JP5287450B2 - Focus detection apparatus and imaging apparatus - Google Patents

Description

  The present invention relates to a focus detection device and an imaging device.

  In a single-lens reflex camera equipped with a focus detection device, a configuration is known in which subject light is reflected by a sub-mirror provided separately from a main mirror on a photographing optical path and guided to the focus detection device. In such a camera, the sub-mirror is retracted to the outside of the photographing optical path at the time of exposure, and the sub-mirror is returned to the original position when photographing is completed.

  The stationary position of the sub mirror on the photographing optical path changes due to the influence of this operation, and an error occurs in the focus detection result. For this reason, for example, Patent Document 1 discloses a technique for reducing or eliminating an error in a focus detection result by drawing an index for detecting a stationary position in advance on a submirror. Specifically, the position of the index for stationary position detection is detected by the image sensor of the phase difference type focus detection device, and the focus detection result is corrected using the detection result.

Japanese Patent Laid-Open No. 2002-98884

  In the camera of Patent Document 1, the stationary position of the sub mirror is detected by an optical system and a light receiving element used for autofocus. Accordingly, the optical system and the light receiving element are affected by the position shift due to the secular change and the like, and the stationary position detection with high accuracy cannot be performed.

According to a first aspect of the present invention, there is provided a reflecting member that reflects the first light beam transmitted through the optical system in a predetermined direction, a light receiving unit that receives the reflected light of the light reflected by the reflecting member, and the reflected light. A focus detection unit that detects a focus state of the optical system based on a signal obtained by receiving light by the light receiving unit and outputs a detection signal; and a second light beam different from the first light beam to the reflection member. And a light source for irradiating the light beam, and a correcting unit for correcting the detection signal based on an output obtained by receiving the second light flux reflected by the reflecting member by the light receiving unit. It is a detection device.
The invention according to claim 9 is an image pickup apparatus comprising the focus detection apparatus according to any one of claims 1 to 7.

  According to the present invention, the influence of secular change of the submirror can be removed from the focus detection result without being affected by the position shift of the optical system and the light receiving element used for autofocus.

It is sectional drawing which shows the structure of the imaging device of 1st Embodiment. It is a figure which shows the structure of the focus detection optical system integrated in the imaging device by 1st Embodiment. 3 is a perspective view of a microlens array 52 and a light receiving element array 53. FIG. It is sectional drawing which shows the AA cross section of the micro lens array 52 and the light receiving element array 53 which are shown in FIG. It is a figure for demonstrating the 1st focus detection method by the focus detection apparatus 16 of 1st Embodiment. 2 is a block diagram showing a detailed configuration of a focus detection device 16. FIG. It is a front view of the submirror 12 seen from LED31. It is a figure which shows the mode of the position detection of the submirror 12 by the light beam for position detection. 6 is a plan view showing a state in which a position detection light beam is incident on a light receiving element group 535 on the light receiving element array 53. FIG. It is a figure which shows the micro lens array 62 and the light receiving element array 63 by 2nd Embodiment. It is a figure for demonstrating the position detection system of the submirror by 2nd Embodiment. It is a figure which shows the modification of the 2nd focus detection method. 3 is a diagram showing a configuration for guiding a position detection light beam to a focus detection device 16 without using a binary optical element 29. FIG.

(First embodiment)
FIG. 1 is a cross-sectional view illustrating the configuration of the imaging apparatus according to the first embodiment. Note that FIG. 1 shows only devices and apparatuses related to the focus detection apparatus and imaging apparatus of the present invention, and illustration and description of other apparatuses and devices are omitted. In the imaging apparatus according to the present embodiment, a lens barrel 2 is detachably attached to a camera body 1, and the lens barrel 2 can be replaced with a lens barrel incorporating various interchangeable lenses.

  The camera body 1 includes a main mirror 11, a sub mirror 12, a filter 13, a shutter 14, an image sensor 15, a focus detection device 16, a penta roof prism 17, an eyepiece lens 18, an electrical contact 19, a body drive control device 20, an LED 31, and a light projection lens. 32 etc. are provided. The filter 13 is a combination of an optical low-pass filter and an infrared cut filter. The shutter 14 controls the exposure state of the image sensor 15. The imaging element 15 is composed of a CCD, a CMOS, or the like, and converts the subject image formed by the photographing lens 21 into an electrical signal and outputs it. The focus detection device 16 detects the focus adjustment state of the taking lens 21, that is, the defocus amount. The body drive control device 20 includes a microcomputer (not shown), a ROM, a RAM, an A / D converter, and the like, and performs various camera calculations, sequence control, image sensor drive control, and the like. The LED 31 irradiates the sub mirror 12 with a light beam for detecting the stationary position via the light projection lens 32.

