JPH11258493A - Focal point detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with the large memory capacity even when a supposed number of focal point detecting areas is much and to detect a focal point with high accuracy by operating a focal condition of an objective on the basis of a signal related to a focal condition and a signal related to the correction. SOLUTION: A focal point operating means 14 performs the operation with the focal deviation amount obtained by a focal point detecting means 12 and a correction value obtained by an operating means 13 to calculate the corrected focal point detecting signal. The corrected focal point detection signal is kept as it is or converted into a lens driving amount or the like according to the necessity, and then transmitted to a lens control means 5 through a contact 16. The lens control means 5 controls a driving device 3 on the basis of a received signal for moving all or a part of the lenses which form an image pick-up optical system 2 to adjust the focal condition of the an image pick-up lens 1. Whereby a focal point detecting device by which the focal point detecting signal can be corrected with high accuracy, and the focal point can be detected with high accuracy, can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographing device such as a photographic camera or a video camera, or a focus detection device applicable to various observation devices. More specifically, the present invention relates to a focus detection device that enables two-dimensional or continuous focus detection in a plurality of regions over a wide range on a photographing screen or an observation screen.

[0002]

2. Description of the Related Art Conventionally, there is a so-called image shift method as a light receiving type focus detection method using a light beam passing through an objective lens. This image shift method is disclosed in, for example,
No. 073111 and JP-A-59-107313.

FIG. 11 is a block diagram of a main part of a conventional camera in which a focus detection device is incorporated. In the figure, 101 is an objective lens for photographing, 102 is a rotatable semi-transmissive main mirror, 103 is a reticle, 104 is a pentaprism,
Reference numeral 105 denotes an eyepiece, 106 denotes a sub-mirror, 107 denotes a film, and 108 denotes a focus detection device.

In FIG. 1, a part of light from a subject (not shown) passes through an objective lens 101 and is reflected upward by a main mirror 102 to form a subject image on a focusing screen 103. The subject image formed on the reticle 103 is reflected by the pentaprism 104 a plurality of times, and
5 through a photographer or an observer.

On the other hand, from the objective lens 101 to the main mirror 10
The other part of the light beam that has reached 2 passes through the translucent main mirror 102, is reflected downward by the sub-mirror 106, and is guided to the focus detection means 108.

FIG. 12 shows the focus detecting means 108 shown in FIG.
FIG. 4 is an explanatory diagram for explaining the principle of focus detection in FIG. This drawing shows only the objective lens 101 and the focus detection device 108 in FIG.

In the focus detection device 108 shown in FIG.
Reference numeral 109 denotes a field mask arranged near a predetermined focal plane of the objective lens 101, that is, a plane conjugate to the film plane. Reference numeral 110 denotes a field lens also arranged near the predetermined focal plane.
Numeral 11 denotes a lens 2 composed of two lenses 111-1 and 111-2.
The next imaging system 112 has two lenses 111-1, 111-
2 and two sensor rows 11 arranged behind them.
A photoelectric conversion element including 2-1 and 112-2, a stop 113 having two openings 113-1 and 113-2 arranged corresponding to the two lenses 111-1 and 111-2, 1
Reference numeral 14 denotes an exit pupil of the objective lens 101 including the two divided regions 114-1 and 114-2.

Incidentally, the field lens 110 is
3 opening portions 113-1 and 113-2 are connected to the objective lens 101.
Of the exit pupil 114 in the vicinity of the regions 114-1 and 114-2.
The light fluxes 115-1 and 115-2 transmitted through -2 form light quantity distributions of the subject image in the two sensor rows 112-1 and 112-2, respectively.

The focus detection principle of the focus detection means shown in FIG. 12 is generally called a phase difference detection method, and the image forming point of the objective lens 101 is located in front of a predetermined focal plane, that is, on the objective lens 101 side. In some cases, two sensor rows 112-
1. In the case where the light quantity distributions of the subject images formed on the light-emitting elements 1, 112-2 are close to each other, and the image forming point of the objective lens 101 is on the rear side of the predetermined focal plane, that is, on the opposite side to the objective lens 101. Has two sensor rows 112-
The light amount distributions of the subject images formed on the respective 1, 112-2 are separated from each other.

Moreover, the two sensor arrays 112-1 and 112
Since the amount of deviation of the light amount distribution with respect to the subject image formed on -2 has a certain functional relationship with the amount of defocus, that is, the amount of defocus of the objective lens 101, if the amount of deviation is calculated by appropriate arithmetic means, The direction and amount of defocus can be detected.

The focus detecting means shown in FIG.
01 allows focus detection only for an object existing in one central area of the range observed or photographed. On the other hand, a focus detection device capable of detecting a focus even on an object located outside the center of an observation or photographing range is disclosed by the present applicant in, for example, Japanese Patent Application Laid-Open No. 7-159684.

