation filter 75G via an adhesive layer 74G. The G light compensation filter 75G cuts off light of an excessive color component from the G light to improve color reproducibility of the G light.

The G-light image sensor 90G is bonded to the G-light compensation filter 75G via the bonding layer 78G. In the present embodiment, the entire surface of the cover glass 91 of the G-light image sensor 90G is bonded to the surface of the G-light compensation filter 75G via the adhesive layer 78G. The G light having passed through the G light compensation filter 75G enters the sensor substrate 92 through the adhesive layer 78G and the cover glass 91.

Similarly, the R-light image sensor 90R is bonded to the R-light compensation filter 75R via the bonding layer 78R. In the present embodiment, the entire surface of the cover glass 91 of the R-light image sensor 90R is bonded to the surface of the R-light compensation filter 75R via the adhesive layer 78R. The R light having passed through the R light compensation filter 75R enters the sensor substrate 92 through the adhesive layer 78R and the cover glass 91.

Similarly, the B-light image sensor 90B is bonded to the 2B-th light compensation filter 75B2 via the bonding layer 78B. In the present embodiment, the entire surface of the cover glass 91 of the B-ray image sensor 90B is bonded to the surface of the 2B-th optical compensation filter 75B2 via the adhesive layer 78B. The B light having passed through the 1B-th light compensation filter 75B1 and the 2B-th light compensation filter 75B2 enters the sensor substrate 92 through the adhesive layer 78B and the cover glass 91.

The adhesive layers 74R, 74G, and 74B and the adhesive layers 74R, 74G, and 74B are formed of, for example, an ultraviolet curable adhesive.

Next, the length (actual length) of each portion along the optical axis Lz of the optical unit 20 will be described. An air layer (hereinafter, referred to as a 1 st air layer) 81 is formed from the bayonet surface 21B to the 1 st light-transmitting plate 24. The length of the 1 st air layer 81 is G1. The length of the 1 st transparent plate 24 is W1. An air layer (hereinafter, referred to as a 2 nd air layer) 82 is formed between the 1 st transparent plate 24 and the optical filter (the 1 st filter 63A in fig. 7) included in the turret filter 60. The length of the 2 nd air layer 82 is G2. The length of the 1 st filter 63A is W2.

An air layer (hereinafter, referred to as a 3 rd air layer) 83 is formed between the 1 st filter 63A and the 2 nd transparent plate 45. The length of the 3 rd air layer 83 is G3. The length of the 2 nd transparent plate 45 is W3. An air layer (hereinafter, referred to as a 4 th air layer) 84 is formed between the 2 nd transparent plate 45 and the incident surface 71A of the dichroic prism 70. The length of the 4 th air layer 84 is G4.

The distance L from the bayonet surface 21B to the incident surface 71A of the dichroic prism 70 is expressed by the following equation (1).

L＝G1+W1+G2+W2+G3+W3+G4……(1)

The refractive index of the 1 st transparent plate 24 is n1, the refractive index of the 1 st filter 63A is n2, and the refractive index of the 2 nd transparent plate 45 is n 3. The air-equivalent length La of the distance L at this time is expressed by the following formula (2).

La＝G1+W1/n1+G2+W2/n2+G3+W3/n3+G4……(2)

Next, the length along the optical axis Lz of the dichroic prism 70 is W4. The length of the air gap 77 along the optical axis Lz is G5. Here, the length W4 is set to a length excluding the length G5 of the air gap 77.

The length of the adhesive layer 74G along the optical axis Lz is W5, the length of the G optical compensation filter 75G is W6, the length of the adhesive layer 78B is W7, and the length of the cover glass 91 is W8. As shown in fig. 8, an air layer 93A is formed from the cover glass 91 to the light-receiving surface 92A of the sensor substrate 92, and the length of the air layer 93A is G6.

