JPH11337813A - Autofocus camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the certainty in focus adjustment and to reduce the necessity of a low contrast scan by bringing a photographing lens close to focusing with the focus adjustment based on an image in a large detection area and focus-adjusting based on an image in a small detection area. SOLUTION: By repeating the detection of out-of-focus by a focus detection part 33 and the drive of a focus lens by a lens drive control part 34 according to the detection result, the detected deviation is reduced gradually, and the automatic adjustment of the focus of the photographing lens 1 is performed. The focus detection part 33 stops focusing when the detected deviation becomes a focusing reference value or below. In such a case, the focus detection part 33 starts the focus adjustment of the photographing lens 1 based on the positional deviation detected by using an image in a first area, and focus-adjusts the photographing lens 1 based on the positional deviation detected by using an image in a second area after a calculated drive amount becomes a prescribed value or below, or the size of the positional deviation detected by using the image in the first area becomes the prescribed value or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus camera using a phase difference detection method, and more particularly, to an autofocus camera having two large and small detection areas.

[0002]

2. Description of the Related Art Some autofocus (AF) cameras that automatically focus a photographing lens on a subject adopt a phase difference detection method as a method for detecting a shift in the focus of the photographing lens. In the phase difference detection method, one image detection sensor such as a line sensor is provided near a surface equivalent to an imaging surface on which an imaging device such as a silver halide film or a photoelectric conversion device is arranged.
A pair or a plurality of pairs are arranged to guide the luminous flux of different parts of the light transmitted through the photographing lens to different sensors, and to detect the shift of the focal point of the photographing lens from the positional deviation of the subject image on the paired sensors. It is.

In this type of autofocus camera,
The amount of deviation detected by repeating the operation of detecting the direction and amount of defocus and driving the focus lens for focusing included in the photographing lens in the detected direction by a distance corresponding to the detected amount. And finally focus the taking lens on the subject.

In order to detect the displacement of the object image on the paired sensors, it is necessary to find out which part of the images of both sensors corresponds to which part, which is based on the brightness of the image on the sensors. That is, the comparison is performed by comparing contrast distribution patterns. Therefore, when the subject does not have sufficient contrast, the position of the subject image on the sensor cannot be determined, and focus adjustment cannot be performed. Even when the subject has a sufficient contrast, if the focus of the photographing lens is largely out of focus, the image is blurred on the sensor and the contrast is lost, making it difficult to adjust the focus.

When the displacement of the image cannot be detected due to insufficient contrast of the image on the sensor, the focus lens is moved at a relatively low speed while monitoring the contrast of the sensor to provide a contrast that can be detected. Find the position of the lens. This operation is called a low contrast scan.

In the low-contrast scan, it is not known at that time whether the focus is in front of or far from the subject, and how much the focus is out of focus. Done on a range. For example, the focus lens is first moved from its current position to the near end corresponding to the latest shooting distance, and then to the infinity end corresponding to the furthest (infinity) shooting distance. Thus, even if the focus of the photographing lens is greatly deviated from the in-focus position, it is possible to detect the displacement.

The accuracy of the shift of the focus of the taking lens with respect to the subject detected by the phase difference detection method depends on the size of the detection area of the sensor. As the detection area of the sensor is larger, a wider range of the image is compared, and the influence other than the part of the subject to be focused is increased, resulting in lower accuracy. The size of the detection area of the sensor is set so as to be suitable for photographing under normal conditions, but such a detection area is not suitable for very strict focusing on a narrow range.

Therefore, a detection area of a normal size and a small detection area limited to a part thereof are set in the sensor so that the user can arbitrarily select one of the detection areas. Even when a small detection area is selected, the detection of the image position shift and the manner of driving the focus lens based on the detected shift are performed in the same manner as when a normal size detection area is selected.

[0009]

However, since light from only a small part of the object is guided to the small detection area, the contrast is lowered, and the necessity of performing low-contrast scanning increases. In addition, since the amount of information is reduced, the number of parts having similar contrasts increases, and the frequency of erroneous detection of judging a part that does not originally correspond to a corresponding part increases. For this reason, even if a low-contrast scan is performed, it is often not possible to appropriately perform focus adjustment.

In addition, since the low-contrast scan is performed with the drive direction of the focus lens determined in advance, such as the near end side and then the infinite end side, the drive is started in the direction opposite to the in-focus position. In some cases, useless driving is performed, and it takes longer than necessary for focus adjustment. Moreover, if a sufficient contrast cannot be obtained even by performing a low-contrast scan, the focus lens will be located at the near end or the infinity end at the end of the scan, and the photographing lens will be significantly out of focus.
The viewfinder image becomes largely blurred.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has an improved focus adjustment certainty of a phase difference detection type autofocus camera capable of performing a strict focus adjustment by limiting a detection area. It is an object of the present invention to reduce the necessity of performing a low contrast scan.

[0012]

In order to achieve the above object, according to the present invention, different portions of a light beam transmitted through a photographing lens are respectively guided to two sensors, and an image detected by one sensor and an image detected by the other sensor are used. An autofocus camera that compares a detected image to detect a position shift of a corresponding part and adjusts a focus of a photographing lens so as to eliminate the position shift, and one sensor for detecting the position shift. In the method of selecting and using the image of the first area and the image of the second area smaller than the first area, the positional deviation is eliminated from the positional deviation detected using the image of the first area. Driving amount calculating means for calculating a driving amount of the focus setting lens of the photographing lens required for the photographing, and starting the focus adjustment of the photographing lens based on a position shift detected using the image of the first area;
After the drive amount calculated by the drive amount calculation means becomes equal to or less than a predetermined value, or after the magnitude of the positional deviation detected using the image of the first area becomes equal to or less than the predetermined value, A focus adjustment unit that adjusts the focus of the photographing lens based on the positional deviation detected using the image.

