JP2016174050A - Imaging element, imaging device, control method of the same, program, and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately control a radius of curvature of an imaging surface of an imaging element.SOLUTION: The imaging element includes two-dimensionally arrayed pixels. Only either one of sides of an imaging surface of the imaging element is made to be bendable.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a technique for variably controlling the curvature of an imaging surface of an imaging element.

  In recent years, compact digital cameras have been equipped with one or more large image sensors. As a result, it is possible to shoot with ultra-high sensitivity, which was conventionally possible only with a single-lens reflex camera, or with a compact digital camera, such as shooting with a shallow subject depth and vivid blur.

  As described above, when a large image sensor is mounted on a compact digital camera, the lens tends to increase in size, and thus it is necessary to reduce the size of the lens. However, when trying to reduce the size of the lens while maintaining equivalent performance, there is a problem that the incident angle of light incident on the lens from the subject (hereinafter referred to as light incident angle) increases.

  As means for solving such a problem, Patent Document 1 proposes an imaging element having a structure in which an imaging surface is curved in order to correct lens aberration. Japanese Patent Application Laid-Open No. 2004-228561 proposes an imaging apparatus in which the curvature of the imaging surface of the imaging element is set according to the image field aberration of the lens, and the curvature is variably controlled between the tele side and the wide side during zooming. .

Japanese Patent No. 4604307 JP 2012-182194 A

  In order to variably control the curvature of the imaging surface of the imaging element, for example, negative pressure is used. FIG. 7 is a schematic diagram of a configuration of a curvature control mechanism that controls the curvature of the imaging surface of the imaging element.

  As shown in FIG. 7, the image sensor 700 includes a semiconductor pixel chip portion 701 having a curved portion 702, a base 703 having a flat portion 704 and an opening 705, a bottom plate 706, and a suction portion 707. The pixel chip portion 701 is supported by a flat portion 704 on the surface side of the base 703. The bottom plate 706 is provided so as to close the opening 705 on the back surface side of the base 703. The suction part 707 is attached at a position corresponding to the opening 705 in the bottom plate 706.

  The pixel chip unit 701 has an imaging region (imaging surface) in which unit pixels are two-dimensionally arranged in the central part, and has a circuit part in the peripheral part.

  Then, the suction unit 707 sucks the gas inside the opening 705 made airtight by the bottom plate 706 and controls the pressure (negative pressure) inside the opening 705 to variably control the curvature of the bending part 702. Is configured to do.

  As described above, the mechanism for variably controlling the curvature of the imaging surface of the image sensor is very complicated. Further, since the bending portion is deformed in a non-contact manner, it is very difficult to accurately control the curvature.

  The present invention has been made in view of the above problems, and an object thereof is to realize a technique capable of controlling the curvature of the imaging surface of the imaging element with high accuracy.

  In order to solve the above-described problems and achieve the object, the imaging device of the present invention is an imaging device in which pixels are arranged two-dimensionally, and only one side direction of the imaging surface of the imaging device is bent and deformed. It was possible.

  According to the present invention, the curvature of the imaging surface of the imaging device can be controlled with high accuracy.

1 is a block diagram illustrating a configuration of an imaging apparatus according to an embodiment. FIG. 3 is a circuit diagram showing an electrical configuration of the image sensor of the present embodiment. FIG. 3 is a diagram illustrating a part of a color filter array of an image sensor according to the present embodiment. The figure explaining the structure of an image pick-up element and a curvature control part. The figure which shows the curvature control table used for the curvature control process of this embodiment. 6 is a flowchart showing curvature control processing of the imaging surface of the imaging device according to the present embodiment. The figure explaining the structure of the conventional curvature control part.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention with reference to an accompanying drawing is demonstrated in detail. The embodiment described below is an example for realizing the present invention, and should be appropriately modified or changed according to the configuration and various conditions of the apparatus to which the present invention is applied. It is not limited to the embodiment. Moreover, you may comprise combining suitably one part of each embodiment mentioned later.

  Hereinafter, embodiments in which the present invention is applied to an imaging apparatus such as a compact digital camera will be described. The present invention can also be applied to other devices having a function capable of variably controlling the curvature of the imaging surface of the imaging element.

  <Apparatus Configuration> With reference to FIG. 1, an outline of a configuration and functions of an imaging apparatus according to an embodiment of the present invention will be described.

