JPH03257389A - Track displaying device - Google Patents

Abstract

PURPOSE:To reduce consumption of power necessary for degaussing by providing a moving distance detecting means, a course detecting means and a degaussing instruction signal generating device which determines a shift of a moving body exceeding a prescribed moving distance and a prescribed angle and generates a degaussing instruction signal. CONSTITUTION:A program to be executed by CPU 1 is written before hand in ROM 2, and RAM 3 is used as a working area on the occasion of storing a course taken at the time of the previous degaussing and calculating the amount of shift of the course etc. and for other purposes, while VRAM 4 stores display data. A video output circuit 5 converts an output signal of the VRAM 4 into a video signal and outputs it to CRT 6. A display control circuit 7 estimates a read-out address of the VRAM 4 in accordance with a raster scan of the CRT 6. A degaussing circuit 9 makes a degaussing current flow through a degaussing coil incorporated in the CRT 6, and the CPU 1 gives it a degaussing instruction signal through an interface 8. A position measuring device 11 is constructed of a loran C receiver and others and determines the position of a moving body as data on the latitude and longitude. The CPU 1 is connected to the bus line of these elements and exercises general control over the whole of a track displaying apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a track display device that displays a track obtained by sequentially measuring the current position of a ship on a color CRT.

(b) Prior Art Generally, in a color CRT display device, a cathode ray tube is magnetically shielded to prevent color shift or uneven color from occurring due to the influence of the earth's magnetic field on electron beams. Furthermore, a degaussing coil and a degaussing circuit that flows an alternating current damping current through the degaussing coil are incorporated to prevent the iron plate for magnetic shielding from being magnetized. Normally, this degaussing circuit is activated when the device is turned on or off, so as not to affect the actual display screen.
It is configured to operate only for a certain period of time as shown above. Therefore, normally, once convergence is performed, correct color display without color shift or color unevenness is maintained. but,
When a color CRT is used as a display for electronic equipment mounted on a moving object such as a ship or vehicle, such as a track display device, the direction of the color CRT changes while the equipment is in use, that is, during display, so the geomagnetic field is affected. In order to avoid such magnetization during display, for example, a degaussing circuit is activated during the vertical retrace period of raster scanning. I try to do that.

(C) Problems to be Solved by the Invention However, with the method of demagnetizing during display as described above, a large current is required for demagnetization, which not only increases power consumption but also causes noise generated by the demagnetization of the main unit. electronic equipment and other electronic equipment.

SUMMARY OF THE INVENTION An object of the present invention is to provide a track display device that eliminates the above-mentioned conventional problems by automatically performing demagnetization only when necessary.

(d) Means for Solving the Problems Color shifts and color unevenness in color CRTs are caused by changes in the direction (azimuth) of the color CRT, which in turn changes the degree of influence of the earth's magnetic field. I want a color CRT
It is only necessary to perform demagnetization when the orientation changes enough to cause color fading or color unevenness. The present invention focuses on this point.

The present invention provides a track display device that includes a color CRT and a degaussing circuit that demagnetizes the color CRT, measures the position of a moving object at each point in time, and displays the position on the color CRT. a moving distance detecting means for detecting a course of the moving object from a change in the position of the moving object; a course detecting means for detecting the course of the moving object from a change in the position of the moving object;
The present invention is characterized in that a degaussing instruction signal generating means is provided which determines that the fixed angle base has changed and generates a demagnetizing instruction signal to the degaussing circuit.

(e) Function In the track display device of the present invention, the moving distance detecting means determines the moving distance of the moving object from the position of the moving object at each measured time point. Further, the moving object course detecting means determines the current course from the position of the moving object at each measured time point.

When the moving body moves a certain distance and its course changes by a certain angle or more, the demagnetization instruction signal generating means generates a demagnetization instruction signal to the demagnetization circuit. Therefore, demagnetization is performed only when the moving body carrying the track display device moves a certain distance or more and its course changes by a certain angle. For example, when the moving body is a ship and is at anchor, even if the detected course changes significantly due to waves or the like, the change in position is slight, so frequent demagnetization is not performed. In this way, even though the electronic device is mounted on a moving object such as a ship or a vehicle, the Ln is turned off only when necessary, so wasteful power consumption and generation of noise can be suppressed.

