JP2009069739A - Image pickup apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To set a focus lens to the optimum focusing position when it is assumed that a subject is infinitely far. <P>SOLUTION: The image pickup apparatus includes: an image pickup means 103 that receives light from a subject image formed by the focus lens and converts it into an electric signal; extracting means 110 and 111 that extract a signal indicating the high frequency component of a signal photo-electrically converted on the light receiving means of the image pick-up means corresponding to a photometry area, during the drive of the focus lens in a scanning range; and focus control means 112 and 113 that detect the focusing state of the focus lens from the signal indicating the high frequency component and drive the focus lens to a focusing position. When the subject is infinitely far, a focusing state is detected by limiting the scanning range of the focus lens when the signal indicating the high frequency component is extracted. When the focusing position is obtained, the focus lens is driven to the focusing position and a focusing position for each photographing is stored. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging apparatus such as a digital camera or a video camera having an automatic focus detection function.

  2. Description of the Related Art Conventionally, digital cameras, video cameras, and the like have used automatic focus detection devices that perform high-frequency components of luminance signals obtained from image sensors such as CCDs and perform focusing operations (Patent Document 1, etc.).

  Some imaging apparatuses using such an automatic focus detection apparatus have a specific scene mode for shooting a specific scene where the subject distance is infinite, such as a fireworks display. In such a case, when the specific scene mode is set, the focus lens is driven to an infinite fixed point adjustment value that is adjusted in advance and the subject distance is infinite, and photographing is performed.

Also, in manual focus, when the subject distance is set to infinity, the focus lens is driven to the infinity fixed point adjustment value, and shooting is performed.
JP 2002-122773 A

  The conventional example has the following problems. In the specific scene mode or manual focus where the subject is at infinity, the focal position may be set to the infinity fixed point adjustment value. However, when the infinity fixed point adjustment value is different from the actual infinity due to poor adjustment, aging of the apparatus, etc., defocus may occur.

(Object of invention)
An object of the present invention is to provide an imaging apparatus capable of setting a focus lens to an optimum in-focus position when a subject is at infinity.

  In order to achieve the above object, the present invention provides a focus lens for adjusting the focus of a subject image, a driving means for driving the focus lens, and a subject image formed by the focus lens to receive an electrical signal. Imaging means for conversion, extraction means for extracting a signal indicating a high-frequency component of a signal photoelectrically converted on a light receiving surface of the imaging means corresponding to a distance measurement area while the focus lens is driven in a scanning range; A focus control unit that detects a focus state of the focus lens from a signal indicating a high-frequency component and drives the focus lens at a focus position, and when the subject is at infinity, When the focus state is detected by limiting the scanning range of the focus lens when extracting a signal indicating a high frequency component, and the focus position is obtained, the focus position is Drives the serial focus lens, it is an imaging device for storing the focus position of each shot.

  According to the present invention, it is possible to provide an imaging apparatus capable of setting a focus lens at an optimum in-focus position when a subject is at infinity.

  The best mode for carrying out the present invention is as shown in the following examples.

  FIG. 1 is a block diagram showing an imaging apparatus according to an embodiment of the present invention. In FIG. 1, an imaging apparatus includes an imaging lens 101 that captures an image, a focus lens 102 that adjusts the focus of a subject image, and an imaging element 103 that receives a subject image formed by the imaging lens 101 and converts it into an electrical signal. Have. Furthermore, an A / D converter 104 that converts an analog signal from the image sensor 103 into a digital signal, an electronic viewfinder 105 that displays an image converted into a digital signal by the A / D converter 104, and a digitized image temporarily It has an image memory 106 for storing automatically. Furthermore, the image processing unit 107 that performs image processing such as white balance, the image recording unit 108 that records the finally formed image, and the detection unit 109 that detects the zoom position and aperture value of the imaging lens 101 are provided. Further, a first extraction unit 110 that extracts a signal that is photoelectrically converted on the light receiving surface of the image sensor 103 corresponding to a distance measurement area (autofocus area) on the imaging screen, is extracted by the first extraction unit 110. It has the 2nd extraction part 111 which extracts the signal which shows the high frequency component of a signal. Furthermore, it has the focus position detection part 112 which detects the focus position corresponding to the extraction signal from the 2nd extraction part 111, and the control part 113 which controls the drive of the focus lens 102. FIG. Furthermore, it has the focus lens drive part 115 controlled by the calculation memory | storage part 114 and the focus lens control part 113. FIG.

