JPH0122928B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a backlight type coordinate reading device equipped with an automatic light control function.

Conventionally, this type of backlight type coordinate reading device is
Since the operator had to adjust the luminous intensity each time as necessary, it was extremely difficult to operate.

In order to eliminate these drawbacks, the present invention provides a coordinate indicator with a light receiving element and automatically adjusts the luminous intensity of the light source so as to maintain constant brightness on the surface of the coordinate reading plate. be.

Embodiments of the backlight type coordinate reading device according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram of a backlight type coordinate reading device according to the present invention, in which reference numeral 1 is a coordinate indicator, 2 is a backlight unit, and 3 is a main body of the coordinate reading device. The backlight unit 3 is disposed on the lower surface of the main body of the apparatus. Reference numeral 4 denotes a light receiving element, which is connected to an amplifier circuit 5, and the output voltage of the amplifier circuit 5 is input to a voltage comparison circuit 6, which compares it with the voltage from the luminous intensity setting section 8 and outputs a voltage according to the difference. The signal is then input to the switch circuit 7. The switch circuit 7 is
It is turned on/off by a valid signal from the CPU 19, and when turned on, outputs the output voltage from the voltage comparison circuit 6 to the dimming circuit 9. The dimming circuit 9 receives the voltage from the switch circuit 7 and the luminous intensity setting section 8.
It has a function of adding and inputting voltages from the input voltages and adjusting the luminous intensity of the light source 10 according to the input voltages. Reference numeral 11 is a clock generation circuit, and oscillation circuit 12
is connected to generate an alternating magnetic field in the excitation coil 13. Reference numeral 14 denotes a sense line plate, on which a large number of sense lines are laid in the x and y axis directions, each connected to a Y scanning circuit 15,
It is connected to the X scanning circuit 16. Reference numeral 17 denotes an amplified wave circuit that amplifies the voltage of a specific frequency induced in the sense line, digitizes it through an analog/digital converter 18, inputs it to the CPU 19, and performs calculations to generate coordinate values. Applicable CPU
It also has the function of outputting the scanning addresses of the Y and X scanning circuits 15 and 16, and of outputting a valid signal to the switch circuit 7 when the input from the analog/digital converter 18 exceeds a certain level. have

Next, the operation will be explained. First, the operator operates the luminous intensity setting section 8, supplies the voltage signal C to the voltage comparison circuit 6 and the dimming circuit 9, and sets the light source 10 to a desired luminous intensity. Then, the light receiving element 4 in the coordinate indicator 1 generates a current corresponding to the brightness on the sense line plate 14, and the current is input to the amplifier circuit 5. This amplifier circuit 5 amplifies the current from the light receiving element 4,
The voltage signal b is input to the voltage comparison circuit 6 and compared with the voltage signal C from the luminous intensity setting section 8 . At this time, the voltage comparator circuit 6 outputs the voltage signal d, but
If the coordinate indicator 1 is not within the effective reading range on the sense line plate 14, the light receiving element 4 will operate regardless of the brightness on the sense line plate 14. opens and closes to prevent malfunction. That is, when the coordinate indicator 1 is not within the effective reading range on the sense line board 14, the CPU 19 does not output the valid signal a, and the switch circuit 7
It becomes OFF and is not output to the comparator circuit 9. When the coordinate indicator 1 is within the effective reading range on the sense line plate 14, the CPU 19 outputs a valid signal a, turning on the switch circuit 7.
The voltage signal d from the comparator circuit 6 is output to the dimming circuit 9.

Further, when the coordinate indicator 1 is within the effective reading range on the sense line plate 14 and no drawing or the like is placed on the sense line plate 14, the voltage signal b from the amplifier circuit 5 is transmitted to the luminous intensity setting device. Since the gain of the amplifier circuit 5 is adjusted to be at the same level as the voltage signal C from the voltage comparator circuit 8, the output voltage signal d from the voltage comparator circuit 6 is at zero level. Since the zero level is added to the voltage from the luminous intensity setting unit 8 and inputted via the light source 10
The luminosity of does not change.

When a drawing or the like is placed on the sense line board 14, the board surface becomes dark according to the transmittance of the paper, so the current from the light receiving element 4 decreases, and the voltage signal b from the amplifier circuit 5 accordingly decreases. will also be lower.
At this time, a voltage signal d corresponding to the difference between the voltage signal C from the luminous intensity setting section 8 and the voltage signal b from the amplifier circuit 5 is output from the voltage comparison circuit 6, and is supplied to the dimming circuit 9 via the switch circuit 7. be done. Then, the voltage signal C from the luminous intensity setting section 8 and the voltage signal d from the voltage comparator circuit 6 are added and input to the dimming circuit 9, which operates to increase the luminous intensity of the light source 10. Therefore, the brightness can be maintained at the set brightness via the reading medium on the sense line board 14, regardless of the presence or absence of drawings or the quality of the paper.

2A and 2B are a plan view and a side sectional view of an embodiment of the coordinate indicator according to the present invention, in which reference numeral 4 is a light receiving element, 5 is an amplifier circuit, 12 is an oscillation circuit,
13 is an excitation coil, 20 is a key switch, 21 is a key switch encoder, 22 is an excitation coil fixing plate made of a transparent acrylic plate, etc., 23 is a cover,
Reference numeral 24 denotes a cable, which has a configuration in which a light receiving element 4 and an amplifier circuit 5 are added to a conventional coordinate indicator.

As explained in detail above, according to the present invention, a coordinate indicator is provided with a light receiving element, and the light source is driven according to the output from this light receiving element. Since the set brightness is maintained regardless of the paper quality, there is no need to adjust the brightness each time, which has the effect of improving operability.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a backlight type coordinate reading device according to the present invention, and FIGS. 2a and 2b are a plan view and a side sectional view of the coordinate indicator, respectively. 1... Coordinate indicator, 2... Backlight unit, 3... Coordinate reading device body, 4... Light receiving element,
5...Amplification circuit, 6...Voltage comparison circuit, 7...Switch circuit, 8...Light intensity setting section, 9...Dimmer circuit, 10...Light source, 11...Clock generation circuit,
12... Oscillation circuit, 13... Excitation coil, 14...
...Sense line board, 15...Y scanning circuit, 16...
...X scanning circuit, 17... Amplified wave circuit, 18...
Analog/digital converter, 19...CPU, 2
0... Key switch, 21... Key switch encoder, 22... Excitation coil fixing plate, 23... Cover, 24... Cable.

Claims (1)

[Claims] 1. A coordinate indicator comprising a sense line plate, a light source for projecting light onto the sense line plate from below, a light receiving element facing the upper surface of the sense line plate, and an amplifier circuit for amplifying the signal from the light receiving element. a luminous intensity setting unit that outputs a predetermined luminous intensity setting voltage signal; and a voltage comparison unit that compares the voltage signal from the luminous intensity setting unit with the voltage signal from the amplifier circuit and outputs a voltage signal according to the difference. circuit, a switch circuit that opens and closes the voltage signal from the voltage comparison circuit in response to a valid signal from the coordinate reading device main body, and adds the voltage signal via the switch circuit and the voltage signal from the luminous intensity setting section. and an adjustment circuit that adjusts the luminous intensity of the light source according to the input signal, and automatically adjusts the light according to the transmittance of the reading medium on the sense line. .