JPH03172827A - Camera - Google Patents

Abstract

PURPOSE:To miniaturize a camera in which a TTL system is adopted in a lens shutter type, to simplify a mechanism and to reduce the cost of the camera by bending a luminous flux passing through a photographing lens in the outside area of a photographing optical path at a position which is closer to an objective side than a shutter and guiding it to a focus detecting device. CONSTITUTION:An optical path bending means including a 1st mirror 3 and a 2nd mirror 4 is provided so that the luminous flux 7 passing through the photographing lens 1 in the outside area of the photographing optical path 8 is bent at the position which is closer to the objective side than the shutter 6 and bypasses the shutter 6 to be guided to the focus detecting device 2. The luminous flux passing between a broken line 7 and a continuous line 8 advances to the focus detecting device 2 as a luminous flux for range-finding but is not shielded by the shutter 6 because it advances in parallel with the shutter 6 after passing the 1st mirror 3. Therefore, autofocusing in a TTL system is always performed regardless of the action of the shutter 6. As to the action of the shutter 6, it is sufficient to execute an opening and closing action only for exposure and the camera is miniaturized and simplified like an ordinary compact camera.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a camera, and more particularly to a lens-shutter type camera equipped with a TTL focus detection device.

[Conventional technology]

Many examples of single-lens reflex cameras that are equipped with a focus detection device and perform autofocus are already known. - Focusing of an eye reflex camera has traditionally required high precision, and a so-called TTL type focus detection device has been adopted in which detection is performed using light that has passed through a photographic lens. On the other hand, there is a strong demand for smaller size and lower price for cameras that employ lens shutters, which are generally called compact cameras (for this reason, TTL focus detection devices are not used, and external light-type distance measuring devices are used). However, in recent years, there has been an increasing demand for high focusing accuracy even in compact cameras, and cameras that are lens shutter types but employ the TTL method have appeared.

[Problems to be Solved by the Invention] By the way, as mentioned above, since the TTL method is adopted even though it is a lens-shutter type, conventionally the reflector that guides the light for distance measurement to the focus detection device is located behind the shutter. It is installed in Therefore, the shutter is opened to perform focus detection even when not photographing, and therefore a separate light-shielding plate is required to block exposure of the film. In a conventional camera of this kind, the shutter is once closed when photographing, then the light shielding plate is opened, and the shutter is opened again to expose the photograph. Also, when the exposure is complete,
The extreme situation where the shutter is closed, the light blocking plate is closed, and then the shutter is opened again? A 111m movement is performed. In order to perform such complex operations, the mechanism itself has to become complex and large, which results in the loss of the original advantages of compact cameras, such as compactness and low cost, in conventional cameras of this type. Was. The present invention has been devised in view of the above-mentioned conventional technical problems and to effectively solve them. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a camera that can perform TTL autofocus without sacrificing the original advantages of a compact camera, such as being small and inexpensive due to a simplified mechanism. [Means for Solving the Problems] A camera according to the present invention has the following configuration in order to solve the above-mentioned conventional technical problems and achieve the object. That is, the camera according to the invention of claim 1 is a camera having a lens shutter, in which a light beam passing through the photographing lens in an area outside the photographing optical path is bent at a position closer to the object than the shutter, thereby bypassing the shutter. and an optical path bending means for guiding the light beam to the focus detection device. Further, in the camera according to the second aspect of the invention, the optical path bending means of the camera according to the first aspect is constituted by a total reflection mirror.

[Effect]

In the camera according to the invention of claim 1, the distance measuring light beam that has passed through the outer region of the photographing optical path when passing through the photographing lens is bent by the optical path bending means before passing through the shutter, that is, on the object side of the shutter. . As a result, the distance measuring light flux bypasses the shutter and is guided to the focus detection device. The amount of light obtained as a distance-measuring light beam increases compared to the case where a distance measuring light beam is used.

