CN105423911B - A kind of common railway digital holographic microphotography apparatus and method based on grating defocus - Google Patents

Abstract

The invention discloses a co-channel digital holographic microscopic device and method based on grating defocus. It includes a light source, an object to be measured, a microscopic objective lens, a correction objective lens, a first lens, a second lens, an image sensor and a computer, and also includes a one-dimensional periodic grating and an array of holes; the light beam emitted by the light source passes through the object to be measured, the microscopic objective lens and After correcting the objective lens, it enters the first lens, and the outgoing beam converged by the first lens is divided into 0-order diffracted light and +1-order diffracted light after passing through the one-dimensional periodic grating, and is filtered by the hole array to form reference light and object light, which are directed to the second The converging light beam transmitted by the second lens is received by the light receiving surface of the image sensor, and the image signal output end of the image sensor is connected to the image signal input end of the computer; the invention is simple and easy to adjust, and the size of the object to be measured is not large. Limited, make full use of the field of view of the detection window; it can greatly reduce the complexity of determining the system carrier frequency and improve the efficiency of the phase recovery algorithm.

Description

A co-channel digital holographic microscope device and method based on grating defocus

technical field

The invention belongs to the field of digital holographic detection, in particular to a co-channel digital holographic microscopic device and method based on grating defocus.

Background technique

Based on the principle of interference, digital holographic detection technology uses image sensors such as CCD or CMOS to record holographic (interferometric) images, and uses computers to digitally reproduce the surface topography of objects. The extremely important test and analysis methods are widely used in measurement fields such as biomedicine, micro-nano devices, and optical micro-processing. The traditional digital holography system uses Michelson, Mach-Zehnder and other separate optical path interference. The reference beam and measurement beam pass through different paths, which are easily affected by external vibrations and temperature fluctuations, and have poor anti-interference ability. Compared with the separate optical path structure, the common optical path structure has very good anti-interference ability because the reference beam and the measurement beam pass through the same path, so it has attracted extensive attention from domestic and foreign scholars in the past ten years.

G. Popescu et al. (G. Popescu, T. Ikeda, R. R. Dasari, M. S. Feld. Diffraction phase microscopy for quantifying cell structure and dynamics. Opt. Lett. 2006, 31, 775-777) of the Massachusetts Institute of Technology proposed a common path Point diffraction carrier holography technology, place a grating on the incident surface of the 4f optical system, divide the light wave diffraction through the object to be measured into multiple diffraction orders, and place a spatial hole array on the spectrum plane, select the zero-order light as the reference light and select + The first-order light is used as the object light, and then the carrier hologram is obtained through exposure acquisition. This technology has strong anti-interference ability due to the common path structure, but it has relatively high requirements for the matching between the center distance of the spatial pinhole filter array, the grating period, and the focal length of the lens. High, and precise adjustment is required to ensure an ideal hologram.

In order to improve the anti-interference ability of the system and simplify the system structure, the inventor proposed a series of dual-window common-path interference detection methods and devices based on grating defocus, such as ZL 201210424239.2 "Common-optical-path interference detection device and method based on synchronous carrier frequency phase shifting" , the incident surface of the 4f optical system is divided into two windows, one of which is used to place the object to be measured, and the other is used as a reference window, and a grating is placed at the frequency domain defocus of the 4f optical system to introduce the carrier, and then the carrier hologram is obtained , but because the incident surface is divided into two windows, not only the utilization rate of the detection window is only 1/2, but also the size of the object to be measured is limited.

Contents of the invention

The purpose of the present invention is to provide a simple, easy to adjust, common-path digital holographic microscopic device based on grating defocus. The object of the present invention also includes providing a co-channel digital holographic microscopy method based on grating defocus, which can reduce the complexity of determining the system carrier frequency and improve the efficiency of the phase recovery algorithm.

A co-channel digital holographic microscope device based on grating defocus, comprising a light source 1, an object to be measured 2, a microscope objective lens 3, a correction objective lens 4, a first lens 5, a second lens 8, an image sensor 9 and a computer 10, It also includes a one-dimensional periodic grating 6 and a hole array 7, where λ is the light wavelength of the light beam emitted by the light source 1;

The light beam emitted by the light source 1 enters the first lens 5 after passing through the object to be measured 2, the microscopic objective lens 3 and the correction objective lens 4, and the outgoing light beam converged by the first lens 5 passes through the one-dimensional periodic grating 6 and is divided into 0-order diffracted light and The +1st-order diffracted light is filtered by the hole array 7 to form reference light and object light, which are sent to the second lens 8, and the converging light beam transmitted by the second lens 8 is received by the light receiving surface of the image sensor 9, and the image signal of the image sensor 9 The output end is connected to the image signal input end of the computer 10;

