DEVICE AND METHOD FOR CHARACTERISING THE ROUGHNESS PROFILE OF A TISSUE SAMPLE

Abstract

The invention describes a device (1) for characterizing the rough profile of a tissue sample comprising: a laser source (2) that illuminates the surface (100) of the tissue; a photodetector (3) that receives the light backscattered by the surface (100) of the tissue; and further a displacement means (4) configured to alternate between a first position wherein a rotating ground glass (5) is disposed within the path of the laser beam towards the surface (100), a second position wherein a rotating half wave blade (6) is disposed within the path of the laser beam towards the surface (100); and a third position wherein within the path of the laser beam towards the surface (100) neither the ground glass plate (5) nor the half wave blade (6) are arranged, or the half wave blade (6) is arranged in a fixed non-rotating position.

Claims

1. A device for characterizing the rough profile of a tissue sample, comprising: a laser source that illuminates the surface of the tissue with a continuous wave laser beam; and a photodetector that receives the light scattered in reflection by the surface of the tissue illuminated by the laser beam; characterized in that it further comprises a displacement means configured to alternate between: a first position wherein a rotating ground glass plate (5) is disposed within the path of the laser beam towards the surface; a second position wherein a rotating half wave blade is disposed within the path of the laser beam towards the surface; and a third position wherein neither the ground glass plate nor the half wave blade are arranged within the path of the laser beam towards the surface, or the half wave blade in a fixed non-rotating position.

2. The device according to claim 1, wherein the displacement means comprises: a guide arranged in front of the laser source perpendicular to the emitted laser beam; a frame movable along the guide, the ground glass plate and the half wave blade being coupled to said frame; a translation motor that moves the frame along the guide to selectively place the ground glass plate, the half wave blade in the path of the laser beam, or none of them; and a rotation motor coupled to the ground glass plate and the half wave blade to rotate respectively the ground glass plate and the half wave blade when they are in front of the laser source.

3. The device according to claim 2, wherein the ground glass plate is fixed to a first toothed wheel and the half wave blade is fixed to a second toothed wheel, and wherein the rotation motor is coupled to said first and second toothed wheels to rotate them.

4. The device according to claim 1, further comprising optical light conducting means that conduct the laser beam from the laser source towards the surface of the tissue and the light scattered in reflection by the surface of the tissue towards the photodetector.

5. The device according to claim 4, wherein the optical light conducting means comprises mirrors, lenses and beam splitters.

6. The device according to claim 4, wherein the optical light conducting means comprise an optical fiber housed in an endoscope.

7. The device according to claim 1, further comprising a processing means that receives the signal obtained by the photodetector in response to the light reflected in received dispersion and calculates useful parameters for characterizing the rough profile of the surface.

8. The device according to claim 1, which has a wavelength of less than 635 nm.

9. The device according to claim 1, coupled to a microscope.

10. A procedure for determining the roughness frequency of a surface using the device of claim 1, comprising the following steps: arranging the displacement means so that the ground glass plate is located within the path of the laser beam towards the surface at the same time as it rotates; emitting a laser beam which, after passing through the rotating ground glass plate, falls on the surface; receiving the light scattered in reflection by the surface during a complete rotation of the ground glass plate; determining the roughness frequency (ρ.sub.θ) from the received light intensity (I) and the angle of rotation (θ) of the ground glass plate using the following formula: ${\rho }_{\theta }^{-1}\sim \frac{-\ln \left(C_{ro\mathrm{ughness}}\left(\theta \right)\right)}{\theta }$ $\mathrm{wherein}$ $C_{ro\mathrm{ughness}}\left(\theta \right)\approx \frac{.Math.I\left(\theta =0\right).Math.I\left(\theta \right).Math.}{.Math.{I\left(\theta =0\right)}^2.Math.}-1$

