Patent Publication Number: US-2023152207-A1

Title: Optical imaging system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 110142179, filed on Nov. 12, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to an optical system, and more particularly to an optical imaging system. 
     Description of Related Art 
     Requirements for application of fluid sample inspection take place in various fields, such as the biomedical and pharmaceutical industry, the semiconductor industry, the environmental engineering industry, and the like. Fluid image observers may be used to observe and photograph the information of samples flowing in a flow channel. However, the existing fluid image observers, with depth of field becoming shallower as magnification increases, are prone to cause images of the samples in the flow channel to be clear only on a focusing plane, and the samples not on the focusing plane can merely be presented by blurred images, which leads statistical data of sample analysis to be inaccurate. 
     SUMMARY 
     The disclosure provides an optical imaging system that may make an image of a particle in a flow channel clearer and may enable the information of the particle in the flow channel to be counted and analyzed more accurately. 
     An embodiment of the disclosure provides an optical imaging system adapted for presenting an image of a particle. The optical imaging system includes a collimated light source, a flow channel, and a telecentric lens. The collimated light source is adapted for emitting a parallel beam. The flow channel is arranged on the transmission path of the parallel beam and is adapted for allowing the particle to pass through. The telecentric lens is arranged on the transmission path of the parallel beam. The parallel beam passes through the flow channel before transmitted to the telecentric lens, and the telecentric lens is adapted for converging the parallel beam onto an imaging plane. 
     The optical imaging system in the embodiments of the disclosure, with the collimated light source and the telecentric lens, projects the parallel beam onto the flow channel and makes the parallel beam pass through the flow channel before imaged by the telecentric lens, which may improve the depth of field of the optical imaging system and make the image of the particle in the flow channel clearer. In addition, the optical imaging system of the disclosure may further reduce the impact of particle positions on image magnification, which enables the information of the particle in the flow channel to be counted and analyzed more accurately. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an optical imaging system according to an embodiment of the disclosure. 
         FIG.  2    is a partial schematic diagram of the optical imaging system according to the embodiment in  FIG.  1   . 
         FIG.  3    is a schematic diagram of a collimated light source according to an embodiment of the disclosure. 
         FIG.  4    is a schematic diagram of a collimated light source according to another embodiment of the disclosure. 
         FIG.  5    is a schematic diagram of a collimated light source according to an embodiment of the disclosure. 
         FIG.  6 A  is a schematic diagram of particles and a parallel beam according to an embodiment of the disclosure. 
         FIG.  6 B  is a schematic diagram of particle images according to the embodiment of  FIG.  6 A . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
       FIG.  1    is a schematic diagram of an optical imaging system according to an embodiment of the disclosure.  FIG.  2    is a partial schematic diagram of the optical imaging system according to the embodiment in  FIG.  1   . With reference to  FIG.  1    and  FIG.  2   , an optical imaging system  1  of the disclosure is adapted for presenting an image of a particle P in a flow channel  20 . The particle P may be mixed in fluid L. In some embodiments, the particle P is a sample to be tested, such as bacteria, a semiconductor particle, particles of various materials, or the like. In another some embodiments, the particle P and the fluid L together serve as the sample to be tested, such as blood, industrial wastewater, various solutions, or the like, but the disclosure is not limited thereto. In this embodiment, the optical imaging system  1  includes a collimated light source  10 , the flow channel  20 , and a telecentric lens  30 . The collimated light source  10  is adapted for emitting a parallel beam I. The parallel beam I refers to a beam whose waveform is substantially a plane wave and whose wavefront plane is substantially orthogonal to the direction in which the beam travels. The embodiments of the disclosure use the parallel beam I to irradiate the particle P to reduce diffraction and obtain a clearer image. 
     From another point of view, the parallel beam I in the embodiments of the disclosure may include substantially parallel beams whose beam angle θ ranges from −5 degrees to 5 degrees. The beam angle of the parallel beam I, defined according to the meaning known to those skilled in the art, refers to an included angle formed by two boundary lines where beam intensity is 50% of that at a beam centerline as viewed from a tangent plane through an optical axis.  FIG.  3    is a schematic diagram of a collimated light source according to an embodiment of the disclosure.  FIG.  4    is a schematic diagram of a collimated light source according to another embodiment of the disclosure. With reference to  FIG.  3   , in this embodiment, a collimated light source  10   a  is adapted for emitting the parallel beam I with the beam angle θ of 5 degrees, and two boundary lines of the parallel beam I (as shown in  FIG.  3   ) form an included angle of 5 degrees. With reference to  FIG.  4   , in this embodiment, a collimated light source  10   b  is adapted for emitting the parallel beam I with the beam angle θ of −5 degrees, and two boundary lines of the parallel beam I (as shown in  FIG.  4   ) form an included angle of −5 degrees. 
