JPH0210425Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a photometric device such as an exposure meter, and more particularly to a photometric device that electrically switches its light receiving angle (photometric range).

The idea of changing the light receiving angle of a light meter has been well known, and it is possible to change the light receiving angle of a light meter by displacing optical elements such as apertures, lenses, prisms, etc. (for example, Japanese Patent Publication No. 47
There are various methods, such as configuring a plurality of light receiving systems in advance and switching the optical paths between them.

However, these devices require a considerable amount of space due to their configuration, which is very inconvenient for cameras and other devices where usable space is limited.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a photometric device that can switch the light receiving angle only by applying an electrical signal without requiring a large space.

In order to achieve the above object, the present invention uses a photometry device in which light from a subject is reflected in a predetermined direction by a reflecting mirror and guided to a light-receiving element, by switching between light scattering and non-scattering by applying an electrical signal. a layer of electro-optic material that is controllable and has a predetermined planar pattern shape and thickness; and a transparent electrode for applying the electrical signal to the layer of electro-optic material. A light scattering means is arranged in front of the reflecting mirror, and the light from the object is incident on the reflecting mirror via the electro-optic material layer and the transparent electrode, and the object is reflected by the reflecting mirror. The present invention provides a photometric device comprising a photometric optical path that guides light from the electro-optical material layer and the transparent electrode to the light receiving element. According to the present invention, the light scattering means can be constructed by arranging an electro-optic material layer and a transparent electrode in front of the reflecting mirror that reflects light from the object toward the light-receiving element, so the structure for switching the light-receiving angle is simple. become.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 1 shows an embodiment of an exposure meter in which a photometric device according to the present invention is disposed within a mirror box of a camera.

In the figure, light from an object that has passed through a photographic lens 1 is reflected toward a focus plate 4 by a main reflecting mirror 3 provided between the photographic lens 1 and a film surface 2. Here, a part of the main reflecting mirror 3 is made into a semi-transmissive mirror, and irradiates a part of the transmitted light to the light scattering means E. This light scattering means E includes a support 5, a flat reflecting mirror 6, two transparent electrodes 7a and 7b, a liquid crystal layer 8, and the liquid crystal layer 8 and the electrode 7.
It is composed of spacers 9a, 9b and a cover glass 10 for maintaining the distance between the two electrodes 9a and 7b and insulating the two electrodes. This liquid crystal layer has a certain planar pattern, which faces the photometric optical path. The electrodes 7a, 7b can contact terminals 11a, 11b for applying voltage from each part.

The main reflecting mirror 3 and the light scattering means E are connected by a pivot 12, and are located at the position shown by the solid line during photometry, and at the position shown by the dotted line after being withdrawn from the photographing optical path during photography. During photometry, the electrode 7a,
7b and the terminals 11a, 11b are in contact with each other, and are not in contact with each other at other times. In other words, the electrodes 7a, 7b and the terminal 11
a and 11b come into contact only when the light scattering means is positioned at a predetermined position in the photometric optical path. Therefore, the first
It is possible to apply electrical signals only in the state shown in the diagram.
This application is impossible in a state where it is retracted from the photographing optical path.

The light reflected by the light scattering means E is collected by a condensing lens 13 onto the light receiving surface of the photoelectric conversion element 14 of the exposure meter.

Next, the effect will be explained.

During photometry, when no voltage is applied between the electrodes 7a and 7b, the liquid crystal layer 8 is substantially transparent, as is well known. Therefore, the light scattering means E only functions as the plane reflecting mirror 6. That is, a conjugate image of an area corresponding to the photometric range AC on the film surface 2 is generated at A'C' by the plane reflecting mirror 6, and this is guided to the photoelectric conversion element 14 by the condenser lens 13. At this time, film surface 2
Light directed toward points B and D above does not enter the condenser lens 13. Therefore, although the sensitivity level of the exposure meter is high, the photometry range is within the AC range, as shown by curve a in FIG.

