JP2008129466A - Imaging apparatus and imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid the lowering of focus control accuracy due to influence of a light source which exists in the field of a light source detection sensor. <P>SOLUTION: The imaging apparatus 1 includes: a focus detection means 201 (211a and 211b) to detect the focus state of a photographic optical system by using light from the photographic optical system; first and second light receiving sensors 213a and 213b to detect light having a different wavelength region from each other out of the light from the photographic optical system; and a control means 100 capable of generating information used for focus control by using the detected result of the focus state and signals from the first and the second light receiving sensors. The control means changes a method for generating the information used for the focus control according to the superposed state of the field of the first and the second light receiving sensors. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging apparatus that performs focus control, and more particularly to an imaging apparatus that performs focus control according to information about a light source.

  There is a so-called TTL (Through The Lens) phase difference detection method as an AF (autofocus) method for an imaging apparatus such as a digital single lens reflex camera. In a camera that employs a TTL phase difference detection method, light incident from a photographing lens is separated by a light separation member such as a mirror, and transmitted light is guided to an imaging system and reflected light is guided to a focus detection system. Thus, in the TTL phase difference detection type camera, the imaging system and the focus detection system are provided separately. For this reason, the following problems arise.

  The spectral sensitivity characteristics of the imaging system are usually most sensitive to light of about 400 to 650 nm in order to give color reproducibility that matches the characteristics of the human eye in the case of a general silver salt film. ing.

  On the other hand, a silicon photodiode constituting an imaging device such as a CMOS sensor used in an imaging system generally has a sensitivity peak at about 800 nm, and has a sensitivity up to about 1100 nm on the long wavelength side. However, in order to place importance on color reproducibility, light having a wavelength outside the above frequency range is blocked by a filter at the expense of sensitivity.

  In addition, a photoelectric conversion element as a sensor that performs focus detection by the phase difference detection method generally has a sensitivity up to about 1100 nm. However, the focus detection can be performed even on a low-luminance subject, and an accurate focus detection can be performed by irradiating the subject with auxiliary light in the near-infrared region (about 700 nm) from the camera under a low luminance. In many cases, it has sensitivity up to a long wavelength region.

  FIG. 10 shows spectral sensitivities of various light sources, image sensors, and auxiliary light. The horizontal axis indicates the wavelength. The vertical axis indicates the relative focus position due to relative energy or chromatic aberration of the lens. In the figure, C represents chromatic aberration of the photographing lens, and B, G, and R represent the respective spectral sensitivities of the blue pixel, green pixel, and red pixel of the primary color image sensor. F indicates a fluorescent lamp, L indicates a flood lamp, and A indicates the spectral sensitivity of the auxiliary light described above.

  From the figure, it is understood that the wavelength component of the fluorescent lamp contains almost no wavelength component longer than 620 nm, but the flood lamp has a higher relative sensitivity as the wavelength becomes longer.

  On the other hand, the focal position of the chromatic aberration C of the lens changes according to the wavelength, and the focal length increases as the wavelength becomes longer.

  Therefore, when a focus detection sensor having a maximum sensitivity at 700 nm is used, the focus position to be detected differs between the fluorescent lamp and the flood lamp with a small long wavelength component, and as a result, the focus on the image sensor is also shifted. End up.

  A camera that corrects the focus position is disclosed in Patent Document 1 for the problem that the focus position detected by the focus detection system shifts in accordance with the spectral sensitivity of the light source.

In this camera, the output of two types of light source detection sensors having different spectral sensitivities are compared to determine the type of the light source, and the focus position is corrected to correct the focus shift due to the spectral characteristics of the light source.
JP-A-62-174710 (page 6, upper left column, line 2 to page 7, upper left column, line 3, FIG. 9 etc.)

  However, in the camera disclosed in Patent Document 1, the field of view of the two types of light source detection sensors (visible light sensor and infrared light sensor) on the photographing screen is shifted depending on the defocus state of the photographing optical system. Becomes larger.

  Here, the relationship between the visual field of the visible light sensor and the infrared light sensor will be described. FIG. 11A shows the field of view shift of both sensors when the defocus amount is small. When the defocus amount is small, the fields of view of both sensors almost coincide (overlap). For this reason, for example, even if there is a strong light source in the peripheral part in the field of view, an error hardly occurs in the outputs of both sensors.

  On the other hand, FIG. 11B shows the visual field shift of both sensors when the defocus amount is large. When the defocus amount is large, the field of view of both sensors becomes large. For example, when there is a strong light source such as the sun in the periphery of the field of the visible light sensor, the output from the visible sensor is output from the infrared light sensor. It becomes very large compared to the output of.

  As described above, when the defocus amount is large, the light source that illuminates the subject existing near the center of the field of view cannot be accurately determined due to the influence of the light source that exists in the periphery of the sensor field of view. The focus amount cannot be corrected.

  An object of the present invention is to provide an imaging apparatus capable of avoiding a decrease in focus control accuracy due to the influence of a light source existing in a light source detection visual field.

  An imaging apparatus according to one aspect of the present invention detects light in a different wavelength region from focus detection means for detecting a focus state of a shooting optical system using light from the shooting optical system and light from the shooting optical system. First and second light receiving sensors, and control means capable of generating information used for focus control using the focus state detection results and signals from the first and second light receiving sensors. The control means changes a method for generating information used for focus control in accordance with the overlapping state of the visual fields of the first and second light receiving sensors.

