![]() Miniaturized, high-numerical-aperture lenses that have been developed for this configuration require multielement designs with tight tolerances and long optical paths, which affect the instrument size 29, 37, 38, 39, 40. The majority of MEMS-scanned microscopes (and fiber-scanned and fiber bundle systems) use preobjective scanning 29, 30, 31, 32, 33, 34, 35, 36, which requires an objective lens that is well corrected over a finite field of view. One choice that can influence the size is whether to use preobjective scanning or postobjective scanning. However, the instrument size depends on the optical architecture, in addition to the optomechanical components. This eliminates the need for motor-driven mechanical focusing and further reduces the instrument size. A 3D MEMS scanner can realize focus control in addition to 2D lateral scanning via a tip/tilt/piston motion 21, 22, 23, 24, tip/tilt/curvature control 25, 26, 27, or a combination 28. A biaxial MEMS scanner replaces two bulky galvanometer scanners and, potentially, a lens relay between them. In addition to having a small footprint, a MEMS scanner contributes to miniaturization by combining multiple degrees of freedom into a single active element. ![]() MEMS has also facilitated the adaptation of laser scanning microscopy to endoscopic platforms 15, 16, 17 and MEMS-based optical biopsy systems have demonstrated in vivo detection of cancer in regions of the head, neck, esophagus, and cervix 18, 19, 20. For example, a MEMS-scanned miniaturized two-photon microscope that weighed only 2.15 grams and was small enough to be mounted on the head of a freely moving mouse was used to image neuronal dendrites and spines within the brain 13, 14. This has enabled applications that were not previously possible. Microelectromechanical system (MEMS) devices replace the bulky mechanisms that are required for scanning and focusing the beam with components that are only millimeters in dimension. Miniaturization of the scanning mechanism was a necessary first step in the development of smaller instruments. For imaging ambulatory animals and for accessing most of the human body, miniaturization of these instruments is necessary. However, the large size of a conventional laser scanning microscope limits its potential for both medical and live animal imaging. Large handheld or gantry-arm-mounted microscopes are used in dermatology clinics, which enable noninvasive and more thorough examination to reduce the dependence on physical biopsy for ruling out skin cancer 7, 8, 9, 10, 11, 12. Substantial progress has been made in imaging small animals, such as mice, that can be immobilized on the stage of a benchtop microscope 5, 6. Scanning laser confocal and multiphoton microscopy techniques are a mainstay for in vivo imaging of unprepared, uncleared organs in live animals 1, 2, 3, 4. The optical performance of the active catadioptric system is simulated and imaging of hard targets and human cheek cells is demonstrated with a confocal microscope that is based on the new objective lens design. We implemented this new optical system using a recently developed hybrid polymer/silicon MEMS three-dimensional scan mirror that features an annular aperture that allows it to be coaxially aligned within the objective lens without the need for a beam splitter. The MEMS-in-the-lens architecture incorporates a reflective MEMS scanner between a low-numerical-aperture back lens group and an aplanatic hyperhemisphere front refractive element to support high-numerical-aperture imaging. In this paper, we propose a catadioptric microscope objective lens that features an integrated MEMS device for performing biaxial scanning, axial focus adjustment, and control of spherical aberration. The emergence of multifunctional active optical devices can support further miniaturization beyond direct component replacement because those active devices enable diffraction-limited performance using simpler optical system designs. Laser scanning microscopes can be miniaturized for in vivo imaging by substituting optical microelectromechanical system (MEMS) devices in place of larger components. ![]()
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