JP2008203407A - Imaging apparatus, lens device and imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus that performs TTL (Through The Lens) phase difference detection system AF using a plurality of focus detection sensors having different base line lengths, the apparatus being designed so as to exert highly accurate focus control regardless of the types of a lens device and light source and the lengths of the base lines of the focus detection sensors. <P>SOLUTION: The imaging apparatus 1 having a detachable lens device 11 includes: the plurality of focus detection sensors 29a and 29d having different base line lengths and detecting a corresponding phase difference between two images formed by a luminous flux from the attached lens device; and a wavelength component detection sensor 32 that detects the wavelength component included in a luminous flux from a subject. The control means 100 acquires information about a chromatic aberration corresponding to the base line length of a specific focus detection sensor selected from the plurality of focus detection sensors and used for focus detection. Information used for the focus control is generated based on a phase difference obtained from the specific focus detection sensor, information about the obtained chromatic aberration, and the detection result obtained by the wavelength component detection sensor. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging apparatus that performs an autofocus (AF) operation, and more particularly to an imaging apparatus that can perform an AF operation according to the type of light source that illuminates a subject.

  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 the TTL phase difference detection method, light incident from an imaging lens is divided into two light beams by a light splitting member such as a mirror, and formed on a pair of line sensors by a pair of imaging lenses. The defocus amount is calculated from the shift (phase difference) between the two images at. Then, focusing is performed by controlling the focus lens in accordance with the defocus amount.

  In an imaging apparatus that employs such a TTL phase difference detection AF, the following problems arise because the imaging system and the focus detection system are different.

  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. 13 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 same figure, C is the chromatic aberration of the imaging lens, and B, G, and R are the spectral sensitivities of the blue, green, and red pixels 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.

  As described above, Patent Documents 1 and 2 disclose cameras that correct the focus position 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 sensors having different spectral sensitivities is 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.

Furthermore, in Patent Document 3, in order to achieve both improvement in focus detection accuracy and detection of a large defocus amount, a phase difference is obtained using light beams that pass through different pupils in the lens and have different base-length intervals. An AF camera for detection is disclosed.
Japanese Patent Publication No. 1-45883 (page 13, upper right column, line 13 to page 4, lower left column, line 7) JP 2000-275512 A (paragraphs 0041 to 0107, FIGS. 3 to 10 and the like) JP-A-5-127073 (paragraphs 0033-0048, FIGS. 7-18, etc.)

  In the AF camera disclosed in Patent Document 3, a light beam used for phase difference detection passes through different pupils in the lens, and a pair of imaging lenses for forming an image on the line sensor is provided for each base line length. ing. For this reason, a slight difference occurs in the detection result of the defocus amount detected for each focus detection sensor having a different baseline length.

  The present invention is an imaging apparatus that performs TTL phase difference detection AF using a plurality of focus detection sensors having different baseline lengths, regardless of the type of lens device, light source, subject color, and baseline length of the focus detection sensor. In addition, the present invention provides an imaging apparatus that can perform high-precision focus control. In addition, a lens device mounted on the imaging device is provided. Furthermore, the imaging system comprised by these imaging devices and lens apparatuses is provided.

An image pickup apparatus according to an aspect of the present invention is an image pickup apparatus in which a lens apparatus can be attached and detached, and has two different base line lengths, and the positions of two images formed by light beams from the lens apparatus attached to the image pickup apparatus. A plurality of focus detection sensors for detecting a phase difference; a wavelength component detection sensor for detecting a wavelength component included in a light beam from a subject; and a control means for generating information used for focus control of the lens apparatus. Then, the control unit acquires information on chromatic aberration according to the baseline length of the specific focus detection sensor used for focus detection among the plurality of focus detection sensors, and obtains the phase difference obtained by the specific focus detection sensor and the acquired chromatic aberration. Information used for focus control is generated on the basis of the information on the detection result and the detection result of the wavelength component detection sensor.
According to another aspect of the present invention, there is provided a lens apparatus including an imaging apparatus having a plurality of focus detection sensors each having a different baseline length and detecting a phase difference between two images formed by light beams from the lens apparatus. It is a detachable lens device. The lens device is responsive to a base length of a specific focus detection sensor used for focus detection among a plurality of focus detection sensors in accordance with a storage unit that stores information relating to chromatic aberration of the lens device and a transmission command from the imaging device. And control means for transmitting information relating to the chromatic aberration to the image pickup apparatus.

