Camera module having first and second imaging optical system controlled in relation to imaging modes and imaging method

According to one embodiment, in a first imaging mode, an imaging mode control unit allows a second imaging optical system to function in an optical path between an imaging unit and a first imaging optical system and stops focus adjustment. In a second imaging mode, the imaging mode control unit stops the function of the second imaging optical system and allows the focus adjustment to be performed. The first imaging optical system takes in a light from an object to the imaging unit. The second imaging optical system forms an image piece in each pixel block.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-094731, filed on Apr. 18, 2012; the entire contents of all of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a camera module and an imaging method.

BACKGROUND

Recently, a camera module having a compound-eye configuration capable of simultaneously photographing an object from a plurality of points of view has been proposed. The camera module can perform estimation of object distance and reconstruct a two-dimensional image through image connection by performing an image process for an image group photographed by using the compound-eye configuration. The camera module can obtain depth information of an object from a plurality of images according to different points of view. The camera module performs an image process, for example, refocusing or the like by using the depth information.

The camera module can obtain a high-resolution image though simple, easy operation by using an autofocusing function. In order for a user to photograph a desired image, it is preferable that the camera module is configured so that the refocusing function by the compound-eye configuration and the autofocusing function by an autofocusing mechanism can be separately used according to user's intention.

DETAILED DESCRIPTION

In general, according to one embodiment, a camera module is configured to include an imaging unit, a first imaging optical system, a second imaging optical system, a focus adjustment unit, and an imaging mode control unit. The imaging unit is configured to include pixel cells. The pixel cells are arranged in an array shape. The imaging unit images an object image. The first imaging optical system takes in a light from an object to the imaging unit. The second imaging optical system forms an image piece in each pixel block. The pixel block is configured to include a plurality of pixel cells. The image piece corresponds to a portion of the object image. The focus adjustment unit performs focus adjustment of the first imaging optical system. The imaging mode control unit controls driving of the second imaging optical system and the focus adjustment unit in the first imaging mode and the second imaging mode. In the first imaging mode, the imaging mode control unit allows the second imaging optical system to function in an optical path between the imaging unit and the first imaging optical system and stops the focus adjustment of the focus adjustment unit. In the second imaging mode, the imaging mode control unit stops the function of the second imaging optical system and performs the focus adjustment of the focus adjustment unit.

Exemplary embodiments of a camera module and an imaging method will be explained below in detail with reference to the accompanying drawings. The present invention is not limited to the following embodiments.

FIG. 1is a block diagram illustrating a schematic configuration of a digital camera including a camera module according to a first embodiment. A digital camera1is configured to include a camera module2and a post stage processing unit3.

The camera module2is configured to include an imaging optical system4and a solid-state imaging device5. The post stage processing unit3is configured to include an image signal processor (ISP)6, a storage unit7, and a display unit8. In addition to the digital camera1, the camera module2is applied to electronic apparatuses such as a camera-attached mobile terminal.

The imaging optical system4receives a light from an object to form an object image. The imaging optical system4includes a first imaging optical system and a second imaging optical system which are described below. The solid-state imaging device5images the object image to generate an image signal.

The ISP6performs a signal process on the image signal input from the solid-state imaging device5. The storage unit7stores an image which is subjected to the signal process of the ISP6. The storage unit7outputs the image signal to the display unit8according to user's operation or the like. The display unit8displays an image according to an image signal input from the ISP6or the storage unit7. The display unit8is, for example, a liquid crystal display.

FIG. 2is a block diagram illustrating a configuration of first and second lens modules, a solid-state imaging device, and an ISP. The first lens module11is configured to include a main lens13and a motor15. The main lens13constitutes the first imaging optical system. The main lens13takes in the light from the object to an image sensor20. The motor15supplies a driving force for the focus adjustment of the main lens13.

The second lens module12is configured to include a micro lens array (MLA)14and a motor16. The MLA14constitutes the second imaging optical system. The MLA14is configured by arranging a plurality of lens elements in an array shape. The MLA14forms an image piece. The image piece corresponds to a portion of the object image. The motor16supplies a driving force for moving the MLA14to a first position and a second position which are described below.

The solid-state imaging device5is configured to include an image sensor20, an imaging process circuit21, a micro lens array (MLA) driver22, and an autofocusing (AF) driver23. The image sensor20is an imaging unit which images an object image. The image sensor20allows a photodiode to convert the light incident through the imaging optical system into signal charges to image the object image. The image sensor20is, for example, a CMOS (complementary metal oxide semiconductor) image sensor. In addition to the CMOS image sensor, the image sensor20may be a CCD (charge coupled device).

