JPH0516569Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a field mask placed in front of a condenser lens in a focus detection device for a camera.

Prior Art Two imaging optical systems are arranged behind the expected focal position of the taking lens, and the relative position of the image obtained by re-forming the image taken by the taking lens by the imaging optical system is detected, and the relative position of the image of the taking lens is detected. Focus detection devices have been proposed that are configured to detect focus conditions.

In this type of focus detection device, one is known in which a field mask is disposed at a predetermined position of a photographing lens, and a condenser lens is disposed at a rear position away from the field mask. If the field mask and the condenser lens are placed apart from each other, even when the condenser lens is integrally combined with the imaging lens and the line sensor, the field mask is constructed separately from them and the mirror box of the camera It is conceivable that it would be connected to the bottom wall of the

However, if the field mask is configured separately from other optical systems in the focus detection device, the field mask
After positioning and installing the optical system of the camera (taking lens, secondary mirror, etc.), the optical system of the focus detection device must be positioned and installed relative to both the camera's optical system and the field mask. . This position adjustment involves directing the optical axis of the optical system of the focus detection device to the center of the pupil of the photographing lens, adjusting the focusing of the re-imaging image, and aligning the optical axis with the field mask. It is difficult to adjust both the field mask, which is located relatively close to the lens, and the photographic lens, which is located far away, and the assembly work becomes complicated.

Furthermore, members for attaching the field mask and other optical systems to the camera, and members for blocking stray light entering between the field mask and the condenser lens are required, increasing the number of parts.

Purpose The purpose of the present invention is to provide an optical device for a focus detection device in which the assembly work of a field mask can be easily and accurately performed, and the number of parts can be reduced.

Summary In the optical device for a focus detection device of the present invention, the condenser lens and the field mask member are arranged behind the expected focal plane of the photographing lens, and the field mask member is integrated with the imaging lens, the condenser lens, and the line sensor. It is characterized by being configured to form a module.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the arrangement of the optical system, etc. when the focus detection device according to the present invention is applied to a single-lens reflex camera.

In FIG. 1, a photographing lens TL, a movable mirror 2, a focusing plate 4, a pentaprism 6, etc. are well-known elements constituting a single-lens reflex camera. However, if the camera is configured to perform automatic focus adjustment using the output of the focus detection device, the focus adjustment optical system of the photographing lens TL is driven by a lens drive device including a motor (not shown). It is configured as follows.

The center part of the movable mirror 2 is formed to be semi-transparent, and a sub mirror 8 is provided behind it. is guided to a focus detection device 10 located below.

The focus detection device 10 includes a visual field mask member 12, a condenser lens LC, a reflector 14, a mask plate 16,
It is equipped with imaging lenses L1 and L2 and a line sensor 18, and the output of the line sensor 18 is processed by a signal processing circuit (not shown) to generate a defocus signal indicating the amount and direction of focus deviation from the in-focus position. Ru. Based on this defocus signal, the focus adjustment state is displayed on a display device (not shown), and the focus adjustment lens of the photographing lens TL is driven to the in-focus position by a drive device (not shown).

FIG. 2 is a diagram showing the basic optical system of the focus detection device, where the dashed line Z indicates the optical axis of the photographing lens TL.
A dotted line F indicates the expected focal position of the photographing lens TL (a position equivalent to the film exposure surface). The field mask member 12 and the condenser lens LC are arranged at a position slightly (for example, about 4 mm) behind the planned focal position F. Imaging lenses L1 and L2 are arranged behind the condenser lens LC with the optical axis Z as an axis of symmetry, and a mask plate 16 having openings A1 and A2 is provided in front of these imaging lenses L1 and L2. ing. Each imaging lens L1, L2
A line sensor 18 consisting of a CCD is arranged on the image plane.

The condenser lens LC has the power to form images of the apertures A1 and A2 of the mask plate 18 on predetermined positions of the photographic lens TL, and the sizes of the apertures A1 and A2 are set to match the size of the subject light passing through the photographic lens. It is set so that only the subject light that passes through an aperture with a specific aperture value, for example, F5.6, is allowed to pass through. As a result, even if various photographic lenses are used, if the photographic lens has an open aperture value smaller than F5.6, the subject image received by the line sensor 18 will not be offset by the aperture of the photographic lens TL. There is no.