  On the other hand, the lens barrel 2 includes a photographing lens 21 (lenses 21a to 21e), a diaphragm 22, a lens drive control device 23, and the like. The lens drive control device 23 includes a microcomputer (not shown), a ROM, a RAM, a lens drive actuator, an aperture drive actuator, and the like, and adjusts the focus of the photographing lens 21 and the aperture of the aperture 22. The body drive control device 20 of the camera body 1 and the lens drive control device 23 of the lens barrel 2 are electrically connected via an electrical contact 19 provided at the mount portion of the interchangeable lens 2, and various information Give and receive.

  At the time of non-photographing, as shown by a solid line in FIG. 1, the main mirror 11 and the sub mirror 12 are placed in the photographing optical path, and part of the subject light transmitted through the photographing lens 21 is the main mirror 11, the penta roof prism 17, and the eyepiece 18. The subject image is visually recognized by the photographer. Further, the remaining part of the subject light is guided to the focus detection device 16 via the main mirror 11 and the sub mirror 12, and the focus detection state of the photographing lens 21, that is, the defocus amount is detected by the focus detection device 16.

  At the time of shooting, as indicated by a broken line in FIG. 1, the main mirror 11 and the sub mirror 12 are retracted from the shooting optical path, and a subject image is shot by the image sensor 15. The subject image signal output from the image sensor 15 is processed by an image processing device (not shown), and the subject image is recorded on a recording device such as a memory card (not shown).

  FIG. 2 is a diagram illustrating a configuration of a focus detection optical system incorporated in the imaging apparatus according to the first embodiment. The photographing lens 21 forms a subject image on the light receiving surface 15a of the image sensor 15 (see FIG. 1). A light beam (focus detection light beam) from the subject that has passed through the photographic lens 21 and the main mirror 11 (see FIG. 1) is reflected by the reflection surface 12a of the sub-mirror 12, and enters the planned focal plane 16a conjugate with the light receiving surface 15a of the image sensor. Led. Note that the focus of the photographic lens 21 is adjusted so that the subject image is focused on the planned focal plane 16a.

  In the focus detection device 16, a microlens array 52 and a light receiving element array 53 are enclosed in a package 55 covered with a cover glass 54.

  In a partial region of the reflection surface 12a of the sub mirror 12, a binary optical element 29 that reflects light of a predetermined wavelength at an angle different from the normal angle is formed. Details of the binary optical element 29 will be described later.

  When focus detection is performed using a focus detection light beam at a high image height, a field lens 51 is inserted between the vicinity of the planned focal plane 16a and a microlens array 52, which will be described later, so that the image height is high. You may make it bend the light beam of a part from an optical axis direction. In the following description, the field lens 51 is ignored.

  FIG. 3 is a perspective view of the microlens array 52 and the light receiving element array 53. The light receiving element array 53 is arranged in the very vicinity behind the microlens array 52, but in FIG. On the microlens array 53, a plurality of microlenses ML are two-dimensionally arranged around the optical axis position of the focus detection light beam indicated by a one-dot chain line. On the light receiving element array 53, a light receiving element group 531 in which a plurality of light receiving elements are two-dimensionally arranged is two-dimensionally arranged in a form corresponding to each microlens ML. In FIG. 3, 25 microlenses ML are arranged in 5 rows and 5 columns, and 25 light receiving element groups 531 are arranged in 5 rows and 5 columns corresponding to these microlenses. In this specification, an example in which a plurality of light receiving element groups 531 are arranged in association with each other for each microlens ML is shown, but a plurality of light receiving elements may be arranged two-dimensionally regardless of each microlens.

  In order to prevent stray light, a light-shielding mask is provided on the surface of the microlens array 52, and a light-shielding film is coated on the side surface. In FIG. 3, the light shielding mask and the light shielding film are indicated by oblique lines. A rectangular opening 522 of the light shielding mask is provided outside the region 521 where the microlenses ML are arranged. A portion of the microlens array 52 provided with the opening 522 is a parallel plate. In addition to the plurality of light receiving element groups 531 described above, a light receiving element group 535 in which a plurality of light receiving elements are arranged two-dimensionally exists at a position corresponding to the opening 522 on the light receiving element array 53. This light receiving element group 535 receives the position detecting light beam irradiated to the binary optical element 29 (see FIG. 2) on the surface of the sub mirror, that is, the light beam for detecting the secular change of the stationary position in the photographing optical path of the sub mirror 12. The signal corresponding to the submirror position is output.