(f) Embodiment A block diagram of a track display device according to an embodiment of the present invention and its processing procedure are shown in FIGS. 1 and 2. In FIG. 1, each of the sections shown after the CPU is connected to the lotus line and centralizes control of the entire track display device.

A program to be executed by the CPU 1 is written in the ROM 2 in advance. The RAM 3 is used as a working area for storing the course from the previous demagnetization and calculating the amount of change in the course. VRAM4 stores display data. The video output circuit 5 is connected to this VRAM
4 is converted into a video signal and output to the CRT 6. The display control circuit 7 specifies successive addresses of the VRAM 4 in response to raster scanning of the CRT. The degaussing circuit 9 is a circuit that supplies a degaussing current to a degaussing coil incorporated in the CRT 6, and the CPU 1 gives a degaussing instruction signal via the interface 8. The positioning device 11 includes a Loran C receiver, a GPS receiver, etc., and determines the position of a moving object as latitude and longitude data. The CPUI reads the measured position data via the interface 10. The key manual device 3 is equipped with a key switch for instructing forced degaussing and a key switch for setting a threshold value for course change for automatic degaussing. The CPUI reads the key operation contents via the interface 12. The interface 14 serves as an interface for outputting position data measured by the positioning device 11 and course data obtained through calculation processing by the CPU to an external device.

The track display device performs processing according to the procedure shown in FIG. First, immediately after the power is turned on, a degaussing instruction signal is forcibly given to the degaussing circuit 9 (nl). Thereafter, the presence or absence of a key operation is detected, and if any key operation is performed, the operated key is read (identified) (n2→n3). Next, processing is performed according to the operated key. For example, if a key operation is performed to set a threshold value S for a course change and a threshold value for a distance change when performing automatic demagnetization, which will be described later, the operated values are read and stored (n4). In addition, if the key operation is forcibly degaussing, a degaussing instruction signal is output to the degaussing circuit 9 (
n5).

While key personnel are on standby, when it is time to take a measurement, first read the current own ship position from the positioning device 11 (n6→
n7). Next, the moving distance d is calculated from the relationship between the past own ship position (at the time of demagnetization) and the current own ship position (n
l). It is determined whether this moving distance d exceeds a predetermined moving distance threshold (n9). If the travel distance exceeds the threshold, calculate the current course Co from the relationship between the past own ship position and the current own ship position, and calculate the difference from the course C1 when the previous demagnetization was performed as ΔC. (n1
0→n11). Then, this Kushiro change ΔC is the threshold value S
It is determined whether or not the value has exceeded (n12). If the threshold S is exceeded, the current Sl path Co is stored as 01, and a degaussing instruction signal is output to the degaussing circuit 9 (n13
>n14). It also remembers the clear position where demagnetization was performed (
n15). Thereafter, the previous track and current own ship position and course are displayed (n16). Note that if the course change ΔC is less than the threshold value S, demagnetization is not performed (n12→n1
6...).

(g) Effects of the Invention According to this invention, the course of the moving body, that is, the color C
Since demagnetization is automatically performed only when the direction of the RT changes, the power consumption required for demagnetization can be significantly reduced unless the course of the moving object changes frequently and significantly. Further, as a result, less noise is generated, and there is no adverse effect on the track display device and other electronic devices. Furthermore, since changes in the orientation of the color CRT are determined using the functions originally provided as a track display device, there is no need for a special orientation measuring device such as a compass.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a track display device according to an embodiment of the present invention, and FIG. 2 is a flow chart of the processing procedure of the same device.

Claims (1)

[Claims] (1) A track display device that is equipped with a color CRT and a degaussing circuit that demagnetizes the color CRT, measures the position of a moving object at each point in time, and displays the position on the color CRT. A moving distance detecting means for detecting a moving distance, a course detecting means for detecting a course of a moving object from a change in the position of the moving object, and a course detecting means for determining that the moving object has moved more than a certain distance and the course of the moving object has changed more than a certain angle A track display device characterized in that a degaussing instruction signal generation means for generating a demagnetizing instruction signal to the degaussing circuit is provided.