REFRACTIVE INDEX DISTRIBUTION STANDARD

Abstract

Refractive index distribution standard in the form of a three-dimensional object which contains in its volume a base medium and regions of variable size and distance with a refractive index other than that of the base medium, characterised in that the difference between the refractive index of said regions and the refractive index of the base medium is not greater than 0.04, at least one of the regions is a set of at least two prisms or cylinders or coaxial rings of variable size and distance, having a dimension in at least one direction similar to the resolving power of the measurement system under assessment and at least one of the regions is sphere-like or ellipsoid-like in shape.

Claims

1. A refractive index distribution standard in the form of a three-dimensional object comprising in its volume a base medium and regions of variable size and distance with a refractive index different than that of the base medium, characterised in that the difference between the refractive index of said regions and the refractive index of the base medium is not greater than 0.04, at least one of the regions is a set of at least two prisms or cylinders or coaxial rings of variable size and distance, having a dimension in at least one direction similar to the resolving power of the measurement system under assessment and at least one of the regions is ellipsoid-like or sphere-like in shape.

2. The standard according to claim 1 characterised in that at least one sphere-like or ellipsoid-like region is located within another region with a different refractive index relative to the ellipsoid-like or sphere-like region and relative to the base medium.

3. The standard according to claim 1 characterised in that the region in the form of coaxial rings contains rings with a diameter ranging from 1 pm to 50 pm, with a thickness of each of the rings close to the resolving power of the measurement system to be evaluated.

4. The standard according to claim 1 characterised in that it contains a set of at least two cuboids arranged parallel to each other.

5. The standard according to claim 1 characterised in that it contains a set of prisms arranged in relation to each other similar as in a Siemens star.

6. The standard according to claim 1 characterised in that at least one of the regions has a gradient-based variation in the refractive index, with a maximum refractive index variation range of 0.02.

7. The standard according to claim 6 characterised in that a region with a gradient change in the refractive index has the shape of a cuboid or cylinder.

8. The standard according to claim 1 characterised in that it has external dimensions ranging from 5 pm to 300 pm in each of the three directions.

9. The standard according to claim 1 characterised in that each of the internal regions of the standard with a different refractive index has dimensions in the range from 50 nm to 250 pm in each of the three directions.

10. The standard according to claim 1 characterised in that the differences in refractive indices of individual regions range from 0.001 to 0.04.

11. The standard according to claim 1 characterised in that the values of the refractive index of the standard material range from 1.45 to 1.60.

12. The standard according to claim 1 characterised in that it has a shape similar to truncated ellipsoid.

13. The standard according to claim 1 characterised in that standard represents a biological cell or a colony of cells.

Description

[0036] The standard according to the invention is shown in the exemplary embodiments in the drawing, where:

[0037] FIG. 1 is a standard according to the first embodiment including cross-sections,

[0038] FIG. 2 is a standard according to the second embodiment including cross-sections,

[0039] FIG. 3 is a standard according to the third embodiment including cross-sections,

[0040] FIG. 4 is a standard according to the fourth embodiment.

[0041] The standards according to the invention were made by the two-photon polymerization technique using the Photonics Professional GT (Nanoscribe GmbH) device, characterised by the following parameters: ×100 1.4 NA microscopic lens, positioning of the beam focus in relation to the photoresist by means of a 3-axis piezoelectric stage, femtosecond fibre laser (pulse duration 100 fs, pulse repetition rate 80 MHz, central wavelength: 780 nm); printing of subsequent layers of the structure occurs towards the lens.

Example 1

[0042] The standard shown in FIG. 1 has the shape of a truncated ellipsoid 30×25×11 μm in size (length, width, height). Base material 1 has a refractive index of 1.52. Within the standard's volume there are the following features: [0043] region 2 with a refractive index of 1.50 and a size of 9×6×6 μm, [0044] three ellipsoidal inclusions 3 distributed within region 2 with a refractive index of 1.52 and sizes from 2 to 4 μm, [0045] region 4 in the shape of a set of cuboids with a refractive index of 1.48 and size 4×1.5× from 0.3 to 0.7 μm, spaced at 0.6 to 1.4 μm, [0046] region 5 in the shape of a set of cuboids with a refractive index of 1.48 and size 4×1.5× from 0.3 to 0.7 μm, spaced at 0.6 to 1.4 μm, [0047] region 6 in the shape of a set of cuboids with a refractive index of 1.48 and size 3×3× from 0.8 to 1.4 μm, spaced at 1.5 to 2 μm, [0048] region 7 with gradient-based changes in the refractive index, varying from 1.50 to 1.52 and with a size of 4.5×4.5×3 μm.

