JP2009053568A - Imaging apparatus and imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform highly accurate focus control by correctly detecting a light source, even in the case where irradiation is performed with AF auxiliary light. <P>SOLUTION: An imaging apparatus 1 includes: illumination means 33 which irradiates a subject with auxiliary light for detecting focus; focus detection means 29 which receives light from the subject, to produce a focus detection signal for obtaining the information of the focus state of an imaging optical system; light source detection means 31 which receives the light from the subject, to produce a light source detection signal for obtaining the information of the light source; and control means 100 which produces the information used for focus control by using the information of the focus state and the information of the light source and controls the lighting of the illumination means. When the illumination means is lighted to detect the focus, the control means continues the lighting of the illumination means, until at least the generation of the focus detection signal by the focus detection means and the generation of the light source detection signal by the light source detection means are completed. <P>COPYRIGHT: (C)2009,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 a light source discrimination result.

  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 an imaging 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, in many cases, the sensitivity is extended to a long wavelength region of about 100 nm further than 1100 nm so that accurate focus detection can be performed by irradiating a low-intensity subject with AF auxiliary light in the near infrared region (about 700 nm).

  FIG. 12 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 is a fluorescent lamp, L is a flood lamp, and A is the spectral sensitivity of the AF 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 under illumination with a fluorescent lamp and a flood lamp with a small long wavelength component, and as a result, the focus on the image sensor is different. It will shift.

  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 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.

Further, in Patent Document 2, the amount of chromatic aberration of an interchangeable lens is stored in an in-lens memory, and a method of obtaining a defocus correction amount by multiplying a lens chromatic aberration amount by a predetermined coefficient based on a determination result of the type of light source. It is disclosed.
JP 2000-275512 A (paragraphs 0041 to 0110, FIGS. 3 to 10 and the like) JP-A-62-174710 (page 6, upper left column, line 2 to page 7, upper left column, line 3, FIG. 9 etc.)

  However, the cameras disclosed in Patent Documents 1 and 2 do not mention light source correction in focus control when AF auxiliary light is irradiated. Furthermore, depending on the difference between the irradiation timing of the AF auxiliary light and the detection timing of the light source, an error occurs in the light source determination, resulting in a problem that incorrect focus correction is performed.

  The shift of the focus position due to the spectral wavelength when the AF auxiliary light is irradiated will be described with reference to FIGS.

  FIG. 13 shows the positional relationship between the AF auxiliary light irradiation range and the AF field of view on the imaging screen. The light obtained by the AF sensor becomes a mixed light of the ambient light and the AF auxiliary light, and the focus position shifts due to the spectral wavelength of the mixed light. Here, the environmental light is light other than illumination light from the camera side. In addition, the AF auxiliary light referred to here has substantially uniform luminance within the irradiation range or AF visual field.

  FIG. 14 shows a conventional AF auxiliary light irradiation timing and charge accumulation timing of the AF sensor and the light source detection sensor.

  Since the spectral sensitivity characteristic differs between the AF sensor and the light source detection sensor, a difference occurs in the charge accumulation time. In this figure, the light source detection sensor requires more storage time than the AF sensor. Further, normally, the AF auxiliary light is irradiated only during the charge accumulation of the AF sensor, and is turned off to suppress energy consumption during other operations.

  As described above, the AF auxiliary light is irradiated from the start of accumulation of the AF sensor to the end of accumulation, but is not irradiated during a part of the accumulation time of the light source detection sensor. For this reason, the output from the light source detection sensor includes an error during a period when the AF auxiliary light is not irradiated. Therefore, the mixed light of the ambient light and the AF auxiliary light cannot be accurately detected, and as a result, erroneous focus correction is performed.

  The present invention provides an imaging apparatus capable of performing accurate light source detection and performing highly accurate focus control even in a situation where AF auxiliary light is irradiated.

  An imaging apparatus according to an aspect of the present invention includes an illuminating unit that irradiates a subject with focus detection auxiliary light, and a focus detection signal that receives light from the subject and obtains information regarding the focus state of the imaging optical system. A focus detection unit that generates light, a light source detection unit that receives light from the object and generates a light source detection signal for obtaining information about the light source, and information used for focus control using the information about the focus state and the information about the light source And control means for controlling lighting of the illumination means. When the focus detection is performed by turning on the illumination unit, the control unit performs at least the generation of the focus detection signal by the focus detection unit and the generation of the light source detection signal by the light source detection unit. It is characterized by continuing lighting.

