JP2006284694A - Focus detector, electronic camera and interchangeable lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focus detector which performs focus detection in a pupil time division system, and where the flicker of an observed image in the midst of focus detection is reduced. <P>SOLUTION: A pupil division member 3 arranged between a photographic lens 2 and an imaging device 4 can turn on/off a hologram function in division areas 301 and 302 and other areas by controlling applied voltage. When voltage is applied only to the division area 301 as shown by (a), the hologram function is turned off only in the division area 301, which becomes transparent, and red light R of an area 301' is deflected to the outside of an optical path. When the voltage is applied only to the division area 302 as shown by (b), the division area 302 becomes transparent, and the red light R of an area 302' is deflected to the outside of the optical path. As a result, image shift amount is detected by alternately turning on/off the division areas 301 and 302 and receiving the red light R transmitted through the division areas 301 and 302. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a focus detection device that performs pupil time-division focus detection, an electronic camera including the focus detection device, and an interchangeable lens that is detachably attached to the electronic camera.

  Conventionally, in an electronic camera such as a digital still camera, a contrast detection method for evaluating a sharpness such as a contrast of an image captured by a photographing image sensor and determining a state where the sharpness reaches a peak as a focused state Focus detection is known. When this method is adopted, there is no need to provide a separate focus detection sensor, which is advantageous for reducing the cost and size of the camera, but on the other hand, it takes the time to focus. Have.

  As in the contrast detection method described above, a camera that performs focus detection using the pupil time-division type image shift detection method is known as a method for performing focus detection using the output signal of the image sensor for photographing and reducing the focusing time. (For example, refer to Patent Document 1). In this camera, pupil selection means using liquid crystal is provided in the vicinity of the exit pupil position of the photographing lens, and a pair of pupil openings can be formed in the pupil selection means by switching between transmission and non-transmission of liquid crystal. it can. Then, the focus adjustment state of the photographing lens is detected by alternately switching the transmission state of the pair of pupil openings and detecting the positional deviation between the subject images due to the light transmitted through the pupil openings.

JP-A-6-175015

  However, the above-described camera has a disadvantage that the amount of light is reduced and the entire screen becomes darker than the time of photographing that is always in a transmissive state because transmission and non-transmission of liquid crystal are alternately repeated during the focus detection operation. . In addition, image blur occurs in an image portion that is not in focus in synchronization with the liquid crystal switching. For this reason, when the output signal of the image sensor for photographing is used in an electronic viewfinder, the screen is dark or image blurring occurs during focus detection, which makes it very difficult to see.