FIG. 13 is a schematic diagram showing the configuration of an optical system disclosed in the publication. In the figure, reference numeral 116 denotes a field mask, which has a cross-shaped opening 116-1 in the center and vertically elongated openings 116-2 and 116-3 in peripheral portions on both sides. Reference numeral 117 denotes a field lens.
It comprises three portions 117-1, 117-2, 117-3 corresponding to the two openings 116-1, 116-2, 116-3. Reference numeral 118 denotes an aperture, and four apertures 118-1a and 118-1 are provided at the center, one pair at the top, bottom, left, and right.
b, central opening 1 with 118-1c, 118-1d
18-1 and one to two openings 1 in the left and right peripheral portions.
18-2a, 118-2b and 118-3a, 118-
Peripheral openings 118-2 and 118-3 having 3b are provided, respectively.

Each area 11 of the field lens 117
Reference numerals 7-1, 117-2, and 117-3 function to form images of these openings 118-1, 118-2, and 118-3 near the exit pupil of an objective lens (not shown), respectively. 1
Reference numeral 19 denotes four pairs of eight lenses 119-1a and 119-1
b, 119-1c, 119-1d, 119-2a, 11
This is an optical member in which a secondary imaging system composed of 9-2b, 119-3a, and 119-3b is integrated, and is disposed behind each aperture of the stop 118.

Reference numeral 120 denotes a total of eight sensor rows 120-1.
a, 120-1b, 120-1c, 120-1d, 12
0-2a, 120-2b, 120-3a, 120-3b
, And is arranged so as to receive the image corresponding to each secondary imaging system lens.

FIG. 14 shows a state of a subject image formed on the photoelectric conversion element 120. 121-1a,
Reference numerals 121-1b, 121-1c, and 121-1d denote apertures 118-1a, 118-1b, and 118 of light beams transmitted through the central opening 116-1 of the field mask 116 and the central portion 117-1 of the field lens 117, respectively. -1c, 118
-1d, the lenses 119-1a, 119-1b, 119-1c, and 1-12c of the secondary imaging system 119 behind the lens 11d.
Reference numerals 19-1d denote image areas formed on the photoelectric conversion element 120, respectively.

Reference numerals 121-2a and 121-2b denote a light beam transmitted through an opening 116-2 around the field mask 116 and a peripheral portion 117-2 around the field lens 117.
After being regulated by the 18 apertures 118-2a and 118-2b, the lens 119- of the secondary imaging system 119 behind it is controlled.
2a and 119-2b indicate image areas formed on the photoelectric conversion element 120.

Similarly, reference numerals 121-3a and 121-3b denote light beams transmitted through the aperture 116-3 around the field mask 116 and the peripheral portion 117-3 around the field lens 117, and the apertures 118-3a and 118-3b of the stop 118. After being regulated by the lens 119 of the secondary imaging system 119 behind it
-3a and 119-3b indicate image areas formed on the photoelectric conversion element 120.

The focus detection principle of the focus detection means shown in FIG. 13 is the same as that shown in FIG. 12, and detects the relative position of the subject image in the column direction of the paired sensors. By taking the configuration, not only near the center of the range observed or photographed by the objective lens (not shown),
Focus detection can also be performed on an object at a position corresponding to the openings 116-2 and 116-3 around the field mask.

According to the present focus detecting means, it is possible to perform focus detection even on an object whose light amount distribution changes only in one direction up and down or left and right in the vicinity of the center.

When these focus detecting means are used in a camera such as a single-lens reflex camera whose photographing lens is replaceable, if the lens is controlled based on a focus state detection signal relating to a directly obtained defocus amount, an appropriate focus can be obtained. You may not get the status. The main reason is that the luminous flux of the objective lens for forming an image to be observed or photographed and the luminous flux captured by the focus detection means are generally different. Further, in the focus detection means of the phase difference detection method, the focus position or the defocus amount which should be originally determined by the vertical (optical axis) aberration amount is converted into an image shift related to the horizontal aberration. Therefore, when the objective lens has an aberration, it is conceivable that there is a difference between the two depending on the state of the aberration correction.

In order to solve such a problem, for example, a focus detection signal D indicating the amount of defocus is corrected by using D _C = D C） (1) using a correction value C unique to each objective lens. correcting means is provided, it is also known to control the lens based on the obtained corrected focus detection signal D _C for.

[0022]

Since the correction value specific to each lens generally depends on the position of the focus detection area of the focus detection means, it has a focus detection area other than the center as shown in FIG. In such a case, it is necessary to have a correction value corresponding to each area. However, when the number of assumed focus detection areas is large, a large storage capacity is required to have correction values for all the detection areas on the objective lens side or the camera side.

Further, a change in the position of the focus lens in the objective lens (that is, a subject distance for focusing),
If the change in the focal length of the zoom lens or the variation in the aberration of the objective lens due to the change in the aperture during shooting is large, the correction value according to the movement state of the lens that moves during focusing or zooming, or the aperture, must be changed. Must have a larger storage capacity.