  In FIG. 1, an image pickup apparatus 100 according to the present embodiment is equipped with a one-type or larger large image pickup element.

  The lens 101 includes a focus lens and a zoom lens.

  The lens control unit 102 performs drive control of the lens 101 based on a control signal from the main control unit 111. For example, during zooming, the lens control unit 102 performs zoom control to move the lens 101 to a position corresponding to a predetermined zoom magnification between the tele end and the wide end in accordance with a user's zoom operation.

  The shutter 103 is a mechanical shutter that is mechanically driven to adjust the irradiation time of the subject image light formed on the imaging surface of the image sensor 106.

  The diaphragm 104 adjusts the amount of light of the subject image formed on the imaging surface of the image sensor 106, and includes diaphragm blades whose aperture diameter is variable by being mechanically driven.

  The shutter / aperture control unit 105 performs drive control of the shutter 103 and the aperture 104 based on a control signal from the main control unit 111.

  The image sensor 106 is configured by a CCD, a CMOS, or the like that converts a subject image formed through an optical system including a lens 101, a diaphragm 104, and a shutter 103 into an electrical signal. The detailed configuration of the image sensor 106 will be described later with reference to FIGS.

  The curvature control unit 118 is provided in the image sensor 106 as will be described later with reference to FIGS. 4 to 6, and performs variable control of the curvature of the imaging surface of the image sensor 106 based on a control signal from the main control unit 111.

  A timing generator (TG) 109 generates a timing signal for driving the image sensor 106 based on a control signal from the main controller 111, and supplies the timing signal to the image sensor 106, the CDS / A / D converter 107, and the signal processor 108. Output.

  The CDS / A / D converter 107 performs correlated double sampling, gain adjustment, and conversion from an analog signal to a digital signal for the analog signal output from the image sensor 106. As R, G, and B signals, The signal is output to the signal processing unit 108. Here, the image sensor 106 and the CDS / A / D converter 107 have been described as separate components, but the CDS / A / D converter 107 is integrated into the image sensor 106 so as to be integrated. It doesn't matter. Alternatively, an imaging element 106 in which an imaging chip and an image processing chip are stacked may be used.

  The signal processing unit 108 performs signal processing such as color conversion processing and gamma correction processing on the digital signal output from the CDS / A / D conversion unit 107, and performs compression processing to generate image data. The signal processing unit 108 outputs image data to the image memory 110 and the recording medium 114, and performs predetermined signal processing on the image data read from the image memory 110 and the recording medium 114. Further, the signal processing unit 108 has a function of detecting photometric data such as an in-focus state and an exposure amount from the output signal of the image sensor 106 and outputting the photometric data to the main control unit 111.

  The image memory 110 temporarily stores the image data output from the signal processing unit 108.

  For example, an LCD or an organic EL is used as the display unit 113. In addition to displaying an image, a display for assisting operation, and a camera state display, the display unit 113 displays a shooting screen and a distance measurement area.

  The external connection unit 115 is an interface for communicating with an external device such as a personal computer (PC) to exchange data.

  The recording medium connection unit 112 is an interface for reading and writing image data with respect to the recording medium 114.

  In the recording medium 114, image data (still image, moving image) output from the signal processing unit 108 is recorded. The recording medium 114 may be a memory card or a hard disk drive mounted on the imaging device 100, or a flash memory or a hard disk drive built in the imaging device 100. Note that a memory unit 116 and a recording medium 114, which will be described later, may have the same configuration.

  The memory unit 116 stores constants, programs, setting information, and the like for the operation of the CPU of the main control unit 111. Here, the program is a program for executing a variable control sequence of the curvature of the imaging surface of the imaging device described later in the present embodiment.

  The main control unit 111 includes a CPU, a main memory (RAM), an input / output circuit, a timer circuit, and the like. The CPU expands the program stored in the memory unit 116 in the work area of the RAM, and executes the program. Control overall operation. Note that the main memory and the image memory 110 may have the same configuration.

  The operation unit 117 is an operation unit that receives a user operation for inputting various instructions to the imaging apparatus 100, and various forms such as a physical operation member such as a button or a switch or an input unit through a touch panel can be used. It is. The operation unit 117 includes, for example, a menu switch for performing various settings at the time of image shooting and playback, a zoom lever for instructing a zoom operation of the lens 101, a switch for operation modes such as a shooting mode and a playback mode, a shutter switch, a power switch Includes switches. The main control unit 111 controls the imaging apparatus 100 based on an instruction or setting input by the user via the operation unit 117 and displays setting information, an operation state, an image, and the like on the display unit 113.