According to the first aspect of the present invention, the focus adjustment state of the photographing optical system is mounted on a photographing device that picks up a subject image in which a light flux from the subject is imaged by the photographing optical system, and based on an imaging signal obtained by pupil time division. The first and second regions are applied to a focus detection device for detection and are disposed in a subject optical path of the photographing optical system and have different centroid positions in a plane orthogonal to the optical axis of the photographing optical system. (A) a first state of deflecting light in a predetermined wavelength region incident on the first region of incident subject light; and (b) light in a predetermined wavelength region incident on the second region of incident subject light. And (c) a deflection member that can be switched between the third state in which the incident subject light is transmitted as it is and the imaging surface of the imaging optical system or an optically substantially equivalent position. Image sensor, first state and second state Focus detection means for detecting the focus adjustment state of the photographic optical system based on the imaging signal of each of the imaging elements, and when detecting the focus adjustment state, the first state and the second state of the deflecting member are And a control means for switching the deflecting member to the third state when the focus adjustment state is not detected when the focus adjustment state is not detected.
According to a second aspect of the present invention, in the focus detection apparatus according to the first aspect, the deflecting member has a plurality of paired regions each composed of the first and second regions, and the focus detection means detects the focus adjustment state. This is performed for each area.
According to a third aspect of the present invention, in the focus detection apparatus according to the first or second aspect, the imaging device has a plurality of pixels having different spectral sensitivity characteristics, and the focus detection means includes a plurality of pixels included in the imaging device. The focus adjustment state is detected based on a signal from a pixel having the highest detection sensitivity with respect to light in a predetermined wavelength region.
According to a fourth aspect of the present invention, in the focus detection apparatus according to any one of the first to third aspects, the deflecting member is composed of a diffractive optical element using liquid crystal.
According to a fifth aspect of the present invention, there is provided an electronic camera according to any one of the first to fourth aspects, a photographing imaging device that captures a subject image by receiving light transmitted through the photographing optical system, and focus detection. An autofocus control means for performing a focus adjustment operation of the photographing optical system based on a focus adjustment state detected by the apparatus, and an image pickup signal of an image pickup device included in the focus detection apparatus regardless of whether the focus adjustment state is detected or not detected Display means for displaying an image on the basis thereof.
According to a sixth aspect of the present invention, there is provided an electronic camera according to any one of the first to fourth aspects, a photographing imaging device that captures a subject image by receiving light transmitted through the deflecting member, and a focal point detecting device. Autofocus control means for performing a focus adjustment operation of the photographing optical system based on the focus adjustment state detected by the recording means, and a recording means for recording an image based on the image pickup signal of the image pickup element irrespective of whether the focus adjustment state is detected or not detected The focus detection means detects the focus adjustment state based on the imaging signal output from the imaging element for imaging.
According to a seventh aspect of the present invention, in the electronic camera according to the fifth or sixth aspect, the evaluation value calculating means for calculating a focus evaluation value representing the sharpness of the captured image based on the imaging signal of the imaging element for imaging. The autofocus control means performs a focus adjustment operation of the photographing optical system based on at least one of the focus evaluation value and the focus adjustment state detected by the focus detection device.
According to an eighth aspect of the present invention, there is provided a focus detection apparatus comprising: a photoelectric conversion element disposed at a position optically substantially equivalent to an imaging surface of a photographing optical system that forms a light beam from a subject; and an optical path of the light beam of the photographing optical system. Light having a first wavelength region and a second region different from each other in the center of gravity within a plane orthogonal to the optical axis of the photographing optical system, and having a predetermined wavelength range of a light beam incident on the first region Splitting that alternately switches in a time-division manner a first state in which the light is deflected to the photoelectric conversion element and a second state in which light in a predetermined wavelength region of the light beam incident on the second region is deflected to the photoelectric conversion element And focus detection means for detecting the focus adjustment state of the photographing optical system based on the output signal of the photoelectric conversion element.
An electronic camera according to an invention of claim 9 is disposed on an imaging surface of an imaging optical system that forms an image of a light beam from a subject, and receives an image of the subject by receiving the light beam from the subject;
The photoelectric conversion element disposed at a position optically equivalent to the imaging plane and the optical center of the photographing optical system are arranged in the optical path of the light flux of the photographing optical system, and the center of gravity position is mutually in the plane perpendicular to the optical axis of the photographing optical system. A first state having different first and second regions, (a) a first state in which light of a predetermined wavelength region incident on the first region of the incident light beam is deflected to the photoelectric conversion element; and (b) the incident light beam. A deflecting member that can be switched between a second state in which light in a predetermined wavelength region incident on the second region is deflected to the photoelectric conversion element and (c) a third state in which the incident light beam is transmitted as it is. And a focus detection means for detecting the focus adjustment state of the photographic optical system based on the imaging signals of the photoelectric conversion elements in each of the first state and the second state, and a deflection member in the case of detecting the focus adjustment state The first state and the second state are alternately switched in time division For example, if it does not detect the focus adjustment state is characterized in that a control means for switching the deflection member to the third state.
According to a tenth aspect of the present invention, there is provided an interchangeable lens that is detachably attached to an electronic camera that detects a focus adjustment state by a pupil time division method, and is provided in a subject optical path of a photographing lens. A first state of deflecting light in a predetermined wavelength region incident on the first region, and (b) a predetermined wavelength region incident on the second region having a gravity center position different from that of the first region from the incident subject light. A deflection member that can be switched between a second state of deflecting the light of (3) and a third state of transmitting the incident subject light as it is, and at the time of detecting the focus adjustment state by the pupil time division method, And a switching drive unit that switches alternately between the first state and the second state.
A focus detection device according to an eleventh aspect of the present invention is arranged on an imaging surface of a photographing optical system that forms an image of a light beam from a subject. Light having a first wavelength region and a second region different from each other in the center of gravity within a plane orthogonal to the optical axis of the photographing optical system, and having a predetermined wavelength range of a light beam incident on the first region A deflection member that can be switched between a first state for deflecting light and a second state for deflecting light in a predetermined wavelength region of a light beam incident on the second region, and the deflection member for the first state and the second state Switching means for alternately switching to a state, and a focus for obtaining a focus adjustment state for a subject of the photographing optical system based on a photoelectric conversion signal obtained by the photoelectric conversion element in each of the first state and the second state by the switching means Equipped with detection means The features.

  According to the present invention, in the first state, only light in a predetermined wavelength region incident on the first region is deflected out of the optical path, and in the second state, only light in a predetermined wavelength region incident on the second region is deflected. Since it is only deflected to the outside of the optical path, it is possible to reduce image flicker during focus detection while alternately switching between the first and second states.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration when a focus detection apparatus according to the present invention is applied to an electronic camera. The electronic camera 1 is provided with a photographic lens 2 and an imaging element 4 that captures a subject image formed by the photographic lens 2. As the image sensor 4, an image sensor such as a CCD type or a CMOS type is used. On the optical axis J between the photographing lens 2 and the image sensor 4, a pupil dividing member 3 driven by the drive unit 12 is disposed. When the photographing lens 2 is configured by a lens group having a plurality of lenses, the pupil division member 3 may be disposed between the lens groups.

