JP2019128549A - Focus detector and optical apparatus equipped with focus detector - Google Patents

Abstract

To provide a focus detector with which it is possible to prevent a reduction in the accuracy of focus detection due to ghost light, and an optical apparatus equipped with the focus detector.SOLUTION: In a focus detector 207, a distance measuring beam of light from an external focus lens 101 is divided into four by a porous diaphragm 302 and formed as four subject images by a secondary image-forming lens unit 303, and an in-focus state of the focus lens 101 is detected by a control unit from the relative physical relationship of luminous energy distribution of each of the subject images that is photoelectrically converted by a focus detection sensor 400. The focus detection sensor 400 is provided with image-forming regions 401A-D within an image field range determined by a visual field mask 300 and ghost detection regions 402A-D in the periphery of the foregoing. The beam of light entering the focus detection sensor 400 is limited stepwise using an external diaphragm 105 until the occurrence of ghost light is no longer detected from the output obtained from the ghost detection regions 402A-D.SELECTED DRAWING: Figure 15

Description

  The present invention relates to a focus detection apparatus and an optical apparatus including the focus detection apparatus, and more particularly to a focus detection apparatus capable of automatic focus detection and an optical apparatus including the focus detection apparatus.

  In single-lens reflex cameras, focus detection using a phase difference detection method that detects the focus state (defocus value) of a shooting optical system from the phase difference of a plurality of image signals formed by light passing through the shooting optical system in an interchangeable lens. Devices are often mounted. A focus detection sensor and a secondary imaging optical system dedicated to phase difference detection for forming an object image on the focus detection sensor are provided inside the focus detection apparatus using such a phase difference detection method. For this reason, unnecessary light (hereinafter referred to as “ghost light”) generated by reflection or the like by a structure included in the focus detection apparatus enters the focus detection sensor via the secondary imaging optical system. There is a problem that the detection accuracy is lowered.

  For example, in Patent Document 1, when the position of the photographing light source is detected from the subject image obtained by the focus detection device, a ghost corresponding to the position of the detected photographing light source and the position of the photographing light source stored in advance in the storage means A technique for correcting ghost light based on light information is disclosed. Further, in Patent Document 2, the occurrence of ghost light is predicted from the luminance information in the subject image obtained by the imaging device, and the ghost light is corrected with the information generated based on the predicted generation mode of the ghost light. Technology is disclosed.

JP, 2006-184321, A JP, 2006-129084, A

  However, in the prior art disclosed in the above-mentioned Patent Documents 1 and 2, it is necessary to grasp in advance the position and intensity of ghost light generated according to the position of the photographing light source and the luminance information in the object image. On the other hand, since the position and intensity of the ghost light also change depending on the distance to the photographing lens and the subject, it is necessary to grasp for each photographing lens to be used and the subject distance. In addition, since a high brightness subject does not always generate ghost light, it is necessary to accurately predict the generation of ghost light for all high brightness bodies in the subject image. Therefore, much time is spent on analysis and processing of the subject image. Furthermore, since ghost light may exist outside the area where the subject image of the imaging device or focus detection sensor is formed, in such a case, the ghost light is used in the prior art disclosed in the above-mentioned Patent Documents 1 and 2. Is difficult to correct.

  In view of the circumstances, an object of the present invention is to provide a focus detection device and an optical apparatus including the focus detection device that can prevent a decrease in focus detection accuracy due to ghost light.

  According to a first aspect of the present invention, a focus detection apparatus according to the present invention divides a distance measurement light beam from a focus lens in the outside into a plurality of regions, and forms each of the divided distance measurement light beams as a plurality of object images. A sensor having a secondary imaging lens, and a photoelectric conversion unit for photoelectrically converting the light quantity distribution of each of the plurality of subject images; determining means for determining an image field to be formed on the sensor; It is a focus detection device which has a control part which detects a focusing state of said focus lens from relative physical relationship of light volume distribution, and said sensor is in the range of said image field of vision determined by said determination means A first sensor region, a second sensor region around the first sensor region, a detection means for detecting generation of ghost light from an output obtained from the second sensor region, and the detection hand Characterized in that it comprises a limiting means for the generation of the ghost light is stepwise limit the light beam incident on the sensor until no detected by.

  An optical apparatus according to a fourth aspect of the present invention includes the focus detection device, the focus lens, and a diaphragm for adjusting a light flux transmitted through the focus lens, and the diaphragm is controlled by the restriction unit to control the sensor It is characterized in that the light beam incident on the beam is limited step by step.

  According to the present invention, it is possible to prevent a decrease in focus detection accuracy due to ghost light.