  4 is a cross-sectional view showing cross sections A to A of the microlens array 52 and the light receiving element array 53 shown in FIG. A light-shielding mask 56 is provided on the surface of the microlens array 52 so as to cover a portion other than the microlens, and a light-shielding film 52 a is coated on the side surface of the microlens array 52. Further, in order to prevent crosstalk of incident light to the microlens ML, a light shielding partition 57 is provided along the boundary between the microlenses ML. These are formed by digging deep grooves in the glass microlens array 52 by etching or machining, filling them with light-shielding resin, and curing them.

  FIG. 5 is a diagram for explaining a focus detection method by the focus detection device 16 according to the first embodiment. FIG. 5 shows the microlens array 52 and the light receiving element array 53 in the AA cross section of FIG. 3 as in FIG. 4. However, for explanation, a state in which more microlenses ML and light receiving element groups 531 are arranged is shown. It is shown. In FIG. 5, illustration of the light shielding partition 57 (see FIG. 4) is omitted. In this embodiment, a set of one microlens ML and a light receiving element group corresponding to the microlens ML is referred to as one pixel. In FIG. 5, pixels having five light receiving elements per column are arranged for each microlens ML.

  The image of each light receiving element of the light receiving element array 53 by each microlens ML of the microlens array 52 is connected to the imaging surface 16b on the object side slightly from the apex of the microlens ML. This imaging plane 16b is configured to be in the vicinity of the planned focal plane 16a of the camera shown in FIG.

  The focus detection device 16 according to the first embodiment is a focus detection device based on a pupil division type phase difference detection method. That is, the defocus amount of the photographing lens 21 is detected based on the positional deviation amount of the pair of subject images formed by the pair of focus detection light beams that have passed through the pair of regions on the pupil plane of the photographing lens 21. A specific focus detection method will be described below.

  The first focus detection method is a method of detecting a defocus amount based on a positional shift amount of a pair of subject images detected by a light receiving element group of adjacent pixels or every other pixel. A pair of subject images formed on the light receiving element groups in the A row and the B row shown in FIG. 5 are “back projected images of the light receiving element groups by the microlenses” indicated by A ′ and B ′ on the imaging surface 16b. Corresponding to a pair of subject images formed by the imaging lens 21. Therefore, based on the outputs of the light receiving element groups in the A and B rows, the amount of positional deviation between the pair of subject images formed by the photographing lens 21 on the imaging surface 16b is detected.

  In the second focus detection method, a composite image represented by a waveform obtained by connecting the outputs of the nth light receiving elements from the ends of the light receiving element groups of the pixels arranged in succession, and the (n + m) th light receiving element outputs. In this method, the defocus amount is detected based on the amount of positional deviation from the composite image represented by the connected waveform. As shown in FIG. 5, an image corresponding to a signal sequence obtained by connecting the outputs of the second light receiving elements c from the left end of each light receiving element group of pixels arranged in succession, and the fourth light receiving element d from the left end. An image corresponding to the signal sequence in which the outputs are connected is a pair of images formed by the photographing lens 21 at the position of “back-projected image of light receiving element group by microlenses” indicated by C ′ and D ′ on the imaging surface 16b. Corresponds to the subject image. That is, the composite images represented by the output waveforms of the discrete light receiving element group C in which the light receiving elements c are connected and the discrete light receiving element group D in which the light receiving elements d are connected correspond to the subject images at positions C ′ and D ′, respectively. . Therefore, based on the outputs of the light receiving element group C and the light receiving element group D, the positional deviation amount of the pair of subject images formed by the photographing lens 21 on the image forming surface 16b is detected.

  FIG. 6 is a block diagram showing a detailed configuration of the focus detection device 16. The output of the light receiving element array 53 is converted into a digital signal by the A / D converter 54 and temporarily stored in the memory 55. The microcomputer 56 includes a composite signal sequence creation unit 56a, an image shift calculation unit 56b, and a defocus amount calculation unit 56c according to software form, reads output data of the light receiving element array 53 from the memory 55, and uses the composite signal sequence creation unit 56a. The first signal sequence {a (i)} = a (1), a (2), a (3),..., And the second signal sequence {b (i)} = b (1), b (2 ), B (3),...

