CN102540281A - Wedge-shaped film in white-light interfering displacement sensor and manufacturing method thereof - Google Patents

Abstract

The invention discloses a wedge-shaped film in a white-light interfering displacement sensor and a manufacturing method thereof. According to the method, a better face type is obtained on a common optical substrate by using a stamping technology, a metal film of which the reflectivity is a certain value is plated on the substrate after being stamped, then the wedge-shaped film is manufactured on the metal film by the stamping technology, and the upper surface of the wedge-shaped film is plated with a semi-transparent and semi-reflective film with the design requirement so as to obtain a linear wedge-shaped film. According to the manufacturing method of the wedge-shaped film of which the thickness is in single linear change, which is disclosed by the invention, the problem of manufacturing of a wedge-shaped film of which the thickness is in the linear change of 5 to 50 microns in a sensor is solved, and a key technology is provided for researching and manufacturing the white-light interfering displacement sensor.

Description

A wedge-shaped film in a white light interference displacement sensor and its manufacturing method

technical field

The invention relates to the technical field of wedge-shaped membrane production, in particular to a wedge-shaped membrane in a white light interference displacement sensor and a manufacturing method thereof.

Background technique

Prior Art 1: A wedge-shaped film is fabricated by plating a dielectric film. The process of this method is as follows: firstly, a semi-transparent and semi-reflective film is coated on the optical substrate, then a wedge-shaped dielectric film is coated on the semi-transparent and semi-reflective film, and finally a layer of semi-transparent and semi-reflective film is coated on the dielectric film to form A wedge-shaped membrane in a Fizeau interferometer. The disadvantages of this method are: 1. It is difficult to control the dielectric film whose thickness varies linearly between 5 μm and 40 μm, and the success rate is low; 2. When the thicker dielectric film is taken out from the vacuum environment of the coating machine, it will Influenced by humidity and internal stress, it is easy to cause wrinkles and damage; 3. The equipment for plating dielectric film is expensive, and it takes more than 20 hours to plate a 40 μm dielectric film, and the production cost is relatively high.

Prior art 2: Utilize two optical substrates coated with a semi-transparent and semi-reflective film on one side, a spacer of about 40 μm is used at one end of the substrate, and the other end is in direct contact to form a wedge-shaped air gap. Although this method is simple, in order to ensure the linear relationship between the cavity length and position of the wedge-shaped cavity, the coating surfaces of the two optical substrates must have a good surface shape, and the thickness of the substrate is the basis for ensuring the surface shape, which increases Fizeau Spatial dimensions of the interferometer. At the same time, there are two surfaces in each Fizeau interferometer that require processing with a higher surface shape, which greatly increases the production cost.

At present, the technology of displacement measurement using white light interference displacement sensor can realize all-optical displacement measurement. The requirements for the wedge-shaped film are: wedge-shaped, the thickness change is linear, and the transmittance of the front and rear surfaces is in a certain ratio.

Working principle of white light interference displacement sensor:

As shown in Fig. 11, the wide-spectrum white light 8 enters the wedge-shaped film through one of the Y-shaped optical fibers 9, and after being reflected from the upper and lower surfaces of the wedge-shaped film 10 (connected to the object to be measured), the light with wavelength information passes through the Y-shaped optical fiber The other optical fiber in 9 is transmitted to the lens 11, after being collimated and expanded by the lens 11, it is uniformly irradiated on the wedge-shaped film 12, and a white light autocorrelation interference signal appears at a position equal to the thickness of the optical fiber incident on the wedge-shaped film 10 displacement, The signal is received by the CCD photosensitive element 13 behind the wedge-shaped film 12, and according to the position of the signal on the CCD, the spot position of the optical fiber incident on the wedge-shaped film 10 is judged, thereby performing displacement demodulation.

The purpose of the present invention is to solve the problem that the wedge-shaped cavity whose thickness varies linearly between 5 μm and 50 μm in the current white light interference displacement sensor is difficult to manufacture, the cost is high, or the space size of the optical elements forming the wedge-shaped cavity is too large. A method for manufacturing the wedge-shaped structure required in the white light interference displacement sensor by means of two copy imprints of organic materials.

Contents of the invention

In order to solve the above-mentioned problems in the manufacture of wedge-shaped membranes, the present invention proposes a method for preparing wedge-shaped membranes whose thickness varies linearly between 5 μm and 50 μm, which is suitable for white light interference displacement sensors.

