Refractometer and method for measuring refractive index
View Patent ↗A refractometer and a method for measuring refractive index is disclosed. The refractometer comprises a light source, a reflecting module, a lens module, an array sensor, and a processor, wherein the reflecting module is configured to receive optical beams from the light source, the reflecting module comprises a detection surface configured to totally reflect at least part of the optical beams; the lens module is configured to converge optical beams from the detection surface onto a focal plane of the lens module; and the array sensor is located on the focal plane of the lens module.
1 . A refractometer, comprising:
one or more processors;
an array sensor;
a light source configured to emit a light beam;
a reflecting module configured to reflect a portion of the light beam from the light source, the reflecting module comprising a prism having a first surface and at least one medium disposed on the first surface, wherein a detection area configured to hold a liquid to be detected is disposed on the first surface or on one of the at least one medium; and
a lens module configured to converge the reflected light beam from the reflecting module onto the array sensor, wherein the array sensor is located on the focal plane of the lens module and is configured to detect the received light beam and generate a detection image;
wherein a portion of light incident on a first interface which locates between two adjacent media is totally internally reflected toward the lens module, and is then converged onto the array sensor, thereby forming a first strip-shaped area with a distinct brightness discontinuity in the detection image for self-calibration; wherein the two adjacent media are two media among the prism and the at least one medium;
wherein when a refractive index of the liquid to be detected is less than that of the medium adjacent to the liquid, a portion of light incident on a second interface which locates between the liquid to be detected and the medium adjacent to the liquid is totally internally reflected toward the lens module, and is then converged onto the array sensor, thereby forming a second strip-shaped area with a distinct brightness discontinuity in the detection image; and
wherein the one or more processors are configured to identify the first strip-shaped area and the second strip-shaped area and derive the refractive index of the liquid to be detected based on the positions of the first strip-shaped area and the second strip-shaped area.
2 . The refractometer of claim 1 , wherein the detection area and the medium with a smaller refractive index among the two adjacent media are separately arranged on the first surface-or on one of the at least one medium, or
wherein the detection area and the medium with a smaller refractive index among the two adjacent media are stacked on the first surface or on one of the at least one medium, with said medium disposed therebetween; and the second portion of the light beam passes through the prism and said medium before being incident on the liquid to be detected.
3 . The refractometer of claim 2 , wherein the at least one medium comprises a cured material layer and a transparent glass layer disposed between the detection area and the first surface;
wherein the transparent glass layer is configured to seal the cured material layer and the prism within the refractometer, and the detection area is located on a side of the transparent glass layer facing away from the cured material layer, and
wherein the-two adjacent media among the prism and the at least one medium are the cured material layer and the prism, or the transparent glass layer and the cured material layer.
4 . The refractometer of claim 3 , wherein a refractive index of the prism is greater than that of the cured material layer, and a refractive index of the cured material layer is greater than that of the transparent glass layer, and
wherein a position of the array sensor is configured to avoid a position where a light beam totally reflected by the transparent glass layer is converged by the lens module, thereby preventing a third strip-shaped area with distinct brightness discontinuity from appearing in the detection image.
5 . The refractometer of claim 3 , wherein the cured material layer is cured UV adhesive.
6 . The refractometer of claim 2 , wherein the prism further has a light incident surface and a light exit surface,
wherein the light incident surface is provided with an inlet for allowing entrance of the light beam,
wherein the light exit surface is provided with an outlet for allowing exit of the reflected-light beam, or is provided with a first outlet for allowing exit of the reflected first portion of the light beam by the second medium and a second outlet for allowing exit of the reflected second portion of the light beam.
7 . The refractometer of claim 1 , wherein the detection image comprises a first edge and a second edge opposite to the first edge, and the first edge corresponds to a higher refractive index than the second edge, and
wherein the first strip-shaped area is located in the detection image between the first edge and a strip-shaped area corresponding to a maximum refractive index within a measurement range of the refractometer.
8 . The refractometer of claim 1 , wherein the array sensor is configured to generate one or more detection images,
wherein at least one detection image has pixels with different exposure parameters, or at least one detection image is applied with an exposure parameter different from that of another detection image, or
wherein light beams from the light source have different luminous intensities for at least two detection images, respectively.
