JP2004170638A - Photograph taking device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photograph taking device capable of realizing accurate focus detection without depending on the luminance of a subject. <P>SOLUTION: The photograph taking device is equipped with an optical system including lenses 1a and 1b and a shape variable mirror 15 changing the shape of its reflection surface in accordance with an applied driving signal, a CCD 3 photoelectrically converting a subject image formed by the optical system, a signal processing part 5 performing specified signal processing to an imaging signal outputted from the CCD 3, a mirror control part 16 generating the driving signal applied to the mirror 15, and a CPU 11 controlling the control part 16. Before photographing, the CPU 11 controls the control part 16 so that the specified driving signal by which the focal position of the optical system is not drastically defocused may be applied to the mirror 15. Thereafter, it performs autofocus in an appropriate exposure state after performing exposure control. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image capturing apparatus, and more particularly, to an image capturing apparatus including an optical system including an active optical element.
[0002]
[Prior art]
2. Description of the Related Art Various types of image photographing apparatuses, such as a digital camera, a video camera, and a silver halide camera, have been proposed and commercialized. .
[0003]
Many of these video photographing apparatuses have an automatic focus adjustment function for automatically adjusting the focus of an optical system.
[0004]
This automatic focus adjustment function has been adopted in various cameras using a triangulation distance measuring sensor of an active method or a passive method. Many contrast detection methods for finding an optimum focus position based on contrast have been employed. For example, a hill-climbing control method has been applied to control the position of a photographing lens.
[0005]
More specifically, this contrast detection method is a method of extracting a high-frequency component in a video signal of a subject as an evaluation value corresponding to the position of the photographing lens, and controlling the photographing lens to a position where the evaluation value becomes maximum.
[0006]
On the other hand, an active optical element in which a functional region that generates output light in which the optical characteristics of incident light have been converted in accordance with an applied drive signal has been proposed, and such an active optical element includes a reflection surface As an example, a shape-variable mirror capable of changing the optical characteristics by changing the shape of the mirror is given as an example.
[0007]
A technique relating to autofocus of a digital camera using such a deformable mirror is disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-229100. A photometry operation is performed after a distance measurement operation is performed. I have.
[0008]
[Patent Document 1]
JP 2002-229100 A
[0009]
[Problems to be solved by the invention]
However, in the autofocus technique described in Japanese Patent Application Laid-Open No. 2002-229100, since the distance measurement operation is performed prior to the photometry operation, an appropriate exposure state is not obtained at the time of distance measurement. In particular, when the subject is extremely bright or dark, the peak of the contrast change may not be accurately detected. At this time, accurate distance measurement by the contrast detection method cannot be performed, and the focusing accuracy may be reduced.
[0010]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a video photographing apparatus capable of performing accurate focus detection without depending on luminance of a subject.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a video photographing apparatus according to a first aspect of the present invention includes an active optical element having a functional area for generating emission light obtained by converting optical characteristics of incident light according to an applied drive signal. An optical system including the optical system, an image sensor that photoelectrically converts a subject image formed through the optical system, and a signal processing unit that performs predetermined signal processing on an image signal related to the subject image output from the image sensor And, active optical element driving means for generating a drive signal to be applied to the active optical element, and control means for controlling the active optical element driving means, comprising, prior to performing imaging, the control means, The active optical element driving means is controlled to apply a predetermined drive signal to the active optical element so that the focal position of the optical system becomes appropriate. It is.
[0012]
Further, according to a second aspect of the present invention, in the video imaging device according to the first aspect, the active optical element is a shape variable mirror capable of changing optical characteristics by changing a shape of a reflection surface. is there.
[0013]
Further, in the video photographing apparatus according to the third invention, in the video photographing apparatus according to the first invention, when the control means determines an exposure amount prior to photographing, the control means controls the active optical element driving means. Then, the predetermined drive signal is applied to the active optical element.