In this camera, when performing focus adjustment based on an image of a relatively small second area, first, focus adjustment based on an image of a relatively large first area is performed. Then, focus adjustment based on the image of the second area is performed in a state where the photographing lens is close to focusing. Whether the focus is approached or not is determined from the remaining drive amount of the focus lens to the focus position or the magnitude of the deviation of the detected position. By setting the taking lens in a state close to focusing, the image on the sensor is almost free of blur, and the contrast is increased. Therefore, the reliability of the focus adjustment based on the image of the second area is improved, and the necessity of performing the low contrast scan is reduced.

A signal generating means for giving a predetermined signal for instructing the adjusting operation to the focus adjusting means, wherein the focus adjusting means comprises:
When a predetermined signal is given, focus adjustment of the photographing lens is performed based on a position shift detected using the image of the second area. When a predetermined signal is not given, the image of the first area is adjusted. The focus adjustment of the photographing lens based on the positional deviation detected by using may be continued. With this configuration, focus adjustment based on the image of the second area can be performed only when necessary.

The signal generating means may provide a predetermined signal to the focus adjusting means in accordance with an operation state of an operation member provided on the camera body or the photographing lens. In this case, the operating member will be assigned to switching between normal precision focus adjustment and higher precision focus adjustment,
The user can select any one according to his preference.

The signal generating means may obtain information indicating the type of the lens from the taking lens and provide a predetermined signal to the focus adjusting means when the taking lens is a predetermined type of lens. It is possible to automatically limit the detection area according to the characteristics of the taking lens. For example, even when using a taking lens that can detect positional deviation only in a narrow range such as a reflective telephoto lens, the user can The focus can be adjusted by detecting the positional deviation without waiting for the operation.

When comparing an image detected by one sensor with an image detected by the other sensor to find a corresponding portion,
When using the image of the second region of one sensor, it is preferable to compare with the narrower range of the image of the other sensor than when using the image of the first region. In the focus adjustment based on the image in the second area, the photographing lens is already close to the focus, and there is no large shift in the positions of the images of the two sensors. Can be reliably found. By narrowing the range to be compared, a corresponding part can be found in a short time, and the risk of erroneous detection of determining an uncorresponding part as a corresponding part is greatly reduced.

[0018]

FIG. 1 shows a schematic configuration of an embodiment in which the present invention is applied to a single-lens reflex camera. A photographing lens 1 is mounted on a front surface of a camera body (not shown). The photographic lens 1 is configured to be detachable from the camera body, and various photographic lenses having different focal lengths, open aperture values, and the like are prepared, and can be replaced and mounted on the camera body. The photographing lens 1 is composed of a plurality of groups formed by combining single lenses, and the focal position is adjusted by moving some of the groups (focus lenses) along the optical axis.

A photographic film 2 is provided at the rear of the camera body.
Is supplied, and the photographic film 2 is exposed to light by the photographic lens 1 to perform photographing. By setting the focal position of the photographing lens 1 in accordance with the distance from the camera to the subject, a focused subject image is formed on the photographing film 2 and a sharp subject image is photographed.

A reflecting mirror 3 is provided in front of the photographic film 2, and a focusing screen 4 and a pentaprism 5 are provided above the reflecting mirror 3. The reflecting mirror 3 is provided so as to be retractable on an optical path from the photographic lens 1 to the photographic film 2, and is normally on the optical path and reflects the transmitted light of the photographic lens 1 upward. When operating the shutter release button not shown,
The reflecting mirror 3 is retracted from the optical path so as not to prevent light from reaching the photographic film 2.

The light reflected upward by the reflecting mirror 3 forms an image on the reticle 4, and the camera user can observe the image on the reticle 4 via the pentaprism 5. The distance from the point where the optical axis of the photographic lens 1 intersects the reflecting mirror 3 to the photographic film 2 and the distance to the reticle 4 are set equal, and the image on the reticle 4 is the same as the image on the photographic film 2 Become sharp.

The above-mentioned reflecting mirror 3, focusing plate 4, and pentaprism 5 are well-known components of a single-lens reflex camera.
The camera of the present embodiment is an autofocus camera,
For this purpose, an AF sensor unit 6, an AF control unit 7, and a lens driving unit 8 are provided. The central portion of the reflecting mirror 3 is formed to be semi-transmissive, and a small sub-reflecting mirror 9 is fixedly installed on the rear surface of the central portion of the reflecting mirror 3. The AF sensor unit 6 is disposed below the sub-reflecting mirror 9, and a part of the light transmitted through the photographing lens 1 passes through the central portion of the reflecting mirror 3 and is reflected downward by the sub-reflecting mirror 9, and the AF sensor unit It is led to 6.

The AF sensor section 6 has a line sensor 10, and the line sensor 10 detects light from the sub-reflecting mirror 9 and outputs an electric signal. This output is processed by the AF control unit 7 as will be described later in detail, and the shift amount and the shift direction of the focus from the in-focus position are detected. The AF control unit 7 includes a microcomputer, generates a control signal from the detected amount of focus shift and its direction, and supplies the control signal to the lens driving unit 8.

The lens driving unit 8 includes a motor for driving the focus lens of the photographing lens 1, and drives the focus lens based on a control signal to set the focal position of the photographing lens 1. Further, the camera of the present embodiment is provided with a display unit 11, and the AF control unit 7 displays that the camera is in focus at the time of focusing to notify the user of the focus state.

The AF sensor unit 6 is, as shown in FIG.
In order to guide the light from the sub-reflection mirror 9 to the line sensor 10,
Condenser lens 12, reflector 13, imaging lens group 14
have. The reflecting mirror 13 is provided to reduce the size of the AF sensor unit 6 by bending the optical path, and is not always necessary for light detection by the line sensor 10. FIG. 2 shows the optical system of the AF sensor unit 6 excluding the reflecting mirror 13.

