Patent ID: 12216265

Corresponding reference characters indicate corresponding parts in the drawing.

DETAILED DESCRIPTION

Referring now to the drawing, the night vision device includes a housing8having a first end and a second end. An objective lens10that receives ambient light is mounted on the housing8and located nearer to the first end than to the second end. As illustrated, the objective lens is located at the first end of the housing8. Light received by the objective lens10is directed to a photocathode plate12supported in the housing8. Although the objective lens10is shown as a single, unitary lens it may have other configurations having more than one lens. The photocathode plate12is negatively charged. Light impinging on the photocathode plate12causes electrons to be released from the photocathode plate, which are then accelerated toward a microchannel plate14(e.g., an intensifier) biased to a higher voltage than the photocathode plate. Impact of the electrons on the microchannel plate14causes an even greater number of electrons to be released, thereby effectively augmenting the intensity of the image. In the illustrated embodiment, the photocathode plate12and microchannel plate14can be considered “an image intensifier.” However, other components and arrangements could be used for the purpose of strengthening the image signal. The image intensifier is mounted on the housing8and generally located toward the second end of the housing from the first end.

A phosphor screen16is biased to an even higher voltage than the microchannel plate14. Electrons from the microchannel plate14are accelerated toward and impinge upon the phosphor screen16. Generally, the phosphor screen16has been green, but more recently has been white. However, any suitable color may be used. As a result of the electron impingement, the phosphor screen16emits photons that pass through a first eyepiece lens18and a second eyepiece lens20to the user's eye (not shown). The first and second eyepiece lenses18,20are mounted on the housing8and located toward the second end of the housing from the objective lens10. As illustrated, the second eyepiece lens20is located at the second end of the housing8. The user would position his or her eye just to the right of the second end of the housing8. It will be understood that there may be a greater or fewer number of eyepiece lenses than shown, and at least some of the components may be located other than as illustrated. Moreover, the precise configuration and number of lenses, plates and screens may be other than described.

The night vision device is constructed to permit auto-focusing for the purpose of automatically maintaining the largest depth of field allowed by the ambient light available. In that regard, the night vision device includes an adjustable iris22mounted on the housing8and located toward the second end of the housing from the first objective lens. As illustrated, the adjustable iris22is positioned between the objective lens10and the photocathode plate12. Keeping the iris opening small maximizes the depth of field of the night vision device. Having a large depth of field means that persons and objects viewed through the night vision device will be in focus for the viewer over a greater range of distance from the viewer (and the night vision device). However, restricting the iris opening reduces the amount of light that impinges upon the photocathode plate12. Depending upon the amount of light available, the night vision device may not be able to intensify the image sufficiently to be seen if the iris opening is too small. Accordingly, a light intensity sensor24is connected to the housing8and positioned proximate the viewer's eye to measure the intensity of light that reaches the viewers eye. In the illustrated embodiment, the sensor24is positioned just before the second eyepiece lens20. The sensor24is connected to a motor forming part of the adjustable iris22.

The sensor24operates to keep the depth of field of the night vision device generally as large as possible given the amount of available (ambient) light. For example, when the sensor24detects that light reaching the user's eye has fallen below a predetermined minimum or boundary, the sensor sends a signal to the motor of the adjustable iris22. The signal causes the motor to open the iris22. The amount the iris22is opened can be a predetermined increment, based on the amount by which the light detected by the sensor24falls below the minimum set point, or in according to another suitable algorithm. Increasing the area of the opening of the iris22increases the amount of light passing through. When the sensor24detects light within an acceptable range, the opening if the adjustable iris22is held. Increasing the area of the opening of the iris22reduces somewhat the depth of field of the night vision device. When the user of the night vision device moves into an environment in which there is more light, this is detected by the sensor24. As a result of the detected light intensity being above a maximum or upper boundary, a signal is sent to the adjustable iris22causing the iris opening to become smaller. For example, the signal may be sent when the light detected by the sensor24exceeds a predetermined amount. Closing the iris22increases the depth of field, causing the surrounding people and objects to be in focus over a greater range from the user of the night vision device. The upper and lower light intensity boundaries used by the sensor may be adjusted, for example according to the visual acuity of the particular user. The lower light intensity boundary is selected to that there is a good visual perception of the image being viewed through the night vision device. It is envisioned that the sensor24may simply signal the level of light intensity and that the algorithm determining how much to adjust the iris opening can be associated with the adjustable iris22. Generally, the control of the iris22is biased to keep the opening as small as possible while permitting visual perception of the surroundings. The sensor24is shown schematically as being connected to the iris22, but could be connected to another device controlling the iris. Although the night vision device is discussed in terms of being worn, it will be understood that is but one configuration within the scope of the present invention. The night vision device could be carried or mounted on another object (e.g., a firearm) within the scope of the present invention.

