mesoSPIM_optical_design_detection_arm
Overview of the mesoSPIM detection arm.
The mesoSPIM detection path consists of an Olympus MVX-10 macroscope with a MVPLAPO 1x objective, which allows FOVs of 2-20 mm in combination with a Hamamatsu Orca Flash 4.0 V3 camera. Due to its zoom system, the Olympus MVX-10 does not have a classical infinity-corrected space between objective and tube lens/zoom body that could be varied for focusing. Therefore, we opted to translate the entire detection path (MVX10 + filter wheel + camera assembly) for focusing by mounting it on a heavy-duty linear stage (PI M-406.4PD). The focusing stage carries an additional FLS-95 rail so that the detection system can be highly modular. The stage also aids in refocusing between different zoom settings as the MVX-10 has a large focus drift with magnification (> 150 μm for a change from 1× to 4×). The MVX-10 has a manual zoom wheel which we motorized by attaching a Robotis Dynamixel MX-28R servo to it. The MX-28R is computer-controlled via a serial RS-485 connection and has an internal rotation encoder with a resolution of 4096 steps/revolution, which we deemed to be adequate for the approximately 160 degrees of rotation necessary to change the zoom setting from 0.63× to 6.3×. For higher magnification, the Olympus MVPLAPO 2x objective can be used, but it has large distortion in the corners of the FOV. At the rear port of the MVX-10, we attached a Ludl 96A350 filter wheel with ten 32-mm filter positions. The filter wheel is controlled by a MAC-6000 controller which is connected via RS-232 to the imaging computer. The rear port of the filter wheel housing interfaces with a Olympus MVX-TLU tube lens and a MVX-TV1xC C-mount adapter to which the camera is attached. The camera is rotated by 90° around the detection axis because in an ALSM instrument, the read-out direction of the rolling shutter and the translation of the waist have to be parallel.