Changing the Internal Focuses

The page below describes how to control the internal focuses (the detector positions along the optical axis) in the instrument. The each internal focus will be usually adjusted to specific position based on the measurement at laboratory, after the initalizing command (such as "fs all init") at beginning night. If you don't need to change a internal focus from the default position, you don't need to use the below command. And, please note that the details given below are subject to change at any time.

How to Control the Internal Focuses

To control the internal focuses, type on demi or on trispec as follows.
% fs <focus_number> <focus_control_command> [<argument> ...]
The following value are currently available as focus_number.
1   -   the Slit viewer
2   -   the optical channel
3   -   the IR1 channel
4   -   the IR2 channel
sl   -   the Slit viewer (alias 1)
br   -   the optical channel (alias 2)
jh   -   the IR1 channel (alias 3)
kl   -   the IR2 channel (alias 4)
all   -   the Slit viewer and all channels
And, the following commands are currently available as focus_control_command.
  • param   -   Set the motor control parameters for the focus.
  • rst   -   Move until turn on the front limit switch, then the position is set to zero.
  • ml   -   Move until turn on the front or back limit switch. (the command requires 0 for front, or 1 for back, as id of the limit switch)
  • mv   -   Move by requested step. (the command accepts -260 to 260 as step.)
  • set   -   Move to requested position. (the command accepts 0 to 260 as position.)
  • pos   -   Show current position of the focus.
  • init   -   Move to the initial position of the focus.
  • test   -   Test both front and back limit positions.
  • For several focus control commands mv and set, the command accepts the following omitted usage as well.
    % fs <focus_number> [+|-]<number>
    If you add a plus or minus sign to a number, the number will be interpret as the step number for the control command mv. If you do not, it will be interpret as the position number for the control command set.

    The each step represents movement of the detector by 5µm, with increasing number indicating movement of the detector away from the slit/mask plane (that is, away from a telescope). The each front limit position is usually used the zero point. The each stroke between a front limit and a back limit is 200 to 260 steps.

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    Last Modification Date: 2001/02/18
    Last Modification Author: Makoto Watanabe <>