  Here, in the case of the first focus detection method described above, the signal sequences {a (i)} and {b (i)} are the light receiving elements of the light receiving element groups of the adjacent pixels A and B shown in FIG. A sequence of outputs. Further, in the case of the second focus detection method described above, the signal sequences {a (i)} and {b (i)} are arrays of outputs of the light receiving element groups C and D shown in FIG.

Based on the first signal sequence {a (i)} and the second signal sequence {b (i)} obtained in this way, an image shift calculation is performed by a known method to calculate a defocus amount. A method of calculating a defocus amount from two signal sequences {a (i)} and {b (i)} is well known. First, a first signal sequence {a (i)} and a second signal sequence {b (i)} The correlation amount C (N) of the corresponding pair of images is obtained from (i = 1, 2, 3,...).
C (N) = Σ | a (i) −b (j) | (1)
In the equation (1), j−i = N, and N is the number of shifts. Further, Σ represents a total calculation of a predetermined range related to i.

The shift amount is obtained from the correlation amount C (N) obtained discretely by the equation (1) as follows. Here, among the correlation amounts C (N), the correlation amount giving a minimum value when the shift amount N = N0 is C0, the correlation amount in the shift amount (N0-1) is Cr, and the correlation amount in the shift amount (N0 + 1). Let the amount be Cf. A precise shift amount Na is obtained from the arrangement of the correlation amounts Cr, C0, and Cf.
DL = 0.5 · (Cr−Cf) (2),
E = MAX {(Cf−C0), (Cr−C0)} (3),
Na = N0 + DL / E (4)
Next, a correction amount (constant CONST) corresponding to the position of the focus detection surface is added to the shift amount Na to calculate an image shift amount Δn = Na + CONST on the focus detection surface. Further, the defocus amount Df is calculated by multiplying the image shift amount Δn by a constant Kf depending on the detected opening angle.
Df = Kf · Δn (5)

  FIG. 7 is a front view of the sub mirror 12 as viewed from the LED 31. As shown in FIG. 7, the reflecting surface 12a of the sub mirror 12 is roughly divided into two regions 12c and 12d. The region 12c is a region used for focus detection. Of the subject light transmitted through the photographing lens 21, the light beam incident on the region 12c is used for focus detection. A vertical and horizontal broken line intersection 12e drawn in the area 12c is the center of the area 12c, and the sub mirror 12 is installed so that the position of the intersection 12e substantially coincides with the optical axis position of the photographing lens 21. On the other hand, the region 12d is a region used for detecting the position of the submirror 12, and the LED 31 irradiates the region with a position detecting light beam. A binary optical element 29 is formed in the region 12d of the reflecting surface 12a.

  FIG. 8 is a diagram showing how the position of the sub mirror 12 is detected by the position detection light beam. The binary optical element 29 formed on the reflecting surface 12a of the sub mirror 12 has a function of reflecting light having a specific wavelength in a direction different from the normal direction due to a diffraction effect. In addition, the LED 31 has a light emission characteristic including many wavelengths at which the diffraction effect by the binary optical element 29 works.

  The light emitted from the LED 31 enters the binary optical element 29 via the light projecting lens 32. Most components of this light are reflected toward the focus detection device 16 by the diffraction effect. In FIG. 8, the center of this light beam is represented by L2. Of the light irradiated to the binary optical element 29 by the LED 31, the components other than the specific wavelength component described above are reflected in the same manner as normal reflection by the reflection surface 12 a of the sub mirror 12, and go to the outside of the focus detection device 16. Therefore, this light becomes stray light in the focus detection device 16 and does not adversely affect the focus detection.

  The light beam reflected in the direction of the focus detection device 16 by the diffraction effect passes through the opening 522 (see FIG. 3) of the microlens array 52 and enters the light receiving element group 535 (see FIG. 3) provided in the light receiving element array 53. To do. At this time, an image of the light emitting portion of the LED 31 can be formed on the light receiving element group 535 by the lens action of the light projecting lens 32.

  Note that a part of the subject light may enter the binary optical element 29, but wavelength components other than the specific wavelength described above in this light are reflected in the same manner as other regions on the reflection surface 12a. Further, the specific wavelength component included in this light is reflected to the outside of the focus detection device 16 by the action of the binary optical element 29. Therefore, the subject light incident on the binary optical element 29 is not generated in focus detection.