  According to another aspect of the present invention, there is provided a control method that is an imaging apparatus in which a lens apparatus can be attached and detached, and has different baseline lengths, and is formed by light beams from a lens apparatus attached to the imaging apparatus. The present invention is applied to an imaging apparatus having a focus detection sensor that detects a phase difference between two images and a wavelength component detection sensor that detects a wavelength component included in a light beam from a subject. The control method includes a step of acquiring a detection result by the wavelength component detection sensor, a chromatic aberration acquisition step of acquiring information relating to chromatic aberration of the lens device, and a control information generation step of generating information used for focus control of the lens device. . Then, in the chromatic aberration acquisition step, information on chromatic aberration according to the baseline length of the specific focus detection sensor used for focus detection among the plurality of focus detection sensors is acquired, and in the control information generation step, the information obtained by the specific focus detection sensor Information used for focus control is generated based on the phase difference, information on chromatic aberration acquired in the chromatic aberration acquisition step, and a detection result by the wavelength component detection sensor.

  Further, according to another aspect of the present invention, there is provided a control method for an imaging apparatus having a plurality of focus detection sensors that detect different phase differences between two images having different baseline lengths and formed by a light beam from a lens apparatus. It is applied to a detachable lens device. The control method includes a step of reading out information relating to chromatic aberration of the lens device according to a base line length of a specific focus detection sensor used for focus detection among a plurality of focus detection sensors from a storage unit and a transmission command from an imaging device. And a step of transmitting the read information to the imaging apparatus.

  According to the present invention, a highly accurate TTL phase difference detection AF can be performed regardless of the type of lens device, the light source, the subject color, and the base length of the focus detection sensor.

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

  FIG. 1 shows an imaging system that is an embodiment of the present invention. The imaging system includes a single-lens reflex digital camera (hereinafter simply referred to as a camera) as an imaging device and an interchangeable lens (lens device) that is detachably attached to the camera.

  In the figure, reference numeral 1 denotes a camera, and an interchangeable lens 11 is mounted on the front surface thereof. In the camera 1, an image pickup device 9 including an optical component, a mechanical component, an electric circuit, and a CCD sensor or a CMOS sensor is housed.

  Reference numeral 2 denotes a main mirror, which is disposed obliquely in the imaging optical path in the viewfinder observation state and retracts out of the imaging optical path in the imaging state. Further, the main mirror 2 is a half mirror, and when it is disposed in the imaging optical path, it transmits about half of the light beam incident from the interchangeable lens 11. Reference numeral 20 denotes a sub mirror, which is disposed obliquely in the imaging optical path behind the main mirror 2 in the finder observation state, and retracts out of the imaging optical path in the imaging state. In the imaging state, the sub mirror 20 bends the light beam transmitted through the main mirror 2 downward and guides it to a focus detection unit described later.

  Reference numeral 3 denotes a focusing plate disposed on the planned imaging plane of the interchangeable lens 11, and reference numeral 4 denotes a pentaprism for bending the finder optical path. Reference numeral 5 denotes an eyepiece. A finder optical system is configured by the focus plate 3, the pentaprism 4, and the eyepiece lens 5, and the photographer can observe the subject image by observing the focus plate 3 through the eyepiece lens 5.

  Reference numeral 7 denotes a photometric sensor for measuring the luminance of the subject. Reference numeral 6 denotes an imaging lens for forming a subject image on the photometric sensor 7 by the light flux from the pentaprism 4.

  Reference numeral 32 denotes a color temperature sensor as a wavelength component detection sensor, which detects the luminance of the wavelength component contained in the light flux from the subject. Reference numeral 30 denotes an imaging lens that forms a subject image on the color temperature sensor 32 with the light flux from the pentaprism 4. Reference numeral 31 denotes an optical band-pass filter that cuts unnecessary short-wavelength and long-wavelength components of the light flux directed to the color temperature sensor 32.

  Reference numeral 8 denotes a focal plane shutter that controls the amount and timing of incidence of a light beam on the image sensor 9.

