So that they can see it clearly if using laser pointer

So that they can see it clearly if using  laser pointer
In domestic and foreign has been widely used in clinical diagnosis, CT since the advent of medical imaging technology is another major achievement. Magnetic resonance imaging and X-ray and CT, will eventually have to get the spatial distribution of the magnetic resonance signal of a body section, and no damage, ionizing radiation and high soft tissue contrast and other advantages, both to reflect the shape, could also reflect function, but also to obtain multi-parameter imaging in order to adapt to different clinical needs. The principle of ultrasonic distance measurement of the acoustic method, is to issue a bunch of ultrasonic transmitter receiver the echo signal reflected by the target object, launch a counter counts from the start to the time of the signal is received in the circuit.  laser pointer  can help users out of the restricted situation when using computer to present and demonstrate documents.
The size of the time value represents the distance of the target, the farther the target, the longer the contrary, the closer the target, the smaller the time value. Can know the distance, and is somewhat similar to laser measuring time and speed of ultrasound, but ultrasound vulnerable to the external environment of the smoke, dust, air density change in the communication process. The measurement principle and the basic structure of the non-contact measurement method. Commonly used non-contact measurement method. Triangulation method. Works by the laser (typically a semiconductor laser) light emitted by the optical system to form a thin parallel beam, shine on the workpiece surface. Back by the surface reflection of light, may be specular, and may also be diffuse reflected light. Users can insert  laser pointer  into a computer case.
Optical measurement method. The principle is the modulated light wave-shaped surface being measured changes, fiber optic light wave parameters with the change of the shaped surface is measured, depending on the size of the measured signal to obtain the shaped surface under test spatial relationships. (3) visual measurement. The video probe targeting the development of the microscope and projection methods. The probe is usually lighting, magnifying glass, CCD camera and monitor. A certain way of lighting, the CCD geometric contours of the object into the optical profiler. (4) computed tomography scan (Computed Tomography, CT) Computed Tomography, the most representative, CT technology is based on the X-ray CT scanner.  laser pointer  is compatible with systems like Windows 98 2000MEXP and so on.
To measure objects on X-ray attenuation coefficient based on a computerized tomography image reconstruction using mathematical methods. (5), magnetic resonance imaging (Magnetic Resonance Imaging, MRI), also known as nuclear magnetic resonance, the theory is based on magnetic resonance theory of nuclear physics, future development in the late 1970s, a new imaging technology.