The focal length of the first lens 5 is f ₁ , and the focal length of the second lens 9 is both f ₂ ;

The period of the one-dimensional periodic grating 6 is d, located at the back focus f ₁ -Δf of the first lens 5 and located at the front focus f ₂ +Δf of the second lens 8, where Δf is the defocus amount;

The hole array 7 contains large holes A and pinholes B with a center distance of Δfλd, the hole array 7 is located on the conjugate focal plane of the first lens 6 and the second lens 8, and the diameter of the pinhole B is ≤1.22f ₂ λD , D is the field of view width of the image sensor.

A co-channel digital holographic microscopic device based on grating defocus of the present invention also includes:

1. The one-dimensional periodic grating (6) is a binary one-dimensional periodic grating, a sine one-dimensional periodic grating or a cosine one-dimensional periodic grating.

2. The large hole A of the hole array (7) allows all the 0th-order diffracted light to pass through to form the object light, and the pinhole B allows the +1-order diffracted light to pass through to form the reference light.

Or: the large hole A allows all the +1 order diffracted light to pass through to form the object light, and the pinhole B allows the 0th order diffracted light to pass through to form the reference light.

A co-channel digital holographic microscopy method based on grating defocus, comprising the following steps,

Step 1: Adjust the light source so that the light beam emitted by the light source enters the first lens through the object to be measured, the microscopic objective lens and the correction objective lens, and the outgoing light beam converged by the first lens is directed to the one-dimensional periodic grating;

Step 2: The converging light beam passing through the one-dimensional periodic grating is divided into 0-order diffracted light and +1-order diffracted light, which are filtered by the hole array to form reference light and object light, which are sent to the second lens, and the converging beam transmitted by the second lens forms a picture The interferogram I is collected by the image sensor and processed by the computer;

Step 3: Calculate the complex amplitude c(x,y) of the object to be measured:

c(x,y)=IFT{FT{I(x,y)Rr(x,y)}·LF}

Among them, LF means low-pass filtering, FT means Fourier transform, IFT means inverse Fourier transform, Rr(x, y) is a digital reference wave,

Step 4: Obtain the complex amplitude of the object to be measured

Beneficial effect:

Device of the present invention has following salient features:

1. The device of the present invention has a simple structure, low system positioning complexity requirements, and convenient adjustment, and does not require any special optical elements such as polarization elements;

2. The device of the present invention adopts reflective point diffraction to form a common optical path structure, and the system has strong anti-interference ability and good stability.

The co-channel digital holographic microscopy method based on grating defocus has the following characteristics:

1. On the basis of the common channel structure, the grating defocusing spectroscopic technology and the hole array filtering technology are combined to obtain a carrier hologram through one exposure, which not only ensures the system interference capability and real-time detection, but also the method is simple and easy to adjust , and the size of the object to be measured is not limited, and the field of view of the detection window can be fully utilized, which is one of the innovations different from the existing technology;

2. The hologram carrier frequency mapping relationship is simple and easy to determine. It can be precisely controlled through the grating defocus, thereby greatly reducing the complexity of determining the system carrier frequency and improving the efficiency of the phase recovery algorithm. This is one of the innovations different from the existing technology two.

Description of drawings

Figure 1 is a schematic structural diagram of a co-channel digital holographic microscope device based on grating defocus;

Figure 2 is a schematic diagram of the hole array.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings.

The purpose of the present invention is to address the deficiencies of the prior art, combining grating defocus spectroscopic technology and hole array filtering technology, and propose a co-channel digital holographic microscopic device and method based on grating defocus.

The invention belongs to the field of digital holographic detection, in particular to a co-channel digital holographic microscopic device and method based on grating defocus. A co-channel digital holographic microscope device light source based on grating defocus, a microscope objective lens correction objective lens, a first lens, a one-dimensional periodic grating, an aperture array, a second lens, an image sensor and a computer. The invention is simple and easy to operate, easy to adjust, and the size of the object to be measured is not limited, and the field of view of the detection window is fully utilized; the carrier frequency mapping relationship of the hologram is simple, easy to determine, and can be precisely controlled by the defocus of the grating, which can greatly reduce the determination system. The complexity of the carrier frequency and improve the efficiency of the phase recovery algorithm.

