MXPA98003100A - External magnetic field correction device and catodi ray tube deployment device - Google Patents

Abstract

An external magnetic field correction device capable of preventing malfunction of the external magnetic field correction device due to the operation of a demagnetizing circuit, judging that an abnormality has occurred when an output of an external magnetic field detector is not less a predetermined value, and consequently interrupting the slope adjustment process, and which is capable of limiting irregularities of the slope current in the operating current of the magnetic field correction device to a predetermined value or a lower value, adjusting a slope value to cause the correction current to be supplied to an external magnetic field correction coil when an external magnetic field around a CRT is zero at a regular value or menu

Description

EXTERNAL MAGNETIC FIELD CORRECTION DEVICE AND CATHODIC RAY PIPE DEPLOYMENT DEVICE BACKGROUND OF THE INVENTION The present invention relates to an external magnetic field correction device for automatically correcting external magnetic field influences caused by geomagnetism in the image quality, and to a CRT (cathode ray tube) deployment device employing the same. Figure 1 is a block diagram showing a constitution of a conventional external magnetic field correction device of a CRT deployment device as described, for example, in Japanese open patent application No. 2-214288 (1990 ). In Figure 1, 1 denotes a CRT (cathode ray tube), 2 a coil of magnetic field correction of horizontal direction (the direction along the axis of the tube), 3 a magnetic field correction coil of vertical direction (the direction orthogonal to the axis of the tube), A-a magnetic field sensing element of horizontal direction, 5 a polarization circuit, 6 an amplifier circuit, 7 a counter-tension generator circuit, 8 an adder to which an output of the circuit enters amplifier 6 and an output of the counter-tension generator circuit 7, 9 a filtering circuit to which an output of the adder 8 is input, and 10 a current driver circuit for the correction of the horizontal magnetic field to which an output of the circuit is inputted. filtered 9 and whose output is supplied to the magnetic field correction coil of horizontal direction 2. On the other hand, 11 denotes a magnetic field detector element of dir. vertical section, 12 a polarization circuit, 13 an amplifier circuit, 14 a counter-tension generator circuit, 15 an adder to which an output of the amplifier circuit 13 and an output of the counter-tension generator circuit 14, 16 are fed to a filter circuit which is input an output of the adder 15, and 17 a current driving circuit to which is input an output of the filtering circuit 16 and whose output is supplied to the magnetic field correction coil of vertical direction 3. Figure 2 is a block diagram showing a constitution of a device conventional external magnetic field correction of a CRT deployment device as described, for example, in Japanese open patent application No. 60-118879 (1995). In Figure 2, 4 denotes a horizontal direction magnetic field detecting element, 37 a memory (non-volatile memory) for storing a magnetic field strength detected by the horizontal direction magnetic field detecting element 4, and magnetic field intensity difference to detect a difference in magnetic field strength at a predetermined position stored in the memory 37 and in a different position detected by the horizontal direction magnetic field detecting element. The output of the magnetic field intensity difference detector 20 is input to the current driver circuit for the horizontal magnetic field correction 10, and the output of the current driver circuit for the horizontal magnetic field correction 10 is supplied to the coil of the magnetic field. Correction of magnetic field of horizontal direction 2. The operations will now be explained. In FIG. 1, the CRT 1 of the deployment device is arranged in a magnetic field which is a combination of a magnetic field generated by the magnetic field correction coil of horizontal direction 2 and the magnetic field correction coil of vertical direction 3, as well as an external magnetic field. The magnetic field detector element of horizontal direction 4 is arranged within this magnetic field to convert an intensity and polarity of the magnetic field into electrical signals. The output voltage of the magnetic field detector element of horizontal direction 4 arranged in the magnetic field corresponds to a sum of the horizontal components of the external magnetic field, of the magnetic field in which the horizontal direction magnetic field detecting element 4 is disposed and a magnetic field generated by the magnetic field correction coil of horizontal direction 2. Since the output of the horizontal direction magnetic field detecting element 4 is small, this is amplified by the amplifier 6. The output voltage generating circuit 7 generates a direct current whose absolute value is equal to, and whose polarity is opposite to that of a detected and amplified voltage emitted by the amplifier circuit 6. when the magnetic field intensity of the area in which the horizontal direction magnetic field detector element 4 is disposed is zero. The voltage output detected and amplified by the amplifier circuit 6 when the intensity of the magnetic field in which the horizontal direction magnetic field detector element 4 is arranged is zero, varies for each