  A focus detection unit 24 includes a field lens 25, a secondary imaging lens unit 26, a field mask 27, an infrared cut filter 28, and a sensor unit 29.

  The field lens 25 and the secondary imaging lens unit 26 constitute a focus detection optical system, and form a secondary subject image on the sensor unit 29 in the light flux from the interchangeable lens 11. The focus detection unit 24 generates phase difference information corresponding to the focus state of the imaging optical system in the interchangeable lens 11. The phase difference information is sent to a camera microcomputer described later. The camera microcomputer obtains the defocus amount of the imaging optical system from the phase difference information, and further calculates the drive amount and drive direction of the focus lens 12 for obtaining the focus from the defocus amount. Thereby, focus control is performed by a so-called TTL phase difference detection method.

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

  In the interchangeable lens 11, lens units 12 to 14 and a diaphragm 15 constituting an imaging optical system are arranged. A first lens unit (hereinafter referred to as a focus lens) 12 closest to the subject adjusts the focus position by moving in the optical axis direction. The second lens unit 13 moves in the optical axis direction and performs zooming of the imaging optical system. Reference numeral 14 denotes a fixed third lens unit. The diaphragm 15 adjusts the amount of light by changing the aperture diameter.

  A focus drive motor 16 moves the focus lens 12 in the optical axis direction. Reference numeral 17 denotes an aperture drive motor for changing the aperture diameter of the aperture 15. Reference numeral 18 denotes a distance encoder, and a brush 19 attached to the focus lens 12 slides on the distance encoder 18 to output a signal corresponding to the position of the focus lens 12. The subject distance can be detected based on position information from the distance encoder 18 in a state where the focus lens 12 is controlled to the in-focus position. The interchangeable lens 11 is also provided with a zoom position detector (not shown) that detects the position of the second lens unit 13, and obtains the focal length of the imaging optical system based on a signal from the zoom position detector. You can also.

  The configuration of the focus detection unit 24 will be described with reference to FIGS. 2 to 4 show a secondary imaging lens unit 26, a field mask 27, and a line sensor provided for one focus detection area among a plurality of focus detection areas (AF frames) shown in FIG. 7 later. 29a-29d are shown. That is, the secondary imaging lens unit 26, the field mask 27, and the sensor unit 29 shown in FIGS. 2 to 4 are provided for each focus detection region.

  FIG. 2 shows the secondary imaging lens unit 26 as viewed from the light incident side of the focus detection unit 24. The secondary imaging lens unit 26 has four secondary imaging lenses 26a to 26d.

  FIG. 3 shows the field mask 27 as viewed from the light incident side. Reference numerals 27a to 27d denote stop holes, which respectively stop four light beams transmitted through the four secondary imaging lenses 26a to 26d.

  FIG. 4 shows the sensor unit 29 as viewed from the light incident side. The sensor unit 29 has four line sensors 29a to 29d as photoelectric conversion element (pixel) rows. The four light beams that have passed through the secondary imaging lenses 26a to 26d and passed through the field masks 27a to 27d form subject images on the line sensors 29a to 29d, respectively.

  The subject images (two images) formed on the line sensors 29a and 29b through the secondary imaging lenses 26a and 26b arranged in the vertical direction in the figure form a pair. Further, the subject images (two images) formed on the line sensors 29c and 29d through the secondary imaging lenses 26c and 26d arranged in the horizontal direction in the figure are paired with each other. The baseline length between the line sensors 29c and 29d is set longer than the baseline length between the line sensors 29a and 29b.

  The line sensor pair 29a, 29b and the line sensor pair 29c, 29d constitute a focus detection sensor. That is, the focus detection unit 24 of the present embodiment has two focus detection sensors. In this embodiment, a case where two focus detection sensors are provided will be described. However, as an embodiment of the present invention, the number of focus detection sensors may be three or more.

  FIG. 5 shows an exit pupil of the imaging optical system. 21 indicates the outer peripheral edge of the exit pupil, and 21W indicates the outer peripheral edge of the exit pupil corresponding to the light flux of F2.8. 21N indicates the outer peripheral edge of the exit pupil corresponding to the luminous flux of F5.6. 21a to 21d are aperture images of the field masks 27a to 27d projected onto the exit pupil, respectively.

