JP2000292683A - Imaging device and automatic focusing control method - Google Patents

Abstract

(57) [Problem] To provide an imaging device capable of performing distance measurement at high speed and with high accuracy regardless of a set value of an aperture. In the AF control of the image pickup apparatus, a drive amount of a focus lens is set and driven according to whether or not a relational expression of aperture value ≧ predetermined value is satisfied, and the focus lens is driven by a corresponding drive amount. Is stored while the focus evaluation value and the position of the focus lens 101 are repeatedly stored until the position of the focus lens 101 reaches the scan end position (steps S302 to S307). When the position of the focus lens 101 reaches the scan end position,
The position of the focus lens 101 indicating the maximum value among the stored focus evaluation values is extracted, and the focus position is determined based on the extracted maximum value or the interpolation result of the focus evaluation value.
The focus lens 101 is moved to the position (steps S308 to 611).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image pickup apparatus for automatically focusing a focus lens for adjusting the focus of a subject image and an automatic focusing control method used for the same.

[0002]

2. Description of the Related Art Conventionally, in an image pickup apparatus such as an electronic still camera or a video camera, a focus control method in which a lens position at which a high frequency component of a luminance signal obtained from an image pickup device such as a CCD becomes a maximum is a focus position. Used. That is, this focus control method stores a high-frequency component (hereinafter, referred to as a focus evaluation value) of a luminance signal obtained from an image sensor while driving a lens over the entire range of a distance measurement range, and stores a maximum value of the stored values. The lens position indicating the value is set as the focus position.

[0003] This method will be described with reference to FIGS. 8 to 10. FIG. 8 is a diagram showing a distance measurement area in a shooting screen in a conventional imaging device focusing control method, FIG. 9 is a diagram showing a relationship between a lens position and a focus evaluation value in a conventional imaging device focusing control method, FIG. 10 is a diagram showing a relationship between a focus evaluation value and a sampling point with respect to a lens position in a focusing control method of a conventional imaging apparatus.

In the above-described method, as shown in FIG. 8, a center portion of a photographing screen is usually used as a distance measuring area, and a lens position at which a focus evaluation value is maximized for a subject within this range is focused on. And position. The relationship between the lens position and the focus evaluation value obtained in this way is represented by a mountain-shaped curve as shown in FIG.

In this method, in order to shorten the distance measurement time, the entire area is scanned by increasing the interval between lens positions for obtaining focus evaluation values. That is, as shown in FIG. 10, the whole area is scanned with the sampling interval being coarse,
The interval between the sampling points is set uniformly from infinity to the nearest. The focus evaluation value is obtained by interpolation calculation for the points between the respective sampling points. Here, black points in FIG. 10 indicate sampling points, and dotted lines indicate stop positions of the focus lens.

[0006]

When the aperture is set near the maximum aperture, the depth of field becomes shallow, and higher precision ranging is required. However, in the above-described conventional focus control method, since the interval between sampling points is uniform, if an aperture value that reduces the depth of field is selected, distance measurement can be performed with high accuracy. In some cases, a phenomenon that the focus becomes so sweet may occur. That is, there is a possibility that the accuracy of the distance measurement may be reduced according to the set value of the aperture.

When a zoom lens is mounted,
Depending on the zoom position, the amount of movement of the focus lens from infinity to close range may change. In such a case, when the interval between the sampling points is uniform as in the above-described conventional focus control method, the telephoto side where the moving amount of the focus lens is large and the sampling points are large is larger than the wide side. The distance measurement time becomes longer. That is,
The distance measurement time changes depending on the zoom position.

An object of the present invention is to provide an image pickup apparatus and an automatic focusing control method capable of performing distance measurement at high speed and with high accuracy irrespective of the aperture setting value.

Another object of the present invention is to provide an image pickup apparatus and an automatic focusing control method capable of performing distance measurement at high speed and with high accuracy irrespective of a set angle of view of a zoom lens.

[0010]

According to the first aspect of the present invention,
An optical lens including a focus lens for adjusting a focus of a subject image, a focus lens driving unit for driving the focus lens, and a photoelectric conversion for converting the subject image formed via the focus lens into an electric signal and outputting the electric signal Means, extraction means for extracting a signal indicating a high-frequency component of the luminance of the subject image based on the electric signal output from the photoelectric conversion means, and aperture means for limiting the amount of light received from the subject image to the photoelectric conversion means And control means for controlling the focus lens drive means, wherein the control means sets a drive amount of the focus lens according to a set value of the aperture means, and a predetermined value is set based on the set drive amount. Processing for controlling the focus lens driving means to drive the focus lens over a range;
A process of determining a focus position according to an output signal of the extraction means obtained for each drive of the focus lens by the set drive amount, and driving the focus lens to the determined focus position. And controlling the focus lens driving means.

According to a second aspect of the present invention, in the imaging apparatus according to the first aspect, when the set value of the aperture means is equal to or more than a predetermined value, the control means sets a first drive amount as a drive amount of the focus lens. A process of setting an amount, a process of controlling the focus lens driving means so as to drive the focus lens with the first drive amount over a predetermined range, and a process of driving the focus lens by the first drive amount. Executing a process of determining a focus position in accordance with the obtained output signal of the extraction unit, and a process of controlling the focus lens driving unit to drive the focus lens to the determined focus position; Setting a second driving amount different from the first driving amount as the driving amount of the focus lens when the set value of the aperture means is less than the predetermined value; Processing for controlling the focus lens driving means so as to drive the focus lens over the predetermined range with the second drive amount, and an output of the extraction means obtained each time the focus lens is driven by the second drive amount A process for determining a focus position in accordance with a signal and a process for controlling the focus lens driving means to drive the focus lens to the determined focus position are executed.

According to a third aspect of the present invention, in the imaging apparatus according to the second aspect, the control means drives the focus lens by the first drive amount when a set value of the aperture means is equal to or greater than a predetermined value. A process of interpolating the output signal of the extraction means obtained every time is performed, and based on the output signal of the extraction means obtained every time the focus lens is driven by the first drive amount and the result of the interpolation, The focus position is determined.

The invention according to claim 4 is the invention according to claim 2 or 3.
The imaging device according to claim 1, wherein the first drive amount is smaller than the second drive amount.