individual product due to irregularities such as irregularities in the manufacture of the horizontal directional magnetic field detector element 4, irregularities in the positional relationship between the horizontal directional magnetic field detector element 4 and magnetic bodies that are used to be used, for example, in parts that make up a case, or irregularities in parts that make up a frame, or irregularities in parts that make up the amplifier circuit. Therefore, the counter-tension generator circuit 7 needs to carry out the adjustment for each individual product. The adder 8 emits a value of zero when the intensity of the magnetic field of the area in which the horizontal direction magnetic field detecting element 4 is arranged is zero, a negative value to a magnetic field generated when the field correction coil horizontal directional magnetic field 2 is supplied with positive current preliminarily prescribed, and a positive value to a magnetic field generated when the magnetic field correction coil of horizontal direction 2 is supplied with preliminarily prescribed negative current. The output of the adder 8 is filtered by the filtering circuit 9. The output of the filtering circuit 9 is input to the current driving circuit for the horizontal magnetic field correction 10. The current driving circuit for horizontal magnetic field correction 10 it is constituted by a circuit that is able to supply current bidirectionally, and supplies current to the magnetic field correction coil of horizontal direction 2. With this constitution, a control loop is formed in which the sum of the magnetic field generated by the horizontal directional magnetic field correction coil 2 and the horizontal directional component of the external magnetic field detected by the horizontal directional magnetic field detector element 4, converges to zero. Although the above explanations have been given for the magnetic field correction of horizontal direction, they also apply to magnetic field correction of vertical direction. Next, the external magnetic field correction device according to FIG. 2 will be explained. First, the deflection coil disposition positions (not shown) and the electric magnetic characteristics are adjusted in manufacturing steps (combining process). assemble with the deflection coil) of a CRT (not shown). At this point, this adjustment, as well as an external magnetic field strength detected by a horizontal direction magnetic field detecting element 4 are stored in a memory 37. In this condition, the CRT deployment device is completed and ready for shipment. When the CRT deployment device is used in a location to which it has been shipped, a current that is proportional to a difference between the detected value for the external magnetic field strength at a location detected by the magnetic field direction detector element horizontal 4 and the magnetic field strength stored in the memory 37 is provided from the magnetic field intensity difference detector 20 to the horizontal direction magnetic field correction coil 2 through the current driver circuit for field correction Magnetic horizontal 10, and by a magnetic field generated by the magnetic field correction coil of horizontal direction 2, an external magnetic field (in an axial direction of the tube) with respect to the CRT (not shown) is necessarily corrected to be equal to the external magnetic field for the place where the CRT has been adjusted (place of manufacture). The above constitution of the conventional external magnetic field correction device of a CRT display device has the following disadvantages. In the example of Figure 1, the operation of the generator generator circuit 7 needs to carry out the adjustment for each individual product, so it takes a long time for adjustment and thus results in higher manufacturing costs. In case the place of placement or orientation of the CRT deployment device has been changed, it is required to demagnetize the entire deployment device, including the CRT, using an internal demagnetization circuit or an external device in order to make the CRT deployment device presents maximum performance. When an internal demagnetization circuit or an external demagnetization device is operated, an abnormally large magnetic field is detected for a peripheral magnetic field of the magnetic field detection element of horizontal direction 4 compared to a normal external magnetic field such as, geomagnetism , so that failures can occur in the case of Figure 1. In other words, the filtering circuit 9 as described in the example of Figure 1 is effective at disturbance levels such as high harmonic noise which is printed on normal operation and that requires to be operated within an operational response time (within a few seconds) that is, without obstacles when the place of placement is changed or the source of energy is entered; however, it can not eliminate an influence of an abnormally large magnetic field that can be generated when an internal demagnetization circuit or an external demagnetization die is operated. Therefore, when the faults of the magnetic field correction device occur while an internal demagnetization circuit or an external demagnetization device is running so that an abnormal current runs through the correction coil, this can cause a disadvantage, each time that the display device is inversely magnetized so that it can dramatically degrade the performance of the external magnetic field correction device.