  The pair of line sensors 29a and 29b receive (that is, observe) the light beams 21a and 21b forming F5.6 separated by the base line length d1 on the exit pupil. The pair of line sensors 29b and 29c receive (that is, observe) the light beams 21c and 21d forming F2.8 separated by the base line length d2 (> d1) on the exit pupil. Thereby, an output corresponding to the interval (shift) between the two subject images projected on the line sensor pair is obtained.

  When a bright interchangeable lens of F2.8 or higher is used, the output from the line sensor pair 29b, 29c of F2.8 having a base length longer than that of the line sensor pair 29a, 29b corresponding to F5.6 is used. Thereby, more accurate phase difference information (and thus defocus information) can be obtained.

  Next, the 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. A focus detection circuit 105 including the focus detection unit 24 described above, the photometric sensor 7, the color temperature sensor 32, and a shutter control circuit 107 are connected to the camera microcomputer 100 as control means. The camera microcomputer 100 is also connected with a motor control circuit 108 and a liquid crystal display circuit 111.

  The camera microcomputer 100 performs signal transmission via the lens microcomputer 112 disposed in the interchangeable lens 11 and the mount contact group 10. In the camera microcomputer 100, serial communication lines LCK, LDO, and LDI are formed through contacts L2, L3, and L4 described later in the mount contact group 10.

  The focus detection circuit 105 performs charge accumulation control of the line sensors 29 a to 29 d and readout control of the accumulated charge in accordance with a signal from the camera microcomputer 100. Then, phase difference information indicating the shift amount and shift direction of the subject image on the line sensor pair obtained from the pixel information from the line sensor pair is output to the camera microcomputer 100. The camera microcomputer 100 calculates the defocus amount of the imaging optical system based on the phase difference information, and calculates the drive amount and drive direction of the focus lens 12 based on the defocus amount.

  Information on the driving amount and driving direction is transmitted to the lens microcomputer 112, and the lens microcomputer 112 controls the focus control motor 16 to drive the focus lens 12. Thereby, focus control for obtaining in-focus is performed.

  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 front curtain and rear curtain of the shutter 8 travel and the exposure operation is performed.

  The motor control circuit 108 controls the motor M in accordance with a signal from the camera microcomputer 100 to perform up / down driving of the main mirror 2 and the sub mirror 20 and charge driving of the shutter 8.

  SW1 is a switch that is turned on by a first stroke (half-pressing) operation of a release button (not shown) to start photometry and focus control (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. The camera microcomputer 100 reads the states of the switches SW1 and SW2 and the states of switches such as an ISO sensitivity setting switch, an aperture setting switch, and a shutter speed setting switch (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. The camera 1 and the interchangeable lens 11 are electrically connected to each other via the mount contact group 10. The mount contact group 10 includes a contact L0 that is a power contact for the focus drive motor 16 and the aperture drive motor 17, a power contact L1 for the lens microcomputer 112, and a clock contact L2 for serial data communication. Including. The mount contact group 10 includes a data transmission contact L3 from the camera 1 to the interchangeable lens 11 and a data transmission contact L4 from the interchangeable lens 11 to the camera 1. Further, the mount contact group 10 includes a ground contact L5 for the motor power supply and a ground contact L6 for the lens microcomputer 112 power supply.

  The lens microcomputer 112 receives a signal from the camera microcomputer 100 via the mount contact group 10 and controls the focus drive motor 16 and the aperture drive motor 17 to perform focus control and aperture control.

  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 (drive amount 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.

  The position information of the focus lens 12 obtained by the distance encoder 18 described above is input to the lens microcomputer 112, where it is converted into subject distance information and transmitted to the camera microcomputer 100.

  The color temperature sensor 32, the optical bandpass filter 31, and the imaging lens 30 described in FIG. 1 will be described. FIG. 7 shows these viewed from the pentaprism 4 side. Reference numeral 33 denotes an AF frame formed on the focus plate 3, and indicates a focus detection area as an area where the phase difference information can be acquired by the focus detection unit 24.

