How to Select Board Cameras

How to Select Board Cameras Selecting small footprint size cameras board

Images credits: Tom Depot; Luminera; PI Store

Board cameras, also commonly called printed circuit board (PCB) cameras, are a type of small-footprint video camera that are valued for their general versatility. With optical devices and image sensors mounted directly on a circuit board, manufacturers are able to sacrifice components to provide a space-saving design. Cellular phones and surveillance systems are the most prominent employers of board cameras.

Board Camera Operation

Board cameras are a type of digital camera that have their optical recording devices--aperture, lens, and image sensor--directly attached to a printed circuit board with typical input/output. As such, most board cameras are small in size—registering just ¹/₃" in lens diameter. CCD image sensors are most common, but CMOS and CID sensors are used as well. Without a specified feature, board cameras retain the functionality of video cameras in general. It is recommended you visit GlobalSpec's video camera selection guide for an in-depth look at the capabilities of board cameras.

The display of a board camera is relayed through the I/O of the PCB, typically a display or handheld monitor. Since there are no analog controls, recording options are also controlled through this interface. Attached to a programmable logic controller, board cameras can act as a type of vision system.

Board Camera Quality

Lens

Camera lenses have the greatest influence on the quality of image capture. Because of the small stature of PCB cameras, simple pinhole designs are available. Board cameras also utilize exclusive lens types.

Sized camera lenses determine the angle of focus for the image sensor. Smaller sizes offer a wider angle. Common sizes include: 2.1 mm with 150° field-of-view; 2.8 mm, 115° FOV; 3.6 mm, 92° FOV; 6 mm, 53° FOV; 16 mm, 20° FOV.	Image credit: PC Link
Pinholecameras do not utilize a lens, and are common for surveillance because they can be difficult to detect. Light passes through the aperture onto the image sensor. Smaller apertures result in sharper, but dimmer imaging. Sensitive CCDs are used.	Pinhole example Image credit: Wikimedia
C and CS mount lenses are least common, and TPI threads for mounting. With flange-back distances of 17.5 mm and 12.5 mm respectively, and diameters of 1", these lenses are exclusive unless there is an adapter.	Image credit: Bosch Security

Resolution

Resolution of board cameras is typically rather poor when compared with other larger cameras. A horizontal resolution of 700 TVL is considered exceptional, while more moderately-priced yet capable cameras have resolutions between 380—480 TVL.

Frame Rate

Frame rates for board cameras tend to be about 30 frames per second—the average frame rate for television display. Since board cameras sacrifice some functionality to account for their small footprint, devices capable of recording at over 100 frames per second are considered high-speed. Since board cameras are not used for motion analysis, this is typically more than acceptable.

Shutter Speed/Exposure

By using a digital image sensor, board cameras do not have a shutter in the photogenic film sense of the word, but rather use an electronic shutter that ensures the image sensor records a unified picture. In pinhole cameras, there is one preassigned exposure rate since the aperture cannot be changed. Auto-exposure is often utilized in board cameras.

Sensitivity

Recognizable by the quality of the picture in low-light situations, sensitivity is measured in lux. Black and white board cameras are much more sensitive than their color counterparts, and some monochrome board cameras are capable of recording in environments with as little as .0003 lux which is helpful in surveillance applications. Color board cameras require more illumination to record a quality image. Minimum lux levels for elite-level color board cameras tend to be .3 lux.

Video Output

Most board cameras provide a video feed via 75 Ohms composite output, but other options do exist. With an integral power supply, some board cameras can wireless transmit feeds. Firewire and USB connectivity is common when a memory is connected to the circuit board.

Board Camera Specifications

Camera Mounting

With the camera directly mounted onto the printed circuit board, and the small footprint of these cameras overall, mounting options for board cameras are limitless. Board cameras for surveillance are placed surreptitiously to record unaware subjects. This includes clocks, toys, mirrors, and other hidden camera applications. Board cameras are also commonly used in cell phones, tablet computers, and other mobile devices. Board cameras do not have a common mounting option, such as brackets or stands. Board cameras often incorporate a form of electromagnetic shielding in their housing. This prevents interference from nearby electrical components.

Images credits: Amazon; Ubergizmo

Camera Features

Due to their small size, board cameras cannot offer the same versatility as other video cameras.

These specifications are often optional on video cameras, but depending upon the use they will enhance video quality.

Anti-Blooming: Saturation occurs when the light that is sensed exceeds a pixel's capacity to emit electrons. Excessive charge can bleed into adjacent pixels and cause bright spots or streaks to appear on the image, a condition known as blooming. Anti-blooming gates remove excessive charge and can significantly reduce blooming, but often at the cost of reduced sensitivity.	Anti-blooming before/after Image credit: Astrosurf
Auto-Lens: Auto-lens operation is a mode in which the lens iris automatically adjusts to maintain a predetermined level of light on the image pickup device. Cameras with auto-lens mode may also provide automatic lens focusing.


Dome: Cameras are enclosed in a protective dome made from materials such as acrylic or polycarbonate. Typically, these materials are optically-corrected for accurate image capture. This can create a tamper-proof housing common for security use.	Image credit: Jarrett Security
Gain Control: Automatic gain control (AGC) uses electronic circuitry to increase video signals in low-light conditions. This can introduce noise and, subsequently, graininess in the picture. Typically, AGC is disabled and specifications are presented with this feature turned off.
Gamma Correction: Gamma is the nonlinear relationship between the video signal level and the subsequent image element brightness. Gamma correction compensates for this nonlinearity in order to render the image true in color while providing intensity to the original object.
High Definition: High definition is a video standard that has higher picture sharpness, larger picture, more colors, and higher quality sound than regular video standards. Board cameras are not usually capable of the true HD video definition of 1,280 x 720 pixels.

Low-Light Camera: These are meant to be used in dark situations where an otherwise suitable camera will not reach an exposure level capable of capturing an image. The cameras contain image sensors that are exceptionally perceptive of subtle light sources.
Machine Vision Sensors: Machine vision sensors have the capability to analyze events captured by its camera, and alert operators or make decisions based on the information collected. These are also called smart cameras. If they are not uniform machines, the camera is typically linked to a computer interface via a FireWire, USB, or Ethernet connection.
Outdoor Rated: Outdoor-rated devices are designed to withstand outdoor temperature variations, rain, snow, and other weather conditions.

Progressive Scan: This is a CCD design that allows acquisition of both even and odd fields at the same time. Each pixel contains information from one complete frame. This technology allows high resolution without the use of a mechanical shutter. Progressive scan cameras are used for image acquisition of rapidly moving objects and accurate dimensional measurements.


Zoom: Cameras are designed with a feature that allows the device to closely focus on distant objects. Optical zooms offer better resolution than digital zooms.

Board Camera Applications

Board cameras are an inexpensive way to incorporate video cameras into existing devices or to position a camera with limited mounting options. Their small stature makes them exceptionally versatile, and they will meet the video recording requirements of many industrial applications. Common examples of board cameras include hidden cameras and surveillance modules. Board cameras are also prevalent in cellular phones and other mobile devices like iPods and tablet computers.