FIG. 1 is a block diagram showing a schematic configuration of an imaging apparatus as an optical apparatus provided with a focus detection device according to a first embodiment. It is a schematic sectional drawing of the focus detection apparatus in FIG. It is a top view of the visual field mask in FIG. FIG. 3 is a plan view of the porous stop in FIG. 2; It is the figure which looked at the secondary imaging lens unit in FIG. 2 from the focus detection sensor side. It is the figure which looked at the focus detection sensor from the secondary imaging lens unit side. It is a conceptual diagram which shows the ranging light beam of a focus detection sensor. It is a figure of a photographic subject for explaining ranging operation of an imaging device. It is a figure which shows the to-be-photographed image imaged on a focus detection sensor. It is a figure which shows the sensor output waveform of each focus detection line in FIG. It is the schematic which shows the optical path which the light ray which makes a focus detection sensor produce ghost light injects. It is a figure which shows the positional relationship of each ghost light which arises on a focus detection sensor. It is a figure which shows the sensor output waveform of the focus detection line in FIG. 12, and a ghost detection line. 6 is a flowchart illustrating a procedure of focus adjustment processing according to the first embodiment. FIG. 13 is a schematic diagram illustrating an optical path of a light beam that has passed outside the pupil of the photographing lens when the diaphragm is driven from the state of FIG. 11 until each ghost light of FIG. 12 is not generated.

  Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the following embodiments. In addition, the embodiments of the present invention show preferred embodiments of the present invention and do not limit the scope of the present invention.

Example 1
FIG. 1 is a block diagram showing a schematic configuration of an image pickup apparatus as an optical apparatus provided with a focus detection apparatus according to a first embodiment.

  An imaging apparatus 200 according to the first embodiment is a single-lens reflex camera, and as illustrated in FIG. 1, a photographing lens 100 is detachably attached via a lens mounting mechanism of a mount unit (not shown). An electrical contact unit 104 is provided in the mount portion. The imaging device 200 communicates with the photographing lens 100 via the electric contact unit 104, and controls the focus lens 101 in the photographing lens 100. In FIG. 1, only the focus lens 101 is shown as the lens in the photographing lens 100, but a variable power lens or a fixed lens may be provided in addition to this.

  A light beam from a subject (not shown) is guided to a main mirror 201 in the imaging apparatus 200 via a photographing optical system (including a focus lens 101) in the photographing lens 100. The main mirror 201 is disposed obliquely with respect to the photographing optical axis OA, and a first position (illustrated position) for guiding the light beam from the subject to the upper viewfinder optical system and a second position for retracting outside the photographing optical path OA. It is possible to move to the position of.

  The central portion of the main mirror 201 is a half mirror, and when the main mirror 201 is at the first position, a part of the light flux from the subject passes through the central portion of the main mirror 201 which is a half mirror. Then, the transmitted light beam is reflected by the sub mirror 202 provided on the back side of the main mirror 201, and is guided to the focus detection device 207 (focus detection means) on the photographing optical axis OA 'as a distance measurement light beam. The detailed configuration of the focus detection device 207 will be described later.

  On the other hand, when the main mirror 201 is at the first position, the light beam from the subject reflected by the main mirror 201 forms an image on the focus plate 203 disposed at a position optically conjugate with the image sensor 209. . The light (object image) transmitted after being imaged by the focusing plate 203 is converted into an erect image by the penta-dach prism 204. The erect image is magnified by the eyepiece 205 and can be viewed by the photographer.

  When the main mirror 201 is in the second position, the sub mirror 202 is also folded with respect to the main mirror 201 and retracted from the photographing optical axis OA. The luminous flux transmitted through the photographing optical system of the photographing lens 100 passes through a focal plane shutter 208 which is a mechanical shutter and reaches the image pickup element 209. The focal plane shutter 208 limits the amount of light incident on the imaging device 209. The imaging element 209 is configured by a photoelectric conversion element such as a CCD sensor or a CMOS sensor that photoelectrically converts an object image formed by the photographing lens 100 to generate an image and outputs an electrical signal.

  The camera control unit 210 is a controller (control unit) that controls various calculations and various operations in the imaging device 200, and is configured of a CPU, an MPU, and the like. Also, the camera control unit 210 communicates with the lens control unit 103 in the photographing lens 100 via the electrical contact unit 104.

