JPH0731302B2 - Focus detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a secondary imaging lens shift type focusing device used in a single-lens reflex camera, etc. The present invention relates to a focus detection device provided with a rotation adjusting mechanism around an axis.

[Prior Art] Generally, in a focusing device of a secondary imaging shift type, a pair of secondary imaging lenses and a pair of line sensors corresponding thereto are used. If the alignment in the direction of rotation around the optical axis is insufficient,
There is a problem that distance measurement error occurs. For example, if the pair of line sensors 30a and 30b are inclined with respect to the projection images 31a and 31b by the secondary imaging lens of the field frame that regulates the distance measurement field as shown in FIG. , Since different parts of Sb are being measured, accurate distance measurement cannot be performed.

In order to correct the distance measurement error due to such a so-called "blur glare" phenomenon, conventionally, the entire line sensor was rotated to adjust the position of the image of the line sensor. Therefore, the adjustment by rotating the line sensor is extremely troublesome, and there is a drawback that a considerable space is required for the adjustment.

[Object of the Invention] In order to remedy the above-mentioned conventional drawbacks, an object of the present invention is to rotate only a small secondary imaging lens with a line sensor fixed, thereby facilitating the above-mentioned so-called "blur glare" phenomenon. It is to provide a focus detection device that can be eliminated.

[Summary of the Invention] The gist of the present invention for achieving the above-mentioned object is to re-image an object by an objective optical system on a pair of line sensors by a pair of secondary imaging lenses to form a secondary object image. In a focusing device of a secondary imaging shift type that detects a focusing state of the objective optical system from a relative shift, the pair of line sensors are held and the pair of secondary imaging lenses are attached to the objective optical system. A focus detection device comprising: a unit main body that is rotatably held around an optical axis; and a rotation adjustment mechanism that adjusts a rotation amount of the secondary imaging lens.

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

FIG. 1 shows a basic configuration diagram of an optical system according to the present invention,
Reference numeral 1 denotes a photographing lens, which has a field mask 2, a field lens 3, a diaphragm 4 having two openings 4a and 4b symmetrical with respect to the optical axis, and a secondary element 5a and 5b. An imaging lens 5 and a line sensor 6 consisting of two elements 6a, 6b are arranged.

Among them, the field mask 2 blocks an unnecessary light beam outside the distance measuring field from entering the focusing device system, and the field lens 3 connects the openings 4a and 4b of the diaphragm 4 and the exit pupil S of the photographing lens 1. By placing them in an image relationship, they play a role of effectively guiding the light flux that has passed through the taking lens 1 to the line sensor 6. The diaphragm 4 is for limiting the light flux, and the two elements 5a and 5b of the secondary imaging lens 5 reconnect the light flux passing through different areas of the exit pupil S of the photographing lens 1 onto the line sensor 6. It plays the role of making the image. Two elements 6a of the line sensor 6,
2 re-imaged by the secondary imaging lens 5 from the output of 6b
The amount of defocus is detected by calculating the correlation between the positions of the two images. The secondary imaging lens 5 forms a secondary image having a parallax from a light flux that has passed through different areas of the exit pupil S of the photographing lens 1.
It is formed on the array of photoelectric elements of the line sensor 6.

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 designed to be 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. On the reflection side of the sub-mirror 12, as shown in the sectional view of FIG. 3 when the focusing optical system of FIG. 2 is viewed from the lateral direction, a field mask arranged near the planned image forming surface of the taking lens 1. 2, a field 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. Submirror shown in FIGS. 2 and 3
All optical elements from 12 to the line sensor 6,
They are attached together in one unit body 14.
An infrared cut filter 15 and an antireflection member 12 are inserted between the sub mirror 12 and the field mask 2, and the antireflection member 16 prevents the reflected light filter 11 on the surface of the infrared cut filter 15 from reaching. It is for. The unit body 14 is fixed to the front plate of the camera by a mounting screw 17, the field lens 3 is adjusted by the field lens adjusting pin 18 with respect to the unit body 14, and the secondary imaging lens 5 is rotationally adjusted. Rotational adjustment is made with respect to the unit main body 14 by a screw 19 for use.

Next, the assembling procedure of this focusing unit is shown by arrow A in FIG.
It will be described according to the procedure of 1, 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 book 14.

A4: The cut filter 15 is incorporated into the unit book 14 by press-fitting the hole 16a of the antireflection member 16 into the dowel 14a of the unit book 14.

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

A6: Screw the rotation adjusting screw 19 into the screw hole 14d of the unit body 14.

A7: The diaphragm 4 is attached to the secondary imaging lens 5.

A8: Positioning part 5c of the secondary imaging lens 5 and rotation adjusting screw 1
The unit body 14 of the secondary imaging lens 5 can be
Position in the direction of rotation with respect to.

A9: The line sensor 6 is attached to the mounting holes 6c and 6d and the unit body 14
The pin 14e is fitted and positioned to be attached to the unit body 14.

Next, the adjustment procedure will be described according to the arrows S1 to S5 in the drawing (however, S2 is not shown). First, the whole unit is attached to the adjustment tool and the following adjustments of S1 to S3 are performed.

S1: 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 pin 18 is provided in the hole 3a and the cutout hole 3b of the field lens 3.
, The field lens 3 is decentered in parallel, and then fixed with an adhesive. In this case, the adjustment standard uses the tool mirror box and the tool exit pupil.