     With reference to  FIG.  1    and  FIG.  2    again, the flow channel  20  is adapted for allowing the particle P to pass through. In detail, the flow channel  20  is adapted for allowing the mixture of the fluid L and the particle P to flow from an end  20 A of the flow channel  20  to an end  20 B of the flow channel  20 . In some embodiments, the size of the particle P ranges from 1 micrometer to 100 micrometers, but the disclosure is not limited thereto. In some embodiments, the flow channel  20  may be a micro flow channel. For example, an inner diameter R 1  of the flow channel  20  may range from 0.1 millimeter to 1 millimeter, but the disclosure is not limited thereto. The flow channel  20  may be arranged on a microfluidic chip  22 , but the disclosure is not limited thereto. 
     The flow channel  20  is arranged on the transmission path of the parallel beam I. The flow channel  20  may be made of a light-transmitting material, such that the parallel beam I may pass through the wall of the flow channel  20  and the fluid L in the flow channel  20  to be transmitted to the telecentric lens  30 . The disclosure does not limit the types and light transmittance of the light-transmitting material. In some embodiments, the flow channel  20  and the collimated light source  10   b  are arranged to make the included angle between the parallel beam I and the flow channel  20  fall within a range from −5 degrees to 5 degrees, and the included angle may be defined by the beam centerline of the parallel beam I and the centerline of the flow channel  20 . In this embodiment, the parallel beam I is substantially orthogonal to the flow channel  20 . In other words, the beam centerline of the parallel beam I may be substantially orthogonal to the centerline of the flow channel  20  to obtain a better image. 
     In some embodiments, the collimated light source  10  and the flow channel  20  are arranged to make a distance D 1  between the collimated light source  10  and the flow channel  20  fall within a range from 100 millimeters to 500 millimeters, but the disclosure is not limited thereto. A beam diameter RL of the parallel beam I at the flow channel  20  may be greater than the inner diameter of the flow channel  20 . In this case, the parallel beam I may provide sufficient illumination for the particle P flowing through the flow channel  20 . The beam diameter may be defined according to the meaning known to those skilled in the art to refer to, for example, a spot diameter at where light intensity is 1/e 2  of peak intensity. In some embodiments, the beam diameter RL of the parallel beam I at the flow channel  20  ranges from 10 millimeters to 80 millimeters to provide more homogeneous illumination, but the disclosure is not limited thereto. 
     The telecentric lens  30  is arranged on the transmission path of the parallel beam I. After passing through the flow channel  20  and the fluid L in the flow channel  20 , the parallel beam I is transmitted to the telecentric lens  30 . The telecentric lens  30  is adapted for converging and imaging the parallel beam I onto an imaging plane IP after the parallel beam I passes through the flow channel  20 . Therefore, the image of the particle P may be presented on the imaging plane IP. The telecentric lens  30  has a depth of field D. In some embodiments, the flow channel  20  and the telecentric lens  30  are configured for the portion of the flow channel  20  irradiated by the parallel beam I to be located within the depth of field D of the telecentric lens  30 . With this configuration, all the particles P passing through the flow channel  20  may be presented by clear images on the imaging plane IP. Generally speaking, the telecentric lens  30  may have the greater depth of field D to provide clearer images. In some embodiments, the effective focal length of the telecentric lens  30  may range from 144 micrometers to 216 micrometers, but the disclosure is not limited thereto. 
     In this embodiment, the optical imaging system  1  may further include a fluid pump  40  and a containing cavity  42 . The containing cavity  42  is in fluid communication with the flow channel  20 . The containing cavity  42  contains the fluid L and the particle P to be tested. The fluid pump  40  is connected with the containing cavity  42  and is adapted for driving the fluid L, such that the mixture of the fluid L and the particle P flows from the containing cavity  42  to the flow channel  20 , and the fluid L and the particle P pass through the flow channel  20 . The fluid pump  40  may be a mechanical micro pump or a non-mechanical micro pump, but the disclosure is not limited thereto. In some embodiments, with the fluid pump  40  in cooperation with the flow channel  20 , the flow rate of the fluid L ranges from 0.3 ml/min to 3 ml/min, but the disclosure is not limited thereto. 