  The lens control unit 103 controls the lens driving mechanism 102 that performs focusing by driving the focus lens 101 in the optical axis direction in accordance with a signal from the camera control unit 210. The lens driving mechanism 102 has a stepping motor or an ultrasonic motor as a driving source. Further, the lens control unit 103 controls the diaphragm drive mechanism 106 that drives the diaphragm 105 for adjusting the light beam transmitted through the photographing lens 100 in accordance with a signal from the camera control unit 210. The aperture drive mechanism 106 has a stepping motor or the like as a drive source.

  An EEPROM 211, which is a storage device, is connected to the camera control unit 210. In the EEPROM 211, parameters that need to be adjusted to control the imaging apparatus 200, camera ID (identification) information for performing individual identification of the imaging apparatus 200, and parameters related to imaging that have been adjusted in advance using a reference lens are stored. Factory adjustment values etc. are stored.

  The display unit 212 is a device that displays image data captured by the image sensor 209, items set by the photographer, and the like, and is generally configured using a color liquid crystal display element.

  Furthermore, the camera control unit 210 is connected to an operation detection unit 213 that detects an operation on the imaging device 200 by the photographer. The operation detection unit 213 detects an operation of the photographer with respect to operation members such as a release button (not shown) and a focusing operation start button. Also, settings relating to imaging are performed via the operation member, and the settings are stored in the EEPROM 211.

  On the other hand, the lens control unit 103 of the photographing lens 100 stores performance information such as the focal length and the aperture value of the photographing lens 100, and lens ID (identification) information which is unique information for identifying the photographing lens 100. A storage device (not shown) is provided. The storage device also stores information received from the camera control unit 210 through communication. The performance information and the lens ID information are transmitted from the lens control unit 103 to the camera control unit 210 through initial communication performed when the imaging lens 100 is attached to the imaging device 200, and the camera control unit 210 stores these in the EEPROM 211. Let

  The imaging device 200 may be a mirrorless camera. In this case, the main mirror 201, the focusing plate 203, the penta-dach prism 204, and the eyepiece lens 205 are removed from the imaging device 200. Further, the sub mirror 202 moves to the position shown in FIG. 1 only in the AF (automatic focus detection) mode, and retracts outside the photographing optical path OA in the other modes.

  The configuration of the focus detection device 207 according to the first embodiment will be described with reference to FIGS.

  FIG. 2 is a schematic sectional view of the focus detection apparatus 207 in FIG. Although not shown, at the left end of FIG. 2, there is a primary imaging plane P (scheduled imaging plane of the taking lens 100) conjugate with the image sensor 209. That is, in the focus detection device 207, the visual field mask 300, the field lens 301, the aperture stop 302, the secondary imaging lens unit 303, and the focus detection sensor 400 are disposed in order from the primary imaging plane P.

  FIG. 3 is a plan view of the field mask 300, and FIG. 4 is a plan view of the multi-aperture stop 302. Both are views seen from the primary imaging plane P side.

  5 is a view of the secondary imaging lens unit 303 viewed from the focus detection sensor 400 side, and FIG. 6 is a view of the focus detection sensor 400 viewed from the secondary imaging lens unit 303 side.

  The field mask 300 is a thin plate-like part, and an opening 300A is provided at the center. The shape of the aperture 300 A determines the image field to be imaged on the focus detection sensor 400.

  The field lens 301 is a convex lens and is provided in the vicinity of the field mask 300. The field lens 301 has a role of forming an image of the aperture stop 302 in the vicinity of the exit pupil of the photographing lens 100.

  The porous stop 302 is a thin plate-like part, and openings 302A to 302D are provided at four places. The openings 302A to 302D divide the distance measuring light beam that enters through the field lens 301 and is from the focus lens 101 outside the focus detection device 207 (dividing unit). In the present embodiment, the aperture 302A and the aperture 302B divide the distance measurement light beam in the Y direction, and the aperture 302C and the aperture 302D divide in the X direction.

  The secondary imaging lens unit 303 is a substantially plate-like component, and a surface facing the focus detection sensor 400 has a plurality of convex lens shapes as shown in FIG. These convex lens shapes are respectively referred to as secondary imaging lenses 303A-D. In the first embodiment, four secondary imaging lenses 303 </ b> A to 303 </ b> D are arranged so as to correspond to the openings 302 </ b> A to 302 </ b> D of the porous diaphragm 302. The secondary imaging lenses 303 </ b> A to 303 </ b> D re-image the subject image on the primary imaging plane P formed by the photographing lens 100 on the focus detection sensor 400. The distance measuring light beam that has passed through the aperture 302A of the aperture stop 302 is focused on the focus detection sensor 400 as a subject image by the secondary imaging lens 303A. Similarly, the distance measuring light beams that have passed through the openings 302 </ b> B to 302 </ b> D of the porous diaphragm 302 are imaged on the focus detection sensor 400 by the secondary imaging lenses 303 </ b> B to 303 </ b> D.

