JP2510085B2 - Focus detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a secondary image shift type focusing device used in a single-lens reflex camera or the like, and an optical axis of a focusing unit and an optical axis of a camera side. The present invention relates to a focus detection device provided with an adjusting mechanism for adjusting, that is, a pupil exiting mechanism.

[Prior Art] Conventionally, in this type of focusing device, it is general to adjust the inclination of the entire focusing unit to perform pupil exit.
For example, in the apparatus disclosed in Japanese Patent Laid-Open No. 60-39612, the focusing unit is attached to the front plate of the camera by using three screws and springs, and the posture of the focusing unit, that is, the inclination, is tilted by extending the screws. I am trying to adjust it. However, in this system, the sensor and the subsequent printed circuit board are integrated to adjust the tilt, which causes the entire focusing unit to oscillate, so that extra space is provided inside the narrow camera. There is a problem that has to be.

Moreover, since this adjustment is performed after the camera is attached to the front plate of the camera, the assembly process and the adjustment process are mixed, which is disadvantageous for rationalization of the production line. Further, the work of attaching the focusing unit with screws or springs has a problem that automatic assembly becomes difficult.

[Object of the Invention] An object of the present invention is to improve such drawbacks of the related art and to perform pupil defocusing by adjusting the parallel decentering of only the field lens, which is advantageous for downsizing and is capable of automatic assembly and automatic adjustment. It is to provide a focus detection device that can be easily performed.

[Summary of the Invention] The gist of the present invention for achieving the above-mentioned object is to provide a secondary image-shifting type focus detection device having a field lens in the secondary image-forming optical system, wherein Focus detection characterized by including a parallel eccentricity adjusting mechanism capable of moving the field lens in a plane orthogonal to the optical axis of the aperture lens, which is the entrance pupil of the lens, and the exit pupil of the photographing lens. It is a device.

Embodiments of the Invention The present invention will be described in detail based on the illustrated embodiments.

FIG. 1 is a basic configuration diagram of an optical system according to the present invention, in which 1 is a photographing lens, and a field mask 2, a field lens 3 and two apertures symmetrical with respect to the optical axis are sequentially provided along the optical axis thereof. A stop 4 having parts 4a, 4b, a secondary imaging lens 5 consisting of two elements 5a, 5b, and a line sensor 6 consisting of two elements 6a, 6b are arranged.

The field mask 2 in this block prevents unnecessary light beams outside the distance measuring field from entering the focusing device system, and the field lens 3
By placing the openings 4a and 4b of the diaphragm 4 and the exit pupil S of the photographing lens 1 in an image-forming relationship, the light flux passing through the photographing lens 1 is effectively guided to the line sensor 6. Aperture 4
Is for limiting the luminous flux, and the secondary imaging lens 5
The two elements 5a and 5b play a role of re-imaging the light beams passing through different regions of the exit pupil S of the photographing lens 1 on the line sensor 6. Two elements 6 of the line sensor 6
From the outputs of a and 6b, the correlation between the positions of the two images re-imaged by the secondary imaging lens 5 is obtained, and the defocus amount is detected. The secondary imaging lens 5 is an exit pupil S of the taking lens 1.
A secondary image having a parallax is formed on the array of photoelectric elements of the line sensor 6 from the light fluxes passing through different areas.

FIG. 2 is a cross-sectional view when the focus detection system according to the present invention is applied to a single-lens reflex camera, in which a quick return mirror 7 is arranged behind the taking lens 1, and the light flux reflected upward here is a condenser. It is guided to a finder system including a lens 8, a penta roof prism 9, and an eyepiece lens 10. A photosensitive film 11 is arranged behind the quick return mirror 7 and constitutes a photographing system together with the photographing lens 1. A sub-mirror 12 is attached to the back of the light transmitting portion of the quick return mirror 7 so that the sub mirror 12 is flipped up or returned together with the quick return mirror 7. This submirror 12
As shown in the sectional view of FIG. 3 which is a lateral view of the focusing optical system of FIG. A lens 3, a mirror 13 for bending the optical path, a diaphragm 4 having two openings 4a and 4b symmetrical with respect to the optical axis, a secondary imaging lens 5, and a line sensor 6 are sequentially arranged.

FIG. 4 is an exploded view showing a specific structural example of the focusing unit. All the optical members from the sub mirror 12 to the line sensor 6 shown in FIGS. 2 and 3 are collectively attached to one unit main body 14. An infrared cut filter 15 and an antireflection member 16 are inserted between the sub mirror 12 and the field mask 2, and the antireflection member 16 prevents reflected light on the surface of the infrared cut filter 15 from reaching the film 11. It is for doing. A fixed stage 17 and a rotary stage 18 are arranged in front of the line sensor 6, and the unit body 14 is fixed to a front plate of the camera by a mounting screw 19.
Is temporarily held on the fixed stage 17 by the sensor holding pin 20, and the field lens 3 is a field lens adjusting pin.
The unit main body 14 can be adjusted by 21a and 21b.