Next, when a voltage is applied between the electrodes 7a and 7b from a control means (not shown), a scattering effect occurs in the liquid crystal layer 8. Therefore, the center P of the exit pupil of the photographic lens 1
The light passing through the liquid crystal layer 8 toward points B and D on the film surface 2 is scattered by the liquid crystal layer 8 and deflected toward the condenser lens 13. This is guided to the photoelectric conversion element 14 by the condensing lens 13. Therefore, the photometry range extends to BD.

Specifically, each of the lights directed toward points B to D on the film surface 2 is radially dispersed by the liquid crystal layer 8 with a certain intensity distribution. Therefore, a portion of the light directed toward points B and D, which could not enter the condensing lens 13, enters the photoelectric conversion element 14 via the condensing lens 13. Further, a part of the light directed to points A and C, which had hitherto been incident on the condenser lens 13, no longer enters the condenser lens 13. In this way, as shown by curve b in FIG. 2, the measurement range is expanded to B and D, although the sensitivity level of the exposure meter is lowered. In addition, examples of liquid crystals that produce such a light scattering effect include the DSM effect (Dynamic Scattering Mode).
Nematic liquid crystals having the following characteristics are known. In general, when an appropriate voltage is applied to a liquid crystal with a thickness of several microns to several tens of microns (for example, when a voltage of several volts is applied to a liquid crystal with a thickness of about 10 microns), a scattering effect comparable to that of ground glass can be obtained. It will be done.
By determining the size and arrangement of the liquid crystal layer and the size and arrangement of the light receiving system in consideration of this scattering characteristic, the spot photometry shown by curve a in Figure 2 approaches the average photometry shown by curve b in the same figure. It is possible to switch to a desired photometry range. At this time, the change in acceptance angle that occurs when a voltage is applied to the liquid crystal layer expands from AC to BD, but the composition, thickness, and applied voltage of the liquid crystal can be selected appropriately depending on design needs. Needless to say. However, it is necessary to consider that as the thickness of the liquid crystal layer increases, the response will be delayed and the applied voltage will have to be increased. (In the case of a camera, it is not preferable to make the liquid crystal layer extremely thick.) According to this embodiment as described above, it is possible to switch the acceptance angle even with a thin liquid crystal layer, so it is possible to switch the light receiving angle even with a thin liquid crystal layer. A photometric device is obtained. Also,
According to this embodiment, an electro-optical material layer (liquid crystal layer 8) is disposed between the conjugate plane A'C' of the film surface formed by the plane reflection mirror 6 and the plane reflection mirror 6, so that the following Effects can be obtained. That is, among the rays of light that go from the photographic lens 1 to points A to D on the film surface, point B
When we focus on the light rays heading toward point B when the liquid crystal layer is transparent, after being reflected by the flat reflecting mirror 6, the light rays are directed in a completely misplaced direction from the photoelectric conversion element 14, that is, toward the exit pupil of the lens. When the light scattering effect of the liquid crystal occurs, the light beam returning to the center can be guided to the photoelectric conversion element 14 as shown by the dotted line in FIG. This effect is caused by the liquid crystal devices 7a and 7 located in front of the plane reflecting mirror 6 in the arrangement shown in FIG.
This becomes even clearer when compared with the case where b, 8, 9a, 9b, and 10 are arranged between the conjugate plane A'C' and the photoelectric conversion element 14. If the liquid crystal device is arranged in the latter manner, in addition to the light rays heading to points A and C, the light rays heading towards point D (which generally has a directionality toward the photoelectric conversion element 14) can be guided to the photoelectric conversion element 14. However, it is not possible to guide the ray toward point B. This is because the light rays shown by the dotted lines in FIG. 1 do not exist in the first place.

In Figure 2, which shows the sensitivity distribution curve of a light meter,
A, B, C, D, and O indicate points on the film surface 2 in FIG.

