JP4865275B2 - Focus detection apparatus and imaging apparatus - Google Patents

Description

  The present invention relates to a focus detection device and an imaging device that obtain a correction value of a focus state detected by a phase difference detection method by a contrast detection method.

  Conventionally, in a camera system, a TTL phase difference detection type focus detection method is generally used. However, it is difficult to completely match the in-focus position detected by this phase difference detection method with the actual in-focus surface.

  This is because of errors that occur when a sensor module of the phase difference detection method is attached to the camera body, errors on the camera body side such as dimensional errors of the optical system that constitutes the sensor module, and photography that is manufactured separately from the camera body. This is due to factors such as lens manufacturing errors.

  As an apparatus for correcting a manufacturing error, an electronic imaging apparatus having a first focus detection unit of a phase difference detection method and a second focus detection unit that evaluates contrast from an image signal of an imaging element and performs autofocusing. It is disclosed in Japanese Patent Laid-Open No. 2000-292684 (Patent Document 1). This calculates the relative deviation amount from the autofocus data by the first and second focus detection means, and corrects the error on the camera body side by correcting the autofocus data of the first focus detection means.

Japanese Patent Laid-Open No. 2003-295047 (Patent Document 2) discloses an imaging apparatus that calculates a correction value by contrast detection for each distance measurement area in a camera system having a plurality of line sensors for phase difference detection. Has been proposed.
JP 2000-292684 A JP 2003-295047 A

  The conventional technology has the following problems.

  In a camera system having a plurality of line sensors for phase difference detection, high accuracy and high speed when calculating a correction value by contrast detection for each distance measurement area are described in Patent Documents 1 and 2. It remains an important issue.

(Object of the present invention)
An object of the present invention is to provide a focus detection device and an imaging device that can achieve high accuracy when a correction value of a focus state detected by a phase difference detection method is obtained by a contrast detection method.

In order to achieve the above object, the first aspect of the present invention has a plurality of focus detection areas that can be selected, and a focus state based on a phase difference of image signals from a pair of sensor rows corresponding to the selected focus detection area. A first focus detection means for detecting the contrast, and a contrast detection means for detecting a contrast in a predetermined direction of an image in a contrast detection area corresponding to the sensor row pair among images read out from the imaging sensor , and the contrast an imaging apparatus which have a second focus detection means for detecting a focus state based on the detection result by the detection means, when the second focus detection unit detects the focus state, the focus detection area selected The direction of contrast detection by the contrast detection means is switched in accordance with the direction of the sensor array pair corresponding to the focus detection area and It is characterized in that the last detected direction corresponds.
Furthermore, the second aspect of the present invention provides a first focus detection means for detecting a focus state based on a phase difference of image signals from a sensor array pair corresponding to a focus detection area, and an image read out from an image sensor. Among them, a second focus detection unit that includes a contrast detection unit that detects a contrast in a predetermined direction of an image in a contrast detection area corresponding to the sensor row pair, and detects a focus state based on a detection result by the contrast detection unit; The first detection mode for performing normal shooting as the shooting mode, and the correction of the focus detection result based on the focus detection results of the first focus detection unit and the second detection unit, respectively. A second mode for determining the amount, and switching a contrast detection direction by the contrast detection means in accordance with switching to the second mode It allows in which arrangement direction and the contrast detection direction of the sensor array pairs corresponding to the focus detection area is equal to or corresponding.

  According to the present invention, it is possible to achieve high accuracy when the correction value of the focus state detected by the phase difference detection method is obtained by the contrast detection method.

  The best mode for carrying out the present invention is as described in Examples 1 to 4 described later.

  FIG. 1 is a block diagram showing an example of the electrical configuration of a single-lens reflex digital camera system that is Embodiment 1 of the present invention.

