JP2005121885A - Imaging apparatus, its control method, program, and storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a high-speed and high-precision auto focusing operation at low cost. <P>SOLUTION: The imaging apparatus is provided with: a photographing optical system 31 having a focus adjustment lens 3; an imaging device 5 for subjecting the formed image of a subject to photoelectric conversion; an LED 30 for emitting a luminous flux toward the subject; an arithmetic section 15 for calculating an approximate distance to the subject, based on the position of an image signal which is formed in the imaging device by its receiving light emitted by the LED and reflected by the subject; a lens driving device 22 for scanning the focus adjustment lens over a prescribed front and rear range in the optical axis direction of the center position which is a position in the optical axis direction of this lens in focusing on the approximate distance; and a focus detection section 14 for determining the position of the focus adjustment lens in focusing on the subject, on the basis of the image signal formed by the imaging device at each position of the focus adjustment lens when scanned. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for performing focus adjustment using an image signal acquired by an image sensor that photoelectrically converts a subject image formed by an imaging optical system.

  As a conventional technique related to an automatic focus adjustment device that performs focus adjustment using an image signal acquired by an image sensor that photoelectrically converts a subject image formed by an imaging optical system, Japanese Patent Laid-Open No. 5-119250, What is disclosed in Japanese Patent Application Laid-Open No. 2000-111792 is known.

  Japanese Patent Laid-Open No. 5-119250 discloses the following technique.

  Autofocus using contrast detection and autofocus using infrared light detection are used together, and during normal shooting operations, focus adjustment is performed using autofocus means using contrast detection. Only in a shooting environment where the focus adjustment operation by the conventional autofocus means is difficult, the autofocus means using infrared light detection is switched to perform the distance measuring operation and the autofocus operation for a desired subject. Therefore, according to this, appropriate autofocus can be performed regardless of the brightness of the subject.

  Japanese Patent Laid-Open No. 2000-111792 discloses the following technique.

Autofocus means using contrast detection that performs photoelectric conversion of the subject image to generate an image signal, detects a predetermined high-frequency component from the generated image signal, and adjusts the focus accordingly, and light emission that irradiates infrared light In accordance with the output of the temperature detection means for detecting the ambient temperature, the means (LED) and the autofocus means using infrared light detection for receiving the reflected light from the subject and detecting the output signal according to the subject distance are used together. One of the autofocus means using contrast detection and the autofocus means using infrared light detection is selected to perform the autofocus operation. Therefore, according to this, it is possible to perform an appropriate autofocus regardless of changes in the use environment temperature.
Japanese Patent Laid-Open No. 5-119250 JP 2000-111792 A

  However, in the above conventional example, one of the autofocus means using contrast detection and the autofocus means using infrared light detection is selected according to the brightness of the subject and the operating environment temperature, and the autofocus operation is performed. Therefore, it is necessary to separately provide an autofocus means using infrared light detection in addition to an image sensor that photoelectrically converts a subject image formed by the imaging optical system. Therefore, there is a problem that the cost increases. Further, when either one of them is selected and an autofocus operation is performed, there is a problem that a high-speed and high-precision autofocus operation cannot be performed.

  Accordingly, the present invention has been made in view of the above-described problems, and an object thereof is to realize a high-speed and high-precision autofocus operation at a low cost.

  In order to solve the above-described problems and achieve the object, an imaging apparatus according to the present invention includes a photographing optical system including a focusing lens that moves in an optical axis direction in order to form a subject image on a target focal plane. An imaging means for photoelectrically converting an object image formed by the photographing optical system to generate an electrical image signal, a light projecting means for irradiating a light beam toward the object, and a light emitted from the light projecting means. Focusing on the approximate distance and calculation means for calculating the approximate distance to the subject based on the position of the image signal generated by the image capture means when the image capture means receives the light reflected by the subject. Lens driving means for scanning the focus adjustment lens over a predetermined range before and after the center position in the optical axis direction, with the position in the optical axis direction of the focus adjustment lens for the center position as the center position, and the focus adjustment lens Focus detecting means for obtaining a position of the focus adjusting lens for focusing on the subject based on an image signal generated by the imaging means at each position of the focus adjusting lens when scanned. It is characterized by.

  Further, in the imaging apparatus according to the present invention, the light projecting unit includes a plurality of light emitting elements larger than the number of the plurality of focus detection areas provided in the photographing screen, and the focus detection is performed from the plurality of light emitting elements. The same number of light-emitting elements as the number of regions are selected, and the plurality of selected light-emitting elements are caused to emit light sequentially.

  Further, in the imaging apparatus according to the present invention, the light projecting unit includes a plurality of light emitting elements larger than the number of the plurality of focus detection areas provided in the photographing screen, and the focus detection is performed from the plurality of light emitting elements. The same number of light-emitting elements as the number of regions are selected, and the plurality of selected light-emitting elements are configured to emit light simultaneously, and the imaging of the reflected image irradiated from the light-emitting elements and reflected by the subject The apparatus further comprises determination means for determining the validity of the approximate distance based on the position on the means.

  In the image pickup apparatus according to the present invention, when the light emitted from the light projecting means and reflected by the subject is picked up by the image pickup means, only a partial region of the image signal formed by the image pickup means is used. Is read out.

  In the imaging apparatus according to the present invention, the partial area is made different depending on a light emitting element that emits light.

  In the image pickup apparatus according to the present invention, the partial area is made different according to a focal length of the photographing optical system.

  The image pickup apparatus according to the present invention further includes a detection unit that detects whether or not the subject exists at a shorter distance than an assumed distance based on an image signal generated by the image pickup unit, A light emitting element that emits light is selected from a plurality of light emitting elements provided in the light projecting unit based on a detection result of the detecting unit.

  Further, in the imaging apparatus according to the present invention, by causing one of a plurality of light emitting elements provided in the light projecting unit to emit light and causing the imaging unit to capture the light reflected by the subject, It further comprises detection means for detecting whether or not the subject exists at a shorter distance than the assumed distance, and causes the other light emitting elements of the plurality of light emitting elements to emit light based on the detection result of the detection means. It is characterized by determining whether or not.

The image pickup apparatus control method according to the present invention includes a photographing optical system including a focus adjustment lens that moves in the optical axis direction to form a subject image on a target focal plane, and an image formed by the photographing optical system. An imaging device control method for controlling an imaging device comprising imaging means for photoelectrically converting the subject image to generate an electrical image signal and light projecting means for irradiating a light beam toward the subject, A calculation step of calculating a rough distance to the subject based on a position of an image signal generated by the imaging unit when the imaging unit receives light irradiated from the light projecting unit and reflected by the subject; A lens that scans the focus adjustment lens over a predetermined range before and after the center position in the optical axis direction with the position in the optical axis direction of the focus adjustment lens for focusing on the approximate distance as the center position. And a position of the focus adjustment lens for focusing on the subject based on an image signal generated by the imaging means at each position of the focus adjustment lens when the focus adjustment lens is scanned. A desired focus detection step;
It is characterized by comprising.

  A program according to the present invention causes a computer to execute the above-described method for controlling an imaging apparatus.

  A storage medium according to the present invention stores the above program in a computer-readable manner.

  As described above, according to the present invention, it is possible to realize a high-speed and high-precision autofocus operation at a low cost.

  Hereinafter, preferred embodiments of the present invention will be described.

  First, an outline of the present embodiment will be described.

  In the present embodiment, the CCD 5 is used as the light receiving means for active AF (autofocus), the distances from the light receiving means output to a plurality of subjects are estimated, the distances to the appropriate subjects are estimated from the results, and the distances are estimated. Within the range set with the corresponding position as the center, the position of the focus lens group 3 where the high frequency component output from the image signal generated by the CCD 5 is the largest is obtained while moving the focus lens group 3. In other words, by obtaining a rough distance to the subject and performing a scan AF process that detects an accurate in-focus position around that distance, it is possible to focus at high speed and accurately with a low-cost configuration that only requires light projection means. Made it possible to detect the position.

  By turning on multiple light emitting elements at the same time, it is possible to estimate the distance to multiple subjects at a higher speed, and by estimating the distance to multiple subjects, a wide variety of subjects on the screen On the other hand, the in-focus position can be detected.

  By performing scan AF in the macro area prior to the active AF and knowing whether or not the subject exists at a shorter distance than the assumed distance, a “reflected image is formed outside the assumed range, making it difficult to separate the reflected image. The problem of lighting multiple light-emitting elements at the same time has been resolved.

  First, by performing active AF at the center distance measuring point and knowing whether or not the subject is closer than the assumed distance, a reflection image is formed outside the assumed range, making it difficult to separate the reflection image. The problem of lighting multiple light-emitting elements at the same time has been resolved.

  By not displaying the image at the time of storing the illumination on the LCD 10, there is a sense of incongruity such as “a part of the image is temporarily displayed” or “an image in which the reflection image of the light emitting element is reflected” is displayed on the LCD. A certain image can be prevented from being displayed on the LCD 10. The non-illuminated accumulated image is displayed immediately after that, thereby avoiding the adverse effect of giving the photographer an uncomfortable feeling that the screen freezes.

