JP2010249881A - Imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging device including an optical element that is not affected by the optical characteristic or internal constitution. <P>SOLUTION: The imaging device (10) includes an imaging element (22) for photoelectrically converting incident subject light, an optical low-pass filter (23) arranged on the subject side of the imaging element, an optical element (24) arranged on the subject side of the optical low-pass filter, and a vibration generating means (27) for vibrating the optical element by application of voltage. The optical element (24) is a wavelength plate formed of single crystal quartz. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging apparatus.

  2. Description of the Related Art Conventionally, in an imaging apparatus such as a digital camera, an optical low-pass filter (hereinafter, referred to as a foreign object) in which dust that intrudes during lens replacement or wear powder (hereinafter referred to as foreign matter) generated from driving components in the camera is disposed in front of the image sensor. In the following, there is a problem that it adheres to the surface of the OLPF and appears in the image taken by the image sensor.

  Therefore, a technique is known in which foreign matters appearing on the image sensor are removed by vibrating a dust-proof optical element disposed further forward of the OLPF (see, for example, Patent Document 1).

JP 2006-293097 A

  There is a model using glass as the optical element. In general, since glass has low strength, it is necessary to increase the plate thickness in order to vibrate as an optical element. However, when the thickness of the glass is increased, it is difficult to transmit vibrations, and thus it is difficult to remove foreign matter. In addition, the coating film formed on the glass surface makes it easy to see the dirt on the surface that cannot be seen with the naked eye, and affects the optical characteristics.

  In addition, there is a model using a quartz birefringent plate as the optical element. The quartz birefringent plate has higher strength than glass, but is restricted by the optical design because it is necessary to consider the direction of the optical axis when it is arranged on the front side of the OLPF. In addition, since the crystal refracting plate linearly polarizes all incident light, it is restricted by the configuration of the OLPF disposed behind.

  The subject of this invention is providing the imaging device provided with the optical element which is not influenced by an optical characteristic or an internal structure.

The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.
According to the first aspect of the present invention, there is provided an imaging device (22) for photoelectrically converting incident subject light, an optical low-pass filter (23) disposed on the subject side relative to the imaging device, and a subject more than the optical low-pass filter. An imaging device (10) comprising: an optical element (24) arranged on the side; and vibration generating means (27) for vibrating the optical element by applying a voltage, wherein the optical element is a single crystal It is a wave plate made of quartz.
A second aspect of the present invention is the imaging apparatus (10) according to the first aspect, wherein the wave plate has a phase difference of 90 degrees.
A third aspect of the present invention is the imaging apparatus (10) according to the first or second aspect, wherein the wavelength plate has a coating film that transmits only visible light on a surface on the subject side. It is characterized by.
Note that the configuration described with reference numerals may be improved as appropriate, or at least a part thereof may be replaced with another component.

  ADVANTAGE OF THE INVENTION According to this invention, the imaging device provided with the optical element which is not influenced by an optical characteristic or an internal structure can be provided.

It is a figure which shows the camera of embodiment. (A) is a cross-sectional view of the camera along the optical axis A. FIG. FIG. 2B is a longitudinal sectional view of the camera along the optical axis A. FIG. It is the schematic which shows the structure of an imaging unit. It is a front view when the diaphragm is viewed along the optical axis A from the subject side.

  Hereinafter, an embodiment in which an imaging apparatus according to the present invention is applied to a digital camera will be described with reference to the drawings. Each figure shown below is provided with an XYZ orthogonal coordinate system for ease of explanation and understanding. In this coordinate system, the direction toward the right side when viewed from the photographer at the camera position (hereinafter referred to as the normal position) when the photographer shoots a horizontally long image with the optical axis A being horizontal is defined as the X plus direction. Further, the direction toward the upper side in the normal position is defined as the Y plus direction. Further, the direction toward the subject at the normal position is taken as the Z direction.

  FIG. 1 is a diagram illustrating a camera 1 according to the present embodiment. 1A is a transverse sectional view of the camera 1 along the optical axis A, and FIG. 1B is a longitudinal sectional view of the camera 1 along the optical axis A.

  The camera 1 includes a camera body 10 as an imaging device and a lens barrel 50. The camera 1 of the present embodiment is a lens interchangeable digital camera in which a lens barrel 50 can be attached to and detached from the camera body 10. In FIG. 1, the lens L of the lens barrel 50 is depicted by simplifying the lens. The lens L is actually composed of a plurality of lenses.

  The camera body 10 includes a mirror unit 11, a finder screen 12, a pentamirror 12a, an eyepiece 14, a photometric element 15, an AF detection element 16, a shutter 17, a sequence motor 18, a display unit 19, An imaging unit 20.

  The mirror unit 11 includes a main mirror 11a and a sub mirror 11b. The main mirror 11a is arranged in the photographing optical path and reflects an object position in the direction of the pentamirror 12a (indicated by a solid line in the figure) and a retracted position (indicated by a two-dot chain line in the figure) retracted from the photographing optical path. (Position), and is configured to be rotatable. The main mirror 11a is disposed at the observation position when observing the subject, and is disposed at the retracted position when photographing. The main mirror 11a is a half mirror near the center.

