JP2005099608A - Automatic focusing camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic focusing camera that can cope with problems related to automatic focusing such as image loss that occurs at the time of switching between a photographing optical path and a finder optical path and that needs no extra space nor increased cost. <P>SOLUTION: The image of an object 13 reflected on the main mirror 15 is picked up by an area sensor 16. Then, while the main mirror 15 is moved by an actuator 17, a change in the image of the object 13 on the area sensor 16 is detected by a contrast judgement section 18. On the basis of the change in the object image so detected, the focusing direction or the focusing position of a photographic lens 14 is controlled by the CPU 20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an improvement in focusing technology for a so-called digital single-lens reflex camera.

  In general, a single-lens reflex camera (hereinafter abbreviated as a single-lens reflex camera) is configured to be able to observe a subject image incident from a photographing lens so that various conversion lenses can be used. In addition, a special image sensor is often used because descriptive properties such as extremely high gradation expression and resolving power are required.

  For these reasons, the photographing optical path and the framing finder optical path are generally designed separately. However, when switching these optical paths, there are problems such as disappearance of an image from the finder optical path.

In addition, in a digital camera, a method of focusing is usually used by a contrast signal of a subject image on an image sensor. However, with this method, it is necessary to finely drive the photographic lens, and time lag is likely to occur. In order to solve the occurrence of this time lag, a technique of providing a special optical path splitting element is known (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 9-181954

  However, since the technique described in Patent Document 1 described above requires a special optical member or actuator, there is a demerit that a space for that is required and the cost is increased.

  Therefore, the present invention provides an autofocus camera that eliminates the problem of autofocus such as image disappearance that occurs when the optical path between the photographing optical path and the finder optical path is switched, and that does not require extra space and does not increase cost. The purpose is to do.

  Therefore, the invention described in claim 1 is a detection that detects a change in the subject image by the imaging element while moving the movable mirror, an imaging element that captures the subject image reflected by the movable mirror, and the movable mirror. And a focus control means for determining a focus direction or a focus position of the photographic lens based on a subject image change detected by the detection means.

  By adopting such a configuration, it is possible to take measures against autofocusing such as image disappearance that occurs when the optical path between the photographing optical path and the finder optical path is switched, and an auto that does not require extra space and does not increase the cost. A focus camera can be provided.

  According to a second aspect of the present invention, in the first aspect of the present invention, the movable mirror is disposed in the photographing optical path, and a first position for guiding the subject image in the viewfinder direction and retreating from the photographing optical path. It is possible to move to the second position.

  With this configuration, the movable mirror that is lighter and smaller than the photographic lens is moved, so that the mechanism system can be downsized.

  According to a third aspect of the invention, in the first aspect of the invention, the focus control means is based on a change in the contrast signal of the subject image signal accompanying a change in the optical path length due to the movement of the movable mirror. The focusing direction is determined.

  With this configuration, the time required for focusing can be shortened.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, the camera further includes a lens driving unit that moves the photographing lens in the focusing direction determined by the focus control unit. To do.

  By adopting such a configuration, it is possible to provide an autofocus camera that does not require a new extra space and does not increase the cost.

  According to a fifth aspect of the present invention, there is provided a reflecting member that guides a subject image light beam incident through a photographing lens to an image pickup device, an angle control unit that controls an angle of the reflecting member, and the angle controlling unit that controls the photographing lens. Determining means for determining the focus of the photographing lens based on a change in contrast of the subject image at the switched plurality of incident positions. It is characterized by.

  By adopting such a configuration, it is possible to take measures against autofocusing such as image disappearance that occurs when the optical path between the photographing optical path and the finder optical path is switched, and an auto that does not require extra space and does not increase the cost. A focus camera can be provided.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the camera further includes a lens driving unit that moves the photographing lens to adjust the focus of the photographing lens in accordance with a determination result of the determination unit. It is characterized by that.

  By adopting such a configuration, it is possible to provide an autofocus camera that does not require a new extra space and does not increase the cost.

  A seventh aspect of the present invention is a phase difference type autofocus in which an image signal of a subject is guided to a pair of sensors by using a first reflecting mirror that can be retracted from the optical path using different optical paths of the photographing lens; According to the present invention, there are two autofocus methods, that is, an autofocus method of detecting a change in contrast by switching the optical path length according to the position of the second reflecting mirror interlocked with the first mirror.

