Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
1998-10-28
2001-09-11
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C313S532000
Reexamination Certificate
active
06288386
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to electronic circuits and in particular to an electronic circuit including a flexible printed circuit board and a rigid printed circuit board incorporated into a monocular night vision device for electronically connecting components within the lower and upper housing improved night vision operation.
BACKGROUND OF THE INVENTION
A monocular night vision system basically incorporates a single eyepiece lens assembly, image intensifier assembly, and objective lens assembly. Most monocular night vision devices (MNVDs) are compact and lightweight to optimize hand-held use. MNVDS are often referred to as pocket scopes since they could optimally be small enough to be stored in a user's pockets.
Numerous MNVDs exist in the prior art. Examples of some of these night vision devices, including hand-held night vision devices, include U.S. patent application Ser. No. 08/108,989 entitled NIGHT VISION MONOCULARS, filed Aug. 18, 1993; U.S. patent application Ser. No. 08/405,172 entitled COMPACT NIGHT VISION DEVICE, filed Mar. 16, 1995; U.S. Pat. No. 5,644,425, issued Jul. 1, 1997, entitled NIGHT VISION MONOCULAR WITH UNISTRUCTURAL OPTICAL BED also teaches a hand-held night vision device for use in both military and non-military applications, however these devices generally suffer from a combination of poor performance characteristics and design shortcomings which lead to inefficient device operation or limited flexibility, and poor performance. For example, a number of the monocular night vision devices have main housings which are made of metallic material which make them rugged, but heavy. Moreover, prior art MNVDs are often bulky and uncomfortable to hold in one's hand and are difficult to operate when deployed in completely dark areas. Furthermore, prior art MNVDs are often energy efficient, expending battery power even when not in use, such as during daylight. In the event of a headmounted device, prior art MNVDs did not automatically turn off when removed from the helmet mount or when flipped up in the helmet mount. Still further, prior art devices could not be mounted to an M16/M4 receiver rail configured for the Modular Weapon System Kit (which fits the mounting rail defined in MIL-STD-93), and standard AN/PVS-7 accessories such as the lens cap, sacrificial filter, compass, 3X magnifier, and light interference filter could not be attached to the objective lens assembly of these devices.
As one can ascertain, night vision systems frequently need to include some control functions beyond just “on” and “off”. Users commonly want additional features such as: a low-battery indicator, an infrared illuminator for use in very dark areas, an indicator that the infrared illuminator is activated, an automatic cut-off in high-light conditions, an automatic cut-off when the viewing device is flipped up to a stowed position or removed from its mount, and a variable gain control. These features can be implemented piecemeal, or as parts of an integrated control system.
The prior art AN/PVS-7 night vision device, manufactured by IT Corporation, the assignee herein, represents an integrated control system device. The AN/PVS-7 is a binocular viewer having one objective lens, one image intensifier tube, and two eyepieces which view the same output image from the tube via an arrangement of a beam splitter and turning mirrors. The AN/PVS-7 is intended predominantly for use by military ground forces, and can be hand-held or attached to a head mount or helmet mount.
The AN/PVS-7 includes a control circuit which is an application-specific integrated circuit (ASIC), implemented in a complementary metal-oxide semiconductor (CMOS) process, and including both digital and analog subcircuits. This ASIC includes a high-light cutoff circuit described in commonly assigned U.S. Pat. No. 4,843,29, entitled HIGH LIGHT LEVEL CUTOFF APPARATUS FOR USE WITH NIGHT VISION DEVICE, issued to J. Reed and J. Caserta, and incorporated herein by reference.
FIG. 6
shows the prior art circuit illustrated in the above patent (FIG. 2 of U.S. Pat. No. 4,843,229) where most of the functional blocks shown are contained in the ASIC. Only the light sensor
8
, the crystal
22
, the voltage multiplier
4
, the power field-effect transistor (FET)
3
, the battery
1
, the goggles (intensifier tube)
2
, and the on/off switch are not located inside the ASIC, due to their unsuitability for implementation in the CMOS process. The crystal
22
may be replaced by a resistor-capacitor (RC) timing network, in order to reduce cost while still providing sufficient timing accuracy. This ASIC also includes circuitry to implement a flashing low-battery indicator and flip-up cutoff. In the AN/PVS-7, the ASIC and its associated electronic parts, including the voltage multiplier
4
, the power FET
3
, RC timing network, and some associated power filtering components are assembled on one small surface-mount rigid printed circuit board or ceramic substrate. Other parts, including the on/off/ir switch, the connections for the intensifier tube, the light sensor (photo resistor or photo transistor), the infrared illuminator, the low battery indicator light-emitting diode (LED), the infrared indicator LED, and the magnetic reed switch (which is the sensor for the flip-up cutoff function) are required to be located elsewhere in the overall housing, due to physical access or optical exposure requirements. These parts are interconnected to the main circuit via a flexible polyamide circuit with etched copper conductors. The battery contacts are connected by wires to the rest of the circuit.
The flip-up cutoff feature assures that the user does not inadvertently leave the viewing device on or give away his position by exposing the glow from the intensifier, when the viewing device is removed from its mount or is flipped up to the stowed position. The flip-up cutoff feature functions as follows. The magnetic reed switch is placed in the AN/PVS-7 viewing device housing, inside the housing wall which is in proximity to the mounting point. The magnetic reed switch is a single-pole, double-throw device. In the de-energized (no magnetic field applied) state, the magnetic reed switch connects an input of the ASIC to the positive supply voltage considered logic “high”. In the energized (magnetic field applied) state, the magnetic reed switch connects the input of the ASIC to the negative supply voltage. This is considered logic “low”. A small magnet is placed in the head mount and helmet mount, in a location proximal to the mounting point for the viewing device. When the viewing device is installed in the mount, the magnetic reed switch comes in proximity to the magnet, the reed switch is energized, and the ASIC input transits from a logic high state to a logic low state, provided the viewing device has been turned on. The ASIC contains logic which ignores the reed switch state at the moment when the viewing device is turned on, and also ignores high-to-low transitions of the input from the reed switch. Thus, the viewing device can be switched on whether or not it is in the mount, and the viewing device will not turn off when it is installed in the mount. When the viewing device is removed from the mount or flipped up to the stowed position in the mount, the magnetic reed switch is separated from proximity to the magnet. The reed switch is thus de-energized, and the ASIC input transits from a logic low state to a logic high state, (provided the viewing device has been turned on). The transition from low to high is interpreted by the logic in the ASIC as a command to turn the intensifier off, causing the latching flip-flop
7
to close, grounding the gate electrode of the power FET
3
. The power FET
3
ceases to conduct, turning off the intensifier and turning off the infrared illuminator and indicator, if on. Once the ASIC turns the intensifier off, the user must switch the viewing off and back on to restore the operation of the intensifier.
The low battery indicator provides a visual warning to the user tha
Bowen James H.
Bryant Mark A.
Clamme Michael S.
Schlotthober Nathan R.
Duane Morris & Heckscher
ITT Manufacturing Enterprises Inc.
Le Que T.
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