JP2006078734A - Photographing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a photographing apparatus capable of performing a TTL auto-focusing in a short period of time even when an imaging element high in the number of pixels is disposed. <P>SOLUTION: A lead screw 105 with which nuts 104 provided on a lens hold frame 103 are helically engaged is rotated by a stepping motor 106, thereby moving a focusing lens 101 to the vicinity of a focused point. Further, a voltage as a drive signal is applied from a drive circuit 111 to a piezoelectric element 110 supporting the imaging element 102, and thus the piezoelectric element 110 is extended or shortened to move the imaging element 102 to the just-focused position. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photographing apparatus that includes a photographing optical system and an image sensor and generates an image signal representing a subject image formed on the image sensor via the photographing optical system.

  In some imaging devices, a distance measuring device is not provided separately, and subject light guided through the imaging lens is imaged on an imaging device, and distance measurement is performed using the imaging device. When such distance measurement (hereinafter referred to as TTL distance measurement) is performed, for example, a focus adjustment lens is moved using a stepping motor, and an image is formed on the image pickup device for each unit step of the stepping motor. An image signal representing the subject is generated.

  By the way, when the number of pixels of the image sensor is increased and the pixels are miniaturized, it is expected that blurring of an image is emphasized unless the unit step is further refined and accurate focus adjustment is performed. .

  At present, in a photographing apparatus or the like, a stepping motor whose rotation diameter is reduced to about 6 mm is used based on a request for downsizing. In this stepping motor of about 6 mm, the number of poles is 20 poles. Things have been announced. The unit step corresponds to the number of poles, and in order to further refine the unit step, a pole number of 20 poles or more is required. Is not easy.

  In addition, it is conceivable that the screw pitch of the lead screw that is rotationally driven by the stepping motor is finely screwed with the nut on the lens holding frame side, but the screw pitch of the lead screw has also been reduced to 0.2 mm. The above miniaturization cannot be expected.

  Even if the screw pitch is 0.2 mm or less, this time, the screw pitch is too small, and it becomes easy to disengage the nut on the lens holding frame side and the lead screw. There is also a risk that shooting will be hindered.

  Thus, since the screw pitch of the lead screw and the number of poles of the stepping motor are almost close to the limit value, the number of poles cannot be increased or the screw pitch cannot be further reduced.

  In order to cope with such a situation, in addition to the moving means composed of the stepping motor, the lead screw and the rack member, a piezoelectric element for moving the lead screw for fine adjustment is provided, and the lead screw itself is moved finely. Some attempt to perform a focus adjustment (see, for example, Patent Document 1).

However, if the lead screw itself is moved as in Patent Document 1, rattling may occur in the lead screw and the lens holding frame may be tilted, and so-called tilting may occur.
JP 2002-354332 A

  In view of the above circumstances, the present invention provides an imaging apparatus capable of performing TTL distance measurement accurately in a short period of time and without causing tilt even when an imaging device having a large number of pixels is provided. Objective.

A first imaging apparatus of the present invention that achieves the above object includes an imaging optical system and an imaging element, and generates an image signal representing an object image formed on the imaging element via the imaging optical system. In the device
First focus adjustment means for performing coarse focus adjustment by moving at least a part of the optical components of the photographing optical system in the optical axis direction;
And a second focus adjusting means for finely adjusting the focus by moving the image pickup device in the optical axis direction.

  According to the first photographing apparatus of the present invention, after the coarse adjustment is performed by the first focus adjustment unit, the fine adjustment is performed by the newly added second second focus adjustment unit. .

  Then, the first focus adjustment unit quickly moves the focus adjustment lens to the vicinity of the in-focus position, and then the second focus adjustment unit moves the image sensor to move the position of the image sensor relative to the focus adjustment lens. By adjusting, accurate focus adjustment can be performed in a short time.