Next, the assembling procedure of this focusing unit will be described with arrows in FIG.
It will be described according to the procedure of A1, A2, A3 ....

A1: The infrared cut filter 15 is attached to the antireflection member 16.

A2: Attach the field mask 2 to the infrared cut filter 15.

A3: Place the field lens 3 on the unit body 14.

A4: The hole 16a of the antireflection member 16 is made into the dowel 14a of the unit main body 14.
The cut filter 15 is pressed into the unit body
Install in 14.

A5: Attach the mirror 13 to the unit body 14.

A6: The diaphragm 4 is attached to the secondary imaging lens 5.

A7: The positioning portion 5c of the secondary imaging lens 5 is attached to the unit body 14
The secondary imaging lens 5 is assembled into the unit main body 14 while being positioned in the rotational direction.

A8: The fixed stage 17 is attached to the line sensor 6.

A9: Attach the rotary stage 18 to the unit body 14.

A10: The fixed stage 17 sandwiches the rotary stage 18,
The fixed stage 17 is incorporated in the unit body 14, and the protrusion 17a of the fixed stage 17 is temporarily held by the engaging portion 14b of the unit body 14.

Next, the adjustment procedure will be described according to the arrows S1 to S9 in the drawing (however, S3 is not shown). First, the unit body 14 is attached to the adjustment tool, and adjustment is performed by the following procedure.

S1: The sensor holding pin 20 is inserted into the hole 6c and the cutout hole 6d of the line sensor 6 to insert the line sensor 6 into the unit main body 14.
Regulate the position of.

S2: The pupil is projected, that is, the focusing unit is aligned with the optical axis of the front plate of the camera body. The apertures 4a and 4b of the diaphragm 4 are adjusted by the field lens 3 so that they are correctly projected into the exit pupil S of the taking lens 1. Actually, the field lens adjusting pins 21a and 21b are the through holes of the unit main body 14, respectively.
After passing through the inside of 14c and the outside of the side wall 14d, it is inserted into the hole 3a and the cutout hole 3b of the field lens 3, and the field lens 3 is decentered in parallel in the YZ plane and then fixed with an adhesive. In this case, the adjustment standard uses the tool mirror box and the tool exit pupil.

S3: Although not shown, the shading correction is performed by using the uniform luminance surface chart, and the uneven light amount on the line sensor 6 and the uneven sensitivity of the line sensor 6 are collectively corrected by the EEPROM.

S4: The rotary stage 18 is chucked and rotated about the X ′ axis, and the line sensor 6 and the fixed stage 17 are integrally swung about the Y ′ axis to adjust the inclination of the line sensor 6. The adjustment method and principle will be described later with reference to FIG. After this adjustment, the fixed stage 17 and the rotary stage 18 are bonded and fixed.

S5: Pull out the sensor holding pin 20.

S6: While keeping the chucking of the rotary stage 18, the rotary stage 18 is translated in the Y′-Z ′ plane, and the line sensor 6 is positioned by aligning the optical axis with the center of the line sensor 6.

S7: The rotary stage 18 is rotated to adjust the rotation of the line sensor 6 around the X'axis, and the line sensor 6 is adjusted in the Z'axis direction to adjust the glare.

Since the adjustment as the focusing unit is completed by the above steps S1 to S7, the focusing unit is removed from the adjusting tool, and the following adjustments in S8 and S9 are performed.

S8: When the focusing unit is attached to the front plate of the camera, the entire focusing unit is moved in the Y-axis direction to adjust the parallax so that the distance measuring center coincides with the distance measuring frame center in the viewfinder. In this case, the mounting portion on the bottom surface of the front plate of the camera is provided with a groove for fitting with the mounting seat 14e of the unit main body 14, and the focusing unit is moved in parallel with this as a guide.

S9: After fixing the unit main body 14 to the front plate of the camera with the mounting screw 19, the focus of the focusing unit is electrically matched using the EEPROM.

The inclination adjustment of the line sensor 6 in the above-mentioned step S4 and its principle will be described in detail below. In FIG. 4, the rotary stage
The concave portion 18a around 18 is chucked with three claws of a jig (not shown), and the rotary stage 18 is rotated around the X'axis. In this case, the contact surfaces 17b, 1b of the fixed stage 17 and the rotary stage 18
8b are parallel to each other and are inclined at a predetermined angle with respect to the optical axis. Further, since the rotation of the fixed stage 17 and the rotary stage 18 is restricted by the sensor holding pin 20, by rotating only the rotary stage 18, the fixed stage 17 and the rotary stage 18 are integrated around the Y ′ axis. Rotation is adjusted.