  Here, it is assumed that a specific scene mode, such as a fireworks display, is set in which a subject is set at infinity by a characteristic scene mode setting unit (not shown). In this case, a control unit (not shown) that controls the aperture value and the shutter speed and the focus lens control unit 113 control the aperture value, the shutter speed, the position of the focus lens 102 and the control range corresponding to the zoom position of the specific scene mode. (Focal position scan range) is set. The calculation storage unit 114 stores the in-focus position of the focus lens 102 when the specific scene mode is set, and calculates a stored value fixed point when the subject is at infinity from the signal from the in-focus position detection unit 112. .

  The focus lens control unit 113 drives the focus lens based on the detection information in the focus position detection unit 112, the detection information in the detection unit 109 that detects the zoom position and the aperture value, and the stored value fixed point in the calculation storage unit 114. The focus lens 102 is driven by the unit 115. Thereby, the focus position of the focus lens 102 with respect to the subject can be optimally adjusted.

  Next, the procedure for actually adjusting the focus position will be described with reference to the flowchart of FIG.

  After a power switch (not shown) of the image pickup apparatus is turned on, a specific scene mode for shooting a specific scene where a subject such as a fireworks display is at infinity is set by a characteristic scene mode setting unit (not shown). . In this case, first, in step # 201, it is determined whether or not the camera has been focused a predetermined number of times (M times) after the specific scene mode is set. If the predetermined number of times of in-focus has been achieved, the process proceeds to step # 211 to be described later. If the number of times is less than the predetermined number, the process proceeds to step # 202. Here, the shooting in the specific scene mode is performed for a predetermined number of resets (B times) and reset ( It is determined whether it has been described later with reference to FIG. If the predetermined number of resets has been reset, the process proceeds to step # 210, which will be described later. If the number of resets is less than the predetermined number of resets, the process proceeds to step # 203, and here the focus position scan range (in order to extract a signal indicating a high frequency component) The focus lens scanning range). The focus position scan range is only in the vicinity of infinity because the subject distance in the specific scene mode is infinity.

  In the next step # 204, it is determined whether or not the switch SW1 is turned on. If the switch SW1 is not turned on, the process returns to step # 201. A focus position scan is performed in the focus position scan range. In the next step # 206, it is determined whether or not a focus position signal is obtained as a result of the focus position scan. If an in-focus position signal is obtained, the process proceeds to step # 212 described later. However, if the in-focus position cannot be obtained, the process proceeds to step # 207. In this case, the focus lens 102 is moved in advance to a stored value fixed point stored in advance in the calculation storage unit 112, more specifically, stored in the process of FIG. 4 or FIG. 5 described later, and the position is stored in the memory.

  In the next step # 208, it is determined whether or not the switch SW2 is turned on. If it is turned on, the process proceeds to step # 214 to perform a photographing operation. If the switch SW2 is not turned on, the process proceeds to step # 209 to determine the state of the switch SW1, and if the switch SW1 is turned off, the process returns to step # 201. On the other hand, if the switch SW2 remains ON, the process returns to step # 208 for determining the state of the switch SW1 while maintaining the position of the focus lens 102.

  If it is determined in step # 201 that the camera has been focused a predetermined number of times (M times) during shooting in the specific scene mode in the past, the process proceeds to step # 211 as described above. In step # 211, assuming that a statistically sufficient amount of data has been accumulated, an average value of past in-focus positions is calculated, stored, and the focus lens 102 is moved to the average value of past in-focus positions. Let Thereafter, the process proceeds to step # 208.

  If it is determined in step # 202 that the shooting in the specific scene mode has been reset a predetermined number of times (B times), the process proceeds to step # 210 as described above. In step # 210, assuming that a stored value fixed point for infinity that is reliable in the past is stored, the focus lens 102 is moved to the stored value fixed point. Thereafter, the process proceeds to step # 208.