The technical scheme adopted in the present invention is: a method for manufacturing a wedge-shaped film in a white light interference displacement sensor, the steps of which are as follows:

Step 1. Coat the optical substrate with SU8 glue, and the template with a release agent. Spin-coat SU8 glue on the optical substrate with a thickness of 2-3mm, the thickness of the glue is about 25μm, pre-bake at 65°C, bake for 10 minutes, then raise the temperature to 95°C, bake for 30-60 minutes; the surface shape is 1/10 The surface of the optical template with a wavelength (wavelength of 632.8nm) is coated with a release agent;

Step 2. Copy the surface of the template: imprint the template coated with the release agent on the optical substrate coated with SU8 glue, apply a certain pressure to ensure that the two are completely bonded, and heat it in a vacuum oven at a temperature of 100 ~ Between 120°C, the time is 2 to 3 hours;

Step 3, UV-cured SU8 glue: UV-cured SU8 glue between the template and the substrate, put the template and the substrate together into the oven again, and the post-baking temperature is between 95 and 120°C for 30 minutes. Cool to room temperature; then harden the film, raise the temperature of the oven to 150°C for 15 minutes, and cool to room temperature with the oven after drying;

Step 4, demolding and removing the release agent: after demoulding, use glow discharge ashing to remove the release agent on the SU8 surface on the substrate;

Step 5. Plating a semi-transparent and semi-reflective film: use a sputter coater to plate a chromium film on the surface of the cured SU8, with a thickness between 20-25nm;

Step 6. Apply SU8 glue on the surface of the chrome film, and apply release agent on the template: spin-coat SU8 on the surface of the chrome film with a thickness of about 50 μm, pre-bake at 65°C for 10 minutes, then raise the temperature to 100°C for 50-70 minutes; Apply a release agent to the surface of the optical template with 1/10 wavelength (wavelength is 632.8nm);

Step 7. Make steps by electroplating: clean the SU8 glue at one end, and electroplate steps of 30-50 μm;

Step 8. Embossing to form a wedge shape: emboss the template coated with the release agent on the surface of SU8 again, apply a certain pressure, and put it in a vacuum oven at a temperature of 100-120°C for 2-3 hours, then heat Keep the pressure constant during the process;

Step 9, UV-cured SU8 glue: UV-cured SU8 glue between the template and the chrome film, put the template and the substrate together in the oven again, and the post-baking temperature is between 95 and 120°C for 30 minutes;

Step 10, demoulding and removing the release agent: after demoulding, use glow discharge ashing to remove the release agent on the SU8 surface on the substrate;

Step 11, coating metal film: using a sputter coating machine to coat a metal film with a thickness between 2 and 6 nm;

Step 12, the wedge-shaped membrane is manufactured.

A wedge-shaped film in a white light interference displacement sensor is prepared by the above method.

Advantage and positive effect of the present invention:

1. Using the template replication technology, the optical substrate does not need to have a high surface shape requirement. It only needs to make the surface shape of the template 0.1 wavelength, and through the two-time embossing replication technology, the surface of the upper and lower surfaces of the wedge-shaped film The shape is consistent with the template, which ensures that the thickness of the wedge-shaped film changes linearly. At the same time, compared with the prior art 2, the processing cost of the optical substrate is reduced, the thickness of the substrate is reduced, that is, the space size of the wedge-shaped film in the Fizeau interferometer is reduced;

2. The commonly used organic material SU8 glue is used as the material in the middle of the wedge-shaped film, which replaces the method of plating the dielectric film in the prior art, greatly reduces the cost, and does not require special equipment for plating the dielectric film. After curing, the SU8 glue is in a glass state, which is less affected by temperature changes and can withstand high and low temperature changes.

Description of drawings

Figure 1 is coated with SU8 glue 2 on the optical substrate 1;

Figure 2 uses the template 3 coated with a mold release agent to imprint on the optical substrate 1 coated with SU8 glue 2, heat and UV cure, so that the surface shape of the SU8 glue is consistent with the surface shape of 3;

Figure 3 After the SU8 glue 2 is cured, the template 3 is separated, and the release agent remaining on the surface of the 2 is treated by ashing method;

Figure 4 sputters metal chromium film 4 on the surface of SU8 glue;

Figure 5 Spin-coat SU8 glue 5 on the surface of the chromium film again, with a thickness between 30 and 50 μm;

Figure 6 Remove the SU8 at one end, electroplating to form a step 6 of 30-50 μm, and emboss the SU8 glue 5 with the template 3 coated with a release agent again, apply a constant force on 3, and heat and cure at the same time;

Figure 7 After curing the SU8 glue 5, use ashing equipment to treat the surface of the SU8 glue 5 to remove the residual release agent;

Figure 8 is coated with a metal film (Au, Al, etc.) on the surface of SU8 glue 5;

Figure 9 cuts and removes the part without wedge-shaped membrane at the end, and the preparation is completed.

Fig. 10 is a flow chart of making wedge-shaped film in white light interference displacement sensor by embossing method.

Fig. 11 Schematic diagram of the working principle of the white light interference displacement sensor.

Detailed ways

Embodiment one:

Spin-coat SU8 glue on the BK7 optical glass with a thickness of 2mm and both sides are optical surfaces, with a thickness of 20μm. After pre-baking at 65°C for 10 minutes, heat up to 95°C for 40 minutes, as shown in Figure 1. The surface of the optical template whose surface type is 1/10 wavelength (wavelength is 632.8nm) is coated with a release agent.

Emboss the template coated with the release agent on the optical substrate coated with SU8 glue, apply a certain pressure to ensure that the two are completely bonded, and heat in a vacuum oven at 100°C for 2 hours, as shown in Figure 3 .

UV-cure the SU8 glue between the template and the substrate, and then put it into the oven at a temperature of 95-120°C for 30 minutes. After baking, cool to room temperature with the oven; then harden the film, and the temperature of the oven rises to 150°C. The time is 15 minutes, after drying, cool to room temperature with the oven.