  The color temperature sensor 32 includes a transmission part (non-colored part) A1 and a colored part B1. The imaging lens 30 has two lens portions, and the optical axes of the respective lens portions are arranged so as to pass through the centers of the transmission portion A1 and the coloring portion B1 of the color temperature sensor 32. For this reason, the transmissive part A1 and the colored part B1 receive light beams from the same region of the subject through the focus plate 3.

  Next, the spectral characteristics of the color temperature sensor 32 will be described with reference to FIG. a is the spectral sensitivity characteristic of the transmissive part A1 of the color temperature sensor 32, and b is the spectral sensitivity characteristic of the color filter applied before the colored part B1. c is the spectral sensitivity characteristic of the optical bandpass filter 31.

  The total spectral characteristic of the transmission part A1 is obtained by multiplying the spectral sensitivity characteristic a of the transmission part A1 by the spectral sensitivity characteristic c of the optical bandpass filter 31. The total spectral characteristic of the coloring part B1 is obtained by multiplying the spectral sensitivity characteristic a of the transmission part A1, the spectral sensitivity characteristic b of the color filter, and the spectral sensitivity characteristic c of the optical bandpass filter 31.

  Thereby, the transmission part A1 receives light of 400 to 700 nm, and the coloring part B1 receives light of 600 to 700 nm. The color temperature of the light source in the imaging range can be determined by comparing the outputs of two sensors (transmission part A1 and coloring part B1) having different spectral sensitivity characteristics. That is, the type of light source can be determined.

  Next, the operation of the camera system configured as described above will be described using the flowcharts of FIGS. This operation is executed by the camera microcomputer 100 according to a computer program stored therein.

  FIG. 9 shows the flow of AF operation in the camera system.

  When the switch SW1 is turned on by the first stroke operation of the release button, the camera microcomputer 100 starts the AF operation from step (abbreviated as S in the figure) 101. First, the camera microcomputer 100 selects an AF frame from a plurality of AF frames 33 automatically by a known algorithm or according to the operation of a selection switch by a photographer. Next, of the two line sensor pairs 29a, 29b and 29c, 29d corresponding to the selected AF frame, a pair of line sensors having a larger baseline length that can be used according to the open F value of the interchangeable lens 11 (specific focus). Detection sensor: hereinafter referred to as a specific line sensor pair). The line sensor pair that can be used in accordance with the open F value is a line sensor pair in which the opening image of the field mask 27 corresponding thereto falls within the outer peripheral edge of the exit pupil described earlier with reference to FIG.

  In the following description, the baseline length corresponding to a specific line sensor pair in the selected AF frame is referred to as a focus detection baseline length. The value of the focus detection baseline length may be the baseline length of the line sensor pair itself, or may be any of the baseline lengths d1 and d2 between the aperture images of the field mask 27 on the exit pupil shown in FIG.

  Then, the camera microcomputer 100 performs charge accumulation with the specific line sensor pair, and reads out phase difference information that is deviation information of the subject image formed on the line sensor pair. At this time, the diaphragm 15 is left open.

  In the next step 102, the camera microcomputer 100 calculates the defocus amount from the acquired phase difference information.

  In step 103, the camera microcomputer 100 reads the outputs from the transmission part A1 and the coloring part B1 of the color temperature sensor 32. In step 104, a difference between outputs from the transmission part A1 and the coloring part B1 is calculated, and a correction coefficient is read from the table data of FIG. 11 according to the difference. The table data of FIG. 11 is stored in a memory (ROM) 101a as a storage means in the camera microcomputer 100. The horizontal axis corresponds to the luminance difference between the transmissive portion A1 and the colored portion B1, and the vertical axis represents the luminance difference between the transmissive portion A1 and the colored portion B1, that is, the focus correction coefficient corresponding to the type of the light source.

  In step 105, the camera microcomputer 100 communicates with the interchangeable lens 11 (lens microcomputer 112), and whether or not the interchangeable lens 11 has chromatic aberration data (information regarding chromatic aberration) corresponding to the focus detection baseline length of the camera 1. To check. If the interchangeable lens 11 has chromatic aberration data, the process proceeds to step 105A.

