Classification of industrial lenses according to field of view size

The angle formed at the vertex of an industrial lens, defined by the object-image extending through the lens's maximum range, is known as the field of view (FoV). This means that the FoV is the area that a lens can capture when connected to a CCD camera. The size of the FoV determines the range of an optical instrument: the larger the field of view, the smaller the optical magnification.

Types of Camera Lenses

Industrial lenses can be divided into several types based on the size of the field of view: small-field lenses, standard lenses, wide-angle lenses, ultra-wide-angle lenses, telecentric lenses, and microscope lenses, among others.

1. Standard Lenses Standard lenses have a viewing angle of approximately 50 degrees, with focal lengths that closely match the diagonal length of the camera's format. This resembles the natural field of view of the human eye when the head and eyes are stationary. In 35mm cameras, typical standard lenses have focal lengths of 40mm, 50mm, or 55mm. Larger formats like 120mm cameras use lenses with focal lengths around 80mm or 75mm.

2. Wide-angle and Ultra-wide-angle Lenses These lenses have a viewing angle of over 90 degrees, suitable for capturing large scenes at close distances, emphasizing strong foreground elements, and providing intense perspective. In a 35mm camera, a typical wide-angle lens has a focal length of 28mm, offering a viewing angle of 72 degrees. A 120mm camera with a 50mm or 40mm lens is equivalent to a 35mm camera with a 35mm or 28mm lens.

3. Telephoto Lenses Telephoto lenses are designed for capturing distant subjects. They have smaller depth of field, allowing the background to blur, thus highlighting the subject. In 35mm cameras, telephoto lenses can be categorized into three groups: below 135mm as medium telephoto, between 135mm and 500mm as long telephoto, and over 500mm as ultra-telephoto. In 120mm cameras, a 150mm lens is comparable to a 105mm lens in a 35mm camera.

4. Reflective Telephoto Lenses Reflective telephoto lenses use mirrors to create the image, which leads to a more compact design. However, these lenses cannot accommodate an aperture, so exposure adjustments must be made using the shutter speed.

5. Fisheye Lenses and Reflective Lenses Fisheye lenses, with viewing angles of about 180 degrees, create extreme wide-angle images with significant distortion. Reflective lenses (also known as catadioptric lenses) offer a shorter and lighter form factor compared to traditional telephoto lenses.

6. Zoom Lenses Zoom lenses have adjustable focal lengths, allowing them to cover a range of magnifications. This versatility enables zoom lenses to substitute for several fixed-focus lenses. They can be manually or electrically adjusted, providing flexibility for varying distances.

7. Macro Lenses, Perspective Adjustment Lenses, and Bellows Lenses Macro lenses, or micro lenses, allow for extremely close focus. Perspective adjustment lenses, also known as tilt-shift lenses, can adjust perspective effects or depth of field. Bellows lenses use a flexible connection, providing added adaptability for close-focus photography.

8. Pinhole Lenses These lenses have a very narrow diameter, often just a few millimeters, and can be concealed within an object or setting. They are ideal for special applications, such as industrial furnaces or mental institutions, where standard lenses could be easily damaged or detected.

Optical Formulas

To determine the desired field of view (FoV) and working distance (WD), the following formulas can be used to calculate the appropriate focal length (f):

• Focal Length (f): �=��×Target Size (H or V)FoV (H or V)f=FoV (H or V)WD×Target Size (H or V)​

• Field of View (FoV): FoV (H or V)=��×Target Size (H or V)�FoV (H or V)=fWD×Target Size (H or V)​

• Optical Magnification: Optical Magnification=Target Size (H or V)FoV (H or V)Optical Magnification=FoV (H or V)Target Size (H or V)​

• Working Distance (WD): ��=�×Target SizeFoV (H or V)WD=FoV (H or V)f×Target Size​