  As described above, if only the vicinity of the in-focus point can be finely adjusted by the second focus adjustment unit, the second focus adjustment unit does not finely adjust the distance from the nearest point to the farthest point. Therefore, an imaging device capable of accurately performing TTL distance measurement in a short time is realized no matter what high-pixel imaging device is provided.

Here, the first focus adjustment unit moves the focus adjustment lens constituting the photographing optical system in the optical axis direction.
It is preferable that the second focus adjusting unit has a piezoelectric element that supports the imaging element and moves the imaging element in the optical axis direction by the piezoelectric element.

  In this way, when the conventional focus adjustment means including the lead screw and the nut is used as the first focus adjustment means, and the piezoelectric element that supports the image sensor is used as the second focus adjustment means, the above-described configuration can be obtained. This photographing apparatus can be realized simply by adding a slight change of adding an elastic piezoelectric element that supports the image pickup element. Also, after moving the lens to the vicinity of the in-focus position with the conventional focus adjustment means, it is possible to move the lens finely with the resolution of the piezoelectric element and place the lens at the focus position, so the time required for ranging And the focus adjustment is performed with high accuracy.

  Further, when the image sensor is supported by the piezoelectric element, if the image sensor is supported by one piezoelectric element, the image sensor may be tilted or tilted due to variations in expansion and contraction of the piezoelectric element itself.

If such a tilt is likely to occur,
It is preferable that the piezoelectric element that supports the imaging element includes a plurality of piezoelectric elements, and an inclination adjusting unit that adjusts the inclination of the imaging element with respect to the optical axis using the plurality of piezoelectric elements is preferable.

  When a plurality of piezoelectric elements are provided in this way and different drive signals are given to the plurality of piezoelectric elements to individually adjust the amount of expansion or contraction, the image pickup element can be controlled according to the inclination. The tilt / tilt can be adjusted.

The second imaging apparatus of the present invention that achieves the above object includes an imaging optical system and an imaging element, and receives an image signal representing a subject image formed on the imaging element via the imaging optical system. In the imaging device to generate,
It has a plurality of piezoelectric elements that support the image pickup device, and includes an inclination adjusting means that adjusts the inclination of the image pickup device with respect to the optical axis using the plurality of piezoelectric elements.

  According to the second photographing apparatus of the present invention, the inclination of the image sensor is adjusted by the inclination adjusting means to prevent the occurrence of tilt.

  When the tilt adjusting unit is also used as the second focus adjusting unit of the first photographing apparatus of the present invention, even if an image sensor having a high pixel count is provided, the tilt adjusting unit is accurate in a short time. An imaging apparatus capable of performing TTL distance measurement without causing tilt is realized.

  As described above, even when an image sensor with a high pixel count is provided, an imaging apparatus capable of performing TTL distance measurement with high accuracy and without causing tilt is realized.

  Embodiments of the present invention will be described below.

  FIG. 1 is an external perspective view showing an external appearance of a camera which is an embodiment of a photographing apparatus of the present invention.

  The camera 1 includes a photographic optical system and an image sensor, and generates an image signal representing a subject image formed on the image sensor via the photographic optical system.

  A lens barrel 10 is provided at the center of the camera body 1a shown in FIG. 1, and a finder 11 is provided above the lens barrel 10. While looking through the viewfinder 11 or visually recognizing a subject captured by the photographing optical system in the lens barrel 10 on a display screen (not shown) on the back side, a release button on the upper surface of the camera body 1a is used for a photo opportunity. 13 is operated and shooting is performed. The release button 13 has two operation modes of half-pressing and full-pressing. When the half-pressing operation is performed, TTL distance measurement is performed in the photographing apparatus 1, and when the half-pressing operation is performed, Photographing is performed with a focus corresponding to the subject distance obtained by the TTL distance measurement. If the photometry unit in the camera detects that the brightness of the object field is insufficient when this shooting is performed, the flash light is emitted from the flash light emission window 12 provided next to the viewfinder 11 and the amount of light necessary for shooting. Is given to the subject and shooting is performed.

