Built-in compact near-infrared on-line detection system of integrating sphere
[ technical field ] A method for producing a semiconductor device
The invention belongs to the technical field of spectral information measurement, and particularly relates to a compact near-infrared online detection system with an integrating sphere arranged inside.
[ background of the invention ]
The near infrared spectrum measurement is widely applied, but the absorption is weak and the sensitivity is low. Therefore, different methods are invented in the prior art to improve the signal-to-noise ratio and improve the measurement sensitivity.
The invention patent application CN201910503942.4 discloses an active non-contact high-flux diffuse reflection optical fiber probe device for measuring near infrared spectrum, although the characteristics of large area, high flux, strong spectrum signal and the like of a region for collecting reflected light are stated, a light guide light path is based on optical fiber design, the diameter of a common optical fiber is 200-300 microns, and the diameter of a quartz optical fiber can be 10mm, even though the quartz glass optical fiber is compared with a light engine based on space optics with the size of 100mm, the luminous flux is two orders of magnitude lower, and the common optical fiber is two orders of magnitude lower, so the luminous flux is relatively low. Reflecting the influence of the signal-to-noise ratio, the actual influence on the signal-to-noise ratio is at least one order of magnitude more than that because the light intensity distribution may be uneven or the light has different divergence angles. In this case, the light spot emitted by collimated illumination is larger in area according to the author's description, and the light intensity is weaker. In addition, the light engine also comprises a movable device for providing a calibration light path of background reference light, and the stability, accuracy and inter-platform difference of the instrument cannot be guaranteed.
The patent US5406084A designs a space optics-based light engine, which has a built-in high-speed rotating wheel and a brisk sphere (integrating photometer), and a sample window is attached to the lower end of the integrating sphere, directly isolating the instrument and the sample. This allows part of the specularly reflected light to enter the integrating sphere and mix in the effective signal, affecting the signal-to-noise ratio. The presence of the moving wheel also reduces the stability of the instrument in long-term use, prolonging the time required for a single sample.
Patent CN206601328 adopts a mode that a transmitting optical fiber is arranged in the center, five collecting optical fibers are wrapped around the transmitting optical fiber, the outer sides of the five collecting optical fibers are arranged in a regular hexagon and a circle of transmitting optical fibers is arranged, and so on, to design a probe. Such a compact probe structure would allow a significant amount of specular light to enter the collection fiber bundle unless the probe is immersed or in close proximity to the sample, thus limiting the range of applications for near infrared spectrometers.
Therefore, there is a need to provide a new compact near-infrared online detection system with an integrated sphere built-in to solve the above problems.
[ summary of the invention ]
The invention mainly aims to provide a compact near-infrared online detection system with an integrating sphere, which has a compact structure, can effectively avoid specular reflection light, adaptively adjust an effective irradiation range, and extract effective light intensity to the maximum extent, so that the sensitivity and the signal-to-noise ratio of the system are remarkably improved.
The invention realizes the purpose through the following technical scheme: a compact near-infrared online detection system with a built-in integrating sphere comprises a light source, a reflection cover, the reflection cover, an integrating sphere, a light collector and a spectrum detector, wherein the reflection cover is used for reflecting light emitted by the light source to form a columnar light beam with a set diffusion angle, the integrating sphere is arranged in the path of the columnar light beam, the light collector is positioned right below the integrating sphere, the spectrum detector is connected with the integrating sphere through an optical fiber, the columnar light beam is emitted onto the surface of a sample through a light emitting window, and diffuse reflection light generated on the surface of the sample enters the integrating sphere after passing through the light collector.
Furthermore, the device also comprises a shell which surrounds the reflector to form a hollow cavity, the integrating sphere and the light collector are arranged in the hollow cavity, and the light outlet window is arranged at one end of the shell.
Furthermore, the integrating sphere is provided with a first opening for the diffuse reflection light to enter and form signal light, a second opening for part of the columnar light beam to enter and form reference light, a third opening for connecting with a calibration light source inside the spectrum detector and a fourth opening for connecting with the spectrum detector.
