Imaging device with gated integrator

Abstract

The present invention relates to an imaging device that includes a gating element which receives incident photons and releases pulsed electrons; a single microchannel-plate (MCP) which receives the pulsed electrons and amplifies the pulsed electrons as an amplified pulsed electron flux; a collection element which receives the amplified pulsed electron flux; a high-pass filter; and a gated integrator; wherein the high-pass filter element receives the amplified pulsed electron flux from the collection element and alternate current (AC) couples the amplified pulsed electron flux as a charge pulse to the gated integrator; and wherein the gating element and the gated integrator are time-synchronized to allow charge-integration only while the AC-coupled charge pulse is unipolar. A feedback loop can provide an auto-gating function. The imaging device can be used in night vision goggles or a mass spectrometer.

Claims

1. An imaging device, the imaging device comprising: a gating element which receives incident photons and releases pulsed electrons; a single microchannel-plate (MCP) which receives said pulsed electrons and amplifies said pulsed electrons as an amplified pulsed electron flux; a collection element which receives said amplified pulsed electron flux; a high-pass filter element; and a gated integrator, wherein said high-pass filter receives said amplified pulsed electron flux from said collection element and alternate current (AC) couples said amplified pulsed electron flux as a charge pulse to said gated integrator; and wherein said gating element and said gated integrator are time-synchronized to allow charge-integration only while said AC-coupled charge pulse is unipolar.

2. The imaging device of claim 1, the imaging device further comprising: a feedback loop disposed between said gated integrator and said gating element, said feedback loop which provides an auto-gating function.

3. The imaging device of claim 2, wherein the imaging device is night vision goggles.

4. The imaging device of claim 1, wherein the imaging device is a mass spectrometer, and wherein said gating element is an electrostatic lens and serves to modulate particle flux from incident flux.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The description of the drawings includes exemplary embodiments of the disclosure and are not to be considered as limiting in scope.

(2) FIG. 1 is a functional block diagram of a microchannel arrangement in a prior art imaging device, such as a night vision goggles.

(3) FIG. 2 is a functional block diagram of a microchannel arrangement in an imaging device, such as a night vision goggles, illustrating the improved sensitivity of the present invention (AC-coupled current measurement with gated integrator) over the prior art (DC-coupled current measurement with electrometer).

DESCRIPTION OF THE INVENTION

(4) The present invention relates to a gated integrator for use with a plurality of photon or particle imaging devices, including but not limited to night vision goggles, or a mass spectrometer, and which uses a single microchannel-plate (MCP) with an alternating current (AC)-coupled output capable of providing high temporal resolution and high sensitivity measurements.

(5) In one embodiment, the present invention obtains a more rapid, sensitive estimate of a pulsed microchannel-plate-based (MCP) output current obtained using a high-pass filter element 210 and gated charge-integrator circuit 212 (see FIG. 2), rather than the prior art DC electrometer 110 (FIG. 1). The high-pass filter 210 isolates the time-varying pulses from the DC bias of the collection element 206. The gated integrator 212 or boxcar average 212, integrates the signal input voltage after a defined waiting time (trigger delay) over a specified time (gate width) and then averages over multiple integration results.

(6) In one embodiment, the present invention is directed to a single MCP 204 (see FIG. 2) that serves as a current amplification device placed between a gating element 202 (i.e., photocathode 202) and a collection element or 206 (i.e., phosphor screen 206). A high-pass filter element 210 is connected to either the back surface of the MCP 204 (to measure image charge), or the collection element 206 (to measure secondary electrons 205) to a gated integrator device 212.

(7) In one embodiment, the incident photons (flux) 201 strike the gating element 202, such as a negatively biased photocathode 202, which then releases electrons 203 that act as a pulsed flux 203, the electrons 203 which are accelerated towards the single MCP detector 204. The MCP 204 amplifies the electrons 205 as an amplified pulsed electron flux 205 by several orders of magnitude, to then be captured by the collection element 206 such as phosphor screen 206.

(8) In one embodiment, when the gating element 202 opens for a short period of time (i.e., on the order of a few microseconds), the MCP 204 produces a pulse of secondary electrons 205 that is alternate current (AC)-coupled (pulsed electron current 209) from the collection element 206 through the high-pass filter element 210, as filtered electron current 211, to the gated (boxcar) integrator 212 of the present invention.

(9) In one embodiment, the gating element 202 and the gated integrator 212 are time-synchronized to allow for charge-integration only while the AC-coupled charge pulse is unipolar (either positive or negative). This configuration provides a high signal-to-noise measurement of the output 211 of a single MCP 204 on a microsecond time scale.

(10) In one embodiment, the output 213 from the gated integrator device 212 can be incorporated into a feedback loop (feedback control element 214) with the gating element 202, providing a highly sensitive auto-gating function (gating control 214), as would be needed in, for example, night-vision goggles.

(11) In one embodiment, the present invention enables high-time resolution measurements of particle beams for mass spectrometer instruments and laboratory beam diagnostics and provides a technique to sensitively quantify output from a single MCP.

(12) In one embodiment, by using an MCP 204 in a mass spectrometer, and gating the incident particle flux 201 through electrostatic deflection to avoid MCP 204 saturation, and combining with either a pulse detector or a gated integrator circuit 2012, the dynamic range of mass spectrometers could be significantly enhanced. Because of the larger range of overlap of a pulsed single-plate MCP 204 (˜0.1 pA up to ˜1 nA) with both the Faraday cup current and secondary electron multiplier (SEM) flux measurements found in mass spectrometers, improved cross-calibration between the measurement devices can likely be achieved, allowing for more precise estimates of mass composition.

(13) The present invention may be used in a variety of imaging devices in addition to night vision goggles, or mass spectrometers.

(14) It should be emphasized that the above-described embodiments of the invention are merely possible examples of implementations set forth for a clear understanding of the principles of the invention. Variations and modifications may be made to the above-described embodiments of the invention without departing from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of the invention and protected by the following claims.