If an imaging system such as a single-lens reflex camera or an interchangeable lens that operates only at a certain position or a certain number of focus detection areas already exists, a focus different from the position or number of the focus detection areas is used. New cameras equipped with detection means will not function properly in this system.

One method for solving this problem is disclosed by the present applicant in Japanese Patent Application Laid-Open No. Hei 6-331886. This is based on the assumption that the correction value C depends only on the distance L from the center of the focus detection area, and that the change can be expressed by a certain function related to L, and the correction for two or more focus detection areas at a specific position is performed. The correction value of the focus detection area at another position is complemented by a function of, for example, a first-order equation or a second-order function.

In the above method, since it is assumed that the correction value C depends only on the distance L from the center of the focus detection area, the focus detection means for detecting the focus of each area is different, and the focus detection means is different from the output signal. When there is no characteristic or correlation, or when the focus detection means does not have axial symmetry with respect to the optical axis of the objective lens, it becomes difficult to accurately obtain the correction value.

The present invention further improves the focus detection device proposed earlier by the present applicant, and does not require a large storage capacity even when the number of focus detection areas is assumed to be large, and achieves accurate focus detection. An object of the present invention is to provide a focus detection device capable of obtaining a correction of a detection signal and performing high-accuracy focus detection.

[0028]

According to the present invention, there is provided a focus detecting device comprising: (1-1) focus detecting means for obtaining signals relating to a focus state of an objective lens for a plurality of areas on a predetermined focal plane of the objective lens; Storage means for storing a constant set for each state of the objective lens; lens state detection means for detecting each state of the objective lens; two or more lens states set for each area of the predetermined focal plane Using a parameter and a constant obtained from the storage unit, a correction value calculation unit that obtains a signal related to correction at the time of focus detection of each area by a predetermined calculation procedure, based on the signal related to the focus state and the signal related to the correction. And a focus calculating means for calculating a focus state of the objective lens.

In particular, (1-1-1) the focus detection means includes at least a pair of secondary imaging lenses and sensors respectively corresponding thereto, and the amount of light related to two subject images formed on the sensors. Detecting a focus state of the objective lens from a relative positional relationship between corresponding portions of the distribution.

(1-1-2) The focus detecting means has no rotational symmetry with respect to the optical axis of the objective lens or an axis optically equivalent to the optical axis of the objective lens.

(1-1-3) The parameter is a two-dimensional coordinate value with respect to a coordinate system defined on the predetermined focal plane or a plane equivalent thereto.

(1-1-4) The predetermined calculation procedure is a calculation of a predetermined function determined by characteristics of the objective lens using the parameter as a variable.

(1-1-5) The objective lens is configured to be separable from a camera body including the focus detection means.

(1-1-6) There are a plurality of types of the objective lens, and the objective lens is replaced and mounted on the camera body.

(1-1-7) The correction value calculation means is located on the camera body side.

(1-1-8) The correction value calculation means is on the objective lens side.

(1-1-9) The area on the predetermined focal plane of the objective lens is divided into a plurality of partial areas, and the two or more parameters are set corresponding to the position of each partial area. That you are.

(1-1-10) The parameters are a plurality of values determined by coordinate values of the center of the partial area.

(1-1-11) The objective lens has a variable focal length by moving all or a part of the lens constituting the objective lens. To detect the moving state of a moving lens or an amount characterizing the moving state.

(1-1-12) The objective lens can focus on an object at a predetermined distance by moving a focus lens including all or a part of the objective lens. It is possible that the lens state detecting means detects a moving state or an amount characterizing the moving state of the focus lens.

(1-1-13) The objective lens has an aperture,
The diameter of the aperture is variable during photographing or observation, and the lens state detecting means detects the diameter of the aperture of the objective lens or an amount characterizing the diameter of the aperture. And so on.

(1-2) focus detection means for obtaining signals relating to the focus state of the objective lens for a plurality of regions on the predetermined focal plane of the objective lens, lens state detection means for detecting each state of the objective lens, Using the two or more parameters set corresponding to each region of the predetermined focal plane and the parameters determined for each state of the objective lens, a predetermined calculation procedure is used to detect the focus of each region. Correction value calculating means for obtaining a signal related to correction, focus calculating means for calculating the focus state of the objective lens based on the signal related to the focus state and the signal related to the correction, all or some of the lenses constituting the objective lens. Driving means for driving, and the driving means drives all or some of the lenses constituting the objective lens based on the calculation result of the focus calculating means, thereby driving the focus state of the objective lens. It is characterized by adjusting the.

