The sensor format or image sensor size of an industrial camera refers to the physical size of the photosensitive area of the camera's internal image sensor (CMOS or CCD). It is a core parameter of industrial cameras, directly influencing key aspects of the imaging system, such as field of view, resolution matching, and lens selection.

Simply put: just like the size of the "negative" of a traditional film camera, the target surface is the actual size of the "electronic film" of a digital camera.

How do I calculate target surface dimensions? (Target surface dimensions are typically expressed and calculated as follows:)
Direct dimensions (unit: mm):

1. This is the most direct and accurate method, usually expressed as width (W) x height (H), in millimeters (mm).
2. Calculation principle:
Target surface size = pixel size x number of active pixels in that direction
Width (W) = pixel width (μm) * horizontal active pixel number (H_pixels) / 1000 (convert μm to mm)
Height (H) = pixel height (μm) * vertical active pixel number (V_pixels) / 1000
3. Example: A camera has a pixel size of 3.45μm x 3.45μm and a resolution of 2448 x 2048.
Width W = 3.45 μm * 2448 / 1000 = 8.4456 mm (≈ 8.45 mm)
Height H = 3.45 μm * 2048 / 1000 = 7.0656 mm (≈ 7.07 mm)
Thus, the camera's image surface measures approximately 8.45 mm x 7.07 mm.

Optical Format (unit: inches):
1. This is a historical notation (derived from early camera tubes) expressed in inches with quotation marks (e.g., 1/1.8", 1/2.5", 1", 2/3", etc.).
2. Key Point: This inch number is not the actual diagonal length of the sensor! It is a code for the "optical format." The actual diagonal length is approximately 2/3 of the nominal value.
3. Calculating the actual diagonal size (approximately):
Actual diagonal length (mm) ≈ Nominal optical format (inches) * 16 mm
Why 16? This is a historical conversion factor (a 1-inch optical format corresponds to an actual diagonal of approximately 16 mm).
4. Example:
Nominal 1" image surface: Actual diagonal ≈ 1 * 16 mm = 16 mm
Nominal 2/3" image surface: Actual diagonal ≈ (2/3) * 16 mm = 10.67mm
Nominal 1/1.8" target: Actual diagonal ≈ (1/1.8) * 16mm ≈ 8.89mm
5. Note: The exact dimensions of sensors with the same nominal format (e.g., 1/1.8") may vary slightly between manufacturers and over time.

Diagonal length (unit: mm):
1. The sensor's diagonal length (mm) is sometimes given directly. Knowing the diagonal length and aspect ratio (usually 4:3, 3:2, or 1:1) allows you to deduce the width and height.

What key factors does sensor size determine?
Field of View (FoV):
1. This is the most direct and important factor. At the same working distance (WD) and lens focal length (f), the larger the sensor, the wider the field of view (FoV).
2. Formula: FoV (W or H) = Sensor Size (W or H) * WD / f
3. For example, at the same distance and focal length, a camera with a 1" sensor has a much larger field of view than one with a 1/2.5" sensor.

Lens Compatibility:
1. Lens Image Circle: The diameter of the largest circular area that a lens is designed to clearly image. The lens's image circle diameter must be greater than or equal to the diagonal length of the camera's image surface. Otherwise, severe vignetting will occur at the edges of the image and resolution will be reduced.
2. Selection Guidelines: The lens you choose must indicate its maximum supported sensor format (e.g., "Designed for 1" sensor," "Compatible up to 2/3" sensor"), and this value must be greater than or equal to the size of your camera's image surface (optical format or actual diagonal). Using a lens with a small image circle on a camera with a large image surface will result in poor image quality at the edges.

Resolution vs. Pixel Density Tradeoffs:
1. At the same pixel resolution (e.g., 5 megapixels):
The larger the image surface, the larger the individual pixel size (or it can be made larger).
The smaller the image surface, the smaller the individual pixel size (or it must be very small to achieve high resolution).
2. Impact:
Large image surface + large pixels: Generally, they offer better low-light performance (higher sensitivity) and dynamic range, and may also have better noise control. However, they may also increase camera size and cost.
Small image surface + small pixels: They can achieve high resolution in a smaller physical space, resulting in a more compact camera and potentially lower cost. However, they require extremely high lens resolution (MTF), may limit low-light performance and dynamic range, and may also increase noise.

Depth of Field (DoF):
1. At the same aperture (f/#) and field of view (FoV) (this means using lenses of different focal lengths to maintain the same FoV):
A camera with a large image area typically requires a lens with a longer focal length to achieve the same field of view as a camera with a smaller image area.
Depth of field is inversely proportional to the square of the focal length. Therefore, a camera with a larger image area using a lens with a longer focal length will have a shallower depth of field (more pronounced background blur) at the same aperture and FoV.
2. If the focal length and aperture remain the same, a camera with a larger image area will have a wider field of view, but its depth of field is theoretically the same as a camera with a smaller image area at the same focal length and aperture (smaller field of view). However, in practice, to achieve a specific field of view, the image area size directly affects the required lens focal length, which indirectly affects the depth of field.

Lens Resolution Requirements:
1. To fully utilize the camera sensor's resolution, the lens's modulation transfer function (MTF) at the corresponding spatial frequency (determined by pixel size) must be sufficiently high. The smaller the pixel size (meaning that to achieve high resolution, the image surface can be smaller or larger, but the pixel density is high), the more stringent the lens resolution requirements. High-resolution cameras with small image surfaces require extremely sharp lenses.