JP2010124406A - Imaging device and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging device and an electronic apparatus which can photograph a planar subject such as a document by a simple and space-saved constitution. <P>SOLUTION: Since an optical driver 105 is driven so that a position F between a position O and a position Q becomes a focused position of an imaging optical system 101, a letter or the like on a document DCM located at a side far from an imaging device CA (in the vicinity of the position Q) comes closer to the focused position of the imaging system 101, thereby enabling high-resolution photographing as shown by an MTF curve in Fig.3. A letter or the like at the side of the document DCM closer to the imaging device CA (in the vicinity of a position P) may become out of a focus because it is located away from the focused position. In many cases, however, such a letter is photographed with a high resolution owing to the depth of a field as shown by the MTF curve in Fig.3. Even if the letter is partly out of a focus, its viewing angle is large, so that it can be read easily. Therefore, the subject can be wholly photographed suitably. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging apparatus and an electronic apparatus using a solid-state imaging device such as a CCD (Charge Coupled Devices) type image sensor or a CMOS (Complementary Metal-Oxide Semiconductor) type image sensor.

  In recent years, video cameras and digital cameras equipped with an imaging device using a solid-state imaging device such as a CCD type image sensor or a CMOS type image sensor have become widespread, and a solid having a high number of pixels so that a higher quality image can be obtained. A device equipped with an image pickup device using an image pickup element has been supplied to the market. In addition, with the spread of the Internet, so-called web cameras or the like that are attached to a personal computer to acquire a sender's image and transmit it to the other party are already on the market.

  By the way, there is an increasing need for digitizing documents for information security or remote communication using handwritten documents. There is a scanner as an apparatus conventionally used for digitizing a document. However, the scanner captures an image plane that faces the imaging optical system, and a large-sized scanner device equipped with a line sensor is often used particularly when a document containing characters is digitized on a desktop. However, there is a problem that the device itself is relatively bulky. On the other hand, a digital camera may be used instead of a scanner, but in this case, it is necessary to shoot with the image plane and the digital camera facing each other at a certain distance. There is a problem that it has to be placed on the floor or the like to take an image and is not easy to use.

On the other hand, if a paper document can be digitized using a web camera built in or externally attached to a notebook personal computer or the like, there is an advantage that it can be effectively used on a desktop at low cost. However, the web camera is supposed to be used for video conferencing, and it is assumed that the image plane of the subject faces directly. Therefore, when a document placed on the table is photographed, the closest position and the farthest position There is a problem that a distance difference is large and an image of an appropriate document cannot be obtained.
JP 2007-324655 A

  On the other hand, Patent Document 1 discloses a technique for correcting image distortion by image processing after a document is imaged obliquely from above with a digital camera mounted on a personal computer. However, although image distortion can be corrected to some extent by image processing, if characters on a document are taken out of focus, it will no longer be possible to interpret the characters from the acquired image. There's a problem.

  The present invention has been made in view of such problems, and an object thereof is to provide an imaging apparatus and an electronic apparatus that can capture a planar subject such as a document while having a simple and space-saving configuration. To do.

An imaging apparatus according to claim 1 is provided.
An image sensor;
An imaging optical system capable of adjusting a focal position and forming an optical image on a light receiving surface of the imaging element;
An in-focus position control means for controlling an in-focus position of the imaging optical system, and an imaging apparatus that captures an image of a subject that is inclined with respect to the optical axis of the imaging optical system and is roughly defined by a plane,
The focusing position control means controls the imaging optical system so that the focusing position is farther from the optical axis center position during imaging.

  For example, if you try to shoot a document placed on a desktop in front of the keyboard with a webcam placed on a laptop computer monitor, the characters on the document near the webcam will have a larger angle of view. The character on the document farther from the web camera has a smaller angle of view. Therefore, when the in-focus position of the image pickup optical system is below the center of the document, there is a possibility that reading becomes impossible when the farthest character is picked up.

  On the other hand, according to the present invention, the focusing position control means controls the imaging optical system so that the focusing position is farther from the optical axis center position during imaging. Since the character farthest away from the image pickup device is close to the in-focus position of the image pickup optical system, it is possible to pick up an image with high resolution. On the other hand, characters on the side of the document that are close to the imaging device are far from the in-focus position, so there is a risk of being out of focus. Even if there are some characters, it is easy to read because the angle of view is large. Therefore, good imaging can be performed for the entire subject.