  A signal output from the image sensor 4 is input to the control calculation unit 5. The control calculation unit 5 includes a signal processing circuit that performs various image processing on the output signal of the image sensor 4, and (a) controls the drive unit 12 of the image sensor 4 and the pupil dividing member 3, and (b) the image sensor. (C) Defocus amount of the photographing lens 2 performed based on the calculated image shift amount (on the image plane of the subject and the image sensor 4) (D) Calculation of focus evaluation value (evaluation value of contrast sharpness of subject image) based on output signal of image sensor 4 (D) e) The lens drive unit 11 is controlled based on the calculated defocus amount and focus evaluation value.

  The lens driving unit 11 drives the focus lens of the photographing lens 2 according to a command from the arithmetic control unit 5. Image information obtained by image processing in the arithmetic control unit 5 is stored in the storage unit 6. A recording medium 10 is detachably attached to the electronic camera 1, and image information stored in the storage unit 6 is transferred to the recording medium 10. In addition, the electronic camera 1 includes an electronic viewfinder 7, and the image information stored in the storage unit 6 can be displayed on the display unit 8 configured by an LCD or the like and can be observed by the observation optical system 9.

<< Description of Pupil Dividing Member 3 >>
FIG. 2 is a plan view of the pupil division member 3 as viewed from the direction of the image sensor 4. The pupil division member 3 is composed of a liquid crystal hologram, and the two division regions 301 and 302 are provided at positions symmetrical with respect to the optical axis J. That is, the center of gravity of the divided region 301 is at a position of a distance d on the left side of the optical axis J, and the center of gravity of the divided region 302 is at a position of a distance d on the right side of the optical axis J. The divided regions 301 and 302 have optical characteristics as a phase type volume hologram.

  FIG. 3 schematically shows an AA cross section of FIG. In the figure, for convenience of explanation, the divided areas 301 and 302 are drawn narrower than actual. In FIG. 3, reference numerals 311 and 312 denote transparent substrates made of glass, plastic or the like, and electrode patterns made of transparent conductive films 313 and 314 are formed on the surfaces of the transparent substrates 311 and 312 facing each other. The transparent conductive films 313 and 314 correspond to transparent conductive films 313b and 314b corresponding to the divided region 301, transparent conductive films 313c and 314c (not shown) corresponding to the divided region 302, and regions other than the divided regions 301 and 302. The transparent conductive films 313a and 314a are separated from each other, and the driving unit 12 can individually apply a voltage to each.

  Between the transparent substrate 311 and the transparent substrate 312, a polymer dispersed liquid crystal 315 in which liquid crystal particles 315b are dispersed in a polymer polymer 315a is sandwiched. 2 has the same structure as that of the divided region 301. The polymer dispersed liquid crystal 315 has a layered structure in which the liquid crystal particles 315b are dispersed in the molecular polymer 315a, and the high density layer 316 of the liquid crystal particles 315b and the low density layer 317 of the liquid crystal particles 315b appear alternately. ing. This layered structure has the same periodic structure as an interference fringe pattern to be described later, and functions as a volume hologram for incident light when the applied voltage is low.

  When forming the pupil division member 3 having such a hologram function, first, liquid crystal and a photocurable monomer are mixed to disperse the liquid crystal in the monomer, and then the pupil division member 3 as shown in FIG. Laser exposure. FIG. 4 is a conceptual diagram illustrating laser exposure for forming a hologram. For example, when the laser object light L2 created by arranging a diffraction grating generated by a computer in the object light is caused to interfere with the laser reference light L1, and the pupil division member 3 is disposed in the interference region, the transparent substrate 311 is obtained. A light intensity distribution pattern corresponding to the interference fringes is also formed between 1 and 312.

  The above-mentioned mixed member of the liquid crystal and the photocurable monomer is a recording member for recording the interference fringes formed as described above as a hologram. The liquid crystal dispersed in the monomer becomes liquid crystal particles 315b when the monomer is photopolymerized, and in the portion where the light intensity is increased by interference, the photopolymerization of the monomer proceeds sufficiently to increase the density of the polymer. On the contrary, in the portion where the light intensity is weak, the density of the liquid crystal particles 315b is increased by the amount that the monomer is attracted to the portion where the light intensity is strong.

