Mach-zehnder based optical marker/comb generator for streak camera calibration

• US 8,970,724 B2
• Filed: 06/14/2013
• Issued: 03/03/2015
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: National Security Technologies LLC
• Original Assignee: National Security Technologies LLC
• Inventors: Miller, Edward Kirk
• Primary Examiner(s): Ho, Tuan
• Assistant Examiner(s): NGUYEN, CHAN T H
• Application Number:
  US13/918,724
• Publication Number:
  US 20140267819A1
• Time in Patent Office: 627 Days
• Field of Search: 348/187, 348/207.99, 348/222.1, 348/239, 250/208.1, 250/559.1
• US Class Current: 348/222.1
• CPC Class Codes: G02F 1/0121 Operation of devices; Circuit arrangements, not otherwise provided for in this subclass
• CPC Class Codes: G02F 1/225 in an optical waveguide structure
• CPC Class Codes: G02F 1/353 Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
• CPC Class Codes: H04N 17/002 for television cameras

Abstract

This disclosure is directed to a method and apparatus for generating marker and comb indicia in an optical environment using a Mach-Zehnder (M-Z) modulator. High speed recording devices are configured to record image or other data defining a high speed event. To calibrate and establish time reference, the markers or combs are indicia which serve as timing pulses (markers) or a constant-frequency train of optical pulses (comb) to be imaged on a streak camera for accurate time based calibration and time reference. The system includes a camera, an optic signal generator which provides an optic signal to an M-Z modulator and biasing and modulation signal generators configured to provide input to the M-Z modulator. An optical reference signal is provided to the M-Z modulator. The M-Z modulator modulates the reference signal to a higher frequency optical signal which is output through a fiber coupled link to the streak camera.

Claims

1. A marker or comb generator for generating optical markers or optical combs for calibration during image recordation of an event:

a reference signal generator configured to generate a pulse stream;

a driver configured to receive and amplify the pulse stream to a magnitude for driving an optic signal generator;

an optic signal generator configured to generate an optic reference signal representing the pulse stream;

a bias modulator configured to generate a bias signal;

a signal generator configured to generate a high frequency modulation signal;

a Mach-Zehnder modulator configured to receive the optic reference signal, the bias signal, and the high frequency modulation signal to generate optical markers or combs at a higher frequency than the reference signal; and

an image recording device configured to record an event to create a recorded image and superimpose the optical markers or optical combs on the recorded image to thereby establish timing calibration or temporal reference on the recorded image.

2. The marker or comb generator of claim 1 wherein the optical signal generator comprises a laser diode.

3. The marker or comb generator of claim 1 wherein the signal generator is configured as a precision frequency source when generating combs.

4. The marker or comb generator of claim 1 wherein the signal generator is configured as a step generator when generating markers.

5. The marker or comb generator of claim 1 further comprising a controller that synchronizes operation of the marker or comb generator with the event.

6. The marker or comb generator of claim 1 where the event comprises a short-duration physical experiment, such as a pulsed laser impinging on a metallic or dielectric object and creating optical and x-ray radiation.

7. An optic calibration signal generator configured to establish an optic calibration signal configured to calibrate a recorded image of an event:

an optic modulator configured to receive and process a bias control signal, an optic reference signal, and a modulation signal to thereby generate the optic calibration signal on an output of the optic modulator;

a fiber link between the optic modulator and a high speed image recording device, the fiber link configured to convey the optic calibration signal to the high speed image recording device;

an optic signal generator configured to convert an amplified reference signal to the optic reference signal;

a driver configured to amplify a reference signal and provide the amplified reference signal to the optic signal generator;

a bias control circuit configured to generate the bias control signal for the optic modulator;

a modulation signal source configured to generate the modulation signal; and

a controller configured to synchronize operation between the high speed image recording device, the optic calibration signal generator and the event.

8. The signal generator of claim 7 further comprising a reference signal generator configured to generate the reference signal and output the reference signal to the driver for amplification.

9. The signal generator of claim 7 wherein the bias control circuit includes a feedback loop.

10. The signal generator of claim 7 further comprising a high speed image recording device configured to record the event.

11. The signal generator of claim 7 wherein the modulation signal source is configured as a precision frequency source when generating combs.

12. The signal generator of claim 7 wherein the modulation signal source is configured as a step generator when generating markers.

13. The signal generator of claim 7 wherein calibration comprises imposing a known time reference on the recorded image of the event.

14. A method for providing a known time reference on a recorded image of the event using an optic calibration signal to establish markers or combs, the method comprising:

generating an optic reference signal at a first frequency;

generating a modulation signal at a second frequency;

generating a bias signal for biasing a Mach-Zehnder modulator;

biasing the Mach-Zehnder modulator with the bias signal;

presenting the optic reference signal and the modulation signal to the Mach-Zehnder modulator;

generating the optic calibration signal at a third frequency with the Mach-Zehnder modulator;

triggering an event;

recording the event to create a recorded event image;

concurrent with recording the event, imposing the optic calibration signal on the recorded event image to establish a time reference or calibration for the recorded event.

15. The method of claim 14 wherein the optic calibration signal is a marker and the optic reference signal comprises an impulse or step generator signal.

16. The method of claim 14 wherein the optic calibration signal is a comb and the optic reference signal is generated by a precision frequency source capable of generating a frequency specific signal.

17. The method of claim 14 wherein generating an optic reference signal comprises presenting a reference signal from a controller to a driver, the driver amplifying the reference signal and then presenting the amplified reference signal to an optic signal generator to generate the optic reference signal.

18. The method of claim 17 wherein the optic signal generator comprises a laser diode.

19. The method of claim 14 wherein the event comprises a high speed event that is recorded over a duration of 10 nanoseconds or less.

20. The method of claim 14 wherein the optic reference signal is at a frequency of 10 GHz or greater.