  As shown in FIG. 1, the taking lens unit 100 is detachably attached to the digital camera 200 of this embodiment via a mount mechanism (not shown). The mount portion has an electrical contact group 107. The contact group 107 has functions of transmitting control signals, status signals, data signals, and the like between the digital camera 200 and the photographing lens unit 100 and supplying various voltages. Further, it has a function of transmitting a signal to the system controller 223 when the photographing lens unit 100 is connected. As a result, communication can be performed between the digital camera 200 and the photographing lens unit 100, and the photographing lens 101 and the aperture 102 in the photographing lens unit 100 can be driven. The contact group 107 may be configured to transmit not only electrical communication but also optical communication, voice communication, and the like.

  In the present embodiment, for the sake of convenience, one photographic lens 101 is shown, but it is well known that the photographic lens 101 is actually composed of a larger number of lenses.

  The contact point group 107 and the system controller 223 constitute lens detection means.

  An imaging light beam from a subject image (not shown) is guided to a quick return mirror 202 that can rotate in the direction of an arrow shown in the drawing via the imaging lens 101 and the diaphragm 102. The central portion of the quick return mirror 202 is a half mirror, and a part of the light beam is transmitted when the quick return mirror 202 is lowered. The transmitted light beam is reflected downward by the sub mirror 203 installed on the quick return mirror 202.

  Reference numeral 204 denotes a known phase difference detection system composed of a field lens, a reflecting mirror, a secondary imaging lens, a diaphragm, a line sensor composed of a plurality of CCDs, and the like arranged in the vicinity of an imaging surface (not shown). AF sensor unit. In the AF sensor unit 204, a plurality of pairs of sensor rows 111a to 111n that are not unidirectional as shown in FIG. 2 are arranged, and seven distance measuring areas (seven pairs of sensor rows) are synonymous with focus detection areas. ) Is configured to allow focus detection. The focus detection circuit 205 controls the AF sensor unit 204 based on a control signal from the system controller 223, and performs focus detection by a known phase difference detection method.

  The AF sensor unit 204 and the focus detection circuit 205 constitute a phase difference detection type focus detection means.

  On the other hand, the photographing light beam reflected by the quick return mirror 202 reaches the eyes of the photographer through the pentaprism 201 and the eyepiece lens 206.

  Further, when the quick return mirror 202 is raised, the light beam from the photographing lens 101 passes through the focal plane shutter 208 as a mechanical shutter and the image sensor 210 represented by a CMOS or the like as an image sensor through a filter 209. It reaches.

  Although a solid-state image sensor such as a CCD or CMOS is used here, an image pickup tube such as a silver salt film or a vidicon may be used.

  The filter 209 has two functions. One is a function of cutting infrared rays and guiding only visible light to the image sensor 210, and the other is a function as an optical low-pass filter. The focal plane shutter 208 has a front curtain and a rear curtain, and controls transmission and blocking of a light beam from the photographing lens 101.

  The sub mirror 203 is folded when the quick return mirror 202 is up.

  The digital camera 200 according to the present embodiment is a control unit for the entire digital camera, and includes a system controller 223 (hereinafter also referred to as a CPU 223) that includes a CPU that controls the operation. Control.

  The system controller 223 corresponds to correction value calculation means and the like.

  The system controller 223 moves the photographing lens 101 in the optical axis direction to focus the lens control circuit 104 for controlling the lens driving mechanism 103 and the diaphragm driving mechanism 105 for driving the diaphragm 102. It is connected to the control circuit 106. Further, it is also connected to a shutter charge / mirror drive mechanism 211 that controls the up / down drive of the quick return mirror 202 and the shutter charge of the focal plane shutter 208. In addition, a shutter control circuit 212 for controlling the travel of the front curtain and rear curtain of the focal plane shutter 208 and a photometric circuit 207 connected to a photometric sensor (not shown) disposed in the vicinity of the eyepiece lens 206 are also connected. Has been. Further, a memory that stores parameters necessary to control the digital camera 200, camera ID information that enables individual identification of the digital camera, AF correction data adjusted by the reference lens, automatic exposure correction value, and the like is stored. It is also connected to an EEPROM 222 as a means.