  In this way, a hologram composed of the low density layer 317 of the liquid crystal particles 315b and the high density layer 316 of the liquid crystal particles 315b as shown in FIG. 3 is formed in the polymer dispersed liquid crystal 315. The hologram formed in the present embodiment is designed so that the diffraction efficiency is high with respect to the light R in a specific wavelength region when the light L11 is incident on the pupil division member 3. That is, when creating a hologram, exposure is performed with a laser beam having the same wavelength as the light R in a specific wavelength region. Therefore, the light R is diffracted in a predetermined angle direction, and the light L11 'having other wavelengths is transmitted so as to travel straight through the pupil division member 3.

  As a hologram deflection effect, for example, as in the case of (a) prism, all light incident at the same angle regardless of the image height (distance from the optical axis) may be deflected by the same angle. (B) The diffracted light R may be collected in a predetermined range by applying a lens effect to the hologram. In the latter case, it becomes easy to prevent the diffracted light R from being reflected inside the camera and becoming stray light.

  The light R in the specific wavelength range is set as follows. The image pickup device 4 is a color CCD in which one of three types of filters is arranged for each pixel constituting the CCD, and has a structure in which three types of pixels having different spectral transmission characteristics are arranged in a mosaic pattern. FIG. 5 schematically shows the spectral transmission characteristics of the three types of filters. The horizontal axis represents wavelength and the vertical axis represents sensitivity. The spectral transmission characteristic of the first type filter FR has a peak at the red wavelength, the spectral transmission characteristic of the second type filter FG has a peak at the green wavelength, and the spectral transmission characteristic of the third type filter FB. The transmission characteristic has a peak at a blue wavelength.

  As will be described later, the electronic camera of the present embodiment is configured to perform focus detection using red light R that passes through the first type of filter FR. Therefore, the hologram formed on the pupil division member 3 is configured to diffract the red light R by using a hologram having a high diffraction efficiency near red. In addition, not only the red light R but also a hologram may be configured to diffract blue light or green light, and focus detection may be performed using these lights.

<< Explanation of operation of pupil division member 3 >>
Next, the on / off operation of the hologram function of the pupil division member 3 will be described. FIGS. 6A and 6B are diagrams showing the types of operation states of the pupil division member 3, wherein FIG. 6A shows the first state, FIG. 6B shows the second state, and FIG. 6C shows the third state. FIGS. 7 to 9 schematically show the A1-A1 cross section, the A2-A2 cross section, and the A3-A3 cross section shown in FIGS. 6A to 6C, respectively.

  In the first state shown in FIG. 6A, a voltage is applied to the transparent conductive films 313b and 314b in the divided region 301 shown in FIG. In FIG. 7, reference numeral 318 represents liquid crystal molecules in the liquid crystal particles 315b. In the divided region 301, by applying an applied voltage, the optical axes of the liquid crystal molecules 318 in the liquid crystal particles 315b are aligned in the thickness direction of the pupil dividing member 3, and the effective refractive index neff of the liquid crystal particles 315b is set to be an isotropic polymer. The refractive index np of the polymer 315a is made substantially equal.

  Therefore, in the first state shown in FIG. 7, there is no difference in refractive index between the layer 316 and the layer 317 in the divided region 301, and the layers 316 and 317 do not function as holograms. As a result, the divided region 301 is transparent to both the red light R and light of other wavelengths, and the light L12 incident on the divided region 301 is transmitted so as to travel straight through the pupil dividing member 3.

  On the other hand, in the region 301 ′ other than the hatched divided region 301 in FIG. 6A, the applied voltage is turned off. In this case, the liquid crystal molecules 318 in the liquid crystal particles 315b are randomly oriented. As a result, a difference in refractive index occurs between the liquid crystal particles 315b and the isotropic polymer 315a, and the layers 316 and 317 in regions other than the divided region 301 function as holograms with respect to red light. Therefore, the red light R included in the incident light L11 is diffracted out of the subject optical path in the upper right direction in the figure as indicated by a one-dot chain line, and the other light L11 'is transmitted so as to travel straight through the pupil dividing member 3.

  That is, in the first state, the red light R in the region 301 ′ is deflected out of the optical path of the subject light from the subject lights L 11 and L 12 incident on the pupil division member 3. The remaining light (light L11 'other than red light R in the region 301' and subject light L12 incident on the divided region 301) is transmitted in the direction toward the image sensor 4 without being deflected.

  In the second state shown in FIG. 6B, the applied voltage in the divided region 302 is turned on and the applied voltage in other regions is turned off. As shown in the A2-A2 cross-sectional view of FIG. 8, since no voltage is applied to the divided region 301, the alignment directions of the liquid crystal molecules 318 in the liquid crystal particles 315b are random. Therefore, in the hatched region 302 ′ including the divided region 301 in FIG. 6B, the red light R included in the incident light L11 and L12 is diffracted as shown in FIG. 8, and the remaining light L11 ′, L12 ′ passes through the pupil division member 3 so as to go straight. Further, the state of the divided region 302 to which the voltage is applied is the same as that of the divided region 301 shown in FIG. 7, and the incident light is transmitted as it is.