  By not displaying the image at the time of storing the illumination on the LCD 10, it becomes possible to read out only a part of the image used for the calculation, so that the processing is speeded up.

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

  In FIG. 1, 1 is an imaging device, 2 is a zoom lens group, 3 is a focus lens group, 4 is a light amount adjusting means for controlling the amount of light beam transmitted through a photographing optical system including the zoom lens group 2, the focus lens group 3, and the like. The aperture 31 is an exposure means, 31 is a photographic lens barrel incorporating the zoom lens group 2, the focus lens group 3, the aperture 4, and the like, 5 is a subject image that has passed through the photographic optical system, and this is photoelectrically converted. A solid-state image pickup device (hereinafter referred to as a CCD) such as a CCD, an image pickup circuit 6 that receives an electric signal photoelectrically converted by the CCD 5 and performs various image processing to generate a predetermined image signal, and 7 is an image pickup circuit 6 An A / D conversion circuit 8 converts the analog image signal generated by the digital image signal into a digital image signal, and 8 is a buffer for receiving the output of the A / D conversion circuit 7 and temporarily storing the image signal. A memory (VRAM), such as a memory, 9 reads out an image signal stored in the VRAM 8, converts it into an analog signal, and converts it into an image signal in a form suitable for reproduction output. An image display device (hereinafter referred to as LCD) such as a liquid crystal display device (LCD) for displaying signals, a storage memory 12 for storing image data such as a semiconductor memory, and 11 for reading and storing image signals temporarily stored in the VRAM 8 In order to obtain a form suitable for storage in the storage memory 12, a compression circuit that performs compression processing and encoding processing of image data and a form optimal for reproducing and displaying the image data stored in the storage memory 12 are used. A compression / decompression circuit comprising a decompression circuit for performing a decoding process, a decompression process, and the like, and an automatic exposure in response to an output from the A / D conversion circuit 7 AE) AE processing circuit that performs processing, 14 is a scan AF processing circuit that receives an output from the A / D conversion circuit 7 and performs automatic focus adjustment (AF) processing, and 15 is an arithmetic memory that controls the imaging apparatus. Built-in CPU, 16 is a timing generator (hereinafter referred to as TG) that generates a predetermined timing signal, 17 is a CCD driver, 21 is a diaphragm drive motor that drives the diaphragm 4, and 18 is a first motor drive that drives and controls the diaphragm drive motor 21. Circuit, 22 a focus drive motor that drives the focus lens group 3, 19 a second motor drive circuit that drives and controls the focus drive motor 22, 23 a zoom drive motor that drives the zoom lens group 2, and 20 a zoom drive motor A third motor drive circuit for driving and controlling 23, 24 an operation switch comprising various switch groups, 25 a variety of controls, etc. EEPROM, which is an electrically rewritable read-only memory in which data for use in performing various operations and data used for performing various operations are stored in advance, 26 is a battery, 28 is a strobe light emitting unit, and 27 is a strobe light emitting unit 28 A switching circuit for controlling the flash emission of light, a light emitting means (hereinafter referred to as LED) 30 comprising a plurality of light emitting elements such as a light projecting lens and a light emitting diode for irradiating a subject with a plurality of light beams, and 32 for emitting infrared light. The iR cut filter 33 to be blocked is a filter driving device for inserting and retracting the iR cut filter 32 to the front surface of the CCD 5. A light-emitting diode for irradiating a subject with a plurality of light beams can also be used as AF auxiliary light for illuminating the subject supplementarily when performing scan AF. Conversely, it is also possible to use the AF auxiliary light as means for irradiating a subject with a plurality of light beams.

  The storage memory 12 that is a storage medium for image data or the like is a fixed type semiconductor memory such as a flash memory, a card type flash memory that has a card shape or a stick shape, and is detachable from the apparatus. In addition to the semiconductor memory, various forms such as a magnetic storage medium such as a hard disk or a floppy disk are applied.

  The operation switch 24 includes a main power switch for starting the imaging apparatus 1 to supply power, a release switch for starting a photographing operation (storage operation), a reproducing switch for starting a reproducing operation, and a photographing optical system. There is a zoom switch for moving the zoom lens group 2 to perform zooming.

  The release switch then performs a first stroke (hereinafter referred to as SW1) for generating an instruction signal for starting AE processing and AF processing performed prior to the photographing operation and a second stroke (hereinafter referred to as SW2) for generating an instruction signal for starting an actual exposure operation. And a two-stage switch.

  The operation of the imaging apparatus configured as described above will be described below.

  First, the light flux of the subject that has passed through the taking lens barrel 31 of the image pickup apparatus 1 is adjusted on the light amount by the diaphragm 4 and then imaged on the light receiving surface of the CCD 5. This subject image is converted into an electrical signal by photoelectric conversion processing by the CCD 5 and output to the imaging circuit 6. The imaging circuit 6 performs various signal processing on the input signal to generate a predetermined image signal. The image signal is output to the A / D conversion circuit 7 and converted into a digital signal (image data), and then temporarily stored in the VRAM 8.

  The image data stored in the VRAM 8 is output to the D / A conversion circuit 9, converted into an analog signal, converted into an image signal in a form suitable for display, and then displayed as an image on the LCD. On the other hand, the image data stored in the VRAM 8 is also output to the compression / decompression circuit 11. After compression processing is performed by the compression circuit in the compression / decompression circuit 11, it is converted into image data in a form suitable for storage and stored in the storage memory 12.

  Also. For example, when a reproduction switch (not shown) of the operation switches 24 is operated and turned on, the reproduction operation is started. Then, the image data stored in a compressed form in the storage memory 12 is output to the compression / expansion circuit 11, subjected to decoding processing, expansion processing, etc. in the expansion circuit, and then output to the VRAM 8 and temporarily stored. The Further, this image data is output to the D / A conversion circuit 9, converted into an analog signal, converted into an image signal in a form suitable for display, and then displayed as an image on the LCD.

  On the other hand, the image data digitized by the A / D conversion circuit 7 is output to the AE processing circuit 13 and the scan AF processing circuit 14 separately from the VRAM 8 described above. First, the AE processing circuit 13 receives the input digital image signal and performs arithmetic processing such as cumulative addition on the luminance value of the image data for one screen. Thereby, the AE evaluation value corresponding to the brightness of the subject is calculated. This AE evaluation value is output to the CPU 15.

  The scan AF processing circuit 14 receives an input digital image signal, extracts a high-frequency component of image data for one screen through a high-pass filter (HPF) or the like, and performs arithmetic processing such as cumulative addition. . Thereby, an AF evaluation value corresponding to the contour component amount on the high frequency side is calculated. As described above, the scan AF processing circuit 14 plays a role of high-frequency component detection means for detecting a predetermined high-frequency component from the image signal generated by the CCD 5 in the process of performing the AF processing.

  On the other hand, a predetermined timing signal is output from the TG 16 to the CPU 15, the imaging circuit 6, and the CCD driver 17, and the CPU 15 performs various controls in synchronization with this timing signal. The imaging circuit 6 receives the timing signal from the TG 16 and performs various image processing such as separation of color signals in synchronization with the timing signal. Further, the CCD driver 17 receives the timing signal of the TG 16 and drives the CCD 5 in synchronization therewith.

  Further, the CPU 15 controls the first motor drive circuit 18, the second motor drive circuit 19, and the third motor drive circuit 20, respectively, and thereby controls the aperture through the aperture drive motor 21, the focus drive motor 22, and the zoom drive motor 23. 4. Drive control of the focus lens group 3 and the zoom lens group 2 is performed. That is, the CPU 15 controls the first motor drive circuit 18 based on the AE evaluation value calculated by the AE processing circuit 13 to drive the aperture drive motor 21 and adjust the aperture amount of the aperture 4 so as to be appropriate. I do. The CPU 15 controls the second motor drive circuit 19 based on the AF evaluation value calculated by the scan AF processing circuit 14 and the output obtained by the active AF means described later to drive the focus drive motor 22, and the focus lens group. AF control for moving 3 to the in-focus position is performed. When a zoom switch (not shown) among the operation switches 24 is operated, the CPU 15 moves the zoom lens group 2 by controlling the third motor drive circuit 20 and driving the zoom motor 23 in response to the operation. Then, the zooming operation of the photographing optical system is performed.

  Next, an actual photographing operation of the imaging apparatus according to the present embodiment will be described with reference to a flowchart shown in FIG.

  When the main power switch of the image pickup apparatus 1 is in the on state and the operation mode of the image pickup apparatus is in the shooting (recording) mode, the shooting processing sequence is executed.