  According to the present invention, when focus detection is performed by irradiating the subject with focus detection auxiliary light, generation of the focus detection signal by the focus detection unit and generation of the light source detection signal by the light source detection unit are completed. Continuously irradiates the auxiliary light. For this reason, the mixed light of environmental light and illumination light can be detected accurately, and information on the highly accurate light source can be obtained. Therefore, highly accurate focus control can be performed even when illumination light is used under various light sources.

  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 housed in the camera 1, and an image (or photograph) obtained by capturing an image of a subject can be acquired.

  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, when the main mirror 2 is a half mirror and is disposed in the imaging optical path, approximately half of the light beam from the subject is transmitted to a focus detection optical system, which will be described later, and the rest is reflected to the finder optical system. .

  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 an imaging optical system described later. Reference numeral 4 denotes a finder optical path changing pentaprism. Reference numeral 5 denotes an eyepiece, from which the imager can observe the subject image by looking at the focusing plate 3 through the pentaprism 4.

  Reference numerals 6 and 7 denote a first imaging lens and a photometric sensor for measuring subject luminance within the viewfinder field (that is, the imaging range). Reference numerals 30 and 31 respectively denote a second imaging lens and a light source detection sensor (light source detection means) for performing photometry in order to acquire information on the light source that illuminates the subject in the viewfinder field.

  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 imaging optical path together with the main mirror 2 in the finder observation state, and retracts out of the imaging optical path in the imaging state. The sub mirror 25 reflects the light beam transmitted through the main mirror 2 disposed in the imaging optical path downward and guides it to a focus detection unit described later.

  A focus detection unit 26 includes a secondary imaging mirror 27, a secondary imaging lens 28, and a focus detection sensor (focus detection means) 29. The secondary imaging mirror 27 and the secondary imaging lens 28 constitute a focus detection optical system, and form a secondary image formation surface of the imaging optical system on the focus detection sensor 29.

  The focus detection unit 26 receives light from the subject and performs focus detection to detect the focus state of the imaging optical system by a so-called phase difference detection method. Specifically, the focus detection sensor 29 generates pixel information having a phase difference as a focus detection signal corresponding to the focus state of the imaging optical system, and sends the pixel information to a camera microcomputer to be described later.

  Reference numerals 32 and 33 denote a projection lens and an AF auxiliary light source (illuminating means) for irradiating the subject with AF auxiliary light (focus detection auxiliary light). The AF auxiliary light source 33 emits AF auxiliary light in the near infrared region (about 700 nm).

  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. The first lens unit (hereinafter referred to as a focus lens) 12 performs focus adjustment by moving in the optical axis direction. The second lens unit 13 performs zooming by changing the focal length of the imaging optical system by moving in the optical axis direction.

  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 generates a signal corresponding to the subject distance corresponding to the position of the focus lens 12 when the brush 19 attached to the focus lens 12 slides.

  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 29, a photometric sensor 7, a light source detection sensor 31, 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 150 arranged in the interchangeable lens 11 via the mount contact 10.

  The light source detection sensor 31 receives light from the subject and generates a light source detection signal for obtaining information about the light source. The light source detection sensor 31 includes two visible light sensors 311 and infrared light sensors 312 having different spectral wavelengths. The light source detection sensor 31 causes the visible light sensor 311 and the infrared light sensor 312 to perform a photoelectric conversion operation according to a signal from the camera microcomputer 100, and performs charge accumulation control and charge readout control. Then, the luminance information obtained by each of the sensors 311 and 312 is output to the camera microcomputer 100 as a light source detection signal.

  The camera microcomputer 100 A / D converts this luminance information, and the ratio of luminance values (luminance ratio) detected by the visible light sensor 311 and the infrared light sensor 312 is information relating to the light source (hereinafter simply referred to as light source information). Generate as

  The focus detection sensor 29 includes a pair or a plurality of pairs of CCD line sensors, and performs a photoelectric conversion operation on the subject image. The focus detection sensor 29 performs charge accumulation control and charge readout control of the CCD line sensor in accordance with a signal from the camera microcomputer 100. Then, pixel information (information representing two images formed on the pair of line sensors) as a focus detection signal is output to the camera microcomputer 100 from each line sensor.