  The focus detection sensor 400 photoelectrically converts the subject image formed by the secondary imaging lenses 303A to 303D for each pixel, generates an image, and outputs an electrical signal (photoelectric conversion unit). The focus detection sensor 400 includes a photoelectric conversion element such as a CCD sensor or a CMOS sensor, and the photoelectric conversion elements (pixels) are arranged in a two-dimensional array. In the first embodiment, the pixels of the focus detection sensor 400 are disposed in a range wider than the range in which the subject image is formed. Specifically, the pixels of the focus detection sensor 400 are formed around the imaging regions (first sensor regions) 401A to 401D in the range where the subject image is formed by the visual field mask 300 and the periphery of the imaging regions 401A to 401D. It is arranged in a certain ghost detection area (second sensor area) 402A-D. The imaging area 401A and the ghost detection area 402A are configured by the same sensor array. The same applies to the imaging regions 401B to 401D and the ghost detection regions 402B to 402D. The light beam that has passed through the aperture 302A of the aperture stop 302 is imaged in the range of the imaging region 401A of the focus detection sensor 400 by the secondary imaging lens 303A. Similarly, the imaging regions 401B-D correspond to the apertures 302B-D of the aperture stop 302 and the secondary imaging lenses 303B-D.

  The pixel configuration of the focus detection sensor 400 is not limited to the configuration of the first embodiment as long as the ghost detection region 402 is provided around the imaging region 401. For example, a plurality of line sensors may be combined and disposed.

  FIG. 7 is a conceptual view showing a distance measurement luminous flux of the focus detection sensor 400. As shown in FIG. A distance measuring beam LA from the subject OBJ passes through the pupil EPA of the photographing lens 100 and forms an image on the primary imaging plane P. Thereafter, the secondary imaging lens 303A re-forms an image in the range of the imaging region 401A of the focus detection sensor 400. Similarly, the distance measurement light beams LB to D pass through the pupils EPB to EPD of the photographing lens 100 and form an image on the primary imaging plane P. After that, the secondary imaging lenses 303 </ b> B to D re-form images in the range of the imaging regions 401 </ b> B to D of the focus detection sensor 400.

  A single-lens reflex camera such as the imaging device 200 can mount an interchangeable lens having imaging optical systems of various focal lengths and open f-numbers as the imaging lens 100. Therefore, the focus detection sensor 400 is configured to correspond to an interchangeable lens (for example, F5.6) having a large open F value so that focus detection can be performed with all the interchangeable lenses for the imaging apparatus 200. Also in the first embodiment, the distance measurement light beams LA to D used by the focus detection sensor 400 for focus detection are configured to be F5.6 light beams. As shown in FIG. 7, the default setting of the aperture value of the aperture 105 of the taking lens 100 is F1.4 which is an open F value, and the F1.4 light beam is configured to pass through. Therefore, the pupils EPA to D through which the distance measurement luminous fluxes LA to D pass are accommodated inside the F5.6 luminous flux.

  In the focus detection apparatus 207 according to the first embodiment, the control unit (not shown) calculates the defocus value, that is, detects the in-focus state of the focus lens 101 by a known focus detection method based on secondary imaging phase difference detection. Detection). The focus detection principle and focus adjustment operation will be described with reference to FIGS. 8 to 10, taking as an example a case where focus detection is performed to shoot a subject using the imaging device 200 and the imaging lens 100.

  FIG. 8 is a diagram of a subject for explaining the distance measuring operation of the imaging device 200, and shows a subject photographed by the imaging device 200 to which the photographing lens 100 is attached. The shooting range is a range indicated by a solid line in FIG. 8, and the focus detection ranges 500 and 500 'are ranges (so-called AF distance measuring points) selected by the photographer as focus detection targets. Further, a range 300B indicated by a broken line indicates a field range defined by the opening 300A of the field mask 300, and an object image is formed on the focus detection sensor 400 in a range defined by the range 300B.

  FIG. 9 is a view showing a subject image formed on the focus detection sensor 400. As shown in FIG. The subject image in the range 300B defined by the aperture 300A of the visual field mask 300 is divided into four images by the apertures 302A to 302D of the aperture stop 302 and the secondary imaging lenses 303A to 303D. As a result, subject images are formed on the imaging regions 401A to 401D on the focus detection sensor 400 as shown in FIG.