  In step 105A (chromatic aberration acquisition step), the camera microcomputer 100 sends a transmission command to the lens microcomputer 112 to request transmission of chromatic aberration data corresponding to the focus detection baseline length. In response to this communication, the lens microcomputer 112 obtains chromatic aberration data corresponding to the current focal length, position information of the focus lens 12 and the focus detection baseline length from a memory (ROM) 112 a serving as a storage means in the lens microcomputer 112. read out. Then, the chromatic aberration data is transmitted to the camera microcomputer 100. On the other hand, if the interchangeable lens 11 does not have chromatic aberration data, the process proceeds to step 105B.

  In step 105 </ b> B, the camera microcomputer 100 acquires the type of the interchangeable lens 11, the focal length, and the position information of the focus lens 12 from the lens microcomputer 112. Then, chromatic aberration data corresponding to the focus detection baseline length of the camera is read from the memory 100a in the camera microcomputer 100 in accordance with these pieces of information.

  Further, in the next step 106, the camera microcomputer 100 multiplies the chromatic aberration data acquired in step 105A or step 105B by the focus correction coefficient obtained in step 104 to obtain corrected chromatic aberration data.

  Next, in step 107, the camera microcomputer 100 corrects the defocus amount by adding the corrected chromatic aberration data obtained in step 106 to the defocus amount obtained in step 102, thereby correcting the defocus amount (focus control). Information to be used).

  Steps 106 and 107 correspond to a control information generation step.

  In the next step 108, it is determined whether or not the corrected defocus amount is within the focus allowable range. The focus allowable range is, for example, a range of 1/4 × Fδ. F is the aperture value of the lens, and δ is the minimum circle of confusion. When F = 2.0 and δ = 20 μm, the allowable focusing range at the wide aperture is 10 μm.

  If the corrected defocus amount is within the focus allowable range, it is determined that the focus is in focus, and the AF operation is terminated. On the other hand, if the corrected defocus amount is out of the focus allowable range, the process proceeds to step 109, and the driving amount (including the driving direction) of the focus lens 12 obtained from the corrected defocus amount is transmitted to the lens microcomputer 112 to focus. Commands the lens 12 to be driven. Upon receiving this command, the lens microcomputer 112 controls the focus drive motor 16 according to the received drive amount and moves the focus lens 12. Then, the process returns to step 101 and the operations of step 101 to step 109 are repeated until the in-focus determination is made in step 108.

  FIG. 12 shows how much the amount of focus deviation occurs depending on the focal length and subject distance when the light source is the sun (white daylight) and when it is a fluorescent lamp. Specifically, it is an example of chromatic aberration data stored in a table in the ROM when a zoom lens of 35 to 70 mm is attached to the camera 1 as the lens unit 11.

  This data indicates the amount of focus shift under a typical fluorescent lamp as a light source that emits a lot of light in the short wavelength region with respect to the AF position in daylight (matches the amount of chromatic aberration due to the difference in the center of gravity wavelength). The amount of focus shift at the subject distance at each focal length of the lens is shown.

  From such a table, the amount of deviation is read out from the ROM using the focal length and subject distance (the position of the focusing lens 12 read by the distance encoder 18) as addresses. As described above, this data is stored as a table in the ROM for each baseline length corresponding to each line sensor pair. In response to a transmission command from the camera microcomputer 100, the lens microcomputer 112 reads chromatic aberration data corresponding to the focus detection baseline length from the ROM.

  Here, the chromatic aberration data corresponding to the focal length and the position information of the focus lens 12 is read out at this time. Note that the chromatic aberration data as shown in FIG. 12 is included in each interchangeable lens unit, and is basically a value determined by optical design, and may be stored in the ROM in a fixed manner. However, in consideration of manufacturing errors, the amount of focus shift may be measured during manufacturing and stored in a writable storage means such as an EEPROM or a flash ROM.

  Alternatively, the amount of focus movement may be approximated by a polynomial with the focal length and the subject position as parameters, and the coefficient of the polynomial may be stored in a ROM, EEPROM, flash ROM, or the like. In this case, when using the amount-of-focus data, the calculation may be performed based on the focal length and the subject distance.

  FIG. 10 shows the flow of the release operation of the camera system. When the AF operation shown in FIG. 9 is completed and the switch SW2 is turned on by the second stroke operation of the release button, the release operation is started from step 201.