  That is, in the second state, the red light R in the region 302 ′ is deflected from the subject light incident on the pupil division member 3 to the outside of the optical path of the subject light, and the remaining light (other than the red light R in the region 302 ′) is deflected. The light and the subject light incident on the divided region 302 are transmitted as they are toward the image sensor 4 without being deflected.

  In the third state shown in FIG. 6C, the applied voltage of the entire region of the pupil dividing member 3 is turned on. Therefore, as shown in FIG. 9, the liquid crystal molecules 318 in the liquid crystal particles 315b are aligned in the electric field direction in all regions, and the hologram function is not expressed in all regions. Therefore, the entire region of the pupil division member 3 is transparent with respect to the incident lights L11 and L12, and the incident lights L11 and L12 are transmitted as they are. When performing pupil time-division focus detection described later, the first state and the second state are used, and when photographing is performed, the third state in which the whole is in a transparent state is used.

<Explanation of focus detection>
In the camera of the present embodiment, the focus state of the photographic lens 2 can be detected by two types of methods. The first method is a pupil time division type focus detection using the pupil division member 3, and the second method is a contrast detection type focus detection using a focus evaluation value representing the contrast sharpness of a captured image. is there.

(Eye time-division focus detection)
First, pupil time division focus detection, which is the first method, will be described. FIGS. 10 and 11 are views for explaining the principle of focus detection using the pupil division member 3, and is a view of the photographing lens 2, the pupil division member 3 and the image sensor 4 as viewed from the X direction in FIG. The divided areas 301 and 302 of the pupil dividing member 3 are arranged in the vertical direction in the figure with the optical axis J in between. The focus detection method using the pupil division member 3 in the present embodiment is in principle the same as the conventional pupil time division focus detection, but performs focus detection using the red light R included in the subject light. The point is different.

  As described above, the hologram of the pupil division member 3 has a structure with good diffraction efficiency near the red light R, and it can be said that light other than the vicinity of the red light R is in a transparent state regardless of whether the applied voltage is on or off. Therefore, in FIGS. 10 and 11, only the red light R is illustrated as the light beam. 10A and 10B show a focused state in which the position of the imaging surface of the photographic lens 2 and the position of the imaging surface of the image sensor 4 coincide with each other.

  3 and 6 to 9 described above, an example has been described in which the red light R is diffracted above the optical axis J by the hologram. 10 and 11, in order to make it easy to understand the diffraction and image shift of the red light R, the red light R is moved in the right direction of the image sensor 4 in the region on the right side (the upper side in the drawing) of the optical axis J when viewed from the image sensor 4. An example will be described in which diffraction is performed in the upper part of the figure and diffracted in the left direction (lower part of the figure) of the image sensor 4 in the region on the left side (lower side of the figure) of the optical axis.

  FIG. 10A shows a case where a voltage is applied to the divided region 301 of the pupil dividing member 3, that is, the first state described above. In this case, the red light R incident on the divided region 301 is directly incident on the image sensor 4 without being deflected by diffraction. On the other hand, in the region 301 ′ other than the divided region 301, the red light R is deflected in the left-right direction of the image sensor 4 by diffraction as indicated by a two-dot chain line, and does not enter the image sensor 4. FIG. 10B shows the case where the pupil dividing member 3 is in the second state described above. The red light R incident on the divided region 302 is incident on the image sensor 4 without being deflected. The red light R that has entered the region 302 ′ is deflected and does not enter the image sensor 4.

  On the other hand, FIGS. 11A and 11B show the case where the position of the imaging plane is closer to the photographing lens 2 than the position of the imaging plane, that is, the case where the focus is shifted forward. The states of the pupil division member 3 in FIGS. 11A and 11B are the same as those in FIGS. 10A and 10B. FIG. 11A shows that the applied voltage of the divided region 301 is on. In FIG. 11B, the applied voltage of the divided region 302 is on.

  In the case of FIG. 11A, a slightly blurred image is formed on the imaging surface of the imaging device 4 by the red light R that has passed through the divided region 301, and the position of the image is on the right side (upper side in the drawing) of the optical axis J. It's off. In the case of FIG. 11B as well, an image that is slightly blurred by the red light R that has passed through the divided region 302 is formed on the imaging surface of the imaging device 4, but the position of the image is opposite to that in the case of FIG. Is shifted to the left side (lower side in the figure) from the optical axis J. In contrast to the case of FIG. 11, when the focal point is shifted to the rear of the imaging surface, the image shift direction is opposite to that described above.

  The control calculation unit 5 (see FIG. 1) calculates the above-described image shift amount based on the output signal of the image sensor 4, and calculates the defocus amount of the photographing lens 2 based on the calculated image shift amount. When detecting the amount of image shift, the control calculation unit 5 controls the voltage applied to the pupil dividing member 3 to alternately switch between the first state and the second state.