  FIG. 2 is a block diagram showing the internal configuration of the camera 1 in FIG.

  The photographing apparatus 1 includes a TTL distance measuring unit that measures a subject distance using subject light obtained through a photographing lens including a zoom lens 100a and a focus lens 101. In this embodiment, the photographing device 1 and the focus lens 101 are imaged. The TTL distance measuring unit is composed of the element 102 (hereinafter referred to as a CCD since a CCD solid-state imaging device is used), the A / D unit 12a, and the signal processing block 13a. The focus lens which is a component of the TTL distance measuring unit corresponds to the focus adjustment lens according to the present invention.

  In the signal processing block 13a, signal processing such as white balance adjustment and YC separation is also performed.

  In this example, the signal processing block 13a, the JPEG encoder 16 and the card I / F 17 are configured by a DSP, and the DSP is controlled by the CPU 100. The CPU 100 controls the operation of the photographing apparatus according to the procedure of the program recorded in the ROM 100a. When an operation signal of the release button 13 in the key block 130 is input to the CPU 100, for example, Processing corresponding to the release operation signal is notified to the DSP so that the signal processing block 13a and the card I / F 17 in the DSP perform necessary processing.

  First, the operation of the photographing apparatus 1 when the power switch in the key block 130 is turned on will be described.

  When the power switch is turned on, power is supplied from the battery to the CCD 102, A / D 12 and the like shown in FIG. When power is supplied to the CCD 102, a subject in the direction in which the photographing lens including the zoom lens 100a and the focus lens 101 is directed is imaged on the CCD 102. At this time, the CPU 10 gives an instruction to output the image data representing the subject imaged on the CCD 102 via the TG 11a at every predetermined time, causes the CCD 102 to output the image data, and further the A / D 12a. Then, the image data is supplied to the signal processing block 13a at every predetermined time. At the same time, an instruction is issued from the CPU 100 to the driver 1061, the stepping motor 106 is driven by the driver 1061, and the focus lens 101 is moved along the optical axis.

  The signal processing block 13a detects the contrast based on the image signal supplied from the CCD 102 for each position in the middle of the movement of the focus lens 101, and calculates an AF evaluation value from the contrast. Then, processing for setting the peak of the AF evaluation value to the in-focus position is performed.

  In the imaging apparatus 1 of this embodiment, the CCD 102 is supported by the piezoelectric element 110 and fine adjustment is performed by moving the CCD 102 in the optical axis direction in order to increase the detection accuracy of the focus position of the signal processing unit. I am also able to do it.

  As a result, the focus lens 101 can be accurately moved to the in-focus position, and a focused subject is imaged on the CCD 102. Image data representing the subject imaged on the CCD 102 is output to the signal processing block 13a via the A / D 12a, and image processing such as YC separation is performed on the image data supplied from the CCD 102 by the signal processing block 13a. The image processed image data is output to the DRAM 14 at every predetermined time, and the image data at every predetermined time is stored in the DRAM 14 one after another. The image data stored in the DRAM 14 is supplied to the image display unit 15 at a predetermined time. The image display unit 15 switches the subject based on the image data supplied at the predetermined time and sequentially displays them on the display screen. To do. In this way, the subject captured by the photographing lens is displayed on the display screen of the image display unit.

  When the release button 13 is pressed at a photo opportunity while viewing the subject displayed on the display screen, a signal for performing exposure for a predetermined time from the timing when the release button 13 is pressed is supplied from the TG 11a to the CCD 102. Is done. After the predetermined time has passed and the exposure is completed, image data is output from the CCD 102. The output image data is supplied to the signal processing block 13a via the A / D 12a, and the image data processed by the signal processing block 13a is further supplied to the JPEG encoder 16. The JPEG encoder 16 compresses the image data, and an image file composed of the compressed image data and information related to the compression is recorded on the memory card 18 under the control of the card I / F 17.

