JP2008009048A - Imaging apparatus, and drive range control device for its focus lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect presence of a subject within a fixed range by changing intensity of auxiliary light and limit the scanning operation of automatic focus within the range. <P>SOLUTION: An auxiliary light control section 120 controls the intensity of auxiliary light of an auxiliary light emitting section 291. A luminance acquisition section 130 acquires a luminance signal from a picked-up image received via a focus lens 211. A contrast extraction section 140 extracts a contrast signal from the picked-up image. A subject detection section 150 detects the presence of a subject within the reaching range of the auxiliary light. A focus lens control section 160 drives the focus lens 211 on the basis of the extracted contrast signal and focuses the lens 211 on the subject. When the subject detection section 150 detects the presence of the subject within the reaching range of the auxiliary light, the focus lens control section 160 limits the drive range of the focus lens 211 within a range corresponding to the reaching range of the auxiliary light. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging device, and in particular, an imaging device having a focusing function for driving and focusing a focus lens based on contrast of a captured image, a focus lens driving range control device in the imaging device, and The present invention relates to a processing method and a program for causing a computer to execute the method.

In an imaging apparatus such as a digital still camera, a so-called contrast-type autofocus is known in which a focus lens is driven based on the contrast of a captured image to search and focus on a lens position where the contrast is highest. In this contrast-type autofocus, auxiliary light is used at low illuminance, and autofocus is performed based on the contrast of a captured image obtained by the auxiliary light. That is, auxiliary light is emitted in a half-pressed state generated in the process of shutter operation, and imaging is performed after focusing (see, for example, Patent Document 1).
Japanese Patent Laying-Open No. 2003-5023 (FIG. 1)

  In such contrast-type autofocus, the focus lens is driven from the closest side to the infinity side in order to extract the contrast in the captured image. Then, after determining the focus position based on the extracted contrast, the focus lens is moved to the focus position. Therefore, every time the shutter is half-pressed, the focus lens is driven from the closest side to the infinity side, and the in-focus position is determined. This series of operations is called a scan operation.

  However, if it is known that the subject is within a certain range, it is not necessary to perform the scanning operation for the entire range from the closest side to the infinity side. become. That is, when it is found that the subject is within a certain range, the autofocus process can be speeded up by restricting the scanning operation within the range.

  On the other hand, when the intensity of the image picked up before and after the intensity of the autofocus auxiliary light is changed, it is estimated that the subject exists within a certain range.

  Therefore, an object of the present invention is to detect the presence of a subject within a certain range by changing the intensity of auxiliary light, and to limit the autofocus scanning operation within that range.

  The present invention has been made to solve the above problems, and a first aspect of the present invention is an imaging apparatus having a focusing function for driving a focus lens based on contrast in a captured image to perform focusing. Luminance acquisition means for acquiring a luminance signal from the captured image obtained through the focus lens, auxiliary light control means for controlling the intensity of auxiliary light for focusing, and the auxiliary light with the first brightness. A difference detection means for detecting a difference between the luminance signal when the brightness is darker and the brightness signal when the auxiliary light is brighter than the second brightness, which is brighter than the first brightness, and based on the difference Focus lens control means for limiting the drive range of the focus lens for the focusing to a predetermined range, and a focus lens drive range control. It is a device. Accordingly, there is an effect that the driving range of the focus lens for focusing is limited based on the difference between the luminance signals by the auxiliary lights having different intensities. That is, the processing required for the scanning operation for focusing is accelerated.

  The second aspect of the present invention provides a focus lens, a luminance acquisition unit that acquires a luminance signal from the captured image obtained through the focus lens, and a contrast extraction unit that extracts a contrast signal from the captured image. And a focus lens control means for driving and focusing the focus lens based on the contrast signal, an auxiliary light emitting means for emitting auxiliary light for the focusing, and controlling the intensity of the auxiliary light. Auxiliary light control means, the luminance signal when the auxiliary light is darker than the first brightness, and the luminance signal when the auxiliary light is brighter than the second brightness that is brighter than the first brightness Difference detecting means for detecting a difference, and the focus lens control means is configured to adjust the focus lens for the focusing based on the difference. An imaging apparatus characterized by limiting the dynamic range to a predetermined range. This brings about the effect that focusing is performed by driving the focus lens within the limited driving range based on the difference between the luminance signals of the auxiliary lights having different intensities.