  <Image Sensor> Next, the detailed configuration of the image sensor 106 of the present embodiment will be described with reference to FIGS.

  FIG. 2 is a circuit diagram showing an electrical configuration of the image sensor 106 of the present embodiment. In FIG. 2, for simplification of explanation, only the unit pixels 201 are shown as 4 rows × 4 columns, but in reality, a large number of unit pixels 201 are two-dimensionally arranged.

  In FIG. 2, a unit pixel 201 includes a photodiode (PD) 202, a transfer switch 203, a floating diffusion (FD) 204, an amplification MOS amplifier 205 that functions as a source follower, a selection switch 206, and a reset switch 207. Light is converted into electric charge in the PD 202, and the electric charge generated in the PD 202 is transferred from the PD 202 to the FD 204 by applying the transfer signal φTX to the transfer switch 203 and temporarily stored in the FD 204. A floating diffusion amplifier is configured by the FD 204, the amplification MOS amplifier 205, and the constant current source 209 serving as a load of the amplification MOS amplifier 205. Then, by applying the selection signal φSEL, the selection switch 206 is turned on, the signal charge accumulated in the FD 204 of the selected pixel is converted into a voltage, and is output to the readout circuit 213 via the signal output line 208. . Further, a signal output from the readout circuit 213 is selected by outputting a selection signal through the selection signal line 210 by the horizontal scanning circuit 214, and the selected pixel signal is output to the outside of the image sensor 106 via the output amplifier 211. The The charge accumulated in the FD 204 is removed by applying a reset signal φRES to the set switch 207. The vertical scanning circuit 212 performs driving to selectively turn on / off the transfer switch 203, the selection switch 206, and the reset switch 207.

  FIG. 3 illustrates a part of the color filter array used in the image sensor 106 shown in FIG.

  In FIG. 3, the first color filter is red (R), the second color filter is green (G), the third color filter is green (G), and the fourth color filter is blue (B). Is shown. This array of color filter arrays is called a Bayer array among the primary color filter arrays, and is a color filter array having high resolution and excellent color reproducibility.

  <Curvature Control Unit> Next, the configuration and functions of the curvature control unit 118 of this embodiment will be described with reference to FIG. FIG. 4A to FIG. 4D are diagrams showing the configuration of the image sensor 106 shown in FIG.

  FIG. 4A is a plan view of the image sensor 106 as viewed from the imaging surface direction. The image sensor 106 is formed so that at least its imaging surface has a rectangular (quadrangle) shape.

  The effective pixel unit 401 has a pixel array in which a plurality of unit pixels 201 shown in FIG. 2 are arranged in a two-dimensional direction of a horizontal direction (row direction) H and a vertical direction (column direction) V as shown in the figure. .

  An area 403 along the row direction H that is the long side direction (longitudinal direction) of the imaging surface of the imaging element 106 including the effective pixel unit 401 is imaged according to the light incident angle of the lens 101 by a plurality of expansion and contraction units 417 described later. It is configured to be capable of bending deformation so as to obtain characteristics. By bending and deforming the region 403 so as to protrude downward about the axis passing through the center of the effective pixel portion 401 and parallel to the column direction V (vertical direction with respect to the paper surface), the effective pixel portion 401 has a row in the longitudinal direction. Curve in direction H. Note that the light incident angle of the lens 101 varies depending on the zoom state of the lens 101, and the angle increases toward the periphery of the image circle.

  On the other hand, the region 402 along the column direction V, which is the short side direction (short direction) of the image pickup surface of the image pickup element 106 including the effective pixel unit 401, is configured not to be bent and deformed as described later. The region 402 is fixed to the flat portion 414 of the pedestal as will be described later. Since the region 402 is fixed to the flat portion 414 of the pedestal, the effective pixel portion 401 cannot be bent in the column direction V. Note that the change in the imaging characteristics according to the light incident angle of the lens 101 is dealt with by performing correction by image processing.

  In any zoom state, the lens 101 has a certain light incident angle. Therefore, in order to maintain good imaging characteristics, the microlens (not shown) arranged in each unit pixel 201 is configured to shift in the column direction V as the distance from the center of the effective pixel unit 401 increases.