[0043]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a main part of a first embodiment of the present invention, and is a conceptual diagram for explaining an operation of a photographing apparatus including a focus detecting device. In the figure, reference numeral 1 denotes a lens body having a photographic lens as an objective lens. The lens body includes one or a plurality of lens groups, and the focal length can be changed by moving all or a part of the lens group. Possible photographing optical system (photographing lens) 2, lens state detecting means 37 for detecting the focal length of photographing optical system 2, that is, the zoom state, and moving all or a part of the lens constituting photographing optical system 2 Let the shooting lens 1
And a storage means 4 such as a ROM and a lens control means 5 for controlling them.

Here, the lens state detecting means 37 is a known method, for example, an encoder electrode provided on a lens barrel that rotates or moves to change the focal length of the photographing optical system 2 and a detection electrode in contact therewith. The movement state of the lens that moves when the focal length (zoom state) of the photographing optical system 2 is changed or the amount characterizing the movement state is detected by using the above method.

On the other hand, reference numeral 6 denotes a camera (camera body).
Inside, a main mirror 7, a reticle 8 on which an object image is formed, a pentaprism 9 for image inversion, and an eyepiece 1
0, and each of these elements constitutes a finder system. Further, a sub-mirror 11, focus detection means 12, calculation means (correction value calculation means) 13, camera control means (focus calculation means) 14, film (photoconductor) 1 as a photographing medium
5 is included. The photographing lens 1 and the camera body 6 have a contact 16, and when they are attached to each other, communication of various information and power supply are performed via the contact 16.

FIG. 2 is an explanatory diagram of a detailed configuration of elements relating to the focus detection means 12 of FIG. In the figure, reference numeral 17 denotes an optical axis of a photographing lens, 18 denotes a film equivalent to the photosensitive surface 15 in FIG.
1 is a semi-transmissive main mirror arranged on the optical axis 17 of the taking lens 2 and equivalent to the main mirror 7 of FIG. 1, and 20 is similarly arranged obliquely on the optical axis 17 of the taking lens 2 in FIG. A first reflecting mirror 21 having the function of the sub-mirror 11 is a paraxial imaging plane conjugated to the film 18 by the first reflecting mirror 20.
2 is a second reflecting mirror, 23 is an infrared cut filter, 24
Denotes an aperture, which has two openings 24-1 and 24-2.

Reference numeral 25 denotes a secondary image forming system, which has two lenses 25-1 and 25-2 arranged corresponding to the two apertures 24-1 and 24-2 of the diaphragm 24. 36 is a third reflecting mirror, 26 is a photoelectric conversion element (sensor) and has two area sensors 26-1 and 26-2.

Here, the first reflecting mirror 20 has a curvature,
It has convergence power (refractive power) for projecting the two apertures 24-1 and 24-2 of the aperture 24 near the exit pupil of the photographing lens 2.

The first reflecting mirror 20 is formed by depositing a metal film such as aluminum or silver so that only a necessary area reflects light, and also functions as a field mask for limiting a range in which focus detection is performed. I have. The other second and third reflecting mirrors 22 and 36 also reduce stray light incident on the photoelectric conversion element.
Only the minimum required area is deposited. It is preferable to apply a light-absorbing paint or the like to a region that does not function as a reflecting surface of each reflecting mirror.

FIG. 3 is a plan view of the diaphragm 24 shown in FIG. The diaphragm 24 has a configuration in which two horizontally long openings 24-1 and 24-2 are arranged in a direction in which the opening width is narrow. The dotted lines in the figure indicate the lenses 25-1 and 25-2 of the secondary imaging system 25 disposed behind and corresponding to the apertures 24-1 and 24-2 of the diaphragm 24. is there.

FIG. 4 is a plan view of the photoelectric conversion element 26 of FIG. The two area sensors 26-1, 26 shown in FIG.
Reference numeral -2 indicates two area sensors in which pixels are two-dimensionally arranged as shown in FIG.

In the configuration shown in FIG. 2 having the above-described components, the light beams 27-1 and 27-2 from the photographing lens 2 pass through the half mirror surface of the main mirror 19 and then pass through the first reflecting mirror 20.
Is reflected in a direction substantially along the inclination of the main mirror 19, the direction is changed again by the second reflecting mirror 22, and then the two apertures 2 of the diaphragm 24 are passed through the infrared cut filter 23.
4-1 and 24-2, each lens 2 of the secondary imaging system 25
The light is condensed by 5-1 and 25-2, and the area sensors 26-1 and 26 of the photoelectric conversion element 26 via the third reflecting mirror 36.
-2 respectively.

The light beams 27-1 and 27-2 in the drawing indicate the light beams that form an image at the center of the film 18, but the light beams that form an image at other positions also undergo photoelectric conversion through the same path. After reaching the element 26, the two light amount distributions of the subject image corresponding to a predetermined two-dimensional area on the film 18 as a whole are obtained by the area sensors 26-1 and 26-2 of the photoelectric conversion element 26.
6-2.