  The camera microcomputer 100 performs A / D conversion on the pixel information and generates a phase difference (information on the focus state) of the pixel information. Further, based on the phase difference, a defocus amount of the imaging optical system, that is, information used for focus control is generated.

  Further, the camera microcomputer 100 controls the lighting of the AF auxiliary light source 33. Furthermore, as will be described in detail later, the camera microcomputer 100 performs correction according to the light source of the defocus amount (hereinafter referred to as light source correction of the defocus amount) using the information regarding the light source.

  Then, based on the defocus amount corrected for the light source, focus sensitivity information of the imaging optical system, and the like, a drive amount of the focus lens 12 (a drive amount of the focus drive motor 16) for obtaining focus is calculated. The driving amount information of the focus lens 12 is transmitted to the lens microcomputer 150. The lens microcomputer 150 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.

  The AF auxiliary light source 33 is turned on according to a signal from the camera microcomputer 100 and irradiates the subject with AF auxiliary light via the projection lens 32. By irradiating the AF auxiliary light, even when the subject is dark, the subject luminance is compensated to facilitate focus detection.

  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. Thereby, the shutter front curtain and the rear curtain travel, and the image sensor 9 (or film) 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 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 in the interchangeable lens 11, and a power contact L1 for the lens microcomputer 150, and a clock for serial data communication. Contact point 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 150. And a ground contact L6.

  The lens microcomputer 150 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, respectively. 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 150 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 150 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 150. The lens microcomputer 150 converts the position information into subject distance information and transmits it to the camera microcomputer 100.

  Next, a control method of the focus detection sensor 29 will be described using the timing chart of FIG.

  In the figure, an AF_START signal (accumulation start signal), an AF_READ signal (read enable signal), and an AF_SRP signal (read serial signal) are control signals from the camera microcomputer 100 to the focus detection sensor 29. An AF_TINT signal (accumulation end signal) and an AF_SIG signal (analog output signal) are output signals from the focus detection sensor 29.

  First, when the camera microcomputer 100 switches the AF_START signal from Lo to Hi, the focus detection sensor 29 once resets the charge in the sensor, and then starts the charge accumulation operation. The focus detection sensor 29 is equipped with a monitor circuit for the charge accumulation amount, and when the charge accumulation amount of the pixel that accumulates the most charge among a plurality of pixels constituting the line sensor reaches a predetermined amount, the charge accumulation amount is accumulated. To indicate the completion of the operation, the AF_TINT signal is switched from Lo to Hi.

  When the camera microcomputer 100 monitors the state of the AF_TINT signal and confirms that the AF_TINT signal is switched from Lo to Hi, the camera microcomputer 100 outputs the AF_READ signal and the AF_SRP signal at the timing shown in FIG. . The focus detection sensor 29 outputs a voltage signal (pixel information) corresponding to the charge accumulation amount of each pixel as an AF_SIG signal (focus detection signal) in synchronization with the AF_SRP signal.

  Next, a method for controlling the light source detection sensor 31 will be described with reference to the timing chart of FIG.

  In the figure, an LS_START signal (accumulation start signal), an LS_READ signal (read enable signal), and an LS_SRP signal (read serial signal) are control signals from the camera microcomputer 100 to the light source detection sensor 31. The LS_TINT signal (storage end signal) and the LS_SIG signal (analog output signal) are output signals from the light source detection sensor 31.

  When the camera microcomputer 100 switches the LS_START signal from Lo to Hi, the light source detection sensor 31 once resets the charge in the sensor and then starts the charge accumulation operation. The light source detection sensor 31 includes a charge accumulation amount monitoring circuit, and when the charge accumulation amount of either the visible light sensor 311 or the infrared light sensor 312 reaches a predetermined amount, the charge accumulation operation is completed. To illustrate, the LS_TINT signal is switched from Lo to Hi.