The principle is shown in FIG. 5 (a). Since the contact surfaces 17b, 18b of the fixed stage 17 and the rotary stage 18 are inclined with respect to the optical axis as described above, the normal line N1 of the contact surface 18b.
The inclination angle of is assumed to be φ. At the intended position of the fixed stage 17, the normal line N1 is in the X'-Y 'plane. Here, when only the rotary stage 18 is rotated counterclockwise by the angle θ, the rotary stage 18 begins to tilt with respect to the optical axis as shown in FIG. It is represented by an inclination angle θy ′ from the optical axis of the normal line N2 at. Since the fixed stage 17 is shown so as to swing around the point C where the optical axis intersects the contact surfaces 17b and 18b, the surface 17c is shifted by dz in the Z'-axis direction. Actually, since the fixed stage 17 and the rotary stage 18 are regulated by the sensor holding pin 20, the generation of the shift amount dz is canceled by the slip between the contact surfaces 17b and 18b in the Z'-axis direction, and the line sensor 6 The center of does not deviate from the optical axis.

The relationship between the angle θ and the inclination angle θy ′ described above is expressed as shown in FIG. Note that the normal N1 is Y '
In addition to the tilt angle around the axis θy ′, the tilt angle around the Z ′ axis θ
z 'is generated, but because the actual adjustment range is extremely narrow range between - [theta] ₁ through? _1, the tilt angle θz Within that range'
Is almost negligible as compared with the inclination angle θy ′, and there is no practical problem.

Although the above-described embodiment shows the structure in which the decentering of the field lens 3 is adjusted by the adjusting jig, the structure may be such that the adjusting jig may not be used. FIG. 7 shows an example thereof. In this case, a guide pin 24 standing on the unit main body 14 of FIG. 4 is fitted into a guide groove 23 provided in the lens frame of the field lens 3 to Eccentric screws 27 and 28 having an eccentric amount e are fitted in two-direction guide grooves 25 and 26 provided in the frame. Now, when the eccentric screw 27 is turned in FIG. 7, the field lens 3 makes a substantially rotational movement in the direction of arrow E about the guide pin 24, so that the center of the field lens 3 makes a substantially linear movement in the Y-axis direction. When the eccentric screw 28 is turned, the field lens 3 moves in parallel in the direction of arrow D. Therefore, by adjusting the rotation of the eccentric screws 27, 28, the Y
-Parallel eccentricity can be independently performed in the Y-axis direction and the Z-axis direction in the Z plane, and in this method, parallel eccentricity adjustment of the field lens 3 can be performed without using a special adjustment jig. Is possible.

[Advantages of the Invention] As described above, the focus detection apparatus according to the present invention can be adjusted by finally moving only the field lens without inclining the entire focusing unit, and thus the focusing can be performed as in the conventional example. It is not necessary to take an extra space around the unit, which is advantageous for downsizing the camera. Further, since it is not necessary to move the sensor unit, there is no fear that an unnecessary force is applied to the lead wire connected to the sensor as in the conventional case. Furthermore,
Since the pupil can be projected by the focusing unit alone and the unit can be guaranteed, the assembly procedure in the mass production process is organized and automatic assembly becomes easy.

[Brief description of drawings]

The drawings show an embodiment of a focus detection device according to the present invention. FIG. 1 is a basic configuration diagram of an optical system, FIG. 2 is a sectional view of the inside of a camera, and FIG. FIG. 4 is a cross-sectional view seen from the direction, FIG. 4 is an exploded view of a specific configuration example of the focusing unit, FIG. 5 is a principle diagram of tilt adjustment of the line sensor, and FIG. 6 quantitatively represents the tilt of the line sensor. FIG. 7 is a configuration diagram of another embodiment of the field lens decentering adjustment mechanism. Reference numeral 1 is a photographing lens, 2 is a field mask, 3 is a field lens, 4 is a diaphragm, 5 is a secondary imaging lens, 6 is a line sensor, 7 is a quick return mirror, 12 is a sub-mirror,
13 is a mirror, 14 is a unit body, 15 is an infrared cut filter, 16 is an antireflection member, 17 is a fixed stage, 18 is a rotary stage, 19 is a mounting screw, 20 is a sensor holding pin, 21
a and 21b are field lens adjusting pins, 23, 25 and 26 are guide grooves, 24 is a guide pin, and 27 and 28 are eccentric screws.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akira Ishizaki, 770 Shimonoge, Takano-ku, Kawasaki City, Tamagawa Plant, Canon Inc. (72) Akira Akashi, 770, Shimonoge, Takatsu-ku, Kawasaki City, Canon Company, Tamagawa (72) Inventor Keishi Otaka, 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Canon Inc., Tamagawa Plant (72) Inventor Takeshi Koyama, 770, Shimonoge, Takatsu-ku, Kawasaki-shi, Tamagawa Plant, Canon Inc. (56) Reference JP 60-39612 ( JP, A) JP 59-148016 (JP, A)

Claims (2)

(57) [Claims] 1. In a focus detection device of a secondary imaging shift type having a field lens in the secondary imaging optical system, positions of an aperture stop which is an entrance pupil of the secondary imaging optical system and an exit pupil of a photographing lens. A focus detection apparatus comprising a parallel eccentricity adjusting mechanism capable of moving the field lens in a plane orthogonal to an optical axis of the field lens for performing alignment. 2. The focus detecting apparatus according to claim 1, wherein the adjusting mechanism is capable of adjusting the eccentricity of the field lens independently in two directions by rotating two eccentric pins.