JP3215725B2 - Focus detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detecting device capable of detecting the in-focus state of a photographic lens with respect to a subject in a plurality of zones in a screen to be photographed.

[0002]

2. Description of the Related Art Such a focus detecting device is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 1-155308 and 2-58012. In these publications, a plurality of focus detection zones are provided on a predetermined focal plane, and a pair of partial images obtained by looking through the formed image through each zone is provided on a plurality of line sensors by a pair of separator lenses. A configuration for dividing and re-imaging is disclosed.

In order to reduce the influence of vignetting of the photographing lens, a peripheral detection zone on the predetermined focal plane is arranged in a sagittal direction perpendicular to the radial direction of the photographing lens. Is more desirable. On the other hand, if the sensors arranged on the re-imaging plane have the same arrangement direction, a single line sensor can be used by separating a part of each line sensor.

[0004] CC currently used as a line sensor
D sequentially obtains luminance information by sequentially transferring charges accumulated for each pixel. In a conventional focus detection device, three line sensors arranged at different positions are electrically connected,
The outputs of the three line sensors are extracted as a series of information. Such connection is employed because the cost is lower than providing a detection circuit for each line sensor.

[0005]

However, the conventional transfer method has a problem that it takes more time than extracting information from a single line sensor, and from this point, there is a demand for using a single line sensor. is there.

As described above, there are different requirements for the arrangement of the detection zone and the arrangement of the sensor. However, in the above-described conventional focus detection device, these arrangement relations are all set to be the same, and the degree of freedom is set. There is no problem.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and relates to the arrangement of a detection zone on a predetermined focal plane and the arrangement of a line sensor on a re-imaging plane. It is an object of the present invention to provide a focus detection device that can be freely combined, and to provide a device that can be reduced in size even when five or more detection zones are provided on a predetermined focal plane.

[0008]

In order to achieve the above object, a focus detecting device according to the present invention comprises a first deflecting section for deflecting a light beam from a central detection zone provided at the center on a predetermined focal plane. A second deflecting unit provided on each side to deflect a light beam from each of a plurality of peripheral detection zones provided on both sides of the central detection zone on a predetermined focal plane in directions different from the first deflecting unit; A third deflecting unit provided on each side to deflect the light beam deflected by the second deflecting unit in the same direction as the deflecting direction by the first deflecting unit, and is deflected by the first and third deflecting units. A sensor for receiving a light beam for each detection zone, and at least one of the second and third deflecting units on each side,
Light beams from a plurality of peripheral detection zones are deflected on the same surface.

[0009]

Embodiments of the present invention will be described below. The embodiment is a focus detection device that is used, for example, as a focus detection device of a single-lens reflex camera and detects the in-focus state of a photographic lens with respect to a plurality of subjects within a photographic range.

[0010]

First Embodiment FIGS. 1 to 5 show a first embodiment of a focus detection device according to the present invention. Note that the vertical relationship between FIG. 1 and FIG. 2 is opposite in terms of drawing.

As shown in FIGS. 1 and 2, a field mask 10 for extracting a part of a subject image is disposed near a predetermined focal plane where a subject image is formed by a photographing lens. , Detection zones 11, 12, 13, 14, 1 as five apertures that determine the field of view of the focus detection system
5 are formed.

The predetermined focal plane is a plane optically conjugate with the film plane in the case of a photographic camera and an image sensor in the case of an electronic camera. In a camera having an optical finder system, the predetermined focal plane is also optically conjugate with the focus plate.

The focus detection zone includes a central detection zone 11 provided at a position intersecting the optical axis of the photographing lens, and four peripheral detection zones 12, 13, 14, 15 provided on both sides in the longitudinal direction. The peripheral detection zones 12-15 are provided so that the longitudinal direction thereof coincides with the sagittal direction orthogonal to the longitudinal direction of the central detection zone.

As shown in FIGS. 1 and 2, the light flux transmitted through the central detection zone 11 through two horizontally divided areas E 1 and E 2 of the pupil E of the photographing lens is 90 The beam is deflected, divided via a pair of separator lenses 30 and 31 as a re-imaging optical system, and re-images on a central area 41 on a line sensor 40 a provided on a re-imaging plane 40. A pair of separator lenses 30, 3
Reference numeral 1 has a function of dividing an image formed in the detection zone 11 into two parts and re-forming the image. The pupil is optically conjugate with the pupil E of the photographing lens as a pupil of a focus detection system. is there.

