A method of phase-time domain ghost imaging

Abstract

The application discloses a phase time-domain ghost imaging method. The device uses light pulses generated by a non-coherent light source in a time domain as an imaging light source, divides the light pulses into two paths, and one path is used for acting on a to-be-measured time signal and is received by a photodiode. The time-domain signal is converted into a frequency-domain signal on the photodiode, a filter function is used to filter out a low-frequency part and reserve a high-frequency part, and the high-frequency part is converted into a time-domain signal to record light intensity information. The other path is used for recording a signal intensity waveform by another photodiode, and second-order correlation operation is performed on light intensities of the two photodiodes to obtain an image of phase modulation. The device is a phase time-domain ghost imaging device. The method and the device are simple, easy to modulate, and have application value in the field of optical imaging.

Description

Technical Field

[0001] This invention discloses a method for phase-temporal ghost imaging, which belongs to the field of optical imaging. Background Technology

[0002] Ghost imaging is a promising technique that utilizes indirect imaging. Its imaging structure typically requires two detectors: a single-pixel detector measures the total intensity signal after the light beam interacts with the object; the other, a multi-pixel detector, records the spatial intensity distribution of another light beam without any object information. By calculating the correlation between the intensity fluctuations of the two beams, an image of the target can be obtained.

[0003] Currently, only a few strategies have been proposed for ghost imaging of phase objects. This is because traditional ghost imaging algorithms can only obtain the square mode information of the target's transmission function and cannot directly image the phase of the target's transmission function.

[0004] Compared to spatial ghost imaging, temporal ghost imaging experimentally utilizes the temporally fluctuating beam emitted by a laser diode to replace the spatially fluctuating beam, and an ultrafast electro-optic modulator modulates the temporal intensity of the incident light field to replace the interaction between the spatial object and the light field. Through multiple measurements, correlation calculations are performed on the intensity waveforms between the fast detector in the reference optical path and the slow detector in the signal optical path, achieving high-quality reconstruction and recovery of the signal. However, current temporal ghost imaging cannot image purely phase-dependent objects, which severely hinders its development and application. Therefore, we propose a phase-temporal ghost imaging device that can perform temporal imaging of time-phase signals, fulfilling one of the urgent requirements for the development of free-space optical imaging. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a method for phase-temporal ghost imaging. This invention utilizes temporal ghost imaging to process the frequency domain and achieves imaging of the temporal phase-modulated waveform through high-pass filtering. The device used in this invention has fewer optical components and a simpler layout.

[0006] The technical solution to achieve the purpose of the invention is to provide a method for phase-temporal ghost imaging, comprising the following steps:

[0007] (1) Incoherent light sources in the time domain generate light pulses as imaging light sources;

[0008] (2) The optical pulse is split into two paths by a beam splitter: one path is the signal optical path, where the beam is scattered (multiplicative modulation) by the time signal to be measured O(t); the time signal to be measured O(t) is a bit sequence generated by an ultrafast electro-optic modulator driven by a pulse mode generator, and its function expression is O(t)=exp[iφ(t)], where φ(t) is the phase variable; the signal light after interacting with the time signal to be measured O(t) is received by a photodiode D1 and integrated over time; the other path is the reference optical path, where the beam is directly received by another photodiode D2 and the signal intensity waveform is recorded in real time; both detectors D1 and D2 can distinguish the temporal structure of the optical signal;

[0009] (3) The pulsed light field on photodiode D2 is E(t), and the intensity of the light it receives is denoted as I2(t), where I2(t) = |E(t)| 2 The light intensity received by photodiode D1 is denoted as I1(t), where I1(t) = ∫dt|E(t)O(t)| 2 ;

[0010] (4) In order to image the time signal O(t) to be measured, the light intensity received by photodiode D1 needs to be processed. First, the time domain signal received by D1 is converted into a frequency domain signal. The time signals received by D1 and D2 are obtained simultaneously. Then, the low-frequency part of the D1 signal is filtered out using the filter function P(t), and the high-frequency part is retained. The signal is then converted from the frequency domain to the time domain, thereby obtaining the light intensity.

[0011]

[0012] P(t) is a high-pass filter function;

[0013] (5) Perform a second-order correlation operation on the light intensities received by D1 and D2.

[0014]

[0015] The image g of the time-domain phase modulation waveform O(t) can then be obtained. (2) (t); the correlation function g (2) (t) is the second derivative of the phase function of the time signal O(t), i.e. This refers to taking the derivative of the function φ(t) with respect to its independent variable t twice.

