JP6966974B2 - Imaging device - Google Patents

Description

The present invention relates to an image pickup apparatus that images an inner peripheral surface of a hole formed in a hole formation direction from the surface of an image pickup object.

As one of the three-dimensional workpieces such as metal parts, resin parts and rubber parts, there are those in which holes (including recesses and through holes) are provided from the surface of the workpiece. For example, when a cylindrical hole is formed on the surface of a disk-shaped metal plate by cutting, it is necessary to inspect whether or not the inner peripheral surface of the hole is formed in a desired peripheral surface state. Therefore, for example, an inspection technique has been proposed in which the inner peripheral surface of a hole is imaged by using the image pickup apparatus described in Patent Document 1, and the work is inspected based on the image obtained by the image pickup apparatus.

Japanese Unexamined Patent Publication No. 2012-49624

In the image pickup apparatus described in Patent Document 1, a lens barrel that can be inserted and removed is extended in the vertical direction in the hole of the work. An objective mirror is placed on the lower end side of the lens barrel at an angle of 45 ° with respect to the axis of the lens barrel, and the illumination light going from above to below along the axis of the lens barrel is folded back horizontally. Irradiate the inner peripheral surface of the hole. Further, the reflected light reflected on the inner peripheral surface of the hole is folded upward by the objective mirror and received by the camera unit via the dimming unit. As a result, a partial image of the inner peripheral surface of the hole is captured by the camera unit.

In this imaging device, the lens barrel and the objective mirror are rotated around the axis in order to image the inner peripheral surface of the hole over the entire circumference. Further, since the reflected light emitted from the lens barrel rotates around the axis along with the rotation, the dimming unit is rotated around the axis. By adopting such a configuration, the light incident on the camera unit is prevented from rotating around the axis, and the orientation of the image captured by the camera unit is maintained constant. In this way, it is possible to satisfactorily capture an all-around image of the inner peripheral surface of the hole at the insertion height position of the lens barrel and the objective mirror.

However, in order to capture an all-around image of the inner peripheral surface of a hole that is sufficiently deeper than the size of the objective mirror in the vertical direction, each insertion is performed while switching the insertion height position of the lens barrel and the objective mirror in multiple stages. It is necessary to repeatedly capture the all-around image by the camera unit while rotating the lens barrel and the objective mirror at the height position and rotating the dimming unit in synchronization with the rotation. Therefore, it may take a long time to image the inner peripheral surface of the hole.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an imaging device capable of satisfactorily imaging the inner peripheral surface of a hole in a short time.

The image pickup apparatus according to the present invention is an image pickup device that captures an image of the inner peripheral surface of a hole formed in the hole formation direction from the surface of an image pickup object by an imaging unit, and emits illumination light for illuminating the inner peripheral surface. The light source and the plurality of folding mirrors are provided, and the plurality of folding mirrors guide the illumination light to different regions of the inner peripheral surface in the hole forming direction and extract the reflected light reflected in the regions from the holes. The head part that rotates around the rotation axis parallel to the hole formation direction while being inserted into the hole, and the head while rotating around the rotation axis so that the rotation angle per unit time is half the rotation angle of the head part. An image rotation correction unit that guides a plurality of reflected light extracted from the unit toward the image pickup unit to maintain a constant orientation of the image captured by the image pickup unit, and each reflected light emitted from the image rotation correction unit. In addition, it is provided with an optical path length difference correction unit that guides the light path to the image pickup unit while adjusting the optical path length of the reflected light from the image rotation correction unit to the image pickup unit according to the optical path length difference of a plurality of reflected lights in the head unit. It is a feature.

In the invention configured in this way, a plurality of folded mirrors are provided in the head portion inserted into the hole, and the illumination light is guided to different regions of the inner peripheral surface in the hole forming direction and reflected in the region. The reflected light is taken out from the hole. Then, each reflected light is guided to the image pickup unit. Therefore, it is possible to image the inner peripheral surface of the hole for a plurality of regions different from each other in the hole forming direction at one time.

Further, by providing a plurality of folded mirrors in the head portion as described above, an optical path length difference occurs between a plurality of reflected lights in the head portion, but the optical path length difference before the reflected light is incident on the imaging unit. The correction unit adjusts the optical path length of the reflected light from the image rotation correction unit to the image pickup unit for each reflected light emitted from the image rotation correction unit. Therefore, the optical path lengths from the inner peripheral surface to the image pickup unit are the same for all the reflected lights, and it is possible to image the inner peripheral surface of the hole satisfactorily for each region.