The sensitivity level of the exposure meter that occurs when switching the photometry range is determined by the selection of the liquid crystal material and the magnitude and frequency of the applied voltage, but the correction must be made in conjunction with conventional exposure meter sensitivity correction means as appropriate. Bye.

Furthermore, electrodes 7a and 7b constituting the light scattering means
It is also possible to locally vary the planar pattern shape, the thickness of the liquid crystal layer 8, etc. to provide different scattering characteristics depending on the location. This results in
For example, the sensitivity distribution curve of the exposure meter can be made asymmetrical in the vertical direction with respect to the central axis PO of the film screen to reduce the sensitivity to light from the sky (curve w in Figure 2).

As shown in FIGS. 3a and 3b, the transparent electrodes 7a and 7b are provided at the periphery of the light scattering means E, and the planar pattern is such that there are no transparent electrodes slightly above the center. When a voltage is applied between the transparent electrodes 7a and 7b, the scattering property is strongly generated only at the periphery.

FIGS. 4a and 4b show another embodiment in which a portion 7c of one transparent electrode 7a is covered with a layer 15 of transparent material.
The thickness of the liquid crystal layer 8 is set so that the thickness of the liquid crystal layer 8 is thicker where transparent electrodes 7a and 7b face each other than where transparent electrodes 7b and 7c face each other. I have to. When a voltage is applied between the transparent electrodes, a stronger electric field is generated where the transparent electrodes 7b and 7c face each other, thereby locally increasing the scattering property. In this case as well, the sensitivity to light from the sky is reduced.

Further, although liquid crystal is used as a material exhibiting scattering properties in the light scattering means E of the present invention, it is not limited to this, and may be an electro-optical material that deflects light by applying a voltage. It may be hot.

According to the present invention configured as described above, the light receiving angle can be switched only by applying an electric signal to the light scattering means including an electro-optic material. In particular, since the electro-optical material that exhibits scattering properties and the transparent electrode are placed in front of the reflecting mirror, the structure is simplified, and almost no space is required to switch the acceptance angle as in the conventional case, so the usable space is reduced. This is effective for cameras and the like in which there are extremely limited quantities.
Furthermore, according to the present invention, when the layer of electro-optic material exhibits a light scattering effect, the light that is scattered by the layer and goes directly to the photoelectric conversion element, and the light that is transmitted through the layer and then reflected by the reflecting mirror. There are light rays that pass through the layer again and head toward the photoelectric conversion element (so-called double scattered light rays), but since they are all scattered toward the photoelectric conversion element, the efficiency of directing the light rays toward the photoelectric conversion element is improved.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, and FIG. 2 shows a sensitivity distribution curve of the light meter according to the present invention. Figure 3a
2 is a front view showing another embodiment of the light scattering means shown in FIG. 1. FIG. Figure 3b shows the X-
It is an X′ cross-sectional view. FIG. 4a is a front view showing another embodiment of the light scattering means shown in FIG. 1.
FIG. 4b is a sectional view taken along the line YY' in FIG. 4a. Explanation of the symbols of the main parts, Film surface...2, Main reflecting mirror...3, Support body...5, Plane reflecting mirror...
6. Transparent electrodes...7a, 7b, liquid crystal layer...8, spacers...9a, 9b, cover glass...10.

Claims (1)

[Claims for Utility Model Registration] A photometric device in which light from a subject is reflected in a predetermined direction by a reflecting mirror and guided to a light receiving element, in which light scattering and non-scattering effects can be switched and controlled by applying an electrical signal. and a layer of an electro-optic material having a predetermined planar pattern shape and thickness;
A transparent electrode for applying the electric signal to the layer of electro-optic material is arranged in front of the reflecting mirror to constitute a light scattering means, and when light from the object passes through the layer of electro-optic material and the transparent electrode, A photometric optical path is configured to guide light from a subject that enters the reflecting mirror via an electrode and is reflected by the reflecting mirror to the light receiving element via the electro-optic material layer and the transparent electrode. Characteristic photometric device.