  When the camera microcomputer 100 confirms that the LS_TINT signal has been switched from Lo to Hi, the camera microcomputer 100 outputs the LS_READ signal and the LS_SRP signal at the timing shown in order to perform the charge reading operation of the light source detection sensor 31. The light source detection sensor 31 outputs a voltage signal corresponding to the charge accumulation amount of each of the visible light sensor 311 and the infrared light sensor 312 as an LS_SIG signal (light source detection signal) in synchronization with the LS_SRP signal.

  The light source detection sensor 31 used in the present embodiment requires a longer time for the charge accumulation operation than the focus detection sensor 29 as shown in FIG.

  Next, spectral characteristics of the visible light sensor 311 and the infrared light sensor 312 will be described with reference to FIG. In the figure, the horizontal axis represents wavelength (nm) and the vertical axis represents spectral sensitivity. W is the spectral sensitivity characteristic of the visible light sensor 311, and IR is the spectral sensitivity characteristic of the infrared light sensor 312.

  As can be seen from this figure, the visible light sensor 311 mainly detects light in the visible light region, and the infrared light sensor 312 mainly detects light in the long wavelength region having peak sensitivity in the near infrared 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 the figure) 101. The camera microcomputer 100 outputs an AF_START signal and an LS_START signal, and starts charge accumulation in the focus detection sensor (referred to as AF sensor in the figure) 29 and the light source detection sensor 31.

  In step 102, the camera microcomputer 100 determines whether or not the charge accumulation operation of the focus detection sensor 29 is completed by monitoring the AF_TINT signal. When the AF_TINT signal is switched from Lo to Hi and it is determined that the charge accumulation operation is completed, the charge accumulation operation is stopped and the process proceeds to Step 103.

  In step 103, the camera microcomputer 100 determines whether or not the charge accumulation operation of the light source detection sensor 31 is completed by monitoring the LS_TINT signal. When the LS_TINT signal is switched from Lo to Hi and it is determined that the charge accumulation operation is completed, the charge accumulation operation is stopped and the process proceeds to Step 104.

  In step 104, the camera microcomputer 100 outputs an AF_READ signal and an AF_SRP signal, and performs an operation of reading the AF_SIG signal (pixel information) from the focus detection sensor 29. In step 105, the camera microcomputer 100 A / D-converts pixel information and detects a phase difference between the pixel information. Further, the defocus amount of the imaging optical system is calculated based on the phase difference.

  In step 106, the camera microcomputer 100 calculates the contrast value of the pixel information acquired in step 104, and determines the reliability of the defocus amount detection result. If the calculated contrast value is greater than or equal to the predetermined value, it is determined that the reliability of the detection result is high, the process proceeds to step 115, and the light source correction of the defocus amount and the focus control operation are performed. On the other hand, when the contrast value is smaller than the predetermined value, it is determined that the reliability of the detection result is low, the process proceeds to step 107, and the AF operation using the AF auxiliary light is performed. The contrast value can be calculated by accumulating the level difference between the output signals of adjacent pixels or calculating the difference between the maximum value and the minimum value of the output signals of all pixels.

  In step 107, the camera microcomputer 100 controls the lighting of the AF auxiliary light source 33 to irradiate the subject with AF auxiliary light. In step 108, the camera microcomputer 100 outputs the AF_START signal and the LS_START signal, and starts the charge accumulation operation of the focus detection sensor 29 and the light source detection sensor 31.

  In step 109, the camera microcomputer 100 determines whether or not the charge accumulation operation of the focus detection sensor 29 is completed by monitoring the AF_TINT signal. When the AF_TINT signal is switched from Lo to Hi and it is determined that the charge accumulation operation is completed, the charge accumulation operation is stopped and the process proceeds to Step 110.

  In step 110, the camera microcomputer monitors the LS_TINT signal to determine whether or not the charge accumulation operation of the light source detection sensor 31 has been completed. When the LS_TINT signal is switched from Lo to Hi and it is determined that the charge accumulation operation is completed, the charge accumulation operation is stopped and the process proceeds to Step 111.

  In step 111, the camera microcomputer 100 stops (turns off) driving of the AF auxiliary light source 33. By turning off the AF auxiliary light source 33 at this timing, the irradiation of the AF auxiliary light to the subject is continued until both the charge accumulation operation of the focus detection sensor 29 and the charge accumulation operation of the light source detection sensor 31 are completed. It will be. In other words, the AF auxiliary light source 33 remains on until both the focus detection signal generation by the focus detection sensor 29 and the light source detection signal generation by the light source detection sensor 31 are completed.