  FIG. 9 is a plan view showing a state in which the position detection light beam is incident on the light receiving element group 535 on the light receiving element array 53. FIG. 9 is a view of the light receiving element array 53 as viewed from the sub-mirror 12 side. The arrows B and F in FIG. 9 indicate the same direction as the arrows B and F in FIG. Similarly, the position X in FIG. 9 represents the same position as the position X in FIG. When the sub-mirror 12 is at a position determined at the time of shipment from the factory, the position detection light beam enters the position X in FIG. Further, the incident range 61 of the position detecting light beam is wide across a plurality of light receiving elements. When the stationary position of the sub mirror 12 shifts in the direction U in FIG. 8 due to secular change, the position where the position detection light beam enters moves in the direction F in FIG. 9 by a magnitude corresponding to the shift amount of the sub mirror 12. On the other hand, when the stationary position of the sub mirror 12 is shifted in the direction D of FIG. 8, the stationary position detecting light beam moves in the direction B of FIG. 9 by a magnitude corresponding to the amount of displacement of the sub mirror 12.

  The microcomputer 56 included in the focus detection device 16 detects the incident position of the position detection light beam from the output of the light receiving element group 535. This detection result represents a secular change in the stationary position of the sub mirror 12. The body drive control device 20 (see FIG. 1) compares the incident position of the position detecting light beam at the time of shipment from the factory with the incident position detected during use of the imaging apparatus of the present embodiment, and according to the difference. The focus correction value is obtained by referring to a previously stored table or by performing a predetermined calculation. Then, the defocus amount output from the microcomputer 56 is corrected using the obtained correction value, and the focus detection result of the photographing lens 21 without the focus detection error due to the secular change of the stationary position in the photographing optical path of the sub mirror 12 is obtained. Get.

  The processing for detecting the stationary position of the sub-mirror 12 described above is performed when the user of the imaging apparatus instructs execution of processing using an operation member (not shown). At this time, it is desirable that light entering the photographing lens 21 is blocked by a lens cap or the like. This is to prevent light from the subject from becoming harmful light for detecting the stationary position of the submirror. The body drive control device 20 stores the focus correction value obtained by the above-described process in a non-volatile storage device (not shown), and performs correction using the focus correction value stored each time the microcomputer 56 outputs the defocus amount. Do.

According to the imaging apparatus according to the first embodiment described above, the following operational effects can be obtained.
(1) The body drive control device 20 corrects the defocus amount based on the output obtained by the light receiving element array 53 receiving the stationary position detecting light beam. Thereby, the error due to the secular change of the sub mirror 12 can be corrected.

(2) The direction in which the binary optical element 29 formed on the reflecting surface 12a of the sub mirror 12 reflects light of a specific wavelength is determined by the shape of the binary optical element. Therefore, by appropriately designing the shape of the binary optical element, the degree of freedom of the position of the LED 31 in the camera body 1 is increased without limiting the direction of incident light with respect to the binary optical element.

(3) The binary optical element 29 is provided in a region 12d of the reflecting surface 12a of the sub mirror 12 that is different from the region 12c where the focus detection light beam is incident. Thereby, the stationary position of the sub mirror 12 can be detected without reducing the area used for focus detection.

  In the first embodiment described above, the light beam for detecting the stationary position of the sub mirror 12 is received by the light receiving element group 535 without passing through the microlens ML. In the second embodiment described in detail below, the stationary position detection light beam is received through the microlens ML in the same manner as the focus detection light beam. In the following description, parts that are the same as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

(Second Embodiment)
FIG. 10 is a diagram showing the microlens array 62 and the light receiving element array 63 according to the present embodiment. As shown in FIG. 10, in the present embodiment, the microlens array 62 does not have a rectangular opening that transmits the position detection light beam. Similar to the focus detection light beam, the light beam enters the microlens ML of FIG. 10 and is received by the plurality of light receiving element groups 531. The microcomputer 56 included in the body drive control device 20 of the present embodiment detects the incident position of the position detection light beam incident on the plurality of light receiving element groups 531 and, similarly to the first embodiment, according to the detection result. Correct the defocus amount.

  FIG. 11 is a diagram for explaining a sub-mirror position detection method according to the second embodiment. 11A and 11B show cross sections A to A of the microlens array 62 and the light receiving element array 63 shown in FIG. The light projecting lens 32 is set so that the light emitted from the LED 31 toward the sub mirror 12 is connected to the imaging surface 16b. By setting in this way, an image of the light emitting portion of the LED 31 can be formed on the light receiving element array 63.

  FIG. 11A illustrates a state in which light emitted from the LED 31 is incident directly on the light receiving element group 531b through the light projecting lens 32. As shown in FIG. 11A, at this time, the light emitted from the LED 31 is detected by the three light receiving element groups 531a, 531b, and 531c. The microcomputer 56 included in the body drive control device 20 detects the position where the light beam for stationary position detection of the sub mirror 12 is incident by the output of these light receiving elements.

  In FIG. 11A, when the stationary position of the sub mirror 12 in the photographing optical path changes due to secular change, for example, when the position detection light beam moves in the direction of the arrow SS1 in FIG. The position where the light passing through the lens array 62 enters moves in the direction of the arrow SS2. If the position detecting light beam moves in the direction of arrow SS1 by a certain amount or more, light will not enter the light receiving element group 531a. However, the state where light is incident on the light receiving element groups 531b and 531c is still maintained.

  FIG. 11B shows a state where the position detection light beam has moved in the direction of arrow SS1 by half the width of the microlens ML in FIG. In FIG. 11B, as described above, the light incident position on the light receiving element array 63 moves in the direction of the arrow SS2, and no light enters the light receiving element group 531a, but the light receiving element group 531b. , 531c can detect the incident position of the position detecting light beam. When the position detecting light beam further moves in the direction of the arrow SS1, light also enters the light receiving element group 531d. When the position detecting light beam is moved by just the width of the microlens ML from FIG. 11A, FIG. The light enters the light receiving element groups 531b, 531c, and 531d in the same manner as the light incident on the light receiving element groups 531a, 531b, and 531c in FIG.

  As described above, even if the position where the position detection light beam of the sub mirror 12 is connected to the imaging surface 16b is directly above the microlens ML, or directly above the light shielding mask 56 existing between the microlenses. However, the state where the incident position of the position detecting light beam can be detected by any one of the light receiving element groups is maintained.

  In the example of FIG. 11, the position detecting light beam that has passed through the microlens ML is always incident on two or more light receiving element groups. However, if light is incident on at least one light receiving element group. It is possible to detect the incident position of the position detecting light beam. That is, the angle Dt shown in FIG. 11A is larger than the spread of the position detection light beam that is at least necessary for detecting the incident position. Actually, the angle may be a little more than two-thirds of the angle Dt, that is, an angle having a spread of slightly more than twice the width of the microlens ML on the microlens array 62. In this case, in FIG. 11A, although the light incident on the light receiving element groups 531a and 531c is half cut, the incident position of the position detecting light beam can be detected. In FIG. 11, the lower part of the microlens ML is drawn larger than the actual size for the sake of explanation, but in reality, the distance between the imaging surface 16b and the microlens array 62 is several tens of times the width of the microlens ML. It is easy to provide the detection light beam with the above-mentioned spread.

According to the imaging apparatus according to the second embodiment described above, the following functions and effects can be obtained in addition to the functions and effects obtained by the imaging apparatus according to the first embodiment.
(1) The stationary position detecting beam of the sub mirror 12 is received by the light receiving element that receives the focus detecting beam, and the stationary position of the sub mirror 12 is detected. Thereby, the microlens array and the light receiving element array are simplified, and the manufacturing cost can be reduced.

  In the second embodiment described above, the irradiation light of the LED 31 is used only for correcting the influence of the sub-mirror 12 due to aging. In the third embodiment described in detail below, the vibration state of the sub mirror 12 is detected using the irradiation light of the LED 31. In the following description, parts common to the second embodiment described above are denoted by the same reference numerals and description thereof is omitted.

(Third embodiment)
As shown in FIG. 1, the imaging apparatus according to the present embodiment performs focus detection in a state where the main mirror 11 and the sub mirror 12 are on the imaging optical path, and then retracts the main mirror 11 and the sub mirror 12 from the imaging optical path. Exposure. Therefore, focus detection cannot be performed during exposure.

  When continuous shooting is performed using the image pickup apparatus according to the present embodiment, a series of processes such as focus detection, retraction of the mirror group including the main mirror 11 and the sub mirror 12, exposure, and return of the mirror group are repeated at short time intervals. It is. Assuming that the exposure time is constant, the shorter the time required for operations other than focus detection, the longer the time that can be spent on focus detection and the higher the accuracy of focus detection. In other words, the shorter the time from when the mirror group is restored to when the focus detection starts, the better.

