Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B21/00—Microscopes
  • G02B21/0004—Microscopes specially adapted for specific applications
  • G02B21/002—Scanning microscopes
  • G02B21/0024—Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders
  • G02B21/008—Details of detection or image processing, including general computer control
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B21/00—Microscopes
  • G02B21/0004—Microscopes specially adapted for specific applications
  • G02B21/002—Scanning microscopes
  • G02B21/0024—Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders
  • G02B21/0028—Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders specially adapted for specific applications, e.g. for endoscopes, ophthalmoscopes, attachments to conventional microscopes
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B21/00—Microscopes
  • G02B21/0004—Microscopes specially adapted for specific applications
  • G02B21/002—Scanning microscopes
  • G02B21/0024—Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders
  • G02B21/0032—Optical details of illumination, e.g. light-sources, pinholes, beam splitters, slits, fibers
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices
  • G02B23/24—Instruments or systems for viewing the inside of hollow bodies, e.g. fibrescopes
  • G02B23/2407—Optical details
  • G02B23/2423—Optical details of the distal end

Definitions

• the present invention relates to a system and method for parallel confocal laser microscopy. It applies in particular, but not exclusively, to the field of medical imaging.
• confocal microscopy 0 In general, the principle of confocal microscopy 0 is based on the illumination of a sample by a point light source and by the detection of photons returning from this sample through a filtering hole conjugated with a plane of excitation, this in particular making it possible to obtain an optical cut. 5
• confocal microscopy 0 is based on the illumination of a sample by a point light source and by the detection of photons returning from this sample through a filtering hole conjugated with a plane of excitation, this in particular making it possible to obtain an optical cut.
• Jp / papers / optics / conf / naruse_confocal_SPIE00.pdf Jp / papers / optics / conf / naruse_confocal_SPIE00.pdf
• the author describes a system 1 of confocal microscopy 0 parallel in accordance with FIG. 1.
• the mirror 11 makes it possible to deflect the beam of light backscattered by the sample 13 to a matrix of photo-detectors 16.
• filtering holes 15 are arranged upstream of the photo-detectors 16 A control unit
• the object of the present invention is a miniature confocal microscopy system.
• Another object of the invention is to propose a microscopy system making it possible to acquire images in real time.
• Another object of the invention is to allow laser scanning for the acquisition of good quality images. At least one of the above objectives is achieved with a parallel confocal laser microscopy system comprising in particular:
• a photo-detector is arranged on one face of each VCSEL laser so that this photo-detector is capable of collecting a beam of light coming from the object via the cavity of the VCSEL laser, this cavity having a opening used as a filter hole.
• the invention is particularly remarkable in that a quasi point laser source is used, the cavity opening of which serves as a filtering hole.
• the opening of the VCSEL laser cavity advantageously has a diameter of a few microns.
• the photo-detector is arranged on a face opposite the opening of the cavity of the VCSEL laser.
• the laser source and the photo-detector are aligned with the optical axis, the axis of the laser beam.
• These two elements can be integrated into the same device, which considerably reduces the size of the system.
• the system can thus consist of a miniature head in the form of a housing. We can then provide applications such as endoscopy for which we have the miniature head at the end of an endoscope.
• the outside diameter of the miniature head can be between 2 and 10mm, for a length between 10 and 30mm.
• this miniature head and its electrical wiring can be inserted into the operating channel of an endoscope, the operating channel usually serving to pass the tools which a practitioner has need to carry out measurements or samples.
• the head is thus brought to the end of the endoscope so as to carry out in particular an optical biopsy.
• the system according to the invention can be used during backscattering applications.
• the system can also comprise scanning means for carrying out a laser scan so as to produce an image.
• the matrix makes it possible in particular to work on a large number of data at the same time, therefore to improve the quality of the image obtained. Indeed, we can stay longer on each point and integrate longer.
• the useful signal then contains enough information to allow quality processing.
• Several points are acquired at the same time while preserving the confocality, the latter being ensured by the almost point source assembly (spatial filtering) and optical system.
• the confocality criterion can make it possible to make optical cuts of the order of 1 to 3 microns.
• the choice of the VCSEL laser (useful diameter cavity and digital aperture) and of the optical system (magnification, digital aperture) is notably imposed by confocality.
• the system further comprises means for controlling the scanning means so as to carry out image acquisition in real time.
• the system makes it possible to descend to low scanning frequencies such as for example 400 Hz, for which the components are extremely reliable while allowing acquisition of images. in real time.
• real time we mean an acquisition from about ten images per second.
• prior systems require scanning frequencies above 4 kHz.
• the loss of flux is reduced since the semi-transparent mirror disappears; the sensitivity of the detection can be improved by increasing the integration time of the data since the acquisition is made on several points at the same time; and the line scanning frequency of the images can be adjusted in particular downward.
• the field of observation can be sufficiently large, that is to say present an area of at least 150 microns by 150 microns for example.
• the confocal nature and a sufficiently large field of observation represent a real advantage in the medical field, in particular within the framework of assistance to the early diagnosis of cancerous lesions.