[0014]
A video imaging device according to a fourth aspect of the present invention is the video imaging device according to the first aspect, wherein the control means controls the active optical element driving means when adjusting the white balance prior to photographing. And the predetermined drive signal is applied to the active optical element.
[0015]
According to a fifth aspect of the present invention, in the video imaging apparatus according to any one of the first to fourth aspects, the active optical element driving means includes a predetermined drive signal such that a focal position of the optical system becomes appropriate. A drive signal corresponding to a focus position at any position within a focus range from the shortest shooting distance to infinity is generated.
[0016]
A video imaging device according to a sixth aspect of the present invention is the video imaging device according to the fifth aspect, wherein the active optical element driving means outputs the predetermined driving signal as a predetermined driving signal for appropriately setting a focal position of the optical system. A drive signal corresponding to a focus position located substantially at the center of the focus range is generated.
[0017]
A video imaging device according to a seventh aspect is the video imaging device according to any one of the first to fourth aspects, wherein the optical system includes a varifocal optical system, and the active optical element driving unit includes: As a predetermined drive signal such that the focal position of the optical system becomes an appropriate one, in all the focal lengths that the variable focus optical system can take, any of the focusing ranges from the shortest shooting distance to infinity A drive signal corresponding to the in-focus position at the position is generated.
[0018]
An image capturing apparatus according to an eighth aspect of the present invention is the video image capturing apparatus according to the seventh aspect, wherein the active optical element driving means outputs the predetermined drive signal such that a focal position of the optical system becomes appropriate. At all focal lengths that the variable focus optical system can take, a drive signal corresponding to an in-focus position located substantially in the middle of the in-focus range included in common is generated.
[0019]
A video imaging device according to a ninth aspect is the video imaging device according to the first to eighth aspects, further comprising a temperature detecting unit, wherein the active optical element driving unit is responsive to a detection signal from the temperature detecting unit. Thus, the drive signal is corrected.
[0020]
A video imaging device according to a tenth aspect is the video imaging device according to any one of the first to ninth aspects, further comprising humidity detection means, wherein the active optical element driving means responds to a detection signal from the humidity detection means. Thus, the drive signal is corrected.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 5 show an embodiment of the present invention, and FIG. 1 is a block diagram showing a configuration of a digital camera.
[0022]
The video photographing apparatus according to the present embodiment is, for example, a digital camera and includes the following elements.
[0023]
The imaging optical system (optical system) reflects a lens 1a and a light beam passing through the lens 1a, and is a variable shape as an active optical element configured to change a mirror surface shape by applying a voltage. A mirror 15 and a lens 1b for forming a subject image by a light beam reflected by the shape-variable mirror 15 on a surface of a CCD 3, which is an image pickup device described later.
[0024]
Note that the lenses 1a and 1b schematically represent optical systems other than the deformable mirror 15 in the imaging optical system for forming a subject image on the image area of the CCD 3, and in reality, This is a more complicated optical system using a large number of lenses and the like.
[0025]
The stop 2 is disposed between the shape-variable mirror 15 and the lens 1b on the optical path of the imaging optical system, and forms an image on the CCD 3 by restricting a passing range of incident light as necessary. This is for controlling the light amount of the optical image.
[0026]
The CCD (Charge Coupled Device) 3 is an imaging device that photoelectrically converts an optical subject image formed by the operation of the imaging optical system and outputs an electrically captured image as an imaging signal.
[0027]
The imaging processing unit 4 includes a CDS (Correlated Double Sampling: correlated double sampling circuit), an AGC (Automatic Gain Control: an auto gain control circuit), an ADC (Analog to Digital Converter), and the like. This is to remove reset noise which may be included in the output captured image, adjust the signal level, etc., and convert the processed captured image which is an analog signal into captured image data which is a digital signal.