  The sub mirror 11b is a member that reflects the subject light that has passed through the half mirror toward the AF detection element 16 when the main mirror 11a is at the observation position. The sub mirror 11b is disposed so as to overlap the back surface of the main mirror 11a as the main mirror 11a is retracted, and retracts from the photographing optical path.

  The viewfinder screen 12 is a member that forms an image of subject light guided from the main mirror 11a during subject observation. The image formed on the finder screen 12 is guided in the direction of the eyepiece 14 by the pentamirror 12a and observed by the photographer.

  The photometric element 15 is a sensor that detects the amount of light of the image formed on the finder screen 12. Information on the amount of light detected by the photometric element 15 is output to a body control unit (not shown) and used when determining exposure at the time of photographing.

  The AF detection element 16 is a sensor that detects the focus adjustment state of the lens L based on subject light guided from the sub mirror 11b during subject observation. The AF detection element 16 divides the subject light guided from the sub-mirror 11b into two parts by a mask (not shown), and then re-images it on two line sensors (not shown), so that the relative image of the image on the line sensor is relative. The focus adjustment state of the lens L is detected by calculating the shift amount (phase difference).

  The shutter 17 includes a plurality of shutter curtains that travel at predetermined intervals. The shutter 17 opens and closes the shutter curtain according to the operation of the release button, and adjusts the amount of light incident on the imaging surface.

  The sequence motor 18 drives the mirror unit 11 and charges the shutter 17.

  The display unit 19 is a display device such as a liquid crystal display device disposed on the back surface (surface in the negative Z direction) of the camera body 10. The display unit 19 displays a captured image (reproduced image, live view image) captured by the imaging unit 20, a menu screen for performing various settings, and the like.

  The imaging unit 20 is a device that converts an image formed on the imaging element 22 into an electrical signal and outputs it to a body control unit (not shown) when the main mirror 11a is disposed at the retracted position during imaging. . A specific configuration of the imaging unit 20 will be described later.

  FIG. 2 is a schematic diagram illustrating the configuration of the imaging unit 20. The imaging unit 20 includes an imaging element 22, an OLPF 23, and a diaphragm 24 as an optical element, when roughly classified. Note that illustration of the peripheral members is omitted. The imaging element 22 is a photoelectric conversion element that photoelectrically converts subject light incident through the lens L (FIG. 1). The image sensor 22 is composed of a photodiode (not shown) and a CCD or CMOS.

  The OLPF 23 is an optical filter that removes a component having a high spatial frequency from incident subject light and guides the subject light to the image sensor 22. The OLPF 23 is formed by laminating a first birefringent plate 23a, an infrared cut glass 23b, a quarter wavelength plate 23c, and a second birefringent plate 23d in this order from the subject side. In addition, the function and arrangement of each part constituting the OLPF 23 are not limited to the example of the present embodiment, and can be appropriately combined.

  The first birefringent plate 23a is made of a single crystal crystal and is disposed closest to the subject. The first birefringent plate 23a converts incident light into two linearly polarized light components whose vibration directions are orthogonal to each other and emits the converted light.

  The infrared cut glass 23b absorbs light having a longer wavelength than the infrared region from the incident light. In the present embodiment, an example in which the infrared cut glass 23b is disposed between the first birefringent plate 23a and the quarter-wave plate 23c is shown. However, the present invention is not limited to this example. The image sensor 22 may be the most.

  The quarter-wave plate 23c is made of single crystal quartz, and is disposed closer to the image sensor 22 than the infrared cut glass 23b. The quarter-wave plate 23c causes a phase difference of 90 degrees between two components whose vibration directions included in the light incident through the first birefringent plate 23a are orthogonal to each other. ) Is converted into a circularly polarized light component and emitted.

  The second birefringent plate 23d is made of single crystal quartz, and is disposed closer to the imaging element 22 than the quarter-wave plate 23c. The second birefringent plate 23d converts the incident light (circularly polarized light component) into two linearly polarized light components whose vibration directions are orthogonal to each other and emits the converted light.

  Antireflection films 25 are respectively formed on the subject side surface and the image sensor 22 side surface of the OLPF 23 configured as described above.

  The diaphragm 24 is a wave plate made of single crystal quartz, and is disposed closer to the subject than the OLPF 23. As the diaphragm 24 of this embodiment, a phase difference of 90 degrees is generated between two components whose vibration directions included in the incident light are orthogonal to each other, and the incident light (linearly polarized light component) is converted into a circularly polarized light component. A quarter-wave plate that converts and emits light is used. Further, a visible light transmitting film 26 that transmits only visible light is formed on the subject side surface of the diaphragm 24. An antireflection film 25 is formed on the surface on the image sensor 22 side.