  Note that an imaging system including the imaging device and a lens device that can be attached to and detached from the imaging device and has a photographing optical system also constitutes another aspect of the present invention.

  According to another aspect of the present invention, there is provided a method for controlling an imaging apparatus, the step of detecting a focus state of a photographing optical system using light from the photographing optical system, and photographing using first and second light receiving sensors. Information used for focus control can be generated using the step of detecting light in different wavelength regions from the light from the optical system, the detection result of the focus state, and the signals from the first and second light receiving sensors. An information generation step. In the information generation step, the method for generating information used for focus control is changed according to the overlapping state of the visual fields of the first and second light receiving sensors.

  According to the present invention, it is possible to generate information used for focus control by an appropriate method according to the overlapping state (in other words, a shift state) of the visual fields of the first and second light receiving sensors. For this reason, even when a strong light source is included in one of the shifted fields of view, a decrease in focus control accuracy due to the influence of the light source can be avoided. Thereby, an imaging device and an imaging system having good focusing performance can be realized.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a single-lens reflex camera system (imaging system) that is Embodiment 1 of the present invention. The camera system includes a single-lens reflex camera (imaging device) 1 and an interchangeable lens (lens device) 11 that is detachably attached to the camera 1.

  In the figure, an optical component, a mechanical component, an electric circuit, an image sensor (or film), and the like are accommodated in the camera 1 and an image (or photograph) can be taken.

  Reference numeral 2 denotes a main mirror, which is disposed obliquely in the photographing optical path in the viewfinder observation state and retracts out of the photographing optical path in the photographing state. Further, the main mirror 2 is a half mirror, and when arranged in the photographing optical path, transmits about half of the light beam from the subject to a focus detection optical system described later.

  Reference numeral 3 denotes a focusing plate, which constitutes a part of the finder optical system and is disposed on a planned imaging plane of a photographing optical system described later. Reference numeral 4 denotes a finder optical path changing pentaprism. Reference numeral 5 denotes an eyepiece, and the photographer can observe the subject image by observing the focus plate 3 from this window.

  Reference numerals 6 and 7 denote a first imaging lens and a photometric sensor for measuring the subject luminance in the viewfinder observation screen. Reference numerals 30 and 31 denote a second imaging lens and a light source detection circuit for measuring the luminance of the subject in the viewfinder observation screen.

  Reference numeral 8 denotes a focal plane shutter. Reference numeral 9 denotes an image sensor, which is composed of a CCD sensor or a CMOS sensor. Reference numeral 25 denotes a sub-mirror, which is disposed obliquely in the photographing optical path together with the main mirror 2 in the finder observation state, and retracts out of the photographing optical path in the photographing state. The sub mirror 25 bends the light beam transmitted through the main mirror 2 arranged in the photographing optical path downward and guides it to a focus detection unit described later.

  The focus detection unit 200 includes a field mask 26, a field lens 27, a mirror 30, a stop 28, a secondary imaging lens 29, and a focus detection sensor 201. The mirror 30 and the secondary imaging lens 29 constitute a focus detection optical system, and the secondary imaging surface of the photographing optical system is formed on the focus detection sensor 201. The focus detection unit 200 detects the focus state (pixel information having a phase difference) of the photographing optical system by a so-called phase difference detection method, and sends the detection result to a camera microcomputer to be described later.

  A mount contact group 10 serves as a communication interface between the camera 1 and the interchangeable lens 11.

  Reference numerals 12 to 14 denote lens units. A first lens unit (hereinafter referred to as a focus lens) 12 performs focus adjustment by moving on the optical axis. The second lens unit 13 performs zooming by changing the focal length of the photographing optical system by moving on the optical axis.

  Reference numeral 14 denotes a fixed third lens unit. Reference numeral 15 denotes an aperture. A focus driving motor 16 moves the focus lens 12 in the optical axis direction during AF. Reference numeral 17 denotes an aperture drive motor for changing the aperture diameter of the aperture 15.

  A distance encoder 18 slides a brush 19 attached to the focus lens 12 to read the position of the focus lens 12 and generate a signal corresponding to the subject distance.

  Next, the electric circuit configuration of the camera system will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same component as FIG.

  First, the circuit configuration in the camera 1 will be described. The camera microcomputer 100 is connected with a focus detection sensor 201, a photometric sensor 7, a shutter control circuit 107, a motor control circuit 108, and a liquid crystal display circuit 111. The camera microcomputer 100 communicates with the lens microcomputer 112 arranged in the interchangeable lens 11 via the mount contact 10.

  The focus detection sensor 201 includes a pair or a plurality of pairs of AF line sensors (CCD line sensors) and a light source detection sensor.

  A camera microcomputer 100 as a control unit performs charge accumulation control and charge readout control of the AF line sensor. Then, pixel information from each AF line sensor (information representing two images formed on the pair of AF line sensors) is A / D converted to detect a phase difference between the pixel information. Further, a defocus amount of the photographing optical system, that is, information used for focus control is obtained based on the phase difference.