  The lens control circuit 104 includes a lens storage device that stores lens-specific information, for example, information such as focal length, wide aperture, lens ID assigned to each lens, and information received from the sequence controller 223.

  The photometric sensor connected to the photometric circuit 207 is a sensor for measuring the luminance of the subject, and its output is supplied to the system controller 223 via the photometric circuit 207.

  The system controller 223 controls the lens driving mechanism 103 to form a subject image on the image sensor 210. Further, the system controller 223 controls the aperture driving mechanism 105 that drives the aperture 102 based on the set Av value, and further outputs a control signal to the shutter control circuit 212 based on the set Tv value. .

  The drive source of the front and rear curtains of the focal plane shutter 208 is constituted by a spring, and a spring charge is required for the next operation after the shutter travels. The shutter charge / mirror drive mechanism 211 controls the spring charge. Also, the quick return mirror 202 is raised and lowered by the shutter charge / mirror drive mechanism 211.

  An image data controller 220 is connected to the system controller 223. The image data controller 220 is configured by a DSP (digital signal processor), and executes control of the image sensor 210 and correction and processing of image data input from the image sensor 210 based on commands from the system controller 223. is there. Auto white balance is also included in the image data correction and processing items. Auto white balance is a function that corrects a portion of maximum brightness in a captured image to a predetermined color (white). In the auto white balance, the correction amount can be changed by a command from the system controller 223.

  Connected to the image data controller 220 is a timing pulse generation circuit 217 that outputs a pulse signal necessary for driving the image sensor 210. An A / D converter 216 for receiving the timing pulse generated by the timing pulse generation circuit 217 together with the image sensor 210 and converting an analog signal corresponding to the subject image output from the image sensor 210 into a digital signal is also connected. Yes. Further, a DRAM 221 for temporarily storing the obtained image data (digital data), a D / A converter 215 and an image compression circuit 219, an image rotation circuit 241, and a contrast detection circuit 242 are connected. .

  The image data controller 220, the image compression circuit 219, and the image data recording medium 218 constitute recording means.

  The DRAM 221 is used for temporarily storing image data before processing or data conversion into a predetermined format.

  The image rotation circuit 241 operates based on a command from the system controller 223, rotates the image data corrected by the image data controller 220 by an arbitrary angle, and stores the image data in the DRAM 221.

  The contrast detection circuit 242 operates based on a command from the system controller 223, detects the contrast in a predetermined direction of the image data corrected by the image data controller 220, and stores the contrast evaluation value in the EEPROM 222.

  An image display circuit 213 is connected to the D / A converter 215 via an encoder circuit 214. Further, an image data recording medium 18 is connected to the image compression circuit 219.

  The image display circuit 213 is a circuit for displaying image data picked up by the image sensor 210, and is generally composed of a color liquid crystal display element.

  The image data controller 220 converts the image data on the DRAM 221 into an analog signal by the D / A converter 215 and outputs the analog signal to the encoder circuit 214. The encoder circuit 214 converts the output of the D / A converter 215 into a video signal (for example, an NTSC signal) necessary for driving the image display circuit 213.

  The D / A converter 215, the image display circuit 213, and the encoder circuit 214 constitute image display means.

  The image compression circuit 219 is a circuit for performing compression and conversion (for example, JPEG) of image data stored in the DRAM 221. The converted image data is stored in the image data recording medium 218. As the image data recording medium, a hard disk, a flash memory, a floppy disk (registered trademark), or the like is used.