  In step 201, the camera microcomputer 100 obtains the subject brightness BV from the photometric value of the photometric sensor 7, and adds the set ISO sensitivity SV to obtain the exposure value EV. Then, an aperture value AV and a shutter speed TV are calculated from the exposure value EV.

  In the next step 202, the camera microcomputer 100 performs an up operation to retract the main mirror 2 and the sub mirror 20 from the imaging optical path, and transmits the aperture value AV determined in step 202 to the lens microcomputer 112. . The lens microcomputer 112 receives the information of the aperture value AV and operates the aperture 15 through the aperture drive motor 17 to reduce the aperture diameter from the open state to the set aperture diameter.

  When the main mirror 2 is retracted from the imaging 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.

  Thereafter, when the set 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. As a result, the exposure ends, and in step 205, the main mirror 2 and the sub mirror 20 are lowered into the imaging optical path, and this flow ends.

  As described above, the camera 1 of the present embodiment has a plurality of lines that have different base line lengths and detect the phase difference between the two images formed by the light flux from the interchangeable lens 11 attached to the camera 1. It has sensor pairs 29a, 29b and 29c, 29d. Further, it includes a color temperature detection sensor 32 that detects a wavelength component included in a light beam from a subject, and a camera microcomputer 100 that generates information used for focus control. The camera microcomputer 100 acquires chromatic aberration data corresponding to the base line length of a specific line sensor pair used for phase difference detection (that is, focus detection) among a plurality of line sensor pairs. Then, the camera microcomputer 100 corrects the corrected defocus amount (information used for focus control) based on the phase difference obtained by the specific line sensor pair, the acquired chromatic aberration data, and the detection result by the color temperature sensor 32. ) Is generated.

  On the other hand, the interchangeable lens 11 has a memory 112 a that stores chromatic aberration data of the interchangeable lens 11. Then, the lens microcomputer 112 a transmits chromatic aberration data corresponding to the base line length of the specific line sensor pair among the plurality of line sensor pairs to the camera 1 in response to a transmission command from the camera 1.

  Thus, according to this embodiment, in addition to the type of light source and the type of interchangeable lens, defocus amount correction that takes into account different chromatic aberration amounts for each base line length of the pair of line sensors used for focus detection, that is, a focus lens Twelve focusing position corrections can be performed. Therefore, extremely high-precision focus control can be performed.

  In the above-described embodiment, the case where the focus correction coefficient and the chromatic aberration data shown in FIG. 11 are stored as table data in the memories 100a and 112a, and read out from the memories 100a and 112a has been described. However, the focus correction coefficient and the chromatic aberration data may be stored in the memories 100a and 112a, and the focus correction coefficient and the chromatic aberration data may be calculated using the calculation formula. In this case, a calculation formula for chromatic aberration data is also included in the information regarding chromatic aberration. In the above-described embodiment, the chromatic aberration data is corrected according to the light source discrimination result (luminance difference between the transmission portion A1 and the coloring portion B1), and the corrected chromatic aberration data and the defocus amount obtained from the phase difference information are used. The correction defocus amount was calculated. However, the corrected defocus amount obtained using the chromatic aberration data and the defocus amount obtained from the phase difference information may be further corrected according to the determination result of the light source.

  The embodiment of the present invention is not limited to a single-lens reflex digital camera system, but can be applied to an interchangeable lens type video camera using a phase difference detection method.

1 is a block diagram showing a configuration of a single-lens reflex digital camera system that is an embodiment of the present invention. FIG. 3 is a diagram illustrating a secondary imaging lens in the focus detection unit used in the first embodiment. The figure which shows the visual field mask in the said focus detection unit. The figure which shows the line sensor in the said focus detection unit. It is a figure which shows the exit pupil of the interchangeable lens used in an Example. 1 is a block diagram illustrating a circuit configuration of a camera system according to an embodiment. The figure which shows the structure of the color temperature sensor used in an Example. The figure for demonstrating the spectral sensitivity characteristic of the said color temperature sensor. 6 is a flowchart showing an AF operation of the camera system of the embodiment. 6 is a flowchart illustrating a release operation of the camera system according to the embodiment. FIG. 6 is a diagram illustrating a focus correction coefficient according to a light source determination result in the camera system of the embodiment. The figure which shows the amount of focus deviation | shift according to the light source in the camera system of an Example. It is a figure which shows the spectral sensitivity of a light source, an image pick-up element, and auxiliary light.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Single-lens reflex digital camera 7 Photometric sensor 11 Interchangeable lens 12 Focus lens 24 Focus detection unit 26 Secondary imaging lens unit 29 Line sensor unit 100 Camera microcomputer 112 Lens microcomputer