  When the photographer operates the operation member of the imaging apparatus 200 to instruct the start of the focus detection operation to the location in the focus detection range 500 in FIG. 8, focus detection, that is, calculation of the defocus value is started. Specifically, the relative positional relationship with respect to the direction in which the image is divided by the apertures 302A to 302D of the aperture stop 302 and the secondary imaging lenses 303A to 303D (hereinafter referred to as "correlation direction") is examined. The defocus value is calculated from

  Hereinafter, the pixels at positions corresponding to the selected focus detection range 500 in the imaging regions 401A to D in FIG. 9 are referred to as focus detection lines 401A-1, 401B-1, 401C-1, and 401D-1, respectively. Do. The focus detection lines 401A-1, 401B-1, 401C-1, and 401D-1 are arranged in the same direction as the correlation direction. The focus detection line 401A-1 and focus detection line 401B-1 are in the Y direction, and the focus detection line 401C-1 and focus detection line 401D-1 are in the X direction.

  FIG. 10 is a diagram showing sensor output waveforms at each of the focus detection lines 401A-1, 401B-1, 401C-1, and 401D-1 in FIG. The horizontal axis of the graph of FIG. 10 is the position of the pixel, which is arranged in the order indicated by the arrow in FIG. The vertical axis represents the amount of light.

  A waveform indicated by a solid line in FIG. 10 is a sensor output waveform in a state where there is no focus shift and the defocus value is zero, and a waveform indicated by a broken line is a sensor output waveform in a state where the focus is shifted. This is because, when the focal position of the image on the primary imaging plane P is shifted, the images formed on the focus detection sensor 400 divided into pupils move in opposite directions in the correlation direction.

  The two sensor output waveforms indicated by the broken lines in FIGS. 10A and 10B that are output when the focus is deviated can be matched if they are moved by a predetermined number of pixels. Similarly, the two sensor output waveforms indicated by the broken lines in FIGS. 10C and 10D that are output when the focus is deviated can be matched if they are moved by a predetermined number of pixels.

  This calculation of the predetermined number of pixels is called correlation calculation. In general, the correlation calculation treats a common area (sum set, product set) of two sensor output waveforms as a correlation amount, and calculates a predetermined number of pixels that minimizes the correlation amount. Also, if the characteristics of the optical system of the focus detection device 207 are known, the calculated predetermined number of pixels can be converted into the amount of movement of the primary imaging plane P, that is, the defocus value. The method of correlation calculation is not limited to this example, and for example, a non-common area (corresponding to exclusive OR) of two sensor output waveforms may be used as the amount of correlation.

  The correlation calculation result using the sensor output waveform (FIGS. 10A and 10B) with the correlation direction in the Y direction and the sensor output waveform with the correlation direction in the X direction (FIGS. 10C and 10D) are used. Whether the defocus value is determined based on which of the correlation calculation results is determined depends on the waveform reliability determination. The reliability determination of the sensor output waveform is a known technique, and a defocus value calculated using the sensor output waveform determined to be more reliable is employed. In the example of FIG. 10, the X direction is the correlation direction, and the sensor output waveforms shown in FIGS. 10C and 10D are shown in FIGS. 10A and 10B where the Y direction is the correlation direction. The sensor output waveform is determined to have high waveform reliability because the peak position and the inflection point of the waveform are clear. Therefore, the defocus value calculated using the sensor output waveform which makes Y direction a correlation direction is adopted here.

  As described above, the example in which the correlation calculation is performed using the obtained sensor output waveform as it is has been described in the first embodiment, but the present invention is not limited to this example. For example, after performing filter processing that makes it less susceptible to signal intensity level differences from focus detection lines in the same correlation direction, or filter processing that amplifies or attenuates specific frequency components, the correlation operation is performed. Also good.

  If the defocus value is obtained, the focus lens 101 of the photographing lens 100 is driven to make the defocus value zero based on the defocus value, thereby completing the focusing of the subject image. Note that the process of determining the reliability is not usually recognized by the photographer, and is automatically processed by the imaging device 200 and its camera control unit 210.

  The cause of the generation of ghost light and the influence thereof in the focus detection device 207 will be described with reference to FIGS. The ghost light is a light beam that is defined by the field mask 300 and is incident on the focus detection sensor 400 through an optical path different from the distance measurement light beams LA to D imaged on the focus detection sensor 400. In FIG. 2, only the main components of the focus detection device 207 are shown and the structure thereof has been described. However, in actuality, it becomes a reflection source such as a reflection mirror for bending the optical system of the focus detection device 207 and a member for holding the components. It contains many possible members.