  The system controller 223 is connected to a display control circuit 225 that displays information on the operation mode of the digital camera 200, exposure information (shutter seconds, aperture value, etc.) on the external liquid crystal display device 250 and the internal liquid crystal display device 251. ing. A main electronic dial switch 226 and a determination switch 227 are connected. A distance measurement area selection button 228 (corresponding to distance measurement area selection means) for selecting a distance measurement area to be used from among a plurality of distance measurement areas of the AF sensor unit 204 is also connected. Further, a shooting mode selection button 229 for setting a mode in which the digital camera 200 should execute a desired operation by the user is connected. Also, a release SW1 (231) for starting a shooting preparation operation such as photometry and distance measurement, a release SW2 (230) for starting an imaging operation, an AF mode selection button 233, and a photometry mode selection button 235 are also provided. It is connected.

  The external liquid crystal display device 250 and the internal liquid crystal display device 251 correspond to display means, the external liquid crystal display device 250 corresponds to external display means, and the internal liquid crystal display device 251 corresponds to internal display means. Further, the display control circuit 225 and the system controller 223 constitute display control means.

  About the digital camera system comprised as mentioned above, the operation | movement flow in a present Example is demonstrated in detail using FIGS. 3-11.

  FIG. 3 is a flowchart showing the shooting mode switching operation in this embodiment. When the release SW1 (231) is turned on, the state of the shooting mode selection button 229 is read in step S101, and the read shooting mode is determined in step S102. As a result of the determination, the process proceeds to one of the “normal mode” in step S103 and the “calibration mode” in step S104.

  FIG. 4 is a flowchart showing the focus detection operation in the “normal mode”. In FIG. 4, in step S <b> 201, the result obtained by the phase difference detection type focus detection method is stored in the EEPROM 222.

  In step S202, the correction value of the focus detection result based on the phase difference corresponding to the currently mounted photographic lens 101 is read from the EEPROM 222. Here, the lens ID may be used to identify the photographic lens 101 that is mounted. In addition, when a photographing lens having no lens ID or a corresponding correction value is not found, the latest calibration result may be used as the correction value.

  In step S203, the focus detection result in step S201 is corrected using the correction value read in step S202, and in step S204, the photographing lens 101 is driven to the in-focus position based on the correction result.

  FIG. 5 is a flowchart showing the AF calibration operation in the “calibration mode”, which is controlled by the system controller 223. In FIG. 5, in step S301, a distance measurement area to be calibrated (referred to as a distance measurement point in FIG. 5 and later) is selected by a distance measurement area selection button 228, and the position corresponding to the selected distance measurement area is as shown in FIG. A simple reference chart 10 is installed. The reference chart 10 installed here is arranged so that its orientation is orthogonal to the corresponding line sensor in order to reduce errors in phase difference detection.

  In step S302, the focus detection by the phase difference detection method in the distance measurement area is performed, and the photographing lens 101 is driven to the focus position based on the focus detection result. The distance measurement frames 81a to 81g of each distance measurement area are as shown in FIG. 7, and the positional relationship with the contrast detection areas 82a to 82g is also as shown in FIG.

  In step S <b> 303, the position (defocus amount) of the taking lens 101 focused by the phase difference AF is stored in the EEPROM 222. At this time, it may be stored in pairs with a lens ID that is uniquely set for the taking lens 101.

  In step S304, in order to detect contrast near the current in-focus position, the photographic lens 101 is driven to be a predetermined amount of the front pin.

  In step S305, the photographing lens 101 is driven by a predetermined amount in the rear pin direction to perform imaging. Here, the photographing lens 101 may be driven to the rear pin side in step S304, and may be driven in the front pin direction in step S305. Further, the lens driving direction in step S305 may be changed according to the contrast evaluation value in step S309 described later.

  In step S306, image signals in the contrast detection areas 82a to 82g corresponding to the distance measurement areas shown in FIG.

  In step S307, it is determined whether or not the image needs to be rotated based on the direction of the line sensor corresponding to the distance measuring area selected in step S301. This determination is based on the assumption that the contrast detection circuit 242 capable of performing contrast detection in a predetermined direction is used, and determines whether or not the image can be detected in a direction with high contrast. To do. In step S301, since the user places the reference chart 10 in a direction orthogonal to the line sensor, it is possible to determine the direction in which the corresponding distance measurement area has a strong contrast.