  In the second aspect, the difference detection means uses the luminance signal when the auxiliary light is turned off as the luminance signal when the auxiliary light is darker than the first brightness, and uses the auxiliary signal. The luminance signal when the auxiliary light is turned on may be used as the luminance signal when the light is brighter than the second brightness. This brings about the effect of simplifying the control of the auxiliary light.

  In the second aspect, the focus lens control means limits the driving range of the focus lens for the focusing to the predetermined range when a value by the difference exceeds a predetermined threshold value. It may be. This brings about the effect of determining whether or not to limit the drive range based on the threshold value.

  In the second aspect, the focus lens control means may use a range corresponding to the reach distance of the auxiliary light as the predetermined range. Here, the range corresponding to the reach distance of the auxiliary light may be the reach distance of the assist light itself, or may be a range obtained by adding a certain margin to the reach distance of the assist light.

  Further, in the second aspect, the focus lens control means sets the range corresponding to the strobe light arrival distance as the predetermined range when the strobe light arrival distance is shorter than the auxiliary light arrival distance. It may be used.

  The second aspect further includes illuminance detection means for detecting illuminance in the captured image, and the focus lens control means is configured to detect the illuminance when the detected illuminance is higher than a predetermined illuminance. The drive range may not be limited. This brings about the effect | action that this invention is applied only to low illumination intensity.

  In the second aspect, the focus lens control unit performs the focusing in a range other than the limited driving range when the focusing is not successful in the limited driving range. Also good. Thereby, when focusing is not successful, focusing is performed in a range other than the limited driving range.

  According to the present invention, when the presence of a subject within a certain range is detected by changing the intensity of the auxiliary light, an excellent effect that the autofocus scanning operation can be limited within the range. Can be played.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing an example of the appearance of a digital still camera 200 in the embodiment of the present invention. 1A shows an imaging surface on the subject side, and FIG. 1B shows an operation surface on the photographer side. The imaging surface of the digital still camera 200 includes a lens 210, a viewfinder 252, an auxiliary light emission unit 291, an illuminance detection unit 292, and a strobe light emission unit 293. A power switch 271 and a shutter button 272 are provided on the upper surface of the digital still camera 200. The operation surface of the digital still camera 200 includes a display 251, a viewfinder 252, a mode dial 273, a zoom button 274, and an operation button 275.

  The lens 210 receives reflected light from the subject. When the digital still camera 200 is not used, the shutter on the front surface of the lens 210 is closed. Further, a focus lens described later is provided inside the lens 210.

  The display 251 displays captured images and menu screens, and is realized by, for example, an LCD (Liquid Crystal Display). The display 251 may constitute a touch panel. In this case, the photographer can make a menu selection by touching the menu screen displayed on the display 251.

  The viewfinder 252 supplies a captured image from the imaging surface to the operation surface. The photographer can view the subject by looking through the viewfinder 252 from the operation surface.

  The power switch 271 is a switch for turning on or off the power of the digital still camera 200. The shutter button 272 is a button for imaging a subject. When the subject is imaged, an autofocus operation is performed when the shutter button 272 is half-pressed.

  The mode dial 273 receives an instruction for an imaging mode. The zoom button 274 receives an instruction to enlarge or reduce the captured image. The operation button 275 receives instructions in the up / down / left / right directions.

  The illuminance detection unit 292 detects the illuminance on the imaging surface. The illuminance detection unit 292 can be realized by, for example, a photodiode or a phototransistor.

  The auxiliary light emitting unit 291 emits auxiliary light for autofocus operation, and is realized by, for example, an LED (Light Emitting Diode). Although the light emission condition of the auxiliary light by the auxiliary light emitting unit 291 can be determined as appropriate, for example, when the illuminance detecting unit 292 determines that the light is darker than a certain illuminance, the auxiliary light can be controlled to emit light. it can.