Two vertically divided areas E on the pupil E
The light flux transmitted through the peripheral detection zones 12, 13, 14, 15 through 3, E4 is transmitted to the first mirror 20 by the second mirror 21.
Is reflected to the center side different from the reflection direction of
The light is reflected by the mirror 22 in the same direction as the first mirror 20, and re-images through the pair of separator lenses 32-39.

At this time, the peripheral detection zone 1 near the center
The light fluxes from the peripheral detection zones 14 and 15 are re-imaged on the same peripheral regions 42 and 43 on the line sensor 40a as the light fluxes from the central detection zone 11, and the light fluxes from the outer peripheral detection zones 14 and 15 are Are formed again on the peripheral areas 45 and 46 on the line sensor 40b provided in parallel with the image sensor 40b.

In this embodiment, the first, second, and third deflecting units use the first mirror 20, the second mirror 21, and the third mirror 22, but a prism or the like may be used in addition to the mirror. Is also possible.

Here, the x, y, and z axes are defined in FIG.
The xy plane is parallel to the field mask 10, and the yz plane is parallel to the re-imaging plane 40.

The third mirror 22 is positioned on the optical path of the light beam entering from the detection zones 12 and 14 in the yz plane.
Because it is provided in degrees, the interval between the light beams does not change when reflected by this mirror. Therefore, as shown in FIG. 5, the interval ΔY between the optical paths incident from the detection zones 12 and 14 is the interval ΔY between the optical paths after being reflected by the mirrors 21 and 22.
H, and this interval is equal to two line sensors 40
a, 40b.

Since a light beam reaching the sensor from the central detection zone and a light beam reaching the sensor from the peripheral detection zone have different optical path lengths, optical systems having different focal lengths are used.

The viewfinder system of the camera (not shown) is provided with a focusing area for the photographer to confirm the detection zone corresponding to the detection zone on the predetermined focal plane. The circuit uses the outputs of the line sensors 40a and 40b to determine the in-focus state of the photographic lens by using the output of an area corresponding to the subject intended by the photographer or the in-focus area overlapping the subject selected by the circuit on the camera side. To detect.

Each area 41, 42, 43, on the line sensor
At 45 and 46, an image is formed by the luminous flux from each detection zone. The focus detection device takes in the outputs of the line sensors 40a and 40b at a time and separately recognizes the output corresponding to each area. The video signals are detected as video signals corresponding to a pair of images, respectively, and the in-focus state of the photographing lens corresponding to each detection zone is detected by a known phase method.

By deflecting the optical path by the mirror, the central detection zone 11 and the peripheral detection zone 1 on the field mask 10 located at the predetermined focal plane as shown in FIG.
2, 13, 14, and 15 are arranged at right angles, and on the re-imaging plane 40, as shown in FIG. 4, an area 41 receiving an image from the central detection zone 11 and images from the peripheral detection zones 12, 13 are formed. The receiving areas 42 and 43 can be arranged on the linear line sensor 40a, and the two line sensors 40a and 40b can be arranged in parallel with each other.

Since the exit pupil of the taking lens is circular, by making the longitudinal direction of the peripheral detection zone coincide with the sagittal direction orthogonal to the central detection zone, vignetting due to vignetting can be suppressed. If the longitudinal direction is the same direction as the central detection zone, vignetting occurs due to vignetting in a portion where the image height is high, and there is a high possibility that accurate focus detection cannot be performed due to an insufficient amount of image light.

Further, by aligning the directions of the line sensors in one direction, the in-focus state in five zones can be detected by the two line sensors.

[0026]

FIG. 6-8 shows a focus detection apparatus according to a second embodiment of the present invention. In this example, two detection zones 11 and 16 are provided at the center of the screen, and the other configuration is the same as that of the first embodiment. The light flux from the detection zone 16 is reflected by a mirror (not shown),
The central region 44 of the line sensor 40b
Form an image on it.

The arrangement of the detection zones on the field mask 10 is shown in FIG. 7, and the arrangement of the line sensors on the re-imaging plane 40 is shown in FIG.

[0028]

Third Embodiment FIGS. 9-12 show a focus detection apparatus according to a third embodiment of the present invention. In this example, the luminous fluxes from the detection zones 12 and 14 provided on the periphery of the screen are reflected by the separate second mirror 21a and the second mirror 21b, respectively, are reflected again by the common third mirror 22, and are respectively reflected. Light enters the line sensor.

Other configurations are the same as those of the first embodiment shown in FIGS. Also, the arrangement of the detection zone on the field mask,
The arrangement of the line sensors on the re-imaging plane is almost the same as the example shown in FIGS.

