Patent Application
20090273831
This application claims the benefit of Taiwan application Serial No. 97116541, filed May 5, 2008, the subject matter of which is incorporated herein by reference.
1. Field of the Invention
The invention relates in general to a light module, an optical tweezers generator and a dark field microscope, and more particularly to a light module, an optical tweezers generator and a dark field microscope capable of reducing the loss rate of the light.
2. Description of the Related Art
Referring to
The surrounding light 114 passing through the condensing lens 120 illuminates the field of view of the microscope. Some of the illuminating light 114 is scattered by the object 141 to be examined. The scattered light 116 can enter the lens 150 to form an image of the object 141 behind. However, the rest of the illuminating light 114 that is not scattered by the object 141 will propagate straight and does not enter the lens 150 because of its large angle of inclination. In another words, the unscattered light 115 will not contribute to the image as a background noise. Thus, the image displayed by the dark field microscope 100 shows a bright object with a dark background. Therefore, the image of the dark field microscope is clearer than that of a bright field microscope because of high-contrast. Unfortunately, the conventional dark field microscope 100 has the following disadvantages.
Firstly, the brightness of the image is low. In order to display an image of the object with a high contrast, the dark field stop 130 blocks most of the source light 111. Thus, only the surrounding light 114 which is a small part of the source light 111 is allowed to enter the condensing lens 120, illuminate the object, and form the image. Typically, the loss rate of the source light 111 blocked by the dark field stop 130 is as high as 80%. As the loss rate of the light is high, less light illuminates the object 141. Consequently, the brightness of the image is low.
Secondly, both the magnification and the resolution of the conventional dark field microscope are low. To prevent the unsacttered light 115 from entering the lens 150, the numerical aperture (NA) of the lens 150 needs to be smaller than that of the condensing lens 120. Therefore, it is necessary for the conventional dark field microscope 100 to sacrifice the magnification of the lens 150 and thus the resolution of the image. Consequently, both the magnification and the resolution of the image are low.
The invention is directed to a light module, an optical tweezers generator and a dark field microscope. In order to reduce the loss rate of the source light, the light module is invented to convert all of source light into a circular beam. Particularly, the circular beam passes through the light module and is highly focused to illuminate an object to be examined at a large inclination angle. Thus, the brightness, the magnification, and the resolution of the invented dark field microscope are high. On the other hand, because the circular beam completely passes through the condensing component and is highly focused to illuminate the object at a large inclination angle, the light module also generates a trapping force onto the object like an optical tweezers generator.
Firstly, the present invention provides a light module. The light module is applied to the invented dark field microscope for illuminating an object to be examined. The light module mainly consists of a reflection component and a condensing component. The reflection component is used to convert all of an incident light beam into a circular beam. Particularly, the circular beam completely passes through the condensing component and is highly focused to illuminate the object at a large inclination angle.
Secondly, the present invention provides an optical tweezers generator as well. The optical tweezers generator makes use of the same components of the invented dark field microscope, which includes the reflection component and the condensing component. The reflection component is used to covert all of a laser beam into a circularly hollow beam. Particularly, the circularly hollow beam completely passes through the condensing component and is highly focused onto the object at a large inclination angle.
The invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.
According to the light module, the optical tweezers generator and the dark field microscope of the invention, an incident illuminating light beam is converted into a circular beam for illuminating the object to be examined. Meanwhile, the object may be trapped by a laser beam incident into this light module, simultaneously. The invention is disclosed below by way of embodiments.
Illuminating Object
Referring to
The light beam 240 is a collimated beam and is guided from either of the two entrances of the light module 230 to the reflection component 250 inside. The reflection component 250 is used for converting the light beam 240, which is collimated and sold, to a circular beam CL substantially radiating along the beginning direction BD. The circular beam CL is hollow. The circular beam CL passes through the condensing component 260 and is focused onto the object 201. Preferably, the circular beam CL passes through the edge of the condensing component 260. Thus, the circular beam CL is focused on the object 201 at a large angle of inclination. A large portion of the circular beam CL is scattered by the object 201. The scattered light 243 is projected onto an image plane (not illustrated) to form an image of the object 201 by the lens 210. A small portion of the focused circular beam CL is not scattered by the object 201. The unscattered light 244 does not enter the lens 210, and therefore will not contribute to the background noise of the image.