  The strobe light emitting unit 293 emits strobe light for imaging. Although the light emission condition of the strobe light by the strobe light emission unit 293 can be determined as appropriate, for example, when the illuminance detection unit 292 determines that the light is darker than a certain illuminance, it can be controlled to emit the strobe light. .

  FIG. 2 is a diagram illustrating an internal configuration example of the digital still camera 200 according to the embodiment of the present invention. The digital still camera 200 includes a camera control unit 100, a focus lens 211, an imaging unit 213, an analog signal processing unit 220, an A / D conversion unit 230, a digital signal processing unit 240, a display unit 250, A recording unit 260, an operation unit 270, a motor driver 281, a stepping motor 282, a timing generation unit 283, an auxiliary light emission unit 291, and an illuminance detection unit 292 are provided.

  The camera control unit 100 controls the entire digital still camera 200, and includes a processor 101, a RAM (Random Access Memory) 102, and a ROM (Read Only Memory) 103. The processor 101 is a processing device that executes a program. The RAM 102 holds a work area necessary for processing by the processor 101. The ROM 103 holds initial programs and parameters executed by the processor 101.

  The focus lens 211 constitutes the lens 210 described above, and is a lens for focusing on a subject. The imaging unit 213 captures an image of a subject supplied via the focus lens 211, and is realized by, for example, a CCD (Charge Coupled Devices) or a CMOS (Complementary Metal Oxide Semiconductor) sensor.

  The analog signal processing unit 220 removes noise in the analog signal from the imaging unit 213 by correlated double sampling (CDS) and corrects the high and low parts of the analog signal by automatic gain control (AGC). Is. The A / D converter 230 converts the analog signal from the analog signal processor 220 into a digital signal. The digital signal processing unit 240 performs processing such as white balance and gamma conversion. The digital signal processed in the digital signal processing unit 240 is supplied to the display unit 250 and the recording unit 260. The digital signal processed by the digital signal processing unit 240 is supplied to the camera control unit 100 and used for an autofocus operation.

  The display unit 250 displays the digital signal supplied from the digital signal processing unit 240 and corresponds to the display 251 described above. The recording unit 260 records the digital signal supplied from the digital signal processing unit 240 on a recording medium.

  The operation unit 270 receives an operation from the photographer, and corresponds to a power switch 271, a shutter button 272, a mode dial 273, a zoom button 274, an operation button 275, and the like. The operation content received by the operation unit 270 is supplied to the camera control unit 100.

  The stepping motor 282 is a motor for moving the position of the focus lens 211. The motor driver 281 is a driver for driving the stepping motor 282. The motor driver 281 drives the stepping motor 282 according to control from the camera control unit 100. As a result, the focus lens 211 performs a scanning operation for autofocus, and focuses the subject.

  The timing generation unit 283 generates an imaging timing signal for the imaging unit 213. The timing generation unit 283 generates an imaging timing signal in accordance with control from the camera control unit 100. Thereby, the imaging unit 213 images the subject by the imaging timing signal generated from the timing generation unit 283.

  As described above, the auxiliary light emitting unit 291 emits auxiliary light for the autofocus operation. The auxiliary light emitting unit 291 switches the presence or absence of the auxiliary light emission or its intensity according to the control from the camera control unit 100.

  The illuminance detection unit 292 detects the illuminance on the imaging surface as described above. The illuminance detected by the illuminance detection unit 292 is supplied to the camera control unit 100.

  FIG. 3 is a diagram illustrating the relationship between autofocus and contrast. In this figure, the position of the focus lens is shown in the horizontal direction, and the height of contrast at each position is shown in the vertical direction.

  In the autofocus by the contrast method, the scanning operation is performed by sequentially driving the focus of the focus lens from the closest side (for example, about 10 cm) to the infinity side. This one-time scanning operation from the closest side to the infinity side is referred to as one stroke. In normal autofocus, in order to focus the focus lens, the movement of the focus lens for one stroke and the movement to the focus position are involved.