11. A procedure for determining the degree of depolarization of a surface using the device of claim 1, comprising the following steps: arranging the displacement means so that the half wave blade is located within the path of the laser beam towards the surface at the same time as it rotates; emitting a laser beam which, after passing through the rotating half wave blade, falls on the surface; receiving the light scattered in reflection by the surface during a complete rotation of the half wave blade; determining the degree of depolarization (δP.sub.θ.sup.−1) from the received light intensity (I) and the angle of rotation (θ) of the half wave blade using the following formula: $\delta P_{\theta }^{-1}\sim \left(\frac{-\ln \left(C_{\mathrm{polarization}}\left({\theta }_p\right)\right)}{{\theta }_p}\right)$ $\mathrm{wherein}$ $C_{\mathrm{polarization}}\left({\theta }_p\right)\approx \frac{(I\left({\theta }_p=0\right).Math.I\left({\theta }_p\right).Math.}{.Math.{I\left({\theta }_p=0\right)}^2.Math.}-1$

12. A procedure for determining the average speed of the dispersive components of a fabric using the device of claim 1, comprising the following steps: arranging the displacement means so that in the path of the laser beam towards the surface there is none of the half wave blade and the ground glass plate, or the half wave blade is located in a fixed non-rotating position; emitting a laser beam which falls on the surface; receiving the light scattered in reflection by the surface during a time interval; determining the average speed of the dispersive components (v.sub.dynamic) of the surface from the received light intensity (I) and time (t) using the following formula: $.Math.v_{\mathrm{dynamic}}.Math.\sim \left(\frac{-\ln \left(C_{\mathrm{dynamic}}\left(t\right)\right)}{t}\right)$ $\mathrm{wherein}$ $C_{\mathrm{dynamic}}\left(t\right)\approx \frac{.Math.I\left(0\right).Math.I\left(r\right).Math.}{.Math.{I\left(0\right)}^2.Math.}-1.$

Description

BRIEF DESCRIPTION OF THE FIGURES

[0063] FIG. 1 shows a simplified diagram of the device according to the present invention.

[0064] FIG. 2 shows a perspective view of an example of displacement means according to the present invention.

[0065] FIG. 3 shows a front view of the example of displacement means according to the present invention.

[0066] FIG. 4 shows a rear view of the example of displacement means according to the present invention.

[0067] FIG. 5 shows a schematic view of the system of the invention implemented for a microscope.

[0068] FIG. 6 shows a schematic view of the system of the invention implemented for an endoscope.

PREFERRED EMBODIMENT OF THE INVENTION

[0069] The present invention will now be described with reference to the accompanying figures, which show various exemplary configurations of devices for characterizing the roughness profile of a tissue sample.

General Description

[0070] FIG. 1 shows a simplified diagram of the device (1) of the present invention wherein the most important components have been represented. A laser source (2), which in this example is a 635 nm continuous wave laser, emits a laser beam directed towards the surface (100) of the tissue to be studied. Within the path of the laser beam towards the surface (100), a displacement means (4) is interposed that has at least one ground glass plate (5) and a half wave blade (6). The displacement means (4) can alternate between a first position wherein the laser beam passes through the ground glass plate (5), a second position wherein the laser beam passes through the half wave blade (6), and a third position wherein the laser beam does not pass through any of the two. That is, in the third position, the laser beam is not affected by its passage through the displacement means (4).

[0071] The laser beam continues its path, passing through a beam splitter (71) until it falls on the surface (100). The reflected light is diffuse due to the scattering phenomenon produced in the light wave due to the roughness of the sample. As a consequence, light is reflected according to multiple angles instead of just one. Part of this scattered light in reflection hits the beam splitter (71) again and is directed towards a photodetector (3). The signal from the photodetector (3) is subsequently directed towards a processing means (not shown in the figures), wherein it is analyzed according to the procedures described previously in this document.

[0072] FIGS. 2 to 5 show in greater detail an example of displacement means (4). In this configuration, the displacement means (4) comprises a guide (41) that takes the form of a threaded cylindrical rod arranged essentially perpendicularly in front of the laser source (2). A frame (42) is slidably coupled to the guide (41) so that it can slide along it from one end to the other. In this example, the frame (42) has two aligned holes through which the guide (41) passes. A translation motor (43) coupled to one end of the guide (41) causes rotation in one direction or another. Thus, when the guide (41) rotates around its own axis, the thread forces the frame (42) to move along it in one direction or another.

