JPS59226328A - Conversion lens provided with light leading-in device for exposure photometry - Google Patents

Abstract

PURPOSE:To make incident regular light to a light receiving part of a camera by providing a conversion lens in a position shielding the light receiving part for exposure photometry of the camera. CONSTITUTION:A conversion lens 2 set to a camera 1 is shown in the figure Though a camera light receiving part 3 acquires the light parallel with an optical axis 5 of a camera lens to measure the light essentially, it is shielded by the conversion lens 2, and therefore, Galilean or reverse Galilean optical systems 8 and 9 are provided additionally on the outside of focal lenses 6 and 7 for photographing. If these additionally provided optical systems are Galilean as shown in the figure optical systems 8 and 9 are so combined that their rear focuses coincide with each other. It is desirable that refracting faces of additionally provided optical systems are surfaces of revolution using optical axes of afocal lenses for photographing as axes.

Description

DETAILED DESCRIPTION OF THE INVENTION In general, the exposure metering light receiving section of a portable camera is often installed close to the photographing lens. If you attach a conversion lens with a large outer diameter to the camera, this will block the light that enters the camera's light receiving area, so as a countermeasure, make the effective diameter of the conversion lens larger than originally necessary.

Generally, a method is adopted in which a light beam incident on the lens is directed into a light receiving section. Normally, a conversion lens has a large front group lens and a small rear group lens depending on the angle of view of the camera lens. If you try to widen the rear group lens to cover the camera's light-receiving area, if the rear group lens surface facing the camera lens is concave, the edge will become thicker and will not affect performance or anything else. In order to avoid
On the market, there are devices in which a ring-shaped flat glass is placed around the rear group lens so that light enters the light receiving section.

The disadvantage of this case is that although the light also enters the corner light receiving section, the transparent body just in front of the light receiving section does not take into account the relationship with the front group lens, so the light is affected only by the front group lens. , and the light receiving unit measures the illuminance in a different direction rather than the intended illuminance at the center of the screen.

An object of the present invention is to take nine measures to ensure that regular light enters the light receiving section of the camera when the conversion lens is mounted in a position that covers the exposure metering light receiving section of the camera.

The first invention is to attach a pair of Galilean type or inverse Galilean type optical systems having a rotating surface around the optical axis of the conversion lens to the periphery of the conversion lens, and to direct the emitted light from this to the camera. In this method, the exposure metering light is applied to the light receiving section.

The second invention is a method in which a parallel four-shaped prism is attached to a conversion lens, and light emitted from the prism is made to enter a light receiving section of a camera.

The third invention is to double the lens barrel of the conversion lens and open windows in the support plates of the inner and outer barrels.

Alternatively, the support plate may be made transparent to allow the light incident on the light receiving section of the camera to pass therethrough.

First, the first invention will be explained with reference to the drawings. Figure 1 shows the conversion lens (2) attached to the camera (1).
) is shown. The light receiving part (3) of the camera should normally capture light parallel to the optical axis (5) of the camera lens (4) and measure the light, but it is blocked by the conversion lens, so the first part is blocked by the conversion lens.
As shown in the figure, a for photographing.

Galilean type or reverse Galilean type optical system (8) on the outside of the focal lens (6), (7),
(9) is added. If the attached optical system is a Galilean type as shown in Figure 1, it is necessary to combine so that the rear focal points of both (8) and (9) coincide; The device is designed to match the front focus. The refractive surface of the attached optical system is preferably a surface of rotation about the optical axis of the photographic afocal lens.

The attached optical system is composed of a lens, a Fresnel lens, or a prism. FIG. 2 shows an embodiment of the reverse Kalilei type. In this case, the front lens group (10) is
It is used for both photography and photometry. The attached lens (b) is dedicated to photometry, and the configuration of (to) and 01) creates an afocal system for exposure metering.

The second invention will be explained with reference to the drawings. Is the light receiving part of the camera far away from the camera lens?

This is a case where light entering the peripheral part of the conversion lens or the light receiving part is blocked. Please refer to Figure 3. Since the light receiving section (3) of the camera is shielded by the periphery of the conversion lens (2), a parallel 4 feed prism α East is attached to the conversion lens to allow light into the light receiving section.

The third invention will be explained with reference to two drawings. As shown in Figure 4,
This is the case when the conversion lens is small enough to be placed inside the exposure metering light receiving section (3) of the camera, or when the attachment/detachment section Q→ of the camera and conversion lens is located outside the light receiving section as shown in the figure.

In this case, double the lens barrel of the conversion lens as shown in the diagram, and either open a window in the support plate a of the inner and outer cylinders, or make the support plate transparent, and attach it to the light receiving part of the camera. This is a method in which the incident light is passed parallel to the optical axis.

[Brief explanation of drawings]

The figures relate to the present invention. Figure 1 is a sectional view showing an embodiment of a conversion lens equipped with a Galilean type optical system attached to a camera, and Figure 2 is a conversion lens equipped with a reverse Galilean type optical system. FIG. 3 is a cross-sectional view showing an embodiment of the lens, FIG. 3 is a cross-sectional view when a parallel four-feeding prism is attached, and FIG. 4 is a cross-sectional view when a transparent support is attached to the inner and outer cylinders of a conversion lens. (1)・・・・・・・・・・・・Camera (2)・・・・・・・・・Conversion lens (3)・・・・・・・・・・Light receiving part (4 )・・・・・・・・・Camera lens (5)・
・・・・・・・・・Optical axis (6)・・・・・・・・・A focal lens for photography (power・・・・・・・・・A focal lens for photography・Focal lens (8)・・・・・・・・・Galilei type attached optical system (9)・・・・・・・・・Galilei type attached optical system QO)・・・・・・......Combined lens 0υ......Additional lens for photometry (2)...--Conversion lens (to)...・・・・・・Parallel 4-shaped prism α→・・・・・・・・・・・・Removal part α0・・・・・・・・・・・・Support plate

Claims (1)

[Scope of Claims] Around the conversion lens, an afocal optical system having the optical axis of the lens as the optical axis, a parallel 4 openwork prism, or a transparent body. A conversion lens that is equipped with the above components to allow light parallel to the optical axis of the conversion lens to enter the light receiving section of the camera.