  In the configuration of the main mirror 11 and the sub mirror 12 as shown in FIG. 1, the retracted sub mirror 12 is returned to the photographing optical path together with the mirror down operation of the main mirror 11. When the main mirror 11 performs the mirror down operation, the sub mirror 12 that overlaps the main mirror 11 in the retracted state is opened from the main mirror 11 by the spring force. A sub-mirror receiving part (not shown) integrally joined with the sub-mirror 12 collides with a not-shown limiting member such as a pin in the camera body 1 and stops, and the sub-mirror 12 stops at a predetermined position in a predetermined posture. .

  When the sub mirror 12 is opened from the main mirror 11, the sub mirror 12 may collide with the limiting member and bounce off, and may vibrate for a while until it stops. While the sub mirror 12 is vibrating, the light reflected by the sub mirror 12 and incident on the focus detection device 16 also vibrates, so that accurate focus detection cannot be performed. Therefore, it is necessary to wait until the vibration of the sub mirror 12 is settled before performing focus detection.

  In the imaging apparatus according to the present embodiment, the LED 31 is turned on when the mirror down operation of the main mirror 11 is started, and after the mirror down operation, the microcomputer 56 detects the vibration state of the sub mirror 12 based on the output of the light receiving element array 63. Then, when it is detected that the sub-mirror 12 is not vibrating, the LED 31 is turned off, and focus detection by the focus detection device 16 is performed.

According to the imaging apparatus according to the third embodiment described above, the following functions and effects can be obtained in addition to the functions and effects obtained by the imaging apparatus according to the second embodiment.
(1) The microcomputer 56 detects that the sub mirror 12 is oscillating based on a change in the incident position of the position detecting light beam on the light receiving element array 63. Thereby, the timing for performing focus detection can be accurately determined.

(Modification 1)
As a modification of the third embodiment, a configuration in which the sub-mirror angle detection configuration similar to that of the second embodiment is the same as that of the first embodiment can be used. It should be noted that, in both the third embodiment and its modification, it is desirable to take the same countermeasures as the “first countermeasure” and “third countermeasure” in modification 5 described later in detecting the vibration state of the submirror. .

(Modification 2)
As a modified example of the second focus detection method, as shown in FIG. 12, a signal sequence obtained by adding the first and second light receiving element outputs from the end of each light receiving element group of continuously arranged pixels, that is, Based on the output waveform of the light receiving element group C connected with the combined light receiving element c and the signal sequence obtained by adding the fourth and fifth light receiving element outputs from the end, that is, the output waveform of the light receiving element group D connected with the combined light receiving element d. Alternatively, the positional deviation amount of the pair of subject images formed by the photographing lens 21 on the image forming surface 16b may be detected. That is, the outputs of a plurality of adjacent light receiving elements may be combined into a single light receiving element output. Furthermore, as disclosed in Japanese Patent Application Laid-Open No. 2008-116616, the outputs of the light receiving unit groups having various arrangements may be added.

(Modification 3)
Instead of providing the binary optical element 29 on the reflecting surface 12 a of the sub mirror 12, the position detection light beam emitted by the LED 31 may be guided to the focus detection device 16. For example, as shown in FIG. 13, the LED 31 emits light to the back surface of the main mirror 11, and the light reflected by the back surface of the main mirror 11 is reflected by the reflection surface 12 a of the sub mirror 12 and enters the focus detection device 16. The camera body 1 may be configured as follows.

(Modification 4)
A diffractive optical element having an imaging effect equivalent to that of a concave mirror may be provided on the reflecting surface 12 a of the sub mirror 12 instead of the binary optical element 29. In this case, the light projecting lens 32 can be omitted.

(Modification 5)
As a modification of the first embodiment, the position of the sub mirror 12 may be automatically detected regardless of the user operation. For example, the position detection of the sub mirror 12 may be performed when the imaging device is first activated after a predetermined number of days have passed since the position detection of the sub mirror 12 was last performed. In this case, in order to prevent the subject light from entering the light receiving element group 535 and interfering with the position detection of the sub mirror 12, it is desirable to implement one of the following measures or a combination of a plurality of measures.

  As a first countermeasure, the LED 31 emits light sufficiently brighter than the luminance of the subject captured by the image sensor 15 or the like. In this case, since the subject light incident on the light receiving element group 535 has a lower luminance than the position detection light beam, the influence of interference by the subject light is relatively small.

