Optical apparatus and imaging apparatus

An optical apparatus is disclosed. The optical apparatus includes: a first optical element having a first polarizing layer containing a material having a refractive index that changes in accordance with the magnitude of applied voltage and first and second transparent electrodes sandwiching both sides of the first polarizing layer in the direction of thickness and polarizing light passing through the first polarizing layer in the direction of thickness; and a second optical element having a second polarizing layer containing a material having a refractive index that changes in accordance with the magnitude of applied voltage and third and fourth transparent electrodes sandwiching both sides of the second polarizing layer in the direction of thickness and polarizing light passing through the second polarizing layer in the direction of thickness.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese Patent Application JP2006-086895 filed in the Japanese Patent Office on Mar. 28, 2006, the entire contents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

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

2. Description of the Related Art

There is an imaging apparatus such as a digital still camera that uses an imaging sensor to image a subject image captured by a shooting optical system.

When a camera shake occurs during a shooting operation by using an imaging apparatus, a forward motion occurs on the imaging plane of the imaging sensor, which results in a failure in shooting.

In order to prevent the occurrence of a forward motion, a forward motion compensating apparatus has been proposed (refer to JP-A-3-188430 (Patent Document 1)) in which a vibration of the imaging apparatus is detected by vibration detecting means such as an acceleration sensor, and a part of a lens in a shooting optical system is moved in the direction orthogonal to an optical axis by a lens driving mechanism such as a linear motor based on the detection result.

SUMMARY OF THE INVENTION

Such a forward motion compensating apparatus has a large space occupied by the lens driving mechanism and large power consumption, which is disadvantageous for the decreases in size and power consumption of the imaging apparatus.

Accordingly, it is desirable to propose an optical apparatus, which prevents a forward motion securely and, at the same time, is advantageous for the decreases in size and power consumption, and an imaging apparatus including the optical apparatus.

According to an embodiment of the present invention, there is provided an optical apparatus including a first optical element having a first polarizing layer containing a material having a refractive index that changes in accordance with the magnitude of applied voltage and first and second transparent electrodes sandwiching both sides of the first polarizing layer in the direction of thickness and polarizing light passing through the first polarizing layer in the direction of thickness, and a second optical element having a second polarizing layer containing a material having a refractive index that changes in accordance with the magnitude of applied voltage and third and fourth transparent electrodes sandwiching both sides of the second polarizing layer in the direction of thickness and polarizing light passing through the second polarizing layer in the direction of thickness, wherein the first and second optical elements are placed one over another in the direction of thickness of the first and second polarizing layers, the first and second transparent electrodes apply a first voltage that changes in magnitude in a stepwise manner or continuously to the first polarizing layer along a first direction orthogonal to the direction of thickness, and the third and fourth transparent electrodes apply a second voltage that changes in magnitude in a stepwise manner or continuously to the second polarizing layer along the first direction.

According to another embodiment of the invention, there is provided an imaging apparatus including a shooting optical system conducting a subject image, an image sensor on an optical axis of the shooting optical system, and an optical apparatus before the image sensor on the optical axis, wherein the optical apparatus has a first optical element having a first polarizing layer containing a material having a refractive index that changes in accordance with the magnitude of applied voltage and first and second transparent electrodes sandwiching both sides of the first polarizing layer in the direction of thickness and polarizing light passing through the first polarizing layer in the direction of thickness, and a second optical element having a second polarizing layer containing a material having a refractive index that changes in accordance with the magnitude of applied voltage and third and fourth transparent electrodes sandwiching both sides of the second polarizing layer in the direction of thickness and polarizing light passing through the second polarizing layer in the direction of thickness, wherein the first and second optical elements are placed one over another in the direction of thickness of the first and second polarizing layers, the first and second transparent electrodes apply a first voltage that changes in magnitude in a stepwise manner or continuously to the first polarizing layer along a first direction orthogonal to the direction of thickness, and the third and fourth transparent electrodes apply a second voltage that changes in magnitude in a stepwise manner or continuously to the second polarizing layer along the first direction.