Images If, Io, and Ib on the optical axis indicate images in the front focus, in-focus, and back focus states, respectively, with respect to the subject in front of the photographic lens TL. The imaging lenses L1, L2 of these images If, Io and Ib
The re-imaging images by I1f, I1o, I
1b, and I2f, I2o, and I2b. That is, the re-imaging image I1o,I of the focused image Io
2o is connected to a position slightly in front of the line sensor 18, and the re-imaged images I1f and I2f of the front-focus image If are
The re-imaged images I1b, I2b of the rear-focused image Ib, which are focused in front of the focused re-imaged images I1o, I2o and closer to the optical axis Z, are the focused re-imaged images I1
o, I2o and at a position away from the optical axis Z. Here, the position of the image formed by the photographing lens TL is opposite to the distance between the two re-imaged images,
The line sensor 18 determines rear focus and front focus depending on whether the distance between the two re-imaged images is longer or shorter than the distance between the two re-imaged images at the time of focusing, and determines how much the difference in distance is. Thus, the amount of out-of-focus is detected. That is, the line sensor 18 has a large number of pixels arranged along the moving direction of the re-imaged image, and detects how many pixels apart the pattern of the re-imaged image is repeated. , detect the distance between both re-imaged images.

3 to 6 show an enlarged view of the focus detection device 10 configured as one module.

In the figure, the condenser lens LC has an aspherical convex lens surface 20 on the upper surface, a spherical convex lens surface 22 on the lower surface, and is formed around the convex lens surface 20,
It is constituted by a plastic lens formed of a flange surface 24 perpendicular to the optical axis direction and a side peripheral surface 26 perpendicular to the flange surface 24. The condenser lens attachment part 32 formed on the upper wall of the support body 30 has a circular aperture 34 forming an optical path, and an optical axis formed around the aperture 34 so as to be orthogonal to the optical axis direction and in contact with the flange surface 24. It includes a direction positioning surface 36 and an optical axis positioning surface 38 formed to be perpendicular to the positioning surface 36 and to fit into the side peripheral surface 26 .
Therefore, when the condenser lens LC is fitted into the lens attachment part 32, the flange surface 24 and side peripheral surface 26 of the condenser lens LC abut and fit into the positioning surfaces 34 and 36 of the lens attachment part 32, respectively. As a result, the position of the condenser lens LC in the optical axis direction and the alignment of the optical axis with respect to the support body 30 can be performed accurately and easily.

The visual field mask member 12 has a circular recess 12 on the lower surface.
a, and an upper wall 12c made of a light-shielding material that has a long rectangular opening AS in the direction parallel to the direction in which the line sensor 18 is disposed at the center of the circular recess 12a and is large enough to cover the entire condenser lens LC. ,
It has two legs 12d and 12e extending downward from the lower surface of the upper wall 12c. leg portion 12d,
Hook portions 12h and 12i each have abutting surfaces 12f and 12g that are inclined with respect to the horizontal plane at the tips of 12e.
is formed. This visual field mask member 12 is
While elastically deforming the legs 12d and 12e outward, the leg 12d is inserted into the rectangular attachment hole 31a of the support top wall 31, while the leg 12e is brought into contact with the side surface 31b of the support top wall 31. By bringing it into contact with
The hook portions 12h and 12i are the lower corner portions 3 of the support upper wall 31.
1c and 31d, and attached to the support body 30. In the attached state, the inclined abutment surfaces 12f, 12g are caused by the elastic force of the legs 12d, 12e to return inwardly, causing the support upper wall 31
As a result of elastic contact with the lower corners 31c and 31d of the field mask member 12, an elastic pulling force is generated downward on the upper wall 12c of the field mask member 12, and the chamfered portion 12j around the circular recess 12a of the upper wall 12c pulls the condenser lens LC from above. It's pressing. This makes the condenser lens
The LC is integrally fixed to the support body 30.

