Image reading optical system and image reading device

An image reading optical system includes an image reading portion, multiple light reflection portions, and a diaphragm. The image reading portion includes an array of reading elements that read incident light. The light reflection portions reflect light traveling from a readable object to the image reading portion. The diaphragm regulates light traveling from a first one of the light reflection portions to a subsequent one of the light reflection portions in a specific direction. The diaphragm includes a first light shielding portion and a second light shielding portion disposed at different positions in a travel direction of the light with respect to the first one of the light reflection portions to block part of the light. The first light shielding portion and the second light shielding portion are located in substantially a common plane. The first light shielding portion is disposed along an optical axis of light incident on the first one of the light reflection portions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2018-179563 filed Sep. 25, 2018.

BACKGROUND

(i) Technical Field

The present disclosure relates to an image reading optical system and an image reading device.

(ii) Related Art

Japanese Patent No. 4497805 discloses an imaging optical system that forms, on a line sensor, an image of image information of an object surface, the imaging optical system including multiple reflection planes in an optical path from the object surface to the line sensor, all the reflection planes being formed of off-axial reflection planes.

Japanese Patent No. 4817773 discloses an imaging optical system including two off-axial optical devices.

Some optical systems that read images regulate light using, for example, a light shielding portion for light reduction.

In an optical system that reflects light with multiple light reflection portions and forms images with light on an image reading portion (sensor), if the light shielding portions serving as diaphragms are arranged in the plane orthogonal to the optical axis or if regulating members for regulating light are arranged in the direction orthogonal to the optical axis direction, the light shielding portions or the regulating members easily block light beams on other optical paths reflected by the light reflection portions. To avoid this, the other optical paths need to be spaced apart from the light shielding portions or regulating members. This arrangement, however, is more likely to enlarge bend angles of the optical paths.

The present disclosure aims to further narrow down a bend angle between a first optical path, along which light travels to be incident on a light reflection portion, and a second optical path, along which light emerges, compared to a case where multiple light shielding portions which regulate light and serve as optical diaphragms are arranged in an optical axis direction.

SUMMARY

Aspects of non-limiting embodiments of the present disclosure relate to an image reading optical system that includes an image reading portion, multiple light reflection portions, and a diaphragm. The image reading portion includes an array of reading elements that read incident light. The light reflection portions reflect light traveling from a readable object to the image reading portion. The diaphragm regulates light traveling from a first one of the light reflection portions to a subsequent one of the light reflection portions in a specific direction. The diaphragm includes a first light shielding portion and a second light shielding portion disposed at different positions in a travel direction of the light with respect to the first one of the light reflection portions to block part of the light. The first light shielding portion and the second light shielding portion are located in substantially a common plane. The first light shielding portion is disposed along an optical axis of light incident on the first one of the light reflection portions.

DETAILED DESCRIPTION

Exemplary embodiments of the present disclosure will now be described below with reference to the appended drawings.

FIG. 1illustrates an image reading device12according to an exemplary embodiment.

The image reading device12includes a document feeder50, and an image reading processor52, which reads images on documents.

The document feeder50includes a document tray60, which receives documents, a document transport path61, along which documents are transported, and a discharging portion62, to which documents from which images are read are discharged.

The document transport path61has a letter U shape.

On the document transport path61, multiple document transport rollers60R are arranged. Documents placed on the document tray60are transported along the document transport path61by the multiple document transport rollers60R. Documents transported along the document transport path61are finally discharged to the discharging portion62.

The image reading device12has a function of reading images of documents transported thereto from the document feeder50, and a function of reading images of documents placed on a platen glass70, described later.

The image reading processor52includes a housing75, and the platen glass70, at an upper portion of the housing75. In the present exemplary embodiment, documents are manually placed on the platen glass70one by one by an operator.

The housing75accommodates a reader unit76(carriage), which reads images on documents.

The reader unit76is movable along the platen glass70.

The reader unit76is disposed in a read position M to read images on documents transported by the document feeder50and passing over the reader unit76.

The reader unit76moves along the platen glass70to read images on documents placed on the platen glass70.

The reader unit76includes an illumination unit80, which is an example of a light source. The illumination unit80emits light to documents, which are readable objects.

The reader unit76also includes an image reading optical system86.