  Here, as will be described in detail later, the camera microcomputer 100 performs correction according to a defocus light source (hereinafter referred to as defocus light source correction) in accordance with a predetermined condition. Based on the defocus amount (the light source is not corrected or the light source is corrected), the focus sensitivity information of the photographing optical system, and the like, the drive amount of the focus lens 12 for focusing (focus) The drive amount of the drive motor 16) is calculated. The driving amount information of the focus lens 12 is transmitted to the lens microcomputer 112. The lens microcomputer 112 controls the focus drive motor 16 according to the received drive amount information. Thereby, AF control in the interchangeable lens 11 is performed, and focusing is obtained.

  Further, the light source detection sensor includes a visible light sensor and an infrared light sensor (first and second light receiving sensors) that detect light having different spectral sensitivities, that is, different wavelength regions.

  Here, in this embodiment, a visible light sensor mainly having sensitivity in the visible light wavelength region and an infrared light sensor mainly having sensitivity in the infrared light wavelength region are used. In the present invention, “detecting light in different wavelength regions” does not mean only when the wavelength regions to be detected (having sensitivity) are completely separated, but as shown in FIG. This includes the case where a part of each overlaps. Further, the sensitivity wavelength region of one sensor may be included in the sensitivity wavelength region of one sensor.

  The camera microcomputer 100 performs charge accumulation control and charge readout control of these visible light sensor and infrared light sensor. And the signal which shows the luminance information obtained by each sensor is A / D-converted, and the luminance ratio which is a ratio of the luminance information (luminance value) of visible light and infrared light is produced | generated as information regarding a light source.

  The shutter control circuit 107 performs energization control of the shutter front curtain drive magnet MG-1 and the shutter rear curtain drive magnet MG-2 constituting the focal plane shutter 8 in accordance with a signal from the camera microcomputer 100. As a result, the shutter front curtain and rear curtain travel, and the image sensor 9 is exposed.

  The motor control circuit 108 controls the mirror drive motor M in accordance with a signal from the camera microcomputer 100. Thereby, the up / down operation of the main mirror 2 and the charging operation of the focal plane shutter 8 are performed.

  SW1 is a switch that is turned on by a first stroke (half-press) operation of a release button (not shown) to start photometry and AF.

  SW2 is a switch that is turned on by a second stroke (full press) operation of the release button and starts shutter running, that is, an exposure operation. In addition to the switches SW1 and SW2, the camera microcomputer 100 reads the states of various switches such as an ISO sensitivity setting switch, an aperture setting switch, and a shutter speed setting switch which are not shown.

  The liquid crystal display circuit 111 controls the in-finder display 24 and the external display 42 according to signals from the camera microcomputer 100.

  Next, an electric circuit configuration in the interchangeable lens 11 will be described. As described above, the interchangeable lens 11 is electrically connected to the camera 1 via the mount contact 10. The mount contact 10 is a contact L0 that is a power contact for the focus drive motor 16 and the aperture drive motor 17 in the interchangeable lens 11, and a power contact L1 for the lens microcomputer 112, and a clock for serial data communication. Contact L2. Further, a data transmission contact L3 from the camera 1 to the interchangeable lens 11, a data transmission contact L4 from the interchangeable lens 11 to the camera 1, a motor ground contact L5 to the motor power supply, and a power supply for the lens microcomputer 112. And a ground contact L6.

  The lens microcomputer 112 is connected to the camera microcomputer 100 via the mount contact 10 and controls the focus drive motor 16 and the aperture drive motor 17 in accordance with signals from the camera microcomputer 100. Thereby, focus adjustment and light quantity adjustment are performed.

  Reference numerals 50 and 51 denote a photodetector and a pulse plate. The pulse plate 51 is rotated by the focus drive motor 16. When the pulse plate 51 rotates, the photodetector 50 receives detection light intermittently and outputs a pulse signal. The lens microcomputer 112 obtains position information of the focus lens 12 at the time of focus adjustment by counting the number of pulses from the photodetector 50. The lens microcomputer 112 controls the focus drive motor 16 so that the position information of the focus lens 12 matches the drive amount for focusing the focus lens 12 transmitted from the camera microcomputer 100. Thereby, focus adjustment is performed.

  Reference numeral 18 denotes the above-described distance encoder, and the position information of the focus lens 12 read here is input to the lens microcomputer 112. The lens microcomputer 112 converts the position information into subject distance information and transmits it to the camera microcomputer 100.

  The focus detection sensor 201 will be described in detail with reference to FIGS. FIG. 3 is a diagram showing a detailed configuration of an optical system related to focus detection. The light beam from the subject that has passed through the photographing optical system is reflected by the sub-mirror 25 shown in FIG. 1, and once forms an image in the vicinity of the field mask 26 arranged on a plane conjugate with the imaging surface. In FIG. 3, the optical path reflected by the sub-mirror 25 and then turned back by the plurality of mirrors 30 is developed. The field mask 26 is a member for shielding extra light other than the focus detection area in the screen.

  The field lens 27 has an action of forming images of two pairs of openings formed in the stop 28 in the vicinity of the exit pupil of the photographing optical system. A secondary imaging lens 29 is disposed behind the stop 28. The secondary imaging lens 29 includes two pairs of lenses, and each lens corresponds to each opening of the diaphragm 28. The light flux that has passed through the field mask 26, the field lens 27, the aperture 28, and the secondary imaging lens 29 forms an image on the AF line sensor and the light source detection sensor on the focus detection sensor 201.

