Month: February 2015

An active treadmill to control locomotion

As documented in several publications, active locomotion can strongly modulate cortical activity. I explained earlier how Scanbox uses a quadrature encoder to be able to control, in real time, an external stimulus that depends on the state of locomotion. In this way, we can design experiments in which stimuli are delivered during periods of locomotion or rest.

However, if either locomotion or rest are not sampled often enough by an individual subject, one may want to use an active treadmill to have some control over their duration.  The same controller used to move the motors of the microscope has additional axes that can be used for this purpose, allowing us to slowly ramping up and down the velocity of the platform with arbitrary velocity profiles. The video below shows the smooth acceleration and deceleration we can achieve.  The Scanbox interface keeps track of commands issued to the treadmill and monitors the actual physical movement through the quadrature encoder.

Simultaneous control of an electrically tunable lens and a pockels cell

We are preparing Scanbox for fast, volumetric scanning, by providing simultaneous control of an electrically tunable lens (to focus on different planes) and a Pockels cell (to control laser power).

The Scanbox card has an integrated, 12-bit current source used to control the focus tunable lens. Similarly, an integrated DAC on the Scanbox card controls laser power via a Pockels cell. The mechanism implemented still allows for user-defined blanking of the margins.  Arbitrary tables can be uploaded from the Scanbox GUI to the card to allow for simultaneous changes in these variables that are precisely synchronized to the frames of the microscope.

Below is a demonstration showing a sinusoidal change in focusing along with matching changes in laser power.  Fast scanning with synchronized depth/power control is coming to Yeti soon!

[vimeo 119605807 w=500&h=280]

Better positioning with a wireless 3D mouse

The latest Scanbox release switches its positioning mechanism to rely on the 3dconnection wireless SpaceMouse.  A single controller provides a more intuitive, responsive and smoother control of microscope position.  It is more intuitive because the panning controls align with the axes of the microscope, and a twist motion of the knob allows you to rotate the objective.

3dmouse

With the 3D mouse it is no longer necessary to specify an axis before movement — you just move the joystick in the desired direction and the axes will be selected.  It also provides two buttons that allow switching between coarse/fine motion and normal/rotated modes. The interface is and faster through java-based listeners that take care of the motion without interfering with data acquisition and display.

imgres

Because the communication and control methods with the motor control box have changed substantially, the older ShuttleXpress wheel will no longer be supported in future releases.  So make sure you have your 3D mouse before upgrading to the most recent version of Scanbox.  It can be obtained here.