  When it is determined in step S307 that it is necessary to rotate the image, the process proceeds to step S308, and the contrast detection circuit 242 uses the image rotation circuit 241 so that the contrast detection can be performed in the direction of strong contrast. The image is rotated as shown in FIG. For example, the contrast detection circuit 242 performs filtering on the image signal cut out in step S306 and extracts a high frequency component of about 1 MHz to 2.5 MHz. The contrast evaluation value can be obtained by integrating the maximum value of the luminance difference between adjacent pixels in the horizontal direction in the vertical direction. Using such a contrast detection circuit 242, calibration is performed using the distance measurement frames 81f (FIG. 7) corresponding to the sensor rows 111c and 111k (FIG. 2). In that case, contrast cannot be detected in the reference chart 10 arranged in the direction shown in FIG. 6 in step S301. Therefore, the image rotation circuit 241 rotates the image 90 degrees as shown in FIG. 9 to detect contrast.

  Here, the image rotation will be briefly described. Considering that coordinate transformation as shown in FIG. 10 is performed on all pixels in order to rotate the image, the coordinate position D after rotation when rotated by θ degrees is expressed by the following equations (1) and (2 ) Expression.

Dx = Zx + (Sx−Zx) cos θ− (Sy−Zy) sin θ (1)
Dy = Zy + (Sx−Zx) sin θ− (Sy−Zy) cos θ (2)
Next, a case where the rotated image is input to the contrast detection circuit 242 will be described. If the rotated image is maintained horizontally and vertically as shown in FIG. 11A, it can be input to the contrast detection circuit 242 as it is. However, when the rotated image cannot be maintained horizontally and vertically, the image area needs to be changed before being input to the contrast detection circuit 242. For example, as shown in FIG. 11B, a part is extracted from the rotated image, and the image is input to the contrast detection circuit 242. Further, as shown in FIG. 11C, the image size input to the contrast detection circuit 242 may be determined, and image rotation may be performed on an image in a larger area.

  After it is determined in step S307 that it is not necessary to rotate the image, or after the image is rotated in step S308, in step S309, the contrast detection circuit 242 performs contrast detection, and the evaluation result is obtained from the photographing lens 101. It is stored in the EEPROM 222 together with the position information.

  In step S <b> 310, a contrast peak is detected from the evaluation result stored in the EEPROM 222. When the contrast peak cannot be detected, the process proceeds to step S305, and the contrast evaluation is repeated a predetermined number of times until the contrast peak is detected.

  When the contrast peak is detected, the process proceeds to step S311 and the photographing lens 101 is driven to the peak position based on the contrast AF result.

  In step S <b> 312, a correction value for the phase difference AF is obtained from the difference between the position of the photographing lens 101 focused by detecting the phase difference and the position of the photographing lens 101 when focused by contrast AF, and stored in the EEPROM 222. . At this time, it may be stored in pairs with a lens ID that is uniquely set for the taking lens 101.

  In the first embodiment, it is possible to improve the accuracy of contrast evaluation by performing contrast detection in a direction with strong contrast. Further, the direction of the strong contrast is determined by an algorithm that can determine the direction of the strong contrast without actually detecting the contrast by making the direction of the line sensor and the direction of the reference chart 10 to be arranged orthogonal to each other. Speeding up is possible. In addition, in order to perform contrast detection in an arbitrary direction, an image input to the contrast detection circuit 242 is rotated, so that an existing safe contrast detection circuit 242 with a proven track record can be reused.

  In the first embodiment, the direction of the line sensor corresponding to the distance measurement area to be calibrated is orthogonal to the direction of the reference chart 10, and the direction of strong contrast in the reference chart 10 is determined from the direction of the line sensor. Yes. However, the means for determining the direction with strong contrast is not limited to this.