  FIG. 4 shows the arrangement of AF line sensors and light source detection sensors in the focus detection sensor 201. The focus detection sensor 201 includes four (two pairs) AF line sensors 211a, 211b, 212a, and 212b, and four (two pairs) light source detection sensors 213a, 213b, 214a, and 214b. The light source detection sensors 213a and 214a are visible light sensors as first light receiving sensors, and the light source detection sensors 213b and 214b are infrared light sensors as second light receiving sensors.

  FIG. 5 shows a positional relationship between a focus detection area corresponding to the visual field of the AF line sensor and a light source detection area corresponding to the visual field of the light source detection sensor in the photographing screen. The vertical visual field 51 which is a focus detection area is an area where a light beam from here is guided to the pair of AF line sensors 211a and 211b. That is, the light flux from the subject existing in the vertical visual field 51 forms two images on the pair of AF line sensors 211a and 211b, and the signal (image signal) corresponding to the two images from the AF line sensors 211a and 211b. The focus detection of the photographing optical system is performed based on the phase difference. The horizontal visual field 52 is an area where the light flux from here is guided to the pair of AF line sensors 212a and 212b. That is, the light flux from the subject existing in the horizontal visual field 52 forms two images on the pair of AF line sensors 212a and 212b, and the signal (image signal) corresponding to the two images from the AF line sensors 212a and 212b. The focus detection of the photographing optical system is performed based on the phase difference.

  Further, the upper visual field 53 that is a light source detection region is a region where light beams from here are guided to the visible light sensor 213a and the infrared light sensor 213b that make a pair with each other. The signals from the visible light sensor 213a and the infrared light sensor 213b are respectively the luminance values (luminance values) of the light component in the visible wavelength region and the light component in the infrared wavelength region of the light flux from the subject and the light source present in the upper visual field 53. Information). The light source that illuminates the subject existing in the upper visual field 53 can be detected (estimated) by the luminance ratio that is the ratio of the luminance values.

  Further, the lower visual field 54 which is a light source detection region is a region where light beams from here are guided to the visible light sensor 214a and the infrared light sensor 214b which make a pair with each other. The signals from the visible light sensor 214a and the infrared light sensor 214b are respectively the luminance values (luminance values) of the light component in the visible wavelength region and the light component in the infrared wavelength region of the light flux from the subject and the light source present in the lower visual field 54. Information). The light source that illuminates the subject existing in the lower visual field 54 can be detected (estimated) by the luminance ratio that is the ratio of the luminance values.

  As described above, in this embodiment, the focus detection sensor 201 is provided with two pairs of AF line sensors in the vertical and horizontal directions, so that the object having the contrast in the vertical direction and the object having the contrast in the horizontal direction can be used. Focus detection is possible. In addition, by arranging the light source detection region (field of the light source detection sensor) so as to be close to or overlap at least part of the focus detection region (field of view of the AF line sensor), the subject for which focus detection is performed or the vicinity thereof Detection of the illuminating light source is possible.

  Next, the spectral sensitivity characteristics of the visible light sensors 213a and 214a and the infrared light sensors 213b and 314b will be described with reference to FIG. In the figure, A indicates the spectral sensitivity characteristics of the visible light sensors 213a and 214a. The horizontal axis represents wavelength (nm) and the vertical axis represents sensitivity. B represents the spectral sensitivity characteristics of the infrared light sensors 213b and 314b. In the characteristics A and B, wavelength regions having sensitivity in the vicinity of 600 to 750 nm overlap, but the wavelength regions where the sensitivity reaches a peak are a visible light region and a near infrared light region, respectively. Accordingly, the visible light sensors 213a and 214a mainly detect light in the visible light region, and the infrared light sensors 213b and 314b mainly detect light in the near infrared light region on the longer wavelength side than the visible light region. .

  Next, the AF operation in the camera system of the present embodiment will be described using the flowchart of FIG. This AF operation is mainly executed by the camera microcomputer 100 as control means in accordance with a computer program.

  When SW1 of the camera 1 shown in FIG. 2 is turned on, the operation starts from step (abbreviated as “s” in FIG. 2) 101. The camera microcomputer 100 accumulates charges in the AF line sensor in the focus detection unit 200 and generates pixel information corresponding to the focus state of the photographing optical system.

  In step 102, the camera microcomputer 100 calculates the defocus amount of the photographing optical system based on the acquired pixel information shift (phase difference).

  In step 103, the camera microcomputer 100 performs charge accumulation of the light source detection sensor and reading of the accumulated charge (luminance signal). In step 104, a luminance ratio (infrared light / visible light), which is an output ratio of luminance signals from the light source detection sensors (infrared light sensor and visible light sensor), is calculated. In this embodiment, the luminance ratios detected in the upper visual field 53 and the lower visual field 54 are averaged.

  In step 105, the camera microcomputer 100 reads a first correction coefficient (correction information) that is a defocus correction coefficient from the data table shown in FIG. 9 according to the averaged luminance ratio.

  The data table in FIG. 9 is stored in a memory (ROM table) 100a in the camera microcomputer 100. The horizontal axis represents the luminance ratio, and the vertical axis represents the first correction coefficient. In this embodiment, the case where the first correction coefficient corresponding to the luminance ratio is stored in the data table format will be described. However, a calculation formula for calculating the first correction coefficient according to the luminance ratio is stored as correction information. You may keep it.