  First, in step S1, the CPU 15 displays an image formed on the CCD 5 through the photographing lens barrel 31 as an image on the LCD. That is, the subject image formed on the CCD 5 is photoelectrically converted by the CCD 5 and converted into an electrical signal, and then output to the imaging circuit 6. Then, various signal processing is performed on the input signal to generate a predetermined image signal, which is then output to the A / D conversion circuit 7 and converted into a digital signal (image data) and temporarily stored in the VRAM 8. Stored. The image data stored in the VRAM 8 is output to the D / A conversion circuit 9, converted into an analog signal, converted into an image signal in a form suitable for display, and then displayed as an image on the LCD.

  Next, in step S2, the state of the release switch is confirmed. When the photographer operates the release switch and the CPU 15 confirms that SW1 (first stroke of the release switch) has been turned on, the process proceeds to the next step S3, and normal AE processing is executed. Subsequently, active AF processing is performed in step S4. In this case, the CPU 15 controls the light emitting means 30 to sequentially irradiate a plurality of light beams toward the subject, and the reflected light is received by the CCD 5 via the photographing lens barrel 31. Then, the CPU 15 obtains the positions of a plurality of reflected images corresponding to the respective light fluxes from the image obtained by the CCD 5, and further calculates the distance to the subject from the positions of the reflected images. Then, an in-focus position is calculated according to a predetermined algorithm from the obtained distances to a plurality of subjects, and an area for performing scan AF, which will be described later, is determined. Examples of the predetermined algorithm include Japanese Patent Publication No. 7-069513, Japanese Patent Application Laid-Open No. 64-935, Japanese Patent Application Laid-Open No. 64-48050, Japanese Patent Application Laid-Open No. 64-48051, and Japanese Patent Application Laid-Open No. 64-48052. An algorithm described in a gazette is used. However, in practice, after the external light removal operation is performed, the position of the reflected image is obtained and the distance is calculated.

  The active AF process performed in this way is a process for detecting a rough subject distance (focus position of the focus lens group 3) with respect to a desired subject, and is an AF process for so-called rough adjustment. Thereafter, scan AF processing for fine adjustment for detecting an accurate in-focus position is performed.

  That is, the CPU 15 then performs a scan AF process for fine adjustment to detect an accurate in-focus position in step S5. This is based on the image signal in the determined scan AF area while moving the focus lens group 3 minutely after moving the focus lens group 3 to the vicinity of the in-focus position obtained from the distance measurement result of the active AF process. This is done by monitoring the output of the scan AF processing circuit and determining the position of the focus lens group 3 where the high-frequency component output from the image signal generated by the CCD 5 is the largest.

  When the predetermined AF processing is completed in this way, the CPU 15 confirms SW2 (second stroke of the release switch) in step S6. If SW2 is on, the CPU 15 proceeds to step S7 and actually The exposure process is executed.

  While the SW2 (second stroke of the release switch) is being confirmed, the subject image formed on the CCD 5 is displayed on the LCD.

  Details of the active AF executed in step S4 of FIG. 2 will be described here. The flowchart is shown in FIG.

  As described above, when SW1 is turned on in the imaging apparatus 1, AE processing and AF processing are executed. Of these, the AF process is a scan AF process in which, after coarse adjustment is first made by the active AF process, an accurate in-focus position is detected based on the distance measurement result within a predetermined range centered on the distance measurement result. I do.

  First, in step S20, the CPU 15 reads information on the focal length of the photographing optical system set by operating a zoom switch (not shown) of the operation switches 24. In step S21, a light emitting element to be lit is selected from a plurality of light emitting elements in the light emitting means 30. This is a process for making the position of the luminous flux irradiated toward the subject the same on the photographing screen without mechanically moving the light emitting element even when the zooming operation is performed by operating the zoom switch. . Currently, active AF is performed at three points on the shooting screen, so about 7 light emitting elements are prepared (depending on the zoom magnification), and when the focal length is on the wide (wide angle) side, Two light emitting elements at the center, one light emitting element from the outside at the middle focal length, and one light emitting element at the center from the outside, and three at the center at the tele (telephoto) focal length The light emitting element is selected as the light emitting element to be lit. Thereafter, in step S22, the CPU 15 drives the filter driving device 33 to retract the iR cut filter 32 from the front surface of the CCD 5 so that the infrared light component attenuated during photographing is not attenuated. This is because infrared light uses an infrared light-emitting element as a light-emitting element of the active AF means because infrared light has a smaller difference in reflectance depending on the subject and can be expected to provide good distance measurement.

  In the following processing, the selected light emitting elements are sequentially emitted to perform the same processing, and the center of gravity of the reflected image when each light emitting element emits light is obtained.

  First, in step S23, illumination accumulation is performed. When executing this routine for the first time, the CPU 15 emits the light emitting element corresponding to the right distance measuring point among the selected three light emitting elements and irradiates the subject with infrared light. Secondly, when executing this routine, the light emitting element corresponding to the center distance measuring point emits light and irradiates infrared light toward the subject. When this routine is executed third, the light emitting element corresponding to the left distance measuring point emits light and irradiates infrared light toward the subject. When the light emitting element is caused to emit light, the amount of light received by the CCD 5 is adjusted by the diaphragm unit 4. When the outside light is bright, the diaphragm 4 is controlled to increase the light emission amount of the light emitting element, and when the external light is dark, the diaphragm 4 is opened to reduce the light emission amount of the light emitting element. The received subject image is converted into an electrical signal by photoelectric conversion processing by the CCD 5 and output to the imaging circuit 6. In step S24, the CPU 15 controls the image pickup circuit 6 to read out only the portion corresponding to the central portion of the output signal from the CCD 5, and outputs the output to the A / D conversion circuit 7 to be converted into a digital signal (image data). Later read and stored in internal memory. This is because it is only necessary to store the portion where the reflection image from the subject is formed. In addition, since the subject in which the reflected light is projected when the light emitting element that emits light is different, the portion where the reflected image from the subject is formed is naturally different. Therefore, the area to be read out differs depending on the light emitting element that emits light. Also, if the focal length of the photographic lens is different, the portion where the reflected image from the subject is formed is different except for the center distance measuring point even in the reflected image from the same subject. Therefore, the area to be read out varies depending on the focal length of the photographing lens. In this way, the processing speed can be increased by reading only a part. At this time, since the output of the A / D conversion circuit 7 is controlled to be input to the CPU 15, the output of the A / D conversion circuit 7 is not temporarily stored in the VRAM 8. Therefore, the image at the time of accumulation of illumination is not displayed on the LCD 10, and an image temporarily stored immediately before that is displayed.

  Proceeding to step S25, non-illumination accumulation is performed with the same aperture as in the illumination accumulation in step S23. The subject image formed on the light receiving surface of the CCD 5 after the amount of light is adjusted by the diaphragm unit 4 is read as an image in step S 26 and stored in the VRAM 8. A signal converted into an electrical signal by photoelectric conversion processing by the CCD 5 is output to the image pickup circuit 6, and the image pickup circuit 6 performs various signal processing on the input signal to generate a predetermined image signal. . This image signal is output to the A / D conversion circuit 7, converted into a digital signal (image data), and then temporarily stored in the VRAM 8. Then, it is output to the D / A conversion circuit 9, converted into an analog signal, converted into an image signal in a form suitable for display, and then displayed as an image on the LCD.

  In step S27, an external light removal operation is performed. This is an act of obtaining data of only a reflection image by a light emitting element by obtaining a difference between illumination accumulation data and non-illumination accumulation data. Since the image formed by the external light can be removed, the center of the reflected image can be easily obtained. Actually, the CPU 15 reads the data corresponding to the data stored in the internal memory of the CPU 15 of the data stored in the VRAM 8, calculates the difference from the data stored in the internal memory of the CPU 15, and performs proper normalization. To remove external light. The calculation result from which the external light is removed is stored in a built-in memory of the CPU 15.

  Next, in step S28, the reflected image is extracted and the center of gravity is calculated. A light image having a relatively high brightness with a steep rise and fall is extracted, and the center of gravity of the light image is obtained. Details will be described later.

  In step 29, it is determined whether or not the processing for the three points for which active AF is to be performed has been completed.

When the processing for the three points is completed, in step S30, the distance from the position of the center of gravity of the reflected image to the three points of the subject is obtained. The distance L to the subject is L = (f + Δz) × B / x from the principle of triangulation
Is required. Where f is the focal length of the photographic lens, Δz is the taking-out amount of the photographic lens, B is the base length (interval between the optical axis of the light emitting means and the optical axis of the photographic lens), and x is the amount of deviation of the reflected image from the optical axis center. It is.

  Then, an in-focus distance D is calculated from the distances to the three subjects according to a predetermined algorithm, and an area for performing the scan AF is determined. This predetermined algorithm is disclosed in Japanese Patent Publication No. 7-069513, Japanese Patent Application Laid-Open No. 64-935, Japanese Patent Application Laid-Open No. 64-48050, Japanese Patent Application Laid-Open No. 64-48051, Japanese Patent Application Laid-Open No. 64-48052, and the like. Will be used. For the in-focus distance D, an appropriate one of the three points is selected and the distance to the subject at that point may be used, or the average of the three points or the average of the appropriate two of the three points may be used. Sometimes used. The average may be a simple average or a weighted average.