  By adopting such a configuration, it is possible to take measures against autofocusing such as image disappearance that occurs when the optical path between the photographing optical path and the finder optical path is switched, and an auto that does not require extra space and does not increase the cost. A focus camera can be provided.

  The invention described in claim 8 is characterized in that, in the invention described in claim 7, the phase difference method is used before the optical path of the first mirror is retracted, and the contrast method is used during the retracting.

  By adopting such a configuration, it is possible to take measures against autofocus problems such as image disappearance that easily occur when the optical path between the photographing optical path and the finder optical path is switched without using a new type of autofocus.

  According to a ninth aspect of the present invention, there is provided a photographing lens, a reflecting member that reflects a light beam from a subject image incident through the photographing lens, and an imaging that forms a light beam of the subject image reflected by the reflecting member. An optical path length changing means for changing an optical path length from the photographing lens to the imaging element; a detecting means for detecting an incident position of the subject image changed by the optical path length changing means on the imaging element; Determining means for determining a focusing position of the photographing lens based on a change in the subject image detected by the detecting means.

  By adopting such a configuration, it is possible to take measures against autofocusing such as image disappearance that occurs when the optical path between the photographing optical path and the finder optical path is switched, and an auto that does not require extra space and does not increase the cost. A focus camera can be provided.

  According to a tenth aspect of the present invention, in the ninth aspect of the invention, the lens driving unit further moves the photographic lens to adjust the focus of the photographic lens in accordance with the determination result of the determination means. It is characterized by that.

  By adopting such a configuration, it is possible to provide an autofocus camera that does not require a new extra space and does not increase the cost.

  According to an eleventh aspect of the present invention, in the invention according to the ninth aspect, the optical path length changing means moves the reflecting member along an optical axis direction of the photographing lens.

  With such a configuration, the reflecting member that is lighter and smaller than the photographic lens is moved, so that the mechanism system can be downsized.

  According to a twelfth aspect of the present invention, in the invention according to the ninth aspect, the optical path length changing means controls the angle of the reflecting member to change the incident position of the subject image on the image sensor. It is characterized by.

  By adopting such a configuration, it is possible to provide an autofocus camera that does not require a new extra space and does not increase the cost.

  The autofocus camera according to the present invention effectively utilizes the optical path switching optical system and drive system of a single-lens reflex camera to prevent loss of focus information when switching the optical path unique to a single-lens reflex camera, and can support high-speed shooting. It is what.

  Further, the present invention can be applied not only to a single-lens reflex camera but also to a photographing apparatus having an optical path switching optical system, and is used as focusing information using contrast information that changes due to an optical path change caused by switching of the optical path. .

  According to the present invention, an autofocus camera that eliminates the problem of autofocus such as loss of an image that occurs when the optical path between the photographing optical path and the finder optical path is switched, does not require extra space, and does not increase the cost. Can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

  In general, in many digital cameras, as shown in FIG. 2, an image of a subject 1 is received by an image sensor (imager) 3 through a photographing lens 2. The contrast of the image signal obtained here is determined by the microcontroller (CPU) 5 from the output of the contrast determination unit 4. The CPU 5 controls the position of the photographic lens 2 via a lens drive (LD) control circuit 6.

  That is, the contrast change as shown in FIG. 3 is obtained depending on the lens driving position. Accordingly, if the lens drive control is stopped at the position where the contrast change peaks, the subject 1 can be focused. This method is generally called a hill-climbing method because it searches for a contrast peak.

  However, in such a hill-climbing method, it is necessary to move the photographic lens 2. For example, in a system that shoots using various lenses such as a single-lens reflex camera, complicated control according to the characteristics of the lens when driving the lens. Is required. Therefore, a known phase difference type autofocus (AF) method (hereinafter referred to as a phase difference AF method), which is different from the method described above, is often employed.

  In this phase difference AF method, as shown in FIG. 4, the pupil of the photographing lens 2 is divided, and subject images passing through different optical paths are monitored by the lenses 7a and 7b, and the photographing lens 2 is in focus. Then, it is detected using the sensor arrays 8a and 8b that a predetermined positional relationship is obtained.

  Further, in this phase difference AF method, as shown in FIG. 5, the mirror 10 is provided between the photographing lens 2 and the image sensor 9, the optical path is bent, and the image is guided to the lens 7 and the sensor array 8. It is necessary to do so. Therefore, the mirror 10 is configured to be retracted from the optical path during photographing.

  As described above, both the hill-climbing method shown in FIG. 2 and the phase difference AF method shown in FIG. 4 have various advantages and disadvantages.