  In the next step 106, the camera microcomputer 100 requests the lens microcomputer 112 to transmit chromatic aberration amount data specific to the interchangeable lens (imaging optical system). This request is transmitted to the lens microcomputer 112 via the serial communication lines LCK, LDO, and LDI shown in FIG.

  Upon receiving the request, the lens microcomputer 112 first analyzes the content of the request (communication). If the request is a transmission request for chromatic aberration amount data, chromatic aberration amount data corresponding to the current focal length and focus lens position of the photographing optical system is read from the memory (ROM table) 112a in the lens microcomputer 112. The chromatic aberration amount data is measured in advance in association with the focal length and the focus lens position for each individual interchangeable lens, and is stored in the memory 112a. The lens microcomputer 112 returns the chromatic aberration amount data to the camera microcomputer 100 via the serial communication lines LCK, LDO, and LDI.

  In the next step 107, the camera microcomputer 100 calculates a defocus correction amount by multiplying the chromatic aberration data acquired in step 106 by the first correction coefficient obtained in step 105.

  In step 108, the camera microcomputer 100 determines whether or not the defocus amount (focus state detection result) calculated in step 102 is within a range of ± d2 shown in FIG. If it is within the range of ± d2 (first state), it is regarded that the reliability of the result detected by the light source detection sensor is high, the process proceeds to the next step 109, and the light source correction of the defocus amount is performed. On the other hand, if the defocus amount is outside the range of ± d2 (second state), the reliability of the result detected by the light source detection sensor is regarded as low, and the light source correction of the defocus amount is not performed, and step 110 is performed. Transition.

  Here, a method of determining the defocus amount d2, which is a reference for determining the reliability of the result detected by the light source detection sensor, will be described with reference to FIGS.

  FIG. 8 is a data table stored in the memory (ROM table) 100a in the camera microcomputer 100. The horizontal axis represents the defocus amount, and the vertical axis represents the ratio (overlapping state or overlapping degree) of the overlapping amount of the visual field of the light source detection sensor (infrared light sensor and visible light sensor).

  As shown in FIG. 7, the area of the visual field VSF of the visible light sensor and the visual field ISF of the infrared light sensor are both “S”, and the area of the portion where these visual fields overlap is “S ′”.

  As shown in FIG. 8, when the defocus amount is 0 (in a focused state), the overlap amount ratio S ′ / S is 1, and as the defocus amount increases, S ′ / S decreases linearly. To do. And the one where the ratio of the overlapping amount of the visual field VSF of the visible light sensor and the visual field ISF of the infrared light sensor is close to 1 is less affected by the light source existing only in the visual field of one sensor.

  In this embodiment, whether or not S ′ / S ≧ 0.8 is used as a criterion for determining the reliability of the detection result by the light source detection sensor. For this reason, the reliability of the detection result by the light source detection sensor is high when the defocus amount is within ± d2 corresponding to S ′ / S = 0.8. As for the relationship between the defocus amount and S ′ / S, a design value or an actual measurement value is stored in the ROM table.

  Note that the above reliability determination criteria are common to both the visible light sensor 213a and the infrared light sensor 213b and the visible light sensor 214a and the infrared light sensor 214b shown in FIG. Moreover, the above criteria are only examples, and the present invention is not limited thereto.

  In FIG. 13, in step 109, the camera microcomputer 100 calculates the final defocus amount by adding the defocus correction amount calculated in step 107 to the defocus amount obtained in step 102. This is hereinafter referred to as a light source corrected defocus amount.

  In step 110, the camera microcomputer 100 determines that the defocus amount (defocus amount that has not undergone light source correction or defocus amount that has undergone light source correction) calculated in step 102 or step 109 is within a predetermined focus range. It is determined whether or not. If it is within the focusing range, the routine proceeds to step 112.

  If it is out of focus range, the process proceeds to step 111, and the defocus amount is transmitted to the lens microcomputer 112 via the serial communication lines LCK, LDO, and LDI described above. The lens microcomputer 112 determines the drive direction and drive amount of the focus drive motor 16 according to the information on the defocus amount, and drives the focus drive motor 16. And it returns to step 101 and repeats the process of steps 101-111 until an in-focus state is acquired.

  In step 112, the camera microcomputer 100 determines whether or not the switch SW2 is turned on. If it is turned on, the process proceeds to step 201 shown in FIG. If the switch SW2 is off, the AF operation process ends.

  Next, an imaging operation will be described with reference to FIG. When the above-described AF operation is completed and the switch SW2 is turned on, the camera microcomputer 100 measures subject luminance through the photometric sensor 7 in step 201. Further, the subject brightness BV is obtained from the photometric value obtained by the photometric sensor 7 and added to the set ISO sensitivity SV to obtain the exposure value EV, and the aperture value AV and the shutter speed TV are calculated by a predetermined algorithm.

  In step 202, the camera microcomputer 100 moves the main mirror 2 up and retracts it from the photographing optical path. At the same time, the aperture value AV information determined in step 202 is transmitted to the lens microcomputer 112. The lens microcomputer 112 narrows down the aperture 15 according to the aperture value information.

  When the main mirror 2 is completely retracted from the photographing optical path, in step 203, the camera microcomputer 100 energizes the shutter front curtain drive magnet MG-1, and starts the opening operation of the focal plane shutter 8.