  FIG. 11 is a schematic view showing a light path on which a light beam 403 which causes the focus detection sensor 400 to generate ghost light is incident. The distance measuring beams LA to B are actually reflected by the sub-mirror 202 and the optical path is bent, but the drawing is simplified here.

  Ranging beams LA to B from a subject OBJ (not shown) pass through the pupils EPA to EPA B of the photographing lens 100 and form a subject image on the primary imaging plane P. Thereafter, the subject image is re-imaged on the focus detection sensor 400 via the field mask 300, the field lens 301, the porous aperture 302 (not shown in FIG. 11), and the secondary imaging lens unit 303.

  On the other hand, the light beam 403 that has passed outside the pupil of the photographic lens 100 is not blocked by the aperture 105 or the field mask 300 set to the open F value (F1.4), which is the default setting, and is not blocked by the inside of the focus detection device 207. And are reflected by the internal structure 600. Thereafter, the reflected light beam 403 enters the focus detection sensor 400 via the multi-aperture stop 302 and the secondary imaging lens unit 303. For this reason, on the focus detection sensor 400, ghost light 403A to 403A shown in FIG. 12 to be described later at four incident positions of the light beam 403 corresponding to the apertures 302A to D of the aperture stop 302 and the secondary imaging lenses 303A to 303D. D is generated.

  FIG. 12 is a diagram showing the positional relationship of each of the ghost lights 403A to 403D generated on the focus detection sensor 400. As shown in FIG. In the first embodiment, among these ghost lights 403A to 403D, the ghost lights 403A, 403B, and 403C are incident on the ghost detection area 402C, and the ghost light 403D is incident on the imaging area 401A.

  In this situation, when the photographer sets the focus detection range 500 'shown in FIG. 8, the focus detection lines 401A-2 and 401B-2 are provided at corresponding positions in the imaging regions 401A and 401B. In addition, ghost detection lines 402C-1 to 402C-3 are provided at positions corresponding to the ghost lights 403A to 403C.

  FIG. 13 is a diagram illustrating sensor output waveforms of the focus detection lines 401A-2 and 401B-2 and the ghost detection lines 402C-1 to 402C-3 in FIG. Since ghost light is not incident on the focus detection line 401B-2 as shown in FIG. 12, the sensor output waveform at the focus detection line 401B-2 shown in FIG. 13B is the light intensity distribution of the object image. In addition, as shown in FIG. 12, since no subject image is formed on the ghost detection lines 402C-1 to 402C-3, the sensor output waveforms on the ghost detection lines 402C-1 to 402C-3 shown in FIG. A light quantity distribution of ~ C. The ghost lights 403 </ b> A to 403 </ b> D have almost the same intensity because the members that are transmitted from the internal structure 600 reflected by the light beam 403 to the focus detection sensor 400 are the same.

  On the other hand, since the ghost light 403D is incident on the subject image on the focus detection line 401A-2 as shown in FIG. 12, the sensor output waveform in the focus detection line 401A-2 shown in FIG. It does not become accurate light quantity distribution of the image. Therefore, if the correlation calculation is performed based on the two sensor output waveforms of the focus detection lines 401A-2 and 401B-2, an accurate defocus value cannot be obtained, and the subject image cannot be focused with high accuracy. .

  Therefore, in the present invention, in order to prevent erroneous distance measurement due to the ghost light 403D, ghost detection regions 402A to 402D are provided around the imaging regions 401A to D of the focus detection sensor 400. Areas other than the imaging areas 401A to 401D of the focus detection sensor 400 are areas where light rays do not enter unless ghost light is generated. Therefore, when light rays are incident on the ghost detection areas 402A to 402D, it can be determined that there is a possibility that ghost light is incident somewhere in the imaging area 401.

  In the first embodiment, ghost light is generated in the focus detection range 500 ′ by the light ray 403 being reflected by the internal structure 600, but this is an example and the present invention is not limited to this condition. In particular, when the position of the light source at the time of photographing changes, the angle of the light beam emitted from the photographing lens 100 changes, so that the light beam 403 from outside the pupil does not hit the internal structure 600 and ghost light is not generated. That is, ghost light does not necessarily occur in the focus detection range 500 '. That is, even in the same focus detection range, ghost light may or may not be generated depending on various conditions such as the position of the light source at the time of photographing and the internal configuration of the photographing lens 100.

  Hereinafter, the procedure of the focusing process in the present invention will be described with reference to FIGS. The focus adjustment process may be performed by the camera control unit 210 or may be performed by the control unit included in the focus detection apparatus 207.

  FIG. 14 is a flowchart illustrating the procedure of the focus adjustment process according to the first embodiment.

