The core working principle of Leica stereomicroscope is to simulate the binocular disparity of the human eye through two independent optical systems, forming a three-dimensional image of the sample with a sense of three dimensionality, rather than the two-dimensional plane image of traditional microscopes.
The point you are focusing on is crucial. The core difference between stereomicroscopes (also known as stereomicroscopes) and ordinary biological microscopes lies in "stereoscopic imaging". As a representative brand in this field, Leica's principle design is also centered around this core, mainly divided into three parts: optical system, illumination system, and adjustment system working together.
1. Core: Dual path optical system, simulating human eye parallax
This is the fundamental way to achieve stereoscopic imaging. The entire optical system consists of three parts: "objective lens → beam splitter/conversion component → eyepiece", and the left and right sides are completely independent.
Step 1: Objective lens collects sample information
The sample is placed on the stage, and when the light source below or above illuminates the sample, the light carries the detailed information of the sample surface into a pair of parallel objective lenses. The distance between these two objective lenses is close to the distance between human eyes (about 65mm), which will capture sample images from two slightly different angles, forming a "left-right parallax image".
Step 2: Spectral and image conversion processing
Two streams of light carrying parallax enter the microscope's internal beam splitter or conversion lens group, respectively. This component will refract and correct the light rays to ensure that the two paths of light do not interfere with each other, while converting the inverted image of the sample into an upright image (different from the inverted image of a biological microscope, which is more in line with human observation habits).
Step 3: Eyepiece synthesis of stereoscopic image
The processed left and right images ultimately enter the observer's left and right eyes respectively. The human eye and brain will automatically fuse these two images with small parallax, thereby perceiving the three-dimensional sense of the sample and being able to clearly distinguish the high and low, front and back, and depth levels of the sample.
2. Assistance: Flexible lighting system, highlighting sample details
Leica stereomicroscopes are usually equipped with a "transmission+reflection" dual illumination mode (some models can be switched), and the illumination mode is selected according to the characteristics of the sample to ensure clear details.
Reflective illumination (commonly used): The light source illuminates the surface of the sample from above or from the side of the microscope, and the light is reflected by the sample before entering the objective lens. It is suitable for observing opaque and textured samples (such as electronic components, metal parts, insect specimens).
Transmitting illumination: The light source passes through the sample from below the stage (if the sample is semi transparent or thin), and the light directly enters the objective lens, suitable for observing transparent/semi transparent samples (such as thin slices, plastic parts, plant leaves).
3. Adjustment: Zoom and focus system, adapted to different observation needs
By adjusting the components, magnification switching and clarity calibration are achieved to ensure observation flexibility.
Zoom adjustment: The lens group includes a movable zoom lens, and rotating the zoom handwheel can change the distance between the objective lens and the imaging component, thereby continuously adjusting the magnification (usually ranging from 6.5x-45x, some models can be extended to lower or higher magnifications by attaching an objective lens).
Focus adjustment: Rotate the focus handwheel to drive the stage or objective lens up and down, adjust the distance between the sample and the objective lens, and achieve the clearest image. Some Leica models are also equipped with dual knobs for "coarse adjustment+fine adjustment", allowing for quick positioning with coarse adjustment and precise focusing with fine adjustment.