  When a predetermined shutter opening time elapses, the process proceeds to step 204, where the camera microcomputer 100 energizes the shutter rear curtain drive magnet MG-2 and closes the rear curtain of the focal plane shutter 8. Thereby, the exposure of the image sensor 9 is completed.

  In step 205, the camera microcomputer 100 moves the main mirror 2 down. Thus, the imaging operation is completed.

  As described above, in the camera of the present embodiment, the defocus amount detected by the AF line sensor having a visual field that is close to or at least partially overlaps the visual field of the light source detection sensor, the visible light sensor, and the infrared light sensor. The relationship with the amount of visual field deviation is stored. Therefore, it is possible to determine (estimate) the amount of visual field shift between the visible light sensor and the infrared light sensor from the defocus amount. Then, when the visual field shift amount, that is, the defocus amount is larger than a specific value, the reliability of the light source detection result is low, so the light source correction of the defocus amount is not performed. . Thereby, it can suppress that the light source which exists in one visual field among a visible light sensor and an infrared-light sensor has a bad influence on the precision of focus control. On the other hand, when the visual field shift amount of the visible light sensor and the infrared light sensor, that is, the defocus amount is smaller than a specific value, the light source detection result is highly reliable, and thus the light source correction of the defocus amount is performed. Accordingly, it is possible to perform focus control with high accuracy according to the type of light source that illuminates the subject.

  FIG. 15 is a flowchart of the AF operation in the camera system that is Embodiment 2 of the present invention. The configuration of the camera system of the present embodiment is the same as that of the camera system of the first embodiment. For this reason, in this embodiment, the same reference numerals as those in the first embodiment are assigned to the components common to the first embodiment.

  In FIG. 15, when the switch SW <b> 1 of the camera 1 is turned on, the camera microcomputer 100 starts operation from step 301. Here, the camera microcomputer 100 causes the AF line sensor in the focus detection unit 200 to perform charge accumulation, and generates pixel information corresponding to the focus state of the photographing optical system.

  In step 302, the camera microcomputer 100 calculates the defocus amount of the photographing optical system based on the acquired pixel information shift (phase difference).

  In step 303, it is determined whether or not the defocus amount calculated in step 302 is within the range of ± d2 described in the first embodiment with reference to FIG. When it is within the range of ± d2, it is considered that the reliability of the detection result by the light source detection sensor is high, and the process proceeds to the next step 304. On the other hand, when it is out of the range of ± d2, it is considered that the reliability of the detection result by the light source detection sensor is low, and the process proceeds to step 310.

  In step 304, the camera microcomputer 100 performs charge accumulation of the light source detection sensor and reading of the accumulated charge (luminance signal). In step 305, a luminance ratio (infrared light / visible light), which is an output ratio of luminance signals from the light source detection sensors (infrared light sensor and visible light sensor), is calculated. In this embodiment, the luminance ratios detected in the upper visual field 53 and the lower visual field 54 are averaged.

  In step 306, the camera microcomputer 100 reads a first correction coefficient (correction information), which is a defocus correction coefficient, from the data table shown in FIG. 9 according to the averaged luminance ratio.

  In step 307, the camera microcomputer 100 requests the lens microcomputer 112 to transmit chromatic aberration amount data specific to the interchangeable lens (imaging optical system). This request is transmitted to the lens microcomputer 112 via the serial communication lines LCK, LDO, and LDI shown in FIG.

  Upon receiving the request, the lens microcomputer 112 first analyzes the content of the request (communication). If the request is a transmission request for chromatic aberration amount data, chromatic aberration amount data corresponding to the current focal length and focus lens position of the photographing optical system is read from the memory (ROM table) 112a in the lens microcomputer 112. The lens microcomputer 112 returns the chromatic aberration amount data to the camera microcomputer 100 via the serial communication lines LCK, LDO, and LDI.

  In step 308, the camera microcomputer 100 calculates the defocus correction amount by multiplying the chromatic aberration data acquired in step 307 by the first correction coefficient obtained in step 306.

  In step 309, the camera microcomputer 100 adds the defocus correction amount calculated in step 308 to the defocus amount calculated in step 302 to obtain a final defocus amount (light source corrected defocus amount). .

  In step 310, the camera microcomputer 100 determines that the defocus amount (defocus amount that has not been subjected to light source correction or defocus amount that has undergone light source correction) calculated in step 302 or step 309 is within a predetermined focusing range. It is determined whether or not. If it is within the focusing range, the process proceeds to step 312.

  If it is out of focus range, the process proceeds to step 311 and the defocus amount is transmitted to the lens microcomputer 112 via the serial communication lines LCK, LDO and LDI described above. The lens microcomputer 112 determines the drive direction and drive amount of the focus drive motor 16 according to the information on the defocus amount, and drives the focus drive motor 16. And it returns to step 301 and repeats the process of steps 301-311 until an in-focus state is acquired.

  In step 312, the camera microcomputer 100 determines whether or not the switch SW2 is turned on. If it is turned on, the process proceeds to step 201 shown in FIG. If the switch SW2 is off, the AF operation process ends.