The imaging process circuit21performs a signal process on an image signal from the image sensor20. The MLA driver22drives the motor16according to the control of the imaging mode control unit26described below.

The AF driver23detects a focused state by using a signal from the imaging process circuit21and drives the motor15. The AF driver23and the motor15function as a focus adjustment unit which performs the focus adjustment of the first imaging optical system. The AF driver23performs focus adjustment of any one of a phase difference detection method and a contrast detection method. The AF driver23switches between performing and stopping of the focus adjustment according to the control of the imaging mode control unit26.

The ISP6is configured to include a camera interface (I/F)24, an image receiving unit25, a signal process circuit27, a driver interface (I/F)28, and an imaging mode control unit26. The camera I/F24receives an input of the image signal from the solid-state imaging device5. The image receiving unit25receives the image signal input to the camera I/F24.

The signal process circuit27performs a signal process on the image received by the image receiving unit25. The driver I/F28outputs the image signal which is subjected to the signal process of the signal process circuit27to the storage unit7and the display unit8(seeFIG. 1). The imaging mode control unit26controls the driving of second imaging optical system and the focus adjustment unit in the first imaging mode and the second imaging mode.

FIG. 3is a schematic plan diagram illustrating an incidence side of an image sensor. The image sensor20is configured to include pixel cells31which are arranged in an array shape. Each pixel cell31includes a photodiode (not illustrated). Pixel blocks30including a plurality of the pixel cells31are set in the image sensor20. For example, the pixel block30is configured to include25pixel cells31which are arranged in an array shape of five pixels in the row direction and five pixels in the column direction. In addition, the number of pixel cells31included in the pixel block30may be appropriately changed.

FIG. 4is a schematic diagram illustrating a main lens, an MLA, and an image sensor in the first imaging mode.FIG. 5is a schematic diagram illustrating a main lens, an MLA, and an image sensor in the second imaging mode.

Lens elements17constituting the MLA14are installed corresponding to each of the pixel blocks30. The lens element17forms the object image, which is formed by the main lens13, as an image piece. The image piece corresponds to a portion of the object image. The MLA14forms an image piece in each pixel block30. In addition, the arrangement of the lens elements17may be any one of a tetragonal lattice arrangement, a hexagonal close-packed arrangement, and the like.

In the first imaging mode, the MLA14is inserted into an optical path between the main lens13and the image sensor20. The position where the MLA14is disposed in the first imaging mode is set as a first position. The first position is, for example, the position of the image forming plane of the main lens13in the first imaging mode.

In the second imaging mode, the MLA14is deviated from the optical path between the main lens13and the image sensor20. The position where the MLA14is disposed in the second imaging mode is set as a second position. The second position is a position other than the first position. For example, the second position is a position which is shifted from the first position in a two-dimensional direction perpendicular to the optical axis. In addition, the second position may be any position which is deviated from the optical path between the main lens13and the image sensor20.

When the imaging mode control unit26receives a command of changing the mode from the second imaging mode to the first imaging mode, the imaging mode control unit26controls the MLA driver22so as to move the MLA14from the second position to the first position. The imaging mode control unit26controls the AF driver23to move the main lens13so that the image forming plane of the main lens13is coincident with the incidence plane of the MLA14. In the first imaging mode, the imaging mode control unit26stops the focus adjustment of the AF driver23.

In the first imaging mode, the imaging mode control unit26allows the MLA14to function by inserting the MLA14into the first position and stops the focus adjustment of the AF driver23.

When the imaging mode control unit26receives a command of changing the mode from the first imaging mode to the second imaging mode, the imaging mode control unit26controls the MLA driver22so as to move the MLA14from the first position to the second position. The imaging mode control unit26controls the AF driver23to move the main lens13so that the image forming plane of the main lens13is coincident with the light receiving plane of the image sensor20. In the second imaging mode, the imaging mode control unit26performs the focus adjustment of the AF driver23.

In the second imaging mode, the imaging mode control unit26stops the function of the MLA14by detaching the MLA14from the first position to the second position and moves the main lens13and performs the focus adjustment of the AF driver23. In addition, with respect to the solid-state imaging device5, when the mode is changed from the first imaging mode to the second imaging mode, the moving of the main lens13may be performed by the focus adjustment of the AF driver23instead of the control of the imaging mode control unit26.