[0028]
The signal processing unit 5 is a signal processing unit, and outputs a white balance or the like to captured image data output from the imaging processing unit 4 or captured image data after expansion processing output from a compression / expansion processing unit 6 described later. This is for performing correction processing such as γ correction. The signal processing unit 5 further includes an AE (Automatic Exposure) detection circuit for determining an exposure amount and performing exposure control prior to photographing, and a contrast evaluation value for performing autofocus control. And a circuit related to a shooting preparation operation, such as an AF (Automatic Focus) detection circuit that obtains the following.
[0029]
The compression / decompression processing unit 6 performs a compression process on the captured image data output from the signal processing unit 5 and also performs a decompression process on compressed captured image data output from a card I / F 7 described later. It is. The compression / expansion processing of the captured image data at this time is performed by, for example, a JPEG (Joint Photographic Experts Group) method.
[0030]
The card I / F 7 is an interface for transmitting and receiving various data including writing and reading of captured image data between the digital camera and a memory card 8 described later.
[0031]
The memory card 8 is for recording and holding various data including captured image data, and is configured as a recording medium using a semiconductor, for example. The memory card 8 is configured to be detachable from a digital camera, for example. Therefore, the memory card 8 is not a specific component of the digital camera.
[0032]
The lens frame control unit 9 performs a zoom operation by controlling the lenses 1a and 1b and controls an exposure by controlling the aperture 2 in accordance with an instruction from a CPU 11 which will be described later. . When the optical system is not a zoom lens or when manual zooming is performed, the lens frame controller 9 controls only the aperture 2.
[0033]
The imaging control circuit 10 controls an imaging operation by the CCD 3 and the imaging processing unit 4 in accordance with an instruction from the CPU 11.
[0034]
A CPU (Central Processing Unit) 11 is a central processing unit for controlling the operation of the entire digital camera, and serves as control means.
[0035]
The memory 12 includes a ROM (Read Only Memory) in which a control program for causing the CPU 11 to control the operation of the entire digital camera is stored in advance, and a work storage area when the CPU 11 executes the control program. And a RAM (Random Access Memory) used as a semiconductor memory.
[0036]
The DAC (Digital to Analog Converter) 13 converts captured image data output as a digital signal from the signal processing unit 5 into an analog signal.
[0037]
The liquid crystal monitor 14 is a display device for displaying an analog captured image output from the DAC 13 so as to be observable.
[0038]
The mirror controller 16 changes the voltage (drive signal) applied to the deformable mirror 15 in accordance with an instruction from the CPU 11 to control the deformable mirror 15 to have a desired shape. Element driving means.
[0039]
An I / F (Interface) unit 17 controls data transmission and reception between the CPU 11 of the digital camera and a PC 18 described later, and includes, for example, a USB (Universal Serial Bus) interface circuit. It is configured.
[0040]
A PC (Personal Computer) 18 is for storing various data to be recorded in advance in the digital camera during the manufacturing process of the digital camera, and stores, for example, data for correcting the sensitivity of the CCD 3 in the memory. 12 is used to write data for controlling the deformable mirror 15 to a later-described lookup table of the mirror control unit 16. Therefore, the PC 18 is not an element constituting a digital camera.
[0041]
The temperature sensor 19 is a temperature detecting unit that detects the temperature of the environment where the digital camera is placed under the control of the CPU 11 and outputs the temperature to the CPU 11.
[0042]
The humidity sensor 20 is a humidity detecting unit that detects the humidity of the environment where the digital camera is placed and outputs the humidity to the CPU 11 under the control of the CPU 11.
[0043]
Next, the configuration of the deformable mirror 15 will be described with reference to FIGS. FIG. 2 is an exploded perspective view showing the principle configuration of the deformable mirror 15, and FIG. 3 is a sectional view showing the principle configuration of the shape variable mirror 15.
[0044]
The deformable mirror 15 includes an upper substrate 15a, a circular thin film 15c whose periphery is held by the upper substrate 15a, and a lower substrate 15b that is disposed to face the upper substrate 15a while maintaining a predetermined interval. A plurality of fixed electrodes 15d fixedly held on the lower substrate 15b so as to face the thin film 15c; and a plurality of fixed electrodes 15d electrically connected to the plurality of fixed electrodes 15d and supplied from the mirror control unit 16. And a terminal 15e disposed on the lower substrate 15b to apply a voltage to each of the fixed electrodes 15d.
