Method and system for communicating pulse width in a night vision system power system

A night vision system including a power system having a low voltage unit coupled to a high voltage unit. The low voltage unit includes a low voltage controller and a low voltage table correlating step values to pulse widths, the low voltage controller obtaining a desired pulse width and accessing the table to obtain a step value. The high voltage unit including an opto-isolator for receiving the step value from the low voltage controller, a high voltage controller response to the step value accessing a high voltage table correlating step values to pulse width to obtain a pulse width, the high voltage controller generating a control pulse in response to the pulse width.

BACKGROUND OF THE INVENTION

Night vision systems are used in a number of applications, including military, industrial, commercial, etc. In general, the systems operate by multiplying light received at an image intensifier tube to generate a visible image. Power conservation is typically an issue with personal night vision systems that are powered by portable, battery supplies. Thus, it is beneficial to incorporate power conservation features in the night vision system in order to extend the operation of the night vision system.

BRIEF SUMMARY OF THE INVENTION

An embodiment of the invention is a night vision system including a power system having a low voltage unit coupled to a high voltage unit. The low voltage unit includes a low voltage controller and a low voltage table correlating step values to pulse widths, the low voltage controller obtaining a desired pulse width and accessing the table to obtain a step value. The high voltage unit including an opto-isolator for receiving the step value from the low voltage controller, a high voltage controller response to the step value accessing a high voltage table correlating step values to pulse width to obtain a pulse width, the high voltage controller generating a control pulse in response to the pulse width.

Other embodiments of the invention include methods for controlling a night vision system. In a low voltage unit, a desired pulse width is obtained. A low voltage table is accessed to obtain a step value. The step value is transmitted to a high voltage unit. The high voltage unit accesses a high voltage table correlating step values to pulse width to obtain a pulse width. The high voltage unit generates a control pulse in response to the pulse width.

DETAILED DESCRIPTION

FIG. 1is a block diagram of power components of a night vision system in exemplary embodiments. The power components include a low voltage unit100and a high voltage unit200. The low voltage unit100and the high voltage unit200operate with a significant voltFIG. 1is a block diagram of power components of a night vision system in exemplary embodiments. The power components include a low voltage unit100and a high voltage unit200. The low voltage unit100and the high voltage unit200operate with a significant voltage potential difference between them. The low voltage unit100includes a low voltage controller102in communication with low voltage electronics104and an opto-isolator202in the high voltage unit200. The low voltage electronics104may include amplifiers, inverters, transformers, etc. A battery108is coupled to the low voltage electronics104to provide power to the high voltage unit200.

The low voltage controller102may be a general-purpose microprocessor executing a computer code contained on a storage medium. Alternatively, the low voltage controller102may be implemented using a wide variety of other technologies including a special purpose computer, a computer system including a microcomputer, mini-computer or mainframe for example, a programmed microprocessor, a micro-controller, a peripheral integrated circuit element, a CSIC (Customer Specific Integrated Circuit) or ASIC (Application Specific Integrated Circuit) or other integrated circuit, a logic circuit, a digital signal processor, a programmable logic device such as a FPGA, PLD, PLA or PAL, or any other device or arrangement of devices that is capable of implementing the steps of processes in embodiments of the invention.

The low voltage controller102interfaces with a low voltage table103to retrieve a step value that is transmitted to the high voltage unit as described in further detail herein. Low voltage table103may be a look-up table through which the low power controller102obtains a step value based on a desired pulse width. Low voltage table103may be stored in memory located in low power controller102or a separate device accessible by low power controller102.

The opto-isolator202serves as an optically isolated one-way data link used to transfer information from the low voltage unit100to the high voltage unit200. One of the information items is a step value, which corresponds to a desired pulse width. The step value represents the desired pulse width to be used in the high voltage unit and is obtained from low voltage table103as described in further detail herein. In an exemplary embodiment, the step value is an N-bit digital word representing the desired pulse width. Once the step value is received by the high voltage unit200, the high voltage200generates a control pulse with a duration between 1250 μs and 300 ns by accessing high voltage table203with the step value. The opto-isolator202receives the step value and provides the step value to the high voltage controller204. The high voltage controller204uses the step value to interface with pulse shaping module210to control high voltage power electronics206that bias the night vision system.

The high voltage controller204interfaces with high voltage table203to retrieve a pulse width in response to the step value transmitted from the low voltage unit100. High voltage table203may be a look-up table through which the high power controller204obtains a pulse width based on the received step value. High voltage table203may be stored in memory located in high power controller204or a separate device accessible by high power controller204.

A conventional method of defining a pulse width is to create a digital word where each count equals the minimum resolution. In power system ofFIG. 1with a minimum pulse resolution of 1 ns and a maximum value of 1250 μs, a digital word scaled at 1 count=1 ns would need to be capable of storing 1,250,000 counts to accommodate the desired resolution and maximum range. This requires a 21 bit digital word to represent 1,250,000 counts.

As noted above, a constraint of the night vision power system is power consumption. Sending 21 data bits drives up system power due to the energy required to drive the opto-transmitter for that many bits as well as the real-time power consumption needed during the data transmission and reception.

As described above, the low voltage unit accesses low voltage table103to obtain a step value corresponding to a desired pulse width. The step value uses a reduced number of bits to communicate the pulse width. Exemplary step values and pulse widths are shown in Table 1. The pulse values start at the maximum, e.g., 1250 μs and go down by a percentage (e.g., 2.5%) in each step. A total of 336 steps are defined from 0 to 335 corresponding to pulse widths from 1250 μs to 319 ns.

In operation, the low voltage controller102determines the desired pulse width and accesses low voltage table103to determine the appropriate step value. The low voltage unit100sends a digital word representing the step value by accessing low voltage table103indexing the desired pulse width to the step value. Accordingly, instead of sending the pulse width value across the data link, a step value from Table 1 is sent. Using this method, the data transmitted across the data link need only be 10 bits as opposed to 21 bits if the pulse width value is sent. Nine bits are used to send the step value and a tenth bit may be included as a steering bit to direct the 9 bit word to the appropriate high power circuitry. Sending 10 bits results in a 2× power reduction and transmission time reduction as compared to sending 21 bits.

The low voltage controller102sends the step value to the high voltage controller204through opto-isolator202. The high voltage controller204accesses high voltage table203, which is a local copy of low voltage table103, and determines the pulse width corresponding to the received step value. The high voltage controller202causes this pulse width to be produced though pulse shaping module210, which in-turn drives high voltage electronics206through a control pulse. For example, the high voltage electronics206may include a digital to analog converter and several analog output functions, all of which reside in the high voltage block.

This communication protocol uses less power and communication time than standard digital communication protocols. Using tables103and203provides fast, low power operation. The use of a correlation table based upon a 2.5% change between steps results in a logarithmic scaling relationship between inputs to output.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed for carrying out the invention, but that the invention will include all embodiments falling within the scope of the appended claims.