  In step S701, a ranging operation is started. This is performed by the photographer operating a specific button of the imaging apparatus 200 and the operation detection unit 213 detecting the operation. In the present embodiment, the operation detection unit 213 detects the setting operation of the focus detection range 500 ′ by the photographer.

  In step S702, the open F-number of the photographing lens 100 is set to a variable FNo that is an aperture value of the aperture 105. In the present embodiment, 1.4 is set as the value of the variable FNo.

  In step S703, the light amounts of the ghost detection areas 402A to 402D are accumulated, and the output is acquired.

  In step S704, generation of ghost light is detected from the output of the ghost detection areas 402A to 402D acquired in step S703. As described above, since the ghost detection areas 402A to 402D are areas where light rays do not enter unless ghost light is generated, when an output is obtained from any of the ghost detection areas 402A to 402D, ghost light The occurrence is detected, and the process proceeds to step S705. At this time, ghost detection lines (ghost detection lines 402C-1 to 402C-3 in the example of FIG. 12) are provided at positions corresponding to the generated ghost lights (ghost lights 403A to C in the example of FIG. 12). On the other hand, when the output can not be obtained, the generation of ghost light is not detected, so the process proceeds to step S709.

  In step S705, it is determined whether the variable FNo is less than F5.6. If it is less than F5.6, the process proceeds to step S706. As described above, in the first embodiment, the distance measurement light beams LA to D used by the focus detection sensor 400 for focus detection are configured to be F5.6 light beams. That is, if the aperture value of the aperture 105 is set to F5.6 or more, which is an F value that defines the size of the distance measuring beams LA to D, vignetting occurs in the distance measuring beams LA to D, and highly accurate distance measurement is possible. It may not be possible. Therefore, the aperture value of the aperture 105 is not set to be F5.6 or more.

  In step S706, the diaphragm 105 is driven by one stage. Here, the diaphragm 105 is driven for each stage, but the number of stages is not limited as long as the diaphragm 105 is driven in stages to limit the light beam incident on the focus detection sensor 400 in stages.

  In step S707, the variable FNo is counted up by one step, and the process returns to step S703 to detect ghost light in a state in which the photographing lens 100 is reduced by one step from the previous time.

  Hereinafter, steps S703 to S707 will be specifically described with reference to FIG.

  FIG. 15 is a schematic diagram showing the optical path of the light beam 403 that has passed outside the pupil of the taking lens 100 when the diaphragm 105 is driven from the state of FIG. 11 until the ghost lights 403A to 403D of FIG.

  In FIG. 11, the light beam 403 which has passed through the outside of the pupil of the photographing lens 100 is incident on the focus detection sensor 400 to generate ghost lights 403A to D shown in FIG. 12. In such a situation, the generation of ghost light is detected in step S704. The initial value of the aperture 105 of the photographing lens 100 is an open F value (F1.4), which is less than F5.6, which is an F value that defines the size of the ranging light beams LA to D used for focus detection (step). YES in step S705), the process proceeds to step S706. Thereafter, each time the diaphragm 105 is gradually reduced (steps S706 and S707), it is confirmed whether or not the output from the ghost detection regions 402A to 402D can be obtained, that is, whether the generation of ghost light is not detected (step S703). , S704). In step S703, after the ghost detection line is set, whether or not ghost light is generated is determined from the output of the set ghost detection line. In the first embodiment, as shown in FIG. 15, when the aperture value of the aperture 105 is reduced to F4.0 (three steps from the open F value), the light beam 403 is blocked by the aperture 105, and the ghost of the focus detection sensor 400 is detected. The light does not enter the detection lines 402C-1 to 402C-3. That is, steps S703 to S707 are repeated three times, and the generation of ghost light is not detected in the fourth step S704. In this case, the process proceeds to step S709.

  Returning to FIG. 14, on the other hand, if the generation of ghost light is detected even when the aperture value of the aperture 105 is reduced to F5.6 (Yes in step S704 and NO in step S705), erroneous measurement will result if the aperture 105 is further reduced. The possibility of distance increases. In this case, the process proceeds to step S 708, and a distance measurement NG message indicating that the distance measurement can not be performed according to the current setting of the photographer (the position of the focus detection range 500 ′) is displayed on the display unit 212 (notification means ), This process is terminated.

  In step S709, in response to the fact that generation of ghost light is no longer detected in step S704, the amount of light in the imaging region 401 is accumulated and an output is obtained. More specifically, the sensor output waveforms at the focus detection lines 401A-2 and 401B-2 provided at corresponding positions in the imaging regions 401A and B of the focus detection range 500 'selected at step S701 are acquired. .