  According to a second aspect of the present invention, in the invention of the first aspect, the in-focus position control unit automatically obtains the in-focus position so that the in-focus position is farther from the optical axis center position. This is convenient because it controls the imaging optical system. However, the in-focus position may be determined manually by the user's intention.

  According to a third aspect of the present invention, in the invention of the second aspect, the in-focus position control means processes the signal of the image sensor that forms an optical image on the light receiving surface, thereby focusing. Since the position is detected, there is no need to separately provide a distance measuring device, and the cost can be reduced.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the in-focus position control unit processes a signal of the imaging element that forms an optical image on the light receiving surface. Thus, the outline of the subject is extracted, and the imaging optical system is controlled so that the in-focus position is farther from the optical axis center position within the range of the extracted outline of the subject. Therefore, the in-focus position can be determined with high accuracy.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the in-focus position control unit processes a signal of the imaging element that forms an optical image on the light receiving surface. Thus, the contour of the subject is extracted, and the contour of the subject is divided into a plurality of parts according to the in-focus distance, and the subject is obtained by combining the divided images. Therefore, a clearer image can be obtained.

  According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the first imaging mode for imaging a subject extending in a substantially vertical direction and the subject extending in a substantially horizontal direction. The second imaging mode for imaging can be set, and when the second imaging mode is selected, the focusing position control means sets the focusing position farther from the optical axis center position during imaging. Since the imaging optical system is controlled so as to become, it is user-friendly because it automatically enters a state suitable for imaging a document or the like.

  According to a seventh aspect of the present invention, there is provided the imaging apparatus according to the sixth aspect, further comprising a sensor that detects a direction of an optical axis of the imaging optical system, and the optical axis of the imaging optical system is in a horizontal direction. When it is detected that the camera is directed upward, the first imaging mode is selected, and when it is detected that the optical axis of the imaging optical system is directed downward from the horizontal direction, the second imaging mode is selected. Since the imaging mode is selected, it is user-friendly because it automatically enters a state suitable for imaging a document or the like.

  An electronic apparatus according to an eighth aspect includes the imaging device according to any one of the first to seventh aspects. As electronic devices, there are various devices such as personal computers (including notebook computers), mobile phones, and PDAs.

  An electronic apparatus according to a ninth aspect is the electronic device according to the eighth aspect, wherein a monitor that displays an image of the subject based on a signal of the imaging element that forms an optical image on the light receiving surface is the imaging device. It has in the front side of an apparatus, It is characterized by the above-mentioned.

  An electronic device according to a tenth aspect is the electronic device according to the eighth or ninth aspect, wherein the sub-monitor that displays an image of the subject based on a signal of the imaging element that forms an optical image on the light receiving surface, It is provided on the back side of the imaging device.

  The electronic device according to claim 11 is the imaging device according to any one of claims 8 to 10, wherein the electronic device has a keyboard for inputting information, and an optical image is formed on the light receiving surface. A sub-monitor for displaying an image of the subject on the basis of an element signal is provided on the keyboard.

  According to the present invention, it is possible to provide an imaging apparatus and an electronic apparatus that can capture a planar subject such as a document while having a simple and space-saving configuration.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a notebook personal computer PC equipped with an imaging apparatus CA according to the present embodiment. FIG. 2 is a block diagram of a notebook personal computer PC equipped with the imaging apparatus CA according to the present embodiment. FIG. 3 is a side view of a state in which an A4 document DCM in which characters and pictures are drawn is arranged in the vicinity of the notebook personal computer PC. The MTF (object field) of the subject distance corresponding to the document DCM is shown in FIG. It is shown with the (depth) curve. In the MTF curve, the resolution increases as the value on the vertical axis increases.

  As shown in FIG. 1, the notebook personal computer PC has a main body PCB and a display unit PCD connected by a hinge PCH so that it can be folded, and the imaging device CA is provided above the center of the monitor 112 in the display unit PCD. That is, the monitor 112 is on the front side of the imaging device CA. In addition, since the image pickup apparatus CA is built in the notebook type personal computer PC, an image processing circuit on the personal computer side can be used, so that the configuration can be simplified. Further, since the display unit PCD can be used as a support unit of the imaging apparatus CA, there is an advantage that a certain angle of view can be secured when the document DCM is captured.