S2: Although not shown, the shading correction is performed by using the uniform luminance surface chart to collectively correct the uneven light amount on the line sensor 6 and the uneven sensitivity of the line sensor 6 by the EEPROM.

S3: The secondary imaging lens 5 is biased counterclockwise in FIG. 4 by a spring (not shown), and the positioning portion 5c is pressed against the rotation adjusting screw 19 to rotate the screw 19 to turn the secondary imaging lens 5 unit. Change the rotation angle with respect to the main body 14 to adjust the glare.

Since the adjustment as the focusing unit is completed by the above-described means, the focusing unit is removed from the adjustment tool, and then the following adjustments of S4 and S5 are performed.

S4: When the focusing unit is attached to the front plate of the camera, the parallax is adjusted by moving the entire focusing unit in the Y-axis direction in order to match the distance measuring center with the distance measuring center in the viewfinder. In this case, since the mounting portion on the bottom surface of the front plate of the camera is provided with a groove that fits into the mounting seat 14c of the unit book 14, the focusing unit is moved in parallel with this as a guide.

S5: After fixing the unit main body 14 to the front plate of the camera with the mounting screw 17, the focus of the focusing unit is electrically matched using the EEPROM.

FIG. 5 shows another example of the rotation adjusting mechanism of the secondary imaging lens 5, and the reference numerals are given according to FIG. In this case, the eccentric portion 21a of the eccentric pin 21 is inserted into the hole 20 of the unit body 14, and the head portion 21b of the eccentric pin 21 is fitted to the fork portion 22 of the secondary imaging lens 5. .

The fitting portion 23 of the secondary imaging lens 5 is the hole portion 14 of the unit main body 14.
Since it is fitted in b, if the eccentric pin 21 is rotated, the secondary imaging lens 5 can be rotated around the optical axis and the alignment with the line sensor 6 can be performed. In addition to this, the rotation adjusting mechanism of the secondary imaging lens 5 can be replaced with various mechanisms using, for example, a cam.

In each of the above embodiments, if the secondary imaging lens 5 is rotated to adjust the alignment of the line sensor 6 around the optical axis, the image projected on the line sensor 6 is as shown in FIG. Become. That is, the pair of line sensors 30a and 30b are used as the visual field frame.
Even if it is slightly inclined with respect to 31a and 31b, each line sensor 30
Since the distances a and 30b are measured at the same positions of the subject images Sa and Sb, the so-called ghost glare is removed.

Since the cause of the glare is not only the deviation of the angle of the line sensor 6 but also the eccentricity of the secondary imaging lens 5, the secondary imaging lens 5 is rotated rather than the line sensor 6. It is better to adjust it.

[Effects of the Invention] As described above, in the focus detection device according to the present invention, the rotational direction alignment around the optical axis between the pair of secondary imaging lenses and the pair of line sensors corresponding thereto is adjusted by a small secondary coupling. Since the image lens can be rotated for adjustment, the adjustment unit can be made smaller than before. Further, since it is not necessary to move the line sensor, unnecessary force is not applied to the flexible electric wire connected to the conventional line sensor, and the line sensor pulled by the electric wire can be securely fixed in advance. Because it is possible, adjustment work 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 layout diagram in a camera, and FIG. FIG. 4 is a cross-sectional view as seen from the direction, FIG. 4 is an exploded view of a specific configuration example of the focusing unit, FIG. 5 is a perspective view of another embodiment of the rotation adjusting mechanism of the secondary imaging lens, and FIG. FIG. 7 is an explanatory diagram of the state of the subject image projected on the sensor, and FIG. 7 is an explanatory diagram of the state of the subject image projected on the line sensor in the conventional case. 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 mounting screw, 18 is a field lens adjusting pin, 19 is a rotation adjusting screw, 20 is a hole, 21
Is an eccentric pin, 22 is a fork part, and 23 is a fitting part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akira Akashi, Akira Akashi, 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Canon Inc., Tamagawa Plant (72) Keishi Otaka 770, Shimonoge, Takatsu-ku, Kawasaki, Kanagawa Canon Inc. Company Tamagawa Business Office (72) Inventor Takeshi Koyama 770 Shimonoge, Takatsu-ku, Kawasaki City, Kanagawa Canon Inc. Tamagawa Business Office (56) Reference JP-A-58-150918 (JP, A) JP-A-60-263914 ( JP, A)

Claims (4)

[Claims] 1. An object image formed by an objective optical system is further re-imaged on a pair of licensors by a pair of secondary imaging lenses, and a focus state of the objective optical system is detected from a relative deviation of the secondary object image. In the focusing device of the secondary image-shifting method, a unit main body which holds the pair of line sensors and also holds the pair of secondary image-forming lenses rotatably around the optical axis of the objective optical system, A focus detection device comprising a rotation adjustment mechanism for adjusting the rotation amount of a secondary imaging lens. 2. The focus detection device according to claim 1, wherein the rotation adjusting mechanism rotates the secondary imaging lens with respect to the unit main body by rotation of a pin. 3. The focus detection device according to claim 2, wherein the secondary imaging lens is rotated by the protrusion amount of the pin. 4. The focus detection device according to claim 2, wherein the pin is an eccentric pin, and the secondary imaging lens is rotated by the eccentric pin and the amount of eccentricity.