[0014] The invention according to claim 5 provides the invention according to claims 1 to 4.
The imaging device according to any one of the above, wherein the set value of the aperture means is an aperture diameter of the aperture.

According to a sixth aspect of the present invention, there is provided an optical lens including a focus lens for adjusting a focus of a subject image and a zoom lens for changing an angle of view of a photographing screen; a focus lens driving means for driving the focus lens; A photoelectric conversion unit that converts a subject image formed through a focus lens into an electric signal and outputs the signal, and extracts a signal indicating a high-frequency component of luminance of the subject image based on the electric signal output from the photoelectric conversion unit Extracting means, and control means for controlling the focus lens driving means, wherein the control means sets a driving amount of the focus lens according to an angle of view of the zoom lens; Controlling the focus lens driving means to drive the focus lens over a predetermined range by an amount; Determining a focus position in accordance with an output signal of the extraction means obtained each time the focus lens is driven by the determined drive amount, and driving the focus lens to the determined focus position. And a process of controlling the driving means.

According to a seventh aspect of the present invention, in the imaging apparatus according to the sixth aspect, when the angle of view of the zoom lens is equal to or greater than a predetermined angle, the control means sets a first drive amount as a drive amount of the focus lens. A process of setting an amount, a process of controlling the focus lens driving means so as to drive the focus lens with the first drive amount over a predetermined range, and a process of driving the focus lens by the first drive amount. Executing a process of determining a focus position in accordance with the obtained output signal of the extraction unit, and a process of controlling the focus lens driving unit to drive the focus lens to the determined focus position; When the angle of view of the zoom lens is less than the predetermined angle, a second drive amount different from the first drive amount is used as the drive amount of the focus lens.
Setting the driving amount of the focus lens, controlling the focus lens driving means so as to drive the focus lens over the predetermined range with the second driving amount, and driving the focus lens by the second driving amount. Executing a process of determining a focus position in accordance with an output signal of the extraction unit obtained every time, and a process of controlling the focus lens driving unit to drive the focus lens to the determined focus position. It is characterized by the following.

According to an eighth aspect of the present invention, in the imaging apparatus according to the seventh aspect, when the angle of view of the zoom lens is smaller than a predetermined angle, the control means drives the focus lens by the second drive amount. A process of interpolating the output signal of the extraction means obtained every time is performed, and the sum is obtained based on the output signal of the extraction means obtained every time the focus lens is driven by the second drive amount and the interpolation result. The focus position is determined.

The ninth aspect of the present invention is the seventh or eighth aspect.
The imaging device according to claim 1, wherein the first drive amount is smaller than the second drive amount.

According to a tenth aspect of the present invention, in the imaging apparatus according to the seventh or eighth aspect, the predetermined angle is an angle of view for distinguishing between a wide angle side and a telephoto side.

According to an eleventh aspect of the present invention, there is provided an optical lens including a focus lens for adjusting a focus of a subject image, a focus lens driving means for driving the focus lens, and a subject image formed via the focus lens. In an automatic focusing control method for an image pickup apparatus, comprising: a photoelectric conversion unit that converts and outputs an electric signal; and an aperture unit that limits an amount of light received from the subject image to the photoelectric conversion unit. And a step of performing focusing control according to the set value of the aperture means,
Focusing control according to the set value of the aperture means includes processing for setting a drive amount of the focus lens according to the set value of the aperture means, and controlling the focus lens over a predetermined range with the set drive amount. Processing for controlling the focus lens driving means so as to be driven, and extracting a high-frequency component of luminance of the subject image based on an electric signal output from the photoelectric conversion means each time the focus lens is driven by the set driving amount. And a process of determining a focus position in accordance with each of the extracted high-frequency components, and a process of controlling the focus lens driving unit to drive the focus lens to the determined focus position. And

According to a twelfth aspect of the present invention, in the automatic focusing control method according to the eleventh aspect, a first focusing control is performed when a set value of the aperture means is equal to or greater than a predetermined value, and When the set value is less than the predetermined value, the second
The first focus control includes a process of setting a first drive amount as a drive amount of the focus lens, and driving the focus lens over the predetermined range with the first drive amount. Controlling the focus lens driving means so that the high frequency components are extracted each time the focus lens is driven by the first drive amount, and a focus position is determined according to the extracted high frequency components. And controlling the focus lens driving unit to drive the focus lens to the determined focus position. The second focus control includes a first drive amount of the focus lens as a drive amount of the focus lens. Processing for setting a second drive amount different from the drive amount, and controlling the focus lens driving means so as to drive the focus lens with the second drive amount over a predetermined range. And processing that extracts the high frequency components for each driving of the focus lens by said second driving amount,
A process of determining a focus position according to each of the extracted high-frequency components, and a process of controlling the focus lens driving unit to drive the focus lens to the determined focus position. I do.

According to a thirteenth aspect of the present invention, in the automatic focusing control method according to the twelfth aspect, the first focusing control includes:
The method includes a process of interpolating a high-frequency component extracted every time the focus lens is driven by the first drive amount. Each high-frequency component extracted every time the focus lens is driven by the first drive amount and an interpolation result thereof The in-focus position is determined based on the in-focus position.

According to a fourteenth aspect of the present invention, in the automatic focusing control method according to the twelfth or thirteenth aspect, the first drive amount is smaller than the second drive amount.

According to a fifteenth aspect of the present invention, in the automatic focusing control method according to any one of the eleventh to fourteenth aspects, the set value of the aperture means is an aperture diameter of the aperture.

According to a sixteenth aspect of the present invention, there is provided an optical lens including a focus lens for adjusting a focus of a subject image and a zoom lens for changing an angle of view of a photographing screen; a focus lens driving means for driving the focus lens; An automatic focusing control method for an imaging apparatus, comprising: a photoelectric conversion unit that converts a subject image formed through a focus lens into an electric signal and outputs the electric signal; and a control unit that controls the focus lens driving unit. Determining the angle of view of the lens; and performing focusing control according to the angle of view of the zoom lens. The focusing control according to the angle of view of the zoom lens comprises: Setting the driving amount of the focus lens according to the driving amount, and driving the focus lens over a predetermined range with the set driving amount. Processing for controlling the focus lens driving means, and extracting the high frequency component of the luminance of the subject image based on the electric signal output from the photoelectric conversion means every time the focus lens is driven by the set driving amount, and The method includes a process of determining a focus position in accordance with each high-frequency component, and a process of controlling the focus lens driving unit to drive the focus lens to the determined focus position.

