JPS60263914A - Focus detecting device of camera - Google Patents

Abstract

PURPOSE:To reduce the trouble of adjustement by adjusting the holder for a focus detection optical system by the 1st adjusting mechanism in two orthogonal directions, and correcting the mismatching of the optical system with the holder and the storage body for a photoelectric converting element by the 2nd adjusting mechanism. CONSTITUTION:Part of subject light which is image-formed through a photographic lens is guided onto the photoelectric converting element of a sensor package 31 through the sensor unit 27 consisting of a field lens 37, an image separating prism 39, secondary image forming lenses 30a, 30b, and 30c, etc., and the image state of a subject image formed by the photographic lens is detected on the basis of the output signal of the photoelectric converting element to detect the foucs; and the holding part 29 for the sensor unit 27 is pivoted rotatably on an adjusting ground plate 45 at the shaft part 29a of one terminal, and the other shaft part 29b is held rotatably on an adjusting arm 46 and adjustable in two independent different directions. Further, an inclination adjusting plate 44 is provided between the unit holding part 29 and sensor package 31 rotatably as the 2nd adjusting mechanism.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a focus detection device used in a -eye reflex camera or the like.

In a camera focus detection device, the subject light entering through the photographic lens is guided onto a photoelectric conversion element by a focus detection optical system, and the imaging state of the subject is detected based on the output signal of this photoelectric conversion element. , an adjustment mechanism is an essential condition for correctly forming an image on the photoelectric conversion element surface, but this adjustment is performed with great care in minute displacements, and two-dimensional adjustments interfere with each other. Therefore, many steps were required to reach the final adjustment point.

An object of the present invention is to enable independent two-dimensional adjustment of the holder of the focus detection optical system, and to easily adjust the irregularity of the secondary imaging lens system. The main purpose of the device is to guide a part of the object light that is imaged by a photographing lens onto a photoelectric conversion element using a focus detection optical system, and to take a photograph based on the output signal of the photoelectric conversion element. A focus detection device that detects an image state of a subject image of a lens, comprising: a first adjustment mechanism that rotatably adjusts a holder of the focus detection optical system in two orthogonal directions, and the holder and the photoelectric conversion element. A second adjustment mechanism for correcting optical/system misalignment with the housing body.

Next, the present invention will be explained in detail based on illustrated embodiments.

FIG. 1 is a sectional view of the camera body, showing a state in which the main mirror is lowered. The camera body is composed of a bottom cover 2 surrounding a base 1 made of Guicast, for example, a back cover 3, an upper cover 4, a front cover 5, and a lens mount 6 to which a photographic lens is attached. A main mirror 8 is provided in the mirror box at the center for selectively guiding the light beam that has passed through the photographic lens to the finder optical system above and the photographic film surface 7. It has become a department.

The finder optical system includes a focusing plate 9, a pentaprism 10, and eyepiece lenses lla and ll sequentially along the optical path.
b is provided. Also, a light receiving element 12 for measuring subject brightness for exposure and a matte surface 9 of a focusing plate 9 are provided.
A Fresnel lens 13 is fixed to the upper part of the eyepiece frame 14 for condensing the light diffused by the light receiving element 12 on the light receiving element 12, and a prism 15 is attached to adjust the peak of distance measurement sensitivity to the center of the photographic screen. It is attached to the exit surface of the pentaprism 1o, facing the Fresnel lens 13.

Further, a pressure bonding plate 16 for holding the photographic film at the focal plane, a shutter curtain 17 of a focal plane shutter, and an aperture frame 18 are arranged inwardly from the back cover 3.

The main mirror 8 at the center of the mirror box is attached to a main mirror holding frame 19, and the holding frame 19 has an opening 19a in the center for guiding the light beam that has passed through a portion of the half mirror to the sub-mirror 2o. ing. Holding frame 19
is rotatably supported by a rotating shaft 21, and is urged to rotate in the direction of arrow A by a spring (not shown); It is regulated within a predetermined range by a stopper 22. A rubber plate 19b is added to the position of the holding frame 19 that comes into contact with the stopper 22 for absorbing shocks during lifting and lowering. In addition, on the back of the main mirror holding frame 19,
A sub-mirror 20 is arranged to guide the light flux that has passed through a portion of the half mirror to the focus detection optical system, and is set so that the incident angle θ of the light beam passing through the optical axis of the photographic lens is greater than 45 degrees. This sub-mirror 20 is fixed to a sub-mirror holding frame 23, rotatably supported on the main mirror holding frame 19 by a rotating shaft 24, and is urged to rotate in the direction of arrow B by a spring (not shown). . The stopper 25 regulates the upper stop position of the sub-mirror holding frame 23, and controls the rotation axis 2 of the sub-mirror holding frame 23.
A cam portion 23a is provided at the end portion on the 4 side, and the cam portion 23a is configured to move along the outer circumference of the guide pin 26 as the main mirror 8 rises.