In FIG. 2, a straight line 21 corresponds to the optical axis of the taking lens 1. The broken line 22 is a surface equivalent to the exposure surface of the photographic film 2, and the distance from the intersection of the optical axis of the photographic lens 1 and the sub-reflecting mirror 9 to the exposure equivalent surface 22 is the distance between the optical axis of the photographic lens 1 and the sub-reflecting mirror 9. Is equal to the distance from the intersection of to the exposure surface of the photographic film 2. That is, the optical path length from the taking lens 1 to the exposure equivalent surface 22 and the taking lens 1 to the taking film 2
Is equal to the optical path length up to.

The condenser lens 12 has an exposure equivalent surface 22
They are arranged in a position apart focal length f ₁ of the condenser lens 12 from. Behind the condenser lens 12, a pair of imaging lenses 14L and 14R are disposed symmetrically with respect to the optical axis 21.
Field limiting masks 23L and 23R having openings of a predetermined size are provided on the front surface of 14R. The field-of-view limiting masks 23L and 23R limit the diameter of the light beam incident on the imaging lenses 14L and 14R, and allow only the light beam having a constant diameter to reach the line sensor 10.

In this embodiment, the line sensor 10 for receiving light is used.
A pair of CCDs (charge-coupled devices) 15L and 15R is used. These CCDs 15L and 15R are provided with an imaging lens 1
On the imaging planes of 4L and 14R, imaging lenses 14L and 14R
Are arranged perpendicular to the optical axis of Instead of a pair of CCDs, a single long CCD may be used, and light from the imaging lenses 14L and 14R may be received in different light receiving areas.

FIG. 2 shows a pair of CCDs 15L, 15R and 1 CCD.
Although only the pair of imaging lenses 14L and 14R are shown, the camera of this embodiment has a total of four pairs of CCDs for focus detection.
And four imaging lenses provided with a field limiting mask are provided corresponding to each CCD pair. These CCD pairs are referred to as first to fourth islands of the line sensor 10.

FIG. 4 shows the arrangement of the islands of the line sensor 10. The above-mentioned CCD pair 15L, 15R forms a second island 10b and is arranged in the horizontal direction. First,
C forming the third and fourth islands 10a, 10c and 10d
The CD pairs are arranged vertically symmetrically with respect to the second island 10b. First and third islands 10a
And 10c are arranged near both ends of the second island 10b, and the fourth island 10d is arranged at the center of the second island 10b. The horizontal displacement of the image can be detected in the horizontal second island 10b, and the vertical displacement of the image can be detected in the vertical first, third, and fourth islands 10a, 10c, and 10d.

The detection of an image by the AF sensor unit 6 will be described by taking the second island 10b as an example. The light from the sub-reflecting mirror 9 is condensed by the condenser lens 12 after passing through the exposure equivalent surface 22, and is condensed by the field limiting masks 23L, 2L.
The light passes through the opening of 3R and reaches the imaging lenses 14L and 14R. The light transmitted through the imaging lenses 14L and 14R forms an image on the light receiving surfaces of the left and right CCDs 15L and 15R, respectively.
Condenser lens 12 and imaging lenses 14L, 14R
From the exposure equivalent plane 22 to the condenser lens 12, the imaging lenses 14L and 14R and the CCD 15
The distance between the light-receiving surfaces L and 15R is set so that the image on the exposure equivalent surface 22 is re-imaged on the CCDs 15L and 15R.

Here, since the condenser lens 12 is arranged away from the exposure equivalent surface 22, even if the condenser lens 12 has a flaw or dust,
Formation of a sharp image on the light receiving surfaces of the CDs 15L and 15R is prevented. The image of the scratches and dust on the condenser lens 12 becomes noise and has a bad influence on the detection of the displacement of the image, but the blurred image has a small contribution to the detection of the displacement, and the scratches and the dust on the condenser lens 12 having the above arrangement are small. The adverse effects of the above can be reduced.

The field-of-view limiting masks 23L and 23R are
The condenser lens 12 and the CCD 15L, such that only light passing through a specific aperture value, for example, an aperture area equivalent to F5.6, out of the light transmitted through the taking lens 1 is passed.
An opening is set in relation to the light receiving area width of 15R. When the light beams whose peripheral portions are blurred are received by the CCDs 15L and 15R, the light does not reach the ends of the CCDs 15L and 15R, so that the photometric range is reduced, and the range in which a shift in the image position can be detected is reduced. By setting the apertures of the field-of-view limiting masks 23L and 23R as described above, when various interchangeable lenses are used as the photographing lens 1, if the open aperture value is smaller than F5.6, the photographing lens itself may be used. The light partially shaded by the pupil mask is transferred to the CCD 15L, 15R.
This avoids the disadvantage of receiving light at the same time, so that most commonly used interchangeable lenses can be applied.

In FIG. 2, points P ₀ , P ₁ ,
P ₂ indicates the position of the aerial image in focus, front focus, and rear focus with respect to one point in front of the photographing lens 1. The incident positions on the left CCD 15L from the image positions P ₀ , P ₁ , and P ₂ are PL ₀ , PL ₁ , and PL ₂ , respectively, and the incident positions on the right CCD 15R are PR ₀ , PR ₁ , and PR ₂ , respectively.

FIG. 3 shows the positional relationship between the in-focus and the refocusing of the aerial image of the front focus and the rear focus. Focused image Z ₀ is CCD 15L, 1
The image is re-formed on the light receiving surface 24 of 5R to become ZL ₀ and ZR ₀ .
The re-imaging of the front focus image Z ₁ becomes ZL ₁ and ZR ₁ ,
CCDs 15L, located in front of the light receiving surface of the 15R, and closer to the optical axis 21 than the reimaging ZL ₀ and ZR ₀ focusing. On the other hand, the re-imaging of the rear focus image Z ₂ becomes ZL ₂ and ZR ₂ and is located behind the light receiving surfaces of the CCDs 15L and 15R.
Further, it is further away from the optical axis 21 than the refocused images ZL ₀ and ZR ₀ . Therefore, the image Z _{1 of the} front focus is the CCD 15
L, becomes an image which is elongated blurred slightly on the light receiving surface of the 15R, the image Z ₂ of the rear pins CCDs 15L, the shrunken image blurred slightly on the light receiving surface of the 15R.