  Then, a setting value indicating the position of the focus lens group 3 corresponding to the in-focus distance D is obtained, and this is set as the in-focus position G1 of the active AF.

  If the center of gravity of the reflected image cannot be obtained in step S28, it is predicted that the subject is far away and the intensity of the reflected image is small, so the distance to the subject is set to infinity. When all three points are calculated to have a subject at an infinite distance, the focus AF detection operation position by the scan AF process is set to infinity, so that the focus position of the active AF is changed from infinity to scan AF. A value obtained by subtracting the variable Gs indicating the range is used.

  Thereafter, the process proceeds to step S31, and the iR cut filter 32 retracted from the front surface of the CCD 5 in step S22 is inserted into the front surface of the CCD 5 again.

  The reason why the image during illumination accumulation is not displayed on the LCD 10 in this way is that there is a sense of incongruity because only a part of the image is read out in order to speed up the calculation, and the reflected image of the light emitting element is reflected. This is to prevent the image from being displayed on the LCD 10. In addition, since the non-illuminated image is displayed immediately afterward, the photographer is not given an uncomfortable feeling that the screen freezes.

  Here, details of the extraction of the reflected image and the calculation of the center of gravity in step S28 will be described with reference to FIGS. 4A and 4B.

  First, in step S400, the CPU 15 initializes variables used for calculation. That is, the work area for storing the counters i and k and the optical image data is cleared. In addition, since it is conceivable that a plurality of light images that are considered to be reflected images are detected, a plurality of memory areas for calculation for storing light image data are prepared.

  Next, in step S401, the data of the calculation result from which external light has been removed stored in the built-in memory is read out. This value is d [i]. In step S402, d [i] is compared with the first threshold value Th1. If data equal to or greater than the first threshold value is detected, in step S403, the difference between the values of adjacent pixels of a plurality of pixels (for example, two pixels) is obtained to determine the rising slope of the optical image, and the slope is the second. It is checked whether the threshold value Th2 is greater than or equal to the threshold value Th2. If the rising slope of the optical image is greater than or equal to the second threshold value, the process proceeds to step S404 where the optical image data is stored in the internal memory of the CPU 15. As a result, a light image having a relatively high luminance with a steep rise is detected. If the conditions are not satisfied in steps S402 and S403, the process proceeds to step S413.

In step S404, optical image data is stored as follows. That is, the sum of the luminance d [i] of the signal and the sum d [i] × i of the product of the luminance of the signal and the coordinates are obtained and stored. Further, i is stored as L [k] as coordinates on the left side of the optical image. Sd [k] = d [i] + d [i−1] where Sd [k] is the sum of the luminances of the kth light image and Se [k] is the sum of the product of the luminance and coordinates.
Se [k] = d [i] × i + d [i−1] × (i−1)
It becomes.

  In step S405, the counter i is incremented by 1, and the next pixel is set as a calculation target. In step S406, the calculation result data from which external light has been removed is stored in the built-in memory. This value is d [i]. In step S407, d [i] is compared with the first threshold value Th1. If data equal to or greater than the first threshold is detected, the optical image is still continuing, and thus the process proceeds to step S408 and the optical image data is updated according to the following equation.

Sd [k] = Sd [k] + d [i]
Se [k] = Se [k] + d [i] × i
The operation of updating the optical image data is performed while updating the counter i in step S405 until the condition of step S407 is not satisfied. However, if the detection for all pixels is completed during this process, the fall condition is not satisfied, so the light image being detected is determined to be inappropriate and the data is Clear and immediately proceed to step S415.

  When the condition of step S407 is not satisfied (when data of the first threshold value or more is not detected), it can be determined that the optical image has been completed, and thus it is checked whether or not there is a steep fall. . In step S409, the difference between the values of adjacent pixels of a plurality of pixels (for example, two pixels) is obtained to determine the slope of the fall of the optical image, and it is checked whether the slope is equal to or greater than the second threshold Th2. If the falling slope of the optical image is greater than or equal to the second threshold value, a light image having a relatively high brightness having a steep rising / falling edge has been extracted. Update according to the following formula.

Sd [k] = Sd [k] + d [i] + d [i + 1]
Se [k] = Se [k] + d [i] × i + d [i + 1] × (i + 1)
Further, i is stored as R [k] as coordinates on the right side of the optical image. Then, the counter k is incremented by 1, and the address of the memory storing the optical image data is updated. On the other hand, if the condition is not satisfied in step S409, a light image having a relatively high brightness having a steep rise and fall has not been extracted, and thus the optical image data stored so far is cleared.

  In step S413, the counter i is incremented by 1 and the next pixel is set as a calculation target. In step S414, it is checked whether or not the detection for all the pixels has been completed.

If the detection for all pixels is completed, the center of gravity of the optical image detected in step S415 is obtained. The coordinate Px of the center of gravity of the optical image is Px = Se [k] / Sd [k]
It becomes.

  However, when a plurality of light images are detected, one having R [k] -L [k] within a predetermined range is selected. This is because the size of the reflected image of the light emitting element on the surface of the CCD 5 should be substantially constant, so that only those within a certain range assuming an error are considered to be reflected images by the correct light emitting element. If a plurality of optical images remain, the one having the largest value of Sd [k] / (R [k] −L [k]) is selected. The reason why the largest value of Sd [k] / (R [k] −L [k]) is selected is because the luminance of the reflected image by the light emitting element is maximized because external light is removed. Because.

  Although the sensitivity of each color of the color separation filter arranged in front of the CCD 5 to detect infrared light has been ignored, there is actually a difference in sensitivity. After correcting the data in accordance with the sensitivity, the above-described optical image detection process is performed.

  Next, details of the scan AF executed in step S5 of FIG. 2 will be described.

  FIG. 5 shows a flowchart of the scan AF sequence. FIG. 6 shows the relationship between the high-frequency component amount and the focus lens position when the scan AF is executed. However, this operation is performed only for the area determined according to a predetermined algorithm in the active AF process. For example, when it is determined that there is a subject in the area where the left side scan AF is performed by a predetermined algorithm in the active AF process, the following process is performed in the area where the left side scan AF is performed. Depending on the algorithm of the active AF process, there are cases where two continuous areas such as the left side and the center are selected or all areas (three areas) are selected. In this case, the following processing is performed with the selected plurality of regions as one wide region.

  In step S51 of FIG. 5, the CPU 15 sets a start position and a stop position for driving the focus lens group 3 in order to perform a focus position detection operation by the scan AF process from the result of the active AF process calculation. The set value of the start position set here is an active AF in-focus position (a set value indicating the position of the focus lens group 3 corresponding to the subject distance of the active AF processing calculation result) G1 to a variable Gs indicating a range of scan AF. The value obtained by subtracting. The set value of the stop position is a value obtained by adding a variable Gs indicating the range of the scan AF to the active AF in-focus position (a set value indicating the position of the focus lens group 3 corresponding to the subject distance of the active AF processing calculation result) G1. It becomes. That is, the range in which the scan AF is performed is a predetermined range centered on the subject distance based on the active AF processing calculation result.

  The variable Gs indicating the range of the scan AF is determined in consideration of the focal length of the photographing lens / active AF processing calculation result (subject distance), parallax, distance measurement error assumed in the active AF processing, and the like.

  In general, the focus adjustment operation in an imaging apparatus is for focusing a light beam from a desired subject collected by a photographing optical system on an imaging surface (light receiving surface) of an imaging device (CCD or the like) in a focused state. Is the action. For this purpose, a focus lens group which is a part of the photographing optical system is moved in the optical axis direction to obtain a focused state. The amount of movement in the optical axis direction tends to increase as the subject approaches. Moreover, it tends to increase as the focal length of the photographing lens increases.

  Also, the parallax tends to increase as the subject gets closer and the focal length of the photographic lens becomes longer.

  The distance measurement error includes an adjustment error at the time of manufacturing the image pickup apparatus, a temperature error such as a distortion caused by a change in the environmental temperature of the photographing lens barrel 31, and a mechanical component of each member (CCD 5, light emitting means 30, etc.) constituting the active AF means. A distance measurement error caused by the error, a movement error of the focus lens group 3, and the like are conceivable.

  Therefore, the variable Gs indicating the range of the scan AF becomes a larger value as the distance to the subject obtained from the active AF processing calculation result is shorter and the focal length of the photographing lens is longer. Then, a variable Gs indicating the range of the scan AF is set by adding a coefficient considering a distance measurement error to a value obtained from the distance to the subject and the focal length of the photographing lens. For example, the following formula may be used.

Gs = K1 × f / L + δL
Here, K1 is a constant, L is the distance to the subject, f is the focal length of the photographic lens, and δL is a coefficient relating to distance measurement error and the like.