• Continuous scanning makes it possible to obtain an image in which each pixel represented carries useful information originating from the sample.
• the scanning frequencies and the number of laser sources can be determined so as to achieve image acquisition in near real time. In certain fields such as medical, real time is a necessity to compensate for the patient and practitioner shake.
• the scanning means can comprise MEMS micro-systems ("micro-electro-mechanical System", in English) and / or piezoelectric blocks, capable of moving the matrix of VCSEL lasers and / or the optical means.
• MEMS micro-systems micro-electro-mechanical System
• piezoelectric blocks capable of moving the matrix of VCSEL lasers and / or the optical means.
• the optical system may include one or more refractive and / or diffractive lenses.
• the optical means in particular the lenses, are capable of directing each beam of light coming from the object to be observed towards the cavity of a VCSEL laser, the opening of the cavity then performing filtering.
• the light beams of leakage emitted at the rear of the VCSEL laser and picked up by the photo-detector are not negligible compared to the useful light beam from the object to be observed.
• means are available for modulating the outgoing light beams of the matrix. These means can be an acousto-optical or electro-optical modulator, or any other type of suitable modulation means.
• the light beams coming from the object to be observed are also modulated. We can then have synchronous detection means to extract a useful signal from the electrical signal generated by each photo-detector.
• the optical means can comprise at least one movable lens to allow image acquisition at different depths of the object to be observed. It is thus possible to produce three-dimensional images. It is also possible to use lenses with variable curvature or to move the matrix axially, that is to say along the z axis, to carry out a deep scanning.
• a method of parallel confocal laser microscopy in which a plurality of beams of light are emitted from a matrix of lasers with vertical cavity VCSEL, and these beams of light are focused on an object to be observed by means of an optical system such as lenses for example.
• an optical system such as lenses for example.
• the photo-detector is arranged on the face opposite the opening of the laser cavity.
• FIG. 2 is a block diagram illustrating the operation of a microscopy system according to the invention.
• FIG. 3 is a diagram illustrating an example of sizing of the main elements of a microscopy system according to one invention
• FIG. 4a is a sectional view of an electronic component comprising a laser of the VCSEL type produced on a photo-detector;
• - Figure 4b is a top view of the VCSEL laser of Figure 4a;
• FIG. 6 is a simplified diagram of the system according to one invention in which the laser scanning is obtained by 0 displacement of the matrix by means of piezoelectric shims.
• FIGS. 2 to 6 We will now describe a miniature head according to the invention by means of the simplified and nonlimiting diagrams of FIGS. 2 to 6.
• the system 2 according to the invention does not include a semi-transparent mirror.
• the transmitter that is to say the laser VCSEL
• the receiver that is to say the photo-detector
• the transmitter that is to say the laser VCSEL
• the receiver that is to say the photo-detector
• Each VCSEL laser 23 of the matrix emits monochromatic and mono-mode light which is focused by an optical system 24 in the object to be observed such as a sample 25.
• VCSEL lasers with a wavelength between 630 nanometers and 1200 nanometers are used.
• the light beam backscattered from the sample 25 takes the same path as the incident beam via the optical system 24, then returns to the VCSEL laser 23 passing through it to the photo-detector
• the electrical signal generated by the photo-detector 22 is processed by a processing system 21 comprising in particular amplification and digitization means.
• the digitized signal 29 is then transmitted to a control unit 26.
• control signals 28 can consist of commands to move the matrix in two directions x and y so as to acquire two-dimensional images (as will be seen in FIG. 6), in signals for controlling the light intensity of the VCSEL lasers, in signals for controlling the photo-detectors and in signals for controlling the processing means.
• the control signals 27 are capable of managing the movement of the optical system as will be seen in FIG. 5.
• the matrix and the optical system can be integrated into a miniature head 20 disposed at the end of an endoscope.
• FIG. 3 shows an example of dimensioning of a system according to the invention.
• the optical system includes two diffractive lenses.
• the design parameters are as follows:
• Wavelength between 680 and 880 nm;
• Source field: 2 ⁇ X 400 - 600 ⁇ m
• Diameter of the opening of the VCSEL cavity: ⁇ ca vity 2-4 ⁇ m
• Focal length of first lens: fl 3mm
• Diameter of the first lens: ⁇ to tai 2mm
• Focal length of the second lens: f2 1.17mm
• Diameter of the second lens: ⁇ 2 1.6mm
• a laser scanning is carried out either by moving lenses of the optical system 24 by ME S systems as will be seen below in FIG. 5, or by moving the matrix by piezoelectric shims as will be seen in FIG. 6.
• the scanning frequencies are chosen as a function of the number of source points (VCSEL laser) used simultaneously in the matrix. For example, for a 10 by 10 matrix, we use frequencies of 10 hertz (frame) and 400 hertz (line). These frequencies make it possible to obtain a two-dimensional real-time scan.
• the signal from the sample is found focused at the input of the VCSEL laser using the same optical path as the incident signal.