[0049] Regions 4, 5 and 6 are resolution tests for directions X (5), Y (4) and Z (6).

[0050] The standard shown in FIG. 1 was obtained from the material that is commercially available under the name IP-L 780 (Nanoscribe GmbH).

[0051] The standard shown in FIG. 1 was obtained as follows: [0052] 1. A drop of IP-L 780 polymer was applied to the centre of the 170 μm thick, high-precision coverslip, which was then placed in the holder of the 3D printing device using the two-photon polymerisation method. [0053] 2. After focusing the optical system of the device on the glass-polymer interface, the line by line and layer by layer manufacturing procedure was started in accordance with the numerical definition of the structure, which consists of successive points in the coordinate system of the device as well as local and global process parameters. [0054] 3. Performance characteristics of the standard are primarily affected by the following process parameters: power of the polymerizing laser, scanning rate and spacing between subsequent voxels, lines, and layers. The indicated refractive index values have been achieved for the following set of parameters: average laser power of 0 mW for regions with a refractive index of 1.48, 13 mW for regions with a refractive index of 1.50, and 20 mW for regions with a refractive index of 1.52, scanning velocity of 70 μm/s, distance between voxels of 200 nm in the XY plane (plane of the glass-polymer interface) and 300 nm in the Z direction (along the axis of the optical system of the device). Analogous standard regions with refractive indices of 1.50 and 1.52 can be obtained for example with a constant laser power of 18 mW and a variable scanning velocity ranging from 150 to 50 μm/s, respectively. [0055] 4. At the end of the printing process, the coverslip with the structure was cleaned from the excess uncured polymer by submersion in isopropyl alcohol bath for 15 minutes.

Example 2

[0056] The standard shown in FIG. 2 has the shape of a truncated ellipsoid 60×50×15 μm in size. Base material 1 has a refractive index of 1.50. Within the standard's volume there are the following features: [0057] seven ellipsoidal regions 2 with a refractive index of 1.52 and a size of 1 to 10 μm, [0058] region 3 in the shape of 4 coaxial rings with diameters between 5 and 8 μm, thickness between 0.3 and 1 μm and a refractive index of 1.52, [0059] region 4 in the shape of a set of cuboids with a refractive index of 1.48 and size 6×6× from 1.5 to 3 μm, spaced at 3 to 5 μm. [0060] region 5 in the shape of a cuboid with dimensions of 12×10×4 μm and with gradient-based changes in refractive index values ranging from 1.50 to 1.52.

[0061] Regions 3 and 4 are resolution tests for directions X (3), Y (3) and Z (4).

Example 3

[0062] The standard shown in FIG. 3 has the shape of a truncated ellipsoid 30×25×11 μm in size. Base medium 1 has a refractive index of 1.52. Within the standard's volume there are the following features: [0063] region 2 in the shape of a set of cuboids with a refractive index of 1.48 and size 3×3× from 0.8 to 1.5 μm, spaced at 2 to 2.5 μm, [0064] region 3 in the shape of an ellipsoid with dimensions of 18×18×8 μm and a refractive index of 1.51, with regions 4 and 5 within it, [0065] region 4 in the shape of 2 ellipsoids with a refractive index of 1.50 and sizes in the range of 0, 5 to 4 μm, [0066] region 5 in the shape of prisms 2×5×4 μm in size, arranged in relation to each other like a Siemens star, with a refractive index of 1.50.

[0067] Regions 2 and 5 are resolution tests for directions X (5), Y (5) and Z (2).

Example 4

[0068] The standard shown in FIG. 4 is composed of three standard presented in Example 1, fabricated side by side and overlapping, similar to a cell colony.