  Since the pupil dividing member 3 is always in a transparent state with respect to light other than the red light R, the light other than the red light R becomes unnecessary light for detecting the image shift amount. Therefore, when focus detection is performed by the pupil time division method, the image shift amount is detected using only the output signal of the pixel provided with the first type filter FR that transmits the red light R. As a result, the image shift amount can be detected more accurately.

  On the other hand, the display unit 8 of the electronic viewfinder 7 displays an image based on an output signal from the image sensor 4 even during focus detection using the pupil time division method. The conventional pupil time-division focus detection using a liquid crystal shutter has a drawback that flicker (flickering) is difficult to see in an image observed with the electronic viewfinder 7 because much light is blocked by the liquid crystal shutter during focus detection. It was. In addition, there was a drawback that the blurred image seemed to shake and was difficult to see.

  However, in the focus detection apparatus of the present embodiment, the pupil time-division focus detection is performed using only the red light R, so light other than the red light R is always imaged even during focus detection. A decrease in the amount of light can be reduced. In the image displayed on the display unit 8, flicker and blurring of the blurred image due to alternately turning on and off the divided areas 301 and 302 are observed. However, since light other than the red light R is always captured, the red light Flicker and blurring caused by R can be made inconspicuous.

  Further, when the captured image is sequentially displayed on the display unit 8 of the electronic viewfinder 7, the other filters FB and FG weight the output signals of the pixels provided with the filter FR, that is, the pixels for detecting the red light R. By making it smaller than the weighting for the output signal of the provided pixel, flicker or the like can be made less noticeable. Such weighting can be performed not only for image display but also for image recording.

(Contrast detection focus detection)
Next, focus detection by contrast detection will be described. There is a correlation between the degree of image blur and contrast, and the image contrast is maximized when in focus. The magnitude of the contrast (sharpness) can be evaluated by the magnitude of the high-frequency component of the imaging signal. This evaluation value is called a focus evaluation value, and the control calculation unit 5 extracts a high frequency component of the imaging signal and integrates the absolute value of the high frequency component as a focus evaluation value. This focus evaluation value becomes the maximum value when the focus is reached and the contrast becomes maximum.

<< Explanation of AF operation >>
As described above, in the present embodiment, the focus is divided into two methods: pupil time-division focus detection capable of quick AF operation, and contrast detection method capable of performing focus adjustment with a low speed while focusing accurately. Since the adjustment state can be detected, various effective AF operations can be performed by properly using them. The focus detection apparatus according to the present invention can be applied to both still image shooting and moving image shooting.

  In the case of still image shooting, AF operation is performed when the release button is pressed halfway, and shooting is performed when the release button is fully pressed. In the AF operation, first, coarse adjustment is performed by the pupil time division method, and then fine adjustment is performed by the contrast detection method. In this case, image flicker (flicker) on the electronic viewfinder at the time of the pupil time division AF operation can be reduced.

In the case of moving image shooting, AF is normally performed using a contrast detection formula. However, in the following situation, AF is performed using a pupil time division formula.
(A) Performing in the initial stage of moving image shooting For example, when the defocus amount at the start of shooting is large, if AF is performed only with the contrast detection method, it may take time to focus or focus may not be achieved. However, by performing AF using the pupil time division method at the start of shooting, a sharp image without blur can be shot and recorded immediately after the start of shooting. Therefore, when one frame of a moving image is used as a still image, a sharp still image can be cut out from the moving image immediately after shooting. Further, since a sharp image can be taken immediately after the photographing operation, it is possible to take a sharp image without missing the scene to be photographed.

(B) When image blur occurs suddenly during movie shooting For example, when the camera is panned, the image blur becomes very large. Switch back to the detection method.
(C) When the release button is pressed halfway In general, when the release button is operated, movie shooting starts, but here, half-pressed performs a pupil time-division AF operation, and fully presses to shoot. Use an action that starts. As a result, it is possible to shoot and record a sharp image from the start of shooting.

  In the embodiment described above, when focus detection is performed by the pupil time division method, the divided regions 301 and 302 are alternately made transparent as shown in FIGS. 6A and 6B, and are not transparent. The red light R is diffracted and deflected in the regions (hatched regions 301 ′ and 302 ′). However, by reversing this relationship, the hatched areas 301 ′ and 302 ′ may be made transparent, and the red light R may be deflected in the non-hatched divided areas 301 and 302. Also in this case, in the hatching area 301 ′ of FIG. 6A and the hatching area 302 ′ of FIG. 6B, the center of gravity of each area is shifted to the left and right across the optical axis J. Deviation can be formed. Furthermore, although a pair of divided regions 301 and 302 are provided to detect an image shift in one direction, two or more pairs may be provided to detect an image shift in two or more directions.