The refractive index of the dichroic prism 70 is n4, the refractive index of the adhesive layer 74G is n5, the refractive index of the G optical compensation filter 75G is n6, the refractive index of the adhesive layer 78B is n7, and the refractive index of the cover glass 91 is n 8. The flange gap FB (air equivalent length) at this time is represented by the following equation (3).

FB＝La+W4/n4+G5+W5/n5+W6/n6+W7/n7+W8/n8+G6……(3)

The filters included in the turret filter 60 each have the same length and refractive index as those of the 1 st filter 63A. Therefore, even if the filter is switched by the rotation of the turret filter 60, the air-equivalent length La of the distance L and the flange distance FB do not change.

The above equation (3) represents the flange distance FB on the optical path of the G light. The lengths of the flange pitches on the optical paths of the B light and the R light are set so that the flange pitches are the same as the flange pitch FB expressed by the above formula (3).

Fig. 8 is a schematic diagram showing an example of the structure of the G-light image sensor 90G. As shown in fig. 8, the G-ray image sensor 90G has a cover glass 91 bonded to a sensor substrate 92 having a light receiving surface 92A via a spacer 93 disposed so as to surround the light receiving surface 92A. The length G6 of the air layer 93A between the cover glass 91 and the light receiving surface 92A is set according to the thickness of the spacer 93. The periphery of the cover glass 91 and the sensor substrate 92 may be covered with a sealing member such as resin.

The G-light image sensor 90G photoelectrically converts G light, which is incident light, by a plurality of photodiodes constituting the light receiving surface 92A, thereby generating an image signal.

The R-light image sensor 90R and the B-light image sensor 90B have the same configuration as the G-light image sensor 90G.

Fig. 9 shows an example of the length and refractive index of each portion along the optical axis Lz in the portion from the bayonet surface 21B of the optical unit 20 to the incident surface 71A of the dichroic prism 70. As shown in fig. 9, by setting the actual length and refractive index of each portion, the distance L from the bayonet surface 21B to the incident surface 71A can be 9.811 mm. The distance L is a length that can accommodate a switching filter such as the turret filter 60 in the optical unit 20. The air equivalent length La of the distance L is 8.795 mm.

Fig. 10 shows an example of the length and refractive index of each portion along the optical axis Lz in the portion from the incident surface 71A of the dichroic prism 70 of the optical unit 20 to the light receiving surface 92A of the G-beam image sensor 90G. As shown in fig. 10, by setting the actual length and refractive index of each portion, the flange distance FB can be set to 17.526mm (air equivalent length) which is the standard of C-bayonet. The actual length of the flange from FB is 24.381 mm.

Since the air converted length is shortened by increasing the refractive index of the dichroic prism 70, the length of the dichroic prism 70 (air converted length) from the flange distance FB, which is the air converted length, is shortened, and the incident surface 71A can be moved to the rear end side. Thus, the distance L from the bayonet surface 21B to the incident surface 71A becomes longer, and the space for disposing the switching filter such as the turret filter 60 is enlarged.

Fig. 11 is a block diagram showing an electrical configuration of the camera body 10. As shown in fig. 11, the camera body 10 is provided with a microcomputer 100, an R-light image sensor driver 110R, G, a light image sensor driver 110G, B, a light image sensor driver 110B, R, an optical analog signal processing section 120R, G, an optical analog signal processing section 120G, and a B-light analog signal processing section 120B. These components are housed inside the camera body 10. The image sensor driver and the analog signal processing unit may be provided inside the corresponding image sensor.

The microcomputer 100 is composed of a CPU, a RAM, a ROM, and the like. The microcomputer 100 controls each unit according to a program stored in the rom, thereby realizing various functions.

The R-light image sensor driver 110R drives the R-light image sensor 90R in accordance with an instruction from the microcomputer 100. The G-light image sensor driver 110G drives the G-light image sensor 90G in accordance with an instruction from the microcomputer 100. The B-light image sensor driver 110B drives the B-light image sensor 90B in accordance with an instruction from the microcomputer 100.