  Of course, the method of rotating the image is not limited to the algorithm in the first embodiment, and the image may be rotated by any method.

  Further, the means for correcting the image input to the contrast detection circuit 242 after the image rotation is not limited to the means in the first embodiment, and an input image to the contrast detection circuit 242 is generated by other means. It doesn't matter.

  In step S304, after the predetermined amount of the photographing lens 101 is driven to the front pin side, in step S305, while the photographing lens 101 is driven to the rear side of the predetermined amount, the contrast peak is searched. The means for obtaining the peak is not limited to the means of the first embodiment.

  Further, the image may be read out along the direction of strong contrast directly in the randomly accessible imaging device without rotating the image.

  Also, a contrast detection circuit capable of reading out corresponding to the direction of the line sensor provided may be prepared, and contrast detection in the direction of strong contrast may be performed.

  Further, when detecting the contrast in the diagonal direction, the contrast in the vertical and horizontal directions may be detected, and the contrast in the diagonal direction may be detected by combining the contrast detection results.

  In the first embodiment, the contrast detection method in the calibration has been described. However, the application example in which contrast detection is performed in accordance with the direction of strong contrast is not limited to this.

  The first embodiment is an application example to a single-lens reflex type digital camera system, but the application example of the present invention is not limited to a single-lens reflex type digital camera system.

  A contrast peak detection method in the hybrid AF mode according to the second embodiment will be described with reference to FIG. Since the configuration of the camera system in the second embodiment is the same as that in the first embodiment, description thereof is omitted here. The description of steps having the same reference numerals as those in the first embodiment is omitted.

  In step S302 'of FIG. 12, focus detection by a phase difference method that performs focus detection based on the phase difference between the output signals from the pair of sensor arrays is performed, and the photographing lens 101 is driven to the in-focus position.

  In step S301 ', the position of the ranging area selected in step 302' is stored in the memory (EEPROM 222).

  In step S307 'of FIG. 12, it is determined whether the contrast evaluation value stored in the EEPROM 222 in step S309 has reached a predetermined level. If the contrast evaluation value has reached a predetermined level, or if a predetermined number of contrast detection processes have been performed, the process proceeds to step S310. If it is determined that the contrast is weak and the contrast evaluation value has not reached the predetermined level, the process proceeds to step S308 '.

  In step S308 ', the image to be subjected to contrast detection is rotated by a predetermined amount. The amount of rotation may be determined based on the direction of the corresponding line sensor and / or the contrast evaluation value at the time of step S307 '. Alternatively, a predetermined amount such as 45 degrees or 90 degrees may be determined in advance.

  The contrast peak detecting means according to the second embodiment may not be the case where the reference chart 10 is arranged in a direction with strong contrast as in the first embodiment. In that case, it is possible to determine the direction of strong contrast based on the output signal from the image sensor (image sensor 210) and evaluate the contrast, and to realize highly accurate contrast peak detection.

  In the focus detection apparatus having multi-point distance measurement, even when a plurality of distance measurement areas are selected at the same time, a high-precision contrast peak can be obtained by applying the operation flow of the second embodiment to each distance measurement area. Detection can be performed.

  A contrast peak detection method according to the third embodiment will be described with reference to FIG. In addition, since the structure of the camera system in Example 3 is the same as Example 1, description here is abbreviate | omitted. Since the operation in the calibration is the same, the description of the steps having the same reference numerals as those in the first embodiment is omitted.

  In step S307 'of FIG. 13, it is determined whether or not the contrast evaluation value stored in the EEPROM 222 in step S309 has reached a predetermined level. If the contrast evaluation value has reached a predetermined level, or if a predetermined number of contrast detection processes have been performed, the process proceeds to step S310. If it is determined that the contrast is weak and the contrast evaluation value has not reached the predetermined level, the process proceeds to step S308 '.