According to the embodiments of the invention, an optical apparatus can displace the optical path by the simple construction including a first optical element having a first polarizing layer and first and second transparent electrodes and a second optical element having a second polarizing layer and third and fourth transparent electrodes. Thus, a smaller space may be required to occupy, and power for forming refractive index distributions in the first and second polarizing layers may be reduced.

Therefore, when the optical apparatus is used for compensating a camera shake in an imaging apparatus, a camera shake can be securely compensated, which is extremely advantageous for the decreases in size and power consumption.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

With reference to drawings, an embodiment of the invention will be described next.

An optical apparatus according to this embodiment of the invention is built in an imaging apparatus.

FIG. 1is a block diagram showing a construction of an imaging apparatus10.

As shown inFIG. 1, the imaging apparatus10is a digital still camera.

The imaging apparatus10has an external case (not shown), and the case has a lens barrel12, a driving unit14, a signal processing section16, a control section18, an operating section20, an LCD display22, an external interface24and a media interface25built in.

The lens barrel12has a barrel1202, and the barrel1202has a shooting optical system1204and an image sensor1206that images a subject image guided by the shooting optical system1204. An optical apparatus26according to this embodiment of the invention is provided before the image sensor1206on the optical axis of the shooting optical system1204.

The driving unit14has a driving section1402, a driver1404, a detecting section1406, a driver1408, a timing generating circuit1410and an A/D converter1412. The driving section1402includes an actuator that drives a movable lens in the shooting optical system1204. The driver1404supplies a drive signal to the driving section1402. The detecting section1406detects a travel of the driving section1402. The driver1408supplies a drive signal to the image sensor1206. The timing generating circuit1410supplies a timing signal to the image sensor1206and the driver1408. The A/D converter1412A/D-converts an imaged signal generated by the image sensor1206.

The driving unit14further has a driver28and a movement detecting section30. The driver28supplies a drive signal to the optical apparatus26. The movement detecting section30includes an acceleration sensor and/or a gyrosensor that detects an amount of a camera shake of the imaging apparatus10.

The signal processing section16may generate image data by performing predetermined signal processing on an imaged signal supplied from the A/D converter1412and perform various operations (such as auto-focus operation, automatic exposure operation, automatic white balance operation and compression/decompression of image data) relating to shooting. The signal processing section16may include a DSP, for example.

The signal processing section16uses a memory (SDRAM)17through an SDRAM controller1602as a work area for image data processing.

The control section18includes a CPU1802, a RAM1804, a flash ROM1806, a clock circuit1808, and a system bus1810connecting them.

The CPU1802operates based on a control program stored in the flash ROM1806.

The CPU1802sends/receives data to/from the RAM1804, flash ROM1806and clock circuit1808through the system bus1810. The CPU1802further operates in accordance with an operation command supplied from the operating section20, a detection signal supplied from the detecting section1406, a detection signal supplied from the movement detecting section30and so on. The CPU1802further controls the drivers1404and28, timing generating circuit1410and A/D converter1412of the driving unit14.

The CPU1802further sends/receives data including image data to/from an internal memory or a recording medium2502such as a memory card through the media interface25. The CPU1802further causes the display22to display image data through an LCD controller2202. The CPU1802further sends/receives data including image data to/from an external apparatus (such as a personal computer and a printer) through the external interface24.

The operating section20includes a power switch, a shutter button, and operation buttons for switching the shooting mode and performing various setting.

The optical apparatus26will be described next.

First of all, an optical element32in the optical apparatus26will be described.

FIG. 2is an explanatory diagram showing the principle of the optical element32in the optical apparatus26, andFIG. 3is an explanatory diagram of a prism effect of the optical element32.

As shown inFIG. 2, the optical element32includes first and second transparent substrates34and36spaced apart from and extending in parallel with each other, first and second transparent electrodes38and40on the surfaces of the first and second transparent substrates34and36, which face against each other, and a polarizing layer42filled between the first and second transparent electrodes38and40.