As described above, since a plurality of folding mirrors are provided in the head portion and the optical path length difference of the reflected light generated in the head portion is adjusted by the optical path length difference correction portion, the inner peripheral surface of the hole is adjusted. Good imaging can be performed in a short time.

It is a figure which shows one Embodiment of the image pickup apparatus which concerns on this invention. It is a figure which shows typically the head part, the image rotation correction part, and the optical path length difference correction part which are the main configurations of the image pickup apparatus shown in FIG. 1. It is a figure which shows typically the optical path that the light reflected by the inner peripheral surface of a through hole is guided to the image pickup part. It is a figure which shows the main structure of the image pickup part. FIG. 3 is a plan view of the optical path length difference correction unit, the image rotation correction unit, and the head unit shown in FIG. 3 as viewed from the Z direction. FIG. 3 is a side view of the optical path length difference correction unit, the image rotation correction unit, and the head unit shown in FIG. 3 as viewed from the Y direction. FIG. 3 is a side view of the optical path length difference correction unit, the image rotation correction unit, and the head unit shown in FIG. 3 as viewed from the X direction.

FIG. 1 is a diagram showing an embodiment of an image pickup apparatus according to the present invention. FIG. 2 is a diagram schematically showing a head unit, an image rotation correction unit, and an optical path length difference correction unit, which are the main configurations of the image pickup apparatus shown in FIG. 1. FIG. 3 is a diagram schematically showing an optical path in which light reflected on the inner peripheral surface of the through hole, that is, the reflected light is guided to the image pickup unit. The image pickup apparatus 100 uses a work 1 having a through hole 13 formed in a through hole 13 from a front surface 11 to a back surface 12 in the central portion of a disk-shaped metal plate as an image pickup target, and holds the back surface 12 of the work 1 on a work holding table 2. This is a device that captures an image of the inner peripheral surface 14 of the through hole 13 of the work 1 in this state. In each of the following figures, the hole forming direction in which the through hole 13 is formed is defined as the “Z direction”.

In the image pickup apparatus 100, the head portion 3 is provided so as to be freely insertable / detachable from the (+ Z) direction with respect to the through hole 13 of the work 1 held in the work holding table 2. Then, when the work 1 is imaged, the head portion 3 is inserted into the through hole 13 of the work 1 as shown in FIGS. 1 and 3. Further, an image rotation correction unit 4, an optical path length difference correction unit 5, and an image pickup unit 6 are provided in this order above the head unit 3, that is, in the (+ Z) direction, and a light source 7 is provided on the side surface of the image pickup unit 6. It is attached.

The light source 7 emits illumination light for illuminating the inner peripheral surface 14 of the through hole 13. Then, as shown in FIG. 1, the illumination light IL emitted from the light source 7 is irradiated toward the half mirror 61 provided in the image pickup unit 6. The illumination light IL is folded back in the (-Z) direction by the half mirror 61, and is further incident on the head unit 3 via the optical path length difference correction unit 5 and the image rotation correction unit 4. In the head portion 3, the illumination light IL is folded back in the (−X) direction and is applied to the inner peripheral surface 14 of the through hole 13.

On the other hand, the reflected light reflected by the inner peripheral surface 14 of the through hole 13 travels in the (+ X) direction, is folded back in the (+ Z) direction by the head portion 3, and is taken out from the through hole 13 of the work 1. Then, the reflected light is incident on the image pickup unit 6 via the image rotation correction unit 4 and the optical path length difference correction unit 5, passes through the half mirror 61, and is received by the image pickup element 62. As a result, the image pickup unit 6 takes an image of the region of the inner peripheral surface 14 of the through hole 13 that has been irradiated with the illumination light IL.

In the present embodiment, as shown in FIG. 2, the head portion 3 has two folded mirrors 31 and 32. The folded mirrors 31 and 32 are arranged so as to be offset from each other in the Z direction. More specifically, the folded mirror 32 is arranged so as to be displaced in the (−Z) direction from the folded mirror 31, and is located on the tip end side in the Z direction. That is, the folded mirror 32 corresponds to an example of the "tip folded mirror" of the present invention. Further, the folding mirror 32 is also displaced in the (−Y) direction from the folding mirror 31 in the Y direction orthogonal to the X direction and the Z direction. Therefore, as shown in FIG. 3, two regions R1 and R2 of the inner peripheral surface 14 that are different from each other in the Z direction are irradiated with illumination light IL (FIG. 1) via the folded mirrors 31 and 32, respectively. The reflected light RL1 and RL2 reflected in the regions R1 and R2 are taken out from the through hole 13 via the folded mirrors 31 and 32, respectively. Of these reflected lights, the reflected light RL2 corresponds to an example of the "advanced reflected light" of the present invention.