According to a seventeenth aspect of the present invention, in the automatic focusing control method according to the sixteenth aspect, when the angle of view of the zoom lens is equal to or larger than a predetermined angle, a first focusing control is performed.
When the angle of view of the zoom lens is less than a predetermined angle,
Performing a second focus control, wherein the first focus control includes a process of setting a first drive amount as a drive amount of a focus lens corresponding to an angle of view of the zoom lens; Processing for controlling the focus lens driving means so as to drive the focus lens over a predetermined range with a drive amount of 1; extracting the high-frequency components each time the focus lens is driven by the first drive amount; And a process of controlling the focus lens driving unit to drive the focus lens to the determined focus position, wherein the second focus control includes: As the driving amount of the focus lens, the first
Setting a second drive amount different from the second drive amount, controlling the focus lens driving unit so as to drive the focus lens over the predetermined range with the second drive amount, A process of extracting the high-frequency component each time the focus lens is driven by a drive amount, and determining a focus position according to the extracted high-frequency components; and driving the focus lens to the determined focus position. Controlling the focus lens driving means.

According to an eighteenth aspect of the present invention, in the automatic focusing control method according to the seventeenth aspect, the second focusing control includes:
The method includes a process of interpolating a high-frequency component extracted every time the focus lens is driven by the second drive amount. The high-frequency component extracted each time the focus lens is driven by the second drive amount and an interpolation result thereof are included. The in-focus position is determined based on the in-focus position.

According to a nineteenth aspect of the present invention, in the automatic focusing control method according to the seventeenth or eighteenth aspect, the first drive amount is smaller than the second drive amount.

According to a twentieth aspect of the present invention, in the automatic focusing control method according to the seventeenth or eighteenth aspect, the predetermined angle is an angle of view for distinguishing between a wide angle side and a telephoto side. And

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing a configuration of a first embodiment of an imaging apparatus according to the present invention.

The image pickup apparatus comprises an electronic still camera. As shown in FIG. 1, the electronic still camera is connected to an optical lens including a focus lens 101, an aperture / shutter 105 and a zoom lens 108 via the optical lens. An image sensor 116 composed of a CCD or the like that converts the formed subject image into an electric signal and a finder 112 are provided.

The focus lens 101 includes an image pickup device 11
6 is a lens for focusing on a photointerrupter 102 for detecting its initial position.
Is installed. The focus lens 101 is driven by a focus lens drive motor 103, and the focus lens drive motor 103 is a focus lens drive circuit 1.
Drive control is performed based on the drive signal from the drive circuit 04. The aperture / shutter 105 is driven by an aperture / shutter drive motor 106, and the aperture / shutter drive motor 106 is driven and controlled by a drive signal from an aperture / shutter drive circuit 107. The zoom lens 108 is a lens for changing the angle of view of a shooting screen, and has a photo interrupter 109 for detecting an initial position of the lens. The zoom lens 108 is driven by a zoom lens drive motor 110, and the drive of the zoom lens drive motor 110 is controlled based on a drive signal from a zoom lens drive circuit 111.

The image pickup device 116 operates based on the timing signal generated from the timing signal generation circuit 117, and outputs an electric signal obtained by subjecting the subject image to photoelectric conversion. This electric signal is input to the preprocessing circuit 118. The preprocessing circuit 118 includes a CDS circuit for removing noise included in the electric signal from the image sensor 116, a non-linear amplifier circuit for performing amplification before A / D conversion, and the like. Do. The signal after the preprocessing is input to the A / D converter 119 and is converted into digital image data by A / D conversion. This digital image data is temporarily written into the buffer memory 121 by the memory controller 120, and then stored in the recording medium I.
The data is written to a recording medium 123 such as a memory card or a hard disk via the / F 122.

The finder 112 is a finder with a zoom function capable of optically confirming the photographing range captured by the optical lens. The finder 112 has a photo interrupter 113 for detecting its initial position.
Is installed. The finder 112 is driven by a finder drive motor 114, and the finder drive motor 1
The drive 14 is controlled based on a drive signal from a finder drive circuit 115.

The focus lens drive circuit 103, aperture / shutter drive circuit 107, zoom lens drive circuit 1
11, finder drive circuit 115, timing signal generation circuit 117, memory controller 120, recording medium I /
Each block of F122 operates based on a control signal from a system control CPU (hereinafter, simply referred to as CPU) 124. The CPU 124 includes a zoom SW 125, a SW
(1) 126, SW (2) 127, main SW 128,
While monitoring the output of each of the photointerrupters 102, 109, and 113, a control signal for each of the above blocks is generated and output, and a photographing sequence and the like are executed based on the control signal. Here, the zoom SW 125 is a switch for instructing the CPU 124 to start or stop the zoom operation. SW (1) 126 is a switch for performing a shooting standby operation such as AF or AE, and SW (2)
Reference numeral 127 denotes a switch for issuing a shooting instruction after operating the SW (1) 126. The main SW 128 is a switch for turning on power to the apparatus.

The CPU 124 controls the operation display unit 129 so as to display setting conditions, an operation state display, various warning displays, and the like in a shooting sequence and the like. The operation display unit 129 includes an operation unit (not shown) having various buttons for setting a shooting mode and the like, in addition to a display unit (not shown) for performing each of the above-described displays.

Next, the main operation of the image pickup apparatus will be described with reference to FIG. FIG. 2 is a flowchart showing a procedure of a main operation in the imaging apparatus of FIG. The procedure of the main operation is executed by the CPU 124.

First, in step S201, the main S
When the main switch 128 is turned on, the process advances to step S202 to determine whether the remaining capacity of the recording medium 123 is zero. If the remaining capacity of the recording medium 123 is zero, the process proceeds to step S203, and a warning display indicating that the remaining capacity of the recording medium is zero is performed via the operation display unit 129. Here, instead of the warning display by the operation display unit 129, a warning sound may be emitted from a speaker and a warning may be issued by the warning sound. Alternatively, a warning display by the operation display unit 129 and a warning from the speaker may be performed. The warning may be issued using both the sound and the sound. Then, the process returns to step S201 again.