  4B, 4C, and 4D respectively show the cross-sectional structures of H1-H1 ', H2-H2', and H3-H3 'of FIG.

  4B and 4D, the image sensor 106 includes a semiconductor pixel chip portion 411 having a curved portion 412, a pedestal 413 having a flat portion 414 and an opening 415, a bottom plate 416, and a plurality of extendable portions 417. Is provided. The pixel chip portion 411 is supported by the flat portion 414 on the surface side of the base 413. The bottom plate 416 is provided so as to close the opening 415 on the back surface side of the pedestal 413. The stretchable part 417 is connected to the back surface of the curved part 412 and the bottom plate 416 inside the opening 415.

  The pixel chip unit 411 has an imaging region (imaging surface) in which unit pixels 201 are two-dimensionally arranged in the central portion, and has the circuit units 209 to 215 in FIG. 2 in the peripheral portion. The pixel chip portion 411 forms a curved portion 412 that is curved in an arc shape so that the long side direction (longitudinal direction) of the imaging region is convex downward with the opening 415 of the base 413. Then, by fixing the flat portion corresponding to the peripheral region 402 of the curved portion 412 in the short side direction (short direction) of the imaging region to the flat portion 414 of the pedestal 413 via the adhesive layer, the pixel chip portion 411 is supported by a pedestal 413.

  Between the bottom plate 416 and the pixel chip unit 411 in the opening 415, a plurality of expansion / contraction units 417 controlled by the curvature control unit 118 are attached. As each expansion / contraction part 417, a piezoelectric element is used, for example, and each expansion / contraction part 417 can expand / contract to a desired length by current control by the curvature control unit 118. And it is comprised so that the curvature (curvature) of the bending part 412 can be variably controlled as shown with the dotted line in a figure.

  4 (b) and 4 (d), as shown in FIGS. 4 (a) and 4 (c), the expansion / contraction portion 417 is not provided in the region where the effective pixel portion 401 is located in the opening 415. . This is to prevent a movable element such as the expansion / contraction section 417 from contacting the effective pixel section 401 and adversely affecting the imaging characteristics.

  Note that the curved shape can be reproduced with very high accuracy by controlling the curvature (curvature) of the bending portion 412 by bringing the expansion / contraction portion 417 into direct contact with the edge of the pixel chip portion 411 as shown in the figure.

  Note that, as a method of changing the curvature of the curved portion 412, in addition to the method using the piezoelectric element as described above, a method of controlling the negative pressure inside the opening 415, or a magnetism on the back side of the pixel chip portion 411 is used. A method of making the curvature variable by forming a film and controlling the magnetic force generated by a magnet or electromagnetic coil is applicable.

  <Curvature Control Table> Next, with reference to FIG. 5, a curvature control table used for curvature control of the imaging surface of the image sensor 106 of this embodiment will be described.

  5A is a curvature control table in which the zoom position of the lens 101 and the curvature control value C used for the curvature control of the imaging surface of the image sensor 106 are associated, and FIG. 5B is the curvature control value of the bending portion 412. The relationship between C, the zoom position, and the curved shape is shown. The memory unit 116 of the imaging apparatus 100 according to the present embodiment stores a curvature control table as illustrated in FIG. The curvature control unit 118 uses the curvature control value C to control the imaging surface of the imaging element 106 to have a curvature corresponding to the zoom position of the lens 101. The curvature control value C set in the curvature control table is obtained by conducting an experiment or the like in advance on the image sensor 106 so as to obtain an appropriate curvature for each zoom position.

  In the example shown in FIG. 5B, the curvature decreases as the zoom position approaches the tele side (the shape of the curved portion 412 approaches flat), and the curvature increases as the zoom position approaches the wide side (the curvature of the curved portion 412 increases). The curvature control value C is set so as to increase. Note that the lens 101 of the present embodiment is configured such that the light incident angle on the imaging surface of the imaging element 106 increases as the zoom position is closer to the wide side during image capture or live view.

  In the curvature control table of FIG. 5A, zoom points such as Wide and M1 are used as zoom positions, but focal lengths at the respective zoom positions may be used.

  By using such a curvature control table, the curvature of the imaging surface of the image sensor 106 is controlled so that the imaging characteristics are optimally maintained with respect to the light incident angle of the lens 101 that changes according to the zoom position during zooming. be able to.