  FIG. 1 is a schematic block diagram of an AF optical system of a camera according to an embodiment of the present invention.

  In FIG. 1, an image of a subject 13 is guided to an area sensor 16 that is an image sensor by a photographing lens 14 and a mirror (movable mirror) 15 that is a reflecting member. The position of the mirror 15 is freely movable by 15 F and 15 N by an actuator 17 and functions as an optical path length changing means. The contrast obtained by the area sensor 16 is determined for contrast change by a contrast determination unit 18 including a function as a detection unit. The microcontroller (CPU) 20 controls the movement of the position of the photographing lens 14 via a lens drive (LD) control circuit 21 as a lens drive unit according to the determination result of the contrast determination unit 18 as a focus control unit and a determination unit. To do.

In the hill-climbing AF method shown in FIG. 2, the position of the taking lens 2 is moved to obtain a contrast change as shown in FIG. 3, but in this invention, the position of the mirror 15 is changed to 15F and 15N using the actuator 17. I try to let them. Thus, by changing the optical path, the image I _m1 due to the optical path of the lens retracting state, the image I _m2 by lens extension state corresponding optical path, and is the in image I _m0 to the lens position of the current are compared, the contrast determination A change in contrast is determined by the unit 18. In accordance with this determination result, the CPU 20 determines in which direction the photographing lens 14 is to be moved, and the lens drive control circuit 21 is controlled.

  That is, the CPU 20 performs focusing control by executing a sequence as shown in FIG.

That is, first, in step S1, the image I _m0 at the initial position is detected. Next, in step S2, the actuator 17 is driven to change the position of the mirror 15 (15 → 15F). In step S3, an image _Im1 obtained at the position of the moved mirror is detected.

Subsequently, in step S5, the actuator 17 is driven, and the position of the mirror 15 is changed again (15N). In step S6, an image _Im2 obtained at the position of the moved mirror is detected. Thereafter, the actuator 17 is stopped in step S7.

Here, in step S8, it is determined whether or not the value of the image _Im0 manually detected in step S1 is the maximum (MAX). When the value of the image I _m0 is not the maximum, the contrast of either the image I _m1 or I _m2 is higher than the value of the image I _m0 . Therefore, the process proceeds to step S9, and it is determined whether the photographing lens 14 is retracted or extended from the values of the images I _m1 and I _m2 .

In other words, towards the value of the image I _m1 is higher than the value of the image I _{m @ 2,} the detected position of the image I _m1 is the maximum contrast. Therefore, the process proceeds to step S10, the lens drive control circuit 21 is driven, and the taking lens 14 is retracted. On the other hand, towards the value of the image I _m2 is higher than the value of the image I _m1, the detected position of the image I _m2 becomes the maximum contrast. Therefore, in this case, the process proceeds to step S11, and the photographing lens 14 is extended by the drive control of the lens drive control circuit 21.

  Then, when the retraction or extension of the taking lens 14 in step S10 or S11 is completed, the process proceeds to step S1 and the above-described sequence is repeated.

In step S8, if the value of the image I _m0 has the highest contrast, it is determined that the image is not largely out of focus, and the process proceeds to step S12 where fine adjustment of the focus is performed. This is because the amount of adjustment of the photographic lens 14 is calculated by the amount of contrast of the images I _m1 and I _m2 and the amount of adjustment is determined.

  Further, the drive amount of the actuator 17 in step S2 may be switched based on the comparison result in step S9. At this time, for example, if any image has a low contrast, the drive amount is increased.

  That is, in the present invention, the contrast change can be determined by controlling a mirror that is lighter and smaller than the lens. Further, as the area sensor 16, an image sensor may be used as it is, and the optical path length change ΔL and the image change as compared with the method of repeatedly reading out signals at the same location of the imager as in the hill-climbing AF method of FIG. 2 described above. Is characterized by being able to synchronize and read out at higher speed.

  That is, in the general method, as shown in FIG. 7 (a), only the part 9a of the image sensor (imager) 9 is used. Therefore, as shown in FIG. It is necessary to reset the image signal. On the other hand, in the present invention, as shown in FIG. 7B, the readout is performed by using the other locations 16a, 16b, and 16c of the area sensor 16, so that the charge accumulation control is performed as shown in FIG. It can be done independently as shown in b). Therefore, continuous reading can be performed without resetting.

  As described above, high-speed focus control is possible regardless of the mounted lens.

  FIG. 9 is a diagram showing an example in which the AF method based on such a concept is applied to a single-lens reflex camera.