The R-optical analog signal processing unit 120R reads the analog image signal output from the R-optical image sensor 90R, performs signal processing (for example, correlated double sampling processing, gain adjustment, and the like), converts the processed signal into a digital signal, and outputs the digital signal. Similarly, the G-light analog signal processing section 120G reads the analog image signal output from the G-light image sensor 90G, performs signal processing, and converts the processed signal into a digital signal and outputs the digital signal. The B-light analog signal processing unit 120B reads the analog image signal output from the B-light image sensor 90B, performs signal processing, converts the processed signal into a digital signal, and outputs the digital signal.

The microcomputer 100 reads the digital signals output from the R-optical analog signal processing unit 120R, G and the B-optical analog signal processing unit 120G and 120B, respectively, and performs signal processing thereon to generate an RGB image, which is a color image. Then, the microcomputer 100 outputs the generated RGB image as an RGB image signal.

The operation of the camera 2 configured as described above will be described. When starting shooting, the user can select a desired filter from the 1 st filter 63A, the 2 nd filter 63B, the 3 rd filter 63C, and the 4 th filter 63D by operating the rotation operation member 22 and rotating the turret filter 60.

The light emitted from the imaging lens 30 passes through the 1 st transparent plate 24, the turret filter 60, and the 2 nd transparent plate 45, and enters the entrance surface 71A of the dichroic prism 70. The light incident on the dichroic prism 70 is split into R light, G light, and B light. The decomposed R light, G light, and B light are separately received by the R light image sensor 90R, G light image sensor 90G and the B light image sensor 90B, respectively.

Each image sensor converts light into an image signal and outputs the image signal. Each analog signal processing unit performs signal processing on the image signal and outputs the image signal to the microcomputer 100. The microcomputer 100 generates and outputs an RGB image. The RGB image output from the microcomputer 100 is displayed on a display (not shown), for example.

As described above, according to the technique of the present invention, in the optical unit 20 having the camera side mount 21 with the short flange distance FB, a switching filter such as the turret filter 60 can be disposed between the camera side mount 21 and the dichroic prism 70. Therefore, according to the technique of the present invention, even in the small-sized camera 2 having a short flange distance FB, the user can easily select the optimum filter in accordance with the shooting situation or the like by performing the switching operation of the switching filter.

< modification example >

Various modifications of the above embodiment will be described below.

In the above embodiment, as shown in fig. 8, the adhesive layer 78G is formed on the entire surface of the cover glass 91 of the G-ray image sensor 90G, but as shown in fig. 12, the adhesive layer 78G may be formed locally on the surface of the cover glass 91. For example, the adhesive layer 78G may be formed on the outer peripheral portion of the cover glass 91. Thereby, an air layer 93B is formed between the cover glass 91 and the G optical compensation filter 75G. The G light having passed through the G light compensation filter 75G enters the sensor substrate 92 through the air layer 93B and the cover glass 91.

The R-light image sensor 90R and the B-light image sensor 90B can be similarly modified.

In the above embodiment, the compensation filter is provided on the emission surface of each prism of the dichroic prism, but a configuration in which no compensation filter is provided may be adopted. In this case, a cover glass of the image sensor may be bonded to the emission surface of each prism. Further, a configuration may be adopted in which a compensation filter is provided only on a specific emission surface.

In the above embodiment, the three-color dichroic prism decomposed into three colors is used as the dichroic prism, but a dichroic prism decomposed into two colors or four or more colors may be used. For example, a four-color dichroic prism that splits an incident light beam into R light, G light, B light, and IR light (infrared light) can also be used.

In the above embodiment, the dichroic prism having an air gap between the 1 st prism and the 2 nd prism is used, but a dichroic prism having no air gap (so-called gapless prism) may be used. In the gapless prism, light is reflected only once and extracted from the light-emitting surface in the prism other than the 1 st prism.