In the present embodiment, the first surface of the secondary imaging system 25 has a concave shape, so that light incident on the secondary imaging system 25 is not forcibly refracted. Good and uniform imaging performance is secured over a wide range of the two-dimensional area of the photoelectric conversion element 26. Incidentally, the first reflecting mirror 2
Numeral 0 is for retracting out of the optical path for photographing in the same manner as the main mirror 19 during photographing.

The focus detecting means 12 shown in FIG. 1 applies the light amount distribution of the two subject images obtained in this manner to the light amount distribution based on the same detection principle as a well-known focus detecting method.
The photographing lens is obtained by calculating the separation direction of the subject image, that is, the vertical positional relationship between the two area sensors 26-1 and 26-2 shown in FIG. 4 at each position of the area sensors 26-1 and 26-2. 1 is detected, and the result is output as the defocus amount D.

According to the focus detecting means 12 described above, it is possible to detect the focus state at almost any point in the area of the film 18 corresponding to the area sensor 26, that is, in the focus detecting area.

A focus detectable area 2 as shown in FIG.
It is also possible to enable focus detection only at specific discrete positions indicated by rectangles in FIG. In this case, for example, a liquid crystal display element having a rectangular pattern shown in FIG. 5 is provided near the focusing screen 8 in FIG. Can be displayed.

As described above, when the defocus amount D representing the focus state obtained from the relative positional relationship between the two images formed on the sensor 26 is used as it is and the photographing lens is controlled, an error occurs and accurate focusing is performed. Since it cannot be performed, it is necessary to correct the defocus amount D obtained at each position with a correction value corresponding to each position.

However, as is apparent from the structure of the focus detecting means, the focus detectable area 28 of FIG. 5 has only line symmetry with respect to the vertical line 30 passing through the center 29 thereof, and has line symmetry with respect to the horizontal line 31. And there is no rotational symmetry with respect to a straight line passing through the center 29 and perpendicular to the page. Therefore, the characteristic of each point in the focus detectable area 28 is the center point 2
The correction value cannot be defined only by the distance from the center point 29, and cannot be expressed only by the distance from the center point 29. Therefore, in the present embodiment, the calculation and correction of the correction value are performed by the following method.

Calculation means (correction value calculation means) in FIG.
Reference numeral 13 calculates a correction value C using two or more parameters corresponding to a region where focus detection is to be performed. For example, assuming that the area for which focus detection is to be performed is the area 32 in FIG. 5, the following equation is used with the coordinates x and y of the center 33 of this area whose origin is the center 29 of the focus detectable area. The correction value C is obtained by the following.

[0061]

(Equation 1) Here, i and j are continuous or discontinuous integers in a predetermined range. a _ij is a constant determined by i and j,
The setting is made for each state detected by the lens state detecting means. These constants are stored in the storage means 4 in the taking lens 1.
And the lens state detecting means 37
The value corresponding to the lens state detected by is selected,
Prior to the calculation of the equation (2), the data is transferred from the lens control means 5 to the camera control means 14 via the contact 16.

Further, x and y, which are parameters indicating a region for which focus detection is performed, are not limited to coordinates on a predetermined focal plane or a film plane, and coordinates on a plane equivalent to these and some conversion are performed. The coordinates may be used. The unit of the coordinate value may be standardized so as to be optimal for the calculation of the expression (2).

The camera control means (focus calculation means) 14 uses the defocus amount D obtained by the focus detection means 12 and the correction value C obtained by the calculation means 13 from the equation (2), and A similar operation is performed to obtain the corrected focus detection signal D
Calculate _C. After correcting the focus detection signal D _C is converted to it, or the lens driving amount and the like if necessary, contact 1
The signal is sent to the lens control means 5 via the reference numeral 6. The lens control means 5 controls the driving device 3 based on the received signal to move all or a part of the lens constituting the photographing optical system 2 and adjust the focus state of the photographing lens 1.

FIGS. 6 (A), (B) and (C) show 28 mm
FIG. 9 is a bird's-eye view showing correction values C in three regions (first, second, and third regions) in a zoom region from a wide-angle end to a telephoto end of a zoom lens having a focal length range from to 80 mm. The correction values for the possible area 34 are indicated by continuous curved surfaces 35-1 to 35-3. The change in the curved surface representing the correction value according to the focal length f as shown in FIG.
It can be approximated with high accuracy by an equation in the form of an equation. In the case of the present embodiment, specific values of the eigen constants a _ij are as follows. (A) First area a ₀₀ = -1.92192 × 10 ^-2 a ₀₁ = -3.53386 × 10 ^-3 a ₀₂ = -9.99921 × 10 ^-3 a ₂₀ = -9.79780 × 10 ^-4 a ₂₁ = 3.34633 × 10 ^-6 a ₂₂ = 2.17978 × 10 ⁻⁴ (B) Second area a ₀₀ = −3.000709 × 10 ⁻² a ₀₁ = −1.96670 × 10 ⁻³ a ₀₂ = −4.66583 × 10 ⁻³ a ₂₀ = −6.94517 × 10 ⁻⁴ a ₂₁ = -1.93460 × 10 ^-5 a ₂₂ = 1.23437 × 10 ^-4 (C) Third region a ₀₀ = -4.22666 × 10 ^-2 a ₀₁ = -1.15450 × 10 ^-3 a ₀₂ = 6.03941 × 10 ^-4 a ₂₀ = 1.20797 × 10 ⁻⁴ a ₂₁ = −2.74064 × 10 ⁻⁵ a ₂₂ = 1.07257 × 10 ^{−5 The} correction value C is a quadratic expression relating to x and y. The coefficients a _1j (j = 0, 1, 2) are all 0, and the values of the correction values C at all positions in the focus detectable area are represented by six coefficients.