As is apparent from FIG.
The image positions detected by L, 15R reflect the focus state such as focus, front focus, rear focus, etc.
By comparing the left and right image positions on L, 15R,
A focus state is detected. Since the left and right CCDs 15L and 15R are fixed to the camera and their positional relationship is constant, the amount of focus shift and the direction of the shift can be known from the distance between the left and right images of the subject.

FIG. 5 schematically shows the arrangement of the pixels of the CCDs 15L and 15R and the arrangement of the signals after subjecting the output signals of these pixels to predetermined processing so as to be suitable for the focus detection calculation. Show. 44 of the left CCD15L is L ₁ ~L ₄₄
Has a number of pixels, right CCD15R has 52 pixels of R ₁ to R _52. Left and right CCDs 15L, the output of the 15R, i.e. the pixel value of the pixel L ₁ ~L ₄₄ and R ₁ to R _52, but is representative of the amount of received light, the left and right CCDs 15L, 1
In order to match the output level of the left and right by correcting the sensitivity difference of the 5R, performs quantization processing on the output signals of the pixels L ₁ ~L ₄₄ and R ₁ to R _52.

Specifically, the difference between the values of the pixels four pixels apart is calculated, and the difference l ₁ , L ₂ between L ₁ and L ₅ is determined for the left CCD 15L.
The difference l ₂ of L _6, hereinafter likewise seek to differences l ₄₀ of L ₄₀ and L _44. Similarly for the right CCD 15R, the difference r ₁
determine the r _48. By this quantization processing, the left and right pixel data l _{1 to} l ₄₀ and r _{1 to} r ₄₈ average to the same level, and the left and right images can be easily compared.

The pixel data l _{1 to} l ₄₀ are referred to as a reference portion, and the pixel data r _{1 to} r ₄₈ are referred to as a reference portion. The pixel data of the reference portion is compared with the pixel data of the reference portion to determine the focus position of the left and right images. Find the deviation. Here, the pixel data of the left CCD 15L is used as the reference part, and the pixel data of the right CCD 15R is used as the reference part.
The pixel data of the CD may be used as the reference portion, and the pixel data of the left CCD may be used as the reference portion.

In detecting the focus state, the left CCD 15
It is necessary to know which part of the L image corresponds to which part of the image on the right CCD 15R. For this purpose, as shown in FIG. 5, a plurality of blocks composed of continuous pixel data are set by dividing the reference portion, and each block is compared with the same number of pixel data of the reference portion. The first, second and third blocks respectively include 20 pieces of pixel data l _{1 to} l ₂₀ and l _11.
Consists to l ₃₀ and l ₂₁ to l _40, is an area used in the normal focus detection. These blocks share half of the pixel data with neighboring blocks.

The camera according to the present embodiment can also perform fine spot detection for detecting the focus state using a smaller area.
Fourth blocks l _{16 to} l _{25 each} consisting of 10 pixel data, which is half of the number of pixel data of the block, are used. This fourth block is also called a fine spot block. The fine spot block is set at the center of the second block,
The five pixel data is shared with the first block, and the remaining five pixel data is shared with the third block.

The comparison between the reference part and the reference part is performed by the correlation operation of the equation (1) or (2). Equation (1) is used for the first to third blocks, and equation (2) is used for the fine spot block.

[0043]

(Equation 1)

(Equation 2)

Here, n represents a block number (1 to 4). The pixel data l _{1 to} l ₂₀ of the first block are obtained from the pixel data r ₁ to r ₂₀ to r ₂₉ of the reference portion by the equation (1).
~r is sequentially compared with up to _48, mismatch amount H ₁ (1) is the sum of the absolute value of the difference between the pixel data values to H ₁ (29) is calculated.
Similarly, the pixel data l _{11 to} l ₃₀ of the second block and the pixel data l _{21 to} l ₄₀ of the third block are obtained from the pixel data r ₁ to r ₂₀ to r ₂₉ to r ₄₈ of the reference portion according to the equation (1).
, And 29 discrepancies H ₂ (1) to H
₂ (29), H ₃ (1) to H ₃ (29) are calculated. As described above, the first to third blocks perform the correlation operation with the entire range of the reference portion.

For the fourth block, that is, the fine spot block, the correlation calculation is performed not in the entire range of the reference portion but in a narrower range. That is, the pixel data l _{16 to} l ₂₅ of the fine spot block are compared with the pixel data r ₁₇ to r ₂₆ to r ₂₃ to r ₃₂ of the reference portion by the equation (2), and the seven mismatch amounts H ₄ (17) are compared. ) To H ₄ (23) are calculated.

When the optical system of the AF sensor unit 6 is in a focused state, the first blocks l _{1 to} l ₂₀ of the reference unit are used as pixel data r _{5 to} r ₂₄ of the reference unit, and the second blocks l ₁₁ to r ₂₄ are used. l ₃₀ is the pixel data r ₁₅ ~r _34, third block l ₂₁ to l ₄₀ is configured to match the pixel data r ₂₅ ~ _44. That is, the in-focus positions of the first to third blocks shown in the reference section of FIG. 5 are areas respectively corresponding to the images of the first to third blocks of the reference section when in the focused state. Therefore,
When the subject is forming an image on the first block of the reference part,
Among the mismatch amounts H ₁ (1) to H ₁ (29) of the first block, H
_{If 1} (5) is the minimum, it is in focus. If any of H ₁ (1) to H ₁ (4) is the minimum, it is the front focus, and _{one of} H ₁ (6) to H ₁ (29). Is the rear pin if is minimum.