  Between the photographic lens 14 and the first image pickup device (imager) 22 disposed behind the photographic lens 14 on the optical axis, there is a reflecting member that can be inserted into and retracted from the photographic optical path. A rotatable mirror (main mirror) 15 as a changing means is provided. The angle of the mirror 15 is controlled around an axis of rotation 25 by an angle control means including an actuator 23 and a CPU 20, and the mirror 15 is rotatable. The photographing lens 14 can be moved in the optical axis direction by the CPU 20 and the lens drive control circuit 21.

  The contrast determination unit 18, the CPU 20, the lens drive control circuit 21, the actuator 23, and the finder circuit 24 are shown only in FIG. 9A and not shown in FIGS. 9B and 9C. These are omitted in order to avoid complication of the drawings, and in fact, the same configuration as that of FIG. 9A is made in FIGS. 9B and 9C.

  At the time of photographing, photographing is performed by forming an image of the subject 13 on the image sensor 22 with light through the photographing lens 14, and prior to that, the subject is observed as shown in FIG. As described above, the image of the subject 13 guided through the photographing lens 14 is guided to a second imaging device (imager) 16 for observing the subject disposed above the mirror 15.

  A signal is sent from the second imager 16 to the finder circuit 24 so that the photographer can confirm the composition. The finder circuit 24 is composed of a display system such as an LCD monitor, but the display system and the second imager 16 need not have the same resolution as the first imager 22. Rather, the design is such that priority is given to speed for transmitting the imaging result in real time, and the first imager 22 has different characteristics.

  The first imager 22 is a so-called megapixel imager having a high pixel count, and is designed to withstand a photograph in which an imaging signal is enlarged to a large size. If this element is used in a display system as it is, thinning readout or the like is required for the display mode, and the configuration may be complicated by special control. In this embodiment, based on such a concept, two types of the first imager 22 and the second imager 16 are prepared, and the second imager 16 for the finder is used to output the contrast as a detection means. The image is input to the determination unit 18, and contrast AF, which is a feature of the present invention, is performed.

The distance from the photographic lens 14 to the main mirror 15 is L ₁ , and the distance from the main mirror 15 to the two imagers 22 and 16 is both equal to L ₂ .

Therefore, in the state shown in FIG. 9A, if the image incident on the second imager 16 is in focus, the optical path at this time has a length of L ₁ + L ₂ . In addition, even when the main mirror 15 shown in FIG. 9B is retracted, the optical path L ₀ becomes L ₁ + L ₂ , and the photographing image sensor (first imager) 22 is also focused. Yes.

In the case of a single-lens reflex camera, since there is such a main mirror retracting configuration, as shown in FIG. 9C, when the main mirror 15 is raised upward by an angle θ from the state shown in FIG. The light (arrow) incident on the second imager 16 from the subject 13 leads the image to a position shifted laterally by d on the second imager 16. This shift amount d is determined by the following equation (1).

At this time, according to the distance h from the rotation axis 25 of the main mirror 15 to the photographing optical axis and the distance L ₂ from the center of the main mirror 15 to the center of the second imager 16, L _{3 in} the figure is (2 ).

The distance from the reflected part on the main mirror 15 to the second imager 16 is expressed by the following equation (3). Accordingly, even in the state shown in FIG. 9A, the optical path that was L ₀ from the taking lens 14 to the second imager 16 is L obtained by the following equation (4) in the state shown in FIG. 9C. Change to ₀₁ .

That is, it is determined whether or not the photographing lens 14 is in focus with respect to the subject 13 based on the optical path change and the image incident position change accompanying the mirror angle switching in the states shown in FIGS. 9A and 9C. Is possible. In this case, if the shift amount d is a positive value, the value within the square root is always greater than L ₃ , so that L ₀₁ > L ₁ .

In other words, in this state, the optical path length from the taking lens 13 to the second imager 16 is longer than in the state shown in FIG. 9A, and the subject at a closer distance is in focus. Therefore, if the contrast of the image obtained as I _{M1 in the} state shown in FIG. 9C is higher than the contrast of the image obtained as I _{M0 in the} state shown in FIG. Since the contrast is high in a state equivalent to the state where 14 is extended, it can be considered that the subject 13 is closer to the camera.

  That is, such a contrast check of the image can be performed while the main mirror 15 is up or down, so that it is possible to perform focus control while the mirror is retracting, which has conventionally been difficult for a single lens reflex camera.