In the above-described embodiment, a rotating type switching filter, that is, a turret filter is used, but instead, a parallel-traveling type switching filter may be used. These switching filters are not limited to the manual switching operation, and may be an electric switching operation.

In the above-described embodiment, the imaging device is configured as a lens-interchangeable camera, but may be configured as an electronic endoscope (e.g., a hard endoscope). The imaging device may be configured as a monitoring camera, a microscope, or the like.

In the above-described embodiment, a bayonet satisfying the standard of the C-bayonet is used as the camera side bayonet for mounting the imaging lens, but the configuration of the bayonet is not limited thereto. For example, CS bayonet can be used. The flange pitch of the CS bayonet was 12.5mm (air converted length).

The technology of the present invention is a technology capable of disposing a switching filter between a bayonet and a dichroic prism in an optical unit including the bayonet and the dichroic prism, and is suitable for an imaging device which is required to be compact. The image pickup device required to be compact is an image pickup device using a C-bayonet, a CS-bayonet, or the like, in which the flange pitch is 20mm or less in air conversion length.

In order to arrange the switching filter between the bayonet and the dichroic prism, the actual length of the distance from the bayonet surface to the incident surface of the dichroic prism is preferably 8.2mm or more. By setting this distance to 8.2mm or more, the 1 st transparent plate can be disposed between the bayonet and the dichroic prism on the incident side of the switching filter, and the 2 nd transparent plate can be disposed on the exit side of the switching filter. The 1 st light-transmitting plate and the 2 nd light-transmitting plate are arranged in a shell for accommodating the switching filter and used for preventing dust of the switching filter. The 1 st transparent plate is disposed on a surface of the bayonet facing the switching filter.

Further, the actual length of the distance from the bayonet surface to the incident surface of the dichroic prism is preferably 10.6mm or less. That is, the actual length of the distance from the bayonet surface to the incident surface of the dichroic prism is preferably 8.2mm or more and 10.6mm or less. Further, the actual length of the distance from the bayonet surface to the incident surface of the dichroic prism is preferably 9.52mm or more and 9.82mm or less.

In an optical unit having a flange pitch of 20mm or less in air-equivalent length, it is preferable to reduce each part of the optical unit in order to dispose a switching filter between the bayonet and the dichroic prism. As a condition for miniaturizing each part of the optical unit, 1 st, the image sensor is preferably 1/2.8 type (diagonal 6.43mm) or less. This enables the use of a dichroic prism for downsizing.

The refractive index of the dichroic prism is preferably 1.7 or more. By increasing the refractive index, the air conversion length is shortened, and therefore the distance from the bayonet surface to the incident surface of the dichroic prism can be increased. This enlarges the space in which the switching filter can be arranged.

In fig. 3, the distance from the exit surface of the dichroic prism to the image sensor (in fig. 6, the thickness W7 of the adhesive layer 78G) is preferably 0.3mm or less. Further, in the 4 th image sensor, the optical path length (in fig. 6, the sum of W8 and G6) is preferably 1.0mm or less in terms of air-equivalent length. Under these conditions, the distance from the bayonet surface to the incident surface of the dichroic prism can be further increased. This further increases the space in which the switching filter can be arranged.

The above descriptions and drawings are only for describing the details of the portions related to the technology of the present disclosure, and are merely examples of the technology of the present disclosure. For example, the description relating to the above-described structure, function, operation, and effect is a description relating to an example of the structure, function, operation, and effect of a part relating to the technology of the present disclosure. Therefore, it is needless to say that unnecessary portions may be deleted, new elements may be added, or replacement may be made to the above-described description and illustration without departing from the scope of the technology of the present disclosure. In addition, in order to avoid the complexity and facilitate understanding of the portions related to the technology of the present disclosure, in the description and the drawings shown above, the description related to the technical common sense and the like which need not be described in particular is omitted in addition to the technology of the present disclosure which can be implemented.