  In step 112, the camera microcomputer 100 outputs an AF_READ signal and an AF_SRP signal, and performs an operation of reading the AF_SIG signal (pixel information) from the focus detection sensor 29. In step 113, the camera microcomputer 100 performs A / D conversion on the pixel information and detects a phase difference between the pixel information. Further, the defocus amount of the imaging optical system is calculated based on the phase difference.

  In step 114, the camera microcomputer 100 calculates the contrast value of the pixel information acquired in step 112, and determines the reliability of the defocus amount detection result. If the contrast value is equal to or greater than a predetermined value, it is determined that the reliability of the detection result is high, the process proceeds to step 115, and the light source correction of the defocus amount and the focus control operation are performed. On the other hand, if the contrast value is smaller than the predetermined value, it is determined that the reliability of the detection result is low, and the AF operation is terminated as AF-NG.

  On the other hand, in step 115, the camera microcomputer 100 requests the lens microcomputer 150 to transmit chromatic aberration amount data specific to the interchangeable lens (imaging optical system). This request is transmitted to the lens microcomputer 150 via the serial communication line L3 shown in FIG.

  Upon receiving the request, the lens microcomputer 150 first analyzes the content of the request (communication). When 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 imaging optical system is read from a ROM table (not shown) in the lens microcomputer 150. 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 stored in the ROM table. The lens microcomputer 150 returns the chromatic aberration amount data to the camera microcomputer 100 via the serial communication line L4.

  In step 116, the camera microcomputer 100 outputs the LS_READ signal and the LS_SRP signal, and performs the reading operation of the LS_SIG signal from the light source detection sensor 31. In step 117, the camera microcomputer 100 A / D converts luminance information from the visible light sensor 311 and the infrared light sensor 312 represented by the LS_SIG signal. Further, the ratio of the luminance information, that is, the luminance ratio is calculated. Then, the correction coefficient is read out from the table shown in FIG. 8 according to the luminance ratio (infrared light / visible light).

  In step 118, the camera microcomputer 100 multiplies the chromatic aberration amount data obtained in step 115 by the correction coefficient obtained in step 117. Further, the multiplication result is added to the defocus amount obtained in step 105 or 113 to calculate the defocus amount after the light source correction.

  Note that correcting the defocus amount is not only generating a new defocus amount (defocus amount after light source correction), and in this sense, correcting in the present embodiment can be rephrased as generating. .

  In step 120, when the defocus amount after light source correction is within a specific range, it is determined that the focus is achieved, and the process proceeds to step 122. When the corrected defocus amount is larger than the specific range, the process proceeds to step 121, and the drive amount for focusing the focus lens 12 is calculated from the corrected defocus amount. Then, the driving amount information is transmitted to the lens microcomputer 150 via the serial communication line L3 described above.

  The lens microcomputer 150 that has received the drive amount information drives the focus drive motor 16 in accordance with the drive amount information. Then, the process returns to step 101, and the operations of the respective steps described above are repeated until it is determined in step 120 that focus is achieved.

  In step 122, the camera microcomputer 100 determines whether SW2 is ON. If it is ON, the process proceeds to step 201 shown in FIG. 5, and an imaging operation is performed. If SW2 is OFF, the AF operation process is terminated.

  Next, the imaging operation will be described with reference to FIG. If the above-described AF operation is completed and SW2 is ON, the camera microcomputer 100 obtains the subject brightness BV based on the photometric value from the photometric sensor 7 that measures the subject brightness in step 201. Then, the subject brightness BV is 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 from the exposure value EV.

  In step 202, the camera microcomputer 100 moves the main mirror 2 up and retracts it from the imaging optical path. At the same time, the camera microcomputer 100 instructs the lens microcomputer 150 to reduce the aperture 15 to the aperture value AV determined in step 202. The lens microcomputer 150 receives the command and drives the aperture drive motor 17.

  Thereafter, when the main mirror 2 is completely 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.

  When the 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 and places it in the imaging optical path, and ends the imaging operation.