  The quartz used as the diaphragm 24 is a member having a higher strength than glass (Mohs hardness is 7 for quartz and 5-6 for glass). For this reason, plate thickness can be made thinner than glass. In addition, since the coating film formed on the diaphragm 24 is the visible light transmitting film 26 that transmits only visible light, the surface of the surface that cannot be seen with the naked eye is conspicuous like the coating film formed on the glass surface. There is no. Further, the visible light transmission film 26 can be easily formed as compared with the coating film formed on the glass surface. Furthermore, since the wave plate made of single crystal quartz may be cut out in a direction parallel to the optical axis of the quartz raw stone, it can be cut out from the quartz raw stone more easily than the quartz birefringent plate.

  In addition, the wavelength plate made of single crystal quartz does not need to consider the direction of the optical axis when placed on the subject side with respect to the OLPF 23, and thus is not restricted by optical design unlike the quartz birefringent plate. Furthermore, unlike a quartz crystal birefringent plate, a wave plate made of single crystal quartz does not linearly polarize all incident light, and can be regarded as having almost the same optical characteristics as glass. There is no restriction on the configuration of the OLPF 23 to be arranged.

  FIG. 3 is a front view of the diaphragm 24 as viewed along the optical axis A from the subject side. As shown in FIG. 3, the diaphragm 24 includes a piezoelectric element 27. The piezoelectric element 27 is attached to one side edge of the X direction on the subject side surface of the diaphragm 24 by adhesion. The piezoelectric element 27 functions as a vibration generating unit that resonates and vibrates the diaphragm 24 when an AC voltage having a specific frequency (resonance frequency of the diaphragm 24) is applied from a piezoelectric element drive circuit (not shown).

  A flexible printed board (not shown) is connected to the end of the piezoelectric element 27. This flexible printed circuit board is electrically connected to the piezoelectric element driving circuit, and applies an AC voltage having a specific frequency to the piezoelectric element 27. When an AC voltage having a specific frequency is applied to the piezoelectric element 27, the diaphragm 24 resonates with the vibration of the piezoelectric element 27, and vibration is generated in the diaphragm 24. Due to this vibration, foreign matter adhering to the surface of the diaphragm 24 is removed.

According to the said embodiment, there exist the following effects.
(1) Since the diaphragm 24 as an optical element is formed of a wave plate made of single crystal quartz, the strength can be increased compared to the case where the diaphragm 24 is formed of glass. In addition, the wave plate made of single crystal quartz does not need to consider the optical axis direction when arranged on the subject side from the OLPF 23, and thus is not restricted by optical design unlike the quartz birefringent plate. Furthermore, unlike a quartz crystal birefringent plate, a wave plate made of single crystal quartz does not linearly polarize all incident light, and can be regarded as having almost the same optical characteristics as glass. There is no restriction on the configuration of the OLPF 23 to be arranged.
Therefore, according to the present embodiment, it is possible to provide the camera body 10 including the diaphragm 24 as an optical element that is not affected by the optical characteristics and the internal configuration.
(2) Since the phase difference of the diaphragm 24 is 90 degrees, the best optical characteristics can be obtained with respect to the rear OLPF 23.
(3) Since the coating film formed on the vibration plate 24 is the visible light transmitting film 26 that transmits only visible light, the surface stains that are not visible to the naked eye, such as when the coating film is formed on the glass surface, are observed. Does not stand out. Further, the visible light transmission film 26 can be easily formed as compared with the coating film formed on the glass surface.
(Deformation)

Without being limited to the embodiment described above, the present invention can be variously modified and changed as described below, and these are also within the scope of the present invention.
(1) The phase difference of the diaphragm 24 is not limited to 90 degrees, and may be 0 degrees or 45 degrees.
(2) The arrangement of the piezoelectric elements 27 is not limited to the example of FIG. 3, and may be arranged on one side edge of the diaphragm 24 in the Y direction, or on both side edges in the X direction or both side edges in the Y direction. May be. In addition, the piezoelectric element 27 may be attached to the surface of the vibration plate 24 on the imaging element 22 side.
(3) The imaging apparatus according to the present invention can be applied not only to an interchangeable lens digital camera but also to a camera in which a camera body and a lens are integrated.

  Moreover, although the said embodiment and modification can be used in combination suitably, since the structure of each embodiment is clear by illustration and description, detailed description is abbreviate | omitted. Furthermore, the present invention is not limited by the embodiment described above.

  1: camera, 10: camera body, 20: imaging unit, 22: imaging device, 23a: first birefringent plate, 23b: infrared cut glass, 23c: 1/4 wavelength plate, 23d: second birefringent plate, 24: diaphragm, 25: antireflection film, 26: visible light transmission film, 27: piezoelectric element, 50: lens barrel

Claims (3)

An image sensor that photoelectrically converts incident subject light, an optical low-pass filter that is disposed closer to the subject than the image sensor, an optical element that is disposed closer to the subject than the optical low-pass filter, and applying the voltage to the optical element A vibration generating means for vibrating the element;
The imaging device according to claim 1, wherein the optical element is a wave plate made of single crystal quartz. The imaging apparatus according to claim 1,
The wave plate has an phase difference of 90 degrees. The imaging apparatus according to claim 1 or 2,
The imaging device, wherein the wavelength plate has a coating film that transmits only visible light on a surface on the subject side.

Images