  In the present embodiment described above, the same effects as those of the first embodiment can be obtained. Further, in this embodiment, since it is determined whether or not the light source correction is performed before performing the process for correcting the light source of the defocus amount, the AF process when the light source correction is not performed can be performed at high speed. .

  FIG. 16 is a flowchart of the AF operation in the camera system that is Embodiment 3 of the present invention. The configuration of the camera system of the present embodiment is the same as that of the camera system of the first embodiment. For this reason, in this embodiment, the same reference numerals as those in the first embodiment are assigned to the components common to the first embodiment.

  In FIG. 16, when the switch SW <b> 1 of the camera 1 is turned on, the camera microcomputer 100 starts operation from step 401. Here, the camera microcomputer 100 causes the AF line sensor in the focus detection unit 200 to perform charge accumulation, and generates pixel information corresponding to the focus state of the photographing optical system.

  In step 402, the camera microcomputer 100 calculates the defocus amount of the photographing optical system based on the acquired pixel information shift (phase difference).

  In step 403, it is determined whether or not the defocus amount calculated in step 302 is within the range of ± d2 described in the first embodiment with reference to FIG. If it is within the range of ± d2, it is considered that the reliability of the detection result by the light source detection sensor is high, and the process proceeds to the next step 404. On the other hand, when it is outside the range of ± d2, it is considered that the reliability of the detection result by the light source detection sensor is low, and the process proceeds to step 411.

  In step 404, the camera microcomputer 100 reads out a second correction coefficient that is a weighting coefficient of the defocus correction amount from the data table shown in FIG. 12 according to the defocus amount calculated in step 402.

  The data table in FIG. 12 is stored in a memory (ROM table) 102a in the camera microcomputer 100. The horizontal axis indicates the defocus amount, and the vertical axis indicates the second correction coefficient. In FIG. 12, 1 is set as the second correction coefficient for a range of −d2 to + d2 where the reliability of the light source detection result is sufficiently high. Further, between -d2 and -d1 and between + d2 and + d1, the second correction coefficient is set to gradually decrease from 1 as the defocus amount increases. Further, the second correction coefficient is set to 0 in a range exceeding −d1 and + d1.

  The range of −d2 to + d2 is a defocus amount range in which S ′ / S shown in FIG. ± d1 is a defocus amount at which S ′ / S becomes 0.5. However, the data table of FIG. 12 is only an example, and the present invention is not limited to this.

  In this embodiment, a case where the second correction coefficient corresponding to the defocus amount (field-of-view shift amount) is stored in the data table format will be described. However, in order to calculate the second correction coefficient according to the defocus amount. May be stored.

  In step 405, the camera microcomputer 100 performs charge accumulation of the light source detection sensor and reading of the accumulated charge (luminance signal). In step 406, a luminance ratio (infrared light / visible light), which is an output ratio of luminance signals from the light source detection sensors (infrared light sensor and visible light sensor), is calculated. In this embodiment, the luminance ratios detected in the upper visual field 53 and the lower visual field 54 are averaged.

  In step 407, the camera microcomputer 100 reads out a first correction coefficient (correction information) that is a defocus correction coefficient from the data table shown in FIG. 9 according to the averaged luminance ratio.

  In step 408, the camera microcomputer 100 requests the lens microcomputer 112 to transmit chromatic aberration amount data specific to the interchangeable lens (imaging optical system). This request is transmitted to the lens microcomputer 112 via the serial communication lines LCK, LDO, and LDI shown in FIG.

  Upon receiving the request, the lens microcomputer 112 first analyzes the content of the request (communication). If the request is a transmission request for chromatic aberration amount data, chromatic aberration amount data corresponding to the current focal length and focus lens position of the photographing optical system is read from the memory (ROM table) 112a in the lens microcomputer 112. The lens microcomputer 112 returns the chromatic aberration amount data to the camera microcomputer 100 via the serial communication lines LCK, LDO, and LDI.

  In step 409, the camera microcomputer 100 calculates a defocus correction amount by multiplying the chromatic aberration data acquired in step 408 by the first correction coefficient obtained in step 406. Further, the defocus correction amount is multiplied by the second correction coefficient obtained in step 404 and weighted according to the defocus amount (that is, the visual field shift amount between the visible light sensor and the infrared light sensor). A defocus correction amount is calculated.

  In step 410, the camera microcomputer 100 adds the weighted defocus correction amount obtained in step 409 to the defocus amount obtained in step 402 to obtain the final defocus amount (light source corrected defocus amount). ) Is calculated.

  In step 411, the camera microcomputer 100 determines that the defocus amount (defocus amount that has not been subjected to light source correction or defocus amount that has undergone light source correction) calculated in step 302 or step 309 is within a predetermined focusing range. It is determined whether or not. If it is within the focusing range, the process proceeds to step 413.

  If it is out of focus range, the process proceeds to step 412 and the defocus amount is transmitted to the lens microcomputer 112 via the serial communication lines LCK, LDO and LDI described above. The lens microcomputer 112 determines the drive direction and drive amount of the focus drive motor 16 according to the information on the defocus amount, and drives the focus drive motor 16. And it returns to step 301 and repeats the process of steps 401-412 until an in-focus state is acquired.

  In step 413, the camera microcomputer 100 determines whether or not the switch SW2 is turned on. If it is turned on, the process proceeds to step 201 shown in FIG. If the switch SW2 is off, the AF operation process ends.