[0045]
The thin film 15c is an organic film in which a conductor such as aluminum is coated on the upper surface side in FIGS. 2 and 3, and reflects light incident from above in FIGS. 2 and 3. Aluminum or the like coated on the organic film is connected to the ground.
[0046]
In the example shown in FIG. 2, the fixed electrode 15d has a total of five electrodes including a circular electrode at the center and four electrodes that divide the ring-shaped portion around the center electrode into four equal parts. It is configured to have.
[0047]
Corresponding to the structure of the fixed electrode 15d, the terminal 15e also has five terminals for supplying voltages V1, V2, V3, V4, V5 to the respective electrodes.
[0048]
Note that the distance between the upper substrate 15a and the lower substrate 15b is kept constant by, for example, inserting a spacer (not shown) therebetween.
[0049]
The operation of the variable shape mirror 15 is as follows.
[0050]
When the voltages V1, V2, V3, V4, V5 are supplied to the fixed electrode 15d through the terminal 15e to give a potential difference between the thin film 15c and the fixed electrode 15d, the fixed electrode 15d and the thin film 15c are attracted. Although a Coulomb force in the direction is generated, since the fixed electrode 15d is fixed to the lower substrate 15b, only the thin film 15c is drawn toward the fixed electrode 15d.
[0051]
At this time, since the periphery of the thin film 15c is fixed to the upper substrate 15a, the thin film 15c is deformed into a gentle concave shape such that the center of the thin film is closest to the fixed electrode 15d. As a result, the aluminum surface coated on the upper surface of the thin film 15c in FIGS. 2 and 3 becomes a concave reflecting surface (mirror surface) and functions as an optical surface having power.
[0052]
As described above, the shape variable mirror 15, which is the active optical element, has the functional area for generating the outgoing light obtained by converting the optical characteristics of the incident light according to the applied drive signal.
[0053]
At this time, even if the thin film 15c is deformed as described above, a sound is hardly generated by the deformation, and furthermore, the power for performing the deformation and the power required for maintaining the deformed state are also low. It is very slight.
[0054]
In the above-described principle configuration, the thin film 15c is formed by devising a method of dividing the fixed electrode 15d and devising each divided shape, and by appropriately controlling the potential applied to each of the fixed electrodes 15d. (Including curvature) can be deformed into a desired shape. At this time, it is possible not only to change the shape of the mirror into a shape with a fixed curvature (spherical surface), but also to change the shape into a spheroid, a paraboloid of revolution, or a more complicated free-form surface.
[0055]
In the present embodiment, as described below, a focusing function is realized by the change in the curvature of the deformable mirror 15 having the same effect as changing the curvature of the lens in the optical system. .
[0056]
The deformable mirror 15 is configured to have a diameter of, for example, about 8 mm in a general digital camera, and the amount of deformation that occurs when a voltage is applied is such that the maximum displacement of the center is about 20 μm. , The applied voltage and the optical aberration.
[0057]
Therefore, in order to enable the focus adjustment with such a displacement, the optical system (that is, schematically shown in FIG. 1) positioned closer to the CCD 3 than the shape-variable mirror 15 so as to increase the focus sensitivity to deformation. In the optical system, the magnification of the lens 1b) is increased.
[0058]
FIG. 4 is a block diagram illustrating a configuration example of the mirror control unit 16.