[0073] On the frame (42) there is arranged a body to which two gears are rotatably fixed: a first toothed wheel (51) provided with a central hole in which a ground glass (5) is fixed; and a second toothed wheel (61) provided with a central hole in which a half wave blade (6) is fixed. Thus, when the first or second toothed wheels (51, 61) rotate relative to the frame body (42), the ground glass (5) also rotates or the corresponding half wave blade (6). Both the first and second toothed wheels (51, 61) are coupled to a drive toothed wheel (46) through a further intermediate toothed wheel (45). The drive toothed wheel (46) is driven by a rotation motor (44). Thus, when the rotation motor (44) rotates, the rotation of the toothed wheel (46) rotates the intermediate toothed wheel (45) which, in turn, causes the rotation of the first and second toothed wheels (51, 61).

[0074] Thus, the operation of this displacement means (4) is as follows. Depending on the analysis procedure of the surface (100) to be carried out, the ground glass plate (5), the half wave blade (6), or neither of the two, is arranged in the path of the laser beam towards the surface (100). To do this, the translation motor (43) is activated until the desired element is placed in front of the laser source (2). Next, or at the same time, if necessary, the rotation motor (44) is activated to cause the rotation of the ground glass plate (5) or the half wave blade (6).

[0075] Example for Microscope

[0076] FIG. 5 shows an example of a system (1) according to the present invention that can be configured for use in combination with a microscope (200). In this example, the displacement means (4) is arranged according to the first position, that is, with the ground glass plate (5) arranged in front of the laser source (2), and with a rotation motor (44) working. Thus, the laser beam passes through the rotating ground glass plate (5). The laser beam then passes through a beam splitter (71) and onto a dichroic filter (72) that reflects wavelengths above 620 nm and transmits wavelengths between 400 nm and 620 nm. The 635 nm laser beam is therefore reflected by the dichroic filter (72) and continues to a second beam splitter (73), which reflects it and sends it to a mirror (75), which finally orients it in parallel to the microscope objective (200). The laser beam falls on the surface (100), and the backscattered light follows the reverse path, passing through the mirror (75) and the beam splitter (73) and the dichroic filter (72) until it reaches the beam splitter (71), which reflects it towards the photodetector (3). Subsequently, through a processing means that is not shown in the figures, the analysis of the light intensity received by the photodetector (3) is carried out to obtain the described parameters.

[0077] The system shown in FIG. 5 further includes a series of additional elements, such as a spectrometer (11), a white light source (12) and collimators (13, 14). These elements are related to a series of measurements that are carried out in this system outside the object of the present invention, and therefore their operation is not described in detail here.

[0078] Example for Fiber Optics

[0079] FIG. 6 shows another example of a system (1) according to the present invention, although in this case designed for use with an optical fiber (87). This configuration would be useful, for example, by arranging the optical fiber in an endoscope, which would allow the analysis of surfaces located inside a patient in-vivo. In this example, the displacement means (4) is also arranged in the first position, that is, with the ground glass plate (5) arranged in front of the laser source (2), and with the rotation motor (44) in operation. The laser beam thus passes through the beam splitter (81) and reaches a dichroic filter (82) that reflects wavelengths above 620 nm and transmits wavelengths between 400 nm and 620 nm. The laser beam is thus directed into an optical fiber (87) that will take it to the study surface (100) inside the patient. The light backscattered by the surface (100) will return along the same path until it reaches the beam splitter (81), which in this case will reflect it, directing it towards the photodetector (3). Subsequently, through a processing means that is not shown in the figures, the analysis of the light intensity received by the photodetector (3) is carried out to obtain the described parameters.

[0080] This system (1) further includes, as in the previous case, a spectrometer (11) and a collimator (14), used to carry out measurements outside the object of the present invention.

[0081] Analysis Procedures

[0082] The three procedures for obtaining surface characteristics described in this document are described below.

[0083] 1. Speckle Interferometry Correlation Measurements

[0084] The speckle interferometry correlation measurements are made by making the laser beam pass through the ground glass (5) at the same time that it rotates, which will cause changes in the lighting pattern on the sample. The light intensity data backscattered by the sample is collected by the photodetector (3) and analyzed by the processing means so that the correlation of the light reflected by the sample when illuminated by the different patterns produced by the rotating glass is obtained. This correlation is related to the roughness of the surface: on very smooth surfaces the correlation will hold even for large angles of rotation, while on very rough surfaces the correlation will be lost even for small angles of rotation.