The first transparent electrode38has multiple divided electrodes39in a band shape, which align at uniform intervals in the direction orthogonal to the direction of extension thereof. The direction that the multiple divided electrodes39align is referred as first direction, and the first direction is the direction orthogonal to the direction of thickness of the polarizing layer42.

The second transparent electrode40includes a single electrode extending across the entire area of the surface of the second transparent substrate36.

The polarizing layer42contains a material with a refractive index depending on the magnitude of the applied voltage. A medium with an anisotropic refractive index may be adopted as the material. The material may be but is not limited to:1) nematic liquid crystal that has higher orientation and positive dielectric anisotropy in which the liquid crystal molecules change from the homogeneous orientation to the homeotropic orientation in accordance with the magnitude of the electric field applied between the substrates as in a general liquid crystal element;2) nematic liquid crystal that has negative dielectric anisotropy in which the liquid crystal molecules change from the homeotropic orientation to the homogeneous orientation in accordance with the magnitude of the electric field applied between the substrates if a homeotropic orientation film is formed on the substrate surfaces; or3) lithium tantalate (LiTao3) or lithium niobate (LiNbo3) with a refractive index depending on the magnitude of an applied electric field. Notably, lithium tantalate is generally known as one which can form a larger refractive index than that of liquid crystal.

Here, the potential at the ground level, for example, may be applied to the second transparent electrode40as a reference potential VL.

A voltage that changes in magnitude in a stepwise manner or serially along the first direction is applied to the multiple divided electrodes39in the first transparent electrode38. The voltage may be a direct-current voltage (or alternate current voltage) of several to several tens V, for example.

Here, the voltage to be applied to the divided electrode39-1at one end in the first direction is the reference voltage VL, and the voltage to be applied to the divided electrode39-N at the other end in the first direction is the highest voltage VH.

When the difference in voltage between adjacent divided electrodes is Δ V, the voltage difference Δ V is expressed as:
ΔV=(VH−VL)/(N−1)  [EQ1]

When a voltage that changes in magnitude in a stepwise manner or serially along the first direction is applied to the divided electrodes39, the voltages applied to the polarizing layer42by the divided electrodes39in this way form an electric field distribution that changes in magnitude in a stepwise manner or serially along the first direction.

Thus, a refractive index distribution that changes in a stepwise manner or serially along the first direction is formed in the polarizing layer42in accordance with the electric field distribution.

With the formation of the refractive index distribution, an input light beam Li traveling in the direction of thickness of the polarizing layer42which is input to the first transparent electrode38, is refracted by the polarizing layer42in accordance with the refractive index distribution and is output as an output light beam Lo from the second transparent substrate36.

In other words, as shown inFIG. 3, the optical element32acts as a so-called prism, and the input light beam Li incident in the direction of thickness of the polarizing layer42is polarized and output as an output light beam Lo.

Next, the optical apparatus26will be described.

FIG. 4is a section view showing a construction of the optical apparatus26.

As shown inFIG. 4, the optical apparatus26includes first, second and third transparent substrates44,46and48, first to fourth transparent electrodes50,52,54and56and first and second polarizing layers58and60.

The first, second and third transparent substrates44,46and48are spaced apart from and extend in parallel with each other.

The first transparent electrode50is provided on the surface where the first transparent substrate44face against the second transparent substrate46.

The second transparent electrode52is provided on the surface where the second transparent substrate46faces against the first transparent substrate44.

The third transparent electrode54is provided on the surface where the second transparent substrate46faces against the third transparent substrate48.

The fourth transparent electrode56is provided on the surface where the third transparent substrate48faces against the second transparent substrate46.

The first polarizing layer58is filled between the first and second transparent electrodes50and52.

The second polarizing layer60is filled between the third and fourth transparent electrodes54and56.

The first and second polarizing layers58and60contain a material that changes in refractive index in accordance with the magnitude of the voltage applied thereto, like the polarizing layer42.

Thus, according to this embodiment, the first and second transparent substrates44and46, the first and second transparent electrodes50and52, and the first polarizing layer58are included in a first optical element32A. The second and third transparent substrates46and48, the third and fourth transparent electrodes54and56and the second polarizing layer60are included in a second optical element32B. In other words, the optical apparatus26includes the first and second optical elements32A and32B placed one over another in the direction of thickness of the first and second polarizing layers58and60.