The number of divisions of the region and the width of each region are determined by the allowable range of the focus detection accuracy after correction, and are appropriately determined according to the specifications and purpose of the photographing lens (objective lens). The value of the coefficient for calculating the correction value in an area having a certain width is a coefficient by which the average value of the correction values at two end points of each area is calculated. The width of the error is minimized.

When the focus detection area is divided into predetermined partial areas as shown in FIG.
The x ⁱ y ⁱ portion of equation (3) for x and y is calculated in advance, and x ⁱ instead of x and y is used as a parameter.
The value of y ⁱ is stored in the storage means on the camera side, and (2)
If the data is read at the time of calculating the formula, the calculation time can be greatly reduced.

In the present embodiment, equation (2) is assumed as an arithmetic equation for obtaining the correction value. However, the present invention is not limited to this, and other equations such as a logarithmic function and a trigonometric function are used. It is also possible to use a function represented by a function or a combination thereof. If the error becomes large when the correction value is represented by one function for all the focus detection areas, the spline function that divides the focus detection area into several parts and continuously connects the correction values of each area is used. May be expressed as

Further, different focus detection means correspond to each focus detection area, and when the correction value does not continuously change over the entire focus detection area, a different function is defined for each area, The correction value may be obtained by an operation suitable for each area.

On the other hand, when the present invention is applied to a system such as a single-lens reflex camera in which many types of photographing lenses are exchanged and used, it is not possible to limit the calculation method for obtaining a correction value to one. In this case, a plurality of types of methods may be prepared in advance, and information specifying the type of function to be used and the method of the operation procedure may be read from the lens body together with constants required for calculating the correction value.

FIG. 7 is a block diagram showing a main part of the second embodiment of the present invention. 7, the same components as those in FIG. 1 are denoted by the same reference numerals. This embodiment is different from the first embodiment in that the calculating means 13 provided on the camera body 6 side in FIG.
Is located on the lens body 1 side as the calculating means 13 '. The calculation of the correction value and the correction of the focus detection signal according to the present embodiment are performed as follows.

First, the lens control means 5 converts the coordinates x and y representing the position of the focus detection area where focus detection is to be performed, into the camera body 6.
The lens-side calculation means 13 ′ receives the value via the contact point 16 and the camera control means 14, and the coefficient data a in the storage device 4 according to the detection result of the lens state detection means 37.
_The correction C is calculated by performing the calculation of Expression (2) using _ij .
The correction value C is sent to the camera control means 14 of the camera body 6 via the lens control means 5 and the contact point 16, and thereafter, the correction of the focus detection signal and the driving of the photographing lens are performed in the same manner as in the first embodiment. .

Although the first embodiment shown in FIG. 1 has a configuration in which all the calculations of the equation (2) necessary for calculating the correction value C are performed on the camera body 6 side, in the present embodiment, these calculations are performed. Since all the operations are performed on the lens body 1 side, the form of the arithmetic expression can be freely set according to each photographing lens, and there is an advantage that the optimum correction can be performed for each photographing lens.

In each of the above embodiments, the focal length (zoom state) of the photographing lens is focused on as a cause of the fluctuation of the aberration. Similarly, the focal length of the photographing lens is adjusted to cause the fluctuation of the aberration. The arrangement state of the focus lens (distance S of the focused object) is given.

FIG. 8 is a block diagram of a main part of a third embodiment of the present invention. FIG. 8 shows an embodiment focusing on the arrangement state of the focus lens. In FIG. 8, the photographing optical system 2 '
Is a single focus lens, and the lens state detecting means 37 'is different from the lens state detecting means 37 for detecting the focal length (zoom state) of the first embodiment shown in FIG. Is detected.

More specifically, as in the first embodiment, an imaging optical system includes an encoder electrode provided on a lens barrel for moving one or more lenses for focusing and a detection electrode in contact with the encoder electrode. The arrangement state of the 2 ′ focus lens (distance S of the focused subject) is detected.