  In FIG. 2, the imaging apparatus CA includes an imaging optical system 101, a solid-state imaging device 102, and an A / D conversion unit 103. On the other hand, the notebook personal computer PC includes a control unit 104, an optical system driving unit 105, a timing generation unit 106, an image sensor driving unit 107, an image memory 108, an image processing unit 109, an image compression unit 110, The image recording unit 111, the monitor 112, and the keyboard 113 are included. In addition, a device used for a normal personal computer is provided, but the description is omitted here. Imaging device CA is preferably tiltable with respect to notebook personal computer PC.

  The imaging optical system 101 has a function of forming a subject image on the imaging surface (light receiving surface) of the solid-state imaging device 102. The solid-state image sensor 102 is an image sensor such as a CCD or CMOS, and photoelectrically converts incident light for each of R, G, and B and outputs an analog signal thereof. The A / D conversion unit 103 converts an analog signal into digital image data.

  The control unit 104 has a function of controlling the imaging device CA. The control unit 104 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory), and various programs read out from the ROM and expanded in the RAM, and various in cooperation with the CPU. Execute the process.

  The optical system drive unit 105 controls the drive of the imaging optical system 101 during focusing, exposure, and the like under the control of the control unit 104. The optical system driving unit 105 and the control unit 104 constitute a focusing position control unit. The timing generator 106 outputs a timing signal for analog signal output. The image sensor drive unit 107 performs scanning drive control of the solid-state image sensor 102.

  The image memory 108 stores image data so as to be readable and writable. The image processing unit 109 performs various image processes on the image data. The image compression unit 110 compresses captured image data by a compression method such as JPEG (Joint Photographic Experts Group). The image recording unit 111 records image data on a recording medium such as a memory card set in a slot (not shown).

  The monitor 112 is a color liquid crystal panel or the like, and can display image data after shooting, a through image before shooting, and the like. The keyboard 113 includes a mode setting command and various operation keys for inputting information, and outputs information input by the user to the control unit 104.

  Here, operations in the imaging apparatus CA and the notebook personal computer PC will be described. The user can use the keyboard 113 to capture a first imaging mode in which the user (subject extending approximately in the vertical direction) can be captured, and a second imaging mode in which the document DCM (subject extending approximately in the horizontal direction) can be captured. You can select either of these.

  First, a case where the first imaging mode is set will be described. In the first imaging mode, subject monitoring (through image display) and image shooting execution are performed as necessary. In monitoring, an image of a subject obtained through the imaging optical system 101 is formed on the light receiving surface of the solid-state imaging device 102. As a photoelectric conversion output corresponding to an optical image formed at fixed intervals, the solid-state imaging device 102 disposed behind the imaging optical axis of the imaging optical system 101 is scanned and driven by the timing generation unit 106 and the imaging device driving unit 107. The analog signal is output for one screen.

  The analog signal is appropriately gain-adjusted for each primary color component of RGB, and then converted into digital data by the A / D conversion unit 103. The digital data is subjected to color process processing including pixel interpolation processing and γ correction processing by the image processing unit 109 to generate a luminance signal Y and color difference signals Cb, Cr (image data) as digital values, and the image memory. 108, the signal is periodically read out, the video signal is generated, output to the monitor 112, and transmitted to the other party connected via the Internet.

  The monitor 112 functions as an electronic viewfinder in monitoring, and displays captured images in real time. In this state, focusing, exposure, and the like of the imaging optical system 101 are set by the drive of the optical system driving unit 105 as needed by the image plane AF.

  In such a monitoring state, the user can acquire still image data by operating a predetermined key on the keyboard 113 at a timing when still image shooting is desired. In response to such a key operation, one frame of image data stored in the image memory 108 is read out and compressed by the image compression unit 110. The compressed image data is recorded on a recording medium by the image recording unit 111.

  Next, a case where the second imaging mode is set will be described. Also in the second imaging mode, subject monitoring (through image display) and image capturing execution are performed as described above. Here, the imaging device CA itself may be tilted forward while visually recognizing the image displayed on the monitor 112 so that the document DCM is easily captured, or the monitor 112 and the imaging device CA are tilted together. May be. In this state, the center of the optical axis of the imaging optical system 101 is located on the document DCM placed on the table. This position is O (see FIG. 3).