  In step S308 ', the image to be subjected to contrast detection is rotated by a predetermined amount. The amount of rotation may be determined based on the direction of the corresponding line sensor and / or the contrast evaluation value at the time of step S307 '. Alternatively, a predetermined amount such as 45 degrees or 90 degrees may be determined in advance.

  With the means for obtaining the contrast peak in the third embodiment, it is not necessary to restrict the relationship between the orientation and type of the reference chart 10 and the distance measuring area to be selected, and calibration can be performed with easy settings. Is possible.

  The means for obtaining the contrast peak in the third embodiment is not limited to calibration.

  The auxiliary light projection method according to the fourth embodiment will be described with reference to FIG. The configuration of the camera system in the fourth embodiment is obtained by adding the auxiliary light driving unit 260 and the auxiliary light projecting unit 261 shown in FIG. 15 to the camera system of the first embodiment. The auxiliary light projected by the auxiliary light projecting means 261 is controlled by the system controller 223 sending a control signal to the auxiliary light driving means 260. Thereby, it is possible to control all or part of the pattern projection, the range of the projection area, and the light intensity. Since the other components of the fourth embodiment are the same as those of the first embodiment, description thereof is omitted here. In FIG. 14, the calibration operation is also the same, and therefore the description of the steps having the same reference numerals as those in the first embodiment is omitted.

  In step S314 in FIG. 14, it is possible to concentrate the light by projecting the auxiliary light only to the distance measurement area to be calibrated. Both can be realized. Further, by using pattern projection according to the direction of the line sensor corresponding to the distance measuring area to be calibrated, the auxiliary light to be projected can be calibrated with higher accuracy. For example, as shown in FIG. 16, when performing calibration of distance measuring areas corresponding to the sensor rows 111a and 111b, pattern projection is performed in an oblique direction that is orthogonal to the sensor rows 111a and 111b. Similarly, pattern light projection in the vertical direction is performed on the central sensor array 111n and sensor array 111g.

  Also, during normal shooting, light can be projected to cover the entire field of view, and the direction of the projected light can be matched to the direction of the line sensor and the direction of strong contrast, achieving high accuracy and energy saving. It is. The application example is not limited to calibration only.

  As described above, according to the fourth embodiment, it is possible to achieve high accuracy of focus detection by contrast detection.

  In addition, since a contrast detection circuit in a predetermined direction can be used to detect contrast in an arbitrary direction, a safe module can be reused, and the cost is excellent.

  In addition, since the direction in which the contrast evaluation is performed and the direction of the corresponding line sensor are matched, simple and high-speed line sensor direction contrast detection is possible.

  In addition, when performing contrast detection in an oblique direction, since it is obtained by combining vertical and horizontal contrast evaluation values, contrast detection in an oblique direction can be performed without performing complicated processing.

  Further, since the image signal is read directly from the image sensor (image sensor 210) along the detection direction, high-speed contrast detection is possible.

  Further, in the calibration mode, since the correction value is obtained by switching the contrast detection direction according to the direction of the line sensor in the corresponding distance measurement area, it is possible to obtain a highly accurate correction value.

  Further, since the auxiliary light is projected in the vicinity of the distance measurement area and in the direction of the line sensor, it is possible to achieve high accuracy and energy saving in the projection of the auxiliary light.

1 is a block diagram illustrating an example of an electrical configuration of a digital camera system that is Embodiment 1 of the present invention. FIG. 3 is a diagram illustrating an arrangement of line sensors in Embodiment 1. FIG. 6 is a flowchart illustrating a shooting mode selection operation according to the first exemplary embodiment. 3 is a flowchart illustrating an operation in a normal mode according to the first embodiment. 3 is a flowchart illustrating an operation in a calibration mode according to the first exemplary embodiment. It is a figure which shows the reference | standard chart in Example 1. 6 is a diagram illustrating a positional relationship between a distance measurement frame and a contrast detection area in Embodiment 1. FIG. It is a figure which shows the relationship between the image rotation in Example 1, and contrast detection. 6 is a diagram illustrating a relationship between a line sensor arrangement direction and a contrast detection direction in Embodiment 1. FIG. It is a figure which shows the coordinate transformation by the image rotation in Example 1. FIG. 6 is a diagram illustrating a relationship between a rotated image and an AF target image in Embodiment 1. FIG. 6 is a flowchart showing the operation of the second embodiment. 10 is a flowchart illustrating the operation of the third embodiment. 10 is a flowchart illustrating the operation of the fourth embodiment. It is a block diagram which shows the relationship between the auxiliary light projector in Example 4, and another part. It is a figure which shows the pattern light emission corresponding to the sensor row | line | column in Example 4. FIG.