A sensor unit 27 serving as a secondary imaging optical system for focus detection is arranged below the main mirror 8 via a first mask 28 for ghost prevention.
8 is an opening 28 having a central axis along the optical path.
It is said to be a. The sensor unit 27 includes a vertical knit holding section 29, a secondary imaging lens 30, a sensor package 31, etc., and the sensor package 31 having a CCD line sensor is attached to the lower surface of the unit holding section 29. Further, below the sensor unit 27, there is provided an operating lever 32 that interlocks with the automatic aperture lever on the photographing lens side, and a base plate 33 that holds this lever. It is pivoted. In addition, 35
is an LED for displaying the focus state, and the pentaprism 10
The bottom surface of the image is investigated.

FIG. 2 shows a cross section of the sensor unit 27 and its adjustment mechanism.
, field lens 37, reflection mirror 38, image separation prism 39, aperture 40, secondary imaging lenses 30a, 30b,
30c and a second reflecting mirror 41 are arranged. Note that the image separation prism 39 and the secondary imaging lenses 30a, 30
b and 30c are molded. A second mask 42 is provided in front of the field lens 37, and
It is located on the image plane. A third mask 43 and a tilt adjustment plate 44 are installed between the unit holding part 29 and the sensor package 31 to prevent stray light. Shaft portions 29a coaxially integrally formed on both ends of the unit holding portion 29
, 2'9b, one shaft portion 29a is rotatably supported by an adjustment base plate 45, and the other end shaft portion 29b is rotatably held by an adjustment arm 46.

Further, the sensor unit 27 is pressed downward by a coil spring 47. By adjusting the positional relationship between the rotation adjustment plate 48 attached to the unit holding part 29 and the adjustment base plate 45, it is possible to adjust the optical path within the sensor unit 27 using the shaft parts 29a and 29b. .

In the mechanism shown in FIGS. 1 and 2, when the main mirror 8 is in the lowered state in FIG. It is divided into those who are guided and those who are guided. The light beam that passes through a portion of the half mirror located at the center of the main mirror 8 is reflected by the submirror 20 and enters a focus detection optical system disposed at the bottom of the mirror box. The focus detection optical system is unitized as a sensor unit 27 as shown in FIG.
Cytofilter 36 → second mask 42 → field lens 37 → first reflection mirror 38 → image separation prism 39 →
Aperture 40 → secondary imaging lenses 30a, 30b, 30c + second reflection mirror 41 → third mask 43 → tilt adjustment plate 4
4→sensor package 31, and the phase difference between the images on the two rows of CCD line sensors of the sensor package 31 is detected to detect the focusing state of the photographic lens.

Note that in order to prevent the incident angle of the light ray passing through the optical axis of the photographic lens to the sub-mirror 20 to be larger than 45 degrees and to prevent the light reflected from the surface of the field lens 37 from entering the photographic film. The first one for ghost prevention.
Since the mask 28 is attached, it becomes possible to arrange the opening of the focus and detection optical system near the aperture frame 18 at the bottom of the mirror box, and effective arrangement of the focus detection optical system is achieved.

When the main mirror holding frame 19 rises against the bias in the direction A shown in FIG. 1 in conjunction with a shirt release (not shown), the guide bin 26 and the cam portion 23a of the sub-mirror holding frame 23 come into contact and slide. However, as the main mirror holding frame 19 further rises, the sub mirror holding frame 23 moves to B in FIG.
rotate in the opposite direction. When the main mirror holding frame 19 has finished rising, the submirror holding frame 23 is in a folded state, and the photographing light beam is transferred to the shutter curtain 17 without being cut off.
reach this. At this time, the sub-mirror holding frame 23 closes the opening 19a of the main mirror holding frame 19 to prevent light from entering the mirror box from the finder optical system.

