Three-dimensional optical coherence tomography confocal imaging apparatus

#The present invention relates to a three-dimensional optical coherence tomography (3D OCT) confocal imaging apparatus, and more particularly to a 3D microscope for forming optical coherence tomography images and confocal microscopic images.

#In early stage, microscopic technology is realized mainly by electron microscope and optical microscope. An optical microscope uses optical lenses to magnify images of a sample to reach a resolution up to 200 nm. On the other hand, an electron microscope utilizes the short wavelength characteristic of electrons to observe micro crystal structure or biological cellular structure. In the case of a transmission electron microscope, a resolution up to 0.1 nm can be reached. However, the transmission electron microscope would disadvantageously cause chemical changes in the sample; and electron beams illuminating the samples tend to destroy organic materials, molecular structures, DNA, etc.

#A confocal microscope is developed from the optical microscopic technology. It has a light source that emits laser light, which passes lenses to focus on the sample. If the sample is located at the focal point, reflected light would pass the lenses to condense on the light source and form a confocal condition. The confocal microscope includes a dichroic mirror arranged on the optical path of the reflected light for refracting the reflected light to other directions, and a pinhole is provided on a focal point of the dichroic mirror. When the reflected light passes through the pinhole, an image can be formed on a photosensor. When the light source scans the sample, a three-dimensional (3D) image of the sample can be created. U.S. Patent Publication No. 2009/0310083 discloses an application of the confocal microscope using polarized light. Taiwan Patent Publication No. 200619673 also discloses a method of increasing the measuring resolution in depth of a confocal microscope using light interference. U.S. Pat. No. 5,804,813 discloses the use of a differential confocal microscopy, in which a He—Ne laser or a solid-state laser is used as a light source to reach a resolution in depth of 2 μm and a lateral resolution of 0.3 μm. However, the confocal microscope has a main disadvantage of uneasy to show the image quickly. When the confocal microscope is applied in the study of biofilm, collagen protein, cell movement, liquid interface or liquid-gas interface characteristics and the like, there would be considerable limitation. Moreover, the confocal microscope has a resolution in depth being limited to the size of the pinhole and accordingly has very small penetration depth, making the confocal microscope not good enough for use.

#The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein

#FIG. 1 is a schematic diagram of a 3D OCT confocal imaging apparatus according to a first embodiment of the present invention;

#FIG. 2 is a schematic diagram of a 3D OCT confocal imaging apparatus according to a second embodiment of the present invention;

#According to a confocal microscope, a pinhole is provided on the optical path of the sample and lateral scanning is used, so that a three-dimensional contour of the sample can be detected using the confocal light intensity signal. The main principle of the confocal microscope is that, when a light ray from a point light source illuminates the sample and the sample is located at the focal plane, the catoptrical light ray is allowed to pass through the pinhole to the photosensor; and, in the case the sample is not located at the focal plane, the catoptrical light ray is blocked by the pinhole from passing therethrough. From the information detected by the photosensor and the scan positions of the sample in X, Y and Z directions, it is able to reconstruct the 3D image of the sample.

#The main principle of the OCT is that, when short-time coherence interference rises between the light beam reflected from the sample and the reference beam, the detected interference signal can undergo image processing and be converted into the depth-sectioning image of the sample. Along the optical path of the reference beam, there are arranged a focusing lens, a mirror, and a piezoelectric actuator (PZT). The PZT is used as an optical delay line. Depending on different applications of the reference beam or the light reflected from the sample, the PZT may be fixed to a dual-axis linear stage or another PZT is provided, in order to achieve the purpose of extending or shortening the distance of the reference beam. The dual-axis linear stage can be a translation stage driven by a step motor. FIG. 4 shows an OCT imaging apparatus 4 constructed according to the above-described principle. As shown, the OCT imaging apparatus 4 includes a light source module 5, a beam splitter 115, a reference source module 6, a pickup module 7, and a sensor module 8. The light source module 5 includes a broadband light source 1111, a focusing lens 112, a collimator 114, and an optical filter 118. The light source module 5 is adapted to emit broadband light, which passes through the focusing lens 112 and the collimator 114 to produce a collimated illumination beam. To match the spectrum of light needed to examine a sample 10, the pumping light in the beam is filtered by the optical filter 118. The filtered broadband illumination beam then passes and is refracted by the beam splitter 115 to illuminate the sample 10.

#The pickup module 7 can include a pickup objective lens 117 and a dual-axis linear stage 116. The pickup objective lens 117 can be a high NA or a low NA objective lens. When the illumination beam enters the pickup module 7, the pickup objective lens 117 can focus the illumination beam on the sample 10. The dual-axis linear stage 116 serves to move the sample 10 in an X-Y plane of the sample 10, so that different positions on the sample 10 can be examined. An image of the sample 10 is reflected from the sample to pass through the pickup objective lens 117 and form an image beam, which is interfered by the reference beam produced by the beam splitter 115 and the reference source module 6 and then projects onto the sensor module 8. At the sensor module 8, the image beam is converted into an electric signal.