On the other hand, the problem of faults due to the operations of an internal demagnetization circuit or of an external demagnetization device originating in the conventional technique of FIG. 1 also exists for the example of FIG. 2. In the step of fabrication (process of combining / assembling with the deflection coil) of the CRT (not shown), when adjusting a deflection coil disposition position (not shown) or electrical magnetic characteristics, it is required to establish irregularities in the slope current which originates in operational irregulars of magnetic field detector, difference detector or amplifier so that they are lower than a regular value. This is to ensure assembly / adjustment conditions (peripheral magnetic field) to design a CRT or diverter yoke. In other words, although it appears that the conventional technique according to Figure 2 solves, by providing a memory and a difference detector, each of the irregularities in the outputs of the magnetic field detector that present a problem after that the product has been shipped, does not yet solve the problem of the initial deviation that presents a problem at the time of assembling the product. Therefore, it is also necessary to adjust the slope current.

BRIEF DESCRIPTION OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide an external magnetic field device that is capable of automatically limiting irregularities in the slope current of an operational current for a field correction coil. external magnetic that can cause a problem in a manufacturing process of a CRT deployer to no more than a predetermined value. The external magnetic field correction device according to the present invention is further characterized in that it comprises an external magnetic field detector for detecting an external magnetic field around a CRT, an external magnetic field correction coil disposed around the CRT to correct the external magnetic field, a current driver circuit for external magnetic field correction to supply the external magnetic correction coil with correction current to correct the external magnetic field based on a detected value of the external magnetic field detector, and a Slope value adjustment unit for adjusting a slope value for the current driving circuit for external magnetic field such that an output of the current driving circuit for the magnetic field at the moment when the external magnetic field around of the CRT is zero is not more than one pre-value determined, and to store an adjusted value. With this constitution, the unevenness value for the current driving circuit for the external magnetic field can be adjusted to no more than a predetermined value and the unevenness adjustment of the current driving circuit for the external magnetic field can be carried out always in easy way, regardless of the place of placement, with which the adjustment problem can be solved and a high accuracy of correction can be achieved. It is another object of the present invention to provide an external magnetic field correction device that is capable of limiting the problem of faults that arise during the operation of an internal demagnetization circuit or of an external demagnetization device. The external magnetic field correction device according to the present invention is further characterized in that it comprises an abnormal input elimination unit for determining that an abnormality has occurred when the output of the external magnetic field detector is not less than a predetermined value and consequently interrupting the operation of the unevenness adjustment unit. Thus, since it is determined that an abnormality has occurred when the output of the external magnetic field detector is not less than a predetermined value and the operation of the unevenness adjustment unit is interrupted accordingly, a failure does not occur even if a an abnormal entry is made due to a demagnetization operation or similar, so the device is highly reliable. The external magnetic field correction device according to the present invention is further characterized in that the unevenness adjusting unit includes a communication means for receiving from an external adjustment means, instructions for adjusting the unevenness value for the driving circuit of current for the correction of the external magnetic field. Therefore, the unevenness value for the current driver circuit for correction of the external magnetic field is adjusted with an external adjustment means using a communication means included in the unevenness adjustment unit, with which it can be adjusted. carry out the adjustment by means of an external automatic adjustment means without there being the need for the user to carry out manual adjustments. The external magnetic field correction device according to the present invention further comprises an external field correction coil current sensing circuit for detecting a value for a current flowing through the external magnetic field correction coil, and the external magnetic field correction coil current sensing circuit is a resistor connected in series to the external magnetic field correction coil. Therefore, the correction current that runs through the external magnetic field correction coil can be detected accurately by means of a simple structure, regardless of the irregularities in the resistance values of the field correction coil external magnetic It is also another object of the present invention to provide a CRT deployment device comprising said external magnetic field correction device. The CRT deployment device according to the present invention is further characterized in that it comprises a CRT deployer and the external magnetic field correction device described above. With this structure, it is possible to produce a CRT deployment device that is capable of adjusting a slope of the current driver circuit described above for the correction of external magnetic field to no more than a predetermined value, capable of always carrying out easy adjustment of the slope of the current driver circuit for the correction of the external magnetic field, regardless of the place of placement, capable of eliminating the adjustment problem, and exhibiting functions of high-precision external magnetic field correction, and is achieved produce a CRT deployer that exhibits highly reliable external magnetic field correction functions and no failures occur, even at an abnormal input, due to demagnetization operations. The CRT display device according to the present invention is further characterized in that it comprises an OSD circuit for creating an adjustment menu and providing instructions for carrying out correction of the external magnetic field to the external magnetic field correction device which will be displayed in the CRT deployer. Therefore, since the correction of the magnetic field is carried out following a previously established adjustment menu, it is possible to carry out the adjustment of the external magnetic field correction using a matrix switch for the screen adjustment that is provided. on a front face of the CRT deployment device and using OSD functions (on-screen display functions) instead of instruction switches connected to a microcomputer input terminal, whereby instruction switches or deployment devices (LED, light emitting diode) can be omitted. The above and other objects of the invention will become apparent more fully from the following detailed description with accompanying drawings.