Further, the reference numeral A1 in FIG. 3 indicates the reflection position of the illumination light IL in the region R1, and the reference numeral A2 indicates the reflection position of the illumination light IL in the region R2. Further, reference numeral B1 in FIG. 3 is a folding position where the reflected light RL1 is folded back on the mirror surface 311 of the folding mirror 31, and reference numeral B2 is a folding position where the reflected light RL2 is folded back on the mirror surface 321 of the folding mirror 32. .. In the present embodiment, the folded mirrors 31 and 32 are provided so that the surface normal of the mirror surface 311 is slightly inclined with respect to the surface normal of the mirror surface 312, and the reflected light RL2 is emitted in the Z direction. On the other hand, the reflected light RL1 gradually moves away from the reflected light RL2 in the Y direction (see FIG. 7), and the reason will be described in detail later.

Further, in the head portion 3 having the two folded mirrors 31 and 32 as described above, the folded mirrors 31 and 32 are integrally rotatable with the central axis 13a of the through hole 13 extending in parallel with the Z direction as a rotation axis. .. Further, the head portion 3 is mechanically connected to the head rotation drive portion 33 as shown in FIGS. 1 and 2. Therefore, when the head rotation drive unit 33 operates in response to a rotation command from the control unit 9 that controls the entire device, the head unit 3 rotates around the central axis 13a. As a result, the regions R1 and R2 move in the circumferential direction of the inner peripheral surface 14 and rotate the head portion 3 once, so that the reflected light RL1 and RL2 are taken out over the entire circumference of the inner peripheral surface 14 of the through hole 13.

When the head portion 3 is rotated in this way, the reflected lights RL1 and RL2 also rotate according to the rotation. Therefore, the image pickup apparatus 100 according to the present embodiment is also provided with an image rotation correction unit 4 having the same configuration as the dimming unit of Patent Document 1. The image rotation correction unit 4 is composed of three correction mirrors 41 to 43, and the correction mirrors 41 to 43 are integrally rotatable with the central axis 13a of the through hole 13 as the rotation axis. Further, the image rotation correction unit 4 is mechanically connected to the image rotation drive unit 44 as shown in FIGS. 1 and 2. Then, when the image rotation drive unit 44 operates in response to the rotation command from the control unit 9, the image rotation correction unit 4 rotates around the central axis 13a. However, the rotation speed is controlled so that the rotation speed, that is, the rotation angle θ per unit time is half the rotation angle (θ / 2) of the head unit 3. As a result, the reflected lights RL1 and RL2 do not rotate, but are guided to the image pickup unit 6 as they are via the optical path length difference correction unit 5, and the orientation of the image imaged by the image pickup unit 6 is maintained constant. Since the configuration and operation of the image rotation correction unit 4 are described in detail in Patent Document 1, the description of the configuration and operation of the image rotation correction unit 4 in the present specification will be omitted.

Here, comparing the optical path lengths of the reflected lights RL1 and RL2 emitted from the image rotation correction unit 4, the folding mirror 32 is farther from the image rotation correction unit 4 than the folding mirror 31 in the head unit 3, that is, to the tip side. Because of the arrangement, the optical path length of the reflected light RL2 is longer than the optical path length of the reflected light RL1. Therefore, if the reflected light RL1 and RL2 emitted from the image rotation correction unit 4 are directly incident on the image pickup unit 6, the focus shift occurs between the regions R1 and R2, and the images are collectively and well imaged. It is difficult to do. Therefore, in the present embodiment, an optical path length difference correction unit 5 that combines two optical path change mirrors 51 and 52 is interposed between the image rotation correction unit 4 and the image pickup unit 6.