  In the embodiment of the present invention, before the autofocus operation, the intensity of the auxiliary light is changed to acquire the luminance signal for each, and when the difference between the luminance signals exceeds a predetermined threshold, the auxiliary light is It is estimated that the subject exists within the reachable range. As a result, when the subject exists within the auxiliary light reachable range, the autofocus scan range is limited to a range corresponding to the auxiliary light reachable distance. Thereby, the time required for the autofocus scanning operation can be saved.

  Here, as shown in FIG. 3, it is assumed that the reach distance of the auxiliary light is equal to the maximum value of the contrast. At this time, in order to detect the maximum value of the contrast, it is necessary to scan to a position slightly exceeding the maximum value (for the margin). Therefore, if such a case is taken into consideration, the limit range of the autofocus scan range is a range obtained by adding the margin to the reach distance of the auxiliary light. If such a case is not taken into consideration, the limit range of the autofocus scan range is the reach distance of the auxiliary light.

  In other words, the “range corresponding to the reach distance of the auxiliary light” that limits the scan range of the autofocus may be the reach distance of the auxiliary light itself, or a range obtained by adding a margin to the reach distance of the auxiliary light. There may be.

  The reach distance of the auxiliary light depends on the LED used in the auxiliary light emitting unit 291, the lens 210 that receives the auxiliary light, the imaging unit 213, and the like, and may change in the future. A degree can be assumed.

  FIG. 4 is a diagram showing an example of the driving range of the focus lens 211 in the embodiment of the present invention. FIG. 4A illustrates an example in which the strobe light reaching distance by the strobe light emitting unit 293 is longer than the auxiliary light reaching distance by the auxiliary light emitting unit 291. In this case, as described with reference to FIG. 3, the drive range of the focus lens 211 is limited to the reach distance of the auxiliary light or the range obtained by adding a margin to the reach distance of the auxiliary light.

  Normally, as shown in FIG. 4A, it is assumed that the arrival distance of the strobe light is longer than the arrival distance of the auxiliary light. As shown in FIG. 4B, if the strobe light reaching distance by the strobe light emitting unit 293 is shorter than the auxiliary light reaching distance by the auxiliary light emitting unit 291, the autofocus can operate normally at low illuminance. Is limited to the range of the strobe light. In other words, when the strobe light reach distance is shorter than the auxiliary light reach distance, when the illuminance detection unit 292 determines that the illuminance is lower than a certain level, the drive range of the focus lens 211 is set to the strobe light. Can be limited up to

  FIG. 5 is a diagram illustrating a functional configuration example of the camera control unit 100 according to the embodiment of the present invention. The camera control unit 100 includes an auxiliary light control unit 120, a luminance acquisition unit 130, a contrast extraction unit 140, a subject detection unit 150, and a focus lens control unit 160.

  The auxiliary light control unit 120 controls the intensity of auxiliary light in the auxiliary light emitting unit 291. When the shutter button 272 is half-pressed, it is determined whether the subject is within the reach of the auxiliary light prior to the autofocus operation. At that time, the auxiliary light control unit 120 changes the intensity of the auxiliary light in the auxiliary light emitting unit 291. In this embodiment, as an example of the change in the intensity of the auxiliary light, the auxiliary light is turned off or turned on.

  Further, the auxiliary light control unit 120 refers to the illuminance detected by the illuminance detection unit 292, and if it is higher than the predetermined illuminance, the auxiliary light control unit 120 does not control the auxiliary light and notifies the focus lens control unit 160 to that effect. . As a result, the focus lens control unit 160 does not limit the drive range of the focus lens 211.

  The luminance acquisition unit 130 acquires a luminance signal from a captured image received through the focus lens 211. This luminance signal is a luminance component such as an RGB (Red Green Blue) signal generated by the digital signal processing unit 240. A luminance signal as a captured image is acquired by integrating all the pixels of the captured image or some pixels such as the central portion.