Similarly, when the object is focused on the second block, if H ₂ (15) is the minimum, focus is achieved, and H ₂ (1) -H ₂
If any of (14) is the minimum, the front pin, H ₂ (16) to H ₂ (2
If any of 9) is minimum, it is a rear pin. Further, when the subject is focused on the fine spot block, focusing is performed when H ₄ (20) is minimum, and focusing is performed when any of H ₄ (17) to H ₄ (19) is minimum. , H ₄ (21) to H ₄ (23) are the rear pins if they are the minimum. When the subject is focused on the third block, focusing is performed when H ₃ (25) is minimum, and focusing is performed when any of H ₃ (1) to H ₃ (24) is minimum. , either _{H 3 (26) ~H 3 (} 29) is a rear focus if minimal.

The defocus amount is detected as a shift amount from the in-focus position of the image of the reference portion. For example, if H ₂ (km) shows the minimum value among the mismatch amounts of the second block,
The shift amount of the second block is obtained by (km-15). The shift amounts of the other blocks are similarly obtained. However, the shift amount thus obtained is a value in pixel units,
The upper limit of the accuracy is defined by the pixel arrangement pitch. Therefore, for example, the reference part position km indicating the minimum amount of mismatch H (km) and the positions (km-1) and (km + 1) corresponding to the positions on both sides thereof are shown in FIG.
Interpolation processing using the point mismatch amount is performed so as to obtain the shift amount more strictly.

In the normal focus detection, the shift amount is obtained for the first to third blocks as described above, and the block having the smallest shift amount among the blocks having the contrast equal to or more than a predetermined value is selected. Is driven so that is smaller. Then, when the shift amount becomes equal to or less than the predetermined focusing reference value, it is determined that focusing has been achieved, and the focus adjustment ends. In the fine spot detection, the focus lens is driven so that the shift amount of the fine spot block becomes small, and the focus adjustment is completed when the shift amount becomes equal to or less than the focus reference value.

The first, third and fourth islands 10a and 10a
The detection of the focus state at c and 10d is similar, and the amount of focus shift and the direction of the shift can be known from the distance between the upper and lower images of the subject. However, these islands are provided for performing normal focus detection and are not used for fine spot detection. Therefore, the first,
Fine spot blocks are not provided on the third and fourth islands 10a, 10c and 10d,
Only three blocks corresponding to the third block are provided.

Hereinafter, the configuration for focus adjustment and the operation of focus adjustment in the camera of this embodiment will be described in detail. FIG. 4 schematically shows a configuration related to focus adjustment. The AF sensor unit 6 includes a CCD control circuit 16.
Is controlled. The AF control unit 7 includes an A / D converter 31, a RAM 32, a focus detection unit 33, a lens drive control unit 34, a timer circuit 35, and a sensor control unit 36.

The A / D converter 31 is connected to the CCD control circuit 16
The analog output signal of the line sensor 10 given via the CPU is converted into a digital signal, the above-described quantization processing is performed, and the processed signal is stored in the RAM 32. The camera includes a communication unit (not shown) that communicates with the photographing lens 1 to acquire information on the photographing lens 1, and the communication unit outputs to the AF control unit 7 information related to the focus adjustment among the acquired information. A lens data output unit 41 for storing the data in the RAM 32 is provided. Information on the photographic lens 1 stored in the RAM 32 includes, for example, the type of the photographic lens, the focal length, the position of the focus lens at that time,
The operation status of the fine spot AF switch provided on the photographing lens for instructing to perform the fine spot detection is included.

The focus detection section 33 reads out the quantized signal stored in the RAM 32, performs the above-described correlation operation between the reference portion and the reference portion of the paired CCD, and detects the direction and amount of the focus shift. . Then, the direction, speed, and amount of rotation of the motor 8a of the lens driving unit 8 are calculated from the detected deviation, and the information is provided to the lens driving control unit 34.

The lens drive control section 34 includes a focus detection section 33
The lens driving unit 8 is controlled according to the information given from the control unit to rotate the motor 8a to drive the focus lens. The camera is provided with an encoder 43 for detecting the rotation of the motor 8a, and the lens drive control unit 34 controls the rotation of the motor 8a while monitoring the output of the encoder 43.

The timer circuit 35 is used for timer interrupt processing for detecting that the focus lens has reached the near end or the infinite end and stopping the focus lens. The sensor control unit 36 is connected via the CCD drive circuit 16 to
It instructs the start of photoelectric conversion of each CCD of the line sensor 10 and the output of charge accumulated by photoelectric conversion.

By repeating the detection of the focus shift by the focus detection unit 33 and the driving of the focus lens by the lens drive control unit 34 in accordance with the detection result, the detected shift amount gradually decreases. Automatic adjustment of the focus of the taking lens 1 is performed. When the detected shift amount becomes equal to or less than the focus reference value, the focus detection unit 33 stops the focus lens, terminates the focus adjustment, and causes the display unit 11 to display that focus has been achieved.

The focus detecting section 33 includes a fine spot AF provided on the camera body for instructing the type of the photographing lens 1 stored in the RAM 32, the operation status of the fine spot AF switch, and performing the fine spot detection. Based on the operation status of the switch 42, either normal focus detection or fine spot detection is selected. Specifically, when the photographing lens 1 is of a special type such as a reflective telephoto lens capable of focus detection only in a narrow range, fine spot detection is performed regardless of the presence or absence of a fine spot detection instruction. For a type of lens, fine spot detection is performed only when a fine spot detection instruction is issued.

In normal focus detection, correlation calculation is performed for all of the first to fourth islands 10a to 10d, and a focus shift is detected based on the calculation result of one of the islands. If focus cannot be detected by any of the islands, a low-contrast scan is performed to find the position of a focus lens capable of focus detection.