If the remaining capacity of the recording medium 123 is not zero, the flow advances to step S204 to perform a lens initialization process. In this process, the focus lens 101, the zoom lens 108, and the finder 112 are reset, and control is performed to move them to the initial position. Subsequently, the process proceeds to step S205 to determine whether or not the SW (1) 126 is on. If the SW (1) 126 is not on, the process proceeds to step S206 to determine whether or not the main SW 128 is on. . If the main switch 128 is not turned on, the process returns to step S201 and the main switch 12
If 8 is on, the process returns to step S205.

In the above step S205, SW (1) 126
Is determined to be ON, the process proceeds to step S207, and AE control is performed. In the AE control, the image sensor 11
The brightness of the subject is calculated from the output signal of No. 6, and parameters related to exposure control such as an aperture value and a shutter speed are determined according to the calculation result. In the following step S208,
Perform AF control. For details of this AF control, see FIG.
Will be described later.

Next, the flow advances to step S209 to switch SW
(2) It is determined whether or not 127 is ON, and SW (2) 1
If 27 is not on, the process proceeds to step S210, where SW
(1) It is determined whether 126 is on. SW
(1) If 126 is not on, the above step S205
Returning to step S209, if SW (1) 126 is on, the process returns to step S209.

In the above step S209, SW (2) 127
If it is determined that is turned on, the process proceeds to step S211 to perform a shooting process. For details of this shooting process,
It will be described later with reference to FIG.

Then, the process proceeds to a step S212, wherein it is determined whether or not the remaining capacity of the recording medium 123 is zero. When the remaining capacity of the recording medium 123 is zero, the above-described step S
Proceeding to 203, a warning display indicating that the remaining capacity of the recording medium is zero is performed via the operation display unit 129. Recording medium 1
If the remaining capacity of the switch 23 is not zero, the process proceeds to step S213, where it is determined whether or not the SW (2) 127 is on.
If W (2) 127 is on, wait for SW (2) 127 to be off. On the other hand, if SW (2) 127 is not on, that is, if it is off, the process proceeds to step S210 to determine whether SW (1) 126 is on.
If the SW (1) 126 is not on, the above step S2
05, if the SW (1) 126 is on, the process returns to step S209.

Next, the procedure of the AF control in step S208 will be described with reference to FIG. FIG. 3 is FIG.
6 is a flowchart showing a procedure of AF control in step S208.

In this AF control, as shown in FIG. 3, first, in step S301, the focus lens 101 is moved to a scan start position. Here, the scanning start position will be described as the infinity end of the focusable range. Note that this scan start position may be the closest end of the focusable range.

Then, the flow advances to step S302 to store the focus evaluation value (the calculated high-frequency component of the subject luminance) and the position of the focus lens 101. Here, in the present embodiment, it is assumed that a stepping motor is used as the focus lens driving motor 103, and in the case of using this stepping motor, the position of the focus lens 101 is determined from the initial position detected by the photo interrupter 102. It is detected as a relative position. When a DC motor is used as the focus lens driving motor 103, an absolute value of the position of the focus lens 101 is obtained using an encoder (not shown).

In the following step S303, it is determined whether or not the position of the focus lens 101 is at the scan end position. Here, since the scan start position is at the infinity end, the scan end position is the closest end. In addition,
Conversely, if the scan start position is the closest end, the scan end position is the infinite end.

If the position of the focus lens 101 is not at the scan end position, the flow advances to step S305 to determine whether or not the relational expression of aperture aperture ≧ predetermined value is satisfied. If the relational expression of aperture opening diameter ≧ predetermined value is satisfied, it is determined that the depth of field is shallow, and the process advances to step S306 to move the focus lens 101 by a driving amount of m pulses, and the relationship of aperture opening diameter ≧ predetermined value is satisfied. If the formula does not hold, it is determined that the depth of field is not shallow, and the flow advances to step S307 to move the focus lens 101 by a drive amount for n pulses. Here, the drive pulse numbers n and m are set so as to satisfy the relationship of n> m. Then, the process returns to step S302 again. That is, driving of the focus lens 101 with a drive amount corresponding to the aperture diameter of the focus and storage of the focus evaluation value and the position of the focus lens 101 are repeatedly performed until the position of the focus lens 101 reaches the scan end position.

When the position of the focus lens 101 reaches the scan end position, the process proceeds to step S304, where the focus lens 1 indicating the maximum value among the stored focus evaluation values is set.
01 is extracted, and in a succeeding step S308, it is determined whether or not a relational expression of aperture diameter ≧ predetermined value is satisfied.
If the relational expression of aperture diameter ≧ predetermined value is not satisfied, the flow advances to step S311 to move the focus lens 101 to the position indicating the extracted maximum value as the in-focus position and exit this processing.

On the other hand, if it is determined in step S308 that the relational expression of aperture aperture ≧ predetermined value is satisfied, the process proceeds to step S309, where the focus corresponding to the lens position that has not been sampled based on the stored focus evaluation value. The evaluation value is calculated by interpolation, and the subsequent step S310
Then, the position of the focus lens 101 showing the maximum value is extracted from the focus evaluation value stored in step S302 and the focus evaluation value calculated by interpolation. Next, the process proceeds to step S311, the extracted position is set as a focus position, the focus lens 101 is moved to the position, and the process exits.

In the above processing, the number of sampling points for obtaining the focus evaluation value is changed by changing the drive amount according to whether or not the relational expression of aperture aperture ≧ predetermined value is satisfied. The difference in the number of sampling points between the case where the relational expression of the aperture opening diameter ≧ the predetermined value is established and the case where the relational expression is not established will be described with reference to FIG. FIG. 5 shows A in FIG.
FIG. 9 is a diagram illustrating sampling points of a focus evaluation value during F control.

When the relational expression of aperture aperture ≧ predetermined value is satisfied, that is, when the depth of field is shallow, the focus lens 101 is moved by the driving amount of m pulses as described above (step S306). Here, FIG. 5A shows an example in which the number of pulses m is set to 2 and scanning is performed. In FIG. 5A, a black point indicates a sampling point of the focus evaluation value,
The dotted line indicates the driving amount of the focus lens 101 for one pulse. On the other hand, when the relational expression of “diaphragm opening diameter ≧ predetermined value” is not satisfied, that is, when the depth of field is not shallow, the focus lens 101 is moved by the driving amount for n pulses as described above (step S307). . Here, FIG. 5B shows an example in which the pulse number n is set to 3 and scanning is performed. In FIG. 5B, a black point indicates a sampling point of the focus evaluation value, and a dotted line indicates a driving amount for one pulse.