FIG. 3 is an explanatory diagram of the operation of this automatic focusing optical system, but it differs from the actual arrangement. A secondary imaging system diaphragm 40 is provided at the back of the image separation prism 39, and two rectangular openings 40a and 40b are opened at positions narrowing the optical axis. On the exit pupil 49 of the photographing lens, there is an aperture 40a when the aperture 40 is projected by the field lens 37,
There are images 50a and 50b of 40b. Also, aperture 40
A misaligned image 50a when there is a misalignment in the position of the lens, or there is eccentricity or inclination of the optical axis of the photographing lens and the optical axis of the focus detection optical system.
', 50b' are shown displaced. Aperture opening 40
The light flux that has passed through a forms a secondary image on the CCD line sensor 51a, and the light flux that has passed through the other aperture aperture 40b forms a secondary image on the CCD line sensor 51b. The in-focus state is detected by detecting the phase difference between the voice power signals of the CCD line sensors 51a and 51b.

The light beams incident on the diaphragm openings 40a and 40'o become images 5 of the respective diaphragm openings on the exit pupil 49 of the photographing lens.
0a, 50b or 50a', 50b', so when it protrudes from the exit pupil 49 like the shifted image 50a'', the illuminance on the corresponding CCD line sensors 51a, 51b decreases. Therefore, the projection position of the entrance pupil of the secondary imaging optical system onto the exit pupil 49 of the photographing lens must be accurate, and the machining accuracy of the component parts must be accurate. Since there is a limit to this, an adjustment mechanism is an essential condition.Specifically, an adjustment mechanism that allows the sensor unit 27 to rotate around the Y-axis and Z-axis shown in Figure 3, that is, the first adjustment mechanism, is required. It is necessary.Also,
If the secondary imaging lenses 30a, 30b, 30c are eccentric, or if the COD line sensors 51a, 51b are not accurately positioned with respect to the sensor package 31, the focus will shift at both ends of the field of view. In order to correct this, it is necessary to
Rotating the CCD line sensors 51a and 51b around the axis,
That is, it is sufficient to use the second adjustment mechanism, the principle of which is shown in FIG.

FIG. 4 is a conceptual diagram of the secondary imaging optical system shown in FIG. 3 after the aperture. C
The light beam incident on one end of the CD line sensor 51 is
52b, and the light beams incident on the other end are shown as 53a and 53b. When the secondary imaging lens 30 is decentered, the light rays 52a and 52b are better than the light rays 53a and 52b as shown in the figure.
There is a possibility that the intersection occurs after 53b. In this case, if the CCD line sensor 51 is placed at the position shown by the solid line, the focus will shift at both ends of the field of view, making accurate distance measurement impossible. In order to correct this, by rotating the CCD line sensor 51 to the position shown by the broken line, the light rays 52a,
52b, 53a, and 53b both intersect on the sensor 51, and the focus movement is eliminated.

FIG. 5 is an exploded perspective view showing the adjustment mechanism of the sensor unit 27. The sensor package 31 containing the CCD line sensors 50a and 50b, the tilt adjustment plate 44, and the third mask 43 are fixed to the unit holding part 29 by a sensor fixing spring member 54. At this time, the claw portions 54c, 54d, 54e, and 54f of the sensor fixing spring member 54 engage with the recesses 29c, 29d, 29e, and 29f of the unit holding portion 29, thereby ensuring secure fixation. The inclination adjustment plate 44 has a cross-sectional shape with non-parallel surfaces shown in FIG. 6, and a tooth profile is machined on the outer periphery. This makes it possible to perform rotational adjustment around the Y'' axis as shown in FIG. Since the interval is 1/4 or less compared to the sensor length, the effect on focus detection accuracy is negligible. Further, the third mask 43 has an opening 43a through which the effective light flux passes and enters the sensor. As shown in FIG. 2, the third mask 43 covers the entire lower surface of the unit holding portion 29, and is configured to prevent stray light from entering the operating lever opening 1a shown in FIG. 1.