The first transparent electrode50has multiple divided electrodes51in a band shape, which align at uniform intervals in the direction orthogonal to the direction of extension of the band shape. The direction that the multiple divided electrodes51align is referred as first direction, and the first direction is the direction orthogonal to the direction of thickness of the first and second polarizing layers58and60.

The second transparent electrode52includes a single electrode extending across the entire area of the surface where the second transparent substrate46faces the first polarizing layer58.

The third transparent electrode54includes a single electrode extending across the entire area of the surface where the second transparent substrate46faces the second polarizing layer60.

The fourth transparent electrode56has multiple divided electrodes57in a band shape, which align at uniform intervals in the direction orthogonal to the direction of extension of the band shape. The direction that the multiple divided electrodes57align agrees with the first direction.

According to this embodiment, the divided electrodes51and the divided electrodes57are similar in size and shape, and the divided electrodes51and divided electrodes57are placed such that the respective contours can agree with each other at the sight from the direction of thickness of the first and second polarizing layers58and60.

FIG. 5Ais a section view of the optical apparatus26,FIG. 5Bis an explanatory diagram of a first electric field distribution to be applied to the first polarizing layer58,FIG. 5Cis an explanatory diagram of a first refractive index distribution in the first polarizing layer58,FIG. 5Dis an explanatory diagram of a second electric field distribution to be applied to the second polarizing layer60, andFIG. 5Eis an explanatory diagram of a second refractive index distribution in the second polarizing layer60.FIG. 6is an explanatory diagram of prism effects of the optical apparatus26.

As shown inFIG. 5A, the potential at the ground level, for example, may be commonly applied as the reference voltage VL to the second and third transparent electrodes52and54.

A voltage that changes in magnitude in a stepwise manner or serially is applied to the multiple divided electrodes51in the first transparent electrode50and the multiple divided electrodes57in the fourth transparent electrode56along the first direction, like in the optical element32.

Thus, as shown inFIG. 5B, the voltage forms a first electric field distribution in the first polarizing layer58. The first electric field distribution changes in magnitude in a stepwise manner or serially along the first direction. As shown inFIG. 5D, the voltage forms a second electric field distribution in the second polarizing layer60. The second electric field distribution changes in magnitude in a stepwise manner or serially along the first direction.

Therefore, as shown inFIG. 5C, a first refractive index distribution that changes in a stepwise manner or serially is formed in the first polarizing layer58in accordance with the first electric field distribution. As shown inFIG. 5E, a second refractive index distribution that changes in a stepwise manner or serially is formed in the second polarizing layer60in accordance with the second electric field distribution.

Here, the gradient of the first electric field distribution and the gradient of the second electric field distribution are opposite in polarity of the rate of change along the first direction and are the same in absolute value of the rate of change. As a result, the gradient of the first refractive index distribution and the gradient of the second refractive index distribution are opposite in polarity of the rate of change along the first direction and are the same in absolute value of the rate of change.

With the formation of the refractive index distributions, the input light beam Li traveling in the direction of thickness of the first and second polarizing layers58and60and entering to the first transparent substrate44is refracted by the first polarizing layer58in accordance with the first refractive index distribution, passes through the second transparent substrate46, is refracted by the second polarizing layer60in accordance with the second refractive index distribution and is output from the third transparent substrate48as an output light beam Lo, as shown inFIG. 5A.

In other words, as shown inFIG. 6, the optical apparatus26(that is, the first and second optical elements32A and32B) acts as two prisms, and the input light beam Li incident in the direction of thickness of the polarizing layer42is polarized twice and is then output as the output light beam Lo.

In this case, the polarization of the input light beam Li by the optical apparatus26twice displaces the output light beam Lo in parallel with the extension line of the input light beam Li and in the first direction.

The amount of displacement of the output light beam Lo with reference to the extension line of the input light beam Li in the first direction, that is, the amount of displacement of the optical path displaced by the optical apparatus26depends on the magnitudes of the gradients of the first and second refractive index distributions.

