JPH0473130B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a focus detection device suitable for self-timer photography.

In a focus detection device equipped with an optical system that projects a light beam of visible light or infrared light from a light-emitting element and detects focus by receiving reflected light from the subject with a light-receiving element, the intensity of the light beam is generally guaranteed. It is squeezed into a circular shape to

Therefore, since the light beam is narrowed down and the distance measurement area is narrow, during self-timer shooting where the camera operator is the only subject, it is extremely difficult for the operator to be reliably located within the distance measurement area, and it is extremely difficult to ensure that the operator is positioned within the desired distance measurement area. In some cases, focus detection was not performed.

Therefore, the purpose of the present invention is to improve the accuracy of distance measurement even when the intensity of the light beam becomes weak, since self-timer photography, in which only the camera operator is the subject, is not often used at a very long distance. Focusing on not having a negative effect on the camera, during self-timer shooting, a cylindrical lens, etc. is inserted on the optical axis of the light emitting element to flatten the circular light beam, expand the photometry area, and accurately detect focus. The present invention provides a focus detection device suitable for self-timer photography.

Embodiments of the present invention will be described below based on the drawings.

In Figure 1, 1 is a light emitting diode that emits infrared light, 2 is a condensing lens, 3 is an imaging lens, and 4 is a light emitting diode that emits infrared light.
is a photoelectric element as a light-receiving element, and the above configuration is an optical system in which a light beam from a light-emitting element is projected from a light-emitting element in a conventional focus detection device, and the light-receiving element receives reflected light from an object to perform focus detection. In this conventional device, the infrared light beam from the light emitting diode 1 is focused into a circular shape as shown by the two-dot chain line.

In contrast, in the present invention, during self-timer photography, the condenser lens 2 is placed on the optical axis of the optical system.
At the rear and in front of the imaging lens 3, the first beam spreads out flatly in the direction of 45 degrees with respect to the position where the camera is held horizontally.
The cylindrical lenses 5 and 6 of FIG. Therefore, the light beam passing through the cylindrical lens 5 is spread flat as shown by the solid line,
It has an elliptical shape, and the intensity per unit area is weaker, but the irradiation angle is wider and the distance measurement area is wider.
In addition, the reflected light from the flattened object is
It is returned to a circular shape via the cylindrical lens 6.

Figure 2 shows a plurality of photoelectric elements 4 as light receiving elements (divided into 4a, 4b, 4c, 4d, 4e).
This figure shows an optical system in a focus detection device arranged in such a way that, during self-timer photography, a cylindrical lens 5 is inserted in front of the condensing lens 2, but a cylindrical lens is not inserted in front of the imaging lens 4. Instead, the photoelectric elements 4, 4a, 4
b, 4c, 4d, and 4e are arranged at an angle corresponding to the spreading direction in which the light beam is flattened.

Note that when the base line length 7 of the light emitting element and the light receiving element is placed horizontally, the direction in which the light beam is flattened and spread is perpendicular to the base line length has little meaning; It needs to have a slope. In a camera, even if the base line length of the light emitting element and the light receiving element are placed horizontally or vertically, it is not possible to determine whether the camera is held in the normal horizontal position or vertically, so the light beam is flattened. It is preferable that the direction in which the fibers are spread out is set at 45 degrees with respect to the base line length. Further, when the base line length is set at 45°, the direction in which the light beam is flattened and spread is preferably on the base line length.

Further, the intervention of the cylindrical lenses 5 and 6 onto the optical axis of the light emitting element and the light receiving element is performed in conjunction with the operation of the setting member for self-timer photography.

Furthermore, even in self-timer shooting, if the target for focus detection is clear for someone other than the operator, there is no need to spread the light beam of the light emitting element flatly, so the above-mentioned interlocking mechanism of the setting member and cylindrical lens is not necessary. It is preferable to be able to switch between an interlocking state and a non-interlocking state depending on the situation.

Although the light emitting element has been described using as an example a light emitting element that emits infrared light, it goes without saying that a light emitting element that emits visible light may also be used.

As described above, according to the focus detection device of the present invention,
During self-timer photography, the light beam for focus detection can be spread out from its normally converged circular state into a flattened shape, so that the distance measurement area is expanded and accurate focus detection is performed. Also, since the light beam is spread flat in a 45° direction, you can either hold the camera horizontally or
The expanded distance measurement area allows you to capture your subject regardless of whether you hold it vertically.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory diagrams showing embodiments of the present invention, respectively. 1... Light emitting diode, 2... Condensing lens, 3
...Imaging lens, 4...Photoelectric element, 5, 6...Cylindrical lens.

Claims (1)

[Scope of Claims] 1. A light source that emits a distance-measuring light beam toward a subject; a first lens that transforms into a circular light beam to project the light beam of the light source; and a lens that is placed on the optical path of the light source during self-timer photography A first cylindrical lens that transforms the light beam into an oval shape that is flattened at 45 degrees with respect to the horizontal position of the camera, and a second cylindrical lens that focuses reflected light from the subject. a second cylindrical lens that is placed on the optical path of the reflected light only during self-timer photography and that transforms the oval reflected light into a circular shape; and a light receiving element that receives the reflected light that has passed through the second lens. A focus detection device comprising an optical system comprising: