JPH0296722A - Strobe light controller for single-lens reflex camera - Google Patents

Abstract

PURPOSE:To restrain deviation and to set any sensitivity distribution by providing a light splitting means in an optical path and installing a strobe light control sensor outside the optical path. CONSTITUTION:The photometry sensor 3 is provided on the outside of the optical path behind the outgoing plane of a penta-prism, the light splittig means 1 is placed in the optical path between the outgoing plane of the penta-prism 6 and the photometry sensor 3, and the strobe light control sensor 2 is provided on a position outside the optical path. In this position, a distance between the sensor 2 and the optical path is almost identical to a distance between the sensor 3 and the optical path. In such a manner the light splitting means is provided between the outgoing plane of the penta-prism and the light control sensor and the photometry sensor is installed outside the optical path, thereby controlling the strobe light. Consequently, the deviation of light control sensitivity distribution due to squit light control is restrained, and the degree of freedom in installing the light control sensor can be increased. In addition, the light control result is not affected by the difference of reflectance between film surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a strobe light control device for a single-lens reflex camera having a semi-transparent fixed mirror.

[Conventional technology]

Figure 4 shows the installation position of a strobe light control device for a conventional single-lens reflex camera with a semi-transparent fixed mirror. 2 is a light control sensor for strobe light control, 3 is a photometry (AE) sensor, and 4 is an infrared cut filter. , 6 is a pentaprism,
7 is a semi-transparent fixed mirror, 8 is a film surface, 9 is a detachable photographic lens, 10 is a focusing plate, 11 is an AP sensor, and 12 is a sub-mirror.

Light incident on the detachable photographic lens 9 is split into transmitted light and reflected light by a semi-transparent fixed mirror 7. The transmitted light is guided to the film surface 8. Normally, the film surface is shielded from light by a known shutter mechanism and exposed by a release operation. A portion of the transmitted light is reflected by the sub-mirror 12 and enters the AP sensor 11. During photographing, the submirror is retracted to a position where transmitted light does not interfere with image formation on the film surface. On the other hand, the reflected light enters a photometric sensor installed outside the finder optical axis behind the exit surface of the finder prism 6 so as to look into the focusing plate 10.

The strobe light control sensor 2 is a distance measurement (AF) sensor, which is a sub-mirror sensor in a retracted state, and is installed in a position that does not interfere with the semi-transparent fixed mirror so as to face the film surface from outside the main optical axis. Measures the light reflected from the film surface.

[Problems to be Solved by the Invention] However, the above conventional example has the following drawbacks regarding the arrangement of the light control sensor.

(1) Since the light control sensor is in a state where it is facing the film surface, the light control sensitivity distribution is uneven.

(2) Since it is necessary to avoid interference with the semi-transparent fixed mirror by using the AP sensor as a sub-mirror in the retracted state, there are significant restrictions on the installation position.

(3) Since light is adjusted using reflected light from the film surface, photographing occurs in the strobe light adjustment result due to differences in the reflectance of the film surface.

[Means and effects for solving the problem] Therefore, according to the present invention, a light splitting means is provided in the optical path between the exit surface of the pentaprism and the photometric sensor, and a light control sensor is installed outside the optical path to produce a strobe. By controlling the light, we can suppress the unevenness of the light control sensitivity distribution caused by the conventional dimming, and increase the degree of freedom in the installation position of the light control sensor.
Furthermore, the light control results are not affected by differences in the reflectance of the film surface.

[Embodiment] FIG. 1 is a drawing of a first embodiment that best represents the features of the present invention. In the figure, 1 is a light splitting means, and the names of other members are the same as in the conventional example shown in FIG.

In the above configuration, the photometric sensor 3 is provided off the optical axis behind the exit surface of the pentaprism. The light splitting means 1 is placed in the optical path between the exit surface of the pentaprism and the photometric sensor, and the strobe light control sensor is placed outside the optical path at a position where the optical path length up to the sensor is approximately the same as that of the photometric sensor. There is.