In the present exemplary embodiment, the image reading optical system86includes a mirror83, a mirror84, and a mirror85, which reflect reflected light L from the documents.

In the present exemplary embodiment, the image reading optical system86includes an imaging unit87, and a sensor88, which is an example of an image reading portion.

The imaging unit87is disposed downstream of the mirror85in the travel direction of the reflected light L.

The illumination unit80includes, for example, a white light emitting diode (LED).

The present exemplary embodiment includes a reflecting member82, which reflects light emitted from the illumination unit80toward the documents.

The imaging unit87shapes a beam (optical image) of the reflected light L from the document into the shape appropriately receivable by the sensor88. The imaging unit87may include an imaging lens (not illustrated) that optically reduces the size of the reflected light L from the document (an optical image of the document).

The sensor88photoelectrically converts the optical image that has passed through the imaging unit87, and creates signals (image signals) for red (R), green (G), and blue (B).

FIG. 2illustrates the sensor88, viewed in the direction of arrow II ofFIG. 1.

The sensor88is formed of, for example, a CCD image sensor.

As illustrated inFIG. 2, the sensor88includes three one-dimensional line sensors99, each extending in a main scanning direction (a first direction).

These three one-dimensional line sensors99are arranged side by side in a subscanning direction, or a second direction crossing (orthogonal to) the first direction.

More specifically, in the present exemplary embodiment, the three one-dimensional line sensors99are disposed for the respective colors R, G, and B.

Each one-dimensional line sensor99includes multiple reading elements (image sensors)95, arranged side by side in the main scanning direction (first direction). In other words, each one-dimensional line sensor99includes an array of the reading elements95that receive incident light.

Herein, the direction in which the reading elements95are arranged refers to the direction in which the reading elements95of each one-dimensional line sensor99for the corresponding color are arranged. In other words, the direction in which the reading elements95are arranged refers to the main scanning direction.

More specifically, in the present exemplary embodiment, three one-dimensional line sensors99are also arranged side by side in the subscanning direction, so that the three reading elements95are also arranged side by side in the subscanning direction. However, herein, the direction in which the reading elements95are arranged refers to the main scanning direction.

In other words, herein, the main scanning direction corresponding to the direction in which the reading elements95are arranged refers to the direction in which the reading elements95in each one-dimensional line sensor99for the corresponding color are arranged, and the subscanning direction refers to the direction crossing (orthogonal to) the direction in which the reading elements95are arranged.

In the present exemplary embodiment, to read a document on the platen glass70, a controller, not illustrated, moves the reader unit76in the direction of arrow C inFIG. 1.

Here, reflected light L from the document travels to the sensor88via the mirror83, the mirror84, the mirror85, and the imaging unit87, so that the sensor88reads the document.

Then, in the present exemplary embodiment, when the reader unit76reaches the position opposing the end of the document, the reader unit76finishes reading of one page of the document.

To read the document transported by the document feeder50, the reader unit76is positioned in the read position M.

In this state, the document feeder50starts transporting a document, and the document passes over the reader unit76. At this time, as in the above case, reflected light L from the document travels to the sensor88via the mirror83, the mirror84, the mirror85, and the imaging unit87, and then, the sensor88reads the document.

Here, a reading optical system including a combination of multiple reflection optical systems having power (intensity for bending light) in a predetermined direction may be used as an optical system that shapes the reflected light L from the document. The reading optical system including a combination of multiple reflection optical systems inevitably causes a reflected optical path.

The reading optical system includes a diaphragm for the purposes of, for example, adjusting the light amount, adjusting the modulated transfer function (MTF) or the transfer function of the optical system, or increasing the depth of focus.

This diaphragm condenses light in both a longitudinal direction of the sensor88(in the direction in which the reading elements95are arranged, or the main scanning direction) and in a lateral direction (in the direction orthogonal to the direction in which the reading elements95are arranged, or the subscanning direction).

FIG. 3illustrates the structure of the imaging unit87.

The imaging unit87includes a first imaging mirror90, and a second imaging mirror92. The first imaging mirror90and the second imaging mirror92reflect the reflected light L from the document, which is a readable object.

In other words, the imaging unit87includes multiple light reflection portions that reflect the reflected light L traveling to the sensor88, which is an example of an image reading portion. Each of the multiple light reflection portions reflects the reflected light L from the document.