FIGS. 9A, 9B, and 9C show focal lengths of three.
The arrangement state of the three focus lenses from the closest object to the object at infinity of the 00 mm single focus lens, that is, the distance of the in-focus subject is set in three regions (first, second, and third regions).
FIG. 13 is a bird's-eye view showing a correction value C for each of the curved surfaces 38-1 to 38 in which correction values for the focus detectable area 34 are continuous.
This is indicated by -3. The change of the curved surface representing the correction value according to the arrangement state of the focus lens (the distance of the focused object) as shown in these figures is expressed in the form of equation (2), and is shown in FIGS. Specific numerical values of the constants a _ij corresponding to the object distances s in B) and (C) are as follows. (A) First area a ₀₀ = 1.93344 × 10 ^-1 a ₀₁ = 8.74587 × 10 ^-5 a ₀₂ = -4.54790 × 10 ^-4 a ₂₀ = 7.36798 × 10 ^-5 a ₂₁ = 5.55151 × 10 ^-6 a ₂₂ = -1.51254 × 10 ^-5 (B) Second area a ₀₀ = -8.90515 × 10 ^-3 a ₀₁ = 6.998959 × 10 ^-4 a ₀₂ = 1.20506 × 10 ^-3 a ₂₀ = 1.26102 × 10 ^-3 a ₂₁ = -1.34973 × 10 ⁻⁵ a ₂₂ = 1.31262 × 10 ⁻⁶ (C) Third area a ₀₀ = −8.76691 × 10 ⁻² a ₀₁ = −1.95856 × 10 ⁻⁴ a ₀₂ = 1.64412 × 10 ⁻³ a ₂₀ = 1.25557 × 10 ^-3 a ₂₁ = 4.48096 coefficients a _ij for each arrangement of × 10 ^-6 a ₂₂ = -1.54401 × focus lens at 10 ^-7 present embodiment is stored in the storage means 4, the detected focus lens The coefficient a _ij according to the arrangement state is the contact 1
6 to the camera control means 14 of the camera body 6. Hereinafter, correction calculation and focusing on the camera side are performed in the same manner as in the first embodiment.

Of course, in this embodiment, the calculation of the correction value may be performed on the lens body 1 side as in the second embodiment.
Further, the third embodiment is applied to the zoom lens of the first embodiment, and is configured to detect both the zoom state and the arrangement state of the focus lens. The coefficient a _ij is set for each combination of the zoom state and the arrangement state of the focus lens. You may have it.

FIG. 10 shows the zoom state of a zoom lens having a focal length range from 28 mm to 105 mm.
Area (from the wide-angle end to the telephoto end (a),
(B), (c)) and the arrangement state of the focus lens in three regions (from the near end to infinity (a),
FIG. 10 is a bird's-eye view similar to FIGS. 6 and 9 showing the correction value C in each area in the fourth embodiment of the present invention divided into (a) and (c)).

In addition, since the aberration state generally varies depending on the aperture of the photographing lens at the time of photographing, and the amount to be corrected differs, information input from outside or information from a photometric system in the camera is used. Detects the aperture value at the time of shooting set based on
The correction of the present invention may be performed using the coefficient a _ij according to the correction.

[0080]

According to the present invention, by setting each element as described above, a large storage capacity is not required even when the number of assumed focus detection areas is large, and accurate focus detection is possible. By obtaining signal correction, it is possible to achieve a focus detection device capable of performing highly accurate focus detection.

In addition, according to the present invention, in a focus detection device having a wide focus detection area, a correction value required for focus detection or data for calculating a correction value is stored for each state that can be taken by a photographing lens. Since it is not necessary to have all the data in the camera body, it is possible to remarkably reduce the required capacity of the storage device for holding the data in the camera body or the photographing lens, and it is possible to obtain a more accurate correction value. Improvement of detection accuracy is realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a focus detection unit to which Embodiment 1 of the present invention is applied;

FIG. 3 is a diagram showing an aperture of a focus detection unit to which the first embodiment of the present invention is applied;

FIG. 4 is a diagram showing a photoelectric conversion element of a focus detection unit to which Embodiment 1 of the present invention is applied;

FIG. 5 is a diagram showing a focus detection area of a focus detection unit to which the first embodiment of the present invention is applied;

FIG. 6 is a diagram illustrating correction values according to the first embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a third embodiment of the present invention.

FIG. 9 is a diagram showing correction values according to the third embodiment of the present invention.

FIG. 10 is a diagram illustrating correction values according to a fourth embodiment of the present invention.

FIG. 11 is a diagram showing a conventional example of a camera having a focus detection device.

FIG. 12 is a diagram showing a first conventional example of a focus detection device.

FIG. 13 is a diagram showing a second conventional example of a focus detection device.

FIG. 14 is a diagram showing a photoelectric conversion element in a second conventional example of the focus detection device.