As described above, when the relational expression of aperture diameter ≧ predetermined value is satisfied, that is, when the depth of field is shallow, scanning is performed with the number of driving steps of the focus lens 101 reduced. In other words, the sampling interval (m = 2)
Is narrowed. On the other hand, when the relational expression of “aperture opening diameter ≧ predetermined value” is not satisfied, that is, when the depth of field is not shallow, scanning is performed with a smaller number of drive steps of the focus lens 101. In other words, the sampling interval (n = 3) is widened.

When the relational expression of aperture diameter ≧ predetermined value is satisfied, that is, when the depth of field is shallow, the focus evaluation value corresponding to the position of the focus lens 101 which is not actually read is calculated by interpolation. Then, the maximum focus evaluation value is extracted from those including the actually sampled focus evaluation value and the result of the interpolation, and the position corresponding to this maximum focus evaluation value is set as the in-focus position, and the focus lens 101 is determined.
Is moved (steps S309 to S311). If the relational expression of aperture diameter ≧ predetermined value is not satisfied, that is, if the depth of field is not shallow, the largest focus evaluation value among the focus evaluation values corresponding to the actually read position of the focus lens 101 without performing interpolation. A focus evaluation value is extracted, and a position corresponding to the maximum focus evaluation value is set as a focus position.
01 is moved (step S311). In this case,
Even if the actual focus position is on a point where sampling is not performed, the depth of field is deep, so that the defocus of the captured image does not pose a practical problem.

As described above, when the aperture diameter is equal to or larger than the predetermined value, that is, when the depth of field is shallow, the interval between the sampling points of the focus evaluation value is reduced and the interpolation of the focus evaluation value is performed. Distance measurement can be performed. On the other hand, when the aperture diameter is smaller than the predetermined value, that is, when the depth of field is not shallow, the interval between the sampling points of the focus evaluation value is widened, so that it is possible to perform faster distance measurement. The accuracy of distance measurement is not reduced.

Next, the photographing process in step S211 in FIG. 2 will be described with reference to FIG. FIG. 4 is a flowchart showing the procedure of the photographing process in step S211 in FIG.

In the photographing process, as shown in FIG. 4, AE control is first performed in step S401. Here, FIG.
The parameters related to the exposure control such as the aperture value and the shutter speed determined in step S207 shown in FIG. In a succeeding step S402, white balance control is performed.

Next, the process proceeds to step S403, where exposure to the image sensor 116 is performed, and in step S404, data stored from the image sensor 116 is read.

Next, the process proceeds to step S405, where a pre-process is performed. In this processing, output noise removal of the image sensor 116 and non-linear processing before A / D conversion are performed by the preprocessing circuit 118. In the following step S406, the analog signal from the pre-processing circuit 118 is converted into digital image data by the A / D converter 119, and then in step S407.
The digital image data is subjected to various image processing including gamma conversion processing and color conversion processing.

Next, in step S408, the digital image data after image processing is subjected to a compression process in accordance with a predetermined compression format such as JPEG, and in step S409, the compressed data is stored in the memory controller 120 and the recording medium I / O. Recording medium 123 via F122
And exit the process.

In this embodiment, interpolation is not performed when the aperture diameter is smaller than a predetermined value. However, interpolation may be performed. As a result, even when the sampling interval is widened, highly accurate ranging can be performed without lengthening the ranging time.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 6 is a flowchart showing the procedure of AF control in the second embodiment of the imaging apparatus of the present invention, and FIG. 7 shows sampling points of focus evaluation values during AF control in the second embodiment of the imaging apparatus of the present invention. FIG.

This embodiment is different from the first embodiment in that the first embodiment employs the AF control which changes the sampling point interval of the focus evaluation value according to the aperture diameter of the aperture and interpolates the focus evaluation value. On the other hand, the difference is that AF control for changing the sampling point interval of the focus evaluation value according to the position (angle of view) of the zoom lens and interpolating the focus evaluation value is employed. Note that the present embodiment has the same configuration as the above-described first embodiment, and the main operation procedure is the same as the above-described first embodiment. Omitted.

In the AF control according to the present embodiment, FIG.
As shown in (1), first, in step S601, the focus lens 101 is moved to the scan start position. Here, as in the first embodiment described above, the scan start position is described as the infinity end of the focusable range.

Then, the flow advances to step S602 to store the focus evaluation value and the position of the focus lens 101.
Here, in the present embodiment, it is assumed that a stepping motor is used as the focus lens drive motor 103, and the position of the focus lens 101 is detected in the same manner as in the first embodiment.

In the following step S603, it is determined whether or not the position of the focus lens 101 is at the scan end position. Here, since the scan start position is at the infinity end, the scan end position is the closest end. In addition,
Conversely, if the scan start position is the closest end, the scan end position is the infinite end.

If the position of the focus lens 101 is not at the scan end position, the flow advances to step S605 to determine whether a relational expression of zoom position ≧ predetermined value is satisfied. Here, the above relational expression indicates that the value indicating the position (angle of view) of the zoom lens 108 is equal to or more than a predetermined value, and the larger the value indicating the position (angle of view) of the zoom lens 108, the larger the zoom lens It is assumed that the position (angle of view) 108 is on the wide side. Therefore, when this relational expression is established, it indicates that the position (angle of view) of the zoom lens 108 is relatively on the wide side.

When the relational expression of zoom position ≧ predetermined value is satisfied, it is determined that the position (angle of view) of the zoom lens 108 is on the wide side, and the flow advances to step S606 to move the focus lens 101 with the driving amount for m pulses. If the relational expression of zoom position ≧ predetermined value is not established, it is determined that the position (angle of view) of the zoom lens 108 is not on the wide side, and the process advances to step S607 to drive the focus lens 101 by n pulses. Move with. Here, the pulse numbers n and m are set so as to satisfy the relationship of n> m.
For example, the number m of drive pulses is set to 1, and n is set to 3.

After the focus lens 101 is driven by the corresponding drive amount, the process returns to step S602 again, where the focus evaluation value and the position of the focus lens 101 are stored, and the focus lens 101 is driven by the corresponding drive amount. Are repeated until the position of the focus lens 101 reaches the scan end position.