As shown in FIGS. 2 and 3, the optical path length difference correction unit 5 includes an optical path change mirror 51 which is arranged away from the optical path of the reflected light RL2 in the Y direction and reflects only the reflected light RL1 and an optical path change mirror 51. It is provided with an optical path changing mirror 52 that folds back the reflected reflected light RL1 toward the image pickup unit 6. Therefore, in the optical path length difference correction unit 5, as shown in FIG. 3, the reflected light RL1 is folded back at the reflection position C1 of the optical path change mirror 51 and the reflection position D1 of the optical path change mirror 52. The optical path length becomes longer than the optical path length of the reflected light RL2. That is, in the present embodiment, the optical path length of the reflected light from the image rotation correction unit 4 to the image pickup unit 6 is set to the reflected light RL1 and RL2 in the head unit 3 for each of the reflected light RL1 and RL2 emitted from the image rotation correction unit 4. It is adjusted according to the difference in the optical path length of. As a result, the optical path length of the reflected light RL1 from the reflected position A1 to the incident position E1 (FIG. 3) to the image pickup unit 6 and the reflected light RL2 from the reflection position A2 to the incident position E2 (FIG. 3) from the reflection position A2 to the image pickup unit 6. It is possible to almost match the optical path length of. The analysis will be described later with reference to FIGS. 5 to 7.

FIG. 4 is a diagram showing a main configuration of an imaging unit. In addition to the half mirror 61 and the image sensor 62 described above, the image pickup unit 6 has an optical system 63 composed of two lenses 631 and 632 and an aperture 633, which constitutes a so-called object-side telecentric lens and reflects light. The optical RL1 and RL2 are focused on the image pickup surface 621 of the image pickup element 62, respectively, and an image of each region R1 and R2 is formed on the image pickup surface 621. Further, although not shown in FIG. 4, in the image pickup apparatus 100, as described above, the illumination light IL from the light source 7 is captured by the image pickup unit 6, the optical path length difference correction unit 5, the image rotation correction unit 4, and the head unit 3. It is a so-called coaxial epi-illumination system that irradiates the inner peripheral surface 14 of the through hole 13 through the above. Therefore, the following effects can be obtained.

As described above, the work 1 is made of metal, the through hole 13 is formed by cutting or the like, and the inner peripheral surface 14 thereof is often required to have relatively high accuracy. Therefore, the inner peripheral surface 14 is in a state close to a mirror surface. If a defective portion such as a scratch or a chip is present on the inner peripheral surface 14, scattered light is generated in the defective portion. On the contrary, the mirror surface state is maintained in the portion other than the defective portion, and the scattered light component from the mirror surface portion is small. Therefore, by combining the feature of being telecentric on the object side and the feature of adopting coaxial epi-illumination as in the present embodiment, the reflected light RL1 and RL2 become specular reflected light, and if there is a defect portion. Clearly includes a defective portion in the image captured by the imaging unit 6. As a result, it is possible to easily inspect whether or not a defective portion is present.

As described above, according to the present embodiment, the head portion 3 in which the folded mirrors 31 and 32 are arranged at different positions in the Z direction is inserted into the through hole 13 of the work 1. Then, the illumination light IL is guided to the regions R1 and R2 of the inner peripheral surface 14 which are different from each other in the Z direction in the inserted state, and the reflected lights RL1 and RL2 reflected in the regions R1 and R2 are taken out from the through hole 13. The light is received by the image pickup element 62 of the image pickup unit 6. Therefore, it is possible to simultaneously image the two regions R1 and R2 included in the inner peripheral surface 14 of the through hole 13, and the inner peripheral surface 14 of the through hole 13 can be imaged in a short time.

Further, by providing the two folding mirrors 31 and 32 in the head portion 3, an optical path length difference occurs between the reflected light RL1 and RL2 in the head portion 3, but by providing the optical path length difference correction unit 5, it is shown in FIG. As described above, for both the reflected light RL1 and RL2, the optical path length from the inner peripheral surface 14 to the incident on the lens 631 on the object side in the image pickup unit 6 has several dimensions and values from the device specifications as described in detail below. Can be set equally, and the inner peripheral surface 14 of the through hole 13 can be well imaged by focusing on each of the regions R1 and R2.