  In addition, as described above, the present invention is not limited to a single-plate color electronic camera that detects color information with a single image sensor 4, but also to a three-plate color electronic camera in which three types of spectral sensitivity are assigned to three image sensors. Applicable. Further, in the case of an interchangeable lens camera, the taking lens 2 and the pupil dividing member 3 are provided in the lens barrel of the interchangeable lens. Then, a voltage is applied to the pupil division member 3 by the drive unit 12 provided on the camera body side.

  Further, a photoelectric conversion element for detecting an image shift is arranged separately from the image pickup element 4 for photographing so as to deflect the red light R to the photoelectric conversion element in a time division manner. Also good. In this case, the focus adjustment state of the photographic lens 2 can be detected by detecting the image shift by receiving the deflected red light R with the photoelectric conversion element.

  The member used for the pupil division member 3 is not limited to the holographic polymer dispersed liquid crystal described above, and any element that can turn on and off the diffraction function by electrical or magnetic means may be used. Note that the focus detection apparatus of the present invention is not limited to an electronic camera that is also used as a moving image and still image, but can also be applied to an electronic camera that is dedicated to moving images or dedicated to still images.

  In the correspondence between the embodiment described above and the elements of the claims, the photographing lens 2 represents the photographing optical system, the region 301 ′ represents the first region, the region 302 ′ represents the second region, and the pupil dividing member. 3 is a deflection member, pupil dividing member 3, drive unit 12 and calculation control unit 5 are pupil division means, calculation control unit 5 and drive unit 12 are control means, drive unit 12 is a switching drive unit and switching means, The calculation control unit 5 is a focus detection unit, an autofocus control unit, and an evaluation value calculation unit, the light R in a specific wavelength range is light in a predetermined wavelength range, the display unit 8 is display means, the storage unit 6 and the recording medium 10 are Each of the recording means is configured. The above description is merely an example, and when interpreting the invention, there is no limitation or restriction on the correspondence between the items described in the above embodiment and the items described in the claims.

It is a figure which shows schematic structure at the time of applying the focus detection apparatus by this invention to an electronic camera. FIG. 3 is a plan view of the pupil division member 3 viewed from the direction of the image sensor 4. It is a schematic diagram which shows the AA cross section of FIG. It is a conceptual diagram explaining the laser exposure for hologram formation. It is a figure which shows the spectral transmission characteristic of 3 types of filters. It is a figure which shows the kind of operation state of the pupil division member 3, (a) shows a 1st state, (b) shows a 2nd state, (c) shows a 3rd state, respectively. It is a schematic diagram which shows the A1-A1 cross section of Fig.6 (a). It is a schematic diagram which shows the A2-A2 cross section of FIG.6 (b). It is a schematic diagram which shows the A3-A3 cross section of FIG.6 (c). It is a figure explaining the deflection | deviation state at the time of focusing, (a) shows a 1st state, (b) shows a 2nd state, respectively. It is a figure explaining the deflection | deviation state at the time of a non-focusing, (a) shows a 1st state, (b) shows a 2nd state, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electronic camera 2 Shooting lens 3 Pupil division member 4 Imaging element 5 Calculation control part 12 Drive part 301,302 Division area 301 ', 302' area

Claims (11)