     In this embodiment, the optical imaging system  1  may further include a circular polarizer  50 . The circular polarizer  50  may include a quarter-wave plate and a linear polarizer. In this embodiment, the circular polarizer  50  is arranged on the transmission path of the parallel beam I, and the circular polarizer  50  may be arranged between the flow channel  20  and the telecentric lens  30 , such that the parallel beam I is transmitted to the telecentric lens  30  through the circular polarizer  50  after passing through the flow channel  20 . The quarter-wave plate may be, for example, arranged between the linear polarizer and the telecentric lens  30 . The circular polarizer  50  may filter out some stray light (such as ambient light reflected by the wall of the flow channel  20 ) to reduce the impact of the ambient light and improve image quality. 
     In this embodiment, the optical imaging system  1  may further include an image sensing apparatus  60 , arranged on the imaging plane IP. The image sensing apparatus  60  may include a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). The image sensing apparatus  60  may further convert the image of the particle P on the imaging plane IP to an electronic signal. 
       FIG.  5    is a schematic diagram of a collimated light source according to an embodiment of the disclosure. With reference to  FIG.  5   , in this embodiment, the collimated light source  10  includes a point light source  12  and a collimated lens  14 . The point light source  12  may include one or more high-power light-emitting diode devices, but the disclosure is not limited thereto. As shown in  FIG.  5   , in this embodiment, the point light source  12  may emit a divergent beam I′. The collimated lens  14  may be a single convex lens or a combination of multiple lenses. A distance D 2  between the point light source  12  and the collimated lens  14  may be configured to be substantially the same as an effective focal length f of the collimated lens  14 , such that the divergent beam I′ emitted by the point light source  12  may be collimated by the collimated lens  14  to obtain the parallel beam I. 
       FIG.  6 A  is a schematic diagram of particles and a parallel beam according to an embodiment of the disclosure.  FIG.  6 B  is a schematic diagram of particle images according to the embodiment of  FIG.  6 A . With reference to  FIG.  6 A  and  FIG.  6 B , as shown in  FIG.  6 A , a first particle P 1  and a second particle P 2  pass through the portion of the flow channel  20  irradiated by the parallel beam I. The first particle P 1  is located on the side closer to the collimated light source  10  in the flow channel  20 , and the second particle P 2  is located on the side farther from the collimated light source  10  in the flow channel  20 . The parallel beam I irradiating the first particle P 1  and the second particle P 2  passes through the fluid L in the flow channel  20  and the flow channel  20  before transmitted to the telecentric lens  30 . Afterwards, the parallel beam I is converged onto the image sensing apparatus  60  through the telecentric lens  30  to form an image IM shown in  FIG.  6 B . 
     The image IM includes a first particle image P 1 ′ and a second particle image P 2 ′. The first particle image P 1 ′ is an optical image corresponding to the first particle P 1 , while the second particle image P 2 ′ is an optical image corresponding to the second particle P 2 . Magnification M 1  of the first particle image P 1 ′ is similar to magnification M 2  of the second particle image P 2 ′. For example, the ratio of the magnification M 1  of the first particle image P 1 ′ to the magnification M 2  of the second particle image P 2 ′ may range from 1 to 1.0358, but the disclosure is not limited thereto. In this embodiment, the magnification M 1  of the first particle image P 1 ′ is substantially the same as the magnification M 2  of the second particle image P 2 ′. Therefore, the first particle image P 1 ′ and the second particle image P 2 ′ may present the size relationship between the first particle P 1  and the second particle P 2  in a more accurately way. For example, if the size of the first particle P 1  and the size of the second particle P 2  are substantially the same, then the size of the first particle image P 1 ′ and the size of the second particle image P 2 ′ are also substantially the same, regardless of where the first particle P 1  and the second particle P 2  are located in the flow channel  20 . Therefore, the optical imaging system  1  of the disclosure may analyze a particle and measure the particle size more accurately. The magnification M 1  of the first particle image P 1 ′ and the magnification M 2  of the second particle image P 2 ′ may fall within a range from 3.8447 to 3.982253, but the disclosure is not limited thereto. 
     In summary, the optical imaging system of the disclosure, with the collimated light source and the telecentric lens, projects the parallel beam onto the flow channel and makes the parallel beam pass through the flow channel before imaged by the telecentric lens, which may improve the depth of field of the optical imaging system and make the image of the particle in the flow channel clearer. In addition, the optical imaging system of the disclosure may further reduce the impact of particle positions on image magnification, which enables the information of the particle in the flow channel to be counted and analyzed more accurately.