  The photographing operation for performing such focus control may be controlled in a sequence as shown in FIG. 10, for example. This focus control is executed by the CPU 20 which is a focus control means and a determination means.

That is, first, in step S21, focusing is performed in a mirror-down state as shown in FIG. Although not shown in FIG. 9, a sub-mirror such as the mirror 10 in FIG. 5 is provided behind the semi-transmissive main mirror to use the phase difference AF. Next, in step S22, the second imager 16 determines the contrast C ₀ using the image signal I _M0 .

  Next, the process proceeds to step S23, and mirror drive for retracting the mirror is started so as to obtain a state as shown in FIG. 9B. Here, in step S24, it is determined whether or not the mirror angle has become θ (by a mirror angle determining means not shown), and steps S23 and S24 are repeated until the angle θ is reached.

If it is detected that the mirror angle is θ, that is, the state shown in FIG. 9C is detected, the process proceeds to step S25, and this time the center of the second imager 16 is detected. As shown in FIG. 9C, the image signal I _{M1 at} a position separated by the shift amount d is detected from (I _M0 incident position). Further, in step S26, the contrast is determined from this I _M1 and set to C ₁ .

Subsequently, in step S27, the contrast C1 when there is, the contrast C ₀ or not greater than the time of focusing in step S21 described above is determined. Here, if it is determined that the contrast C ₀ is larger, it is assumed that the subject is moving and is in a short distance. Accordingly, the process proceeds to step S28, and the taking lens 14 is extended (focus position correction) via the lens drive control circuit 21 so that the focus is adjusted closer to the short distance side. On the other hand, in step S27, if it is the greater in contrast C _1, the process proceeds to step S29 by skipping step S28.

  Next, in step S29, it is determined whether or not the mirror up timing has been detected. Here, when the mirror up timing is detected, photographing is performed in the subsequent step S30. When this photographing is finished, the process proceeds to step S31, and mirror down control is performed.

  In step S32, the process proceeds to step S21 and the above-described sequence is repeated until the continuous photographing operation is completed.

  As described above, according to the present embodiment, the change in the contrast state of the subject can be monitored even during the mirror up of the main mirror 15, and the focus control can be performed at a high speed according to the change. Thus, it is possible to provide a high-speed autofocus camera that can follow a subject.

  Further, as will be described later with reference to FIG. 11, the second imager 48 may be provided at a position where the focusing screen 27 is monitored via the lens 49 and the pentaprism 28. With this configuration, it is possible to provide a camera that can use the contrast AF by the optical path length switching by the main mirror 15, which is a feature of the present invention, using the optical viewfinder.

  That is, when the mirror is down, the image of the subject 13 that has passed through the photographic lens 14 can be monitored by the main mirror that is a half mirror, and the light reflected by the sub mirror 32 is guided to the phase difference AF optical system and its sensor 36 to focus. Control becomes possible.

  Further, during the mirror up, the contrast AF as described with reference to FIG. 9 and FIG. 10 can be used together to achieve focusing corresponding to the moving object.

  FIG. 11 is a configuration diagram of an electric system in the camera of one embodiment of the present invention.

  In FIG. 11, the camera 26 includes a photographing optical system including the photographing lens 14, a main mirror 15, a lens drive control circuit 21, a focusing screen 27, a pentaprism 28, an eyepiece lens 29, and a sub mirror 32. A field lens 33, an optical path bending mirror 34, a re-imaging lens 35, a sensor array 36, a shutter curtain 38, a first image sensor (imager) 22, an A / D converter 39, an image A signal processing unit 40, a recording medium unit 41, an arithmetic control circuit 42, a photometric optical system 43, an in-body photometric sensor 44, a light control unit 45, a photometric unit 47, and an image sensor in a finder (second An imager) 48, a lens 49, a flash light emission control unit 50, a flash light emission unit 51, and an operation switch 53.

  The main mirror 15 is a mirror provided in a space between the photographing optical system and the shutter curtain 38. The main mirror 15 guides the incident light beam from the photographing optical system to either the first imager 22 side or the finder optical system (configured by the focusing screen 27, pentaprism 28, eyepiece lens 29, etc.) side. Therefore, it is movably disposed between a position retracted from the optical axis of the photographing optical system and a position disposed on the optical axis.

  The sub-mirror 32 is a sub-reflecting mirror that is foldably attached to the main mirror 15. This sub-mirror 32, when the main mirror 15 is disposed on the optical axis of the photographic lens 14 of the photographic optical system, transmits a light beam that passes through a part of the main mirror 15 to an AF (autofocus) optical system (for details). To the side described later.