Note that the longitudinal position of the rectangular opening AS of the field mask plate 12 is such that 12o, 12p, 12g, and 12r are perpendicular to the longitudinal direction of the rectangular mounting hole 31a of the support upper wall 31 on the side end surfaces of the legs 12d and 12e. Inner wall surfaces 31b and 31l, and side surface 31b
It is determined by abutting against inner wall surfaces 31m and 31m perpendicular to .

The upper wall 12c of the field mask member 12 restricts the incident light to the condenser lens LC to only the light incident from the rectangular aperture AS to prevent the incidence of harmful stray light, and also prevents the incidence of harmful stray light. be regulated within a predetermined range. Note that the support upper wall 3
1 protrusions 31h and 31i are located on the upper wall 12 of the visual field mask.
Prevent stray light from entering from the side of c.

The reflecting mirror 14 is fixed to the support body 30 in an attitude inclined at 45 degrees with respect to the horizontal plane, and guides the light from the condenser lens LC toward the line sensor 18.
The infrared cut filter 40 is fixed to the support 30 in a vertical position at a position facing the reflecting mirror 14, and blocks infrared light harmful to focus detection.

The mask plate 16 is made of a light-shielding material and has two oval openings A1 and A2 formed in the center.
and mounting holes 16a, 16b formed at the ends, and the mounting holes 16a, 16b are fitted into the pins 30a, 30b of the support body 30, and the openings A1 and A
2 is fixed at a position overlapping the circular opening 30c of the support 30, and as mentioned above, the photographing lens
Only light from a predetermined aperture at the pupil position of the TL is transmitted. The imaging lens member 42 is made of a transparent material, and includes imaging lenses L1 and L2 formed so that a part of each other intersects in the center, and
It has attachment holes 42a and 42b, and the attachment holes 42a and 42b are fitted into the pins 30a and 30b of the support body 30, and the mask plate 16 is fixed to the support body 30 in an overlapping state. By this,
Imaging lenses L1 and L2 face openings A1 and A2 of mask plate 16, respectively.

The sensor unit 44 includes a base plate 48 that integrally supports the line sensor 18 made of a CCD, and a protective glass 52 fixed in front of the line sensor 18 via a spacer 50. It is sealed by a plate 48, a spacer 50, and a protective glass 52. The sensor unit 44 is fixed to the support 30 with the base plate 48 in contact with the front end surface 30d of the support 30.

In this way, the focus adjustment device 10 includes the field mask member 12, the condenser lens LC, the reflector 14, the mask plate 16, and the imaging lenses L1 and L.
2 and the line sensor 18 are positioned at a predetermined position with respect to the support 30 and are integrally coupled. Mounting holes 31e, 31f and 31g formed in the upper wall 31 of the support 30 are fixed to the bottom wall 54 of the mirror box.

In the configuration of this embodiment, since the rectangular aperture AS of the field mask member 12 is arranged behind the planned focal plane F of the photographing lens TL, the line sensor 18
Above, the image of the rectangular aperture AS is slightly blurred. However, the subject image captured by the photographing lens TL is captured by the condenser lens LC and the imaging lenses L1 and L2.
In addition, the blurring of the image of the rectangular aperture AS will affect the re-imaged image equally on the two re-imaged images. , are canceled out when detecting the relative position of the re-imaged image, and do not adversely affect focus detection.

FIGS. 7 and 8 show an embodiment in which the upper surface of the condenser lens is formed with a second flange surface and a side peripheral surface that engage with the field mask member, and the field mask member is positioned with respect to the condenser lens. An example is shown.

The condenser lens LC is attached to the lens mounting portion 32 of the support body 30 as in the embodiments shown in FIGS. 3 to 6.
The optical axis direction positioning surface 36 and the optical axis positioning surface 38 are provided with a flange surface 24 and a side circumferential surface 26 that abut or fit together, and a second lens perpendicular to the optical axis direction is provided around the convex lens 20 on the upper surface. Tsubamen 25 and
A second side circumferential surface 27 orthogonal to the second collar surface 25 is provided.