  The configuration of the TTL distance measuring unit provided in such a camera 1 will be described in detail.

  FIG. 3 is a diagram illustrating a configuration of the TTL distance measuring unit described with reference to FIG.

  In the present embodiment, the TTL distance measuring unit includes two adjusting means: a first focus adjusting means according to the present invention and a first focus adjusting means according to the present invention.

  First, the configuration of the first focus adjustment unit according to the present invention, in which the focus lens 101 which is at least a part of the optical components of the photographing optical system is moved in the optical axis direction to perform coarse focus adjustment, will be described.

  A nut 104 extends from the outer edge of the lens holding frame 103 that holds the focus lens lens 101 shown in FIG. The nut 104 is screwed into the lead screw 105, and the focus lens 101 is moved together with the lens holding frame 103 in the optical axis direction according to the rotation of the lead screw 105. A stepping motor 106 is provided on the end side of the lead screw 105. When the stepping motor 106 is driven and rotated by a driver 1061 (see FIG. 2) according to an instruction from the CPU 100, the lens holding frame 103 is provided. At the same time, the focus lens 101 moves in the optical axis direction. These constitute first focus adjusting means for performing coarse focus adjustment.

  A part of the lens holding frame 103 is engaged with the guide shaft 107 so that the lens holding frame 103 shown in FIG.

  As described above, if the screw pitch of the lead screw 105 is 0.2 mm and the number of poles of the stepping motor 106 is 20, the unit movement amount of the focus lens 101 per step of the stepping motor 106 is about 10 μ, and the unit The focus lens 101 cannot be moved more finely than the movement amount 10 μm.

  Therefore, in the present embodiment, the focus lens 101 is moved together with the lens holding frame 103 by the lead screw 105 to roughly adjust the distance between the focus lens 101 and the CCD 102, and then the piezoelectric element 110 supporting the CCD 102 is changed. It is improved so that fine adjustment can be performed by extending and contracting and moving the CCD 102.

  In this way, the same effect as that obtained when the focus lens 101 is moved more finely than 10 μm by the first focus adjusting means can be obtained by moving the CCD 102.

  Here, the configuration of the second focus adjusting means according to the present invention, which performs fine adjustment of the focus by moving the CCD 102 in the optical axis direction, will be described.

  As shown in FIG. 2, a support substrate 1020 is provided on the back surface of the CCD 102, and the piezoelectric element 110 is configured so as to support the CCD 102 together with the substrate 1020 so that the CCD 102 can be moved together with the support substrate 1020. Is arranged. When a drive signal (applied voltage) is applied to the piezoelectric element 110 from the external drive circuit 111 and the piezoelectric element 110 expands in the direction of increasing thickness, the CCD 102 moves to the focus lens 101 side, and when contracted, the CCD 102 moves away from the focus lens 101. Move to the side.

  At present, since it is easy to obtain about 5 μ / V as the resolution of the piezoelectric element 110, a drive circuit 111 having a minimum drive voltage specification for driving the piezoelectric element 110 of 0.1 V is manufactured here. The CCD 102 can be moved so as to obtain the same effect as when the focus lens 101 is moved more finely than 10 μm.

  With such a configuration, the focus lens 101 is quickly placed near the in-focus position together with the lens holding frame 103 by the lead screw 105 in response to the half-pressing operation of the release button 13, and then the piezoelectric element 110 is driven from the drive circuit to the piezoelectric element 110. By applying a voltage as a signal and adjusting the distance between the focus lens 101 and the CCD 102 in the vicinity of the in-focus position, the focus can be adjusted with high accuracy.

  As described above, if the first focus adjustment means for coarse adjustment and the second focus adjustment means for fine adjustment are arranged in the photographing apparatus, what kind of high pixel CCD is arranged? However, the focus lens can be easily driven to the just pin position by appropriately determining the drive voltage specification of the piezoelectric element in accordance with the number of pixels of the CCD.