BRIEF DESCRIPTION OF THE DIFFERENT VIEWS OF THE DRAWINGS Fig. 1 is a block diagram showing a conventional external magnetic field correction device of a CRT deployment device; Figure 2 is a block diagram showing other conventional external magnetic field correction device of a CRT deployment device; Figure 3 is a block diagram showing a structure of an external magnetic field correction device according to the mode 1; Fig. 4 is a flow diagram showing operations of an external magnetic field correction device of a CRT deployment device according to an embodiment of the present invention; Fig. 5 is a flow chart showing creation operations for horizontal magnetic field correction data outside the operations of an external magnetic field correction device of a CRT deployment device according to an embodiment of the present invention.; Fig. 6 is a flow chart showing slope current adjustment operations for a horizontal external magnetic field correction coil outside the operations of an external magnetic field correction device of a CRT deployment device in accordance with one embodiment of the present invention; Figure 7 is a block diagram showing a structure of an external magnetic field correction device according to mode 2; Figure 8 is a block diagram showing a structure of an external magnetic field correction device in accordance with mode 3; and Figure 9 is a block diagram showing a structure of an external magnetic field correction device in accordance with mode 4.

DETAILED DESCRIPTION OF THE INVENTION Modality 1 Modes of the present invention will now be explained with reference to the drawings. It should be noted that portions WHICH are identical or equivalent to those of the conventional art are indicated with the reference numerals of FIG. 1. FIG. 3 is a block diagram showing a structure of an external magnetic field correction device. according to the embodiment 1. In figure 3, 2 denotes a magnetic field correction coil of horizontal direction to cancel an external magnetic field in a horizontal direction (the direction along the axis of the tube) which is connected to an output terminal of a current driver circuit for the horizontal magnetic field correction 10 through a connector 33 fixed to the magnetic field correction coil of horizontal direction 2 and through a connector 32 on a control circuit 100. An input line of the current driver circuit for the horizontal magnetic field correction 10 is connected to a terminated The D / A PlO conversion output of a microcomputer 21 through a voltage amplification circuit 26. A touch switch (or also called instruction switch) 25 is respectively connected to an input terminal P12 of the microcomputer 21. , a non-volatile memory (EEPROM) 19 to input / output terminals P13, P14, P15 and a display device (LED) 29 to an output terminal P16. An output terminal of a voltage amplifier circuit 6 is connected to an input terminal AD1 of A / D conversion of the microcomputer 21, and an output line of a magnetic field detector element of horizontal direction (or also called a sensor). horizontal magnetic field) 4 is connected to a voltage amplifier circuit input terminal 6. An output of a horizontal magnetic field correction current detection circuit 22 is connected to an AD3 input terminal of A / D conversion of the microcomputer 21, and two differential input terminals of a horizontal magnetic field correction current sensing circuit 22 are connected to both ends of the horizontal direction magnetic field correction coil 2 through the connector 32, to which the voltage generated by the direct current resistance of the magnetic field correction coil of horizontal direction 2 is applied. In addition, a voltage corresponding to the current flowing through the coil is applied to terminal AD3. of horizontal magnetic field correction 2. The number 3 denotes a magnetic field correction coil of vertical direction to cancel an external magnetic field in a vertical direction (the direction orthogonal to the axis of the tube), which is connected to a terminal of output of a current driving circuit for the correction of the vertical magnetic field 17 through a connector 35 fixed to the vertical direction magnetic field correction coil 3 and through a connector 34 on the control circuit 100. An input line of the current driver circuit for vertical magnetic field correction 17 is connected to a D / A Pll conversion output terminal of a microcomputer 21 via a voltage amplifier circuit 27. An output terminal of a voltage amplifier circuit 13 is connected to an A / D conversion input terminal AD2 of microcomputer 21, and a vertical direction magnetic field sensing element (also called vertical magnetic field sensor) 11 is connected to a terminal input of the voltage amplifier circuit 13.