When the position of the focus lens 101 reaches the scan end position, the process proceeds to step S604, where the focus lens 1 indicating the maximum value among the stored focus evaluation values is set.
01 is extracted, and in a succeeding step S608, it is determined whether or not a relational expression of zoom position ≧ predetermined value is satisfied.
If the relational expression of zoom position ≧ predetermined value is not established, the process proceeds to step S611, the focus lens 101 is moved to the position indicating the extracted maximum value as the in-focus position, and the process exits.

On the other hand, when it is determined in step S608 that the relational expression of zoom position ≧ predetermined value is established, the process proceeds to step S609, where the focus evaluation corresponding to the lens position that is not sampled based on the stored focus evaluation value. The value is calculated by interpolation, and the following step S610
Then, the position of the focus lens 101 showing the maximum value is extracted from the focus evaluation value stored in step S602 and the focus evaluation value calculated by interpolation. Next, the process proceeds to step S611, where the extracted position is set as the focus position, the focus lens 101 is moved to the position, and the process exits.

In the above processing, the focus lens 1 is determined according to whether or not the relational expression of zoom position ≧ predetermined value is satisfied.
By changing the driving amount of 01, the number of sampling points of the focus evaluation value is changed. The difference in the number of sampling points between when the relational expression of zoom position ≧ predetermined value is satisfied and when it is not satisfied will be described with reference to FIG.

When the relational expression of zoom position ≧ predetermined value is satisfied, that is, when the position of the zoom lens 108 is on the wide side, as described above, the focus lens 101
Is moved by a drive amount of m (= 1) pulses (step S).
606). FIG. 7A shows an example in which the number of drive pulses m is set to 1 and scanning is performed. In FIG. 7A, a black point indicates a sampling point of the focus evaluation value, and a dotted line indicates a driving amount of the focus lens 101 for one pulse. In other words, when the position of the zoom lens 108 is on the wide side, the number of positions at which the focus lens 101 can be stopped is small.
And the focus evaluation value is obtained and stored each time the focus lens 101 is driven by a drive amount for one pulse.

On the other hand, when the relational expression of zoom position ≧ predetermined value is not satisfied, that is, when the position of the focus lens 101 is located on the telephoto side, as described above, the focus lens 101 is driven with the driving amount for n pulses. Move (step S607). Here, FIG. 7B shows an example in which the number of pulses n is set to 3 and scanning is performed. In FIG. 7B, a black point indicates a sampling point of the focus evaluation value, and a dotted line indicates a driving amount for one pulse. That is, the zoom lens 1
When the position 08 is located on the telephoto side, the number of stopable positions of the focus lens 101 is large. Therefore, the number m of drive pulses of the focus lens 101 is set to 3 and the focus lens 101 is driven with a drive amount of 3 pulses. A focus evaluation value is obtained and stored each time the motor is driven. In this case, the distance between the sampling points of the focus evaluation value is widened to speed up the distance measurement.

Further, when the relational expression of zoom position ≧ predetermined value is not satisfied, that is, when the zoom lens 108 is located on the telephoto side, the focus evaluation value corresponding to the position of the focus lens 101 which is not actually read is interpolated. The maximum focus evaluation value is extracted from the calculated and actually sampled focus evaluation values including the interpolation result, and the focus lens 101 is moved with the position corresponding to the maximum focus evaluation value as the focus position. (Steps S609 to S61
1). By this interpolation, even if the actual sampling point interval is wide, high-accuracy ranging can be performed without impairing the high-speed ranging.

In this embodiment, when the relational expression of zoom position ≧ predetermined value is satisfied, that is, the zoom lens 10
8 is located on the wide side, the focus lens 1
Although the drive pulse number n of 01 is set to 1, it can be set to a number larger than 1 and smaller than m. In this case, it is expected that the ranging accuracy will be reduced, but when the zoom position is on the wide side, there is no danger of a practical problem because the depth of field is deep.

[0078]

As described above, according to the imaging apparatus of the present invention, the optical lens including the focus lens for adjusting the focus of the subject image, the focus lens driving means for driving the focus lens, and the focus lens Photoelectric conversion means for converting the formed subject image into an electric signal and outputting the electric signal, and extracting means for extracting a signal indicating a high-frequency component of the luminance of the subject image based on the electric signal output from the photoelectric conversion means, An aperture unit for limiting the amount of light received from the subject image to the photoelectric conversion unit; and a control unit for controlling the focus lens driving unit, wherein the control unit sets the driving amount of the focus lens according to the set value of the aperture unit. Processing, and controlling the focus lens driving means to drive the focus lens over a predetermined range with the set driving amount; Determining the focus position in accordance with the output signal of the extraction means obtained for each drive of the focus lens by the determined drive amount, and controlling the focus lens drive means to drive the focus lens to the determined focus position Therefore, the distance measurement can be performed at high speed and with high accuracy regardless of the aperture setting value.

According to the imaging apparatus of the present invention, an optical lens including a focus lens for adjusting the focus of a subject image and a zoom lens for changing the angle of view of a photographing screen, a focus lens driving unit for driving the focus lens, and a focus lens Photoelectric conversion means for converting a subject image formed through a lens into an electric signal and outputting the electric signal, and extracting means for extracting a signal indicating a high-frequency component of luminance of the subject image based on the electric signal output from the photoelectric conversion means And a control means for controlling the focus lens driving means, wherein the control means sets a driving amount of the focus lens according to an angle of view of the zoom lens, and focuses over a predetermined range with the set driving amount. Processing for controlling the focus lens driving means to drive the lens, and driving of the focus lens by the set driving amount Since a process of determining a focus position according to the output signal of the extraction unit obtained in step (a) and a process of controlling the focus lens driving unit to drive the focus lens to the determined focus position are executed, the zoom lens Irrespective of the set angle of view, distance measurement can be performed at high speed and with high accuracy.

According to the automatic focusing control method of the present invention, the method includes the step of determining the set value of the aperture means and the step of performing focusing control according to the set value of the aperture means. The focusing control according to the above is a process of setting the drive amount of the focus lens according to the set value of the aperture unit, and controlling the focus lens drive unit to drive the focus lens over a predetermined range with the set drive amount. And extracting a high-frequency component of the luminance of the subject image based on the electric signal output from the photoelectric conversion means for each drive of the focus lens according to the set driving amount, and adjusting the focus position according to each of the extracted high-frequency components. And the process of controlling the focus lens driving means so as to drive the focus lens to the determined in-focus position, so that distance measurement can be performed at high speed and with high accuracy regardless of the aperture setting value. Ukoto can.

