Styles, Features, and Capabilities of Different Types of Industrial Borescopes
Industrial borescopes (also called industrial endoscopes or inspection cameras) are available in a range of different styles, with different interfaces to connect with other devices, and with different specialized capabilities to suit different kinds of inspection duties.
Before we discuss the different kinds of borescopes, however, let's take a moment to look at a the history of borescopes.
The first borescopes were purely optical devices that used lenses and mirrors. They enabled the inspector to see the area being inspected by peering through an eyepiece, much as one would look through a telescope. One of their earliest uses was by military artillery mechanics to inspect inside the barrels of cannons and other artillery.
The next stage in the evolution of borescopes used fiber optics to send light to the target being inspected, and to send the image back to the inspector's eyepiece. Most of these fiber optic borescopes could also be fitted with film (and later digital) cameras to take still and motion pictures of the areas being inspected. Fiber optic scopes are still used today for applications where the scope diameter must be extremely small. Fiber optic borescopes can be made with diameters as small as 0.35 millimeter (less than 1/64 of an inch).
Most borescopes sold today are purely digital devices that use LED's on the ends of the probes to provide the light, and CCD sensors to capture the images. Digital borescopes can produce pictures and videos of remarkably good quality, at a much lower cost than fiber optic scopes. Their main disadvantage is that they require a much larger diameter to accommodate the CCD image sensor and the LED lights. At the time of this writing, the smallest-diameter digital borescopes that produce decent-quality images weigh in at about 5.5 millimeters in diameter.
Now that the history lesson is over, let's take a look at some of the different types and styles of borescopes available today, along with their capabilities and typical applications.
Self-Contained vs. Headless Borescopes
Self-contained (or "all-in-one") borescopes can be broadly-defined as borescopes that have a screen and can be used independently, without needing to connect them to any other device. You literally can take a self-contained borescope out of its box, charge the battery, and use it. No additional devices, drivers, or software are needed.
Most self-contained borescopes record inspection images and video to removable media, most commonly a Micro SD card. Other borescopes must be connected to computing devices using a USB cable to transfer images and video, usually without needing any drivers (they're typically recognized as USB mass-storage devices, like a flash drive would be). Many borescopes can be used either way.
Most professionals prefer self-contained borescopes because they're more convenient than headless borescopes that require a phone or tablet to use as a screen. They also avoid the risk of damaging an expensive phone or tablet by using it in a harsh, cramped, dirty, or greasy environment such as the crawl space of a house or under the hood of a vehicle.
Headless borescopes can be broadly-defined as those which lack screens and must be connected to another device (generally a smartphone, tablet, or laptop) while being used, either by a USB cable or wirelessly. Most also lack any way to independently save videos other than to the host device to which they're attached.
The biggest advantage to headless borescopes is that they're much less expensive than self-contained borescopes because they don't have screens. Most of the USB ones also don't have batteries (they're powered by the host device's USB port). Headless borescopes are also popular with people who typically use another device while doing their jobs anyway, such as car mechanics who run OBD2 diagnostic software on tablets or laptops while working on cars.
Headless borescopes connect to their host devices using either USB, WiFi, or Bluetooth. Some can connect using only one of these interfaces. Others can use two or all three of them. Most (but not all) of the WiFi ones create their own access point, so an existing wireless network usually is not needed.
The disadvantages of headless borescopes are that they may require drivers and software to be installed on the host device (typically a laptop, phone, or tablet); may not work with all devices; may suddenly stop working on a given host device due to operating system updates; and require subjecting the host device to potential damage when used in cramped, dirty, hostile environments.
Rigid vs. Semi-Rigid vs. Flexible Borescopes
Rigid borescopes cannot be bent at all. They're mainly popular with people who have only one inspection task that they need the borescope to do: and that one task always gives them direct, unobstructed, front-facing access into the void being inspected. Someone who uses a borescope only to inspect inside gasoline engine cylinders, for example, might find a rigid borescope more convenient. If you can get a socket wrench onto a spark plug, then you can get a rigid borescope through the spark plug hole. Rigid borescopes are also used to inspect inside the barrels of firearms and artillery.
Semi-rigid borescopes can be used straight or can be bent to some extent, which is usually quite a bit, and hold their position pretty well while in use. They're a good choice when you have a general idea of the shape of the void being inspected, and there's no need to maneuver the device through sharp turns. Semi-rigid borescopes are by far the most popular general-use industrial endoscopes because of their versatility.
Flexible borescopes have very little rigidity and are able to be snaked through tight bends. They can also be pulled through a pipe or conduit with a string or wire. Flexible borescopes are especially popular with aircraft mechanics, who use them to inspect the inside of turbine engines; plumbers who use them to find clogs in sink, shower, and bathtub drains; and electricians who use them to inspect inside electrical conduit (with the power turned off, of course).
Articulating borescopes can be rigid, semi-rigid, or flexible. They have remotely movable tips that allow the user to control the direction the tip of the probe is pointed in. This not only allows the operator to control the area being viewed, but also allows a skilled operator to guide a flexible or semi-rigid borescope through internal passageways by pushing and wiggling the scope and manipulating the tip.
Traditionally, articulating borescopes have been controlled with mechanical cables that run through the probe that pivot the head when pushed or pulled. Cable-controlled articulating borescopes can be of one-way, two-way, or four-way design:
- Articulating borescopes with one-way tips are mainly useful for changing the angle of view from 0 degrees (straight ahead) through 90 degrees, with the direction of view around the scope's centerline controlled by twisting the probe itself.
- Two-way articulating borescopes can change the direction of view 90 degrees left and right (or up and down) from the 0-degree straight-ahead view.
- The tips of four-way articulating borescopes can be moved in 90 degrees up, down, left, or right, but not necessarily in combination. In other words, if you're looking 90 degrees up, you may have to return the scope to 0 degrees before looking right.
Increasingly, modern articulating borescopes use joysticks and electronic servo motors to move the tip in any direction the operator wants. As the technology of miniaturization progresses, I expect that we'll see more and more joystick-controlled articulating borescopes.