  In step S52, the CPU 15 drives the focus motor 22 via the second motor drive circuit 19, and moves the focus lens group 3 to the start position set in step S51. Then, scan AF processing for searching for the in-focus position is performed while moving the focus lens group 3 by a predetermined movement amount starting from the start position.

  In step S53, the CPU 15 determines whether or not the focus lens group 3 has reached the end position set in step S51. If the focus lens group 3 has not reached the end position, the CPU 15 controls the imaging means and acquires image data corresponding to the position of the focus lens group 3 at that time. This image data is output to the AF processing circuit 14 via the imaging circuit 6 and the A / D conversion circuit 7, and an AF evaluation value is calculated as shown in step S54. The AF evaluation value is output to the CPU 15 and stored in a calculation memory built in the CPU 15. In the next step S55, the CPU 15 moves the focus lens group 3 by a predetermined movement amount. Thereafter, the process returns to step S53, and the same processing is repeated until the focus lens group 3 reaches the set end position.

  If it is determined in step S53 that the focus lens group 3 has reached the end position, the process proceeds to step S56. In step S56, the CPU 15 calculates the in-focus position based on the AF evaluation value calculated in step S55. Based on the calculation result, the CPU 15 drives the focus motor 22 via the second motor drive circuit 19 in step S57, moves the focus lens group 3 to the in-focus position, and stops at this position. Exit. Then, it progresses to step S6 of FIG.

  This series of operations will be described with reference to FIG.

  For example, in a state where the focus lens group 3 is at the position indicated by A in FIG. 6, the focus lens group 3 first moves from the position A to a position B obtained by subtracting Gs from the distance measurement result of the active AF that is the start position. (Step S52). The scan AF process is executed until the focus lens group 3 starts from this start position and reaches the position C obtained by adding Gs to the active AF distance measurement result, which is the end position (steps S52 to S55). Based on the AF evaluation value acquired in this way, the CPU 15 calculates the in-focus position (step S56). By this calculation, the position of D in FIG. 6, that is, the position of the focus lens group 3 corresponding to the peak value of the high frequency component is obtained as the in-focus position. Thereafter, the CPU 15 drives the focus lens group 3 to that position (step S57).

  In this way, the CCD 5 is used as the light receiving means of the active AF, the distances from the light receiving means output to the plurality of subjects are estimated, the distances to the appropriate subjects are estimated from the results, and the position corresponding to the distance is centered. The position of the focus lens group 3 in which the high frequency component output from the image signal generated by the CCD 5 is the largest is obtained while moving the focus lens group 3 within the set range. In other words, by performing a scan AF process that detects an accurate in-focus position around the approximate distance to the subject obtained by active AF, it can be performed at high speed and accurately with a low-cost configuration that only requires a light projection means. The focus position can be detected. In addition, by estimating the distances to a plurality of subjects and then performing scan AF processing, it is possible to detect in-focus positions for a wide variety of subjects in the screen.

  Further, by not displaying the image at the time of storing the illumination on the LCD 10, an uncomfortable feeling such as “a part of the image is temporarily displayed” or “an image in which the reflection image of the light emitting element is reflected” is displayed on the LCD. It is possible to avoid a certain image from being displayed on the LCD 10. Then, immediately after the non-illuminated accumulated image is displayed, the adverse effect of giving the photographer an uncomfortable feeling that the screen freezes is avoided.

  For convenience of explanation, the number of distance measuring points has been described as three, but the present invention does not limit the number of distance measuring points to three. The present invention can be applied to other distance measuring points. The same applies to the following embodiments.

(Second Embodiment)
In the second embodiment, the basic configuration and the basic operation procedure are the same as those in the first embodiment, and are shown in the block diagram of the imaging apparatus in FIG. 1 and the flowchart in FIG.

  In this embodiment, the processing time is shortened by simultaneously lighting a plurality (three) of light emitting elements. A flowchart of active AF in the present embodiment, which is different from the first embodiment, will be described with reference to FIG.

  First, in step S700, the CPU 15 reads information on the focal length of the photographing optical system set by operating a zoom switch (not shown) of the operation switches 24. In step S701, a light emitting element to be lit is selected from a plurality of light emitting elements in the light emitting means 30. This is a process for making the position of the luminous flux irradiated toward the subject the same on the photographing screen without mechanically moving the light emitting element even when the zooming operation is performed by operating the zoom switch. . Now, since active AF is performed at three points on the shooting screen, about seven light-emitting elements are prepared (depending on the zoom magnification). One central light-emitting element, the second two from the outside and one central light-emitting element at the middle focal length, and the three central light-emitting elements at the tele-side focal length Select as light emitting element. Thereafter, in step S702, the CPU 15 drives the filter driving device 33 to retract the iR cut filter 32 from the front surface of the CCD 5 so as not to attenuate the infrared light component that is attenuated during photographing. This is because infrared light uses an infrared light-emitting element as a light-emitting element of the active AF means because infrared light has a smaller difference in reflectance depending on the subject and can be expected to provide good distance measurement.

  In the following processing, the selected light emitting elements emit light simultaneously and the same processing is performed, and the center of gravity of the reflected image when each light emitting element emits light is obtained.

  First, in step S703, illumination accumulation is performed. The CPU 15 causes the selected three light emitting elements to emit light and irradiates infrared light toward the subject. At the same time, the amount of light received by the CCD 5 by the diaphragm 4 is adjusted. When the outside light is bright, the aperture 4 is controlled to increase the light emission amount of the aperture light emitting element, and when the external light is dark, the aperture 4 is opened to reduce the light emission amount of the light emitting element.

  The received subject image is converted into an electrical signal by photoelectric conversion processing by the CCD 5 and output to the imaging circuit 6. In step S704, the CPU 15 controls the image pickup circuit 6 to read out only the portion corresponding to the central portion of the output signal from the CCD 5, and outputs the output to the A / D conversion circuit 7 to convert it into a digital signal (image data). Read later and store in internal memory. This is because it is only necessary to store the portion where the reflection image from the subject is formed. In addition, since the subject in which the reflected light is projected when the light emitting element that emits light is different, the portion where the reflected image from the subject is formed is naturally different. Therefore, the area to be read out differs depending on the light emitting element that emits light. Also, if the focal length of the photographic lens is different, the portion where the reflected image from the subject is formed is different except for the center distance measuring point even in the reflected image from the same subject. Therefore, the area to be read out differs depending on the focal length of the photographing lens. In this way, the processing speed can be increased by reading only a part. At this time, since the output of the A / D conversion circuit 7 is controlled to be input to the CPU 15, the output of the A / D conversion circuit 7 is not temporarily stored in the VRAM 8. Therefore, the image at the time of accumulation of illumination is not displayed on the LCD 10, and an image temporarily stored immediately before that is displayed.

  Proceeding to step S705, non-illumination accumulation is performed with the same aperture as that during the illumination accumulation in step S703. The subject image formed on the light receiving surface of the CCD 5 after the amount of light is adjusted by the diaphragm unit 4 is read as an image in step S706 and stored in the VRAM 8. A signal converted into an electrical signal by photoelectric conversion processing by the CCD 5 is output to the image pickup circuit 6, and the image pickup circuit 6 performs various signal processing on the input signal to generate a predetermined image signal. . This image signal is output to the A / D conversion circuit 7, converted into a digital signal (image data), and then temporarily stored in the VRAM 8. Then, it is output to the D / A conversion circuit 9, converted into an analog signal, converted into an image signal in a form suitable for display, and then displayed as an image on the LCD.

  Proceeding to step S707, an external light removing operation is performed. This is an act of obtaining data of only a reflection image by a light emitting element by obtaining a difference between illumination accumulation data and non-illumination accumulation data. Since the image formed by the external light can be removed, the center of the reflected image can be easily obtained. Actually, the CPU 15 reads the data corresponding to the data stored in the internal memory of the CPU 15 of the data stored in the VRAM 8, calculates the difference from the data stored in the internal memory of the CPU 15, and performs proper normalization. To remove external light. The calculation result from which the external light is removed is stored in a built-in memory of the CPU 15.

Next, in step S708, the reflected image is extracted, the center of gravity is calculated, and the distance to the subject at each distance measuring point that emits light from the light emitting element is obtained from the result. As for the center of gravity of the reflected image, a light image having a relatively high brightness with a steep rise and fall is extracted, and the center of gravity of the light image is obtained. Since the details are the same as those of the first embodiment, the description thereof is omitted. The distance L from the position of the center of gravity of the reflected image to the three subjects is calculated from the principle of triangulation L = (f + Δz) × B / x
Is required. Where f is the focal length of the photographic lens, Δz is the taking-out amount of the photographic lens, B is the base length (interval between the optical axis of the light emitting means and the optical axis of the photographic lens), and x is the amount of deviation of the reflected image from the optical axis center. It is.