  The contrast extraction unit 140 extracts a contrast signal from the captured image. The contrast extraction unit 140 integrates edge component information in a predetermined detection area of the captured image to extract a contrast signal. Using this contrast signal, the focus lens control unit 160 performs an autofocus operation.

  The subject detection unit 150 detects the presence of the subject within the reach of the auxiliary light, and is turned off, a luminance holding unit 151, a lighting luminance holding unit 152, a luminance difference calculation unit 153, and a threshold holding unit 154. And a luminance difference determination unit 155.

  The off-time luminance holding unit 151 holds the luminance signal acquired by the luminance acquisition unit 130 when the auxiliary light is turned off as an example of reducing the intensity of the auxiliary light. The lighting luminance holding unit 152 holds the luminance signal acquired by the luminance acquiring unit 130 when the auxiliary light is turned on as an example of increasing the intensity of the auxiliary light.

  The luminance difference calculation unit 153 calculates a difference between the luminance signal held in the unlit luminance holding unit 151 and the luminance signal held in the lighting luminance holding unit 152. The threshold value holding unit 154 holds a threshold value to be compared with the difference calculated by the luminance difference calculation unit 153. The luminance difference determination unit 155 determines whether or not the difference calculated by the luminance difference calculation unit 153 exceeds the threshold value held in the threshold value holding unit 154. That is, if the difference exceeds the threshold value, there is a certain difference between when the auxiliary light is turned off and when the auxiliary light is turned on. Therefore, it is estimated that the subject exists within the reachable range of the auxiliary light.

  Here, as an example of controlling the intensity of the auxiliary light, the case of turning off the light and the time of turning on are given, but intermediate intensity other than this may be used.

  The focus lens control unit 160 drives the focus lens 211 based on the contrast signal extracted by the contrast extraction unit 140 to focus on the subject. When the luminance difference determination unit 155 determines that the difference exceeds the threshold value, the focus lens control unit 160 limits the drive range of the focus lens 211 as described with reference to FIG. However, when the illuminance detected by the illuminance detection unit 292 is higher than the predetermined illuminance, the focus lens control unit 160 does not limit the drive range of the focus lens 211.

  When a series of autofocus operations are completed and the focus lens 211 is positioned, the focus lens control unit 160 reports the completion of the operation to the auxiliary light control unit 120, thereby the auxiliary light control unit 120. Turns off the auxiliary light from the auxiliary light emitting unit 291.

  Next, the operation of the digital still camera 200 according to the embodiment of the present invention will be described with reference to the drawings.

  FIG. 6 is a diagram illustrating an example of an autofocus processing procedure by the digital still camera 200 according to the embodiment of the present invention.

  When the shutter button 272 is pressed halfway, first, as an example in which the intensity of the auxiliary light is lowered, the luminance signal when the auxiliary light is turned off by the auxiliary light emitting unit 291 is acquired by the luminance acquisition unit 130, and the luminance when the light is turned off It is held by the holding unit 151 (step S911). Next, as an example in which the intensity of the auxiliary light is lowered by the auxiliary light control unit 120, the auxiliary light from the auxiliary light emitting unit 291 is turned on (step S912). Then, the luminance signal when the auxiliary light is turned on by the auxiliary light emitting unit 291 is acquired by the luminance acquisition unit 130 and is held in the lighting luminance holding unit 152 (step S913).

  The difference between the luminance signal held in the auxiliary light emitting unit 291 and the luminance signal held in the lighting luminance holding unit 152 is calculated by the luminance difference calculating unit 153, and the difference exceeds the threshold held in the threshold holding unit 154. Is determined by the luminance difference determination unit 155 (step S914). As a result, if the difference exceeds the threshold value, it is estimated that the subject exists within the auxiliary light arrival distance, and the driving range (scan range) of the focus lens 211 in the autofocus operation is set to the auxiliary light arrival distance. The range is limited to the corresponding range (step S915).