An output line of a vertical magnetic field correction current detection circuit 23 is connected to an A / D conversion input terminal AD4 of the microcomputer 21, and two differential input terminals of the correction current detection circuit. of vertical magnetic field 23 are connected to both ends of the magnetic field correction coil of vertical direction 3 through the connector 34, to which the voltage generated by the direct current resistance of the magnetic field correction coil is applied. vertical direction 3. ** In addition, the terminal AD4 is applied with voltage corresponding to the current flowing through the magnetic field correction coil of vertical direction 3. The horizontal directional magnetic field detector element 4 produces a voltage that is proportional to the intensity of the geomagnetis or to the AD1 input terminal of the A / D conversion of the micr computer 21 through the voltage amplifier circuit 6. The microcomputer 21 performs the A / D conversion and the digitization of the voltage applied to the AD1 input terminal of A / D conversion, adds or subtracts field sensor slope correction data magnetic horizontally stored in the non-volatile memory 19, and obtains detection data of the horizontal magnetic field. Then, the microcomputer 21 manages to cancel, following a preliminary adjustment process, coil pulse data provided to the horizontal magnetic field detection data, adds or subtracts slope data from the horizontal correction coil drive circuit previously stored in the non-volatile memory 19, and it obtains magnetic field correction coil pulse data from horizontal direction. Then, the computing partner 21 produces these data by converting them by D / A through the output terminal PlO of D / A conversion, which are provided to the current driving circuit for the correction of the horizontal magnetic field 10 through the voltage amplifying circuit 26. The current driving circuit for the horizontal magnetic field correction 10 provides current that is proportional to the input voltage for the horizontal magnetic field correction coil 2 and, consequently, generates a magnetic field that corrects the influences of geomagnetism in horizontal direction (the direction along the axial tube). As explained so far, the external magnetic field correction device according to this embodiment comprises an external magnetic field detector that includes the magnetic field detector element of horizontal direction 4 and / or the magnetic field detector element of direction vertical 11, an external magnetic field correction coil that includes the magnetic field correction coil of horizontal direction 2 and / or the vertical direction magnetic field correction coil 3, a current sensing circuit of the correction coil of external magnetic field including the horizontal magnetic field correction current detector circuit 22 and / or the vertical magnetic field correction current detector circuit 23, and a current driver circuit for correction of the external magnetic field including the driving circuit of current for the correction of the horizontal magnetic field 10 and / or the current driver circuit for the correction of the vertical magnetic field 17. The device will now be explained for specific operations based on the operation diagram of the microcomputer, as shown in Figures 4, 5 and 6. In Figure 4, the initial setting of the input / output terminals of the built-in memory, recorder, D / A switch and the like of the microcomputer (step ST1) is carried out first. Then, the detection of a horizontal magnetic field by the input terminal AD1 is carried out, and based on the detected value, the correction is carried out, and a pulse process of the horizontal cancellation coil is carried out to determine the pulse data of the horizontal correction coil corresponding to the detected value for the field horizontal magnetic (step ST2). Then, detection of a vertical magnetic field is carried out by the input terminal AD2, and based on the detection value, the correction is carried out, and a vertical cancellation coil pulse process is carried out. to determine impulse data of the vertical correction coil corresponding to the detected value for the vertical magnetic field (step ST3). Then, the pulse data of the horizontal correction coil thus obtained, and the pulse data of the vertical correction coil are converted and generated respectively by D / A from the outputs PlO and Pll of the D / A converter (step ST4). Then, a signal level of the terminal P12 is read, and a key input condition of the touch switch 25 is verified (step ST5), and in case there is no key entry, the operation is returned to the previous step ST2, and the operations from ST2 to ST5 are repeated (step ST6). If there is a key input, the zero point adjustment of the vertical current running through the horizontal magnetic field correction coil is carried out. 2 and the vertical magnetic field correction coil 3 (step ST7). At this point, the external magnetic field around the CRT deployment device is set to zero as a condition for carrying out the key entry. Next, the contents of the operations of step ST2 above will be explained in detail based on Figure 5.