Next, the optical path length from the inner peripheral surface 14 to the incident on the lens 631 on the object side in the imaging unit 6 will be described in detail with reference to FIGS. 3, 5 to 7. FIG. 5 is a plan view of the optical path length difference correction unit 5, the image rotation correction unit 4, and the head unit 3 shown in FIG. 3 as viewed from the Z direction, that is, an XY plan view. Further, FIG. 6 is a side view, that is, an XZ plan view of the optical path length difference correction unit 5, the image rotation correction unit 4, and the head unit 3 shown in FIG. 3 as viewed from the Y direction. Further, FIG. 7 is a side view, that is, a YZ plan view of the optical path length difference correction unit 5, the image rotation correction unit 4, and the head unit 3 shown in FIG. 3 as viewed from the X direction. Note that the image rotation correction unit 4 is not shown in FIGS. 5 and 7. Further, the reference numerals dx, dy1, dy2, dz, L1, L2, L3, and rw in FIGS. 5 to 7 are as follows.

dx: Distance between mirrors of optical path changing mirrors 51 and 52 in the X direction,
dy1: Distance between the folded mirrors 31 and 32 in the Y direction,
dy2: Distance between the mirrors of the folding mirror 31 and the optical path changing mirror 51 in the Y direction,
dz: Distance between the folded mirrors 31 and 32 in the Z direction,
L1: Distance between the mirrors of the folding mirror 31 and the optical path changing mirror 51 in the Z direction (however, including the folding of the reflected light by the correction mirrors 41 to 43).
L2: Distance between mirrors of optical path changing mirrors 51 and 52 in the Z direction,
L3: Distance between the optical path changing mirror 52 and the incident surface of the lens 631 in the Z direction,
rw: radius of inner peripheral surface 14,
α1: Reflection angle of the folded mirror 31 in the YZ plane,
α2x: Reflection angle of the optical path change mirror 51 in the XZ plane,
α2y: Reflection angle of the optical path change mirror 51 in the YZ plane.

Here, first, the optical path length of the reflected light RL1 will be examined. As shown in FIG. 6, the reflected light RL1 is incident on the image pickup unit 6 in an optical path of position A1-position B1- (image rotation correction unit 4) -position C1-position D1-position E1. Therefore, the distance between the positions adjacent to each other is as shown by the following equation.

On the other hand, as shown in FIG. 6, the reflected light RL2 is incident on the image pickup unit 6 through an optical path of position A2-position B2- (image rotation correction unit 4) -position C2-position D2-position E2. Therefore, the distance between the positions adjacent to each other is as shown by the following equation.

Then, in order to make the optical path lengths of the reflected lights RL1 and RL2 equal, it is necessary to satisfy the following equation.

By substituting the above equations 1 and 2 into this and rearranging the distance L2 between the mirrors of the optical path changing mirrors 51 and 52 in the Z direction, the following equation is obtained.

On the other hand, the reflection angle α1 of the folding mirror 31 in the YZ plane, the reflection angle α2x of the optical path changing mirror 51 in the XZ plane, and the reflection angle α2y of the optical path changing mirror 51 in the YZ plane are shown in FIGS. 6 and 7. As is clear, it is expressed by the following equation.

Therefore, when the distances dx, dy1, dy2, dz, L1, and L3 are determined from the specifications of each part of the image pickup apparatus 100, the optical path change mirrors 51 and 52 in the Z direction are provided with the condition that the optical path lengths of the reflected light RL1 and RL2 are equal. The distance L2 between the mirrors can be obtained. Moreover, the reflection angles α1, α2x, and α2y are uniquely determined from the above-mentioned expression of the reflection angle. In this way, the specific configuration of each of the optical path length difference correction unit 5, the image rotation correction unit 4, and the head unit 3 can be determined, and in the image pickup apparatus 100 assembled according to this, the two reflected light RL1s can be determined. By receiving light on the RL2 by the imaging unit 6, not only the inner peripheral surface 14 can be imaged in a short time, but also the inner peripheral surface 14 of the through hole 13 can be imaged satisfactorily.

Further, as described above, the folded mirrors 31 and 32 are arranged so that the surface normal of the mirror surface 311 is slightly inclined with respect to the surface normal of the mirror surface 312 to provide a reflection angle α1. As a result, the reflected light RL1 and RL2 incident on the optical path length difference correction unit 5 are separated in the Y direction, and the reflected light RL2 passes by the side of the optical path change mirror 51 and is guided to the image pickup unit 6. The reflected light RL1 is turned back by the optical path change mirrors 51 and 52, and then guided to the image pickup unit 6. As a result, although the reflected light RL1 and RL2 have a spread according to the numerical aperture on the object side, the reflected light RL1 and RL2 can be separated and guided along a desired optical path as described above.