  As long as the subject is within the shootable range, it is possible to determine which light emitting element is the position of the reflected image even if a plurality of light emitting elements are lit at the same time. Since three light emitting elements are now turned on, a reflected image exists as shown in FIG. 8A, for example. As shown in the figure, when three light emitting elements are turned on, the range where the reflected image by the right light emitting element exists is within the rectangular range on the right side, and the range where the reflected image by the adjacent central light emitting element exists (middle). (The rectangular area) does not overlap. The same applies to the reflection image by the center or left light emitting element. Therefore, it is possible to extract a reflection image by each light emitting element and to measure each point even if the light is simultaneously turned on. In the active AF optical system, if there is a subject at a distance that can be taken and a subject with a certain margin on the camera side, it is designed so that the reflected images from the subject do not overlap. Has been.

  However, it is difficult to discriminate the reflected image from the adjacent light emitting element beyond the distance that the subject is assumed to be closer than the distance that can be photographed. An example is shown in FIG. 8B. The example shown at the bottom of FIG. 8B shows a case where there is a subject at the assumed distance at the center and left, and the subject exists outside the assumed distance (closer to the assumed distance) on the right. In this case, the reflection image from the subject by the right light emitting element is generated in a range in which the reflection image from the subject by the central light emitting element is to be formed, as shown in black in the drawing. Therefore, it becomes impossible to distinguish the reflected images from the subject by the light emitting elements at the center and the right.

  Therefore, in the present embodiment, as shown in FIG. 8B, the reflected light is expected to exist when the left subject is closer than the assumed distance to the left of the range where the reflected light from the subject by the left light emitting element is received. This area is provided, and processing for making this part symmetrical with respect to the extraction of the reflected image is also performed to eliminate this problem. FIG. 8B is a portion indicated as OB range. In FIG. 8B, a black circle (•) is reflected light when the subject is closer than the assumed distance, and the reflected light is generated in a range where the reflected light of the subject by the adjacent light emitting element exists. White circles (◯) in the figure are reflected light when the subject is at an assumed distance, and the reflected light of the subject by the light emitting element is generated in the assumed range.

  When all of the three points are outside the assumed distance, it is as shown at the top of FIG. 8B. Reflected light from the subject at the left point in the OB range, reflected light from the subject at the center point in the left range, and reflected light from the subject at the right point in the center range. Therefore, it is possible to extract a reflected image by each of the three light emitting elements and to measure the distance of each point. However, in this case, since it is difficult to take a focused photograph because the subject is too close, a warning to that effect is given in step S712, and then the process proceeds to step S711. In step S702, the iR cut filter 32 retracted from the front surface of the CCD 5 is inserted again into the front surface of the CCD 5, and the process returns.

  Further, when only the right side is within the assumed distance, it becomes as shown in the second part of FIG. 8B, and distance measurement of each point is possible. However, since the effective distance measurement result is only by the right light emitting element, the focusing distance D set in the subsequent step 710 is determined by the distance measurement result by the right light emitting element.

  When only the center is within the assumed distance, it becomes as shown in the third part of FIG. 8B, and the reflected image of the center and the right point occurs in the range where the reflected image of the same center point is generated. Therefore, only the center light emitting element is regarded as an effective distance measurement result, and only the center light emitting element is turned on in the subsequent step 710 to perform AF again, and the focusing distance D is determined by the distance measuring result by the center light emitting element. The

  When only the left side is within the assumed distance, it becomes as shown in the fourth part of FIG. 8B, and the reflection image of the center and the left point occurs in the range where the reflection image of the left point is the same. Therefore, only the left light emitting element is regarded as an effective distance measurement result, and only the left light emitting element is turned on in the subsequent step 710 and re-AF is performed. The focus distance D is determined by the distance measurement result by the left light emitting element. The

  When the right side and the center are within the assumed distance, it becomes as shown in the fifth of FIG. 8B, and distance measurement of each point is possible. However, since the effective distance measurement result is based on the right and center light emitting elements, the focusing distance D set in the subsequent step 710 is determined by the distance measurement result obtained on the right and center light emitting elements.

  When the right side and the left side are within the assumed distance, as shown in FIG. 8B, the reflection image of the center and the left point occurs in the range where the reflection image of the left point is the same. Therefore, the effective distance measurement result is obtained by using the right and left light emitting elements, and only the left light emitting element is turned on and re-AF is performed in a later step 710, and the focusing distance D is determined by the distance measurement results by the right and left light emitting elements. Is determined.

  When the center and the left side are within the assumed distance, as shown in FIG. 8B, the reflection image of the center and the right point occurs in the range where the reflection image of the same center point is generated. Therefore, the effective distance measurement result is obtained by using the center and left light emitting elements, and only the center light emitting element is turned on in the subsequent step 710 to perform AF again. Is determined.

  In step S709, it is determined whether all three points are outside the assumed distance, and if all three points are outside the assumed distance, the process proceeds to step S712 to give a warning.

  If it is within the assumed range, the process proceeds to step S710. If necessary, re-AF (active AF) is performed, and the reflected image is extracted and its center of gravity is calculated in the same manner as in step S708. The distance to the subject at each distance measuring point is obtained.

  Then, an in-focus distance D is calculated according to a predetermined algorithm from the three effective distances to the subject, and an area for performing the scan AF is determined. The predetermined algorithm is disclosed in Japanese Patent Publication No. 7-069513, Japanese Patent Application Laid-Open No. 64-935, Japanese Patent Application Laid-Open No. 64-48050, Japanese Patent Application Laid-Open No. 64-48051, Japanese Patent Application Laid-Open No. 64-48052, and the like. The algorithm described is used.

  Then, a setting value indicating the position of the focus lens group 3 corresponding to the in-focus distance D is obtained, and this is set as the in-focus position G1 of the active AF.

  If the center of gravity of the reflected image cannot be obtained in step S708, it is predicted that the subject is far away and the intensity of the reflected image is small, so the distance to the subject is set to infinity. When all three points are calculated to have a subject at an infinite distance, the focus AF detection operation position by the scan AF process is set to infinity, so that the focus position of the active AF is changed from infinity to scan AF. A value obtained by subtracting the variable Gs indicating the range is used.

  Thereafter, the process proceeds to step S711, and the iR cut filter 32 retracted from the front surface of the CCD 5 in step S702 is inserted into the front surface of the CCD 5 again.

  The reason why the image during illumination accumulation is not displayed on the LCD 10 in this way is that there is a sense of incongruity because only a part of the image is read out in order to speed up the calculation, and the reflected image of the light emitting element is reflected. This is to prevent the image from being displayed on the LCD 10. In addition, since the non-illuminated image is displayed immediately afterward, the photographer is not given an uncomfortable feeling that the screen freezes.

  Naturally, when a warning is given in step S712, the scan AF in step S5 in FIG. 2 is not executed.

  In this way, the CCD 5 is used as the light receiving means of the active AF, the distances from the light receiving means output to the plurality of subjects are estimated, the distances to the appropriate subjects are estimated from the results, and the position corresponding to the distance is centered. The position of the focus lens group 3 in which the high frequency component output from the image signal generated by the CCD 5 is the largest is obtained while moving the focus lens group 3 within the set range. In other words, by performing scan AF processing that detects an accurate in-focus position around the approximate distance to the subject obtained by active AF, it is possible to achieve high-speed and accurate with a low-cost configuration by simply adding a light projection means. It was possible to detect the in-focus position. In addition, by simultaneously lighting a plurality of light emitting elements, it is possible to estimate the distance to a plurality of subjects at a further high speed, and by approximating the distance to a plurality of subjects and then performing a scan AF process, The focus position can be detected for a wide variety of subjects on the screen.

(Third embodiment)
In the third embodiment, the basic configuration and the basic operation procedure are the same as those in the first embodiment, and are shown in the block diagram of the imaging apparatus in FIG. 1 and the flowchart in FIG.

  In the present embodiment, in the macro mode, first, the scan AF is executed in the macro area, thereby specifying a certain distance of the subject. Then, active AF is performed by simultaneously lighting the light emitting elements at a position where the subject is within the assumed distance. A flowchart of active AF in the present embodiment, which is different from the first embodiment, will be described with reference to FIG.

  First, in step S900, it is determined whether or not the macro mode is set. If it is not set to the macro mode, it is considered that there is no subject outside the assumed distance, and thus the process proceeds to step S904.

  If the macro mode is set, scan AF is performed in the macro imaging region in step S901. The macro shooting area varies depending on the specifications of the camera and the like, but ranges from approximately 70 cm to the shortest shooting distance of the shooting lens. The scan AF performed here is equivalent to the scan AF executed in step S5 of FIG. 2, and the scan range is limited to the macro imaging region.

  The result is determined in step S902. If the subject is present in the macro area and the position of the focus lens group 3 that can be determined to be in focus exists, it is determined that the focus is in focus, the AF operation is terminated, and the process returns. This in-focus determination is determined to be in-focus when the evaluation value (AF evaluation value) indicating the high-frequency component output from the image signal is the largest and the AF evaluation value is greater than or equal to a predetermined amount. Therefore, even when a subject exists in the macro area, it may be determined that the subject is not in focus when the subject is extremely dark or the subject contract is extremely low.