On the other hand, the field mask member 12 is shown in FIGS.
A light shielding part 12b similar to the embodiment shown in the figure, a rectangular opening AS,
The inner circumferential wall 12k of the circular recess 12a is provided with leg portions 12d, 12e and hook portions 12h, 12i.
is formed so that it fits into the side circumferential surface 27 of the condenser lens LC, and the lower surface 12l of the upper wall 12 abuts against the flange surface 25.

Further, the length of the longitudinal side of the rectangular mounting hole 31a of the upper support wall 31 is such that the inner wall surfaces 31k and 31l perpendicular to the longitudinal direction are longer than the side end surface 1 of the leg portion 12d.
It is formed so as to contact 2o and 12p without a gap, respectively. Thereby, the position of the visual field mask member 12 around the optical axis Z can be determined with high precision. In this embodiment, the engagement between the side surfaces 12m and 12n of the field mask member upper wall 12c and the protrusions 31h and 31i of the supporter upper wall 31 and the engagement between the leg portion 12e and the supporter upper wall 3 are as follows. It is formed to be loose.

Thereby, the visual field mask member 12 fixes the condenser lens LC to the support body 30, and
The lower surface 12l and the inner circumferential wall 12n fit into the flange surface 25 and side circumferential surface 27 of the condenser lens LC,
Positioning and optical axis alignment of the rectangular opening AS in the optical axis direction are performed with high accuracy, and the inner wall surfaces 31k and 31l of the support upper wall 31 are aligned with the side end surface 12 of the leg portion 12d.
The position around the optical axis can be accurately determined by contacting with o and 12p.

The field mask member does not include legs as described above,
It can also be configured to be screwed onto the support.

Effects: Because the field mask member is integrally coupled to a single module that includes the condenser lens imaging lens and the line sensor, the field mask member can be easily aligned with the module before being attached to the camera, and installation errors can be avoided. Can be made smaller.

Moreover, since the field mask member and the condenser lens are arranged behind the expected focus position of the photographing lens, these members do not obstruct the photographing optical path.

[Brief explanation of the drawing]

Figures 1 to 6 show an embodiment of the present invention, in which Figure 1 is a side sectional view of a single-lens reflex camera, Figure 2 is a layout of the basic optical system, and Figure 3 is a focus FIG. 4 is a plan view, FIG. 5 is a side sectional view, and FIG. 6 is an exploded perspective view of the detection device as seen from below. 7 and 8 show a modified embodiment, with FIG. 7 being an exploded perspective view and FIG. 8 being a side sectional view. LC: condenser lens, L1, L2: imaging lens, 18: line sensor, 12: visual field mask member.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. Two imaging lenses for re-forming an image formed by a photographing lens, a condenser lens disposed in front of the imaging lens, and a condenser lens arranged in front of the imaging lens. A line sensor for detecting the relative position of two images re-formed by the lens and a field mask member disposed in front of the condenser lens and regulating the field of view of the line sensor form an integrated module. A focus detection device for a camera, characterized in that the modules are coupled together and arranged so that the field mask member and the condenser lens are located behind a planned focal position of a photographing lens. 2. The focus detection device according to claim 1, wherein the field mask member is formed to also serve as a holding member for the condenser lens. 3. The field mask member is elastically deformable in the direction of the optical axis of the photographic lens, and has a leg portion that is elastically deformed outward and has a hook portion on the tip side, and a leg portion that is elastically deformable in the direction of the optical axis of the photographing lens, and has a leg portion that is elastically deformed outwardly and has a hook portion on the tip side, and a leg portion that is elastically deformable in the direction of the optical axis of the photographing lens, and a leg portion that is elastically deformed outwardly and has a hook portion on the tip side, and a leg portion that is elastically deformable in the direction of the optical axis of the photographing lens. The supporting body of the module has a contact surface that contacts the condenser lens in the optical axis direction, and elastic deformation of the visual field mask member in the optical axis direction to cause elastic contact with the hook portion of the visual field mask member. The hook portion is in contact with the hook portion, and by elastic contact between the hook portion and the hook portion, the pressing portion presses the condenser lens in the direction of contacting the contact surface, so that the condenser lens is integrally fixed to the support body. A focus detection device according to claim 2, characterized in that the focus detection device is configured as follows.