  <Variable Control of Curvature of Imaging Surface of Imaging Device> Next, a variable control sequence of the curvature of the imaging surface of the imaging device 106 by the imaging apparatus 100 of the present embodiment will be described with reference to FIG.

  The process shown in FIG. 6 is started when the imaging apparatus 100 is in the shooting mode, and the main control unit 111 and the curvature control unit 118 are executed in cooperation. Note that the CPU of the main control unit 111 realizes the processing of FIG. 6 by developing the program read from the memory unit 116 in the main memory and executing it.

  When a shooting operation start instruction is input via the operation unit 117, the main control unit 111 performs initial setting of various conditions such as control parameters related to the shooting sequence in step S601.

  In step S <b> 602, the main control unit 111 acquires information related to the zoom position of the lens 101 set by operating the zoom lever or the like of the operation unit 117.

  In step S603, the main control unit 111 generates a control value C for setting the curvature corresponding to the zoom position information acquired in step S602 with reference to the curvature control table of FIG. To part 118.

  In step S604, the curvature control unit 118 performs current control of the expansion / contraction unit 417 based on the control value C given in step SS603. Then, the bending portion 412 of the pixel chip portion 411 in the image sensor 106 is bent and deformed, and is controlled so as to have a desired curvature.

  In step S605, the main control unit 111 determines whether a shooting end instruction has been input via the operation unit 117, and ends the process if input. If not input, the process returns to step S602, and curvature control according to the acquired zoom position information is repeatedly executed.

  As described above, according to the present embodiment, the curvature of the imaging surface of the imaging element 106 is controlled with high accuracy by adopting a structure in which only the long side direction (longitudinal direction) of the imaging surface of the imaging element 106 is bent and deformed. An imaging device that can be realized.

  In addition, as in the present embodiment, by controlling the curvature by directly contacting the expansion / contraction part 417 with the edge part of the pixel chip part 411, an imaging apparatus capable of reproducing the curved shape with high accuracy can be realized.

  In this embodiment, the example in which only the long side direction (longitudinal direction) of the imaging surface of the image sensor 106 can be bent and deformed has been described. However, the long side direction (longitudinal direction) and the short side of the imaging surface of the image sensor 106 are short. Only one of the side directions (short direction) may be bent and deformed, and the curvature thereof may be variably controlled.

[Other Embodiments]
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in the computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

DESCRIPTION OF SYMBOLS 100 ... Imaging device, 101 ... Lens, 106 ... Imaging element, 108 ... Signal processing part, 111 ... Main control part, 118 ... Curvature control part, 417 ... Expansion / contraction part

Claims (12)

An image sensor in which pixels are arranged two-dimensionally,
An imaging device, wherein only one side direction of the imaging surface of the imaging device can be bent and deformed.   The imaging device according to claim 1, wherein only the long side direction of the imaging surface of the imaging device can be bent and deformed.   The imaging device according to claim 2, further comprising a curvature control unit that expands and contracts in a state in which the imaging device is in direct contact with an edge portion in the long side direction of the imaging surface.   The imaging device according to claim 3, wherein the curvature control unit is provided at a position excluding an effective pixel unit on an imaging surface of the imaging device.   The imaging device according to claim 3, wherein the curvature control unit includes a plurality of piezoelectric elements. The imaging device according to any one of claims 1 to 5,
An image pickup apparatus comprising: control means for variably controlling the curvature of the image pickup surface of the image pickup element during zooming. Zoom means for performing a zoom operation in response to a user operation;
The image pickup apparatus according to claim 6, wherein the control unit variably controls a curvature of an image pickup surface of the image pickup element according to a zoom position.   The imaging apparatus according to claim 7, further comprising a table in which a curvature control value for the control unit to variably control the curvature is stored for each zoom position.   The imaging apparatus according to claim 8, wherein the curvature is smaller as the zoom position is closer to a tele side and larger as the zoom position is closer to a wide side. A method for controlling an imaging apparatus having an imaging element in which only one side direction of an imaging surface of the imaging element is bendable,
An acquisition means for acquiring information of a zoom position during zooming; and
And a step of variably controlling the curvature of the imaging surface in accordance with the zoom position information.   The program for functioning a computer as each means of the imaging device described in any one of Claims 6 thru | or 9.   A computer-readable storage medium storing a program for causing a computer to function as each unit of the imaging apparatus according to any one of claims 6 to 9.

Images