In the present exemplary embodiment, the first imaging mirror90, which is an example of one of the light reflection portions, reflects the reflected light L, first, and then the second imaging mirror92, which is a subsequent one of the light reflection portions, reflects the reflected light L.

The first imaging mirror90and the second imaging mirror92are concave mirrors, and have a function of reflecting the reflected light L, and a function of condensing the reflected light L.

Thus, in the present exemplary embodiment, light beams from the first imaging mirror90and the second imaging mirror92have their width (width in both the main scanning direction and the subscanning direction) gradually tapering downstream in the light travel direction.

The present exemplary embodiment also includes a diaphragm member94between the first imaging mirror90and the second imaging mirror92.

The diaphragm member94blocks part of the reflected light L reflected by the first imaging mirror90, and regulates the reflected light L in the main scanning direction and the subscanning direction.

The diaphragm member94includes a first diaphragm100, which regulates the reflected light L in the main scanning direction (first direction). In other words, the diaphragm member94includes a first diaphragm100, which regulates the reflected light L in the direction the same as the direction in which the reading elements95are arranged.

The diaphragm member94also includes a second diaphragm200, which regulates the reflected light L in the subscanning direction (in the second direction crossing the first direction).

More specifically, the diaphragm member94includes a second diaphragm200, which regulates the reflected light L in the direction crossing (orthogonal to) the direction in which the reading elements95are arranged.

More specifically, the first diaphragm100includes a light receiving surface110, which receives part of the reflected light L traveling from the first imaging mirror90to the second imaging mirror92(hereinafter referred to as “inter-mirror light”). The light receiving surface110blocks part of the inter-mirror light to regulate the inter-mirror light in the main scanning direction.

The second diaphragm200, including a first light shielding portion210and a second light shielding portion220, blocks part of the inter-mirror light with the first light shielding portion210and the second light shielding portion220, and regulates the inter-mirror light in the subscanning direction.

The diaphragm member94includes a plate member94A, formed of a flat plate.

The plate member94A is disposed at an angle with respect to the inter-mirror light travel direction and to cross the inter-mirror light.

In the present exemplary embodiment, part of the plate member94A functions as the first light shielding portion210and the second light shielding portion220, and the plate member94A regulates the inter-mirror light.

The plate member94A has an opening94B, through which the inter-mirror light passes.

In the present exemplary embodiment, a portion of the plate member94A around the opening94B regulates the inter-mirror light.

More specifically, in the present exemplary embodiment, portions of the plate member94A around the opening94B serve as the first light shielding portion210and the second light shielding portion220.

The first light shielding portion210and the second light shielding portion220, located around the opening94B, block part of the inter-mirror light, so that the inter-mirror light is regulated in the subscanning direction, which is an example of a specific direction.

More specifically, in the present exemplary embodiment, a portion of the plate member94A located on the left side of the opening94B in the drawing serves as the first light shielding portion210, and a portion of the plate member94A located on the right side of the opening94B in the drawing serves as the second light shielding portion220.

In the present exemplary embodiment, the first light shielding portion210and the second light shielding portion220block part of the inter-mirror light to condense the inter-mirror light.

The first light shielding portion210and the second light shielding portion220are disposed at different positions in the inter-mirror light travel direction with respect to the first imaging mirror90.

More specifically, in the present exemplary embodiment, the first light shielding portion210and the second light shielding portion220are in different positions in the inter-mirror light travel direction.

In the present exemplary embodiment, the first light shielding portion210is located downstream of the second light shielding portion220in the inter-mirror light travel direction.

FIG. 4illustrates a comparative example of the imaging unit87.

In this comparative example, a plate member940A having a rectangular opening940B is disposed to extend in the direction orthogonal to the inter-mirror light travel direction. In other words, the plate member940A is disposed orthogonal to the optical axis of the inter-mirror light.

Furthermore, in this comparative example, the first light shielding portion210and the second light shielding portion220are disposed in a plane4A orthogonal to the optical axis of the inter-mirror light.

In this comparative example, the plate member940A is more likely to interfere with the incident light that is incident on the first imaging mirror90(hereinafter referred to as “first mirror incident light”) or the emerging light that emerges from the second imaging mirror92(hereinafter referred to as “second mirror emerging light”).