After demoulding, use glow discharge ashing to remove the release agent on the SU8 surface on the substrate, as shown in Figure 3, use a sputter coater to plate a chromium film with a thickness of 20nm as shown in Figure 4.

Spin-coat SU8 on the surface of the chrome film on the substrate with a thickness of about 50 μm, pre-bake at 65°C for 10 minutes, then raise the temperature to 100°C for 60 minutes, as shown in Figure 5, and coat the mold release agent on the template.

Clean the SU8 glue at one end, electroplate the surface of the chromium film to form a step 6 of 30-50 μm, and imprint the template coated with the release agent on the surface of the SU8 again, apply a certain pressure, and put it in a vacuum oven at a temperature of 100°C , time 2 hours, keep the pressure constant during the heating process, as shown in Figure 6.

Use glow discharge ashing to remove the release agent on the surface of SU8 glue 5 on the substrate, as shown in Figure 7, and use a sputter coater to plate a gold film with a thickness of 4nm as shown in Figure 8.

Use a glass knife to cut and remove the top without the wedge-shaped film to obtain a wedge-shaped film for a white light interference displacement sensor. As shown in Figure 9.

Embodiment two:

On a quartz optical substrate with a thickness of 3 mm and both surfaces being optical surfaces, apply 30 μm of SU8 glue, pre-baking, embossing, demoulding, ashing, and chrome plating are the same as in Example 1; the second coating of SU8 glue, thickness After it is 45 μm, remove the SU8 glue at one end, and electroplate a step of 40 μm.

All the other are the same as the first embodiment.

Embodiment three:

Apply 20 μm SU8 glue on the optical substrate, pre-baking, embossing, demoulding, ashing, and chrome plating are the same as in Example 1; apply SU8 glue twice, after the thickness is 35 μm, remove the SU8 glue at one end, and electroplate 30 μm steps. The intermediate process is the same as the first embodiment, using glow discharge ashing to remove the release agent on the surface of the SU8 glue 5 on the substrate, as shown in Figure 7, removing the electroplating step 6, and plating an aluminum film with a thickness of 6nm, as shown in Figure 8.

All the other are the same as the first embodiment.

Claims (2)

1. the method for making of wedge film in the white light interference displacement transducer, it is characterized in that: the practical implementation step of this method is following:

Step 1, optical substrate are coated with SU8 glue, the template coating release agent.At thickness is spin coating SU8 glue on 2～3mm optical substrate, and the thickness of glue is about 25 μ m, and 65 ℃ of preceding bakings were toasted 10 minutes, were warming up to 95 ℃ then, toasted 30～60 minutes; The face type is the optics template surfaces coated release agent of 1/10 wavelength (wavelength is 632.8nm);

Step 2, duplicate template face type: the template that will scribble release agent is stamped on the optical substrate that scribbles SU8 glue, applies certain pressure, guarantees that the two fits fully, puts into the vacuum drying oven heating, temperature between 100～120 ℃, 2～3 hours time;

Step 3, ultra-violet curing SU8 glue: the SU8 glue between ultra-violet curing template and the substrate, put into baking oven once more, back baking temperature is between 95～120 ℃, the time is 30 minutes, has dried by the fire the back and has been cooled to room temperature with baking oven; Post bake then, oven temperature rises to 150 ℃, 15 minutes time, has dried by the fire with baking oven and is cooled to room temperature;

Step 4, the demoulding are also removed release agent: after the demoulding, utilize the glow discharge ashing to remove the release agent on SU8 surface on the substrate;

Step 5, plate semi-transparent semi-reflecting film: utilize the SU8 surface of sputter coating machine after curing to be coated with the chromium film, between thickness 20～25nm;

Step 6, chromium film surfaces coated SU8 glue, the template coating release agent: spin coating SU8 on chromium film surface, the about 50 μ m of thickness, 65 ℃ of preceding bakings 10 minutes are warming up to 100 ℃, 50～70 minutes then; In the face type is the optics template surfaces coated release agent of 1/10 wavelength (wavelength is 632.8nm);

Step is made in step 7, plating: the SU8 glue of an end is cleaned up, electroplate the step of 30～50 μ m;

Step 8, impression form wedge shape: the template that will scribble release agent once more is stamped in the SU8 surface, applies certain pressure, and puts into vacuum drying oven, and temperature is between 100～120 ℃, and 2～3 hours time, it is constant to keep-up pressure in the heating process;

Step 9, ultra-violet curing SU8 glue: the SU8 glue between ultra-violet curing template and the chromium film, put into baking oven once more, back baking temperature is between 95～120 ℃, the time is 30 minutes;

Step 10, the demoulding are also removed release agent: after the demoulding, utilize the glow discharge ashing to remove the release agent on SU8 surface on the substrate;

Step 11, metal-coated membrane: utilize the sputter coating machine to be coated with metal film, between thickness 2～6nm;

Step 12, wedge film complete.

2. wedge film in the white light interference displacement transducer, it is characterized in that: it adopts method for preparing to form.

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