  If the focus position scan is performed in the focus position scan range limited in step # 205, and it is determined in the next step # 206 that the focus position signal is obtained, the process proceeds to step # 212 as described above. move on. In step # 212, it is determined whether or not the focus signal is within a predetermined value (± XX) with respect to infinity adjusted in advance. As a result, if it is determined that the value is within a certain value, the process proceeds to step # 213, where the position of the in-focus position is detected as being small with respect to infinity, the position is stored, and the in-focus count is counted up (M = M + 1). To do. Then, the process proceeds to step # 208. On the other hand, if it is determined that the in-focus position is not within a certain value, it is determined that there is a large error with respect to the focus position at infinity, and the focus position at infinity is not stored and the process proceeds to step # 208.

  Next, the procedure for resetting the stored value fixed point will be described with reference to the flowchart of FIG. This operation is performed before step # 201 in FIG. 2, and is for canceling the shift of the infinity position due to a change with time.

  The power supply state of the imaging apparatus is checked. If the power is off, the process proceeds to step # 304. If the power is on, the process proceeds to step # 302, where it is determined whether a certain time has elapsed. If the fixed time has elapsed, the process proceeds to step # 304. If the fixed time has not elapsed, the process proceeds to step # 303, where it is determined whether or not the temperature change is greater than or equal to a certain value. If the temperature change is equal to or greater than a certain value, the process proceeds to step # 304. If the temperature change is not equal to or greater than the certain value, the reset of the stored value fixed point due to the time at infinity and the temperature has not occurred. The reset operation is finished.

  When the power of the imaging device is OFF (YES in # 301), the power is ON, and a certain time has passed (YES in # 302), or the temperature change is equal to or greater than a certain value (YES in # 303) ), The process proceeds to step # 304 as described above. In step # 304, the stored value fixed point position at infinity may have changed (because a mechanical position drift occurs and a difference from the electrical stored value occurs). Reset to 0 (M = 0). In the next step # 305, the current position of the focus lens 102 is stored, and in the subsequent step # 306, the reset counter is added (+1).

  In the next step # 307, it is determined whether or not the value of the reset counter exceeds a certain value. If it exceeds the certain value, the process proceeds to step # 308. In Step # 308, assuming that a sufficient amount of stored value fixed point at infinity has been obtained, an average value of the position of the focus lens 102 at the time of past resetting is calculated and set as a stored value fixed point. Then, the stored value fixed point reset operation is terminated.

  On the other hand, if it is determined in step # 307 that the value of the reset counter is equal to or less than a certain value, it is still determined that the amount of the stored value fixed point at infinity is not sufficient, and the average position of the focus lens 102 is The value is not calculated and the reset operation is terminated.

  Next, calculation of the average value of the stored value fixed points will be described using the flowchart of FIG. This operation is performed in step # 211 in FIG.

  First, in step # 401, it is determined whether or not the number of times of photographing (N) is 0 (a state in which the imaging device is used for the first time after being shipped). If 0 (N = 0), step # 401 is determined. In step 410, it is determined whether or not the number of resets is zero. If the number of resets is 0 as a result of the determination, the process proceeds to step # 411. In this case, since the imaging apparatus is used for the first time, the adjustment value at the time of assembly adjustment of the imaging apparatus is used as a stored value fixed point. On the other hand, if the number of resets is other than 0, the process proceeds to step # 412. Since the imaging apparatus has a past measurement result, the previous stored value fixed point that is more likely than the adjustment value at the time of assembly adjustment is used.

  If the number of times of photographing (N) is greater than 0 in step # 401, the process proceeds to step # 402, where the number of times of photographing (N) is less than a predetermined number of times (C) such as 10 that can be trusted as statistical data. It is determined whether or not there is. As a result of the determination, if the number of photographing (N) is equal to or less than the predetermined number (C) (N ≦ C), the process proceeds to step # 403. Then, the average value of the position of the focus lens 102 for each number of photographing is calculated, and this is used as a stored value fixed point. In the next step # 404, a counter for the number of photographing is added (N = N + 1).

  If it is determined in step # 402 that the number of shootings exceeds the predetermined number, the process proceeds to step # 405 and subsequent steps, and the amount of the position of the focus lens 102 that can be statistically processed is gathered. Process.

  In other words, in step # 405, the subject distance stored at the time of photographing is determined to be the farthest or most recent distance, and is excluded from the statistical processing target because the error with respect to infinity is large. Then, in the next step # 406, an average value and σ (standard deviation) are calculated, and in a subsequent step # 407, subject distances that do not fall within the average value ± σ are excluded. Then, in the next step # 408, the average value is obtained again, and this is used as a stored value fixed point. In the next step # 409, a counter for the number of photographing is added (N = N + 1).