First, the detection of the intensity of the horizontal magnetic field is initiated by the input through the input AD1 of the A / D converter (step ST8), and the performance of the detection operation is expected (step ST9). Then, it is verified if the detected data are within a predetermined scale, and if they are outside the scale, it is determined that an abnormality has occurred, so the process is interrupted and omitted. In other words, the operation of eliminating the abnormal input is carried out (step ST10). If the detected data are within the scale, the input data is added to the vertical magnetic field sensor's slope data of correction value to be corrected for the degree of slope of the sensor, and field detection data is obtained horizontal magnetic (step ST11). In addition, the horizontal magnetic field detection data are converted in accordance with preliminary adjustment means (such as referring to a table or proportional calculation), and the value obtained is added to the horizontal offset coil pulse slope data for to be corrected by the unevenness of the driving circuit, and pulse data of the horizontal correction coil are obtained (step ST12). The same applies to the operations of step ST3 in Figure 4.

The operations of step ST7 in Figure 4 will be explained based on Figure 6. First, the scintillation of the display device (LED) 29 is started to indicate that the adjustment operation is being executed (step ST13). Then, detection of the intensity of the horizontal magnetic field is initiated by an input of the AD1 input of the A / D converter, repeated for a predetermined time to perform the sampling and calculation of an averaged value (step ST14), and wait for the detection operation to finish (step ST15). Then, it is checked if the detected data are within a predetermined scale, and if they are outside the scale, it is determined that a normality has occurred, so that the process is interrupted and omitted (step ST16). Then, a difference between the input detected by the sensor and a designated central value (fixed value) is calculated, and the obtained value is stored in the non-volatile memory (EEPROM) as slope data of the horizontal magnetic field sensor correction data (step ST17). Then, the initial adjustment of the adjustment data to an appropriate value is carried out (step ST18). Then, the adjustment data are converted to D / A, and the output through the output PlO of the D / A converter (step ST19). To correspond to a delay in the operation response of the circuit, a predetermined time is expected to elapse (step ST20). A voltage corresponding to the current flowing through the magnetic field coil of horizontal direction 2 is applied to the terminal AD3 of the A / D converter, and the operating current of the steering magnetic field correction coil is detected. horizontal 2 (step ST21). It is judged whether the value so detected is not greater than a predetermined value A, and if the value is greater than A, the operation proceeds to step ST23, subtracts 1 from the adjustment data, and returns to step ST19. If the value is not greater than A, the operation proceeds to step ST24 to judge whether the value is not less than a predetermined value B, and if the value is less than B, the operation proceeds to step ST25, adds the data of adjustment to 1, and return to step ST19. If it is judged in step ST24 that the value is not less than B, it is determined that the current flowing through the magnetic field correction coil of horizontal direction 2 has converged into a regular value, and data of slope of the driving circuit of the horizontal correction coil between the adjustment data and the designated central value (fixed value) to be stored in the non-volatile memory (EEPROM) 19 (step ST26). Finally, the scintillation of the display device (LED) 29 ends, and the process ends (step ST27).