To avoid this interference, the optical path of the first mirror incident light or the optical path of the second mirror emerging light needs to be spaced apart from the plate member940A. This structure is more likely to enlarge the bend angles of the optical paths, and thus enlarge the reader unit76(refer toFIG. 1).

On the other hand, in the present exemplary embodiment (as illustrated inFIG. 3) in which the plate member94A is disposed at an angle with respect to the inter-mirror light travel direction, the plate member94A is less likely to interfere with the first mirror incident light or the second mirror emerging light.

More specifically, in the present exemplary embodiment, the first light shielding portion210and the second light shielding portion220are located at different positions in the inter-mirror light travel direction. Thus, the plate member94A is less likely to interfere with the first mirror incident light or the second mirror emerging light.

In the present exemplary embodiment, the first light shielding portion210and the second light shielding portion220are formed of a single unit.

More specifically, in the present exemplary embodiment, the first light shielding portion210and the second light shielding portion220are formed of portions of the plate member94A, or the first light shielding portion210and the second light shielding portion220are formed of a common member.

In the present exemplary embodiment, the first light shielding portion210is located closer to the optical path of the first mirror incident light than the second light shielding portion220.

More specifically, in the present exemplary embodiment, as illustrated inFIG. 3, the first light shielding portion210is located in, among two areas R1and R2opposing each other with an optical axis LG1of the inter-mirror light interposed therebetween, the area R1, closer to the first mirror incident light, and the second light shielding portion220is located in the area R2, further from the first mirror incident light.

More specifically, the first light shielding portion210is located closer to the optical path of the first mirror incident light than the second light shielding portion220in the direction orthogonal to the optical axis LG1of the inter-mirror light, which is the subscanning direction (in the direction of arrow2X).

In the present exemplary embodiment, the distance between the first light shielding portion210and the first imaging mirror90is greater than the distance between the second light shielding portion220and the first imaging mirror90.

In a structure, for example, where the distance between the first light shielding portion210and the first imaging mirror90is smaller than the distance between the second light shielding portion220and the first imaging mirror90and the first light shielding portion210is located upstream of the second light shielding portion220, the plate member94A (a portion of the plate member94A including the first light shielding portion210) is more likely to interfere with the first mirror incident light.

On the other hand, as in the present exemplary embodiment, in the structure where the distance between the first light shielding portion210and the first imaging mirror90is greater than the distance between the second light shielding portion220and the first imaging mirror90, the plate member94A (a portion of the plate member94A including the first light shielding portion210) is less likely to interfere with the first mirror incident light.

In the plate member94A, the distance from the first light shielding portion210to the end of the plate member94A closer to the first light shielding portion210may be shorter than the distance from the second light shielding portion220to the end of the plate member94A closer to the second light shielding portion220. In this structure, the plate member94A (a portion of the plate member94A including the first light shielding portion210) is less likely to interfere with the first mirror incident light.

In the present exemplary embodiment, the plate member94A is disposed along an optical axis LG2of the first mirror incident light. Thus, the plate member94A is less likely to interfere with the first mirror incident light than in the case where the plate member94A is not disposed along the optical axis LG2of the first mirror incident light.

Alternatively, the plate member94A may be disposed along an optical axis LG3of the second mirror emerging light.

The plate member94A may be disposed along both the optical axis LG2of the first mirror incident light and the optical axis LG3of the second mirror emerging light.

In this case, the optical axis LG3of the second mirror emerging light extends along the optical axis LG2of the first mirror incident light, and the plate member94A extends along these optical axes LG2and LG3.

FIG. 5illustrates the diaphragm member94, viewed in the direction of arrow V inFIG. 3.

As described above, the diaphragm member94has the rectangular plate member94A. The plate member94A has a rectangular opening94B.

In the present exemplary embodiment, the inter-mirror light passes through the opening94B in the plate member94A.

In the present exemplary embodiment, part of the plate member94A around the opening94B regulates the inter-mirror light in the subscanning direction, which is an example of a specific direction.

More specifically, in the present exemplary embodiment, a portion of the plate member94A located on the left of the opening94B in the drawing serves as the first light shielding portion210, and a portion of the plate member94A located on the right of the opening94B in the drawing serves as the second light shielding portion220.

In the present exemplary embodiment, the first light shielding portion210and the second light shielding portion220regulate the inter-mirror light in the subscanning direction, which is an example of a specific direction.