Claims (9)

An imaging device capable of attaching and detaching a lens device,
A plurality of focus detection sensors each having a different baseline length and detecting a phase difference between two images formed by a light beam from a lens device mounted on the imaging device;
A wavelength component detection sensor for detecting a wavelength component contained in a light flux from a subject;
Control means for generating information used for focus control of the lens device,
The control means acquires information on the chromatic aberration according to a base length of a specific focus detection sensor used for focus detection among the plurality of focus detection sensors, the phase difference obtained by the specific focus detection sensor, and the An image pickup apparatus that generates information used for the focus control based on the acquired information on chromatic aberration and the detection result of the wavelength component detection sensor.   The imaging apparatus according to claim 1, wherein the control unit acquires information relating to chromatic aberration according to a baseline length of the specific focus detection sensor from the lens device. The imaging apparatus includes a storage unit that stores information on chromatic aberration according to the baseline length,
The imaging apparatus according to claim 1, wherein the control unit acquires information on chromatic aberration according to a baseline length of the specific focus detection sensor from the storage unit.   The control means acquires the information from the lens device when the lens device has information on the chromatic aberration according to the baseline length of the specific focus detection sensor, and the lens device acquires the baseline length of the specific focus detection sensor. The imaging apparatus according to claim 1, wherein the information is acquired from a storage unit provided in the imaging apparatus when the information regarding the chromatic aberration according to the information is not included.   The control unit corrects information related to the chromatic aberration according to a detection result by the wavelength component detection sensor, and uses the phase difference obtained by the specific focus detection sensor and the corrected information based on the corrected information. Information is generated, The imaging device according to any one of claims 1 to 4 characterized by things. An imaging device according to any one of claims 1 to 5,
An imaging system comprising: a lens device detachably attached to the imaging device. A lens apparatus that has a different baseline length and is detachable from an imaging apparatus having a plurality of focus detection sensors that respectively detect a phase difference between two images formed by light beams from the lens apparatus,
Storage means for storing information relating to chromatic aberration of the lens device;
Control means for transmitting to the imaging device information related to the chromatic aberration according to a base line length of a specific focus detection sensor used for focus detection among the plurality of focus detection sensors in response to a transmission command from the imaging device. A lens device. A focus detection sensor for detecting a phase difference between two images formed by a light beam from a lens device attached to the imaging device, the imaging device having a detachable lens device and having different baseline lengths; A method of controlling an imaging apparatus having a wavelength component detection sensor for detecting a wavelength component included in a light beam from a subject,
Obtaining a phase difference from a focus detection sensor selected from the plurality of focus detection sensors;
Obtaining a detection result by the wavelength component detection sensor;
A chromatic aberration acquisition step of acquiring information relating to chromatic aberration of the lens device;
A control information generation step for generating information used for focus control of the lens device,
In the chromatic aberration acquisition step, the information about the chromatic aberration according to the baseline length of the specific focus detection sensor used for focus detection among the plurality of focus detection sensors is acquired,
In the control information generation step, it is used for the focus control based on the phase difference obtained by the specific focus detection sensor, the information on the chromatic aberration obtained in the chromatic aberration acquisition step, and the detection result by the wavelength component detection sensor. A method for controlling an imaging apparatus, characterized by generating information. A control method for a lens apparatus that has a different base line length and can be attached to and detached from an imaging apparatus having a plurality of focus detection sensors that detect phase differences between two images formed by light beams from the lens apparatus,
Reading out information relating to chromatic aberration of the lens device according to a base length of a specific focus detection sensor used for focus detection among the plurality of focus detection sensors from a storage unit;
And a step of transmitting the read information to the imaging device in response to a transmission command from the imaging device.