  Thus, by eliminating a value having a large error with respect to infinity, the accuracy of the position of the focus lens 102 when the subject distance is infinity can be improved.

  Next, another example of the calculation of the stored value fixed point, which is different from the calculation of the stored value fixed point using the above average value, will be described with reference to the flowchart of FIG.

  First, in step # 501, it is determined whether or not the number of times of photographing (N) is 0. If 0 (N = 0), the process proceeds to step # 507, where it is determined whether or not the number of times of resetting is zero. Determine. If the number of resets is 0 as a result of the determination, the process proceeds to step # 508. In this case, since the imaging apparatus is used for the first time, the adjustment value at the time of assembly adjustment of the imaging apparatus is used as a stored value fixed point. On the other hand, if the number of resets is other than 0, the process proceeds to step # 509, and since the imaging apparatus has a past measurement result, the previous stored value fixed point that is more likely than the adjustment value at the time of assembly adjustment is used.

  If the number of times of photographing (N) is greater than or equal to 0 in step # 501, the process proceeds to step # 502, where it is determined whether or not the number of times of photographing (N) is equal to or less than a predetermined number (C). As a result of the determination, if the number of photographing (N) is equal to or less than the predetermined number (C) (N ≦ C), the process proceeds to step # 503, and the farthest value of the position of the focus lens 102 for each number of photographing is closest to infinity. As a value, the stored value is fixed. Then, in the next step # 504, a counter for the number of photographing is added (N = N + 1).

  If it is determined in step # 502 that the number of shootings exceeds the predetermined number (C), the process proceeds to step # 505 and subsequent steps, and statistical processing is possible. Therefore, the following processing is performed.

  In other words, in step # 505, the farthest subject distance stored at the time of shooting is assumed to be at the end of the statistical distribution, and the accuracy is expected to be low. Is a fixed point of memory value. In the next step # 506, a counter for the number of photographing is added (N = N + 1).

  Also in this case, since the value with a large error with respect to infinity is excluded, the accuracy of the position of the focus lens 102 when the subject distance is infinity can be improved.

  The calculation of the stored value fixed point described with reference to FIGS. 4 and 5 is performed for each zoom position or aperture value of the imaging apparatus. As a result, the accuracy of the position of the focus lens 102 with respect to an infinite subject distance can be improved in accordance with the characteristics of the imaging optical system of the imaging apparatus.

  Such processing is not limited to a specific scene mode for shooting a specific scene where the subject is at infinity, and the same effect can be obtained when the photographer manually adjusts the focus to infinity. Can do.

  The image pickup apparatus according to the above embodiment includes a focus lens 102 that adjusts the focus of a subject image. Further, while the focus lens 102 is driven in the scanning range, the focus driving unit 115 and the image sensor 103 that receives a subject image formed by the focus lens 102 and converts it into an electric signal. Furthermore, it has the 1st extraction part 110 and the 2nd extraction part 111 which extract the signal which shows the high frequency component of the signal photoelectrically converted by the light-receiving surface of the image pick-up element 103 corresponding to a ranging area while driving the focus lens 102. . Furthermore, it has a focus position detection unit 112, a calculation storage unit 114, and a control unit 113 that detect the in-focus state of the focus lens 102 from a signal indicating a high-frequency component and drive the focus lens 102 to the focus position.

  If the subject is at infinity, the focusing state is detected by limiting the scanning range (focusing position scanning range) of the focus lens 102 when extracting a signal indicating a high frequency component. When the in-focus position is obtained, the focus lens 102 is driven to the in-focus position and the in-focus position for each photographing is stored.

  In this embodiment, when the in-focus position cannot be obtained, the farthest in-focus position at a plurality of infinite distances in the past is set as the in-focus position of the focus lens 102 (see FIG. Step # 503 of 5). The focus lens 102 is driven to the in-focus position.

  Alternatively, if a focus signal is not obtained, an average within the scanning range of the limited focus lens 102 is obtained from a plurality of past focus positions at infinity, and the average position is focused. Position (step # 403 in FIG. 4). The focus lens 102 is driven to the in-focus position.