In one embodiment, when the control of the iris22is activated, an algorithm operates to open the iris be stepped amounts. As each step is reached, the sensor24is queried to learn the amount of light now reaching the sensor. If the amount of light is below a predetermined level, the iris22is controlled to open another stepped amount. This process is repeated until a desired light intensity at the sensor24is reached. However, this process does not end. If the light intensity above the desired amount by more than a predetermined threshold, the iris22will be controlled to close by a stepped amount (typically smaller than the steps used for opening the iris). Only when the light intensity at the sensor24lies within a predetermined boundary does the adjustment of the iris opening stop. The presence of the upper boundary and step-down function allows the field of view to be maximized at all times. In a fully automatic mode, the algorithm runs continuously based on variances experienced by the sensor24in the light level. This is effective, but has a greater power demand on the battery28. Accordingly, in a semi-automatic mode (sometimes referred to as a “manual” mode), the algorithm would run only when a button (not show) on the night vision device is pressed. For example, when a soldier moves from one location (e.g., outside) to another location (e.g., inside a building), the solder must press the button in order to cause the algorithm to run and adjust the iris opening and hence the light intensity. It should be understood that predetermined threshold above the desired amount of light intensity used by the algorithm is not selected for purposes of preventing the user from being unable to see due to the light intensity being too great, but rather is selected to drive the iris opening at any given light level toward a predetermined minimum necessary for visual perception.

A power switch26and power source (e.g., a battery28), both schematically illustrated, can be provided to permit automatic adjustment of the iris opening of the adjustable iris22when switched on. A power adjustment of the objective lens is also permitted using structures and techniques well known to those of ordinary skill in the art. It is envisioned that when the power switch is switched off that (fully) manual adjustment would be permitted. More specifically, manual adjustment of both the iris opening, and also of the objective lens is permitted for purposes of changing the focus of the objective lens. Suitable structure (not shown) is provided that is accessible on the exterior of the housing for making the adjustments.

In still another embodiment, the night vision device has different settings. For example, there may be a low, medium and high setting. The low setting would reduce the light intensity number used to control the opening of the iris22. The medium setting would increase that intensity number. The high setting would increase the light intensity number further. In this way, the user can select an operating mode that corresponds with their particular visual acuity. In other words, some users have a greater ability to see in low light situations that others. Those users could select the medium or low setting and thereby even further improve the field of view in operation of the night vision device.

Taking as an example, the use by an infantryman on patrol using the night vision device, when the user is outside, there may be ample light (e.g., from the moon and/or stars). In that case, the sensor24will cause the adjustable iris22to shut down the opening substantially, giving the infantryman a large depth of field from near to the user to a substantial distance away in which objects will be in focus. However, the infantryman may move into a building or other structure that is unlit and moreover blocks out much of the light available out of doors. The night vision device of the current invention detects (using sensor24) the drop in light being admitted into the night vision device and automatically opens the iris22. However, the opening occurs only to the extent required to make people and objects visible to the user. Once sufficient light intensity is detected by the sensor24, the iris is opened no further, and may be closed somewhat even if the light intensity being experienced would not result in any loss of visual perception. As a result, the depth of field is maintained as large as permitted by the available light. In one sense, the night vision device has an image intensifier and an adjustable iris which cooperate to maintain a large depth of field of vision while maintaining the amount of light reaching the user's eye at a level permitting visual perception of the object(s) viewed.

Having described the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. For example, where specific dimensions are given, it will be understood that they are exemplary only and other dimensions are possible.

When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above products without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.