JPH0727110B2 - 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 Tokkai Sho 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 the extension of the screws. I am trying to adjust it. But,
In this system, the sensor and the subsequent printed circuit board are integrated to adjust the tilt, which causes the entire focusing unit to swing, and an extra space must be provided inside the narrow camera. There is a problem of not becoming.

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] The object of the present invention is to improve pupils by adjusting only the mirror angle in the focusing unit in order to improve such conventional drawbacks, and as a result, it is advantageous for downsizing. Another object of the present invention is to provide a focus detection device that facilitates automatic assembly and adjustment.

[Summary of the Invention] The gist of the present invention for achieving the above-mentioned object is to dispose a field mask and a field lens in the vicinity of a planned image forming surface of a photographing lens, and a diaphragm and a secondary image forming optical system behind them. Then, in a focus detection device of a secondary image shift type having a line sensor, an optical path bending mirror is arranged at a position close to the field lens, and the aperture and the aperture which are the entrance pupil of the secondary image formation optical system. A focus detecting apparatus comprising an adjusting mechanism for changing an inclination angle of the optical path bending mirror for aligning an exit pupil of a photographing 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.

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 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 defocus amount is detected by obtaining the correlation between the positions of the two images. The secondary imaging lens 5 forms a secondary image with a parallax from the light fluxes passing through different regions of the exit pupil S of the taking lens 1 on the photoelectric blocking array 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 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, the focusing optical system of FIG.
As shown in the sectional view of the drawing, the field mask 2, the field lens 3, and the field mask 3 arranged near the planned image forming surface of the taking lens 1.
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 book 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. Further, a fixed stage 17 and a rotary stage 18 are arranged in front of the line sensor 6, and the unit main body 14 has a mounting screw 19
Is fixed to the front plate of the camera by the line sensor 6 is temporarily held by the fixed stage 17 by the pin 20 for holding the sensor, and the optical path bending mirror 13 is tilted with respect to the unit body 14 by the adjusting screw 21 with the flange. I am supposed to get it.

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 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: Screw three adjustment screws 21 into 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: The fixed stage 18 can be struck by 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. Adjustment is performed so that the field lenses 3 correctly project the openings 4a and 4b of the diaphragm 4 into the exit pupil S of the taking lens 1. As shown in detail in FIG.
The optical path bending mirror 13 is placed on the flange portion 21a of the adjustment screw 21 screwed in first, and the tilt angle of the mirror 13 is changed by feeding the adjustment screw 21. When the tilt of the mirror 13 is changed, the optical axis from the mirror 13 to the exit pupil S of the taking lens 1 tilts, so that the position of the image of the diaphragm 4 projected on the exit pupil S can be adjusted and fixed. Note that the mirror
The position of 13 should be as close to the field lens 3 as possible. The reason is that if the two are too far apart, the position of the opening of the field mask 2 changes in the plane perpendicular to the optical axis due to the inclination of the mirror 13, so that the field mask 2 and the line sensor 6 by the secondary imaging lens 5 are changed. The image formation relationship with and will be destroyed.

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 adjustment tool, and the following S8 and S9 are adjusted.

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, since 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 14c of the unit body 14, 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 18
The concave surface 18a around the is chucked by the three claws of a jig (not shown), and the rotary stage 18 is rotated about the X axis. In this case, the contact surfaces 17b, 18b of the fixed stage 17 and the rotary stage 18
Are parallel to each other and are inclined at a predetermined angle with respect to the optical axis. Further, since the fixed stage 17 and the rotary stage 18 are restricted in rotation by the sensor holding pin 20, by rotating only the rotary stage 18, the fixed stage 17 and the rotary stage 18 integrally rotate around the Y axis. Adjusted.

The principle is shown in FIG. 6 (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 N1 of the contact surface 18b Suppose the tilt angle is φ. At the initial 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 φ, 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,
Although 17c is shifted by dz in the Z'-axis direction, the fixed stage 17 and the rotary stage 18 actually have the sensor holding pin 20.
The shift amount dz is generated by the contact surface.
The center of the line sensor 6 is not displaced from the optical axis because it is canceled by the sliding in the Z'axis direction between 17b and 18b.

The relationship between the angles θ and θy ′ described above is expressed as shown in FIG. What should be noted here is that the normal line N1 generates a tilt angle θz ′ around the Z ′ axis in addition to the tilt angle θy ′ around the Y ′ axis, but the actual adjustment range is −θ _{1 to} θ ₁ . Since it is a very narrow range, the angle θz 'is almost negligible compared to the angle θy' within that range, and there is no practical problem.

[Effects of the Invention] As described above, the focus detection device according to the present invention can be adjusted by moving only the optical path bending mirror in the focusing unit without tilting the entire focusing unit. It is not necessary to take an extra space around the focusing unit, which is advantageous for downsizing the camera. Further, since it is not necessary to move the sensor section, there is no fear that an unnecessary force is applied to the sensor holding section as in the conventional case. In addition, since pupils can be projected in units of focusing units, 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 an exploded view of a specific configuration example of the focusing unit, FIG. 5 is an enlarged cross-sectional view of an essential part of the focusing unit, and FIG. 6 is a principle diagram of tilt adjustment of a line sensor. FIG. 7 is a graph showing the inclination of the line sensor quantitatively. 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 an optical path bending 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, and 21 is a Adjustment screw.

 ─────────────────────────────────────────────────── ─── 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 Plant (72) Inventor Takeshi Koyama 770 Shimonoge, Takatsu-ku, Kawasaki City, Kanagawa Canon Inc., Tamagawa Plant (56) Reference JP-A-58-150918 (JP, A) JP, U) Actual public Sho 59-16883 (JP, Y2)

Claims (2)

[Claims] 1. A field image mask and a field lens are arranged in the vicinity of a planned image forming surface of a photographing lens, and a diaphragm and a secondary image forming optical system are provided behind them, and a secondary image forming shift system having a line sensor is combined. In the focus detection device, an optical path bending mirror is arranged at a position close to the field lens, and in order to align the aperture, which is the entrance pupil of the secondary imaging optical system, with the exit pupil of the photographing lens, A focus detection apparatus comprising an adjusting mechanism for changing an inclination angle of an optical path bending mirror. 2. The focus detecting mechanism according to claim 1, wherein the adjusting mechanism is configured such that the optical path bending mirror is mounted on the flange by means of three adjusting screws with flanges.