[0016] The beneficial effects of this invention are:

[0017] 1. The time-domain ghost imaging method can image time-domain phase-modulated waveforms;

[0018] 2. This invention can modulate the imaging speed according to the rate of change of the time-domain phase modulation waveform to obtain the best imaging effect;

[0019] 3. The device used in this invention has a simple optical path structure, is easy to adjust, has low manufacturing cost, is easy to implement, and is highly practical, making it valuable for applications in fields such as optical imaging and detection. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a phase-temporal ghost imaging method provided in an embodiment of the present invention.

[0021] Figure 2 This is a time signal O(t) to be measured provided in an embodiment of the present invention;

[0022] In the diagram, 1: light source; 2: beam splitter; 3: time signal to be measured; 4: D1 photodiode; 5: D2 photodiode; 6: computer; 7: correlator. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the embodiments. The following embodiments are explanations of the present invention and are also preferred application forms of the present invention, but the present invention is not limited to the following embodiments.

[0024] like Figure 1 The diagram shown illustrates the structure of a phase-temporal ghost imaging method provided in this embodiment. It includes: 1: a light source; 2: a beam splitter; 3: the time signal to be measured; 4: a D1 photodiode; 5: a D2 photodiode; 6: a computer; and 7: a correlator. (Combined with...) Figure 1 The working steps of this embodiment are as follows:

[0025] (1) An incoherent light source 1 in the time domain generates light pulses as an imaging light source;

[0026] (2) The optical pulse is split into two paths by beam splitter 2: one path is the signal optical path, where the beam is scattered (multiplicative modulation) by the time signal to be measured 3; the time signal to be measured O(t) is a bit sequence generated by an ultrafast electro-optic modulator driven by a pulse mode generator, and its function expression is O(t)=exp[iφ(t)]; the signal light after interacting with the time signal to be measured O(t) is received by a D1 photodiode 4 and integrated over time; the other path is the reference optical path, where the beam is directly received by another D2 photodiode 5 and the signal intensity waveform is recorded in real time; detectors D1 and D2 can both distinguish the temporal structure of the optical signal;

[0027] (3) The pulsed light field on photodiode D2 is E(t), and the intensity of the light it receives is denoted as I2(t), where I2(t) = |E(t)| 2The light intensity received by photodiode D1 is denoted as I1(t), where I1(t) = ∫dt|E(t)O(t)| 2 ;

[0028] (4) In order to achieve imaging of the time signal O(t) to be measured, the light intensity received by photodiode D1 needs to be processed by computer 6. First, the time domain signal received by D1 is converted into a frequency domain signal. The time signals received by D1 and D2 are obtained simultaneously. Then, the low-frequency part of the D1 signal is filtered out using the filter function P(t), and the high-frequency part is retained. Then, the signal is converted from the frequency domain to the time domain, thereby obtaining the light intensity.

[0029]

[0030] P(t) is a high-pass filter function;

[0031] (5) Perform a second-order correlation operation on the light intensities received by D1 and D2 at correlator 7.

[0032]

[0033] The image g of the time-domain phase modulation waveform O(t) can then be obtained. (2) (t); the correlation function g (2) (t) is the second derivative of the phase function of the time signal O(t), i.e.

Claims

1. A method for phase-temporal ghost imaging, Its features include the following steps: (A) Incoherent light sources in the time domain generate light pulses as imaging light sources; (B) The optical pulse is split into two paths by a beam splitter: one path is the signal optical path, where the beam is scattered (multiplicative modulation) by the time signal to be measured O(t); the time signal to be measured O(t) is a bit sequence generated by an ultrafast electro-optic modulator driven by a pulse mode generator, and its function expression is O(t) = exp[iφ(t)]; the signal light after interacting with the time signal to be measured O(t) is received by a photodiode D1 and integrated over time; the other path is the reference optical path, where the beam is directly received by another photodiode D2, and the signal intensity waveform is recorded in real time; both detectors D1 and D2 can distinguish the temporal structure of the optical signal; (C) The pulsed light field on photodiode D2 is E(t), and the intensity of the light it receives is denoted as I2(t), where I2(t) = |E(t)| 2 The light intensity received by photodiode D1 is denoted as I1(t), where I1(t) = ∫dt|E(t)O(t)| 2 ; (D) To image the time signal O(t) to be measured, the light intensity received by photodiode D1 needs to be processed. First, the time-domain signal received by D1 is converted into a frequency-domain signal. The time signals received by D1 and D2 are obtained simultaneously. Then, the low-frequency part of the D1 signal is filtered out using the filter function P(t), while the high-frequency part is retained. Finally, the signal is converted from the frequency domain to the time domain, thereby obtaining the light intensity. P(t) is a high-pass filter function; (E) Perform a second-order correlation operation on the light intensities received by D1 and D2. The image g of the time-domain phase modulation waveform O(t) can then be obtained. (2) (t); the correlation function g (2) (t) is the second derivative of the phase function of the time signal O(t), i.e.

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