FIG. 6is a diagram illustrating an image piece generated by an image sensor in the first imaging mode.FIG. 7is a diagram illustrating an object image reconstruction process by an ISP. Herein, a case where a character string “ABCD” is imaged by the image sensor20and an object image reconstruction process is performed is exemplified.

The field of view where each lens element17forms the image piece32has an overlap range in the image forming plane of the main lens13according to a parallax. The character string “ABCD” is imaged by the image sensor20as an image piece32where overlapped portions are slight different from each other, for example, as illustrated inFIG. 6.

The signal process circuit27of the ISP6reconstructs an object image by connecting the image pieces32so that the overlapped portions are coincident with each other. The image piece32is reconstructed as the object image33including the character string “ABCD” as illustrated inFIG. 7by a signal process for allowing each of the characters “A”, “B”, “C”, and “D” to be coincident with each other.

The camera module2acquires depth information of the object by using the MLA14having a compound eye configuration. The digital camera1performs image refocusing by using the depth information of the object. In the case where the digital camera1photographs a moving object, the digital camera1can perform the focus adjustment as a post process by using a refocusing function. The first imaging mode is appropriate for photographing, for example, a moving picture.

The digital camera1can add a blur expression where, for example, background or the like is intentionally allowed to be out of focus to an image by using a refocusing function. The image refocusing process may be a process by a computer or the like which reads the image photographed by the digital camera1instead of the process by the digital camera1.

The camera module2can obtain a focus-matched, high-resolution image at the same time of photographing by using the AF function. The second imaging mode is appropriate for photographing, for example, a still image.

In the first embodiment, the camera module2moves the MLA14to the first position and the second position and controls the position of the MLA14and the focus adjustment according to the imaging mode, so that the refocusing function by the compound eye configuration and the autofocusing function by the autofocusing mechanism can be separately used according to user's intention.

FIG. 8is a schematic cross-sectional diagram illustrating an example of a partial configuration including an imaging optical system and an image sensor of a camera module. A lens holder41holds each lenses constituting the main lens13. An IR cutoff filter42blocks an infrared (IR) light and transmits a visible light.

The image sensor20is installed on a flexible substrate46. The bonding wire44connects electrodes (not illustrated) and the image sensor20in the flexible substrate46. An outer cover43covers portions where the image sensor20is installed in the flexible substrate46, so that a space is formed inside thereof.

The lens holder41is inserted into an opening formed in the outer cover43. The IR cutoff filter42is attached by blocking the opening from an inner side of the outer cover43. In addition, the position of the IR cutoff filter42may be in an optical path from the object to the image sensor20and may be appropriately changed.

An MLA14is attached to a supporting portion48. The supporting portion48is connected to a rotation shaft47erected on the flexible substrate46. The rotation shaft47is rotated by a driving force of a motor16(seeFIG. 2). The rotation shaft47rotates the MLA14for each supporting portion48. The motor16and the rotation shaft47function as a rotation mechanism for moving the MLA14to the first position and the second position by rotating the MLA14.

A stopper49erected on the flexible substrate46is abutted on the MLA14when the MLA14is at the first position. The motor16rotates the rotation shaft47until the MLA14is abutted on the stopper49when the MLA14is allowed to be moved from the second position to the first position.

FIG. 9is a schematic plan diagram illustrating an MLA and peripheral elements in a main lens side in the first imaging mode.FIG. 10is a schematic plan diagram illustrating an MLA and peripheral elements in a main lens side in the second imaging mode. In the figures, the direction of the paper surface is set to a direction of a plane perpendicular to the optical axis of the imaging optical system. The MLA14is configured so that the MLA14can be rotated in the direction of the plane perpendicular to the optical axis with respect to the rotation shaft47as a center of rotation.

In the first imaging mode, the MLA14is abutted on the stopper49, so that the position is fixed. If a command of changing the imaging mode from the first imaging mode to the second imaging mode is received, the MLA14is rotated from the first position on the image sensor20toward the second position. The MLA14is stopped at the second position. When the MLA14is at the second position, the MLA14is detached from the image sensor20.

If a command of changing the imaging mode from the second imaging mode to the first imaging mode is received, the MLA14is rotated from the second position toward the first position. The MLA14is stopped at the first position where the MLA14is abutted on the stopper49.

The MLA14is not limited to the case where the MLA is moved to the first position and the second position by the rotation mechanism. The MLA14may be an MLA which can be moved by any mechanism. The MLA14may be an MLA which is straightly moved to the first position and the second position, for example, by a straight movement mechanism instead of the rotation mechanism.