[0059]
The mirror control unit 16 includes a step-up circuit 16a that receives a 3.3V power supply (not shown) inside the digital camera and generates a high voltage of, for example, 100V necessary to drive the shape variable mirror 15, and a shape variable mirror 15 An LUT (lookup table) 16c for outputting information to be stored in response to a command sent from the CPU 11 when information for control is stored as a table for focusing, and a CPU 11 for detecting focus by controlling the CPU 11. A signal selector for selecting a control signal of the deformable mirror 15 sent from the controller and outputting the control signal to a drive circuit 16b, which will be described later, and selecting an output signal of the LUT 16c and outputting it to the drive circuit 16b when focusing is performed. SEL.) 16d and the fixed electrode 1 according to the output from the signal selector 16d. The voltage applied to each of the d is configured to have a, a drive circuit 16b that generates and outputs a voltage received from the booster circuit 16a.
[0060]
In the focus detection operation of the mirror control unit 16 having such a configuration, the CPU 11 instructs V1, V2,..., V5 indicating the voltages to be applied to the respective terminals 15e shown in FIG. This is done by selecting and selecting. On the other hand, in the focusing operation, when the in-focus surface position is obtained by the focus detection operation, the CPU 11 outputs information corresponding to the in-focus surface position to the LUT 16c, and the LUT 16c uses the information as shown in FIG. This is performed by referring to the table and inputting its output to the signal selector 16d for selection.
[0061]
FIG. 5 is a table showing an example of data stored in the LUT 16c.
[0062]
.., V5 (more specifically, output information output to the drive circuit 16b) indicating the voltage applied to each of the terminals 15e shown in FIG. 2 are 0 to 127 in the example shown in FIG. It can be set in 128 steps according to the input information up to. The reason why the resolution of the input information is set as relatively high as 128 steps is to control the focal plane position at intervals equal to or less than the depth of field.
[0063]
In the digital camera having such a configuration, if the distance measurement operation is performed prior to the photometry operation, as described above, accurate distance measurement may not be performed depending on the luminance of the subject. In the embodiment, the photographing operation of the digital camera is performed as follows.
[0064]
First, a photometric area is set in a photographic screen, a photographic signal in the photometric area is detected, and the exposure is adjusted by changing a shutter speed, an aperture value, a photographic signal level, and the like.
[0065]
After the photometric operation is completed, a focus area is set in the photographing screen, a photographing signal of an appropriate exposure in the focus area is detected by the contrast detection method, and the shape variable mirror 15 is driven. Is controlled.
[0066]
As described above, when the distance measurement operation is performed after the photometry operation, the position of the shape variable mirror 15 is required with high accuracy in the digital camera using the shape variable mirror 15 as in the present embodiment. Will be described.
[0067]
First, in a general digital camera that performs focus adjustment by adjusting the lens position, if the dimensional error and the mounting error of the lens frame and other optical components are added together, several tens to hundreds of It is considered that a slight error has occurred in the focus adjustment system. It is difficult to reduce such an error by further increasing the precision of the manufacturing process, and if it were to be done, it would take a lot of trouble and cost. Therefore, in an actual digital camera, it is common to provide a margin in a focus adjustment range and adjust the number of driving pulses when driving a focus lens group with a stepping motor or the like. is there.
[0068]
More specifically, in an ordinary digital camera optical system, the moving distance of the lens required for focus adjustment is about several mm, and a margin of about several tens of microns is provided at both ends of this moving range. I have. Even if the focus lens group is in contact with one end of the movement range of the lens including this margin, if the focus adjustment range of several mm wide differs from the focus adjustment range by several tens of microns, the state is greatly defocused. It will not be. Therefore, when performing the AE operation or the AWB operation before photographing, generally good exposure adjustment and white balance adjustment can be performed without being aware of the in-focus state, that is, without driving the lens position close to the in-focus position. It can be performed in a short time.
[0069]
However, in a digital camera that uses the deformable mirror 15 for focus adjustment, even if it is desired to perform the same, there is a possibility that significant defocus will occur as described below.