  Thereafter, the focus lens 211 is driven for autofocus by the focus lens control unit 160 and a scan operation is performed (step S921). As a result, when contrast is extracted in the scan range, the focus lens 211 is moved to the in-focus position by the focus lens control unit 160 (step S926).

  On the other hand, when the contrast is not extracted, if the scan range is limited in step S915 (step S923), the scan operation is also performed for the limited remaining range (step S924). As a result, when the contrast is extracted in the scan range (step S925), the focus lens 211 is moved to the in-focus position by the focus lens control unit 160 (step S926).

  If the scan range is not limited or the contrast is not extracted even in the limited remaining range, the focus lens 211 is moved to a predetermined fixed position (step S927).

  Thereafter, the auxiliary light by the auxiliary light emitting unit 291 is turned off by the auxiliary light control unit 120 (step S928). As a result, the autofocus operation is completed, and the actual shooting phase is started.

  As described above, according to the embodiment of the present invention, the luminance signal is acquired by the luminance acquisition unit 130 before and after the intensity of the auxiliary light of the auxiliary light emitting unit 291 is changed, and the focus lens is based on the difference between the luminance signals. By limiting the driving range 211, the speed of the autofocus operation by the contrast extraction unit 140 and the focus lens control unit 160 can be increased.

  The embodiment of the present invention is an example for embodying the present invention and has a corresponding relationship with the invention-specific matters in the claims as shown below, but is not limited thereto. However, various modifications can be made without departing from the scope of the present invention.

  That is, in claim 1, the luminance acquisition unit corresponds to, for example, the luminance acquisition unit 130. An auxiliary light control unit corresponds to the auxiliary light control unit 120, for example. The difference detection means corresponds to the subject detection unit 150, for example. A focus lens control unit corresponds to the focus lens control unit 160, for example.

  Further, in claim 2, the focus lens corresponds to the focus lens 211, for example. The luminance acquisition unit corresponds to the luminance acquisition unit 130, for example. The contrast extraction unit corresponds to the contrast extraction unit 140, for example. The focus lens control unit corresponds to the focus lens control unit 160, for example. The auxiliary light control unit corresponds to the auxiliary light control unit 120, for example. The difference detection means corresponds to the subject detection unit 150, for example.

  Further, in claim 7, the illuminance detection means corresponds to the illuminance detection unit 292, for example.

  In claims 9 and 10, the first luminance acquisition procedure corresponds to, for example, step S911. The second luminance acquisition procedure corresponds to step S913, for example. The difference detection procedure corresponds to step S914, for example. The focus lens control procedure corresponds to, for example, step S915.

In the embodiment of the present invention, the presence of the subject is determined based on the difference between the luminance signals, but other signals including luminance components may be used. For example, AE data (usually including a contrast component and a luminance component) used for automatic exposure (AE) can be used.

  The processing procedure described in the embodiment of the present invention may be regarded as a method having a series of these procedures, and a program for causing a computer to execute the series of procedures or a recording medium storing the program May be taken as

It is a figure which shows the example of an external appearance of the digital still camera 200 in embodiment of this invention. It is a figure which shows the example of an internal structure of the digital still camera 200 in embodiment of this invention. It is a figure which shows the relationship between autofocus and contrast. It is a figure which shows the drive range example of the focus lens 211 in embodiment of this invention. It is a figure which shows the function structural example of the camera control part 100 in embodiment of this invention. It is a figure which shows the example of a process sequence of the autofocus by the digital still camera 200 in embodiment of this invention.

Explanation of symbols

100 camera control unit 101 processor 102 RAM
103 ROM
DESCRIPTION OF SYMBOLS 120 Auxiliary light control part 130 Luminance acquisition part 140 Contrast extraction part 150 Subject detection part 151 Unlit brightness holding part 152 Illumination brightness holding part 153 Luminance difference calculation part 154 Threshold value holding part 155 Brightness difference judgment part 160 Focus lens control part 200 Digital Still camera 210 Lens 211 Focus lens 213 Imaging unit 220 Analog signal processing unit 230 A / D conversion unit 240 Digital signal processing unit 250 Display unit 251 Display 252 Finder 260 Recording unit 270 Operation unit 271 Power switch 272 Shutter button 273 Mode dial 274 Zoom Button 275 Operation button 281 Motor driver 282 Stepping motor 283 Timing generation unit 291 Auxiliary light emission unit 292 Illuminance detection unit 293 Strobe emission Part