【Example】

A preferred embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 is a diagram showing the photographing optical system and focusing optical system of an embodiment of the camera according to the present invention, viewed from the vertical cross-sectional direction of the camera, and FIG. 2 is a diagram showing the photographing optical system and the focusing optical system of FIG. FIG. 3 is a diagram showing the focusing optical system viewed from the cross-sectional direction of the camera. Note that the focusing optical system here refers to an optical system that guides the distance measuring light beam to the focus detection device. In the figure, 1 is a photographic lens group of a photographic optical system, and 2 is a focus detection device. Reference numeral 3 denotes a first total reflection mirror disposed outside the photographing optical path, which guides the distance measuring light beam that has passed through the photographing lens group 1 to the focus detection device 2. Reference numeral 4 denotes a second total reflection mirror that forms a pair with the first mirror 3 and guides the distance measuring light beam to the focus detection device 2. Reference numeral 5 indicates a shutter base plate, and reference numeral 6 indicates a blade of a shutter that also serves as an aperture. The first mirror 3 is attached to the shutter base plate 5. The dashed line 7 in FIG. 2 is an axial light beam passing outside the photographing optical path, and in FIG. 1 viewed from the vertical cross-sectional direction of the camera, it is a light beam that appears overlapping the optical axis of the light beam passing through the photographing optical path. Also,
In FIG. 2, the photographing optical path 8 is shown by a solid line. That is, the light beam passing between the broken line 7 and the solid line 8 is guided to the focus detection device 2 as a light beam for distance measurement. The specifications of the photographic lens in this example are that the focal length is 35 mm and the F number is 4.
．． It is set to 0. (The light flux surrounded by solid line 8 has an F number of 4.0, and the light flux surrounded by broken line 7 and solid line 8 has an F number of 2.5.) Regarding the operation of the camera according to the present invention To give an overview, first, the amount by which the release button is pressed is divided into two stages, and when the release button is pressed one stage, the first stage switch is turned on. This first stage switch is a switch that starts photometry and focusing of the camera, and when it is turned on, preparation for photographing is automatically completed. Then, in this state, the operating state of the second stage switch is determined. The second stage switch is turned on by pressing the release button one more step, and the diaphragm/shutter mechanism opens and closes the blades 6 for proper exposure.After the exposure is complete, the film is wound and the next shot is taken. Prepare to be able to do so. The series of exposure operations is thus completed. FIG. 3 is a diagram showing the optical system of the focus detection device (AF element) 2 and the photographing optical system as viewed from above the camera. In FIG. 3, a second mirror 4 is located in front of the expected imaging plane (F) at a position equivalent to the film plane for the photographic lens 1.
is arranged with an inclination of 45 degrees, and this second mirror 4 has a rectangular opening 4 for defining a field of view for focus detection.
a is formed. A condenser lens L is located behind the planned image plane (F). is arranged, and further behind it, a pair of re-imaging lenses L, , L, are arranged symmetrically with respect to the optical axis (12) of the photographing lens 1'. These pair of re-imaging lenses L+, Lt re-image the image formed by the taking lens 1'' on its intended imaging plane (F).The condenser lens L0 and both re-imaging lenses L,... A third total reflection mirror MI is arranged with an inclination of 45° between L and L, and this third mirror Ml reflects the light rays made parallel to the optical axis (ρ) by the second mirror 4. , further bent by 90° to make it perpendicular to the optical axis (see Fig. 4).Each arrow shown in Fig. 3 (A), (B), and (C) is formed by a 1° photographing lens. The front focus image, the focused image, and the back focus image are shown, respectively, and the re-imaging lens L,...
L is the image corresponding to each of these front-focus image (A), in-focus image (B), and back-focus image (C): (Aυ, (A t),
(B I), (B l), (C, ), and (C*') are formed as a first image and a second image, respectively. Here, (A
), (B), and (C) are formed as images indicated by upward arrows in the figure, the corresponding first . The second image is formed as an image indicated by both downward arrows, and the first... Second
The interval between images changes depending on the focus adjustment state of the photographic lens l°. Therefore, with respect to the re-imaging lenses Ll and Lt, light-receiving element arrays are arranged at positions conjugate with their intended image-forming planes or in the vicinity thereof, and from the output of these light-receiving element arrays, the first
．． By detecting a change in the position (interval) of the second image, the focus adjustment state of the photographic lens 1' can be detected. Note that M,,M, is an aperture mask placed in front of the re-imaging lens L,,L,. The shaded area at 1° of the photographic lens indicates the area through which the light beam outside the photographic optical path passes, and the range-finding light beam passing through this portion passes through the first mirror 3 and heads toward the focus detection device 2. After passing through the first mirror 3, the light beam travels parallel to the shutter 6 as shown in FIG. 4, so that the light beam is not blocked by the shutter 6. By configuring the focusing optical system as described above, the distance measuring light beam is guided to the light receiving element array of the focus detection device without passing through the shutter 6, so the TTL method is always used regardless of the operation of the shutter 6. Autofocus can be performed using Therefore, the shutter 6 only needs to be opened and closed for exposure, and the mechanism for this can be made smaller and simpler than a conventional compact camera. In addition, each mirror that guides the distance measuring light beam to the focus detection device is a total reflection mirror, so that a sufficient amount of light for autofocus can be ensured.

【Effect of the invention】

As is clear from the above description, the present invention provides the following excellent effects. In other words, even if the TTL method is adopted even though it is a lens shutter type, the shutter operation when performing autofocus is unnecessary, and the mechanism for that is also unnecessary, making the camera itself smaller and the mechanism simpler. is achieved. In particular, when a total reflection mirror is used as the optical path bending means, a more sufficient amount of light can be obtained than other autofocus mechanisms that use a half mirror.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the photographing optical system and focusing optical system of an embodiment of the camera according to the present invention, viewed from the vertical cross-sectional direction of the camera, and FIG. 2 is a diagram showing the photographing optical system and the focusing optical system of FIG. FIG. 3 is a diagram showing the focusing optical system viewed from the cross-sectional direction of the camera. Figure 3 is a diagram showing the focusing optical system viewed from above the camera.
FIG. 4 is a perspective view showing the focusing optical system. 1... Shooting lens group, 1''... Shooting lens, 2...
-Focus detection device, 3...first mirror, 4...second mirror 5...shutter base plate, 6...shutter, 7...
・Light flux outside the photographing optical path, 8: Photographing optical path, Q: Optical axis of the photographing lens, F: Planned imaging plane, Lo: Condenser lens %1IIL2: Re-imaging lens, MI・
...Third mirror, M,,M. ... Aperture mask patent Applicant Minolta Camera Co., Ltd. Agent Patent attorney Seishi Ao (1 other person) Figure 1 Figure 2

Claims (2)

[Claims] (1) In a camera having a lens shutter (6), the light beam (7) passing through the photographing lens (1, 1') in the outer area of the photographing optical path (8) is directed to a position closer to the objective side than the shutter (6). optical path bending means (
3, 4). (2) The camera according to claim 1, wherein the optical path bending means (3, 4) are total reflection mirrors.