JP2001311870A - Focus detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the constitution of an angle adjusting mechanism without making the area of a holding means for holding a focus detecting element larger. SOLUTION: In the focus detector where 1st and 2nd focus detection areas are respectively set at positions separate from the optical axis LX of a photographing lens in 1st and 2nd directions by as long as 1st and 2nd distances, and luminous flux from the 1st focus detection area is deflected to the optical axis LX side and guided to a 1st focus detecting element; the 2nd distance is set shorter than the 1st distance, and the luminous flux from the 2nd focus detection area is deflected to an optical axis side by a 2nd optical system 3T (3b) at a deflection angle smaller than a deflection angle by a 1st optical system or the luminous flux is not deflected at all but guided to 2nd focus detection elements 9Ta and 9Tb (9Ba and 9Bb). The holding means of the focus detector is constituted so that the angle can be adjusted around the axis in the 1st direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detection device provided in a camera or the like, and more particularly to a device for deflecting a light beam from a focus detection area to guide it to a focus detection element.

[0002]

2. Description of the Related Art A focus detection area extending in a horizontal direction of a screen is set at a center portion of a photographing screen, and a focus detection area (off-optical axis area) extending in a vertical direction of the screen is provided on left and right sides thereof.
There is known a focus detection device that sets the focus and detects the focus adjustment state of the photographing lens in these three areas (Japanese Patent Laid-Open No.
3-278012). In this focus detection device, 3
The luminous flux from the area is received by a pair of three sets of image sensor arrays (focus detection elements) provided on the same chip (holding means), respectively. This is deflected to the optical axis side using a field lens. As a result, a plurality of image sensor arrays can be centrally arranged in the vicinity of the optical axis, so that the area of a chip holding these can be reduced, and the camera can be downsized.
However, since the deflected light beam does not originally enter the light receiving surface of the focus detection element at an angle but at a right angle, if the condition that the image sensor array is tilted with respect to the optical axis overlaps with this, the sensor “ There is a problem that the focus detection accuracy is reduced due to the "glare phenomenon".

[0003] Japanese Patent Laid-Open No. 3-23 discloses a method for suppressing a decrease in the focus detection accuracy due to the "blurring phenomenon".
One disclosed in Japanese Patent No. 5906 is known. This is intended to improve the focus detection accuracy by providing a mechanism for adjusting the tilt of the chip holding the image sensor array, thereby reducing the degree of “blurring”.

[0004]

In each of the above two publications, the focus detection area outside the optical axis is set only on the left and right sides of the center area of the screen (the area on the optical axis). In addition to this, there is also a camera in which an off-axis area is set above and below the central area. In this case, if the above concept is followed, it is necessary to deflect the light flux from the upper and lower areas to the optical axis side, and naturally, there is a problem of the "jab glare phenomenon" of the image sensor corresponding to the upper and lower areas. In order to suppress this, in addition to the angle adjustment for the left and right sensors, it is necessary to have a configuration that allows angle adjustment for the upper and lower sensors,
The angle adjustment mechanism becomes large-scale, which leads to an increase in size and cost of the focus detection device and, consequently, a camera equipped with the same.

An object of the present invention is to provide a focus detecting device which can simplify the structure of an angle adjusting mechanism without increasing the area of a holding means for holding a focus detecting element.

[0006]

The present invention will be described with reference to the drawings showing an embodiment. The present invention relates to a first focus detection area which is separated from an optical axis LX of a taking lens LE by a first distance in a first direction. The first optical system 3L (3) deflects the light beam from L (R) toward the optical axis LX at a predetermined deflection angle θ and divides it into two.
R), 7 and a second optical system 3T (3B), which divides the light beam from the second focus detection area T (B) separated by a second distance from the optical axis LX of the photographing lens LE in the second direction by a second distance. 7 and a pair of first focus detection elements 9L for receiving the light beam split into two by the first optical system at an angle corresponding to the deflection angle θ.
a, 9Lb (9Ra, 9Rb), a pair of second focus detection elements 9Ta, 9Tb (9Ba, 9Bb) that respectively receive light beams split into two by the second optical system, and first and second focus detection elements And a holding unit 9 for holding the same on the same surface. Then, the second distance is made shorter than the first distance, and the light beam from the second focus detection area T (B) is deflected to the optical axis side at a deflection angle smaller than the deflection angle by the first optical system 3L (3R). Or the second optical system 3T (3B) is configured so as to be divided into two without any deflection, and the holding means 9 is angle-adjusted around the axis X in the first direction and fixed to the apparatus main body 5. The angle adjusting mechanism 5a is provided to solve the above problem. According to a second aspect of the present invention, the first direction is defined as a long side direction in the rectangular shooting screen P, and the second direction is defined as a short side direction in the shooting screen P.