The present invention is not limited to the above-described embodiment, and various modifications can be made other than those described above as long as the present invention is not deviated from the gist thereof. For example, in the above embodiment, the head portion 3 is provided with two folding mirrors 31 and 32, and two regions R1 and R2 different from each other in the Z direction are simultaneously imaged, but the number of folding mirrors is 3 or more. May be good. In short, the plurality of folded mirrors may be configured to guide the illumination light IL to a region different from each other in the Z direction of the inner peripheral surface 14, and to take out the reflected light reflected in the region from the through hole 13. .. In this case, as the number of folded mirrors increases, the number of optical path changing mirrors provided in the optical path length difference correction unit 5 may also increase.

Further, in the above embodiment, the work 1 in which the through hole 13 is formed is regarded as the “object to be imaged” of the present invention, but it is also possible to image a work in which a recess shallower than the thickness of the metal plate is formed from the surface 11. It is possible. That is, the "hole" of the present invention includes both through holes and recesses. Further, the material of the work is not limited to the metal material, but may be a ceramic material, a resin material or a rubber material, and various works can be imaged as an image pickup object.

INDUSTRIAL APPLICABILITY The present invention can be applied to a general image pickup apparatus that images the inner peripheral surface of a hole formed in the hole formation direction from the surface of an image pickup object.

1 ... Work (object to be imaged)
3 ... Head unit 4 ... Image rotation correction unit 5 ... Optical path length difference correction unit 6 ... Imaging unit 7 ... Light source 11 ... Surface 13 ... Through hole 14 ... Inner peripheral surface (of through hole) 31 ... Folded mirror 32 ... (tip) folded mirror 51, 52 ... optical path change mirror 63 ... optical system 100 ... image pickup device IL ... illumination light R1, R2 ... region RL1 ... reflected light RL2 ... (tip) reflected light Z ... hole formation direction θ ... rotation angle

Claims (5)

An image pickup device that uses an image pickup unit to image the inner peripheral surface of a hole formed in the hole formation direction from the surface of the object to be imaged.
A light source that emits illumination light for illuminating the inner peripheral surface,
The plurality of folding mirrors have a plurality of folding mirrors, and the plurality of folding mirrors guide the illumination light to a region different from each other in the hole forming direction of the inner peripheral surface, and the reflected light reflected in the region is transmitted from the hole. A head portion that rotates around a rotation axis parallel to the hole forming direction while being inserted into the hole so as to be taken out.
While rotating around the rotation axis so that the rotation angle per unit time is half the rotation angle of the head portion, the plurality of reflected lights taken out from the head portion are guided toward the image pickup unit. An image rotation correction unit that keeps the orientation of the image captured by the image pickup unit constant, and an image rotation correction unit.
For each reflected light emitted from the image rotation correction unit, the optical path length of the reflected light from the image rotation correction unit to the image pickup unit is adjusted according to the optical path length difference of the plurality of reflected light in the head unit. However, the image pickup apparatus is provided with an optical path length difference correction section that guides the image pickup section. The imaging device according to claim 1.
The image pickup unit includes an image pickup element and an optical system in which the plurality of reflected lights emitted from the optical path length difference correction section are incident on the image pickup element to form an image of the inner peripheral surface on the image pickup element. death,
An image pickup device in which the illumination light emitted from the light source is applied to the inner peripheral surface via the optical system, the optical path length difference correction unit, the image rotation correction unit, and the head unit. The image pickup apparatus according to claim 1 or 2.
The plurality of folded mirrors are image pickup devices arranged at different positions in a plane orthogonal to the hole forming direction. The image pickup apparatus according to claim 3.
When the folding mirror farthest from the image rotation correction unit among the plurality of folding mirrors is used as the tip folding mirror, and the reflected light taken out by the tip folding mirror is used as the tip reflected light.
The optical path length difference correction unit has an optical path change mirror arranged outside the optical path of the tip reflected light, and among the plurality of reflected lights emitted from the image rotation correction unit, other than the tip reflected light. An image pickup device that reflects the reflected light by the optical path change mirror to change the optical path and guides the light path to the image pickup unit, while guiding the tip reflected light to the image pickup unit as it is to adjust the optical path length. The imaging device according to claim 4.
Among the plurality of folding mirrors, the folding mirrors other than the tip folding mirror have a surface normal inclined with respect to the surface normal of the tip folding mirror, and an image pickup device that guides the reflected light to the optical path changing mirror. ..

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