By means of the above operations, 19 unevenness data of the horizontal magnetic field sensor of correction data and slope data of the driving circuit of the correction correction horizontal correction coil are obtained and stored in the non-volatile memory (EEPROM). are required to adjust the current flowing through the magnetic field correction coil of horizontal direction 2 to no more than a predetermined value. It should be noted that although it has only been explained for operations related to the correction of the horizontal magnetic field, the same operations are carried out for the correction of the vertical magnetic field. As explained so far, in the external magnetic field correction device according to this embodiment, the correction means for the unevenness output current, and the adjustment means of the correction value for the unevenness output current provided on the microcomputer, automatically adjust and correct irregularities in the vertical flow that originate in the irregularities of operation of a magnetic sensor or driving circuit. In other words, by measuring a current flowing through the magnetic field correction coil when the external magnetic field is zero, the adjustment means of the correction value for the slope output current provided in the microcomputer obtain a value of correction for the slope output current from pulse data of the correction coil when the current is limited to no more than a predetermined value, and this correction value is stored in the non-volatile memory. Then, the correction means for the slope difference current, that is, the slope value adjustment unit, corrects magnetic field correction data determined based on the detected value for the external magnetic field by the correction value for the slope difference current, and operates to cause the current flowing through the magnetic field correction coil (slope current) to be no greater than a predetermined value when the external magnetic field is zero. In other words, in this embodiment, it has been possible to adjust a correction value to limit the slope value of the output current for the magnetic field correction coil when the external magnetic field is zero to no more than a predetermined value, and to limit the slope value of the output current for the magnetic field correction coil in an operating condition when the external magnetic field is zero to no more than a value redetermined by the arrangement of a microcomputer, amplifier circuit, sensor magnetic, non-volatile memory, current detector, instruction switch, correction means of slope difference current and adjustment means of the correction value for the unevenness output current inside the microcomputer, and pressing the instruction switch (touch switch) after adjusting the external magnetic field to zero. Accordingly, a high precision magnetic field correction device can be obtained which saves time for making the adjustments.

Modality 2 Figure 7 is a block diagram showing an constitution of an external magnetic field correction device in accordance with mode 2. In this embodiment, the touch switch (instruction switch) 25 of the drawings, related to mode 1, has been replaced using an SIO serial integrated communication interface and a communication connector 36 of the microcomputer 21. The arrangement of communication means in the microcomputer 21 to communicate with the outside, and the provision of a terminal of communication connected to it, allows adjustments to be made through an external automatic adjustment device using the communication means instead of manual adjustment by the user through the operation of the touch switch (instruction switch) 25. In addition, it can also omit the display device (LED) 29 in addition to the touch switch 25.

Mode 3 Figure 8 is a block diagram showing a constitution of an external magnetic field correction device in accordance with mode 3. In this mode, instead of connecting both ends of the steering magnetic field correction coil horizontal 2 and the vertical direction magnetic field correction coil 3 to the horizontal magnetic field correction current detector circuit 22 and the vertical magnetic field correction current detector circuit 23 which are their respective current detector circuits as in constitution of mode 2 as shown, for example, in Figure 7, the connection is carried out so that a signal from both ends of a resistor 51 connected in series to the magnetic field correction coil is made to Horizontal direction 2 is an input signal for the horizontal magnetic field correction current detector circuit 22, and a signal from both ends of a resistor 52 connected in series to the vertical direction magnetic field correction coil 3 is made to be an input signal for the vertical magnetic field correction current detecting circuit 23. the same constitution is used for the constitution of the modality 1 as shown in Figure 3. Using respectively voltages of both ends of the resistors 51, 52 connected in series to magnetic field correction coils of horizontal and vertical direction 2, 3 as input signals for the horizontal and vertical magnetic field correction current detector circuits 22, 23 as described above, the current value of the magnetic field correction coils of horizontal and vertical direction 2, 3 can be detected in the form precise by a simple circuit, despite the irregularities in the resistance values for the coils of magnetic field correction of horizontal and vertical direction 2, 3.

Modality 4 Figure 9 is a block diagram showing an example of a CRT deployment device comprising the external magnetic field correction device in accordance with mode 1 as shown in Figure 3. In Figure 9, a matrix switch 39 is a switch on an adjustment panel provided on a front surface of the CRT display for adjusting, in a normal condition, the luminance or color tone of the screen. An OSD circuit 40 is an on-screen display device for displaying a menu or an adjustment value at the time of adjusting the screen. 41 denotes an image amplification circuit, an input line of which is connected to an image input inferf 42 and the OSD circuit 40, and an output line of which is connected to a cathode electrode of the CRT 1. The microcomputer 21 constantly observes an input condition of the matrix switch, and when it is judged that an input exists, it causes the OSD circuit 40 to be activated. 5 When the OSD 40 circuit is activated, a menu selection image is displayed on a CRT 1 display screen. This menu includes that menu for adjustment of the external magnetic field correction device, and when 0 the operation is carried out carried out following preliminary adjustment processes, adjustment operations are activated for the external magnetic field correction device, by means of which the same effects as those of mode 1 shown in FIG. 3 can be obtained. this invention can be described in various ways without departing from the spirit of the essential features thereof, the present embodiments are therefore illustrative and not limiting, since the scope of the invention is defined by the appended claims more than 0 by the description that precedes them, and all the modalities that are within the goals and limits of the claims, or the equivalence of said met and limits thereof, therefore, have the purpose of being encompassed by the claims.