Here, regulating light in a specific direction refers to blocking passage of an end portion of a beam, that is, an end portion of light in the specific direction. In other words, regulating light in a specific direction refers to preventing a beam from expanding in the specific direction.

The present exemplary embodiment includes projections97, which project into the opening94B from an opening edge94D of the opening94B.

More specifically, in the present exemplary embodiment, as illustrated inFIG. 5, when the opening94B (plate member94A) is viewed from the front, the projections97project into the opening94B from the opening edge94D of the opening94B.

As described above, the present exemplary embodiment includes the first diaphragm100(refer toFIG. 3), which regulates the inter-mirror light in the main scanning direction. The first diaphragm100includes the projections97.

As illustrated inFIG. 3, the projections97project toward the optical path of the inter-mirror light from the side of the optical path. The projections97are formed of plate-shaped projecting pieces.

In the present exemplary embodiment, as illustrated inFIG. 5, the projections97include a first projection971and a second projection972. The first projection971and the second projection972are disposed at different positions in the main scanning direction.

The first projection971and the second projection972are disposed while having a gap therebetween.

The first projection971and the second projection972are integrated with each other with the plate member94A.

The first projection971and the second projection972block part of the inter-mirror light beam passing an end portion in the main scanning direction to regulate the inter-mirror light.

More specifically, the first projection971and the second projection972each include a light receiving surface110, which blocks part of the inter-mirror light to regulate the inter-mirror light.

In the present exemplary embodiment, as illustrated inFIG. 3, when an end pass plane97X that passes free end portions97A of the projections97is assumed, the first light shielding portion210and the second light shielding portion220are located closer to the base of the projections97(the junction between the projections97and the plate member94A) than the end pass plane97X.

More specifically, an end pass plane97X that passes the free end portions97A of the projections97and extends along the optical axis LG2of the incident light incident on the first mirror is assumed, and a first space SP1and a second space SP2, which are two opposing spaces with the end pass plane97X interposed therebetween, are assumed.

In this case, of these two spaces SP1and SP2, the first light shielding portion210and the second light shielding portion220are located in the second space SP2in which the bases of the projections97are located.

As illustrated inFIG. 6(illustrating another structure example), a structure in which a portion corresponding to the first light shielding portion210is connected to the end portions97A of the projections97is also conceivable. In other words, a plane6A in which the first light shielding portion210is located and a plane6B in which the second light shielding portion220is located may be different from each other.

In this structure, the first light shielding portion210is disposed closer to the first mirror incident light. Thus, compared to the structure according to the exemplary embodiment illustrated inFIG. 3, the reflected light L (first mirror incident light) and the diaphragm member94are more likely to interfere with each other.

In contrast, in the structure example according to the exemplary embodiment illustrated inFIG. 3, the first light shielding portion210and the second light shielding portion220are located in a common plane3Z, which is at an angle with respect to the optical axis LG1of the inter-mirror light. Here, the common plane3Z may also refer to substantially common planes, instead of only a completely common plane. The plane in which the second light shielding portion220is located may be parallel to and slightly spaced apart from the extension of the plane of the first light shielding portion210, or may not be completely parallel to the plane in which the first light shielding portion210is located and may cross the plane at a small angle.

In this case, the first light shielding portion210is apart from the first mirror incident light, so that the reflected light L (first mirror incident light) and the diaphragm member94are less likely to interfere with each other.

More specifically, in the structure example illustrated inFIG. 6, the light shielding portions (the first light shielding portion210and the second light shielding portion220) are connected to base portions and the end portions97A of the projections97.

In contrast, in the structure example illustrated inFIG. 3, the first light shielding portion210is not connected to the end portions97A of the projections97, and the first light shielding portion210is located closer to the second mirror emerging light.

In the structure example illustrated inFIG. 3, when a plane3H passing the light receiving surface110is assumed, the first light shielding portion210is located apart from the plane3H, instead of being located in the plane3H.

More specifically, the first light shielding portion210is located, in the inter-mirror light travel direction, downstream of the plane3H and apart from the plane3H.

In the structure example illustrated inFIG. 3, the common plane3Z, in which the first light shielding portion210and the second light shielding portion220are located, crosses the plane3H that passes the light receiving surface110of the first diaphragm100.