  In step S710, correlation calculation is performed from the output of the imaging region 401 acquired in step S709, more specifically, the sensor output waveform acquired in step S709, to calculate a defocus value.

  In step S711, the focus lens 101 is driven based on the defocus value calculated in step S710, and after the focusing of the subject image is completed, the present process ends.

  As described above, in the configuration of the first embodiment, ghost light is detected from the output of the ghost detection region 402 where no light beam enters unless ghost light is generated. As a result, ghost light can be accurately detected without being affected by the subject image. Further, by narrowing the diaphragm 105 of the photographing lens 100, it is possible to confirm in real time whether or not the generated ghost light can be eliminated. As a result, by controlling the aperture 105 when ghost light is generated, it is possible to eliminate ghost light and perform highly accurate distance measurement that is not affected by ghost light.

  As described above, since the generation of ghost light is affected by the position of the light source at the time of shooting, the detection of the presence or absence of ghost light in FIG. . Thereby, it is possible to perform distance measurement with high accuracy in accordance with reality.

  In the first embodiment, four focus detection lines in the focus detection sensor 400 are provided based on the focus detection range set by the photographer, but the configuration is not limited thereto. For example, a plurality of regions corresponding to each of the imaging regions 401A to 401D may be provided, and regions automatically selected by the imaging apparatus 200 from among the regions may be set as four focus detection lines. In this case, for example, the light amount distribution of ghost light is acquired from the sensor output waveform of the ghost detection line, and the light amount distribution of such ghost light is not included as the sensor output waveform, and focus detection is performed on a region where the light amount distribution of only the subject image is obtained. It may be selected as a line. In this case, it is possible to perform highly accurate distance measurement with the aperture 105 of the photographing lens 100 being the initial F value (F1.4). On the other hand, even in this case, the stop 105 of the photographing lens 100 is narrowed until generation of ghost light disappears to prevent generation of ghost light in all the imaging regions 401A to 401D. The focus detection range may be selected. As a result, it is possible to perform distance measurement with high accuracy not affected by ghost light.

  Further, in the first embodiment, the stop 105 of the photographing lens 100 is narrowed stepwise in order to eliminate the generation of ghost light. However, if the light flux incident on the focus detection sensor 400 can be limited, the embodiment is The configuration is not limited to one. For example, the aperture values of the field mask 300 and the aperture stop 302 may be made variable, and the light flux incident on the focus detection sensor 400 may be limited.

DESCRIPTION OF SYMBOLS 100 Shooting lens 101 Focus lens 105 Diaphragm 200 Imaging apparatus 207 Focus detection apparatus 210 Camera control part 300 Field mask 302 Porous diaphragm 303 Secondary imaging lens unit 400 Focus detection sensor 401 Imaging area 402 Ghost detection area

Claims (6)

A dividing unit that divides a distance measuring light beam from an external focus lens into a plurality of regions, a secondary imaging lens that forms each of the divided distance measuring light beams as a plurality of subject images, and the plurality of subject images A sensor having a photoelectric conversion unit that photoelectrically converts the respective light quantity distributions, a determination unit that determines an image field formed on the sensor, and a relative positional relationship between the photoelectrically converted light quantity distributions of the focus lens. A focus detection apparatus having a control unit that detects an in-focus state, the focus detection apparatus comprising:
The sensor is provided with a first sensor region in the range of the image field determined by the determining means, and a second sensor region around the first sensor region,
Detection means for detecting the occurrence of ghost light from the output obtained from the second sensor area;
And a limiting means for stepwise limiting a light beam incident on the sensor until the generation of the ghost light is not detected by the detecting means.   The focus detection apparatus according to claim 1, wherein the first sensor area and the second sensor area are configured by the same sensor array.   Notification means for notifying that the distance cannot be measured when the light flux incident on the sensor is restricted by the restriction means before the detection means no longer detects the generation of the ghost light. The focus detection apparatus according to claim 1, further comprising: The focus detection device according to any one of claims 1 to 3, the focus lens, and a diaphragm for adjusting a light beam transmitted through the focus lens,
The optical apparatus according to claim 1, wherein the diaphragm restricts a light flux incident on the sensor in a stepwise manner by control by the restriction unit.   The optical apparatus according to claim 4, which is an imaging device.   6. The optical apparatus according to claim 5, wherein the detection of the generation of the ghost light by the detection unit and the stepwise restriction of the luminous flux incident on the sensor by the restriction unit are performed at the time of photographing by the imaging device. .

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