In the section of the means for solving the above-mentioned problems, which explains the configuration of the present invention, the drawings of the embodiments are used to facilitate understanding of the present invention. However, the present invention is not limited to this.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a schematic configuration diagram of a camera (single-lens reflex camera) according to the present invention. The luminous flux from the subject is
The light passes through the photographing lens LE in the lens barrel LB and is guided into the camera body CB. A part of the light beam guided to the camera body CB passes through the semi-transparent main mirror 51, is reflected downward by the sub-mirror 52, and then enters the focus detection module 10. The CPU 56 drives the lens drive motor 57 based on the focus detection signal output from the focus detection module 10 to adjust the focus of the photographing lens LE. On the other hand, the light beam reflected by the main mirror 51 is observed by an eyepiece 55 via a pentaprism 54.

FIG. 1 is an exploded perspective view showing the structure of a focus detection module 10, and FIG. 2 is a view showing a focus detection area in a photographing screen. In the present embodiment, as shown in FIG. 2, there are six focus detection areas in a rectangular imaging screen P. A region CH extending laterally around the central optical axis LX,
The two regions CV extending in the vertical direction (the direction orthogonal to the region CH) around the optical axis LX are called on-optical-axis regions,
The other four regions are referred to as off-axis regions. That is, the off-axis region is a region L that is separated from the optical axis LX to the left (first direction: long side direction) and extends in the vertical direction, and a region L that is rightward from the optical axis LX (first direction: long side direction). A region R that extends in the vertical direction and is separated from the optical axis L, a region T that extends in the horizontal direction and separates from the optical axis LX upward (second direction: short side direction), and a region T that extends downward from the optical axis LX (second direction: There are four regions B, which are separated in the short side direction) and extend in the horizontal direction. As can be seen from the figure, the distance between the upper and lower off-axis regions T, B and the optical axis LX (second distance) is the distance between the left and right off-axis regions L, R and the optical axis LX (first distance). Distance). These focus detection areas are determined by the structure of the focus detection module 10 shown in FIG.

In FIG. 1, a focus detection module 10 performs focus detection by a well-known phase difference detection method, and includes a field mask 1, an infrared cut filter 2, a field lens 3, a stray light removing light-shielding mask 4, and a folding mirror. 6, the aperture mask 7, the separator lens 8 and the image sensor chip 9 are integrally held by the holder 5. The field mask 1 has an opening 1C corresponding to the optical axis regions CH and CV as shown in the drawing, and openings 1T, 1B, 1L, 1R corresponding to the off-axis regions T, B, L, R, respectively. The field lens 3 and the light shielding mask 4 are respectively
3C, 3T, 3B, 3L, 3R corresponding to the openings of
And openings 4C, 4T, 4B, 4L, and 4R.
The lenses 3C, 3T, 3B, 3L of the field lens 3,
The 3R guides the light beams incident from the openings 1T, 1B, 1L, 1R of the field mask 1 to the aperture mask 7. At that time, as described later, the light beam is deflected toward the optical axis LX depending on the incident position.

As shown in the enlarged view of FIG.
And a pair of openings 7CHa, 7CHb, 7 corresponding to six focus detection areas, respectively.
CVa, 7CVb, 7Ta, 7Tb, 7Ba, 7Bb,
7La, 7Lb, 7Ra, 7Rb and lens 8CH
a, 8CHb, 8CVa, 8CVb, 8Ta, 8Tb,
8Ba, 8Bb, 8La, 8Lb, 8Ra, and 8Rb. Similarly, the image sensor chip 9 has image sensor arrays 9CHa, 9CHa,
9CHb, 9CVa, 9CVb, 9Ta, 9Tb, 9B
a, 9Bb, 9La, 9Lb, 9Ra, 9Rb are held on the same plane. The aperture mask 7 divides each light beam into two by each pair of openings, and guides the light beam to the separator lens 8.

Here, the pair of left and right curved surfaces 5a provided on the holder 5 form an adhesive surface with the image sensor chip 9, and are formed as curved surfaces so that the X axis (the axis in the first direction) of the image sensor chip 9 is formed. Can be adjusted with the rotation center as the rotation center. The reason why such position adjustment is necessary will be described below.

FIGS. 4 and 5 show the focus detection module 10.
It is a figure showing the state of the light flux in the inside. For convenience, the infrared cut filter 2, the light-shielding mask 4 for removing stray light, and the folding mirror 6 are not shown, and the field mask 1, field lens 3, aperture mask 7, separator lens 8, and image sensor chip 9 are arranged in a straight line. did. The lenses 3C, 3T, 3B, 3L, 3 of the field lens 3
A pair of luminous fluxes that have passed through R and are divided into two by the aperture mask 7 are respectively converted into rCHa, rCHb: rCVa, rCV.
b: rTa, rTb: rBa, rBb: rLa, rL
b: It is represented by rRa and rRb.