According to the automatic focusing control method of the present invention, the method includes the step of determining the angle of view of the zoom lens and the step of performing focusing control according to the angle of view of the zoom lens. The focusing control according to is performed by setting a drive amount of the focus lens according to the angle of view of the zoom lens, and controlling the focus lens driving unit to drive the focus lens over a predetermined range with the set drive amount. And extracting a high-frequency component of the luminance of the subject image based on the electric signal output from the photoelectric conversion means for each drive of the focus lens according to the set driving amount, and adjusting the focus position according to each of the extracted high-frequency components. And a process of controlling the focus lens driving means so as to drive the focus lens to the determined focus position, so that the distance measurement is performed regardless of the set angle of view of the zoom lens. It can be performed quickly and accurately.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a first embodiment of an imaging apparatus according to the present invention.

FIG. 2 is a flowchart illustrating a procedure of a main operation in the imaging apparatus of FIG. 1;

FIG. 3 is a flowchart showing a procedure of AF control in step S208 of FIG. 2;

FIG. 4 is a flowchart illustrating a procedure of a photographing process in step S211 of FIG. 2;

FIG. 5 is a diagram illustrating sampling points of focus evaluation values during the AF control of FIG. 3;

FIG. 6 shows A in the second embodiment of the imaging apparatus of the present invention.
It is a flowchart which shows the procedure of F control.

FIG. 7 is a diagram illustrating sampling points of focus evaluation values during AF control according to the second embodiment of the imaging apparatus of the present invention.

FIG. 8 is a diagram illustrating a distance measurement area in a shooting screen in a focusing control method of a conventional imaging apparatus.

FIG. 9 is a diagram illustrating a relationship between a lens position and a focus evaluation value in a focusing control method of a conventional imaging apparatus.

FIG. 10 is a diagram illustrating a relationship between a focus evaluation value and a sampling point with respect to a lens position in a focusing control method of a conventional imaging apparatus.

[Explanation of symbols]

 Reference Signs List 101 focus lens 104 focus lens drive circuit 105 aperture / shutter 107 aperture / shutter circuit 108 zoom lens 111 zoom lens drive circuit 116 image sensor 124 system control CPU

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H011 AA06 BA33 BB03 CA21 DA00 DA01 2H051 AA00 BA45 BA47 BA66 CB22 CE14 CE20 CE26 CE27 DA01 DA10 DA11 DA26 DA31 DA34 DB06 DB10 EA02 EA08 EA09 EA10 EA11 EA13 EB01 FA04 FA76

Claims (20)