[Explanation of symbols]

 Reference Signs List 1 shooting lens 2, 2 'shooting optical system 3 driving device 4 storage device 5 lens control means 6 camera 7 main mirror 8 focusing plate 9 pentaprism 10 eyepiece 11 sub-mirror 12 focus detection means 13, 13' calculation means 14 camera control means DESCRIPTION OF SYMBOLS 15 Film 16 Contact 17 Optical axis of photographing lens 18 Film 19 Main mirror 20 First reflecting mirror 21 Imaging surface 22 Second reflecting mirror 23 Infrared cut filter 24 Aperture 25 Secondary imaging system 26 Photoelectric conversion element 27 Photographing Light flux from lens 28 Focus detectable area 29 Center of focus detectable area 30 Vertical line 31 passing through center 31 Horizontal line passing through center 32 Focus detect area 33 Center of focus detect area 34 Focus detectable area 35, 38 Curved surface indicating correction value 36 third reflecting mirror 37, 37 'lens state detecting means 101 objective lens 1 02 Main mirror 103 Focus plate 104 Pentaprism 105 Eyepiece 106 Submirror 107 Film 108 Focus detection device 109 Field mask 110 Field lens 111 Secondary imaging system 112 Photoelectric conversion element 113 Aperture 114 Objective lens exit pupil 115 Light flux 116 Field mask 117 Field lens 118 Aperture 119 Optical member 120 Photoelectric conversion element 121 Image on photoelectric conversion element

Claims (15)

[Claims] 1. Focus detection means for obtaining a signal relating to the focus state of the objective lens for a plurality of regions on a predetermined focal plane of the objective lens, and storage for storing constants set corresponding to each state of the objective lens. Means, a lens state detecting means for detecting each state of the objective lens, a predetermined operation using two or more parameters set corresponding to each area of the predetermined focal plane and a constant obtained from the storage means. Correction value calculating means for obtaining a signal related to correction at the time of focus detection of each area by a procedure, and focus calculating means for calculating a focus state of the objective lens based on the signal related to the focus state and the signal related to the correction. A focus detection device. 2. The apparatus according to claim 1, wherein the focus detection unit includes at least two pairs of secondary imaging lenses and sensors corresponding to the respective secondary imaging lenses.
2. A focus detection device according to claim 1, wherein a focus state of said objective lens is detected from a relative positional relationship between corresponding portions of light amount distributions of two subject images formed on said sensor. 3. The focus detecting device according to claim 2, wherein said focus detecting means has no rotational symmetry with respect to an optical axis of said objective lens or an axis optically equivalent to the optical axis of said objective lens. . 4. The focus detection apparatus according to claim 1, wherein the parameter is a two-dimensional coordinate value with respect to a coordinate system defined on the predetermined focal plane or a plane equivalent thereto. 5. The focus detection apparatus according to claim 1, wherein the predetermined calculation procedure is a calculation of a predetermined function determined by a characteristic of the objective lens using the parameter as a variable. 6. The focus detection device according to claim 1, wherein the objective lens is configured to be separable from a camera body including the focus detection unit. 7. The focus detection apparatus according to claim 6, wherein a plurality of types of said objective lenses are present and are exchanged and mounted on said camera body. 8. The focus detection device according to claim 6, wherein said correction value calculation means is provided on said camera body side. 9. The focus detection apparatus according to claim 6, wherein said correction value calculation means is provided on said objective lens side. 10. A region on the predetermined focal plane of the objective lens is divided into a plurality of partial regions, and the two or more parameters are set corresponding to the position of each partial region. The focus detection device according to claim 1, wherein 11. The focus detection apparatus according to claim 10, wherein said parameter is a plurality of values determined by a coordinate value of a center of said partial area. 12. The focal length of the objective lens is variable by moving all or a part of the lens that constitutes the objective lens, and the lens state detecting means moves the lens that moves the objective lens. The focus detection apparatus according to claim 1, wherein an amount characterizing the state or the moving state is detected. 13. The objective lens can focus on an object at a predetermined distance by moving a focus lens including all or a part of the objective lens. 2. The focus detecting device according to claim 1, wherein the lens state detecting means detects a moving state of the focus lens or an amount characterizing the moving state. 14. The objective lens has an aperture, and the diameter of the aperture is variable at the time of photographing or observation, and the lens state detecting means is configured to determine the diameter of the aperture of the objective lens or an amount characterizing the diameter of the aperture. 2. The focus detection device according to claim 1, wherein 15. A focus detection means for obtaining signals relating to a focus state of the objective lens for a plurality of regions on a predetermined focal plane of the objective lens, a lens state detection means for detecting each state of the objective lens, and the predetermined focus. A signal relating to correction at the time of focus detection of each area by a predetermined calculation procedure using two or more parameters set corresponding to each area of the surface and the parameters determined for each state of the objective lens. Correction value calculating means, focus calculating means for calculating the focus state of the objective lens based on the signal relating to the focus state and the signal relating to the correction, and driving for driving all or some of the lenses constituting the objective lens Means, and the drive means drives all or a part of the lenses constituting the objective lens based on the calculation result of the focus calculation means to thereby control the focus state of the objective lens. A focus adjustment device, wherein