When fine spot detection is instructed by the type or operation of the lens, first, a correlation operation is performed on the entire second island 10b, that is, the first to third blocks, and based on the operation result of any one of the blocks. Defocus is detected. Then, when the taking lens 1 approaches the in-focus state, the mode is switched to fine spot detection, that is, correlation calculation of the fine spot block and detection of a focus shift based on the result. If the focus cannot be detected before switching to fine spot detection,
Perform a low contrast scan.

Whether or not the taking lens 1 has approached focusing is determined by
The determination is made based on the remaining drive amount of the focus lens required for focusing or the magnitude of the detected focus shift amount. Each time the output signal of the AF sensor unit 6 is written into the RAM 32, the focus detection unit 33 detects a focus shift by calculating a correlation, and calculates a drive amount for moving the focus lens to a focus position. During this calculation, the lens drive control unit 34 continues to drive the focus lens,
The drive amount during this time is measured by the output of the encoder 43. The difference between the calculated drive amount and the measured drive amount is the remaining drive amount.

The focus detector 33 determines that the remaining drive amount is equal to the reference value A.
In the following cases, or when the detected defocus amount is equal to or smaller than the reference value B, it is determined that the photographing lens 1 is close to focusing. Determination reference value A for remaining drive amount and determination reference value B for deviation amount
Is obtained as information on the taking lens 1 and stored in the RAM 32
Is determined by the focus detection unit 33 according to the focal length stored in the.

The flow of the process of adjusting the focus of the photographing lens 1 performed by the AF control unit 7 will be specifically described with reference to the flowcharts of FIGS. FIG. 6 shows a schematic flow of the entire processing. Start of focus adjustment is instructed by operating a shutter release button provided on the camera body. When the shutter release button is half-pressed, a first signal for instructing photometry for focus adjustment and exposure control of the photographic lens 1 is output, and when fully pressed, a second signal for instructing exposure of the photographic film 2 is output. It is set to output.

The AF control unit 7 first determines whether or not the start of focus adjustment is instructed by the first signal (step # 5). If there is no instruction, the AF control unit 7 performs an operation for detecting the focus position. (# 10), and releases the flag indicating that there has been an operation (experience in focus position detection calculation) (# 10), and waits for an instruction. When instructed, the AF sensor unit 6
The photoelectric conversion of the CD is started (# 15), and after integration for a predetermined time, the accumulated charge of each CCD is output from the AF sensor unit 6 and stored in the RAM 32 (# 20).

Next, a correlation operation for focus position detection is performed (# 25), and the focus position detection calculation experience is set to "Yes"(# 30). Then, a focus shift is calculated from the result of the correlation calculation (# 35), the drive of the focus lens is controlled (# 40), and the process returns to step # 5 to repeat a series of processes. The lens drive control in step # 40 is performed based on the detection result when the defocus can be detected. When the defocus cannot be detected, the lens drive control is performed at a predetermined speed in a predetermined direction. This is a contrast scan.

FIG. 7 shows the flow of the focus position detection calculation in step # 25. First, the operation state of the fine spot AF switch provided on the photographing lens 1 and the camera body,
Then, the type of the photographing lens 1 stored in the RAM 32 is checked to determine whether or not there is an instruction to perform fine spot detection (step # 105). When there is no fine spot detection instruction, the flag indicating that the correlation calculation using the fine spot block is being performed (fine spot block calculation is being performed) is cleared (# 150), and the first to fourth flags are set.
A correlation operation is performed for all of the islands (# 15
5) Return to step # 30 in FIG.

When an instruction for fine spot detection is given, it is determined whether or not the user has experience in calculating the focus position (# 11).
0), if inexperienced, cancel the fine spot block calculation (# 140), and perform the correlation calculation on the entire second island including the fine spot block (# 140).
145), and return to step # 30 of FIG. When focus detection calculation is performed at least once irrespective of whether or not focus detection is possible, the focus position detection calculation experience is set to "Yes" in step # 30 of FIG. Only immediately after the start of focus adjustment.

If there is experience in the determination of # 110, it is determined whether or not the fine spot block calculation is in progress (#
115) If the fine spot block calculation is not being performed, a determination process is performed as to whether or not to switch to fine spot block detection (# 120). Next, the processing result is determined (# 125), and if the mode is not switched to fine spot detection, the process proceeds to step # 140, and the correlation calculation is continuously performed for the entire second island (# 145).
When switching to the fine spot detection, the flag in the fine spot block calculation is set to "calculating"(# 130), the correlation calculation is performed for the fine spot block (# 135), and the process proceeds to step # 30 in FIG. Return.

If it is determined in step # 115 that the fine spot block has already been calculated, the correlation calculation for the fine spot block is continued (# 13).
5) Return to step # 30. Once the flag for calculating the fine spot block is set, step # 10
The state is maintained until the setting is canceled at step # 150 after step 5, and thus fine spot detection is continued until there is no instruction by operating the fine spot AF switch.

FIGS. 8 and 9 show the flow of the process for judging whether or not to switch to the fine spot block operation in step # 120. FIG. 8 shows a determination process based on the remaining drive amount of the focus lens. First, the flag indicating that the fine spot block calculation is to be performed is cleared (step # 205). Next, a correlation operation is performed on the entire second island, the amount of defocus is detected, the drive amount required to move the focus lens to the in-focus position is calculated, and the focus lens is already output from the output of the encoder 43. The drive amount is measured, and the measured drive amount is subtracted from the calculated drive amount, thereby obtaining the remaining drive amount required to move the focus lens to the in-focus position (# 2).
10).

Then, the obtained remaining drive amount is determined by the photographing lens 1.
(# 215), and if the remaining drive amount is equal to or smaller than the determination reference value A, the flag indicating that the fine spot block calculation is to be performed is set to "Yes". (# 220), and FIG.
Return to step # 125. The remaining drive amount is the judgment reference value A
If it exceeds, step # with the flag released
Return to 125.