[0070]
That is, as described above, the optical system of the digital camera in which the deformable mirror 15 is applied to the focus adjustment adopts a configuration in which the focus sensitivity to the deformation of the deformable mirror 15 is increased. The sensitivity to the dimensions and the mounting position is also increased, and even a slight error will cause a significant shift in the focal position. Therefore, if the deformable mirror 15 is configured to focus from the shortest shooting distance to infinity in a deformed state and absorb the above error, the deformable mirror 15 is significantly deformed when the deformable mirror 15 is not deformed. It will be in a defocused state. In this largely defocused state, even if photometry is performed, it is difficult to perform accurate exposure adjustment as described above.
[0071]
Therefore, in the digital camera according to the present embodiment, the shape variable mirror 15 is deformed so as to enable almost satisfactory exposure adjustment, and then the photometry operation and the white balance adjustment are performed, and then the autofocus operation is performed. ing. That is, the shape variable mirror 15 is deformed so as to be at an appropriate focus position even before the photometric operation or the like prior to the distance measuring operation.
[0072]
If the optical system employs a vari-focal lens which is a variable focus optical system, a change in the focal length causes a focal shift. It is possible to absorb by deformation. That is, by setting the deformation amount of the shape-variable mirror 15 to be a value obtained by adding the change amount of the focal length, it becomes possible to focus from the near point to infinity at all the focal lengths.
[0073]
For example, a digital camera adopts an optical system using a varifocal lens that is a variable-focus optical system of a type that can change the focal length in a step-like manner, and the focal length in terms of 35 mm film is 35 mm, It is assumed that the configuration is such that it can be changed to 50 mm, 65 mm, 80 mm, and 95 mm.
[0074]
The input to the LUT 16c at each of these converted focal lengths is, for example, as shown in FIG. FIG. 6 is a table showing how the input to the LUT 16c changes according to the focal length.
[0075]
That is, when the focal length is equivalent to 35 mm in terms of 35 mm film, the input to the LUT 16 c for focusing on the shortest shooting distance is 10, the input to the LUT 16 c for focusing on infinity is 98, and the focal length is 50 mm. When the distance is considerable, the input to the LUT 16c for focusing on the shortest shooting distance is 20, the input to the LUT 16c for focusing on infinity is 108, and when the focal length is 65 mm, the focus is on the shortest shooting distance. The input to the LUT 16c is 30, the input to the LUT 16c for focusing on infinity is 118, and the input to the LUT 16c for focusing on the shortest shooting distance is 24 when the focal length is equivalent to 80 mm. When the input to the LUT 16c for focusing is 112 and the focal length is equivalent to 95 mm, the focusing is performed at the shortest shooting distance. The input to LUT16c for 18, the input to LUT16c for focusing to infinity is configured 106, and so as.
[0076]
As described above, when the error is not taken into consideration, by setting the input to the LUT 16c at all focal lengths to a value from 10 to 118, focusing can be performed from the shortest shooting distance to infinity. The amount of correction of the dimensional error and the mounting error of the part and the amount of AF margin for detecting the peak of the contrast by the hill-climbing method are added to the input value to allow a margin corresponding to 9 as an input value. In other words, control is performed using values from 1 (that is, 10−9) to 127 (that is, 118 + 9) among the input values prepared from 0 to 127 as input values to the LUT 16c.
[0077]
The operation of actually taking a picture with such a digital camera is as follows.
[0078]
When power is supplied to the digital camera, first, it is checked whether or not the power supply voltage supplied from the battery is within a predetermined range by a sensor output (not shown), and further, a recordable memory card 8 is mounted. Make sure that
[0079]
Next, in order to avoid such a large defocus as described above, the error correction amount and the AF margin amount in the control table recorded in the LUT 16c of the mirror control unit 16 are used. AE for driving the shape variable mirror 15 with the center 64 (focusing position located substantially in the middle) of the values from to 127 as an input to the LUT 16c, and determining the exposure amount while maintaining the shape. The control is performed so as to perform the operation and the AWB operation for adjusting the white balance.