The light incident on the photographic lens is split into transmitted light and reflected light on the semi-transparent fixed mirror 7. Part of the transmitted light passes through submirror 1
2 and enters the AF sensor. On the other hand, the reflected light is further divided by the light splitting means 1 after being emitted from the pentaprism, and the transmitted light enters the photometric sensor 3 and the reflected light enters the light control sensor 2.

For example, a semi-transmissive mirror whose surface is vapor-deposited with Al is used as the light splitting means 1, and the light on the vapor-deposited surface is divided between the photometry side and the dimming side in a well-balanced ratio between the low brightness limit of the photometric sensor 3 and the dimming characteristic of the dimming sensor. It is divided into sides at a ratio of approximately 4:1. In addition, if the division ratio is of this level, other light division means may be used.
It is also possible to utilize the surface reflection of a polyester sheet or glass of about 1 sm to 0.2 sq.

In addition, in this embodiment, there is no restriction on the mounting position of the photometric sensor as in the conventional case, so if the sensitivity distribution of the photometric sensor 2 is spotty, the position of the photometric sensor 2 can be adjusted to defocus, or the diffusive film can be adjusted. It is possible to set any sensitivity distribution regardless of the sensitivity distribution of the photometric sensor, such as by placing it directly in front of the photo sensor to obtain a center-centered dimming sensitivity distribution.

FIG. 2 is a drawing of a second embodiment that best represents the features of the present invention. In the figure, numeral 5 is an infrared cut filter with anti-reflection coating, and the names of other parts are different from the first embodiment shown in Fig. 2. It is not provided.

FIG. 3 is an enlarged view of only the optical path inside the infrared cut filter 5 coated with an antireflection coating in the embodiment shown in FIG.

In the second embodiment, an infrared cut filter 5 whose entire surface is coated with an antireflection coating is used in place of the light splitting means 1 in the first embodiment (FIG. 1). By applying this antireflection coating, only the light that has passed through the infrared cut filter 5 can be guided to the two sensors as shown in FIG. Therefore, in the embodiment of the youngest brother 2, the light splitting means 1 and the infrared cut filter 4 for each of the dimming and photometry sensors in the first embodiment are unnecessary.

[Effects of the Invention] As explained above, by providing a light splitting means in the optical path between the exit surface of the pentaprism and the photometric sensor, and installing a strobe light control sensor outside the light path, light control due to blinding can be prevented. This has the effect of suppressing the bias in the sensitivity distribution, making it easy to set an arbitrary sensitivity distribution, and enabling strobe light control that is not affected by differences in the reflectance of the film surface. Furthermore, since the sensor is located in a completely different optical path system that does not interfere with the transflective fixed mirror, sub-mirror, and AF sensor, there is an effect that the degree of freedom in installation position is increased.

Furthermore, by using an infrared cut filter with anti-reflection coating in place of the light splitting means, the infrared cut filters attached to the light splitting means and the dimming sensor and photometry sensor are no longer required, reducing costs. effective.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views of optical systems showing embodiments of the present invention, and FIG. 3 is a section of the optical path in a second embodiment in which an infrared cut filter is used instead of a semi-transmissive mirror. 4 are cross-sectional views of a conventional optical system. DESCRIPTION OF SYMBOLS 1... Light splitting means, 2... Strobe dimming sensor 3... Photometry sensor 4... Infrared cut filter 5... Infrared cut filter with anti-reflection coating, 6... Pentameter Prism, 7... Semi-transparent fixed mirror 8... Film surface, 9...
... Detachable photographic lens, 10... Focus plate, 11... AF sensor + -
12...Sub mirror

Claims (1)

[Scope of Claims] 1. In a single-lens reflex camera with a semi-transparent fixed mirror, a light splitting means is provided in the optical path from the exit surface of the pentaprism for the finder, and a strobe light control sensor is provided outside the optical path. Features a strobe light control device for single-lens reflex cameras. 2. The strobe light control device for a single-lens reflex camera according to claim 1, wherein an infrared cut filter coated with an antireflection coating is used in place of the dividing means.