  That is, the sub mirror 32 is pivotally supported so that one end thereof is rotatable in a predetermined direction with respect to the back side of the main mirror 15, that is, the surface facing the first imager 22. Thus, the reflecting surface of the sub-mirror 32 is disposed so as to face the region of the semi-transmissive mirror of the main mirror 15 described above.

  When the main mirror 15 is disposed at the normal position 15b, the main mirror 15 is fixed in an inclined state with respect to the central axis of the photographing lens 14 by about 45 degrees. In this state, the reflecting surface of the main mirror 15 is set to face the viewfinder optical system.

  That is, when the main mirror 15 is at the normal position 15b, the light beam incident through the photographing optical system is reflected by the main mirror 15 and guided to the finder optical system. In the finder optical system, the incident light beam is imaged as an optical image on the focusing screen 27 and the image formed is guided to the pentaprism 28.

  On the other hand, when the main mirror 15 is disposed at the retracted position 15 a, the sub mirror 32 is disposed at a predetermined position that is substantially parallel to the main mirror 15. As a result, the main mirror 15 moves to the retracted position 15a, and at the same time, the sub mirror 32 retracts from the optical path of the photographing optical system. Contrast AF is performed using the fact that the optical path length is also switched during the retreat operation.

  The focusing screen 27 is disposed on the optical path of the reflected light beam from the main mirror 15 when the main mirror 15 is disposed on the optical axis of the photographing optical system. Then, an optical image formed by the reflected light beam is formed and the reflected light beam is transmitted.

  The pentaprism 28 receives the light beam transmitted through the focusing screen 27 and guides it in a predetermined direction (rear side of the camera 26), and at the same time, inverts the left and right of the image. Further, the eyepiece 29 is a lens that magnifies a normal image by the pentaprism 28 and guides it to the photographer's eye 30.

  Further, in the vicinity of the pentaprism 28, an in-finder image pickup element (second imager) 48, which is a feature of the present invention, is provided. The second imager 48 is provided with a lens 49 so that the image on the focusing screen 27 can be detected while looking inside the pentaprism 28. When the image on the focusing screen 27 is received, a predetermined electrical signal is output to the photometry unit 47. Here, as shown in FIG. 12, the second imager 48 is formed so as to be able to perform photometry and contrast detection operations in a predetermined light receiving region 48b in the photographing screen 48a.

  The photometric unit 47 performs not only the output of the contrast signal, which is a feature of the present invention, but also a photometric operation based on the electric signal input from the second imager 48 to detect the brightness of the subject. Based on the detection result of the photometry unit 47, the arithmetic control circuit 42 controls the flash light emission control unit 50.

  The flash light emitting unit 51 emits auxiliary illumination light when a desired shooting environment including the subject 13 is dark. Then, charging of the light emission energy of the flash light emission unit 51 and light emission control are performed by the arithmetic control circuit 42 via the flash light emission control unit 50.

  The optical path of the light beam transmitted through the field lens 33 that receives the reflected light beam from the sub mirror 32 and divides the field of view is bent in a predetermined direction by the optical path bending mirror 34. The re-imaging lens 35 is provided on the optical path of the reflected light beam of the optical path bending mirror 34, and the reflected light beam is transmitted so that a pair of subject images are re-exposed on the sensor array 36 disposed at a predetermined position. Make an image.

  The sensor array 36 receives a pair of subject images formed by the re-imaging lens 35 and generates a predetermined electrical signal that contributes to the focusing operation. Then, the electric signal generated here is output to the arithmetic control circuit 42, and the arithmetic control circuit 42 performs a predetermined focusing process.

  Here, the focusing process may be a TTL phase difference detection method that is generally applied as already described with reference to FIGS. 4 and 5. This TTL phase difference detection method will be described again with reference to the drawings.

  In this TTL phase difference method, the calculation control circuit 42 controls the lens drive control circuit 21 to monitor the output of the sensor array 36 while moving the photographing optical system in the optical axis direction of the photographing lens 14. Then, when the pair of subject images output from the sensor array 36 has a predetermined positional relationship, it is determined that the subject is in focus, and the photographing lens 14 is controlled so as to be in the positional relationship, so that the photographing optical System drive is stopped.

  The shutter curtain 38 is disposed in the vicinity of the light receiving surface side of the first imager 22 and adjusts the exposure time of the imager 22 to the light receiving surface. That is, the first imager 22 is configured to receive the light beam from the photographing optical system only during the period when the shutter curtain 38 is in the open state.