Explanation of symbols in Fig. 1: light source 1, object to be measured 2, microscope objective lens 3, correction objective lens 4, first lens 5, one-dimensional periodic grating 6, hole array 7, second lens 8, image sensor 9, computer 10.

The invention includes a light source with a wavelength of λ, a collimated beam expander system, an object to be measured, a microscope objective lens, a correction objective lens, a first lens, a second lens, an image sensor and a computer. The device is also provided with a one-dimensional periodic grating and a hole array. The light beam emitted by the light source enters the first lens through the object to be measured, the microscopic objective lens and the correction objective lens. Array filtering forms reference light and object light to the second lens, and the converging light beam transmitted by the second lens is received by the light receiving surface of the image sensor, and the image signal output end of the image sensor is connected to the image signal input end of the computer; The focal length of the first lens is f ₁ , and the focal length of the second lens is f ₂ ; the period of the one-dimensional periodic grating is d, which is located at the back focus f ₁ -Δf of the first lens and at the front focus f ₂ of the second lens At +Δf, where Δf is the amount of defocus; the hole array contains a large hole A and a pinhole B with a center distance of Δfλ/d, which are located on the conjugate focal plane of the first lens and the second lens, where the pinhole B The diameter is ≤1.22f ₂ λ/D, where D is the field of view width of the image sensor.

The one-dimensional periodic grating is a binary one-dimensional periodic grating, a sine one-dimensional periodic grating or a cosine one-dimensional periodic grating.

The large hole A of the hole array allows all the 0th order diffracted light to pass through to form the object light, the pinhole B allows the +1st order diffracted light to pass through to form the reference light, or the large hole A allows all the +1st order diffracted light to pass through to form the object light, the pinhole B B Let the 0th-order diffracted light filter through to form the reference light.

A co-channel digital holographic microscopy method based on grating defocusing, comprising the steps of:

①. Adjust the light source so that the light beam emitted by the light source enters the first lens through the object to be measured, the microscopic objective lens and the correction objective lens, and the outgoing light beam converged by the first lens is directed to the one-dimensional periodic grating. Its characteristics are:

②. The converging light beam passing through the one-dimensional periodic grating is divided into 0-order diffracted light and +1-order diffracted light, which is filtered by the hole array to form reference light and object light, which are sent to the second lens, and the converging beam transmitted by the second lens forms an interference Fig. 1, is gathered into computer by image sensor and processed by computer;

③. Calculate the complex amplitude c(x,y) of the measured object:

c(x,y)=IFT{FT{I(x,y)Rr(x,y)}·LF}

Among them, LF means low-pass filtering, FT means Fourier transform, IFT means inverse Fourier transform, Rr(x, y) is a digital reference wave, which can be expressed as

④. Calculate the complex amplitude of the measured object

The implementation examples of the present invention will be described in detail below with reference to FIG. 1 and FIG. 2 .

The device of the present invention includes: a light source 1, an object to be measured 2, a microscope objective lens 3, a correction objective lens 4, a first lens 5, a one-dimensional periodic grating 6, an array of holes 7, a second lens 8, an image sensor 9, a computer 10, Wherein the light source 1 is a laser with a wavelength of 632.8nm; the focal lengths of the first lens 5 and the second lens 8 are 200mm; the grating period d=50 μm, the defocus amount Δf=150 μm; the center distance between the hole array large hole A and the pinhole B is 1.9mm, and the diameter of the pinhole B is ≤1.22f ₂ λ/D.

The specific implementation of the detection method of the present invention is as follows: the light beam emitted by the light source forms an expanded beam after passing through the collimated beam expander system, and the beam enters the first lens through the object to be measured, the microscopic objective lens and the correction objective lens, and passes through the first The outgoing light beam converged by the lens is directed to the one-dimensional periodic grating; the converged light beam passing through the one-dimensional periodic grating is divided into first-order diffracted light and +1-order diffracted light, which are filtered by the hole array to form reference light and object light, which are directed to the second lens, and passed through the first The combined light beams transmitted by the two lenses form an interferogram I, which is collected by the image sensor and processed by the computer.