[0080]
Here, the median value (first median value) 64 of the input values 1 to 127, which is a focusing range that can be accommodated including an error, is used for all the focal lengths that the variable focus optical system can take. However, at all the focal lengths that the variable focus optical system can take, the input value 64 (in this case, the first input value 64) which is located substantially in the middle of the input values 30 to 98 (see FIG. 6) of the focusing range included in common. , But generally different). With such a value, since the focal length is within the focusing range (including the error correction amount) at all focal lengths, a state in which the variable-shape mirror 15 is largely defocused as in a state in which the variable-shape mirror 15 is not driven. And accurate exposure control can be performed.
[0081]
In the case where more appropriate exposure control is required in an optical system employing a varifocal lens, when the input value is adjusted to the focal length, the vicinity of the center (focusing position located approximately in the middle) is selected. It is also possible to use the value of Specifically, when the focal length is equivalent to 35 mm in 35 mm film conversion, a value near 54, which is the median of 10 to 98, may be input to the LUT 16 c. When the focal length is equivalent to 50 mm, A value near 64, which is the median from 20 to 108, may be input to the LUT 16c.
[0082]
Further, the shape of the thin film 15c made of an organic film coated with aluminum or the like may change due to environmental factors such as temperature and humidity. Therefore, using the temperature information output from the temperature sensor 19 and the humidity information output from the humidity sensor 20, the control table is changed to an appropriate one, or the input value of the control table is changed. By making corrections, more accurate AF control, AE control, AWB control, and the like can be performed.
[0083]
At this time, it is possible to detect not only the temperature and humidity as described above, but also a factor that influences the driving state of the active optical element more widely. Distance measurement and the like become possible. Other examples include detecting the direction of gravity and controlling the applied voltage according to the direction of gravity.
[0084]
In order to maintain the shape of the deformable mirror 15, the means for holding the applied voltage is the simplest. However, as described above, the deformable mirror 15 controls the shape of the reflecting surface by Coulomb force. In this case, since the shape variable mirror 15 forms a capacitor and requires a certain amount of time for discharging, it is possible to maintain the shape even if the application of voltage is stopped for a very short time. . Therefore, it is possible to perform control such that the AE operation or the AWB operation is performed in a state where the driving of the shape variable mirror 15 is stopped within a predetermined time.
[0085]
In the above description, the deformable mirror 15 has been described as an example of the active optical element. However, the present invention is not limited to this, and other active optical elements can be used.
[0086]
Further, in the above description, the mirror control unit 16 generates the drive signal corresponding to the focus position located substantially in the middle of the focus range from the shortest shooting distance to infinity, but is not limited thereto. Even if the drive signal corresponding to the in-focus position at any position within the in-focus range from the shortest photographing distance to infinity is generated, a certain effect can be achieved.
[0087]
According to such an embodiment, the AE operation or the like is controlled to an appropriate exposure by performing the AE operation or the like after driving the shape-variable mirror to an appropriate position. Therefore, the AE operation or the like is performed in a largely defocused state. Can be avoided, and an appropriate exposure value can be obtained.
[0088]
After performing the AE operation, since the AF operation is performed using an image captured in an appropriate exposure state, accurate focus detection is performed without depending on the brightness of the subject, and the subject is accurately detected. It becomes possible to focus.
[0089]
In the case of an optical system using a variable focus optical system, the optical system is driven to a focusing position located at a substantially middle position in a commonly included focusing range at all possible focal lengths of the variable focus optical system. Therefore, regardless of the state of the focal length, the photographing preparation operation such as AE or AWB can always be performed in a stable state.
[0090]
On the other hand, when driving to an arbitrary focal position within the focusing range, it is possible to perform a substantially appropriate shooting preparation operation in a shorter time.
[0091]
Furthermore, by detecting temperature, humidity, etc., and driving the deformable mirror according to the result, the shooting preparation operation is performed in a more stable state without being affected by these environmental factors, and the focal length is detected. It is possible to do.
[0092]
It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications and applications can be made without departing from the gist of the invention.