The rotation adjusting plate 48 inserted into the shaft portion 29a of the unit holding portion 29 is inserted into the caulking holes 48g and 48h of the unit holding portion 29.
After passing through the caulking dowels 29g and 29h, it is fixed to the unit holding portion 29 by hot caulking. The rotation adjustment plate 48 is made of a metal plate having spring properties, and is provided with a locking loose hole 48b and an insertion hole 48a for the shaft portion 29a. The bearing portion 45a of the adjustment base plate 45 is connected to the rotation adjustment plate 4.
The shaft 29a of the unit holding part 29 inserted through the insertion hole 48a of the adjustment arm 46 is rotatably fitted, and the hole 46b at the rear of the adjustment arm 46 is rotatable with the shaft 29b of the unit holding part 29. and the holes 4 on both sides of the adjustment arm 46.
6c and 46d are fitted to the tabs 45c and 45d of the adjustment base plate 45, thereby being coupled to the sensor unit 27.

After the coil spring 47 is bonded to the upper part of the unit holding part 29, the sensor unit 27 is pressed downward by being coupled to the camera base 1 through the screw holes 45g, 45f, and 45h of the adjustment base plate 45.

The posture adjustment of the sensor unit 27, that is, the first adjustment is the rotation around the Y axis shown in FIG. 3, that is, the rotation around the shaft parts 29a and 29b of the unit holding part 29 in FIG.
This is necessary in two directions: rotation around the axis, that is, rotation around the holes 46c and 46d of the adjustment arm 46 in FIG. The rotation adjustment around the Y axis is performed by rotating the rotation adjustment plate 48, and after the adjustment is completed, the lock screw hole 45 of the adjustment base plate 45 is
1. The screw 55 is inserted into the locking loose hole 48b of the rotation adjustment plate 48 and fixed.

Rotation adjustment around the Z axis is performed using the inclined elongated hole 46e of the adjustment arm 46.
This is done by inserting a tool into the elongated hole 45e of the adjustment base plate 45 and moving it in the direction of the elongated hole. After the adjustment is completed, screws 56 are inserted into the long locking holes 46j of the adjusting arm 46 and the locking screw holes 45j of the adjusting base plate 45 to fix them.

Note that since the coil spring 47 is in a charged state and the sensor unit 27 is always pressed downward, the shaft portion 29
No rattling occurs in a. In addition, the rotation adjustment plate 48
Since the metal plate is made of a resilient metal plate, the rotation adjustment around the Y axis and the rotation adjustment around the Z axis can be performed independently from each other without interference.

As explained above, in the camera focus detection device according to the present invention, the first adjustment mechanism quickly and easily adjusts the holder of the focus detection optical system on two mutually independent axes, and the second adjustment mechanism adjusts the holder on two mutually independent axes. This can be easily and reliably implemented even when dealing with irregularities in the subsequent imaging lens system.

[Brief explanation of the drawing]

The drawings show an embodiment of the camera focus detection device according to the present invention, in which Fig. 1 is a sectional view of the camera body with the main mirror in a lowered state, Fig. 2 is a sectional view of the sensor unit, and Fig. 3 is the focus detection mechanism. 4 is a principle diagram of sensor tilt adjustment, FIG. 5 is an exploded perspective view of the sensor unit adjustment mechanism, and FIG. 6 is a sectional view of the tilt adjustment plate. Code 8. 20 is a main mirror, 20 is a submirror, 27 is a sensor unit, 29 is a unit holding part, 31 is a sensor package, 43 is a third mask, 44 is a tilt adjustment plate, 4
5 is an adjustment base plate, 46 is an adjustment arm, and 48 is a rotation adjustment plate. Patent Applicant: Canon Co., Ltd. Continued from page 1 0 Inventor: Ishizaki 77 Hata, Shimonoge, Takatsu-ku, Meiyouzaki City, Canon Co., Ltd. Tamagawa Office

Claims (1)

[Claims] 1. A part of the object light formed by the photographic lens is guided onto a photoelectric conversion element by a focus detection optical system, and the image state of the subject image of the photographic lens is determined based on the output signal of the photoelectric conversion element. A focus detection device for detecting a focus detection optical system, comprising: a first adjustment mechanism that rotatably adjusts a holder of the focus detection optical system in two orthogonal directions; a housing for the holder and the photoelectric variable detection element; a second adjustment mechanism for correcting irregularities in an optical system. 2. The focus detection device for a camera according to claim 1, wherein the first adjustment mechanism is adjusted individually for two orthogonal axes and is configured not to interfere with each other. 3. The camera according to claim 1, wherein the second adjustment mechanism is a rotatable adjustment plate made of non-parallel surfaces provided between the holder and the housing for the photoelectric conversion element. Focus detection device.