FIG. 4 shows the light flux viewed from the opening 1T of the field mask 1 toward 1B. Openings 7La and 7Lb of aperture mask 7, lens 8L of separator lens 8
a and 8Lb and a pair of luminous fluxes r corresponding to the off-axis region L
La and rLb overlap each other in a direction orthogonal to the paper surface. Similarly, the openings 7Ra and 7R of the aperture mask 7
b, the pair of light beams rRa and rRb corresponding to the lenses 8Ra and 8Rb of the separator lens 8 and the off-axis region R also overlap in a direction orthogonal to the paper surface. The luminous flux from the off-optical-axis regions L and R is applied to the lens 3 of the field lens 3.
Since the light beam passes outside the optical axes of L and 3R, the divided light beam rLa
And rLb and the light fluxes rRa and rRb are deflected to the optical axis LX side at a deflection angle θ, respectively, and the image sensor arrays 9La, 9Lb, 9Ra, 9R are angled according to the deflection angle θ.
b enters the light receiving surface obliquely.

As described above, since the light beams from the off-axis regions L and R are deflected to the optical axis LX, the regions L and R are
Image sensor array 9L even if it is relatively far from X
Since a, 9Lb, 9Ra, and 9Rb can be arranged close to the optical axis LX, the size of the image sensor chip 9 can be reduced. However, as described above, the luminous fluxes rLa, rLb, rRa, rR
b is inevitably incident on the sensor arrays 9La and 9Lb.
If 9Lb is also inclined with respect to the light beam in the rotation direction about the X-axis in FIG. 1, the deterioration of the focus detection accuracy due to the "blurring phenomenon" becomes so large that it cannot be ignored. Therefore, in the present embodiment, it is possible to adjust the tilt of the sensor chip 9, that is, the sensor arrays 9La and 9Lb around the X axis, and to minimize the deterioration of the focus detection accuracy due to the "bubble phenomena".

The tilt adjustment is performed at the stage of manufacturing the camera. Specifically, the sensor chip 9 is attached to the curved surface 5 a of the holder 5.
Then, the chip 9 is rotated by a small angle around the X axis while monitoring the focus detection state, and the chip 9 is adhered at an angle at which the influence of the "bubble phenomenon" is minimized.

On the other hand, FIG. 5 shows the light flux viewed from the opening 1L of the field mask 1 toward 1R. The apertures 7Ta and 7Tb of the aperture mask 7, the lenses 8Ta and 8Tb of the separator lens 8, and the pair of light fluxes rTa and rTb corresponding to the off-axis region T overlap each other in a direction orthogonal to the paper surface. Similarly, a pair of light beams rBa and rBb corresponding to the openings 7Ba and 7Bb of the aperture mask 7, the lenses 8Ba and 8Bb of the separator lens 8, and the off-axis region B.
Also overlap in the direction perpendicular to the plane of the paper. in this case,
Since the light beams from the off-axis regions T and B pass substantially near the center of the optical axis of the lenses 3T and 3B constituting the field lens 3, the light beams rTa and rTb and rBa and rBb are hardly deflected inward. Image sensor array 9Ta,
The light enters the light receiving surfaces of 9Tb, 9Ba, and 9Bb at substantially right angles.

The reason that the light beams rTa, rTb, rBa, and rBb are hardly deflected is that the vertical off-axis regions T, B
Are set closer to the optical axis LX than the left and right optical axis regions L and R, so that the image sensor arrays 9Ta, 9Tb, 9Ba and 9Bb are arranged near the optical axis LX without deflecting the light flux. This is because it is possible to increase the chip area. Since the vertical direction is the short side direction in the rectangular shooting screen, the vertical off-axis regions T and B are closer to the optical axis LX than the left and right (longer side) off-axis regions L and R. Even if it is set at a close position, there is no problem in arrangement.

Thus, the luminous fluxes rTa, rTb, rBa,
rBb is hardly deflected and the sensor arrays 9Ta, 9T
b, 9Ba, and 9Bb are incident on the light receiving surfaces at substantially right angles, so that the sensor arrays 9Ta, 9Tb, 9Ba, and 9Bb are slightly rotated with respect to the light beam in the rotational direction around the Y axis (the axis in the second direction) of FIG. Even if it is tilted, the deterioration of the focus detection accuracy due to the “blurring phenomenon” is small. Therefore, in the present embodiment, a mechanism for adjusting the inclination of the sensor chip 9 around the Y axis is not provided, and positioning is completed only by bringing both ends of the sensor chip 9 into contact with both curved surfaces 5a of the holder 5. Therefore, the configuration is simpler than when the sensor chip 9 is configured to be adjustable in both the X-axis and Y-axis directions, and the size and cost of the camera can be reduced.

