JPS581503B2 - Anshisouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a night vision device using an image multiplication amount, and particularly to a night vision device using a three-stage image intensifier tube in which three stages are connected in a cascade. be.

image intensifier
Night vision devices using the r ) are known.

There are two types of image intensifier tubes: a first generation type (three-stage type) that connects three stages in a cascade, and a second generation type that uses a multi-channel plate. Although it is cheap, the gain is high and the performance is excellent.

On the other hand, the latter type has excellent afterimage characteristics, uniformity of light quantity distribution, etc., but is expensive even though the cane is lower than that of the three-stage type.

Therefore, the former is more economically advantageous than the latter;
Preferred for practical purposes.

However, in the former case, the screen on the exit surface is darker towards the periphery;
It has the disadvantage that when photographed, only the bright center is visible.

In addition, this type of night vision device also has an automatic dimming device (ABC
- Automatic Brightness Co.
ntrol ) is provided to reduce the overall gain when the amount of light incident on the incident surface increases beyond a certain value.

In other words, automatic adjustment detects the flow of secondary electrons generated according to the amount of incident light that enters the photomultiplier tube, converts the amount of incident light into a current value, and automatically adjusts the multiplication gain according to this current value. A light device is provided.

For this reason, for example, if a bright street light or the like enters a part of the screen, the entire screen becomes dark.

This is a loss of gain, and is inconvenient because the object you are aiming at becomes darker because it is not the object you are directly aiming at.

Furthermore, since the periphery of the screen gradually becomes darker, the entire screen appears dark to the human eye, which is not practical.

In view of the above points, the present invention provides a night vision device that prevents the automatic light control device from working unnecessarily, in order to improve the night vision effect in a conventional night vision device using a three-stage multiplier tube. This is what we intend to provide.

Another object of the present invention is to provide a night vision device that exhibits an easy-to-see screen excluding the dark peripheral areas that cannot be photographed, and therefore allows all visible areas to be photographed.

The night vision device according to the present invention is characterized in that a mask is provided on the entrance surface for shielding the peripheral region where the amount of light is reduced to about a fraction of that at the center on the exit surface.

Here, 1/2 means the peripheral area that is not photographed, and takes into account the latitude of the photographic film (for example, when the shutter speed corresponds to 2 steps, the amount of light is reduced to 1/4).

When the image on the exit surface is photographed, the peripheral area that does not appear on the film remains the same even if it is cut from the beginning, and by making this cut, unnecessary operation of the automatic light control device can be prevented. I can do it.

That is, even if a high-intensity object such as a street light appears in the periphery, it is likely to be cut off by the incident surface, so ABC will not operate and the overall gain will not drop.

Below, I will explain with reference to the drawings.
When the entrance surface of the stage multiplier tube is illuminated with uniform brightness,
On the exit surface 1, the center is bright and the periphery is dark.

When the measurement direction is taken as shown in FIG. 2, this brightness distribution becomes, for example, as shown in FIG. 3.

This is an example of a test, and most three-stage multiplier tubes have this tendency.

The image intensifier tube used for this test was “VARO3
stage 2 5φ”.

As is clear from this graph, the brightness at about 10 degrees from the center is about 25% (one quarter) of the brightness at the center.

In other words, the brightness in the peripheral area outside 20φ of a 25φ multiplier tube is less than about 25% (1/4) of the center, and it is hardly visible on photographic film. It is shown.

Therefore, from the perspective of photography, even if a mask with an aperture of 20 φ is provided on the entrance surface or the exit surface and the peripheral portion outside the 20 φ is cut, there is no loss at all.

In the above case, the present invention provides a light shielding mask 3 having a circular opening of 20φ on the entrance surface 2 of the multiplier tube.
In addition to cutting off the portion outside φ, the above-mentioned automatic light control device is prevented from performing unnecessary operations due to high-brightness objects unrelated to the subject that enter this peripheral portion.

As a result, an inexpensive, high-gain three-stage image intensifier tube can be used as effectively as possible, and the present invention has great practical value.

Furthermore, according to the present invention, a screen is observed where the periphery is cut with high contrast on the exit surface, which gives a much brighter impression to the visual sense than a conventional screen that gradually becomes darker toward the periphery, and has practical effects. is big.

[Brief explanation of the drawing]

FIG. 1 is a vertical side view showing an example of a night vision device according to the present invention;
Figure 2 shows the distribution test positions when testing the brightness distribution on the exit surface of the image multiplier tube, and Figure 3 shows the brightness distribution at test positions A, B, C, and D in Figure 2. This is a graph showing. 1...Exit surface of image intensifier tube, 2...
・Incidence surface of image intensifier tube, 3... Light-shielding mask.

Claims (1)

[Claims] 1. In a night vision device that uses a three-stage image intensifier tube with a built-in automatic light control device that automatically adjusts the multiplication gain according to the amount of light incident on the incident surface, , characterized in that a light-shielding mask having a circular opening is provided to shield the periphery of the incident surface, which corresponds to the periphery where the amount of light is reduced to about a fraction of that at the center on the exit surface of the multiplier tube. Night vision device.