Information in this article applies to:
Article ID: NDS1154 — Created: 23 Feb 2018 — Reviewed: 8 Aug 2021
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?
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.
The objective moves up and down under the power of a stepper motor. The stepper motor moves in increments called steps. All Step Size settings specify the number of motor steps to move the objective.
The following table lists the single step measurement for all uScope models.
|M2B, M2C, M2D
The Step Size used in the Device Settings 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.
|Depth of Field
Refer to the following knowledge base articles for a step size calculator you can use to accurately determine step measurements:
A focus range is used when attempting to acquire focus in a variety of scenarios:
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 achieve final focus. The following table lists several common range settings.
Be cautious when extending the range of auto-focus. Typical slides have a cover slip that is 170µm thick. Extending the range of auto-focus too much can cause the uScope to focus on dirt and debris on top of the cover slip rather than on the specimen.