  In this embodiment, the focus lens is moved as at least a part of the optical components of the photographing optical system. However, coarse adjustment may be performed by moving the aperture to change the subject depth.

  As described above, even if a CCD having a high pixel count is provided, an imaging apparatus capable of accurately performing TTL distance measurement in a short time is realized.

  Also, as shown in FIG. 2, if one side of the piezoelectric element is supported on one side of the substrate on which the CCD is mounted, the contact area becomes too large and variations in expansion and contraction occur on the parts of the contact surface. May occur, and the CCD may be tilted and tilted.

  FIG. 4 is a diagram showing an example in which the tilt adjusting means for preventing the tilt is constituted by a piezoelectric element. FIG. 4A shows the tilt adjusting means and the first focus adjusting means shown in FIG. 2, and FIG. 4B shows the tilt adjusting means that also serves as the second focus adjusting means. The positional relationship between the piezoelectric element 110 and the CCD 102 constituting the above is shown.

  The inclination adjusting means shown in FIG. 4 includes a plurality of piezoelectric elements 110 that support the CCD 102, and adjusts the inclination of the CCD 102 with respect to the optical axis using the plurality of piezoelectric elements.

  For example, when the piezoelectric elements 110A to 110C are arranged in a balanced manner as shown in FIG. 3 so that the inclination of the CCD 102 can be adjusted by expanding and contracting each of the three piezoelectric elements 110A to 110C, the CCD 102 is placed on the optical axis. In any direction, the inclination can be corrected.

  Further, if this tilt adjusting means is also used as the second focus adjusting means shown in FIG. 2, even if an image pickup device having a high pixel number is provided, the tilt can be accurately generated in a short time. An imaging apparatus that can perform TTL distance measurement is realized.

It is a figure which shows the imaging device which is one Embodiment of this invention. FIG. 2 is a configuration block diagram showing an internal configuration of the photographing apparatus 1 in FIG. 1. It is a figure which shows the structure of a TTL ranging part. It is a figure which shows the example at the time of comprising the inclination adjustment means for preventing a tilt with a piezoelectric element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image pick-up device 10 Lens barrel 11a Timing generator (TG)
12a A / D
13a Signal processor block 14 DRAM
15 Image Display Unit 16 JPEG Encoder 17 Card IF
18 Memory card 100 CPU
100a ROM
100b EEPROM
101 Focus lens (focus adjustment lens)
102 Image sensor (CCD)
1020 Supporting substrate 103 Lens holding frame 104 Nut portion 105 Lead shaft 106 Stepping motor 1061 Driver 107 Guide shaft 110 110A 110B Piezoelectric element 111 Drive circuit

Claims (4)

In an imaging device that includes an imaging optical system and an imaging device and generates an image signal representing a subject image formed on the imaging device via the imaging optical system,
First focus adjustment means for performing coarse focus adjustment by moving at least some of the optical components of the photographing optical system in the optical axis direction;
An imaging apparatus comprising: a second focus adjustment unit that performs fine adjustment of a focus by moving the image sensor in the optical axis direction. The first focus adjustment means moves a focus adjustment lens constituting the photographing optical system in the optical axis direction;
The photographing apparatus according to claim 1, wherein the second focus adjustment unit includes a piezoelectric element that supports the imaging element and moves the imaging element in the optical axis direction by the piezoelectric element.   3. The photographing according to claim 2, further comprising tilt adjusting means for adjusting the tilt of the image sensor with respect to the optical axis by using a plurality of piezoelectric elements supporting the image sensor. apparatus. In an imaging device that includes an imaging optical system and an imaging device and generates an image signal representing a subject image formed on the imaging device via the imaging optical system,
An imaging apparatus comprising: a plurality of piezoelectric elements that support the imaging element; and an inclination adjusting unit that adjusts the inclination of the imaging element with respect to the optical axis using the plurality of piezoelectric elements.

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