Therefore, changing the magnitude of the voltage to be applied to the first and fourth transparent electrodes50and56and changing the gradients of the first and second electric field distributions allow the adjustment of the amount of displacement of the optical path.

Notably, the light polarized by the first optical element32A travels within the second transparent substrate46in parallel with the input light beam Li and is then polarized by the second optical element32B. Therefore, changing the dimension of the second transparent substrate46in the direction of thickness allows the adjustment of the amount of displacement of the optical path.

Next, an operation for compensating a camera shake by using the optical apparatus26in the imaging apparatus10will be described.

As shown inFIG. 1, based on the amount of a movement detected by the movement detecting section30, the CPU1802calculates an amount of displacement (amount of correction) of the optical path by the optical apparatus26, which may be required for compensating the amount of the movement.

Then, the CPU1802supplies a control signal to the driver28based on the amount of displacement. Thus, the voltage the magnitude of which corresponds to the amount of displacement (amount of correction) is applied from the driver28to the first and fourth transparent electrodes50and56of the optical apparatus26.

Therefore, the amount of displacement (amount to be compensated) of the optical path by the optical apparatus26can be adjusted so as to correspond to the amount of the movement detected by the movement detecting section30, which compensates the forward motion of the subject image guided to the image sensor1206.

Since the optical apparatus26alone only displaces the optical path into the first direction, providing one optical apparatus26can only compensate a forward motion in one axis direction orthogonal to the optical axis of the shooting optical system1204.

FIG. 7is an explanatory diagram of the imaging apparatus10having two optical apparatus26built in.

As shown inFIG. 7, two optical apparatus26are placed before the image sensor1206on the optical axis of the shooting optical system1204such that the first directions of the two optical apparatus26can be orthogonal to the optical path. Thus, for example, the first direction of one of the two optical apparatus26can be horizontal, and the first direction of the other optical apparatus26can be vertical. Therefore, the optical path can be displaced in all directions orthogonal to the optical axis, and forward motions in all directions can be compensated.

According to this embodiment, the simple construction of the optical apparatus26including the first optical element32A having the first and second transparent electrodes50and52sandwiching the first polarizing layer58and the second optical element32B having the third and fourth transparent electrodes54and56sandwiching the second polarizing layer60may only require a small space to occupy and a small amount of power for forming the refractive index distributions in the first and second polarizing layers58and60.

Thus, the use of the optical apparatus26for the camera shake compensation of the imaging apparatus10can apparently compensate a camera shake securely and is extremely advantageous for reducing the size and power consumption more than the case that a lens is moved by an actuator as in the past.

Since, according to this embodiment, the output light beam Lo is parallel to the line of extension of the input light beam Li of the optical apparatus26and is displaced in the first direction, the light guided to the image sensor1206by the shooting optical system1204is displaced in parallel with the optical axis of the shooting optical system1204, which may advantageously compensate a one-sided blur in a subject image formed on the image sensor1206.

Having described the case that the first and fourth transparent electrodes50and56have the multiple divided electrodes51and57in a band shape and the second and third transparent electrodes52and54have the single electrode according to this embodiment, the first and fourth transparent electrodes50and56may have a single electrode, and the second and third transparent electrodes52and54may have multiple divided electrodes.

The first and second transparent electrodes50and52and the third and fourth transparent electrodes54and56may only require to form an electric field distribution that changes in magnitude in a stepwise manner or serially along the first direction in the first and second polarizing layers58and60, and the form is not limited.

Second Embodiment

A second embodiment will be described next.

The second embodiment is different from the first embodiment in that a dielectric layer is provided between a transparent electrode and a polarizing layer.

FIG. 8is a section view showing a construction of an optical apparatus26according to the second embodiment. In the description of this embodiment, the same reference numerals are given to the same or like parts and members as those in the first embodiment.