  Here, as a configuration of the shutter curtain itself, a configuration generally used in a conventional single-lens reflex camera is applied.

  The configuration of the shutter curtain 38 will be briefly described with reference to the schematic diagram of FIG.

  As shown in FIG. 13, the shutter curtain 38 includes two curtain members, a front curtain 38a and a rear curtain 38b. In the normal state, the front curtain 38a is disposed in front of the light receiving surface of the first imager 22, and the light receiving surface of the imager 22 is shielded.

  Here, when the exposure operation is executed, first, the main mirror 15 and the sub mirror 32 move to a predetermined retracted position 15a. In this state, the front curtain 38a starts to move in the direction of the arrow Y1 shown in the drawing. Subsequently, after a predetermined time, the trailing curtain 38b starts to move in the direction indicated by the arrow Y2 (the same direction as Y1). Therefore, a predetermined gap is generated between the front curtain 38a and the rear curtain 38b. By adjusting the gap size, that is, by adjusting the time for the front curtain 38a and the rear curtain 38b to move, the exposure time (that is, the shutter speed) to the first imager 22 can be adjusted.

  A predetermined pattern (not shown) is formed on the surface of the front curtain 38a so that the light beam reflected on the surface of the front curtain 38a has a standard reflectance. Then, when the main mirror 25 is retracted from the optical axis of the photographing optical system, the reflected light beam that is transmitted through the photographing optical system and reflected by the surface of the front curtain 38a is received by the photometric optical system 43. The The light beam that has passed through the photometric optical system 43 is received by the in-body photometric sensor 44. The light control unit 45 receives a predetermined electrical signal that contributes to the light measurement operation from the in-body light measurement sensor 44 and performs light control.

  Here, as shown in FIG. 14, the in-body photometric sensor 44 has three photometric areas 44a, 44b, and 44c in a form in which the entire light receiving surface is divided into three. For example, in the case where a composition frame (shooting screen 55) as shown in FIG. 15 is set and shooting is performed using the light control of the preliminary light emission method, the in-body photometric sensor 44 shown in FIG. Photometry is performed using only the photometry area 44c. For example, when a high brightness subject such as the sun is included in the shooting screen 55 as in the composition shown in FIG. 15, if photometry is performed including the high brightness subject, the photometric value is displayed. This is a measure for avoiding an error.

  The light control unit 45 measures the amount of incident light from the subject 13 and performs predetermined light control based on the electrical signal output from the in-body photometric sensor 44.

  Here, in the conventional TTL dimming system dimming control in a general camera, for example, there is an apparatus that receives a reflected light beam from the film surface during an exposure operation. However, since the surface of the first imager 22 generally has more regular reflection components in the reflection of light, the camera 26 according to the present embodiment diffuses and reflects the incident light beam with the standard reflectance. Photometry is performed by the reflected light beam from the surface of the curtain 38a.

  In the camera having such a configuration, it is possible to enjoy shooting while monitoring a high-quality subject image with an optical viewfinder, and a comfortable autofocus operation that responds quickly to a moving subject is possible.

  As described above, according to the present embodiment, the optical system of the single-lens reflex camera is effectively used, and the AF unit that compensates for the loss of the focus information at the time of switching the optical path unique to the single-lens reflex camera is used in combination, thereby enabling high-speed focusing. Can be provided.

  In the above-described embodiment, the focus adjustment using the contrast change in the two optical path lengths has been described. However, since the angle of the main mirror can be continuously adjusted in various ways, the number of angle switching is switched according to the contrast change, etc. You may make the device.

  The present invention can be easily applied not only to a single-lens reflex camera but also to a camera in which an optical path is bent by a reflecting member and a photographing lens and an image sensor are connected.

  In other words, all of the techniques that can switch the optical path and the position of the light incident on the image sensor by controlling the reflecting member can be easily applied.

  With such a configuration, it is possible to provide a high-speed strike-type autofocus by moving a lighter and smaller mirror without moving the photographing lens. This method also has a feature that it can be easily combined with other AF methods as shown in the embodiment.