Claims (12)

NOVELTY OF THE INVENTION CLAIMS

1. - An external magnetic field correction device, comprising: an external magnetic field detector for detecting an external magnetic field around a CRT; an external magnetic field correction coil disposed around the CRT to correct the external magnetic field; a current driver circuit for correction of the external magnetic field for supply to the correction current of the external magnetic field correction coil for correcting the external magnetic field on the basis of a detected value of the external magnetic field detector; and a slope value adjustment unit for adjusting a slope value for the current driving circuit for correction of the external magnetic field, so that an output of the current driving circuit for correction of the external magnetic field is obtained for when the field External magnetic around the CRT is zero, so that it is not greater than a predetermined value, and to store a set value.

2. The external magnetic field correction die according to claim 1, characterized in that it also comprises an abnormal input eliminator unit to determine that an abnormality has occurred when the output of the external magnetic field detector is not less than a value predetermined and, consequently, interrupting the operation of the adjustment unit of the unevenness value.

3. The external magnetic field correction device according to claim 1, characterized in that the unit for adjusting the unevenness value includes communication means for receiving, from an external adjustment device, instructions for adjusting the unevenness value for the current driver circuit for correction of the external magnetic field.

4. The external magnetic field correction device according to claim 1, characterized in that it also comprises a current detector circuit of the external magnetic field correction coil for detecting a current value that runs through the coil of the magnetic field. external magnetic field correction, and the current detector circuit of the external magnetic field correction coil is a resistor connected in series to the external magnetic field correction coil.

5. A CRT deployment device, comprising: a CRT deployment; and an external magnetic field correction device, which includes: an external magnetic field detector for detecting an external magnetic field around a CRT; an external magnetic field correction coil disposed around the CRT display to correct the external magnetic field; a current driver circuit for correction of the external magnetic field for supply to the correction current of the external magnetic field correction coil for correcting the external magnetic field on the battery of a detected value of the external magnetic field detector; and a slope value adjustment unit for adjusting a slope value for the current driving circuit for correction of the external magnetic field, so that an output of the current driving circuit for correction of the external magnetic field is obtained for when the field External magnetic around the CRT is zero, so that it is not greater than a predetermined value, and to store a set value.

6. The CRT deployment device according to claim 5, characterized in that it further comprises an abnormal input eliminator unit for determining that an abnormality has occurred when the output of the external magnetic field detector is not less than a predetermined value and , consequently, interrupting the operation of the unevenness adjustment unit.

7. The CRT deployment device according to claim 5, characterized in that the unit of adjustment of the unevenness value includes means of communication to receive, of an external adjustment device, instructions for adjusting the unevenness value for the current driving circuit for correction of the external magnetic field.

8. The CRT deployment device according to claim 5, characterized in that it also comprises a current detector circuit of the external magnetic field correction coil for detecting a current value that runs through the correction coil of the magnetic field. external magnetic field, and the current detector circuit of the external magnetic field correction coil is a resistor connected in series to the external magnetic field correction coil.

9. The CRT deployment device according to claim 5, characterized in that it further comprises an OSD circuit for making a menu setting to provide instructions for carrying out the correction of the external magnetic field to the external magnetic field correction device. that is going to be deployed on the CRT deployment.

10. The CRT deployment device according to claim 6, characterized in that it also comprises an OSD circuit for making a menu setting to provide instructions for carrying out the correction of the external magnetic field to the external magnetic field correction device. that is going to be deployed on the CRT deployment.

11. The CRT deployment device according to claim 7, characterized in that it further comprises an OSD circuit for making a menu setting to provide instructions for carrying out the correction of the external magnetic field to the external magnetic field correction device. that is going to be deployed on the CRT deployment.

12. The CRT deployment device according to claim 8, characterized in that it further comprises an OSD circuit for making a menu setting to provide instructions for carrying out the correction of the external magnetic field to the external magnetic field correction device. that is going to be deployed on the CRT deployment.