  First, during the monitoring, the control unit 104 detects the outline FR (FIG. 1) of the document DCM placed on the table within the range of the shooting angle of view based on the signal from the solid-state image sensor 102. The detection of the contour is known in the art using edge enhancement and the like, and will not be described. If the document to be imaged is limited to A4 or the like, the contour can be estimated from the standard size and the place (adjacent to the keyboard). Since the image is captured and recorded as a trapezoidally distorted image for photographing in an oblique direction, correction is necessary. However, it is also possible to correct the trapezoid using the estimated contour information.

  Next, referring to FIG. 3, the optical axis center position O (that is, the screen center) of the imaging optical system 101 and the position Q of the farthest contour FR from the imaging device CA are obtained from the detected contour FR of the document DCM. Then, the optical system driving unit 105 is driven so that the center position F is set as the in-focus position of the imaging optical system 101. Focusing is preferably performed automatically by the image plane AF as described above, but a distance measuring device may be provided separately. The in-focus position F is not the center between the position O and the position Q, and may be any position between the position O and the position Q. Here, if the position of the contour FR closest to the imaging device CA is P, the distance PO <distance PF <distance PQ is established. However, in order to effectively use the imaging angle of view and obtain a high-quality image, it is desirable that distance PO> distance OQ.

  In this state, the user can acquire still image data by operating a predetermined key on the keyboard 113. In response to such a key operation, one frame of image data stored in the image memory 108 is read out and compressed by the image compression unit 110. The compressed image data is recorded on a recording medium by the image recording unit 111. At this time, for example, since the document DCM of A4 is captured in a trapezoidal shape, image processing may be performed so that the lateral width of the image on the far side of the imaging device CA is increased according to the distance.

  According to the present embodiment, the optical system driving unit 105 is driven so that the position F between the position O and the position Q is set to the in-focus position of the imaging optical system 101. Therefore, the imaging apparatus CA is displayed on the document DCM. Since characters on the far side (near the position Q) from the image are close to the in-focus position of the imaging optical system 101, it is possible to capture with high resolution as shown by the MTF curve in FIG. On the other hand, characters on the document DCM that are close to the image pickup apparatus CA (near position P) are far from the in-focus position, so there is a risk of being out of focus, but in many cases, as shown by the MTF curve in FIG. Even if some characters are taken with high resolution and are out of focus with the help of the depth of field, reading is easy because the image on the imaging surface is large. Therefore, good imaging can be performed for the entire subject.

  Note that when the contour FR of the document DCM placed on the table is extracted based on the signal from the solid-state image sensor 102, the control unit 104 extracts a plurality of contours FR (for example, FIG. 3 is divided into a region between the position P and the position O, and a region between the position O and the position Q), and the divided images are combined by image processing. You may acquire the whole image of DCM.

  FIG. 4 is a diagram illustrating a notebook personal computer according to a modification. In the present embodiment, the imaging apparatus CA or the notebook personal computer PC is provided with an acceleration sensor SS so that the direction of the optical axis of the imaging optical system 101 with respect to the direction of gravity can be detected. In the embodiment described above, the user can select either the first imaging mode or the second imaging mode, but in the present embodiment, it can be automatically selected.

  More specifically, when the sensor SS detects that the optical axis of the imaging optical system 101 is directed upward from the horizontal direction, the control unit 104 indicates that the monitor 112 is displayed as indicated by a dotted line in FIG. Since the position is directly opposite to the user, it is determined that there is an intention to image itself, and the first imaging mode is selected. On the other hand, when it is detected that the optical axis of the imaging optical system 101 is directed downward from the horizontal direction, the control unit 104 indicates that the imaging apparatus CA is facing the document DCM as indicated by a solid line in FIG. It is determined that the user intends to image the document DCM, and the second imaging mode is selected. This saves the user trouble in mode selection.