FIG. 7Aillustrates the imaging unit87, when viewed in the direction of arrow VIIA ofFIG. 3, andFIG. 7Billustrates the imaging unit87, when viewed in the direction of arrow VIIB ofFIG. 3.

In the present exemplary embodiment, as illustrated inFIG. 7A, inter-mirror light occurs when the first mirror incident light is reflected by the first imaging mirror90.

In the present exemplary embodiment, the first projection971and the second projection972in the diaphragm member94regulate the inter-mirror light in the main scanning direction.

In the present exemplary embodiment, as illustrated inFIG. 7B, the first light shielding portion210and the second light shielding portion220of the diaphragm member94regulate the inter-mirror light in the subscanning direction.

The present exemplary embodiment includes two projections97, that is, the first projection971and the second projection972. However, this is not the only possible structure. For example, only one of the projections97may be disposed in accordance with, for example, the state of light (beam) that is to be regulated.

Similarly, only one of the first light shielding portion210and the second light shielding portion220may be disposed in accordance with, for example, the state of light (beam) that is to be regulated.

In the present exemplary embodiment, a structure in which the opening94B in the plate member94A is rectangular is described by way of example. However, this is not the only possible structure. The opening94B may have another shape such as circular, elliptic, or triangular in accordance with, for example, a cross-sectional shape of a beam of the reflected light L.

FIG. 8A(illustrating another structure example of the diaphragm member94) illustrates a trapezoidal opening94B in the plate member94A, by way of example.

In this structure example, of a first side181to a fourth side184located at the opening edge94D, the first side181, corresponding to the lower base, is longer than a third side183, corresponding to the upper base.

In the present exemplary embodiment, as illustrated inFIG. 8B, the width of the inter-mirror light beam gradually increases at a position downstream of the first diaphragm100.

Here, when the first side181corresponding to the lower base is longer than the third side183corresponding to the upper base, the inter-mirror light and the plate member94A are less likely to interfere with each other than in the case where the first side181is not longer than the third side183.

In the present exemplary embodiment, the case where the first light shielding portion210and the second light shielding portion220are formed of the common plate member94A is described. However, this is not the only possible structure. As illustrated inFIGS. 10A and 10B(illustrating another structure example of the diaphragm member94), the first light shielding portion210and the second light shielding portion220may be formed of plate members991and992, which are separate (separate members).

As in the above case, the first light shielding portion210and the second light shielding portion220(plate members991and992) are located on the common plane3Z.

Thus far, a structure in which the first imaging mirror90and the second imaging mirror92(concave mirrors) that have power in a predetermined direction (or in both the main scanning direction and the subscanning direction) are used as reflecting mirrors is described by way of example. However, this is not the only possible structure. For example, plane mirrors may be used, instead.

When imaging mirrors having power in a predetermined direction are used as the first imaging mirror90and the second imaging mirror92, the imaging mirrors may have power in only either the main scanning direction or the subscanning direction. Alternatively, the imaging mirrors may have power in both the main scanning direction and the subscanning direction.

Both of or either one of the first imaging mirror90and the second imaging mirror92may have power.

In the exemplary embodiments, a structure example including two imaging mirrors (the first imaging mirror90and the second imaging mirror92) is described. However, this is not the only possible structure. The structure may include three or more imaging mirrors.

The imaging mirrors may be formed from resin such as plastics and formed by depositing metal on a curved surface. Instead of resin, the imaging mirrors may be formed from glass or metal.

Mirrors having positive power (condensing optical systems) need to be disposed in front of and at the back of the diaphragm. Between the mirrors, negative power (magnifying optical system) may be disposed.

It will suffice that at least an optical system or a group of optical systems that has positive power in total is disposed in front of the diaphragm (on the upstream side of the optical path), and an optical system or a group of optical systems that has positive power in total is disposed at the back of the diaphragm (on the downstream side of the optical path).

The reader unit76may have a structure illustrated inFIG. 9(illustrating another structure example of the reader unit76).

In the structure example illustrated inFIG. 1, the reflected light L travels to the sensor88from the left side of the sensor88inFIG. 1. However, in the structure illustrated inFIG. 9, after the reflected light L is reflected by multiple mirrors, the reflected light L travels to the sensor88from the right side of the sensor88inFIG. 1.

Although not illustrated in detail, the structure example illustrated inFIG. 9also includes the diaphragm member94that regulates the inter-mirror light, as in the above case.