As shown inFIG. 8, a dielectric layer62is provided between the first transparent electrode50and the first polarizing layer58, and a dielectric layer64is provided between the fourth transparent electrode56and the second polarizing layer60. The dielectric layers62and64may be only required to contain a dielectric material that allows light to pass through and may contain a clear synthetic resin or clear glass.

The second embodiment certainly provides the same effects as those of the first embodiment and can prevent an uneven electric field occurring between the adjacent divided electrodes51and57from being applied to the polarizing layers58and60by providing the dielectric layers62and64.

Thus, the gradients of the electric field distributions formed in the first and second polarizing layers58and60by the first and second transparent electrodes50and52and the third and fourth transparent electrodes54and56, that is, the gradients of the refractive index distributions can be smoothed, which is advantageous for preventing the occurrence of the aberration in the optical apparatus26and for improving the quality of a subject image formed in the image sensor1206.

Third Embodiment

A third embodiment is a variation example of the second embodiment and is different from the second embodiment in that the second and third transparent electrodes52and54also include divided electrodes in a band shape.

FIG. 9is a section view showing a construction of the optical apparatus26of the third embodiment.

As shown inFIG. 9, the second transparent electrode52includes multiple divided electrodes53similar in size and shape to the divided electrodes51in the first transparent electrode50.

At the sight in the direction of thickness, the divided electrodes51of the first transparent electrode50and the divided electrodes53of the second transparent electrode52are placed such that the contours can agree with each other.

The third transparent electrode54also includes multiple divided electrodes55similar in size and shape to the divided electrodes57in the fourth transparent electrode56.

At the sight in the direction of thickness, the divided electrodes55of the third transparent electrode54and the divided electrodes57of the fourth transparent electrode56are placed such that the contours can agree with each other.

A dielectric layer66is provided between the second transparent electrode52and the first polarizing layer58, and a dielectric layer68is provided between the third transparent electrode54and the second polarizing layer60. The dielectric layers66and68contain a dielectric material that allows light to pass through like the dielectric layers62and64, which can prevent an uneven electric field occurring between the adjacent divided electrodes53and55from being applied to the polarizing layers58and60.

According to the third embodiment, the divided electrodes51,53,55and57are similar in size and shape.

Certainly in addition to the same effects as those of the second embodiment, the third embodiment provides the flexibility for defining the magnitude of the voltage to be applied to the first and second polarizing layers58and60since all of the first to fourth transparent electrodes50,52,54and56have the multiple divided electrodes51,53,55and57. Thus, the gradients of the electric field distributions to be formed in the first and second polarizing layers58and60, that is, the gradients of the refractive index distributions can be adjusted freely, which is advantageous for adjusting the amount of displacement of the optical path freely.

Fourth Embodiment

A fourth embodiment is a variation example of the third embodiment and is different from the third embodiment in the positions where divided electrodes are placed.

FIG. 10is a section view showing a construction of an optical apparatus26according to the fourth embodiment.

As shown inFIG. 10, like the third embodiment, the divided electrodes51,53,55and57of the first, second, third and fourth transparent electrodes50,52,54and56are similar in size and shape.

The adjacent divided electrodes are all spaced apart at uniform intervals in the first, second, third and fourth transparent electrodes50,52,54and56.

At the sight from the direction of thickness, the divided electrodes51of the first transparent electrode50and the divided electrodes53of the second transparent electrode52are placed such that the contours do not overlap one another, that is, the divided electrodes51and53are placed alternately along the first direction.

At the sight from the direction of thickness, similarly, the divided electrodes55of the third transparent electrode54and the divided electrodes57of the fourth transparent electrode56are also placed such that the contours do not overlap one another, that is, the divided electrodes55and57are placed alternately along the first direction.

According to the fourth embodiment, certainly in addition to the same effects as those of the third embodiment, the divided electrodes51and53of the first transparent electrode50and second transparent electrode52are positioned alternately so as not to overlap one another, and the divided electrodes55and57of the third transparent electrode54and fourth transparent electrode56are positioned alternately so as not to overlap one another. Therefore, it is more advantageous for improving and making the light transmittance uniform than the third embodiment, which is advantageous for improving the optical characteristics of the optical apparatus26.