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uScope Navigator (Device Settings) Step Size and Range Settings
uScope Navigator (Device Settings)

Information in this article applies to:

  • uScope Navigator V4.0 and Later

Article ID: NDS1154 — Created: 23 Feb 2018 — Reviewed: 8 Jun 2018

Question

In the Device Settings for the uScope, there are a number of options that specify a Step Size and a Range. What is the meaning of these settings?

Answer

The Step Size is the minimum amount of movement (up or down) the objective makes when changing focus while the Range is the maximum amount of movement the objective makes when changing focus.

The following sections provide more information about the Step Size and Range settings.

Step Size

The objective moves up and down under the power of a stepper motor. The stepper motor moves in increments of steps. All Step Size settings specify the number of motor steps to move the objective. One step is approximately 0.1984 microns. So, 10 steps are the equivalent of 1.984 microns.

The Step Size is typically set to a value based on the depth of field of the objective (which is based on the objective magnification and numerical aperture). The following table lists default step size settings.

Objective Depth of Field Default
Step Size
10x ≈5.0 microns 12
20x ≈2.0 microns 6
40x ≈0.6 microns 3
60x ≈0.4 microns 2

You may wish to refer to the following articles for a step size calculator you can use to accurately determine the step size measurements:

Range

A focus range is used when attempting to acquire focus in a variety of scenarios:

  • Acquiring auto-focus,
  • Fast Stack focus method,
  • Capturing Prediction Points (when using the Predictive focus method),
  • Exhaustive Stack focus method.

The Range specifies the distance (in motor steps) above and below a mid-point. So, a range setting of 100 is equivalent to 201 steps in total (100 motor steps above and 100 motor steps below a mid-point).

The Range is typically set to help the focus algorithm home in on or achieve final focus. The following table lists several common range settings.

Range Setting
(In Steps)
Complete Range
(In Steps)
Range Size
30 61 ≈12.1 microns
78 157 ≈31.2 microns
100 201 ≈39.9 microns
120 241 ≈47.8 microns
500 1,001 ≈198.6 microns

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