Explanation of symbols

100 Shooting lens unit
DESCRIPTION OF SYMBOLS 101 Shooting lens 107 Electrical contact group 200 Digital camera 201 Penta prism 202 Quick return mirror 203 Sub mirror 204 AF sensor unit 206 Eyepiece lens 207 Photometry circuit 208 Focal plane shutter 209 Filter 210 Image sensor 211 Shutter charge mirror drive mechanism 212 Shutter control circuit 213 Image display circuit 214 Encoder circuit
215 D / A converter 216 A / D converter
217 Timing pulse generation circuit 219 Image compression circuit 220 Image data controller 221 DRAM
222 EEPROM
223 System controller 228 Distance measurement area selection button 229 Shooting mode selection button 241 Image rotation circuit 242 Contrast detection circuit 111a to 111n Sensor array 10 Reference chart 81a to 81g Distance measurement frame 82a to 82g Contrast detection area 260 Auxiliary light driving means 261 Auxiliary light Projection means

Claims (6)

A first focus detection unit that has a plurality of selectable focus detection areas and detects a focus state based on a phase difference of image signals from a pair of sensor rows corresponding to the selected focus detection area ;
Contrast detection means for detecting the contrast in a predetermined direction of the image in the contrast detection area corresponding to the sensor array pair among the images read out from the imaging sensor is provided, and the focus state is determined based on the detection result by the contrast detection means. an imaging apparatus which have a second focus detection means for detecting,
When the second focus detection unit detects the focus state, the contrast detection direction by the contrast detection unit is switched according to the selected focus detection area, thereby arranging the sensor row pair corresponding to the focus detection area. imaging apparatus characterized by the contrast detection direction corresponds to. Wherein by rotating the image of the contrast detection area, the image pickup apparatus according to claim 1, characterized in that the switchable contrast detection direction by the contrast detection unit. The imaging sensor is a randomly accessible sensor,
The imaging apparatus according to claim 1, wherein a direction in which an image is read out from the imaging sensor can be switched in accordance with a selected focus detection area . The imaging apparatus according to claim 1 , wherein a direction in which an image signal read from the imaging sensor is input to the contrast detection unit can be switched in accordance with a selected focus detection area . The first focus detection unit further includes an auxiliary light projecting unit for projecting the auxiliary light, and determines the direction of the auxiliary light projected by the auxiliary light projecting unit according to the selected focus detection area. the imaging apparatus according to any one of claims 1 to 4, characterized in that it is switchable. First focus detection means for detecting a focus state based on a phase difference of image signals from a pair of sensor rows corresponding to a focus detection area;
Contrast detection means for detecting the contrast in a predetermined direction of the image in the contrast detection area corresponding to the sensor array pair among the images read out from the imaging sensor is provided, and the focus state is determined based on the detection result by the contrast detection means. An imaging device having second focus detection means for detecting,
As a shooting mode, a first mode for performing normal shooting and a second mode for obtaining a correction amount of the focus detection result based on the focus detection results of the first focus detection unit and the second detection unit, respectively. With mode,
By switching the contrast detection direction by the contrast detection means according to the switching to the second mode, the arrangement direction of the sensor array pair corresponding to the focus detection area corresponds to the contrast detection direction. Imaging device.

Images