  FIG. 5 is a diagram illustrating an imaging apparatus CA according to still another modification. Although not shown, the imaging device CA is connected to an electronic device such as a notebook computer. The imaging device CA does not need to be built in the notebook personal computer PC, and may be supported and used by the support PL as shown in FIG. 5, or a desktop personal computer (not shown) as shown in FIG. It may be provided and used at the upper center of the display unit MNT of the monitor device connected to the. In the embodiment shown in FIGS. 4 and 6, the image pickup apparatus CA is arranged at the upper center of the display. However, the arrangement is not limited to this. The arrangement of the image pickup apparatus CA is arranged next to the display unit in consideration of design and wiring distance. It can also be on the bottom, back side. Alternatively, it may be a type that is externally attached to a display unit of a personal computer with a clip or the like.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate. For example, as shown in FIG. 1, a sub monitor 112b for displaying an image of a subject may be provided in the vicinity of the keyboard 113 of the notebook personal computer PC, or the sub monitor 112a indicated by a dotted line may be provided on the display of the notebook personal computer PC. You may provide in the back side of the part PCD. Thereby, even if the display unit PCD is tilted toward the document DCM, the displayed image can be visually recognized.

It is a perspective view of notebook type personal computer PC carrying imaging device CA concerning this embodiment. It is a block diagram of notebook type personal computer PC which mounts imaging device CA concerning this embodiment. It is the figure seen from the side in the state which has arrange | positioned document DCM in the vicinity of notebook type personal computer PC. It is a figure which shows the notebook personal computer concerning a modification. It is a figure which shows imaging device CA concerning another modification. It is a figure which shows imaging device CA concerning another modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Imaging optical system 102 Solid-state image sensor 103 Conversion part 104 Control part 105 Optical system drive part 106 Timing generation part 107 Image sensor drive part 108 Image memory 109 Image processing part 110 Image compression part 111 Image recording part 112 Monitor 112b Sub monitor 113 Keyboard CA Imaging device DCM Document FR Contour PC Notebook PC SS Accelerometer

Claims (11)

An image sensor;
An imaging optical system capable of adjusting a focal position and forming an optical image on a light receiving surface of the imaging element;
An in-focus position control means for controlling an in-focus position of the imaging optical system, and an imaging apparatus that captures an image of a subject that is inclined with respect to the optical axis of the imaging optical system and is roughly defined by a plane,
The in-focus position control means controls the image-capturing optical system so that the in-focus position is farther from the optical axis center position during imaging.   The imaging apparatus according to claim 1, wherein the focusing position control unit automatically obtains a focusing position and controls the imaging optical system so as to be farther from the optical axis center position. .   The focus position control means detects a focus position by processing a signal of the image sensor that forms an optical image on the light receiving surface. Imaging device.   The in-focus position control means extracts a contour of the subject by processing a signal of the imaging device that forms an optical image on the light receiving surface, and extracts the contour of the extracted subject. The imaging apparatus according to any one of claims 1 to 3, wherein the imaging optical system is controlled so that the in-focus position is farther from the optical axis center position within the range.   The focus position control means is configured to extract a contour of the subject by processing a signal of the imaging element that forms an optical image on the light receiving surface, and the contour of the subject is focused on a focus distance. 5. The imaging apparatus according to claim 1, wherein imaging is performed by dividing into a plurality of images in accordance with the image, and an entire image of the subject is obtained by combining the divided images. .   It is possible to set a first imaging mode for imaging a subject extending approximately in the vertical direction and a second imaging mode for imaging a subject extending approximately in the horizontal direction, and the second imaging mode is selected. In this case, the focusing position control means controls the imaging optical system so that the focusing position is farther from the optical axis center position during imaging. An imaging apparatus according to claim 1.   A first sensor that detects a direction of an optical axis of the imaging optical system, and the sensor detects that the optical axis of the imaging optical system faces upward from a horizontal direction; The imaging apparatus according to claim 6, wherein the second imaging mode is selected when it is detected that the optical axis of the imaging optical system is directed downward from the horizontal direction.   An electronic apparatus comprising the imaging device according to claim 1.   The electronic apparatus according to claim 8, further comprising a monitor on the front side of the imaging apparatus that displays an image of the subject based on a signal of the imaging element that forms an optical image on the light receiving surface.   10. The electronic device according to claim 8, further comprising: a sub-monitor on the back side of the imaging device that displays an image of the subject based on a signal of the imaging element that forms an optical image on the light receiving surface. 10. machine.   The electronic apparatus has a keyboard for inputting information, and has a sub-monitor on the keyboard for displaying an image of the subject based on a signal of the imaging element that forms an optical image on the light receiving surface. The electronic device according to claim 8.

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