  As described above, when focus detection is performed by irradiating the subject with AF auxiliary light, not only the charge accumulation operation of the focus detection sensor 29 (generation of a focus detection signal) but also at least the charge accumulation operation of the light source detection sensor 31 (light source). Until the generation of the detection signal) is completed, the irradiation of the AF auxiliary light is continued. Therefore, the mixed light of the ambient light and the AF auxiliary light can be accurately detected, and information on the light source with high accuracy can be obtained. Therefore, even when AF auxiliary light is used under various light sources, highly accurate defocus amount correction, that is, focus control can be performed.

  The AF auxiliary light irradiation may be continued for a certain period of time after the charge accumulation operation of the light source detection sensor 31 is completed.

  FIG. 9 shows a single-lens reflex camera system (imaging system) that is Embodiment 2 of the present invention. FIG. 10 shows the configuration of the electric circuit of the camera system of this embodiment.

  9 and 10, the components other than the light source detection sensor 41 are the same as those of the camera system of the first embodiment. In the present embodiment, components common to the first embodiment are denoted by the same reference numerals as those in the first embodiment. In addition, since the components other than the light source detection sensor 41 have been described in the first embodiment, description thereof is omitted here.

  The light source detection sensor 41 includes two visible light sensors 411 and infrared light sensors 412 having different spectral wavelengths. The spectral characteristics of the visible light sensor 411 and the infrared light sensor 412 are the same as the spectral characteristics indicated by W and IR in FIG.

  The light source detection sensor 41 converts the photocurrent generated by the visible light sensor 411 into a voltage and outputs it as an LS_W signal (detection signal). The light source detection sensor 41 converts the photocurrent generated by the infrared light sensor 412 into a voltage and outputs it as an LS_IR signal (detection signal).

  The camera microcomputer 100 A / D converts the LS_W signal and the LS_IR signal. Then, by calculating the ratio of these voltages, the ratio of luminance values (luminance ratio) is generated as information about the light source.

  The light source detection sensor 31 in the first embodiment is a charge storage type sensor, whereas the light source detection sensor 41 in the present embodiment is an IV conversion type that converts a photocurrent into a voltage.

  In the first embodiment, the charge accumulation operation of the focus detection sensor 29 and the light source detection sensor 31 is started almost simultaneously. However, the time required for the charge accumulation operation (generation of the light source detection signal) of the light source detection sensor 31 is It is longer than the time required for the charge accumulation operation (generation of the focus detection signal). For this reason, in the first embodiment, control is performed to continue the irradiation of the AF auxiliary light until the charge accumulation operation in the light source detection sensor 31 is completed.

  On the other hand, in the present embodiment, the voltage reading timing from the light source detection sensor 41 (that is, the generation completion timing of the light source detection signal) is the completion of the charge accumulation operation (generation of the focus detection signal) in the focus detection sensor 29. This corresponds to the case where it is later than the timing. Even in this case, the same effect as that of the first embodiment can be obtained by continuing the irradiation of the AF auxiliary light until the output of the voltage from the light source detection sensor 41 is completed.

  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. The camera microcomputer 100 outputs an AF_START signal and starts the charge accumulation operation in the focus detection sensor 29.

  In step 302, the camera microcomputer 100 monitors the AF_TINT signal to determine whether or not the charge accumulation operation of the focus detection sensor 29 has been completed. When the AF_TINT signal is switched from Lo to Hi and it is determined that the charge accumulation operation is completed, the charge accumulation operation is stopped and the process proceeds to Step 303.

  In step 303, the camera microcomputer 100 outputs an AF_READ signal and an AF_SRP signal, and performs a read operation of the AF_SIG signal (pixel information: focus detection signal) from the focus detection sensor 29. In step 304, the camera microcomputer 100 A / D-converts pixel information and detects a phase difference between the pixel information. Further, the defocus amount of the imaging optical system is calculated based on the phase difference.

  In step 305, the camera microcomputer 100 calculates the contrast value of the pixel information acquired in step 304, and determines the reliability of the defocus amount detection result. If the calculated contrast value is equal to or greater than the predetermined value, it is determined that the reliability of the detection result is high, and the process proceeds to step 306.

  In step 306, the camera microcomputer 100 performs a reading operation of the LS_W signal and the LS_IR signal (light source detection signal) from the light source detection sensor 41. The camera microcomputer 100 A / D converts luminance information represented by the LS_W signal and the LS_IR signal from the visible light sensor 411 and the infrared light sensor 412, respectively.