  In the present embodiment described above, the same effects as those of the first and second embodiments can be obtained. In addition, in this embodiment, the weighting of the defocus correction amount is changed according to the defocus amount, that is, the visual field shift amount of the visible light sensor and the infrared light sensor. For this reason, even when there is little deviation | shift amount of both visual fields, the bad influence to the focus control precision by the light source which exists in one visual field can be suppressed. Therefore, it is possible to perform focus control with higher accuracy than in the first and second embodiments.

  In the above embodiment, the case where the defocus amount as the focus detection result is corrected has been described. However, the present invention is not limited to this. For example, the focus lens drive amount calculated based on the defocus amount can be corrected. The correction target in the present invention may be any information as long as it is information used for focus control such as a defocus amount and a focus lens drive amount.

  In the above embodiments, a single-lens reflex camera has been described. However, the present invention can also be applied to a lens exchange type video camera that performs phase difference detection AF.

Sectional drawing which shows schematic structure of the camera system which is Examples 1-3 of this invention. FIG. 3 is a block diagram showing an electrical configuration of camera systems of Examples 1 to 3. The perspective view which shows the structure of the focus detection sensor mounted in the camera of Examples 1-3. The figure which shows arrangement | positioning of the AF line sensor and light source detection sensor in the said focus detection sensor. The figure which shows the positional relationship of the focus detection area and light source detection area in the imaging | photography screen in the camera of Examples 1-3. The figure which shows the spectral sensitivity characteristic of the light source detection sensor (visible light sensor and infrared light sensor) in Examples 1-3. The figure which shows the overlapping state of the visual field of the said visible light sensor and an infrared light sensor. The figure which shows the relationship between the defocus amount in the camera of Examples 1-3, and the overlap amount (ratio) of the visual field of a light source detection sensor. The figure which shows the 1st correction coefficient according to the luminance ratio detected by the light source detection sensor in the camera of Examples 1-3. The figure which showed the spectral sensitivity of various light sources, an image pick-up element, and auxiliary light, and the relative focus position by the chromatic aberration of a lens. The figure which shows the state with almost no deviation | shift of the visual field of a visible light sensor and an infrared light sensor. The figure for demonstrating the malfunction by the shift | offset | difference of the visual field of a visible light sensor and an infrared light sensor. FIG. 10 is a diagram illustrating a second correction coefficient according to the defocus amount in the third embodiment. 6 is a flowchart illustrating an AF operation in the camera system according to the first exemplary embodiment. 5 is a flowchart illustrating an imaging operation in the camera system according to the first embodiment. 9 is a flowchart illustrating an AF operation in the camera system according to the second embodiment. 10 is a flowchart illustrating an AF operation in the camera system according to the third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Camera 11 Interchangeable lens 12 Focus lens 51, 52 Field of view 53, 54 (Field of light source detection sensor) Field of view 100 Camera microcomputer 112 Lens microcomputer 201 Focus detection sensor 211a, 211b, 212a, 212b AF line sensor 213a, 214a Visible light sensor 213b, 214b Infrared light sensor

Claims (9)

Focus detection means for detecting the focus state of the photographic optical system using light from the photographic optical system;
First and second light receiving sensors for detecting light in different wavelength regions among the light from the photographing optical system;
Control means capable of generating information used for focus control using the detection result of the focus state and the signals from the first and second light receiving sensors;
The image pickup apparatus, wherein the control unit changes a method of generating information used for the focus control in accordance with an overlapping state of visual fields of the first and second light receiving sensors.   The imaging apparatus according to claim 1, wherein the control unit uses the detection result of the focus state as information corresponding to the overlapping state of the visual fields.   The imaging apparatus according to claim 1, wherein the visual field of the first and second light receiving sensors is close to or at least partially overlaps the visual field of the focus detection unit. The control means stores correction information according to the overlapping state of the visual fields of the first and second light receiving sensors,
When the overlapping state of the visual field is the first state, the control unit generates information used for the focus control using the detection result of the focus state and the correction information, and the overlapping state of the visual field is The information used for the focus control is generated using the detection result of the focus state without using the correction information when the second state has a lower degree of overlap than the first state. The imaging device according to any one of 1 to 3. The control means stores correction information according to signals from the first and second light receiving sensors,
The control means generates information used for the focus control using the focus state detection result and the correction information, and changes the weight of the correction information according to the overlapping state of the visual field. The imaging device according to any one of claims 1 to 3.   The said control means produces | generates the information used for the said focus control using the detection result of the said focus state, the information regarding the chromatic aberration amount of the said imaging optical system, and the said correction information. Imaging device. The imaging device according to any one of claims 1 to 6,
An imaging system comprising: a lens device that is detachable from the imaging device and has the imaging optical system.   The image pickup system according to claim 7, wherein the lens device includes a storage unit that stores information relating to a chromatic aberration amount of the photographing optical system. Detecting the focus state of the photographing optical system using light from the photographing optical system;
Detecting light in different wavelength regions from the light from the imaging optical system using the first and second light receiving sensors;
An information generation step capable of generating information used for focus control using the detection result of the focus state and the signals from the first and second light receiving sensors;
A method for controlling an imaging apparatus, wherein, in the information generation step, a method for generating information used for the focus control is changed according to an overlapping state of visual fields of the first and second light receiving sensors.