In this embodiment, by dividing the second mirror into two, as shown in FIG. 10, the interval .DELTA.H of the light flux entering from the detection zones 12, 14 and traveling toward the line sensor is set on the field mask. Can be set to be smaller than the distance ΔY between the detection zones 12 and 14 in the above. Therefore, the distance between the line sensors 40a and 40b can be made smaller than in the first embodiment, and the area occupied by the sensors can be made smaller.

FIGS. 11 and 12 show specific examples when the mirrors 21 and 22 are provided. In the example of FIG. 11, a mirror is attached to each of the two slopes.
In the example, the mirror is coated directly on the slope.

[0032]

Fourth Embodiment FIG. 13 shows a focus detection apparatus according to a fourth embodiment of the present invention. In this example, the luminous fluxes from the detection zones 12 and 14 provided around the screen are both reflected by the same second mirror 21 and different third mirrors 22a, respectively.
And the third mirror 22b again reflects the light and enters each line sensor. Other configurations are the same as in the first embodiment.

[0033]

As described above, according to the present invention, it is possible to arrange the line sensors in an arrangement different from the arrangement of the plurality of focus detection zones provided on the predetermined focal plane, and By deflecting light beams from a plurality of detection zones by a common mirror, it is not necessary to provide a mirror for each detection zone, and the number of mirrors can be reduced and the apparatus can be downsized.

[Brief description of the drawings]

FIG. 1 is a perspective view of an optical system showing a focus detection device according to a first embodiment.

FIG. 2 is a perspective view showing a main part of FIG.

FIG. 3 is a plan view showing an arrangement of detection zones on a predetermined focal plane according to the first embodiment.

FIG. 4 is a plan view showing an arrangement of line sensors on a re-imaging plane according to the first embodiment.

FIG. 5 is an explanatory diagram of an optical path near a second mirror according to the first embodiment.

FIG. 6 is a perspective view of an optical system showing a main part of a focus detection device according to a second embodiment.

FIG. 7 is a plan view showing an arrangement of detection zones on a predetermined focal plane according to a second embodiment.

FIG. 8 is a plan view illustrating an arrangement of line sensors on a re-imaging plane according to a second embodiment.

FIG. 9 is a perspective view of an optical system showing a main part of a focus detection device according to a third embodiment.

FIG. 10 is an explanatory diagram of an optical path near a second mirror according to a third embodiment.

FIG. 11 is an explanatory diagram illustrating a specific example of a second mirror according to a third embodiment.

FIG. 12 is an explanatory diagram showing another specific example of the second mirror of the third embodiment.

FIG. 13 is a perspective view of an optical system showing a main part of a focus detection device according to a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Field mask 11 ... Central detection zone 12-15 ... Peripheral detection zone 20 ... 1st mirror 21 ... 2nd mirror 22 ... 3rd mirror 30-39 ... Separator lens 40a, 40b ... Line sensor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B ^7/ 28-7/34 G03B 13/36

Claims (6)

(57) [Claims] A first deflecting unit for deflecting a light beam from a central detection zone provided at the center on a predetermined focal plane; and a plurality of peripheral detection units provided on both sides of the central detection zone on the predetermined focal plane. A second deflecting unit provided on each side to deflect a light beam from the zone in a direction different from the first deflecting unit; and a light beam deflected by the second deflecting unit by the first deflecting unit. A third deflecting unit provided on each side to deflect in the same direction as the deflecting direction, and a sensor for receiving a light beam deflected by the first and third deflecting units for each detection zone, At least one of the second and third deflecting units on each side deflects light beams from a plurality of peripheral detection zones on the same surface. 2. The focus detecting device according to claim 1, wherein each of the deflecting units is a mirror. 3. The focus detecting device according to claim 2, wherein both the second and third deflecting units are single mirrors. 4. The apparatus according to claim 2, wherein the second deflecting unit is a plurality of mirrors provided for each peripheral detection zone, and the third deflecting unit is a single mirror. Focus detection device. 5. The second deflecting unit is a single mirror,
The focus detecting device according to claim 2, wherein the third deflecting unit is a plurality of mirrors provided for each peripheral detection zone. 6. A first mirror for reflecting a light beam from a central detection zone provided at the center on a predetermined focal plane, and a plurality of peripheral detection zones provided on both sides of the central detection zone on the predetermined focal plane. A second mirror provided on each side so as to reflect a light beam from the first mirror in a direction different from that of the first mirror; and a light beam reflected by the second mirror having the same direction as the reflection direction by the first mirror. A third mirror provided on each side so as to reflect light in a direction, and a sensor for receiving a light beam reflected by the first and third mirrors for each detection zone. A focus detection device, wherein at least one of the second and third mirrors is a single mirror that reflects light beams from a plurality of peripheral detection zones on the same surface.