  On the other hand, if the contrast value is smaller than the predetermined value in step 305, it is determined that the reliability of the detection result is low, and the process proceeds to step 307. In step 307 and subsequent steps, an AF operation using AF auxiliary light is performed.

  In step 307, the camera microcomputer 100 controls the lighting of the AF auxiliary light source 33 to irradiate the subject with AF auxiliary light. In step 308, the camera microcomputer 100 outputs an AF_START signal and starts the charge accumulation operation in the focus detection sensor 29.

  In step 309, the camera microcomputer 100 monitors the AF_TINT signal to determine whether or not the charge accumulation operation of the focus detection sensor 29 has been completed. When the AF_TINT signal is switched from Lo to Hi and it is determined that the charge accumulation operation is completed, the charge accumulation operation is stopped and the process proceeds to Step 310.

  In step 310, the camera microcomputer 100 performs a reading operation of the LS_W signal and the LS_IR signal from the light source detection sensor 41. The camera microcomputer 100 A / D converts luminance information represented by the LS_W signal and the LS_IR signal from the visible light sensor 411 and the infrared light sensor 412, respectively.

  In step 311, the camera microcomputer 100 stops driving (turns off) the AF auxiliary light source 33. By turning off the AF auxiliary light source 33 at this timing, the AF auxiliary light is continuously irradiated to the subject until both the charge accumulation operation of the focus detection sensor 29 and the luminance information reading operation from the light source detection sensor 41 are completed. Will be. In other words, the AF auxiliary light source 33 remains on until the focus detection signal generation by the focus detection sensor 29 and the generation and output of the LS_W signal and LS_IR signal (voltage: light source detection signal) by the light source detection sensor 41 are completed. Is done.

  In step 312, the camera microcomputer 100 outputs an AF_READ signal and an AF_SRP signal, and performs an operation of reading the AF_SIG signal (pixel information) from the focus detection sensor 29. In step 313, the camera microcomputer 100 performs A / D conversion on the pixel information and detects a phase difference between the pixel information. Further, the defocus amount of the imaging optical system is calculated based on the phase difference.

  In step 314, the camera microcomputer 100 calculates the contrast value of the pixel information acquired in step 312, and determines the reliability of the defocus amount detection result. If the contrast value is equal to or greater than a predetermined value, it is determined that the reliability of the detection result is high, the process proceeds to step 315, and the defocus amount light source correction and the focus control operation are performed. On the other hand, if the contrast value is smaller than the predetermined value, it is determined that the reliability of the detection result is low, and the AF operation is terminated as AF-NG.

  In step 315, the camera microcomputer 100 requests the lens microcomputer 150 to transmit chromatic aberration amount data specific to the interchangeable lens (imaging optical system). This request is transmitted to the lens microcomputer 150 via the serial communication line L3 shown in FIG.

  Upon receiving the request, the lens microcomputer 150 first analyzes the content of the request (communication). When 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 imaging optical system is read from a ROM table (not shown) in the lens microcomputer 150. 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 stored in the ROM table. The lens microcomputer 150 returns the chromatic aberration amount data to the camera microcomputer 100 via the serial communication line L4.

  In step 316, the camera microcomputer 100 calculates a ratio of luminance information from the visible light sensor 411 and the infrared light sensor 412 A / D converted in step 306 or 310, that is, a luminance ratio. Then, the correction coefficient is read out from the table shown in FIG. 8 according to the luminance ratio (infrared light / visible light).

  In step 317, the camera microcomputer 100 multiplies the chromatic aberration amount data acquired in step 315 by the correction coefficient obtained in step 316. Further, the multiplication result is added to the defocus amount obtained in step 304 or step 313 to calculate the defocus amount after light source correction.

  In step 319, if the defocus amount after light source correction is within a specific range, it is determined that focus is achieved, and the process proceeds to step 321. If the defocus amount after light source correction is larger than the specific range, the process proceeds to step 320, and the drive amount for focusing the focus lens 12 is calculated from the defocus amount after light source correction. Then, the driving amount information is transmitted to the lens microcomputer 150 via the serial communication line L3 described above.

