Global shutter for transmission mode secondary electron intensifier by a low voltage signal
A night vision system along with an image intensifier tube and method for shuttering the continued draw of electrons from an electron multiplier are provided. The night vision system includes the electron multiplier, or possibly two electron multipliers, each comprising a silicon membrane. A shutter voltage is applied between a first surface and a substantially parallel, opposed second surface of the silicon membrane to discontinue draw of electrons through the electron multiplier and for substantially discontinuing display of an image from the image intensifier tube under certain bright light conditions. Utilizing a global shutter control on the electron multiplier, and the significantly lower voltage for such control mitigates power consumption within the image intensifier, as well as electromagnetic interference and delay response time. A relatively low voltage negative bias shutter voltage on only the electron multiplier selectively provides global shutter to the image intensifier device.
1. An image intensifier tube, comprising:
an electron multiplier spaced in a vacuum between a photocathode and an anode, wherein the anode is comprised of a phosphor coating side, wherein the phosphor coating side is in the vacuum and faces the electron multiplier, and wherein the electron multiplier comprises a semiconductor die;
a digital imager, wherein the digital imager is configured to send electrical signals across an electrical bus onto the electron multiplier;
a positive bias variable first voltage coupled between the photocathode and the electron multiplier to draw electrons from the photocathode onto the electron multiplier;
a negative bias shutter voltage coupled across opposed surface of the electron multiplier to shutter continued draw of electrons from the electron multiplier for substantially discontinuing display of an image from the image intensifier tube;
a positive bias variable second voltage of between 250 volts to 2000 volts coupled from an automatic brightness controller between the electron multiplier and a ground supply, wherein the positive bias variable second voltage is coupled between the electron multiplier and a second electron multiplier that is coupled to the ground supply; and
a positive bias third voltage between 4150 to 4275 volts coupled between the ground supply and the anode.
2. The image intensifier tube of claim 1 , wherein the positive bias first voltage comprises negative and positive terminals of a first voltage source, wherein the negative terminal of the first voltage source is coupled to the photocathode, and wherein the positive terminal of the first voltage source is coupled to an electron entry surface of the electron multiplier.
3. The image intensifier tube of claim 2 , wherein the negative bias shutter voltage comprises positive and negative terminals of a shutter voltage source, wherein the positive terminal of the shutter voltage source is coupled to the electron entry surface of the electron multiplier, and wherein the negative terminal of the shutter voltage source is coupled to a multiplied electron emission surface of the electron multiplier.
4. The image intensifier tube of claim 1 , wherein the positive bias first voltage is between 200 to 2000 volts.
5. The image intensifier tube of claim 1 , wherein the positive bias first voltage is variable.
6. A method for shuttering the continued draw of electrons from an electron multiplier within an image intensifier tube, wherein the image intensifier tube comprises said electron multiplier spaced in a vacuum between a photocathode and an anode, wherein the anode is comprised of a phosphor coating side, wherein the phosphor coating side is in the vacuum and faces the electron multiplier, wherein the electron multiplier comprises a semiconductor die, wherein a digital imager is configured to send electrical signals across an electrical bus onto the electron multiplier, wherein a positive bias variable first voltage is coupled between the photocathode and the electron multiplier to draw electrons from the photocathode onto the electron multiplier, wherein a negative bias shutter voltage is coupled across opposed surface of the electron multiplier to shutter continued draw of electrons from the electron multiplier for substantially discontinuing display of an image from the image intensifier tube, wherein a positive bias variable second voltage of between 250 volts to 2000 volts is coupled from an automatic brightness controller between the electron multiplier and a ground supply, wherein the positive bias variable second voltage is coupled between the electron multiplier and a second electron multiplier that is coupled to the ground supply, and wherein a positive bias third voltage between 4150 to 4275 volts is coupled between the ground supply and the anode, comprising:
applying a positive bias between said photocathode and an electron entry surface of the electron multiplier to draw multiplied electrons to the electron multiplier;
applying a negative shutter bias between the electron entry surface and a multiplied electron emission surface of the electron multiplier to substantially discontinue the draw of multiplied electrons through the electron multiplier.
7. The method of claim 6 , wherein applying the negative shutter bias that changes in magnitude depending on reading of current within a phosphor covered anode screen.
8. The method of claim 7 , further comprises applying a different positive bias between the photocathode and the electron entry surface reduced if photocurrent through the photocathode or if current through the phosphor covered anode screen exceeds a pre-determined amount.
9. The method of claim 6 , further comprises changing the positive bias depending on intensity readings taken on a phosphor covered anode screen.
10. The method of claim 6 , further comprises switchably applying the negative shutter bias depending on intensity readings taken on a phosphor covered anode screen.