  As a second countermeasure, when the position detection of the sub mirror 12 is executed, the aperture 22 in the lens barrel 2 is reduced to a small diameter. As a result, the light transmitted through the opening 522 has only a large incident angle, that is, a light that is greatly inclined, so that the subject light does not enter the light receiving element group 535.

  As a third countermeasure, the light receiving element group 535 is covered with a filter that blocks wavelength components other than the emission wavelength of the LED 31. When a diffractive optical element such as the binary optical element 29 is used, the diffractive optical element may be a filter that blocks components other than the wavelength component that provides a deflection effect.

(Modification 6)
As shown in FIG. 7, instead of preparing a region where the position detection light beam of the sub mirror 12 is incident only on one side of the sub mirror 12, regions where the position detection light beam is incident on both sides of the sub mirror 12 are provided. 32 and two light receiving element groups 535 may be provided. By performing position detection using the regions on both sides of the submirror 12, it is possible to improve the accuracy of position detection by averaging the position detection results, and also when the submirror 12 is twisted and deformed, This can be detected by comparing the detection results. Further, the center of gravity position in the left-right direction of the main mirror 11 and the sub mirror 12 substantially coincides, and the balance when operating these mirrors is improved.

(Modification 7)
The light receiving element group 535 into which the position detection light beam is incident may not be a two-dimensional array of light receiving elements, but a one-dimensional array. When arranged in two dimensions, the incident position of the stationary position detecting light beam can be detected more precisely. On the other hand, when arranged in a one-dimensional manner, the area of each light receiving element can be made relatively large, and sensitivity can be obtained even for light of lower luminance.

(Modification 8)
In FIG. 3 and FIG. 10, the light receiving element groups 531 and 535 are arranged separately from each other on the light receiving element array, but some or all of them may be continuous.

(Modification 9)
In the second embodiment, the position detection light beam of the sub mirror 12 is incident on the light receiving element for focus detection. However, the position detection light beam is independent because the position detection light beam is detected via the microlens ML. The light may be incident on a light receiving element group prepared in the above manner.

  As long as the characteristics of the present invention are not impaired, the present invention is not limited to the above-described embodiments, and other forms conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention. .

12 Sub mirror 12a Reflecting surface 16 Focus detection device 20 Body drive control device 21 Shooting lens 29 Binary optical element 31 LED
32 Projection lenses 52 and 62 Micro lens arrays 53 and 63 Light receiving element array 535 Light receiving element group for sub mirror position detection

Claims (9)

A reflecting member that reflects the first light beam transmitted through the optical system in a predetermined direction;
A light receiving means for receiving reflected light of the light reflected by the reflecting member;
Focus detection means for detecting a focus state of the optical system based on a signal obtained by receiving the reflected light by the light receiving means and outputting a detection signal;
A light source that irradiates the reflecting member with a second light flux different from the first light flux;
A focus detection apparatus comprising: correction means for correcting the detection signal based on an output obtained by receiving the second light beam reflected by the reflection member by the light receiving means. The focus detection apparatus according to claim 1,
The second light flux includes light of a specific wavelength;
The focus detection apparatus, wherein the reflection member includes a diffractive optical element that reflects light having a specific wavelength of the second light beam toward the light receiving unit. The focus detection apparatus according to claim 2,
The focus detection apparatus according to claim 1, wherein the diffractive optical element is provided in a region different from a region where the first light beam is incident on a reflection surface of the reflection member. The focus detection device according to any one of claims 1 to 3,
The light receiving means has a plurality of light receiving elements arranged,
The focus detection apparatus corrects the focus state based on a position of a light receiving element that receives the second light flux reflected by the reflecting member among the plurality of light receiving elements. The focus detection apparatus according to claim 4,
A focus detection apparatus comprising: a vibration detection unit configured to detect that the reflection member vibrates based on a change in a position of the light receiving element that receives the second light flux. The focus detection apparatus according to claim 5,
The focus detection device, wherein the focus detection unit prohibits detection of the focus state when the vibration detection unit detects that the reflection member is vibrating. The focus detection device according to any one of claims 1 to 6,
The light receiving means is
A microlens array in which a plurality of microlenses are arranged, and a light receiving element array in which a plurality of light receiving elements are arranged with respect to the microlens array, and the first light flux is received through each of the microlenses. A first light receiving portion;
And a second light receiving portion for receiving the second light flux. The focus detection apparatus according to claim 7,
The focus detection apparatus, wherein the second light receiving unit receives the second light flux through the microlens array.   An imaging apparatus comprising the focus detection apparatus according to claim 1.

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