  The lens microcomputer 150 that has received the drive amount information drives the focus drive motor 16 in accordance with the drive amount information. Then, the process returns to step 301, and the operation of each step described above is repeated until it is determined in step 319 that the focus is achieved.

  In step 321, the camera microcomputer 100 determines whether SW2 is ON. If it is ON, the process proceeds to step 201 shown in FIG. 5, and an imaging operation is performed. The imaging operation shown in FIG. 5 is the same as the operation described in the first embodiment. If SW2 is OFF, the AF operation process is terminated.

  As described above, when focus detection is performed by irradiating the AF auxiliary light onto the subject, not only the charge accumulation operation (generation of the focus detection signal) of the focus detection sensor 29 but also the information read operation (light source) from the light source detection sensor 41. The irradiation of the AF auxiliary light is continued until the generation and output of the detection signal is completed. Therefore, the mixed light of the ambient light and the AF auxiliary light can be accurately detected, and information on the light source with high accuracy can be obtained. Therefore, even when AF auxiliary light is used under various light sources, highly accurate defocus amount correction, that is, focus control can be performed.

  In the above embodiments, a single-lens reflex camera has been described. However, other embodiments of the present invention include a video camera that performs phase difference detection AF.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

1 is a schematic diagram showing a configuration of a single-lens reflex camera system that is Embodiment 1 of the present invention. FIG. FIG. 3 is a block diagram illustrating an electric circuit configuration in the camera system according to the first embodiment. The figure which shows the spectral sensitivity characteristic of the visible light sensor and infrared light sensor for a light source detection which are used for the camera system of an Example. 6 is a flowchart illustrating an AF operation in the camera system according to the first exemplary embodiment. 7 is a flowchart illustrating an imaging operation in the camera systems of Embodiments 1 and 2. 5 is a timing chart illustrating a method for controlling a focus detection sensor in the first and second embodiments. 4 is a timing chart illustrating a method for controlling the light source detection sensor according to the first embodiment. FIG. 6 is a diagram illustrating correction coefficients for infrared light / visible light in the camera systems of Examples 1 and 2; The schematic diagram which shows the structure of the single-lens reflex camera system which is Example 2 of this invention. FIG. 6 is a block diagram illustrating an electric circuit configuration in a camera system according to a second embodiment. 9 is a flowchart illustrating an AF operation in the camera system according to the second embodiment. The figure which shows the spectral sensitivity of a light source, an image pick-up element, and auxiliary light. The figure which showed the positional relationship of the irradiation range of AF auxiliary light, and AF visual field. The figure which showed the accumulation | storage timing of AF sensor and a light source detection sensor, and the irradiation timing of AF auxiliary light.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Camera 11 Interchangeable lens 12 Focus lens 29 Focus detection sensor 31, 41 Light source detection sensor 33 AF auxiliary light source 100 Camera microcomputer 150 Lens microcomputer

Claims (5)

Illumination means for irradiating the subject with focus detection auxiliary light;
A focus detection unit that receives light from the subject and generates a focus detection signal for obtaining information on a focus state of the imaging optical system;
Light source detection means for receiving light from the subject and generating a light source detection signal for obtaining information about the light source;
Control information for generating information used for focus control using information on the focus state and information on the light source, and controlling lighting of the illumination means;
When the control means performs the focus detection by turning on the illumination means, at least the generation of the focus detection signal by the focus detection means and the generation of the light source detection signal by the light source detection means are completed. Is an imaging apparatus characterized in that the lighting means continues to be lit.   The imaging apparatus according to claim 1, wherein a time required for generating the light source detection signal by the light source detection unit is longer than a time required for generating the focus detection signal by the focus detection unit.   The imaging apparatus according to claim 1, wherein a generation completion timing of the light source detection signal in the light source detection unit is later than a generation completion timing of the focus detection signal in the focus detection unit. The light source detection means generates the light source detection signal by accumulating charges by a photoelectric conversion operation,
4. The imaging apparatus according to claim 1, wherein the control unit continues lighting of the illumination unit at least until a charge accumulation operation in the light source detection unit is completed. The light source detection means outputs a voltage converted from a photocurrent as the light source detection signal,
4. The imaging apparatus according to claim 1, wherein the control unit continues lighting of the illumination unit at least until the output of the voltage from the light source detection unit is completed.