• the spatial filtering necessary for confocalization is carried out at the input / output of the VCSEL laser because the opening of the cavity of this laser is of the order of a few microns. Confocality is dependent on the digital aperture and the magnification of the optical system as well as the digital aperture of the lasers.
• the signal thus filtered is then detected by the photo-detector which is placed behind the cavity of the laser.
• the amplification factor of the VCSEL laser cavity is approximately 10 6 .
• Two detection modes such as:
• the VCSEL laser emits continuously. Part of this emitted light is detected by the photo-detector because the Bragg mirror of the cavity on the detector side has a transmission of the order of 1%.
• the background signal detected by the photo-detector and coming from the cavity is of the order of 10 "2.
• the signal coming from the backscatter sample being of the order of 10 " 5 at 10 "6 , this signal is amplified by the cavity until reaching a value between 1 and 10 in the cavity. Passing through the Bragg mirror changes its value between 10 " 2 and 10 "1.
• the useful signal generated by the photodetector is therefore at least of the order of the background signal.
• the output signal of the VCSEL laser is modulated by an acousto-optical modulator (not shown) placed in the optical system 24.
• the useful signal is therefore also modulated at the same frequency. It then suffices to use synchronous detection with the modulation signal to extract the useful signal and reject the background signal.
• FIG. 4a a little more detail is seen of an electronic component according to the invention in which, from the same substrate, a photodetector and a VCSEL laser are produced by epitaxial growth.
• the photodetector is arranged on the rear face of the laser opposite the emission face of the laser.
• Figure 4b is a front view of the electronic component of Figure 4a.
• the diameter of this opening can be between 2 and 8 micrometers while the electronic component as a whole can have a length of 50 microns.
• Figure 4c is a front view of several electronic components of the figure 4a arranged in a matrix. With the dimensions of FIG.
• FIG. 5 there is a miniature head according to the invention in which the laser scanning is obtained by displacement of two lenses.
• the miniature head of FIG. 5 comprises a box 50, at the base of which is placed a VCSEL laser matrix / photodetector 51.
• the lasers of the matrix emit along parallel axes towards the interior of the box 50.
• the light beams emitted pass through three lenses 52, 53 and 54 so as to be focused in an object (not shown) outside the casing on the other side of an outlet porthole 55 disposed on the base opposite the base containing the matrix 51
• the light beams all converge in an image field plane arranged in the object to be observed (not shown).
• the convergence lens 54 is fixed integral with the box 50, while the two lenses 52 and 54 are mobile because they are fixed on MEMS microsystems 56 and 57.
• the MEMS 56 makes it possible to move the lens 52 in a direction X in a plane perpendicular to the laser emission axis.
• the MEMS 57 makes it possible to move the lens 53 in a direction Y perpendicular to the axis of emission of the lasers and to the axis X. These displacements make it possible to carry out a laser scanning in, an X Y plane. Then, by processing the signal downstream of the photo-detectors, the image field can be reconstructed.
• the scanning amplitude of MEMS microsystems is determined so as to reach at least 150 by 150 microns of imaged fields for example.
• the data processing can consist of conventional algorithms.
• the laser scanning can take place by displacement of the matrix.
• the miniature head is a box 60, at the base of which is disposed a matrix 61.
• Piezoelectric shims are interposed between the lateral faces of the matrix and the box 60. These piezoelectric shims are arranged in pairs on parallel sides .
• the shims 62 allow movement along the X axis, and the shims 63 allow movement of the matrix along the Y axis.
• the lenses 64 and 65 for focusing the light beams can be fixed. We use while two lenses instead of three previously.
• the amplitude of displacement of the piezoelectric shims allows the overlap of each VCSEL laser.
• this amplitude is around 50 microns.
• the laser scans as shown in FIGS. 5 and 6 make it possible to obtain a two-dimensional image of the imaged field. We can then introduce a scanning of the light beam in an axial direction to choose the viewing depth in the object to be observed. Scanning in the Z direction perpendicular to the X and Y directions allows three-dimensional reconstructions of the object observed. To do this, different two-dimensional acquisitions are made at different depths and a volume is reconstructed by data processing.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Computer Vision & Pattern Recognition (AREA)
• Astronomy & Astrophysics (AREA)
• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Ophthalmology & Optometry (AREA)
• Radiology & Medical Imaging (AREA)
• Surgery (AREA)
• Microscoopes, Condenser (AREA)
• Instruments For Viewing The Inside Of Hollow Bodies (AREA)

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• 2002
  • 2002-12-20 FR FR0216276A patent/FR2849215B1/fr not_active Expired - Lifetime
• 2003
  • 2003-12-12 EP EP03815394A patent/EP1579260A1/de not_active Ceased
  • 2003-12-12 AU AU2003296826A patent/AU2003296826A1/en not_active Abandoned
  • 2003-12-12 WO PCT/FR2003/003687 patent/WO2004066015A1/fr active Application Filing
  • 2003-12-12 JP JP2004566992A patent/JP2006515075A/ja active Pending
  • 2003-12-12 US US10/539,572 patent/US20060256194A1/en not_active Abandoned

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