In a focus detection device that is mounted on a photographing device that captures a subject image obtained by imaging a light beam from a subject with a photographing optical system and detects a focus adjustment state of the photographing optical system based on an imaging signal obtained by pupil time division ,
(A) Incident subject light having a first and a second region disposed in the subject optical path of the photographing optical system and having different centroid positions in a plane perpendicular to the optical axis of the photographing optical system. A first state of deflecting light of a predetermined wavelength region incident on the first region, and (b) second of deflecting light of a predetermined wavelength region incident on the second region of incident subject light. And (c) a deflecting member that can be switched between the third state in which the incident subject light is transmitted as it is,
An imaging device disposed at an imaging surface of the imaging optical system or an optically substantially equivalent position;
Focus detection means for detecting a focus adjustment state of the imaging optical system based on an imaging signal of the imaging element in each of the first state and the second state;
When the focus adjustment state is detected, the first state and the second state of the deflection member are alternately switched in a time-sharing manner. When the focus adjustment state is not detected, the deflection member is switched to the third state. And a control means for switching to the above state. The focus detection apparatus according to claim 1,
The deflecting member has a plurality of paired regions composed of the first and second regions,
The focus detection device, wherein the focus detection unit detects the focus adjustment state for each paired region. The focus detection apparatus according to claim 1 or 2,
The image sensor has a plurality of pixels having different spectral sensitivity characteristics,
The focus detection unit detects the focus adjustment state based on a signal from a pixel having the highest detection sensitivity with respect to light in the predetermined wavelength region among a plurality of pixels included in the image sensor. Focus detection device. In the focus detection apparatus according to any one of claims 1 to 3,
A focus detection apparatus, wherein the deflecting member is composed of a diffractive optical element using liquid crystal. The focus detection device according to any one of claims 1 to 4,
An image sensor for photographing that receives light transmitted through the photographing optical system and images a subject image;
Autofocus control means for performing a focus adjustment operation of the photographing optical system based on a focus adjustment state detected by the focus detection device;
An electronic camera comprising: display means for displaying an image based on an imaging signal of the imaging element included in the focus detection device regardless of whether the focus adjustment state is detected or not. The focus detection device according to any one of claims 1 to 4,
An imaging element for taking a picture of a subject by receiving light transmitted through the deflection member;
Autofocus control means for performing a focus adjustment operation of the photographing optical system based on a focus adjustment state detected by the focus detection device;
Regardless of whether the focus adjustment state is detected or not detected, a recording unit that records an image based on an imaging signal of the imaging element,
The electronic camera according to claim 1, wherein the focus detection unit detects a focus adjustment state based on an imaging signal output from the imaging element for photographing. The electronic camera according to claim 5 or 6,
An evaluation value calculating means for calculating a focus evaluation value representing the sharpness of a captured image based on an imaging signal of the imaging element for photographing;
The electronic camera characterized in that the autofocus control means performs a focus adjustment operation of the photographing optical system based on at least one of the focus evaluation value and the focus adjustment state detected by the focus detection means. A photoelectric conversion element disposed at a position optically substantially equivalent to an imaging surface of a photographing optical system that images a light beam from a subject;
A first region and a second region which are disposed in an optical path of the light beam of the photographing optical system and have different positions of the center of gravity in a plane perpendicular to the optical axis of the photographing optical system; A first state in which light in a predetermined wavelength region of the light beam incident on the region is deflected to the photoelectric conversion element; and light in a predetermined wavelength region of the light beam incident on the second region is directed to the photoelectric conversion element. Pupil division means for alternately switching the second state to be deflected by time division;
A focus detection device comprising: focus detection means for detecting a focus adjustment state of the photographing optical system based on an output signal of the photoelectric conversion element. An imaging element that is disposed on an imaging surface of a photographing optical system that forms a light beam from a subject, and that receives the light beam from the subject and images a subject image;
A photoelectric conversion element disposed at a position optically equivalent to the imaging plane;
The first and second regions are disposed in the optical path of the light beam of the photographing optical system and have different centroid positions in a plane orthogonal to the optical axis of the photographing optical system, and (a) incident A first state of deflecting light of a predetermined wavelength range incident on the first region of the luminous flux to the photoelectric conversion element; and (b) of a predetermined wavelength range incident on the second region of the incident luminous flux. A deflecting member that can be switched between a second state in which light is deflected to the photoelectric conversion element and (c) a third state in which the incident light beam is transmitted as it is;
Focus detection means for detecting a focus adjustment state of the photographing optical system based on an imaging signal of the photoelectric conversion element in each of the first state and the second state;
When the focus adjustment state is detected, the first state and the second state of the deflection member are alternately switched in a time-sharing manner. When the focus adjustment state is not detected, the deflection member is switched to the third state. An electronic camera comprising a control means for switching to the state. An interchangeable lens that is detachably attached to an electronic camera that detects a focus adjustment state by a pupil time division method,
(A) a first state of deflecting light in a predetermined wavelength range incident on the first region of the incident subject light; and (b) the first subject from the incident subject light. It is possible to switch between a second state in which light in a predetermined wavelength region incident on a second region having a center of gravity position different from that of the first region and (c) a third state in which incident subject light is transmitted as it is. A deflection member;
An interchangeable lens, comprising: a switching drive unit that alternately switches the deflecting member between the first state and the second state when the focus adjustment state is detected by the pupil time division method. A photoelectric conversion element that is disposed on an imaging surface of a photographing optical system that forms an image of a light beam from a subject, and photoelectrically converts the light beam from the subject;
A first region and a second region which are disposed in an optical path of the light beam of the photographing optical system and have different positions of the center of gravity in a plane perpendicular to the optical axis of the photographing optical system; Deflection that can be switched between a first state in which light in a predetermined wavelength region of the light beam incident on the region is deflected and a second state in which light in the predetermined wavelength region of the light beam incident on the second region is deflected Members,
Switching means for alternately switching the deflection member between the first state and the second state;
Focus detecting means for obtaining a focus adjustment state of the photographing optical system with respect to the subject based on a photoelectric conversion signal obtained by the photoelectric conversion element in each of the first state and the second state by the switching means. A focus detection apparatus characterized by that.

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