  If it is not determined to be in focus, in step S903, as a result of scan AF in step S901, if all three points are determined to be out of the assumed distance range (closer to the lens shooting distance), in step S913 A warning to that effect is issued, the AF operation is terminated, and the process returns.

  If there is a distance measuring point within the assumed distance range, the process proceeds to step S904 to start the active AF process.

  In step S <b> 904, the CPU 15 reads information related to the focal length of the photographing optical system set by operating a zoom switch (not shown) of the operation switches 24. In step S905, a light emitting element to be lit is selected from a plurality of light emitting elements in the light emitting means 30. This is a process for making the position of the luminous flux irradiated toward the subject the same on the photographing screen without mechanically moving the light emitting element even when the zooming operation is performed by operating the zoom switch. . Now, since active AF is performed at three points on the shooting screen, about seven light-emitting elements are prepared (depending on the zoom magnification). One central light-emitting element, the second two from the outside and one central light-emitting element at the middle focal length, and the three central light-emitting elements at the tele-side focal length Select as light emitting element. Further, based on the result of the scan AF executed in S901, ranging points outside the assumed distance range are excluded.

  Thereafter, in step S906, the CPU 15 drives the filter driving device 33 to retract the iR cut filter 32 from the front surface of the CCD 5 so as not to attenuate the infrared light component attenuated during photographing.

  In the following processing, the selected light emitting elements emit light simultaneously and the same processing is performed, and the center of gravity of the reflected image when each light emitting element emits light is obtained.

  First, in step S907, illumination accumulation is performed. The CPU 15 emits the selected light emitting element to emit infrared light toward the subject. At the same time, the amount of light received by the CCD 5 by the diaphragm 4 is adjusted. When the outside light is bright, the diaphragm 4 is controlled to increase the light emission amount of the light emitting element, and when the outside light is dark, the diaphragm 4 is opened to reduce the light emission amount of the light emitting element.

  The received subject image is converted into an electrical signal by photoelectric conversion processing by the CCD 5 and output to the imaging circuit 6. The CPU 15 controls the image pickup circuit 6 to read out only the portion corresponding to the central portion of the output signal from the CCD 5, and outputs the output to the A / D conversion circuit 7, which is converted into a digital signal (image data) and read. Store in memory. This is because it is only necessary to store the portion where the reflection image from the subject is formed. In addition, since the subject in which the reflected light is projected when the light emitting element that emits light is different, the portion where the reflected image from the subject is formed is naturally different. Therefore, the area to be read out differs depending on the light emitting element that emits light. Also, if the focal length of the photographic lens is different, the portion where the reflected image from the subject is formed is different except for the center distance measuring point even in the reflected image from the same subject. Therefore, the area to be read out differs depending on the focal length of the photographing lens. In this way, the processing speed can be increased by reading only a part. At this time, since the output of the A / D conversion circuit 7 is controlled to be input to the CPU 15, the output of the A / D conversion circuit 7 is not temporarily stored in the VRAM 8. Therefore, the image at the time of accumulation of illumination is not displayed on the LCD 10, and an image temporarily stored immediately before that is displayed.

  Proceeding to step S908, non-illumination accumulation is performed with the same aperture as in the illumination accumulation of step S907. The subject image formed on the light receiving surface of the CCD 5 after the amount of light is adjusted by the diaphragm 4 is read out and stored in the VRAM 8. A signal converted into an electrical signal by photoelectric conversion processing by the CCD 5 is output to the image pickup circuit 6, and the image pickup circuit 6 performs various signal processing on the input signal to generate a predetermined image signal. This image signal is output to the A / D conversion circuit 7, converted into a digital signal (image data), and then temporarily stored in the VRAM 8. Then, it is output to the D / A conversion circuit 9, converted into an analog signal, converted into an image signal in a form suitable for display, and then displayed as an image on the LCD.

  In step S909, an external light removal operation is performed. This is an act of obtaining data of only a reflection image by a light emitting element by obtaining a difference between illumination accumulation data and non-illumination accumulation data. Since the image formed by the external light can be removed, the center of the reflected image can be easily obtained. Actually, the CPU 15 reads the data corresponding to the data stored in the internal memory of the CPU 15 of the data stored in the VRAM 8, calculates the difference from the data stored in the internal memory of the CPU 15, and performs proper normalization. To remove external light. The calculation result from which the external light is removed is stored in a built-in memory of the CPU 15.

Next, in step S910, the reflected image is extracted, the center of gravity is calculated, and the distance to the subject at each distance measuring point that emits light from the light emitting element is obtained from the result. As for the center of gravity of the reflected image, a light image having a relatively high brightness with a steep rise and fall is extracted, and the center of gravity of the light image is obtained. Since the details are the same as those of the first embodiment, the description thereof is omitted. The distance L from the position of the center of gravity of the reflected image to the three subjects is calculated from the principle of triangulation L = (f + Δz) × B / x
Is required. Where f is the focal length of the photographic lens, Δz is the taking-out amount of the photographic lens, B is the base length (interval between the optical axis of the light emitting means and the optical axis of the photographic lens), and x is the amount of deviation of the reflected image from the optical axis center. It is.

  Then, an in-focus distance D is calculated according to a predetermined algorithm using the obtained distance to the subject, and an area for performing the scan AF is determined.

  Then, a setting value indicating the position of the focus lens group 3 corresponding to the in-focus distance D is obtained, and this is set as the in-focus position G1 of the active AF.

  Similar to the first and second embodiments, when the center of gravity of the reflected image cannot be obtained, the distance to the subject is set to infinity. When all three points are calculated to have a subject at an infinite distance, the focus AF detection operation position by the scan AF process is set to infinity, so that the focus position of the active AF is changed from infinity to scan AF. A value obtained by subtracting the variable Gs indicating the range is used.

  Thereafter, the process proceeds to step S912, and the iR cut filter 32 retracted from the front surface of the CCD 5 in step S906 is inserted into the front surface of the CCD 5 again.

  The reason why the image during illumination accumulation is not displayed on the LCD 10 in this way is that there is a sense of incongruity because only a part of the image is read out in order to speed up the calculation, and the reflected image of the light emitting element is reflected. This is to prevent the image from being displayed on the LCD 10. In addition, since the non-illuminated image is displayed immediately afterward, the photographer is not given an uncomfortable feeling that the screen freezes.

  Naturally, when a warning is given in step S913, the scan AF in step S5 in FIG. 2 is not executed.

  The scan AF executed in step S901 determines a distance measurement point that is outside the assumed distance range (closer to the lens photographing distance) on the premise that AF (active AF and scan AF) is performed again even in the macro area. In this case, the scan AF executed in step S901 can be performed at a high speed with a rough scan width.

  Even if the macro mode is not specified (for example, because of forgetting to set), there may be a subject nearby, so the above algorithm may be executed even if the macro mode is not set. In this case, it is preferable to execute the above-described algorithm in a mode other than the distant view mode.

  In this way, the CCD 5 is used as the light receiving means of the active AF, the distances from the light receiving means output to the plurality of subjects are estimated, the distances to the appropriate subjects are estimated from the results, and the position corresponding to the distance is centered. The position of the focus lens group 3 in which the high frequency component output from the image signal generated by the CCD 5 is the largest is obtained while moving the focus lens group 3 within the set range. In other words, by performing scan AF processing that detects an accurate in-focus position around the approximate distance to the subject obtained by active AF, it is possible to achieve high-speed and accurate with a low-cost configuration by simply adding a light projection means. It was possible to detect the in-focus position. By performing scan AF in the macro area prior to the active AF and knowing whether or not the subject exists at a shorter distance than the assumed distance, a “reflected image is formed outside the assumed range, making it difficult to separate the reflected image. The problem of lighting multiple light-emitting elements at the same time has been resolved.

  Then, by estimating the distances to a plurality of subjects and then performing scan AF processing, it is possible to detect in-focus positions for a wide variety of subjects on the screen.

(Fourth embodiment)
In the fourth embodiment, the basic configuration and the basic operation procedure are the same as those in the first embodiment, and are shown in the block diagram of the imaging apparatus in FIG. 1 and the flowchart in FIG.

  In the present embodiment, first, active AF is performed on the center subject, and it is determined whether to perform other two points of active AF or a short distance warning according to the result. A flowchart of active AF in this embodiment different from the first embodiment will be described with reference to FIG.

  First, in step S1000, the CPU 15 drives the filter driving device 33 to retract the iR cut filter 32 from the front surface of the CCD 5 so as not to attenuate the infrared light component that is attenuated during photographing.

  In step S1001, active AF is performed only at the center point. Since the light emitting element for irradiating the central subject with the light flux is determined regardless of the focal length of the photographing lens, the light emitting element is turned on to perform active AF. The specific procedure is the same as in the first, second, and third embodiments. Illumination accumulation, non-illumination accumulation, and external light removal are performed, and the center of gravity position of the reflected image is obtained from the result, and the distance to the subject is determined. calculate. Since only the light emitting element for irradiating the central subject with the luminous flux is turned on, it is possible to extract the reflected image and obtain the distance regardless of the distance of the subject.