[0093]
【The invention's effect】
As described above, according to the video photographing apparatus of the present invention, accurate focus detection can be performed without depending on the luminance of the subject.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a digital camera according to an embodiment of the present invention.
FIG. 2 is an exploded perspective view showing a principle configuration of the deformable mirror in the embodiment.
FIG. 3 is a cross-sectional view showing a principle configuration of the deformable mirror in the embodiment.
FIG. 4 is a block diagram showing a configuration example of a mirror control unit in the embodiment.
FIG. 5 is a table showing an example of data stored in an LUT according to the embodiment.
FIG. 6 is a table showing how an input to an LUT changes according to a focal length in the embodiment.
[Explanation of symbols]
1a, 1b ... Lens (part of optical system)
2. Aperture
3 ... CCD (image sensor)
4: Image processing unit
5. Signal processing unit (signal processing means)
9… Mirror frame control unit
10 ... Imaging control circuit
11 CPU (control means)
12 ... Memory
15 Shape variable mirror (part of optical system, active optical element)
15a: Upper substrate
15b: lower substrate
15c: Thin film
15d: fixed electrode
15e ... terminal
16. Mirror control unit (active optical element driving means)
16a ... Booster circuit
16b ... Drive circuit
16c ... LUT (Lookup table)
16d ... signal selector
17 I / F section
19 temperature sensor (temperature detecting means)
20 Humidity sensor (humidity detecting means)

Claims (10)

An optical system including an active optical element in which a functional region that generates output light obtained by converting the optical characteristics of incident light according to the applied drive signal,
An image sensor that photoelectrically converts the subject image formed through the optical system,
Signal processing means for performing predetermined signal processing on an imaging signal related to the subject image output from the imaging element,
Active optical element driving means for generating a drive signal to be applied to the active optical element,
Control means for controlling the active optical element driving means,
With
The control unit controls the active optical element driving unit before photographing to apply a predetermined drive signal to the active optical element so that the focal position of the optical system is appropriate. A video photographing apparatus characterized in that: The image capturing apparatus according to claim 1, wherein the active optical element is a shape variable mirror capable of changing optical characteristics by changing a shape of a reflection surface. The control means controls the active optical element driving means to apply the predetermined drive signal to the active optical element when determining an exposure amount prior to photographing. The video photographing device according to claim 1, which performs the operation. The control means controls the active optical element driving means to adjust the white balance prior to photographing so as to apply the predetermined drive signal to the active optical element. The video photographing device according to claim 1, which performs the operation. The active optical element driving means may be a predetermined drive signal such that the focal position of the optical system is an appropriate one, and a focus position at any position within a focus range from the shortest shooting distance to infinity. The video photographing apparatus according to any one of claims 1 to 4, wherein the apparatus generates a drive signal corresponding to the following. The active optical element driving means generates a drive signal corresponding to a focus position located substantially in the middle of the focus range, as a predetermined drive signal that makes the focus position of the optical system appropriate. The video photographing apparatus according to claim 5, wherein The optical system is configured to include a variable focus optical system,
The active optical element driving means, as a predetermined drive signal such that the focal position of the optical system is an appropriate one, at all focal lengths that the variable focus optical system can take, from the shortest shooting distance to infinity The video photographing apparatus according to any one of claims 1 to 4, wherein a driving signal corresponding to a focus position at any position within the focus range is generated. The active optical element driving means, as a predetermined drive signal such that the focal position of the optical system becomes an appropriate one, at all focal lengths that the variable focus optical system can take, the focus range included in common 8. The image photographing apparatus according to claim 7, wherein the apparatus generates a drive signal corresponding to an in-focus position located substantially in the middle. Further comprising a temperature detecting means,
9. The device according to claim 1, wherein the active optical element driving unit corrects the driving signal in accordance with a detection signal from the temperature detection unit. Video shooting device. Further comprising humidity detection means,
The said active optical element drive means correct | amends the said drive signal according to the detection signal from the said humidity detection means, The Claim 1 characterized by the above-mentioned. Video shooting device.

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