ACCU-SCOPE EXM-150 Darkfield Annulus: Installation and Operation

Introduction

This document provides instructions for the installation and operation of the ACCU-SCOPE EXM-150 Darkfield Annulus.

Note: If purchased with the microscope, the EXM-150 microscope should arrive with the darkfield annulus (stop) already installed.

Note: The EXM-150 darkfield annulus is designed for use only with models of the EXM-150 series microscopes equipped with Abbe condensers (CAT# EXM-151, EXM-151-T, EXM-151-VT, and any of these models with digital cameras).

Important: The darkfield annulus is effective with 4x and 10x objectives on the specified EXM-150 models. It is not recommended for use with 40x or 100x objectives.

Visual Description: The document includes comparative images of a nematode specimen, illustrating the difference between brightfield (light background) and darkfield (dark background) microscopy. An image of the darkfield annulus itself is also provided, identified by CAT# 150-3220.

The Principle of Darkfield

Darkfield illumination creates a dark background for the specimen, contrasting with brightfield illumination which produces a bright background. In brightfield (BF) observation, light passes through the specimen and is collected by the objective. Color and contrast are transmitted with the light, resulting in a colorful image against a light background.

In darkfield, light is directed towards the specimen at a high angle. If no specimen is present, this light misses the objective, creating a dark background. When a specimen is present, it scatters light in various directions, with some scattered light entering the objective and becoming visible. While some color may be observed, darkfield often appears monochromatic. This method is particularly useful for unstained specimens or those with minimal coloration.

Diagram Description: A diagram illustrates darkfield illumination. It depicts a light source below a condenser, which angles light upwards. A slide with a specimen is placed on a stage. The darkfield annulus is positioned below the condenser, blocking direct light. Light scattered by the specimen is shown entering the objective lens above.

Installation

When ordered with the microscope, the darkfield annulus is pre-installed. No separate installation is required.

Operation

1. Turn on the microscope. Adjust light intensity for comfortable observation.
2. Begin with the darkfield annulus in the “out” position, rotated out of the light path. It should move freely in one direction and stop in the other.
3. Place a specimen on the stage and focus using the 4x objective.
4. Open the condenser iris using the iris lever. Adjusting the lever will change image brightness and texture/contrast (contrast increases as the iris closes).
5. Swing the darkfield annulus into the “in” position. The specimen field should appear dark, with the specimen and any particles appearing bright against the dark background.
6. Adjust the iris position to optimize the view. With practice, these adjustments can be made while observing.
7. Switch to the 10x objective and adjust the iris as needed for optimal imaging.
8. Move the darkfield annulus to the “out” position for brightfield observation. Adjust the iris to achieve the desired contrast.

Visual Description: The operation section includes images showing the microscope stage with the iris lever and the darkfield annulus in both the "in" and "out" positions.