[Claims] 1. An optical lens including a focus lens for adjusting a focus of a subject image, a focus lens driving unit for driving the focus lens, and converting an object image formed via the focus lens into an electric signal. Means for extracting a signal indicating a high-frequency component of the luminance of the subject image based on the electric signal output from the photoelectric conversion means, and the amount of light received from the subject image to the photoelectric conversion means Aperture means for restricting
Control means for controlling the focus lens drive means, wherein the control means sets a drive amount of the focus lens according to a set value of the aperture means, and sets the drive amount to a predetermined range with the set drive amount. Controlling the focus lens driving means so as to drive the focus lens, and determining a focus position according to an output signal of the extraction means obtained every time the focus lens is driven by the set driving amount. An image capturing apparatus that executes a process of performing the following operation and a process of controlling the focus lens driving unit to drive the focus lens to the determined focus position. 2. The method according to claim 1, wherein the control unit sets a first drive amount as a drive amount of the focus lens when the set value of the stop unit is equal to or more than a predetermined value. A process of controlling the focus lens driving means so as to be driven over a predetermined range by a drive amount, and a focus position according to an output signal of the extraction means obtained each time the focus lens is driven by the first drive amount. Performing a process of determining, and a process of controlling the focus lens driving unit so as to drive the focus lens to the determined in-focus position, wherein when a set value of the aperture unit is less than the predetermined value, A process of setting a second drive amount different from the first drive amount as the drive amount of the focus lens, and moving the focus lens over the predetermined range by the second drive amount. Controlling the focus lens driving means so as to drive the focus lens; determining the focus position according to an output signal of the extraction means obtained each time the focus lens is driven by the second drive amount; And controlling the focus lens driving means so as to drive the focus lens to the determined in-focus position. 3. A process for interpolating an output signal of the extracting means obtained every time the focus lens is driven by the first drive amount, when the set value of the diaphragm means is equal to or more than a predetermined value. 3. The in-focus position is determined on the basis of an output signal of the extraction unit obtained every time the focus lens is driven by the first drive amount and an interpolation result thereof. Imaging device. 4. The imaging device according to claim 2, wherein the first drive amount is smaller than the second drive amount. 5. The imaging apparatus according to claim 1, wherein the setting value of the diaphragm means is an aperture diameter of the diaphragm. 6. An optical lens including a focus lens for adjusting a focus of a subject image and a zoom lens for changing an angle of view of a shooting screen, a focus lens driving unit for driving the focus lens, and a lens connected via the focus lens. A photoelectric conversion unit that converts the formed subject image into an electric signal and outputs the signal, an extraction unit that extracts a signal indicating a high-frequency component of luminance of the subject image based on the electric signal output from the photoelectric conversion unit, Control means for controlling a focus lens drive means, wherein the control means sets a drive amount of the focus lens in accordance with an angle of view of the zoom lens, and controls the drive amount over a predetermined range with the set drive amount. Processing for controlling the focus lens driving means so as to drive the focus lens; A process of determining a focus position according to an output signal of the extraction unit obtained for each drive of the focus lens, and a process of controlling the focus lens driving unit to drive the focus lens to the determined focus position And an imaging device. 7. When the angle of view of the zoom lens is equal to or more than a predetermined angle, the control unit sets a first drive amount as a drive amount of the focus lens; A process of controlling the focus lens driving means so as to be driven over a predetermined range by a drive amount, and a focus position according to an output signal of the extraction means obtained each time the focus lens is driven by the first drive amount. Performing a process of determining, and a process of controlling the focus lens driving unit to drive the focus lens to the determined in-focus position, wherein when the angle of view of the zoom lens is less than the predetermined angle, A process of setting a second drive amount different from the first drive amount as a drive amount of the focus lens; A process of controlling the focus lens driving means so as to drive over a range, and a process of determining a focus position according to an output signal of the extraction means obtained each time the focus lens is driven by the second drive amount. ,
7. The image pickup apparatus according to claim 6, further comprising: controlling the focus lens driving unit so as to drive the focus lens to the determined focus position. 8. A process for interpolating an output signal of said extracting means obtained every time the focus lens is driven by said second drive amount, when said angle of view of said zoom lens is smaller than a predetermined angle. 8. The in-focus position is determined on the basis of an output signal of the extraction unit obtained every time the focus lens is driven by the second drive amount and an interpolation result thereof. Imaging device. 9. The imaging apparatus according to claim 7, wherein the first drive amount is smaller than the second drive amount. 10. The imaging apparatus according to claim 7, wherein the predetermined angle is an angle of view for distinguishing between a wide angle side and a telephoto side. 11. An optical lens including a focus lens for adjusting the focus of a subject image, a focus lens driving unit for driving the focus lens, and converting the subject image formed via the focus lens into an electric signal. A photoelectric conversion means for outputting the image data, and an automatic focusing control method for an image pickup apparatus comprising an aperture means for limiting the amount of light received from the subject image to the photoelectric conversion means, wherein a step of determining a set value of the aperture means; Performing focusing control according to the set value of the aperture means, wherein the focus control according to the set value of the aperture means controls the drive amount of the focus lens according to the set value of the aperture means. Processing for setting the focus lens driving means so as to drive the focus lens over a predetermined range with the set drive amount; Extracting a high-frequency component of the luminance of the subject image based on the electric signal output from the photoelectric conversion unit every time the focus lens is driven by the determined drive amount,
The method includes a process of determining a focus position according to each of the extracted high-frequency components, and a process of controlling the focus lens driving unit to drive the focus lens to the determined focus position. Automatic focusing control method. 12. A first focusing control is performed when the set value of the diaphragm is equal to or more than a predetermined value, and a second focusing control is performed when the set value of the diaphragm is less than a predetermined value. The first focus control includes: setting a first drive amount as a drive amount of the focus lens; and controlling the focus lens so as to drive the focus lens over the predetermined range with the first drive amount. A process of controlling a driving unit; a process of extracting the high-frequency component each time the focus lens is driven by the first drive amount; and a process of determining a focus position according to each of the extracted high-frequency components; Controlling the focus lens driving means to drive the focus lens to a focus position, wherein the second focus control differs from the first drive amount by a drive amount of the focus lens. A second drive amount, a process of controlling the focus lens driving means to drive the focus lens over the predetermined range with the second drive amount, and a focus by the second drive amount. A process of extracting the high-frequency component each time the lens is driven and determining a focus position according to each of the extracted high-frequency components; and driving the focus lens to drive the focus lens to the determined focus position. 12. The automatic focusing control method according to claim 11, further comprising a step of controlling the means. 13. The first focus control includes a process of interpolating a high-frequency component extracted each time the focus lens is driven by the first drive amount, and driving the focus lens by the first drive amount. 13. The automatic focusing control method according to claim 12, wherein the in-focus position is determined based on each high-frequency component extracted every time and an interpolation result thereof. 14. The automatic focusing control method according to claim 12, wherein the first drive amount is smaller than the second drive amount. 15. The automatic focusing control method according to claim 11, wherein the set value of the diaphragm means is an aperture diameter of the diaphragm. 16. An optical lens including a focus lens for adjusting a focus of a subject image and a zoom lens for changing an angle of view of a shooting screen, a focus lens driving unit for driving the focus lens, and a lens connected via the focus lens. Determining an angle of view of the zoom lens in an automatic focusing control method for an imaging apparatus, comprising: a photoelectric conversion unit that converts the formed subject image into an electric signal and outputs the electric signal; and a control unit that controls the focus lens driving unit. And a step of performing focusing control according to the angle of view of the zoom lens, wherein the focusing control according to the angle of view of the zoom lens is performed by a focusing lens according to the angle of view of the zoom lens. A process of setting a driving amount; and a step of driving the focus lens so as to drive the focus lens over a predetermined range with the set driving amount. A step of controlling a stage, and extracting a high-frequency component of luminance of the subject image based on an electric signal output from the photoelectric conversion means for each drive of the focus lens by the set driving amount, and extracting the extracted high-frequency components. And a process for controlling the focus lens driving means so as to drive the focus lens to the determined focus position. 17. A first focusing control is performed when the angle of view of the zoom lens is equal to or greater than a predetermined angle, and a second focusing control is performed when the angle of view of the zoom lens is less than a predetermined angle. The first focus control includes a process of setting a first drive amount as a drive amount of a focus lens according to an angle of view of the zoom lens; and setting the focus lens in a predetermined range by the first drive amount. Controlling the focus lens driving means so as to drive the focus lens over the entire distance; extracting the high-frequency components each time the focus lens is driven by the first drive amount; and determining a focus position according to the extracted high-frequency components. And a process of controlling the focus lens driving means to drive the focus lens to the determined focus position, wherein the second focus control is performed by the focus lens. A process of setting a second drive amount different from the first drive amount as a drive amount, and a process of controlling the focus lens driving means so as to drive the focus lens with the second drive amount over a predetermined range. Processing for extracting the high-frequency component each time the focus lens is driven by the second drive amount, and determining a focus position in accordance with each of the extracted high-frequency components; and focusing the focus lens on the determined focus position. 17. The automatic focusing control method according to claim 16, further comprising the step of: controlling the focus lens driving unit to drive the focusing lens. 18. The second focusing control includes a process of interpolating a high-frequency component extracted every time the focus lens is driven by the second drive amount, and driving the focus lens by the second drive amount. 18. The automatic focusing control method according to claim 17, wherein the in-focus position is determined based on each high-frequency component extracted every time and an interpolation result thereof. 19. The automatic focusing control method according to claim 17, wherein the first drive amount is smaller than the second drive amount. 20. The apparatus according to claim 17, wherein the predetermined angle is an angle of view for distinguishing between an angle of view on a wide angle side and an angle of view on a telephoto side.
Or the automatic focusing control method according to item 18.