Thus, a high-contrast image of the object 201 is formed behind the lens 210. Besides, the dark field microscope 200 can guide most of the incident collimated beam 240 to illuminate the object 201 via the condensing component 260, thus reducing the loss rate of the light to as low as 5%.
The first reflection element 251 and the second reflection element 252 are preferably coated with a dielectric film (not illustrated) with high reflectivity. In the present embodiment of the invention, the reflection component 250 includes the first reflection element 251 and the second reflection element 252 but is not limited thereto. In practical application, any reflection components capable of guiding the light into a circular beam will do.
In the present embodiment of the invention, the numerical aperture of the condensing component 260 substantially is 1.3, such that the circular beam CL can illuminate the object 201 at a very large angle of inclination. Thus, the contrast and resolution of the image of the object 201 as well as the magnification are increased.
Providing Optical Tweezers
The light module 230 also provides a trapping force to the object 201 like an optical tweezers generator. As indicated in
The optical tweezers, being a non-mechanical operating technology, is neither invasive nor destructive to the object 201. After, the reflection component 250 converts the laser beam 241 into a circular beam CL, the circular beam CL is able to pass through the condensing component 260 to the object 201. Thus, a large gradient force is provided to trap and manipulate the object 201.
Besides, the numerical aperture of the condensing component 260 can be as high as 1.3, so that the circular beam CL is focused on the object 201 at a considerable large angle of inclination.
Preferably, the light module 230 has at least one dichroic mirror 270 of high reflection at a particular wavelength. In the present embodiment of the invention, two dichroic mirrors 270 are used for reflecting the laser beam 241 toward the reflection component 250.
Concurrently Illuminating Object and Providing Optical Tweezers
The light module 230 can be used to illuminate the object 201 and at the same time exert a trapping force of optical tweezers to the object 201. The reflection component 250 converts the illuminating light 241 into the circularly hollow beam CL substantially radiating along the beginning direction BD. The circular beam CL passes through the edge of the condensing component 260, thus the circular beam CL is focused onto the object 201 with a large angle of inclination. Meanwhile, most of the focused circular beam CL is scattered by the object 201. The scattered light 243 is projected onto an image plane (not illustrated) to form an image of the object 201 by the lens 210. At the same time, a trapping force of optical tweezers is exerted to the object 201.
Due to chromatic aberration, the location of the image of the object 201 formed by the dark field microscope 200 will vary with wavelength. Similarly, the location of the trapping point focused by the optical tweezers generator varies with wavelength. In order to adjust this aberration, in the present embodiment of the invention an achromatic lens 280 is adopted in the light module 230. By doing so, the module 230 may create an image of the object 201 at the same image plane with the laser beam 242 of any wavelength. Similarly, the light module 230 may generate a trapping point of optical tweezers at the same location.
According to the light module, the optical tweezers generator and the dark field microscope of the invention, a light beam is converted into a circular hollow beam. The circular beam passes through the condensing component and is focused on the object. Since the light module reserves nearly all the incident light beam for illumination, the image of the object will have a high brightness. In addition, because of the large inclination angle of the illuminating light, the object also has a high contrast, magnification, and resolution image. Moreover, as the light of the light beam is effectively used to illuminate the object or provide an optical tweezers, the loss rate of the light is reduced. Besides, as the numerical aperture of the condensing component substantially is 1.3, the circular beam is able to pass through the condensing component with a tremendously large angle of inclination. Because of the large angle of inclination, the circular beam and the highly focused laser beam generates a trapping force onto the object within the field of view of the invented dark field microscope.
While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.
| Number | Date | Country | Kind |
|---|---|---|---|
| 97116541 | May 2008 | TW | national |