1 is a schematic block diagram of an AF optical system of a camera according to an embodiment of the present invention. It is a figure explaining a hill-climbing AF system. It is the figure which showed the relationship between contrast and the lens extension amount. 1 is a perspective view schematically showing a configuration of an optical system of a phase difference AF method. It is a figure explaining the structure of the optical system of a phase difference AF system. It is a flowchart explaining the focusing operation | movement of the auto-focus camera which is one Embodiment of this invention. It is a figure explaining the signal reading of an image sensor. 5 is a timing chart for explaining charge accumulation and signal readout operations of the image sensor. It is the figure which showed the example which applied AF system which is one Embodiment of this invention to the single-lens reflex camera. It is a flowchart explaining the imaging | photography operation | movement of the camera in one Embodiment of this invention. It is a block diagram of the electric system in the camera of one Embodiment of this invention. It is the figure which showed the example of the imaging | photography area | region in an imaging | photography screen. It is the schematic explaining the structure of the shutter curtain 38 of FIG. It is the figure which showed the example of the photometry area | region of the in-body photometry sensor 44 of FIG. It is a figure explaining a composition and a photometry area | region.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 13 ... Subject, 14 ... Shooting lens, 15 ... Main mirror, 16 ... Area sensor (2nd imager), 17, 23 ... Actuator, 18 ... Contrast judgment part, 20 ... Microcontroller (CPU), 21 ... Lens drive ( LD) control circuit, 22 ... first image sensor (first imager), 24 ... finder circuit, 26 ... camera, 27 ... focusing screen, 28 ... penta prism, 29 ... eyepiece, 32 ... submirror, 36 ... sensor Array, 38 ... Shutter curtain, 40 ... Image signal processing unit, 41 ... Recording medium unit, 42 ... Operation control circuit, 43 ... Metering optical system, 44 ... In-body photometric sensor, 45 ... Light control unit, 47 ... Metering unit, 48 ... in-finder image sensor (second imager), 50 ... flash emission control unit, 51 ... flash emission unit, 53 ... operation Switch.

Claims (12)

A movable mirror,
An image sensor for imaging a subject image reflected by the movable mirror;
Detecting means for detecting the subject image change by the image sensor while moving the movable mirror;
A focus control means for determining a focus direction or a focus position of the photographic lens based on a subject image change detected by the detection means;
An autofocus camera comprising:   2. The movable mirror according to claim 1, wherein the movable mirror is arranged in a photographing optical path and is movable to a first position for guiding a subject image in a viewfinder direction and a second position retracted from the photographing optical path. Autofocus camera.   2. The autofocus camera according to claim 1, wherein the focus control means determines the focusing direction based on a change in contrast signal of the subject image signal accompanying a change in optical path length due to movement of the movable mirror.   The autofocus camera according to claim 1, further comprising a lens driving unit that moves the photographing lens in the focusing direction determined by the focus control unit. A reflecting member that guides the subject image light beam incident through the photographing lens to the image sensor;
Angle control means for controlling the angle of the reflecting member;
The angle control means switches the incident position of the subject image to the image sensor via the photographing lens, and the focus of the photographing lens is determined by the contrast change of the subject image at the plurality of switched incident positions. Determination means to perform,
An autofocus camera comprising:   6. The autofocus camera according to claim 5, further comprising a lens driving unit that moves the photographic lens to focus the photographic lens in accordance with a determination result of the determination unit. A phase difference type autofocus in which an image signal of a subject is guided to a pair of sensors by a first reflecting mirror that can be retracted from the optical path using different optical paths of the photographing lens;
Auto focus of a method of detecting a change in contrast by switching the optical path length according to the position of the second reflecting mirror interlocked with the first mirror;
Autofocus camera equipped with two autofocus methods.   8. The autofocus camera according to claim 7, wherein a phase difference method is used before retracting the optical path of the first mirror, and a contrast method is used during retracting. A taking lens,
A reflecting member that reflects a light beam from the subject image incident through the photographing lens;
An image sensor that forms a luminous flux of the subject image reflected by the reflecting member;
An optical path length changing means for changing an optical path length from the photographing lens to the imaging device;
Detecting means for detecting an incident position of the subject image changed by the optical path length changing means on the image sensor;
Determination means for determining a focus position of the photographing lens based on a change in the subject image detected by the detection means;
An autofocus camera comprising:   The autofocus camera according to claim 9, further comprising a lens driving unit that moves the photographic lens to focus the photographic lens according to a determination result of the determination unit.   The autofocus camera according to claim 9, wherein the optical path length changing unit moves the reflecting member along an optical axis direction of the photographing lens.   The autofocus camera according to claim 9, wherein the optical path length changing unit changes an incident position of a subject image on the image pickup device by controlling an angle of the reflecting member.

Images