  In step S1002, the distance measurement result in step S1001 is evaluated. As a result, if there is a center distance measurement result outside the assumed distance range (closer to the lens photographing distance), the process proceeds to step S1006 to give a warning to that effect and return.

  When the center distance measurement result is within the assumed distance range, active AF is performed at the right and left distance measurement positions in step S1003. The specific procedure is the same as before. A light emitting element to be lit is selected from the focal length information, illumination accumulation, non-illumination accumulation, and external light removal are performed, and the center of gravity position of the reflected image is obtained from the result, and the distance to the subject is calculated. From the distance measurement result at the center distance measurement position, it can be estimated that the left and right subjects are also within the assumed distance range. This is because the area occupied on the screen increases when an object other than a considerably small object is present near the assumed distance, so it cannot be considered that it exists only at one of the right and left distance measuring points and does not exist at the center. Even in such a case, since the corresponding subject is very small in that case, there is a high possibility that the light beam from the light emitting element will not be hit, and the distance measurement is hardly adversely affected.

  On the other hand, there is rarely a situation where the subject exists near the expected distance only in the center and does not exist on the left and right. In such a case as well, the subject is very small and there is a high possibility that the light beam from the light emitting element will not be hit, and the distance measurement is hardly adversely affected.

  When the three-point distance measurement is completed, the process proceeds to step S1004, and the focus distance D is calculated according to a predetermined algorithm using the obtained distance to the subject, and the area for performing the scan AF is determined.

  Then, a setting value indicating the position of the focus lens group 3 corresponding to the in-focus distance D is obtained, and this is set as the in-focus position G1 of the active AF.

  The process when the center of gravity of the reflected image is not obtained is the same as before.

  Thereafter, the process proceeds to step S1005, and the iR cut filter 32 retracted from the front surface of the CCD 5 in step S1000 is inserted into the front surface of the CCD 5 again.

  Naturally, when a warning is given in step S1006, the scan AF in step S5 in FIG. 2 is not executed.

  In this way, the CCD 5 is used as the light receiving means of the active AF, the distances from the light receiving means output to the plurality of subjects are estimated, the distances to the appropriate subjects are estimated from the results, and the position corresponding to the distance is centered. The position of the focus lens group 3 in which the high frequency component output from the image signal generated by the CCD 5 is the largest is obtained while moving the focus lens group 3 within the set range. In other words, by performing scan AF processing that detects an accurate in-focus position around the approximate distance to the subject obtained by active AF, it is possible to achieve high-speed and accurate with a low-cost configuration by simply adding a light projection means. It was possible to detect the in-focus position. First, by performing active AF at the center distance measuring point and knowing whether or not the subject is closer than the assumed distance, a reflection image is formed outside the assumed range, making it difficult to separate the reflection image. The problem of lighting multiple light-emitting elements at the same time has been resolved.

  Then, by estimating the distances to a plurality of subjects and then performing scan AF processing, it is possible to detect in-focus positions for a wide variety of subjects on the screen.

(Other embodiments)
In addition, an object of each embodiment is to supply a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (or CPU) of the system or apparatus Needless to say, this can also be achieved by reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. It goes without saying that the CPU or the like provided in the expansion card or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

It is a block diagram which shows the structure of the imaging device of the 1st thru | or 4th embodiment of this invention. It is a flowchart for demonstrating operation | movement of the imaging device of 1st thru | or 4th embodiment. 5 is a flowchart for explaining an operation of active AF according to the first embodiment. It is a flowchart for demonstrating the operation | movement of the optical image detection in the active AF of 1st thru | or 4th embodiment. It is a flowchart for demonstrating the operation | movement of the optical image detection in the active AF of 1st thru | or 4th embodiment. It is a flowchart for demonstrating operation | movement of the scan AF of 1st thru | or 4th embodiment. It is a figure which shows the relationship between the high frequency component amount at the time of performing the scan AF of 1st thru | or 4th embodiment, and a focus lens position. It is a flowchart for demonstrating the operation | movement of active AF of 2nd Embodiment. It is explanatory drawing of the position where a reflected image is formed. It is explanatory drawing of the position where a reflected image is formed. It is a flowchart for demonstrating operation | movement of active AF of 3rd Embodiment. It is a flowchart for demonstrating operation | movement of active AF of 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Zoom lens group 3 Focus lens group 4 Aperture 5 Solid-state image sensor 6 Imaging circuit 7 A / D conversion circuit 8 Memory (VRAM)
9 D / A conversion circuit 10 Image display device 11 Compression / decompression circuit 12 Memory for storage 13 AE processing circuit 14 Scan AF processing circuit,
15 CPU
16 Timing generator (TG)
17 CCD driver 18 First motor drive circuit 19 Second motor drive circuit 20 Third motor drive circuit 21 Aperture drive motor 22 Focus drive motor 23 Zoom drive motor 24 Operation switch 25 EEPROM
26 Battery 28 Strobe light emitting unit 27 Switching circuit 30 Light emitting means (LED)
31 Shooting lens barrel 32 iR cut filter 33 Filter drive unit.

Claims (11)

A photographing optical system including a focusing lens that moves in the optical axis direction to form a subject image on a target focal plane;
Imaging means for photoelectrically converting a subject image formed by the photographing optical system to generate an electrical image signal;
A light projecting means for irradiating a subject with a light beam;
Calculating means for calculating a rough distance to the subject based on a position of an image signal generated by the imaging means when the imaging means receives light emitted from the light projecting means and reflected by the subject; ,
A lens driving unit that scans the focus adjustment lens over a predetermined range before and after the central position in the optical axis direction, with the position in the optical axis direction of the focus adjustment lens for focusing on the approximate distance as a central position;
Focus detection means for obtaining the position of the focus adjustment lens for focusing on the subject based on the image signal generated by the imaging means at each position of the focus adjustment lens when the focus adjustment lens is scanned. When,
An imaging apparatus comprising:   The light projecting unit has a plurality of light emitting elements larger than the number of the plurality of focus detection areas provided in the photographing screen, and the same number of light emitting elements as the number of the focus detection areas from the plurality of light emitting elements. The imaging apparatus according to claim 1, wherein the imaging device is selected, and the plurality of selected light emitting elements emit light sequentially.   The light projecting means has a plurality of light emitting elements larger than the number of focus detection areas provided in the photographing screen, and the same number of light emitting elements as the number of the focus detection areas from the plurality of light emitting elements. The selected plurality of light emitting elements are configured to emit light at the same time, and based on the position on the imaging unit of a reflected image irradiated from the light emitting elements and reflected by the subject, the outline The imaging apparatus according to claim 1, further comprising a determination unit that determines the validity of the distance.   2. The method according to claim 1, wherein when the light emitted from the light projecting unit and reflected by the subject is imaged by the imaging unit, only a partial region of an image signal formed by the imaging unit is read out. The imaging apparatus according to 2 or 3.   The imaging apparatus according to claim 4, wherein the partial area is made different depending on a light emitting element that emits light.   The imaging apparatus according to claim 4, wherein the partial area is made different according to a focal length of the photographing optical system.   Based on the image signal generated by the imaging means, further comprising a detecting means for detecting whether or not the subject exists at a shorter distance than the assumed distance, and based on the detection result of the detecting means, The imaging device according to claim 1, wherein a light emitting element that emits light is selected from a plurality of light emitting elements provided in the light projecting unit.   By causing one of a plurality of light emitting elements provided in the light projecting unit to emit light and causing the light reflected by the subject to be imaged by the imaging unit, the distance to the subject is closer than expected. It further comprises detection means for detecting whether or not it exists, and based on the detection result of the detection means, it is determined whether or not other light emitting elements of the plurality of light emitting elements are caused to emit light. The imaging device according to claim 1. An imaging optical system including a focusing lens that moves in the optical axis direction to form a subject image on a target focal plane, and an electrical image signal obtained by photoelectrically converting the subject image formed by the imaging optical system An imaging apparatus control method for controlling an imaging apparatus comprising: an imaging unit that generates a light source; and a light projecting unit that irradiates a subject with a light beam,
A calculation step of calculating a rough distance to the subject based on a position of an image signal generated by the imaging unit when the imaging unit receives light irradiated from the light projecting unit and reflected by the subject; ,
A lens driving step of scanning the focus adjustment lens over a predetermined range before and after the center position in the optical axis direction, with the position in the optical axis direction of the focus adjustment lens for focusing on the approximate distance as a center position;
A focus detection step for obtaining a position of the focus adjustment lens for focusing on the subject based on an image signal generated by the imaging unit at each position of the focus adjustment lens when the focus adjustment lens is scanned. When,
An image pickup apparatus control method comprising:   A program for causing a computer to execute the method for controlling an imaging apparatus according to claim 9.   A storage medium storing the program according to claim 10 in a computer-readable manner.

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