  Alternatively, when the focus signal is not obtained, the position of the focus lens 102 corresponding to infinity is statistically obtained from a plurality of past focus positions at infinity, and the position is determined as the focus position. (Steps # 405 to # 408 in FIG. 4 and Step # 505 in FIG. 5). The focus lens 102 is driven to the in-focus position.

  In this embodiment, the storage of the plurality of in-focus positions for each photographing when the in-focus signal is obtained is reset after a certain time has elapsed or a certain temperature change (# 302 to # 305). ing.

  In this embodiment, the limit of the scanning range of the focus lens 102 is set according to at least one of the zoom position and the aperture value of the imaging apparatus.

  The case where the subject is at infinity is when a specific scene mode for shooting at infinity is set, or when the subject distance is set at infinity by manual operation. .

(Correspondence between the present invention and the embodiment)
The focus lens 102 corresponds to the focus lens of the present invention, the focus driving unit 115 corresponds to the driving unit, the imaging element 103 corresponds to the imaging unit, and the first extraction unit 110 and the second extraction unit 111 correspond to the extraction unit. Further, the focus position detection unit 112, the calculation storage unit 114, and the control unit 113 correspond to the focus control means of the present invention.

  By using the imaging apparatus having the above-described configuration, the focus lens 102 can be set to an optimum in-focus position when the subject is at infinity.

It is a block diagram which shows the imaging device concerning one Example of this invention. It is a flowchart which shows the operation | movement at the time of focus position adjustment when the to-be-photographed object concerning the imaging device concerning one Example of this invention is set to infinity. It is a flowchart which shows the reset operation | movement of the stored value fixed point in the focus position adjustment concerning the imaging device concerning one Example of this invention. It is a flowchart which shows the calculation operation | movement of the memory | storage value fixed point concerning the imaging device concerning one Example of this invention. FIG. 5 is a flowchart for explaining another calculation example of stored value fixed points different from the calculation of stored value fixed points in FIG. 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Image pickup lens 102 Focus lens 103 Image pick-up element 109 Detection part 110 1st extraction part 111 2nd extraction part 112 Focus position detection part 113 Focus lens control part 114 Calculation memory | storage part 115 Focus lens drive part

Claims (8)

A focus lens that adjusts the focus of the subject image;
Driving means for driving the focus lens;
Imaging means for receiving a subject image formed by the focus lens and converting it into an electrical signal;
An extraction means for extracting a signal indicating a high-frequency component of a signal photoelectrically converted by a light receiving surface of the imaging means corresponding to a distance measurement area while the focus lens is driven in a scanning range;
A focus control unit that detects a focus state of the focus lens from a signal indicating the high-frequency component and drives the focus lens to a focus position;
When the subject is at infinity, the focus state is detected by limiting the scanning range of the focus lens when extracting the signal indicating the high frequency component, and the focus position is obtained In the imaging apparatus, the focus lens is driven to the in-focus position, and the in-focus position for each photographing is stored.   If the in-focus position is not obtained, the farthest in-focus position at the infinite distance in the past is set as the in-focus position, and the focus lens is driven to the in-focus position. The imaging apparatus according to claim 1.   When the in-focus signal is not obtained, an average is obtained from a plurality of in-focus positions at infinity in the scanning range of the focus lens, and the average position is determined as the in-focus position. The imaging apparatus according to claim 1, wherein the focus lens is driven to the in-focus position.   When the in-focus signal is not obtained, the position of the focus lens corresponding to infinity is statistically obtained from a plurality of in-focus positions at infinity in the past, and the position is set as the in-focus position. The imaging apparatus according to claim 1, wherein the focus lens is driven to the in-focus position.   The imaging apparatus according to claim 1, wherein the case where the subject is at infinity is a case where a specific scene mode for photographing infinity is set.   The imaging apparatus according to claim 1, wherein the case where the subject is at infinity is a case where the subject distance is set to infinity by a manual operation.   The imaging apparatus according to claim 1, wherein the memory of the focus position for each photographing when the focus signal is obtained is reset after a certain time has elapsed or a certain temperature change.   The imaging apparatus according to claim 1, wherein the limit of the scanning range of the focus lens is set according to at least one of a zoom position and an aperture value of the imaging apparatus.

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