Using a computer to calculate the complex amplitude c(x,y) of the measured object can be obtained

c(x,y)=IFT{FT{I(x,y)Rr(x,y)}·LF}

Among them, LF means low-pass filtering, FT means Fourier transform, IFT means inverse Fourier transform, Rr(x, y) is a digital reference wave, which can be expressed as

In order to obtain the complex amplitude of the object to be measured

Claims (4)

1. A co-channel digital holographic microscope device based on grating defocus, comprising a light source (1), an object to be measured (2), a microscopic objective lens (3), a correction objective lens (4), a first lens (5), Second lens (8), image sensor (9) and computer (10), are characterized in that: also comprise one-dimensional periodic grating (6) and hole array (7), wherein λ is the light wavelength of light source (1) emitting light beam ; The light beam emitted by the light source (1) enters the first lens (5) after passing through the object to be measured (2), the microscopic objective lens (3) and the correction objective lens (4), and the outgoing light beam converged by the first lens (5) passes through the The one-dimensional periodic grating (6) is divided into 0-order diffracted light and +1-order diffracted light, which is filtered by the hole array (7) to form reference light and object light, which are sent to the second lens (8) and transmitted through the second lens (8) After the converging beam is received by the light-receiving surface of the image sensor (9), the image signal output end of the image sensor (9) is connected to the image signal input end of the computer (10); The focal length of the first lens (5) is f1, and the focal length _of the _second lens (8) is both f2; The period of the one-dimensional periodic grating (6) is d, located at the back focus f ₁ -Δf of the first lens (5) and located at the front focus f ₂ +Δf of the second lens (8), where Δf is the amount of defocus ; The hole array (7) contains large holes A and pinholes B with a center distance of Δfλ/d, and the hole array (7) is located on the conjugate focal plane of the first lens (6) and the second lens (8), where the pinholes The diameter of the hole B is ≤1.22f ₂ λ/D, where D is the field width of the image sensor. 2. A co-channel digital holographic microscope device based on grating defocus according to claim 1, characterized in that: the one-dimensional periodic grating (6) is a binary one-dimensional periodic grating, a sinusoidal one-dimensional period grating or cosine 1D periodic grating. 3. A co-channel digital holographic microscope device based on grating defocus according to claim 1, characterized in that: the large hole A of the hole array (7) allows all the 0th-order diffracted light to pass through to form the object light , the pinhole B lets the +1 order diffracted light filter through to form the reference light, Or: the large hole A allows all the +1 order diffracted light to pass through to form the object light, and the pinhole B allows the 0th order diffracted light to pass through to form the reference light. 4. A microscopic method based on the co-channel digital holographic microscopic device based on grating defocus according to claim 1, characterized in that: comprising the following steps, Step 1: Adjust the light source so that the light beam emitted by the light source enters the first lens through the object to be measured, the microscopic objective lens and the correction objective lens, and the outgoing light beam converged by the first lens is directed to the one-dimensional periodic grating; Step 2: The converging light beam passing through the one-dimensional periodic grating is divided into 0-order diffracted light and +1-order diffracted light, which are filtered by the hole array to form reference light and object light, which are sent to the second lens, and the converging beam transmitted by the second lens forms a picture The interferogram I(x,y) is collected by the image sensor and processed by the computer; Step 3: Calculate the complex amplitude c(x,y) of the object to be measured: c(x,y)=IFT{FT{I(x,y)Rr(x,y)}·LF} Among them, LF means low-pass filtering, FT means Fourier transform, IFT means inverse Fourier transform, Rr(x, y) is a digital reference wave, <mrow><mi>R</mi><mi>r</mi><mrow><mo>(</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>)</mo></mrow><mo>=</mo><mi>exp</mi><mrow><mo>(</mo><mo>-</mo><mi>i</mi><mn>2</mn><mi>&amp;pi;</mi><mfrac><mrow><mi>&amp;Delta;</mi><mi>f</mi></mrow><mrow><msub><mi>df</mi><mn>1</mn></msub></mrow></mfrac><mi>x</mi><mo>)</mo></mrow><mo>;</mo></mrow> Step 4: Obtain the complex amplitude c(x,y) of the object to be measured: <mrow><mi>c</mi><mrow><mo>(</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>)</mo></mrow><mo>=</mo><mi>a</mi><mi>r</mi><mi>c</mi><mi>t</mi><mi>a</mi><mi>n</mi><mo>{</mo><mfrac><mrow><mi>Im</mi><mo>&amp;lsqb;</mo><mi>c</mi><mrow><mo>(</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>)</mo></mrow><mo>&amp;rsqb;</mo></mrow><mrow><mi>Re</mi><mo>&amp;lsqb;</mo><mi>c</mi><mrow><mo>(</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>)</mo></mrow><mo>&amp;rsqb;</mo></mrow></mfrac><mo>}</mo><mo>.</mo></mrow>