Claims (10)

In an imaging apparatus having a focusing function that performs focusing by driving a focus lens based on contrast in a captured image,
Luminance acquisition means for acquiring a luminance signal from the captured image obtained through the focus lens;
Auxiliary light control means for controlling the intensity of auxiliary light for the focusing;
Difference detection for detecting a difference between the luminance signal when the auxiliary light is darker than the first lightness and the luminance signal when the auxiliary light is brighter than the second lightness that is brighter than the first lightness. Means,
A focus lens drive range control device comprising: a focus lens control unit that limits a drive range of the focus lens for focusing based on the difference to a predetermined range. A focus lens,
Luminance acquisition means for acquiring a luminance signal from the captured image obtained through the focus lens;
Contrast extraction means for extracting a contrast signal from the captured image;
Focus lens control means for driving and focusing the focus lens based on the contrast signal;
Auxiliary light emitting means for emitting auxiliary light for focusing, and
Auxiliary light control means for controlling the intensity of the auxiliary light;
Difference detection for detecting a difference between the luminance signal when the auxiliary light is darker than the first lightness and the luminance signal when the auxiliary light is brighter than the second lightness that is brighter than the first lightness. Means,
The focus lens control means limits the drive range of the focus lens for the focusing to a predetermined range based on the difference.   The difference detection means uses the luminance signal when the auxiliary light is turned off as the luminance signal when the auxiliary light is darker than the first lightness, and the auxiliary light is made to be less than the second lightness. The imaging apparatus according to claim 2, wherein the brightness signal when the auxiliary light is turned on is used as the brightness signal when the brightness is increased.   The focus lens control means limits the driving range of the focus lens for the focusing to the predetermined range when the value resulting from the difference exceeds a predetermined threshold. Imaging device.   The imaging apparatus according to claim 2, wherein the focus lens control unit uses a range corresponding to a reach distance of the auxiliary light as the predetermined range.   The focus lens control means uses, as the predetermined range, a range corresponding to the arrival distance of the strobe light when the arrival distance of the strobe light is shorter than the arrival distance of the auxiliary light. The imaging device described. Further comprising illuminance detection means for detecting illuminance in the captured image;
The imaging apparatus according to claim 2, wherein the focus lens control unit does not limit a driving range of the focus lens when the detected illuminance is higher than a predetermined illuminance.   3. The imaging apparatus according to claim 2, wherein the focus lens control unit performs the focusing in a range other than the limited driving range when the focusing is not successful in the limited driving range. . In an imaging apparatus having a focusing function that performs focusing by driving a focus lens based on contrast in a captured image,
A first luminance acquisition procedure for acquiring a first luminance signal from the captured image obtained through the focus lens when the auxiliary light for focusing is darker than the first brightness;
A second luminance acquisition procedure for acquiring a second luminance signal when the auxiliary light is brighter than a second lightness that is brighter than the first lightness;
A difference detection procedure for detecting a difference between the first and second luminance signals;
A focus lens drive range control method comprising: a focus lens control procedure for restricting a drive range of the focus lens for focusing to a predetermined range based on the difference. In an imaging apparatus having a focusing function that performs focusing by driving a focus lens based on contrast in a captured image,
A first luminance acquisition procedure for acquiring a first luminance signal from the captured image obtained through the focus lens when the auxiliary light for focusing is darker than the first brightness;
A second luminance acquisition procedure for acquiring a second luminance signal when the auxiliary light is brighter than a second lightness that is brighter than the first lightness;
A difference detection procedure for detecting a difference between the first and second luminance signals;
A program for causing a computer to execute a focus lens control procedure for limiting a driving range of the focus lens for focusing to a predetermined range based on the difference.

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