FIG. 11is a block diagram illustrating a configuration of a lens module, a liquid crystal array, a solid-state imaging device, and an ISP of a camera module according to a second embodiment. The camera module according to the embodiment is applied to an electronic apparatus such as a digital camera1(seeFIG. 1) or a camera-attached mobile terminal. The same elements as those of the first embodiment are denoted by the same reference numerals, and the description thereof is not presented.

The lens module51is configured to include a main lens13and a motor15. The liquid crystal array52is installed at a position in an optical path between the main lens13and the image sensor20, for example, a position on an image forming plane of the main lens13in the first imaging mode. The liquid crystal array52constitutes the second imaging optical system. The liquid crystal array52is configured by arranging a plurality of liquid crystal elements in an array shape. In the liquid crystal element, a light deflection characteristic is allowed to vary with orientation of liquid crystal molecules.

The solid-state imaging device5is configured to include an image sensor20, an imaging process circuit21, an AF driver23, and a liquid crystal driver53. The liquid crystal driver53drives the liquid crystal array52according to the control of the imaging mode control unit26. The imaging mode control unit26controls the driving of the second imaging optical system and the focus adjustment unit in the first imaging mode and the second imaging mode.

FIG. 12is a schematic diagram illustrating a main lens, a liquid crystal array, and an image sensor in the first imaging mode.FIG. 13is a schematic diagram illustrating a main lens, a liquid crystal array, and an image sensor in the second imaging mode.

Liquid crystal elements54constituting a liquid crystal array52are installed corresponding to each of the pixel blocks30(seeFIG. 3). The imaging mode control unit26controls a voltage applied to each of the liquid crystal elements54so as to activate a deflecting function for forming an image piece in the first imaging mode and so as to stop the deflecting function in the second imaging mode.

For example, in the first imaging mode, the liquid crystal driver53continuously applies the voltage to the liquid crystal array52. During the voltage application, the liquid crystal elements54deflect a light beam from the main lens13. In the first imaging mode, the deflecting function of each liquid crystal element54for forming an image piece is activated.

For example, in the second imaging mode, a liquid crystal driver53stops applying of the voltage to the liquid crystal array52. During the stoppage of the voltage application, the liquid crystal element54does not deflect a light beam from the main lens13but allows the light beam to straightly propagate in the direction when the light beam is incident from the main lens13. In the second imaging mode, the deflecting function of each liquid crystal element54for forming an image piece is stopped.

If a command of changing the imaging mode from the second imaging mode to the first imaging mode is received, the imaging mode control unit26controls the liquid crystal driver53so that voltage application to the liquid crystal array52is started. The imaging mode control unit26controls the AF driver23to move the main lens13so that the image forming plane of the main lens13is coincident with, for example, the incidence plane of the liquid crystal elements54. In the first imaging mode, the imaging mode control unit26stops the focus adjustment of the AF driver23.

In the first imaging mode, the imaging mode control unit26allows the liquid crystal array52to function by applying a voltage to the liquid crystal array52and stops the focus adjustment of the AF driver23.

If a command of changing the imaging mode from the first imaging mode to the second imaging mode is received, the imaging mode control unit26controls the liquid crystal driver53so that the voltage application to the liquid crystal array52is stopped. The imaging mode control unit26controls the AF driver23to move the main lens13so that the image forming plane of the main lens13is coincident with the light receiving plane of the image sensor20. In the second imaging mode, the imaging mode control unit26performs the focus adjustment of the AF driver23.

In the second imaging mode, the imaging mode control unit26stops the deflecting function for forming an image piece of the liquid crystal array52and moves the main lens13and performs the focus adjustment of the AF driver23. In addition, with respect to the solid-state imaging device5, when the mode is changed from the first imaging mode to the second imaging mode, the moving of the main lens13may be performed by the focus adjustment of the AF driver23instead of the control of the imaging mode control unit26.

During the stoppage of the voltage application, the liquid crystal element54does not deflect a light beam from the main lens13; but during the voltage application, the liquid crystal element may deflect the light beam from the main lens13. In this case, in the first imaging mode, the liquid crystal driver53stops applying a voltage to the liquid crystal array52; and in the second imaging mode, the liquid crystal driver53continuously applies a voltage to the liquid crystal array52.

In the second embodiment, the camera module2is configured to include the liquid crystal array52, and the voltage applied to the liquid crystal array52and the focus adjustment are controlled according to the imaging mode, so that the refocusing function by the compound-eye configuration and the autofocusing function by the autofocusing mechanism can be separately used according to user's intention.