9 . The refractometer of claim 1 , wherein an aperture of a light-emitting surface of the light source and an aperture of the lens module are the same, or have a difference less than 1/5 of the aperture of the lens module, or
wherein an aperture of a light-emitting surface of the light source is greater than twice the aperture of the lens module.
10 . The refractometer of claim 1 , wherein a full width at half maximum of the light beam from the light source is less than 5 nm, or
wherein an optical path of the light beam is equipped with a narrowband filter, and a full width at half maximum of light beam filtered by the narrowband filter is less than 5 nm.
11 . The refractometer of claim 1 , wherein the one or more processors are configured to perform noise filtering on a target pixel row in the detection image based on at least a portion of an upper pixel row and at least a portion of a lower pixel row of the target pixel row before identifying the first strip-shaped area and the second strip-shaped area.
12 . The refractometer of claim 11 , wherein a filtered pixel in the target pixel row is obtained through noise filtering based on a weighted average of at least one pixel in the target pixel row, at least one pixel in the upper pixel row and at least one pixel in the lower pixel row.
13 . The refractometer of claim 12 , wherein the one or more processors are configured to identify pixels affected by stray light in the detection image, and exclude the identified affected pixels when deriving the refractive index of the liquid to be detected, and
wherein the pixels affected by stray light are identified by comparing brightness between multiple pixel rows and/or comparing brightness between multiple detection images.
14 . The refractometer of claim 1 , wherein the array sensor is configured to generate one or more initial detection images by detecting the received light beam, and the detection image is obtained based on a weighted summation of two or more of the initial detection images.
15 . The refractometer of claim 1 , wherein the one or more processors are configured to obtain the blurriness of the first strip-shaped area and the second strip-shaped area, respectively, and derive the turbidity of the liquid to be detected based on the blurriness of the first strip-shaped area and the second strip-shaped area.
16 . The refractometer of claim 1 , further comprising a first temperature sensor and a second temperature sensor;
wherein the first temperature sensor is in contact with the medium with a smaller refractive index among the two adjacent media to detect a temperature of said medium; and
wherein the second temperature sensor is disposed on the detection area to measure a temperature of the liquid to be detected.
17 . The refractometer of claim 16 , wherein a relationship model among the temperature of liquid to be detected, the temperature of the medium with a smaller refractive index among the two adjacent media and the refractive index of liquid to be detected is stored in the refractometer; and
wherein the one or more processors are configured to derive the refractive index of the liquid to be detected based on the temperatures obtained by the first temperature sensor, the temperatures obtained by the second temperature sensor, and the relationship model.
18 . The refractometer of claim 1 , wherein at least one of the following is adjusted to adjust the quality of the detection image: the light intensity of the light source, the exposure time of the array sensor, the analog gain of the array sensor, or the digital gain of the array sensor.
19 . The refractometer of claim 1 , wherein the refractive index of the medium with a smaller refractive index among the two adjacent media is greater than 1.33 and not greater than 1.6, and has a variation of no greater than 0.0003 per degree Celsius of temperature change.
20 . A method for measuring a refractive index, comprising:
emitting, by a light source, a light beam to a reflecting module;
reflecting, by the reflecting module, a portion of the light beam from the light source to a lens module, the reflecting module including a prism having a first surface and at least one medium disposed on the first surface, wherein a detection area is disposed on the first surface or on one of the at least one medium, the detection area being configured to hold a liquid to be detected;
converging, by the lens module, the reflected light beam by the reflecting module onto an array sensor located on the focal plane of the lens module,
generating, by the array sensor, a detection image from the received light beam;
wherein a portion of light incident on a first interface which locates between two adjacent media is totally internally reflected toward the lens module, and is then converged onto the array sensor, thereby forming a first strip-shaped area with a distinct brightness discontinuity in the detection image for self-calibration; wherein the two adjacent media are two media among the prism and the at least one medium;
wherein when a refractive index of the liquid to be detected is less than that of the medium adjacent to the liquid, a portion of light incident on a second interface which locates between the liquid to be detected and the medium adjacent to the liquid is totally internally reflected toward the lens module, and is then converged onto the array sensor, thereby forming a second strip-shaped area with a distinct brightness discontinuity in the detection image; and
further comprising:
identifying, by one or more processors, the first strip-shaped area and the second strip-shaped area in the detection image,
deriving, by the one or more processors, the refractive index of the liquid to be detected based on the positions of the first strip-shaped area and the second strip-shaped area.