Further, the fourth opening is an SMA95 optical fiber interface and is connected with the spectral detector through an optical fiber.
Further, the third opening is an SMA95 optical fiber interface, and is connected to a calibration light source through an optical fiber.
Further, the first opening, the second opening, and the third opening are respectively provided with a first shutter, a second shutter, and a third shutter.
Furthermore, the light collector is a concave-convex lens and is positioned right below the first opening.
Further, the signal-to-noise ratio can be improved by at least one order of magnitude by adjusting the working distance or the focal distance, and the diameter D of a light spot formed on the surface of the sample is as follows:
wherein: mu is the object distance, i.e. the distance from the light collector to the signal collection opening of the integrating sphere, WdF is the focal length of the collector and is negative, working distance.
Compared with the prior art, the compact near-infrared online detection system with the built-in integrating sphere has the beneficial effects that: the integrating sphere is skillfully placed under a light source, and through the design of a small diffusion angle, specular reflection light is effectively avoided, the range of effective light spots is effectively expanded, the effective light spots basically coincide with visible light spots, and further the effective light intensity is improved by at least one order of magnitude, so that the system sensitivity is improved, and the signal-to-noise ratio is improved; the scheme has compact integral structure and small occupied space, can realize on-line near infrared spectrum detection, and greatly improves the application range; the scheme also provides an irradiation area according to actual needs, and the working distance W is adjusteddOr the focal length f, to transmit the effective diffuse reflection light into the system with the maximum efficiency, so that the method adaptively solves the problems of poor signal-to-noise ratio, strong light intensity, weak effective light intensity, poor sensitivity and the like in the prior art.
[ description of the drawings ]
Fig. 1 is a schematic structural diagram of an embodiment of the present invention.
[ detailed description ] embodiments
Example (b):
referring to fig. 1, the present embodiment is a compact near-infrared online detection system 100 with a built-in integrating sphere, which includes a light source 10, a reflector 11, a housing 16 surrounding the reflector 11 to form a hollow cavity 15, an integrating sphere 20 disposed in the hollow cavity 15, and a light collector 14, wherein an end of the housing 16 is formed with a light exit window 13. The integrating sphere 20 is provided with four openings, which are a first opening 21, a second opening 23, a third opening 25, and a fourth opening 27, wherein the first opening 21, the second opening 23, and the third opening 25 are respectively provided with a first shutter 22, a second shutter 24, and a third shutter 26. The first opening 21 is arranged towards the light exit window 13 and the third opening 25 is arranged horizontally outwards. The light collector 14 is located directly below the first opening 21.
The fourth opening 27 may be an SMA95 optical fiber interface connected to the spectral detector 30 by an optical fiber 31 for measuring spectral data. The third opening 25 is controlled to open and close by a third shutter 26, and the third shutter 26 is connected to a calibration light source 33, such as a xenon lamp or other calibration light source, via an optical fiber 32 connected to the SMA95 optical fiber interface, for performing the necessary calibration of wavelength or spectral line shape.
The second opening 23 forms an openable and closable opening through the second shutter 24, and allows part of the light from the light source 10 to enter the integrating sphere 20 to provide measurement data of the reference light. The first opening 21 forms an openable and closable opening in conjunction with the first shutter 22, and receives the signal light.
Since it is known that a large portion of stray light in the signal path affecting the signal is caused by specular reflection, this embodiment provides a slight diffusion angle of about 6 degrees through the reflector 11, as shown in fig. 1, since the middle of the light path is blocked by the integrating sphere 20, the light can only exit from the periphery, and the exit direction is slightly outward divergent. This ensures that none of the specularly reflected light impinging on the sample surface enters the signal path, i.e. the specularly reflected light does not enter the first opening 21. The present embodiment provides a light collection method to achieve the same effect. In this embodiment, a new diffusion type manner is adopted, and the light collector 14 is combined to expand the effective region to the whole visible light spot region PQ, so that the method is different from the existing scheme, although the visible light spot may be made large enough, the area which can really enter the signal collection region is very limited, the visible light spot and the effective light spot are perfectly fused, and the effective signal intensity is greatly improved.
