Resolution

Detail recognition: observe the details of the target object in the thermal imaging image. Under normal circumstances, a high-quality thermal imaging night vision scope can clearly distinguish the outline, shape and key features of the target. For example, when observing a human-shaped target in the distance, you should be able to see the general outline of the limbs, head and other parts; for animals, you can distinguish the ears, tail and other parts. If the image is blurry and these basic details cannot be distinguished, it may be that the resolution is low or there is a problem with the equipment.

Minimum resolvable unit: check whether smaller targets or tiny parts of the target can be distinguished. A good thermal imaging scope can distinguish closely arranged objects or small parts on the target object. For example, when observing a flock of birds, you can distinguish the shape of a single bird; or when viewing equipment with small parts, you can see the distribution of the parts. Generally speaking, the higher the resolution, the smaller the minimum unit that can be distinguished, and the better the image quality. Common thermal imaging night vision scopes have resolutions of 384×288 pixels, 640×480 pixels, etc. The higher the pixels, the richer the resolvable details are usually.

Thermal sensitivity

Temperature difference detection capability: judged by observing the distinction between objects of different temperatures. Normal thermal imaging equipment should be able to keenly perceive the temperature difference between the target and the background, and between different parts of the target. For example, in the early morning, when observing a hare in the grass, the body temperature of the hare is higher than the surrounding grass. A high-quality scope can clearly show the outline of the hare and reflect the temperature changes caused by the heat dissipation differences in different parts of the hare's body (such as the abdomen and back). If the thermal sensitivity is insufficient, the target and the background may merge and become difficult to distinguish.

Weak thermal signal display: try to observe targets with lower temperatures or weaker thermal signals. For example, in an indoor environment with a relatively balanced temperature, observe the weak thermal signals of the heat dissipation vents of electrical equipment. A normal thermal imaging night vision scope can detect these weak heat changes, so that the heat dissipation vents appear in the image with a different color or brightness from the surrounding walls. If these weak thermal signals cannot be displayed, it may be that the thermal sensitivity is not up to standard.

Image uniformity

Entire field of view inspection: check whether the thermal imaging image is uniform across the entire field of view. Under normal circumstances, the brightness, contrast and color (if there is a color mode) of each area of the picture should be relatively consistent. There will not be a situation where the center area is clear and bright, and the edge area is blurred and dim. You can aim the scope at a large area target with uniform temperature distribution, such as a white wall, to observe whether the image can maintain good quality throughout the field of view.

No obvious noise and artifacts: High-quality images should be relatively clean, without excessive noise and artifacts. Noise appears as random bright or dark spots on the image, which will interfere with the observation of the target. Artifacts are unreal shapes or patterns that appear in the image, such as stripes, shadows, etc. When observing simple hot targets, such as simple-shaped objects such as thermos, there should be no strange stripes or deformed shapes.

Color accuracy and stability (if it is color thermal imaging)

Color restoration: For color thermal imaging night vision scopes, observe whether the color can accurately reflect the temperature of the target. Generally speaking, there are conventional ways of expressing colors, such as in white-hot mode, the high-temperature part is usually displayed as white or bright yellow, and the low-temperature part is displayed as black or dark blue. If the correspondence between color and temperature is confused, such as the high-temperature part is displayed as blue and the low-temperature part is displayed as red, it means that there is a problem with color accuracy.

Color consistency: During the observation process, the color of the image should remain stable. There will be no sudden color changes, flickering, or unnatural color transitions. For example, when observing an object that is continuously heated, its color should remain unchanged within a reasonable range, rather than frequently switching between red and green.

Image stability

Screen jitter: When holding a thermal imaging night vision scope, although there will be a certain degree of jitter, a normal device should have an anti-shake mechanism or a fast enough refresh rate to reduce the impact of jitter on the image. If the image shakes violently and the target cannot be observed stably, it may be that the device has no anti-shake function or the anti-shake function is faulty.

Refresh rate perception: The refresh rate determines the speed of image update. When observing a moving target, the impact of the refresh rate can be clearly felt. A normal thermal imaging scope has a high refresh rate. When observing fast-moving objects (such as running animals), it can smoothly display the movement trajectory of the object without ghosting. If the image is found to have obvious ghosting or is not updated in time, it may be a problem of low refresh rate.