In the above embodiment, the optical axis off-axis regions L,
R is the first focus detection area, off-axis areas T and B are the second focus detection area, lenses 3L and 3R of field lens 3 and aperture mask 7 are the first optical system, lens 3T of field lens 3 , 3B and the aperture mask 7 form the second optical system, and the image sensor arrays 9La, 9Lb, 9Ra,
9Rb is the first focus detection element, and the image sensor array 9
Ta, 9Tb, 9Ba, 9Bb are the second focus detection elements,
The sensor chip 9 is a holding unit, the holder 5 is a device main body,
The curved surfaces 5a constitute angle adjustment mechanisms.

In the above description, the first direction is the long side direction of the photographing screen, and the second direction is the short side direction of the photographing screen. However, the present invention is not limited to this. Further, the configuration of the angle adjusting mechanism is not limited to the embodiment.

[0022]

According to the present invention, the first and second focus detection areas are set at positions separated from the optical axis of the taking lens by first and second distances in the first and second directions, respectively. In a configuration in which a light beam from the focal length is deflected toward the optical axis and guided to the first focus detection element, the second distance is shorter than the first distance, and the light beam from the second focus detection area is smaller. Since it is configured to be deflected to the optical axis side at the deflection angle or to be guided to the second focus detection element without being deflected at all, the holding means of the focus detection element is used in order to prevent the deterioration of the focus detection accuracy due to the "blurring phenomenon". It is not necessary to adjust the angle around the axes in the first and second directions, and it is sufficient to be able to adjust the angle only around the axis in the first direction. Therefore,
The configuration of the angle adjusting mechanism can be simplified, and an increase in the size and cost of the focus detection device can be suppressed to a minimum.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a configuration of a focus detection device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an arrangement of a focus detection area.

FIG. 3 is a schematic diagram showing a configuration of a camera provided with the focus detection device.

FIG. 4 is a diagram showing a state of a light beam in the focus detection device.

FIG. 5 is a diagram illustrating a state of a light beam in the focus detection device when viewed from a direction different from FIG. 4;

FIG. 6 is an enlarged view of a part of FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Field mask 3 Field lens 3C, 3T, 3B, 3L, 3R lens 5 Holder 5a Curved surface 7 Aperture mask 8 Separator lens 9 Image sensor chip 9CHa, 9CHb, 9CVa, 9CVb, 9Ta, 9
Tb, 9Ba, 9Bb, 9La, 9Lb, 9Ra, 9R
b Image sensor array 10 Focus detection module CB Camera body CV, CH, L, R, T, B Focus detection area LB Shooting lens barrel LE Shooting lens LX Optical axis

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masamitsu Ozawa 3-2-2, Marunouchi, Chiyoda-ku, Tokyo Nikon Corporation (72) Inventor Hideki Kambayashi 3-2-2, Marunouchi, Chiyoda-ku, Tokyo F term in Nikon Corporation (reference) 2H011 AA01 BA23 BB01 BB02 2H051 BA04 BA18 CA04 CA06 CA09 CA10 CA12 CA16 CB06 CB08 CB10 CB20 DA07

Claims (2)

[Claims] 1. A first light source for deflecting a light beam from a first focus detection area separated by a first distance in a first direction from an optical axis of a photographing lens toward the optical axis at a predetermined deflection angle to divide it into two. An optical system, a second optical system that divides a light beam from a second focus detection area separated by a second distance from the optical axis of the photographing lens in a second direction, and a second optical system that is divided into two by the first optical system A pair of first focus detection elements for receiving light beams at an angle corresponding to the deflection angle, a pair of second focus detection elements for receiving light beams divided into two by the second optical system, respectively, And a holding means for holding the second focus detection element on the same plane, wherein the second distance is shorter than the first distance, and the second distance is shorter than the first distance.
May deflect the light beam from the second focus detection area toward the optical axis at a deflection angle smaller than the deflection angle of the first optical system, or may divide the light beam into two without any deflection. A focus detection device comprising: an angle adjustment mechanism configured to adjust an angle of the holding means around the axis in the first direction and to fix the angle to the apparatus main body. 2. The focus detection according to claim 1, wherein the first direction is a long side direction in a rectangular shooting screen, and the second direction is a short side direction in the shooting screen. apparatus.