The collector 14 is an optical device that spreads the light, such as a single concave lens or a double concave lens, an example of which is shown in FIG. 1. The collector 14 may also be a set of optics that serve the purpose of directing the light in the PQ region into the first opening 21.
The focal length of the concave lens collector 14 is f negative and the resulting virtual image is negative, assuming an object distance μ, the following relationship is satisfied:
where v is the image distance. Referring to the relation of similar triangles in FIG. 1, there are
Wherein WdThe working distance is D, the diameter of an area shielded by the integrating sphere in a light spot area on the working surface is D, the diameter of the light spot on the working surface is D, and by combining the formula (2) and the formula (3), the following can be deduced:
the object distance μ is a determined value, i.e. the distance of the first opening 21 of the integrating sphere 20 to the center point of the light collector 14, if the working distance WdIs also determined, usually by manufacturer's recommended working distance WdThe ratio D/D is a function of the image distance v only, whereas according to equation (1) the ratio D/D is a function of the focal distance f only. d represents the size of the shaded portion covered by the integrating sphere, WdIf yes, d is the determined value. The effective illumination range is a function of the focal length. From the above derivation, we can adjust the effective spot size by selecting the focal length, note that f is negative, and the spot diameter D is:
in practical application, we determine D according to the surface area of the sample to be irradiated, and back derive the required f. Or if f is fixed in the instrument, the working distance W can be adjusteddThe desired ideal illumination range D is obtained.
For example, if a user measures an apple, the user can estimate the required irradiation range according to the average size of the apple, and the system is arranged to effectively measure the component information required to be measured in the apple. If the watermelon is measured, the irradiation area can be several times larger than that of the apple, and system parameters such as working distance or focal length can be set correspondingly, so that effective measurement is realized.
The working principle of the compact near-infrared online detection system 100 with the built-in integrating sphere in the embodiment is as follows: light emitted by the light source 10 is reflected into diffused light which is circularly distributed and has a diffusion angle with a set angle through the reflector 11, and then is emitted out through the light outlet window 13 and is irradiated on the surface of a sample; wherein a portion of the diffused light enters integrating sphere 20 from second opening 23 to provide measurement data of the reference light; the light impinging on the surface of the sample is diffusely reflected, collected at the first opening 21 by the light collector 14, and enters the integrating sphere 20 to provide signal light for measurement.
The compact near-infrared online detection system 100 with the built-in integrating sphere has the advantages that: the integrating sphere is arranged in a shell, a light source and a reflecting cover are arranged in the shell, light of the light source is reflected into a light beam with a set diffusion angle by the reflecting cover, the light beam passes through the integrating sphere and then hits the surface of a sample, a light collector is arranged below a signal light inlet of the integrating sphere, diffuse reflection light generated on the surface of the sample is converged at the signal light inlet, then the signal light is accessed into the integrating sphere to form signal light, meanwhile, the diffuse light beam passes through the integrating sphere, reference light is collected through the reference light inlet of the integrating sphere, and then a spectrum detector connected with the integrating sphere through an optical fiber is used for spectrum measurement and analysis; the scheme has compact integral structure and occupies spaceThe method is small, can realize on-line near infrared spectrum detection, and greatly improves the application range; the scheme improves the effective irradiation area by times, thereby improving the signal-to-noise ratio and the sensitivity; the scheme also provides an irradiation area according to actual needs by adjusting the working distance WdOr the focal length f, to transmit the effective diffuse reflection light into the system with the maximum efficiency, so that the method adaptively solves the problems of poor signal-to-noise ratio, strong light intensity, weak effective light intensity, poor sensitivity and the like in the prior art.
What has been described above are merely some embodiments of the present invention. It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the inventive concept thereof, and these changes and modifications can be made without departing from the spirit and scope of the invention.