FIG. 9 shows a judgment process based on the amount of defocus. First, the flag indicating that the fine spot block calculation is to be performed is cleared (step # 255). Then
A correlation operation is performed on the entire second island to detect a focus shift amount Df, and the detected shift amount Df is compared with a predetermined reference value B according to the focal length of the photographing lens 1 (# 260). If the deviation amount Df is equal to or smaller than the determination reference value B, a flag indicating that the fine spot block calculation is performed is set to “Yes” (# 265), and if the deviation amount Df exceeds the determination reference value B, the flag is released. Then, the process returns to step # 125 of FIG.

FIG. 10 shows the flow of lens drive control in step # 40 of FIG. First, it is determined whether or not focus detection was possible by the correlation operation performed in step # 25 (step # 305). When the focus detection is possible, the flag indicating that the low contrast scan is being performed is released, and the flag indicating that the low contrast scan is prohibited is set to “prohibited” (# 31).
0). Then, based on the result of the correlation operation, step # 3
A drive amount of the focus lens is calculated based on the shift amount detected in step 5, the position of the focus lens at that time, and the position of the focus lens at an intermediate point in the integration period of the CCD, and according to the calculated drive amount, The focus lens is driven (# 315), and the process returns to step # 5 in FIG.

If the focus cannot be detected in step # 305, it is determined whether or not low-contrast scanning is prohibited (# 320). If the low-contrast scan is prohibited, step # is performed without driving the focus lens. Return to 5. Scanning is prohibited at step # 310 and at the time of completion of a scan (described later) (# 365). After the focus detection is once enabled or after the scan is completed, the low contrast scan is not performed. Therefore, when focus detection becomes impossible after fine spot detection is started, the focus lens is stopped at the position at that time.

If the scan is not prohibited, it is determined whether or not the low contrast scan has already been started (# 325). If not, the drive of the focus lens is started toward the near end (# 325). 330). At this time, it detects that the focus lens has reached the near end and activates a timer interrupt for stopping lens driving. Then, a flag indicating that scanning is being performed is set (# 335), and the process returns to step # 5 in FIG.

FIG. 11 shows the flow of the timer interrupt process. The encoder 43 determines whether the position of the focus lens is changing, that is, whether the motor 8a is rotating.
(Step # 405), and if there is no change in the lens position, it is determined that the focus lens has reached the near end or the infinity end, and the lens driving, that is, the motor 8a is stopped (# 410). If the lens position has changed, no processing is performed.

Returning to FIG. 10, if the low-contrast scan has already been started in the determination of step # 325, it is determined whether or not the focus lens has stopped (# 340). Step # 5
Return to Thus, the ongoing low contrast scan is continued.

If the focus lens has been stopped, it is determined whether or not focus detection has been performed with the focus lens stopped (# 345). If focus detection has not been performed, step # 5 is performed.
Return to As a result, the focus lens is kept at the stop position, that is, the near end or the infinite end, and the focus detection at the stop position is attempted in step # 25.

If focus detection is being performed in a stopped state, it is determined whether or not the focus lens is located at the near end (# 350). When the focus lens is located at the near end, the low-contrast scan is not completed, and the focus detection is still impossible, so that the drive of the focus lens is started toward the infinite end side (# 3
55). At this time, similarly to the drive to the near end side, it detects that the focus lens has reached the infinite end and activates a timer interrupt of FIG. 11 for stopping the lens drive.
Then, the process returns to step # 5.

If the focus lens is not located at the near end in the determination at step # 350, the focus lens is located at the infinite end. In addition, focus detection at the infinite end was not performed, and the low-contrast scan was unsuccessful. At this time, the focus lens is moved to a predetermined position where the focus can be detected in a wide distance range (# 360). This predetermined position is determined according to the focal length of the taking lens 1. Thereafter, the flag indicating that scanning is being performed is released, the flag indicating that scanning is prohibited is set to “prohibited” (# 365), and the process returns to step # 5.

By the above-described control processing, even when the fine spot detection is instructed, the focus adjustment based on the correlation calculation of the entire second island is performed until the taking lens 1 is brought into a state close to the focus, and the focus adjustment is performed. The focus adjustment based on the correlation calculation of the fine spot block is performed only when the state is close. Therefore, when the fine spot detection is started, the subject to be subjected to focus adjustment is clearly imaged somewhere on the second island, and the image formation position of the object is determined by the fine spot block. If it is on the second block including the focus, the focus can be reliably detected by the correlation operation of the fine spot block.

Even if the image formation position of the object is not on the second block but on the first or third block, as shown in FIG. 5, half of the fine spot block is also in the first and third blocks. Since it is included, there is a high possibility that the focus can be detected by the correlation operation of the fine spot block.

Even if the subject forms an image in the first or third block and the focus cannot be detected at the image position by the correlation calculation of the fine spot block, the focus can be detected once as described above. After that, the low contrast scan is prohibited, so that the low contrast scan is not performed by the fine spot detection. In this case, the user can slightly change the direction of the camera to the left or right to position the subject on the fine spot block, thereby immediately enabling focus detection by correlation calculation of the fine spot block.

When the focus cannot be detected by the correlation calculation prior to the fine spot detection, a low contrast scan is performed. During this scan, the correlation calculation is performed not on the limited fine spot block but on the wide first to third blocks. Therefore, as compared with the conventional method of performing low-contrast scan while performing the correlation calculation of the fine spot block, there is a higher possibility of finding the position of the focus lens where the focus can be detected, and the required time is shortened.

When finding a focus lens position at which focus can be detected by low-contrast scan is unsuccessful, the focus lens can be used for both low-contrast scan prior to fine spot detection and low-contrast scan for normal focus detection. Is moved to a position where focus detection can be performed over a wide distance range, instead of stopping at the near end or infinity end, so that the finder image is unlikely to be largely blurred. Moreover, the focus detection can be performed promptly when the start of the focus adjustment is next instructed.