[0085] The correlation is calculated according to the following equation, wherein θ represents the angle of rotation of the ground glass and I(θ) is the light intensity received by the photodetector.

[00004]$C_{ro\mathrm{ughness}}\left(\theta \right)\approx \frac{.Math.I\left(\theta =0\right).Math.I\left(\theta \right).Math.}{.Math.{I\left(\theta =0\right)}^2.Math.}-1$

[0086] The degree of roughness is calculated by adjusting −ln(c.sub.roughness(θ)) as a function of the angle θ, the slope of which is inversely related to the rate of variation of surface roughness. The parameter finally obtained is the “roughness frequency” (ρ.sub.θ).

[00005]${\rho }_{\theta }^{-1}\sim \frac{-\ln \left(C_{ro\mathrm{ughness}}\left(\theta \right)\right)}{\theta }$

[0087] 2. Depolarization Correlation Measurements

[0088] The depolarization correlation measurements are made by making the laser beam pass through the half wave blade (6) at the same time that it rotates. In this way, the incident electromagnetic field is rotated to later compare it with other previous positions of the half wave blade. This measurement offers very useful information on the degree of anisotropy of the fabric, since it compares the different states of polarization of the transmitted and reflected beam. Measurements are taken angularly for one full rotation of the half wave blade. Once performed, the autocorrelation of the measured intensity is calculated as a function of the angle of rotation (θ) of the half wave blade (6).

[00006]$C_{\mathrm{polarization}}\left(\theta \right)\approx \frac{(I\left(\theta =0\right).Math.I\left(\theta \right).Math.}{.Math.{I\left(\theta =0\right)}^2.Math.}-1$

[0089] To obtain information on the level of depolarization, an adjustment of −ln(c.sub.polarization(θ)) is made as a function of the angle of rotation (θ) of the half wave blade. The slope of this fit is inversely proportional to the depolarization of the sample. This parameter is called the “degree of depolarization” (δP.sub.θ).

[00007]$\delta P_{\theta }^{-1}\sim \left(\frac{-\ln \left(C_{\mathrm{polarization}}\left(\theta \right)\right)}{\theta }\right)$

[0090] It should be noted that, in the case of implementation as a module for an endoscope, the optical fiber used will be multimode, which implies that the polarization can vary uncontrollably when crossing the fiber. However, this variation will have the same autocorrelation when rotating the incident polarization. Therefore, these measurements are not equivalent to the polarization measurements that have typically been made with single-mode fibers with maintained polarization, although equivalent quantitative results are obtained when performing autocorrelation.

[0091] 3. Temporal Correlation Measurements

[0092] Temporal correlation measurements are made by ensuring that the laser beam that reaches the surface of the tissue has optical characteristics that are invariant over time. To do this, a first possibility consists of moving both the ground glass plate (5) and the half wave blade (6) out of the path of the laser beam. Alternatively, it is possible to place the half wave blade (6) in the path of the laser beam as long as it remains stationary. This possibility can be useful for applications with space problems, since in this case the displacement means (4) only requires two positions. Temporal correlation measurements allow in-vivo dynamic information to be obtained, such as cell motility and blood flow. For this, the temporal autocorrelation of the intensity (I) measured as a function of time (t) is performed.

[00008]$C_{\mathrm{dynamic}}\left(t\right)\approx \frac{.Math.I\left(0\right).Math.I\left(r\right).Math.}{.Math.{I\left(0\right)}^2.Math.}-1$

[0093] Then, using the slope of the curve resulting from the adjustment of −ln(c.sub.dynamic(t) as a function of time, the parameter that measures the average speed of the dispersive components of the tissue is obtained (v.sub.dynamic).

[00009]$.Math.v_{\mathrm{dynamic}}.Math.\sim \left(\frac{-\ln \left(C_{\mathrm{dynamic}}\left(t\right)\right)}{t}\right)$

[0094] The joint measurement of the parameters measured thanks to the device (1) of the present invention will allow the creation of multidimensional maps of the dispersion of the analyzed tissue sample that will provide a large amount of information on its morphological and dynamic characteristics in the face of various applications.