All documents, patent applications, and technical standards cited in the present specification are incorporated by reference into the present specification to the same extent as if each document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.

Description of the symbols

2-camera, 10-camera body, 12-1 st opening, 13-2 nd opening, 20-optical unit, 21-camera side bayonet, 21A-internal thread portion, 21B-bayonet surface, 22-rotational operation member, 22A-gear, 23-bottom surface, 24-1 st translucent plate, 30-imaging lens, 31-lens barrel, 32-lens side bayonet, 32A-external thread portion, 40-base body, 41-screw hole, 42-internal bottom surface, 43-shaft support portion, 44-through hole, 45-2 nd translucent plate, 46-spacer, 47-support body, 48-support column, 50-cover member, 51, 52-through hole, 60-turntable filter, 61-shaft support portion shaft support hole, 62-tooth, 63A-1 st filter, 63B-2 nd filter, 63C-3 rd filter, 63D-4 th filter, 70-dichroic prism, 71-1 st prism, 71A-1 st face (incident face), 71B-2 nd face, 71C-3 rd face, 72-2 nd prism, 72A-1 st face, 72B-2 nd face, 72C-3 rd face, 73-3 rd prism, 73A-1 st face, 73B-2 nd face, 74R, 74G, 74B-adhesive layer, 75B 1-1B light compensation filter, 75B 2-2B light compensation filter, 75G-G light compensation filter, 75R-R light compensation filter, 76-spacer, 77-air gap, 78R, 78G, 78B-adhesive layer, 80-screw, 81-1 st air layer, 82-2 nd air layer, 83-3 rd air layer, 84-4 th air layer, 90B-B optical image sensor, 90G-G optical image sensor, 90R-R optical image sensor, 91-cover glass, 92-sensor substrate, 92A-light receiving surface, 93-spacer, 93A, 93B-air layer, 100-microcomputer, 110B-B optical image sensor driver, 110G-G optical image sensor driver, 110R-R optical image sensor driver, 120B-B optical analog signal processing section, 120G-G optical analog signal processing section, 120R-R optical analog signal processing section, D-FB-flange distance, L-distance, lz-optical axis.

Claims (10)

1. An optical unit, comprising:

a bayonet to which the imaging lens is detachably attached; and

a dichroic prism for color-decomposing an incident light flux incident through the imaging lens,

in the optical unit, a light source is provided,

the flange distance is less than 20mm in air conversion length,

the optical unit has a switchable filter that is disposed between the bayonet and the dichroic prism and is capable of switching filter characteristics.

2. The optical unit of claim 1,

the bayonet meets the standard of the C bayonet.

3. The optical unit of claim 1,

the distance from the bayonet surface of the bayonet to the incident surface of the dichroic prism is 8.2mm or more in actual length.

4. An optical unit according to claim 3, having:

a housing accommodating the switching type filter;

a 1 st transparent plate disposed on an incident side of the switching filter in the housing; and

and a 2 nd transparent plate disposed on the emission side of the switching filter in the housing.

5. The optical unit of claim 4,

the bayonet is arranged on the shell body,

the 1 st transparent plate is disposed on a surface of the bayonet, the surface being opposite to the switching filter.

6. The optical unit of claim 1,

an image sensor is disposed on each emission surface of the dichroic prism via an adhesive layer.

7. The optical unit of claim 6,

the adhesive layer is formed over the entire surface or in a part of each of the emission surfaces.

8. The optical unit of claim 7,

a compensation filter is arranged on each emergent surface,

the image sensor is disposed on the compensation filter through the adhesive layer.

9. The optical unit of claim 1,

the switching filter is a rotary switching filter.

10. An imaging device includes:

an optical unit as claimed in any one of claims 1 to 9;

a camera body accommodating the optical unit; and

and an imaging lens detachably attached to the mount.

Images