In the camera of the present embodiment, the fine spot block is set only on the second island among the first to fourth islands of the line sensor, but the fine spot block is set on the other islands. Is also good. In that case, it is preferable to set the fourth island located at the center of the second island.

In this case, a fine spot block is set only in the second block at the center of the second island, but a fine spot block is also set in the first block and the third block, and the fine spot block is set according to the image forming position of the subject. Either one can be selected. However, if the above-described control is used, the reliability of focus detection is extremely high even with a single fine spot block, so it is not necessary to add a fine spot block on the same island which would complicate the control process. It can be said that.

[0087]

According to the autofocus camera of the present invention, the focus is adjusted based on the image of the large detection area, and the focusing is performed based on the image of the small detection area after the photographic lens is brought into close focus. The certainty of accurately focusing the lens on a narrow range of the subject is greatly improved. This greatly reduces the necessity of performing low-contrast scanning, and enables quick and accurate focus adjustment. In addition, low-contrast scanning in which the viewfinder image is blurred at the end of scanning due to an increase in power consumption. The accompanying inconvenience can be avoided.

By instructing whether or not to perform focus adjustment based on the image of the second area by a predetermined signal, it is possible to avoid the waste of always performing strict focus adjustment ignoring shooting conditions. When the predetermined signal is generated according to the operation of the user, the intention of the user can be reflected in the focus adjustment, and the predetermined signal is automatically generated according to the type of the photographing lens. Then, the focus adjustment suitable for the characteristics of the photographing lens can be performed without bothering the user.

Further, by limiting the comparison range when finding a part corresponding to the image of the second area, focus adjustment can be performed more quickly, and the risk of erroneous detection is greatly reduced, and focus adjustment is performed. Is further improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a single-lens reflex camera according to an embodiment of the present invention.

FIG. 2 is a diagram showing an optical system of an AF sensor unit of the camera.

FIG. 3 is a diagram showing a positional relationship between a refocused image, a front focus image, and a rear focus image of the camera.

FIG. 4 is a diagram schematically showing a configuration related to an arrangement of a line sensor and a focus adjustment of the camera.

FIG. 5 is a diagram showing an array of pixels in a reference portion and a reference portion of a line sensor of the camera.

FIG. 6 is a flowchart showing a schematic flow of the entire process of focus adjustment of the camera.

FIG. 7 is a flowchart showing a flow of a focus position detection calculation process in the focus adjustment process of the camera.

FIG. 8 is a flowchart showing the flow of a first determination process as to whether or not to perform a fine spot block calculation in the focus adjustment process of the camera.

FIG. 9 is a flowchart showing the flow of a second determination process as to whether or not to perform a fine spot block operation in the focus adjustment process of the camera.

FIG. 10 is a flowchart showing the flow of lens drive control processing in the focus adjustment processing of the camera.

FIG. 11 is a flowchart showing the flow of a timer interrupt process for detecting that the focus lens has reached a near end or an infinite end and stopping lens driving.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photographing lens 2 photographing film 3 reflecting mirror 4 focusing plate 5 pentaprism 6 AF sensor unit 7 AF control unit 8 lens driving unit 8 a motor 9 sub-reflecting mirror 10 line sensor 10 a to 10 d line sensor island 11 display unit 12 condenser lens 13 reflection Mirror 14 imaging lens 15L, 15R CCD 16 CCD control circuit 31 A / D converter 32 RAM 33 focus detection unit 34 lens drive control unit 35 timer circuit 36 sensor control unit 41 lens data output unit 42 fine spot AF switch 43 encoder

Claims (5)

[Claims] 1. A different portion of a light beam transmitted through a photographing lens is guided to two sensors, respectively, and an image detected by one sensor is compared with an image detected by the other sensor to detect a positional shift of a corresponding portion. An auto-focus camera that adjusts the focus of the taking lens so that the position shift is eliminated, and detects an image of the first area of one of the sensors and a first area smaller than the first area to detect the position shift. In the method of selecting and using the image of the second area, the amount of drive of the focus setting lens of the photographing lens required to eliminate the position shift is calculated from the position shift detected using the image of the first area. Driving amount calculating means, and starting the focus adjustment of the photographing lens based on the positional deviation detected using the image of the first area, after the driving amount calculated by the driving amount calculating means becomes equal to or less than a predetermined value, Or the first territory Focus adjusting means for adjusting the focus of the photographing lens based on the positional deviation detected using the image of the second area after the magnitude of the positional deviation detected using the image of the second area becomes equal to or less than a predetermined value; An autofocus camera, comprising: And a signal generating means for providing a predetermined signal for instructing an adjusting operation to the focus adjusting means, wherein the focus adjusting means comprises:
When the predetermined signal is given, focus adjustment of the photographing lens is performed based on the displacement of the position detected using the image of the second area, and when the predetermined signal is not given, the first lens is adjusted.
2. The autofocus camera according to claim 1, wherein the focus adjustment of the photographing lens based on the position shift detected using the image of the area is continued. 3. The auto-focusing device according to claim 2, wherein the signal generating means supplies the predetermined signal to the focus adjusting means in accordance with an operation state of an operation member provided on the camera body or the photographing lens. camera. 4. The signal generating means obtains information indicating the type of lens from the photographing lens, and supplies the predetermined signal to the focus adjusting means when the photographing lens is a lens of a predetermined type. The autofocus camera according to claim 2. 5. When comparing an image detected by one sensor with an image detected by the other sensor to find a corresponding portion, when the image of the second area of one sensor is used, the first 2. The autofocus camera according to claim 1, wherein a comparison is made with a narrower range of the image of the other sensor than when using the image of the area.