JPH0447329B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a display position detection device using a light pen for a CRT display device.

[Conventional technology]

A display position detection device using a light pen is described, for example, in "Light Pen Instruction Manual" (published by Hitachi, Ltd., May 1978). Second
The figure shows the configuration of a character position detection device using a light pen of this conventional CRT display device.
In the figure, a refresh memory 20 stores data to be displayed on a display device 50, and is constantly read out by signals from a timing generation circuit 70. The read data is sent to a pattern generator 30, developed into a character or graphic dot pattern, and sent to a video signal generation circuit 40. A video signal is sent from the video signal generation circuit 40 to the display device 50, and characters or graphics are displayed on the CRT. Switch 6 for light pen 60
5 is attached, and when the light pen is pressed against the CRT tube surface, this switch 65 is turned on. Then, the grid control circuit 80 outputs the grid signal 8
5 is sent to the video signal generation circuit 40, and the photodetection grid is displayed on the CRT of the display device 50.
Vertical character position counter 90 receives a signal from timing signal generating circuit 70, counts the vertical character position of the scanning line, and sends the value to vertical character position latch register 110. Vertical character position counter 90
is reset by a reset signal 72 every time the scanning line scans the screen once. Horizontal character position counter 100 receives a signal from timing signal generating circuit 70, counts horizontal character positions on a scanning line, and sends the value to vertical character position latch register 120. Horizontal character position counter 100 is reset by reset signal 74 each time a scan line reaches the right edge of the screen. When light pen 60 detects the light detection grid, it sends a light detection signal 68 to vertical character position latch register 110, horizontal character position latch register 120, and processing unit 140. Vertical character position latch register 110 and horizontal character position latch register 120 latch the values of vertical character position counter 90 and horizontal character position counter 100, respectively, upon receiving photodetection signal 68. Therefore, the vertical character position latch register 110 stores the vertical character position when the light pen detects the light detection grid, and the horizontal character position counter 100 stores the vertical character position when the light pen detects the light detection grid. Horizontal character position is stored. When processor 140 receives photodetection signal 68, it sends an address signal to address bus 150, which causes address decoder 10 to send a decoded signal 12 to vertical character position latch register 110. Vertical character position latch register 110 busses the vertical character position value onto data bus 130 upon receiving decode signal 12. Processor 140 reads the vertical character position value via data bus 130. Next, the processing device 14
0 sends an address signal to address bus 150 and address decoder 10 sends a decode signal 14 to horizontal character position latch register 120. The horizontal character position latch register busses the horizontal character position value onto data bus 130 upon receiving decode signal 14. Processor 140 reads the horizontal character position value via data bus 130. In this way, character positions were detected by reading the vertical and horizontal character positions.

[Problem that the invention seeks to solve]

FIG. 3 shows the positional relationship between the light receiving port and the fluorescent surface of the light pen. In recent years, high-definition CRTs capable of displaying approximately 6,000 characters or more have been put into practical use, but due to the relationship between the luminance of the cathode ray tube and the sensitivity of the light pen's photodiode, the light receiving aperture must be at least 2 mmφ (receiving angle 30 mm). °) is required. On the other hand, since the thickness of the cathode ray tube glass surface is 10 to 18 mm, the light detection area on the fluorescent surface is approximately 10 mmφ, an area equivalent to 3×3 characters.

FIG. 4 shows the relationship between the displayed characters on the fluorescent surface and the light detection area of the light pen. In order to increase the detection accuracy in the vertical direction, it is common for the grid to appear only near the center of the character. However, if the light pen detects light at point P1, the coordinates of light detection will be (x+1, y), and if the light pen detects light at point P2, the coordinates of light detection will be (x, y+1). Become. Furthermore, at point P3 (x, y
+2), and (x+1, y+3) at point P4, and of course these points P1, P2, P3, and P4 do not match.
Moreover, where the light pen detects light among points P1 to P4 is entirely due to chance. However, the coordinates of each point are values expressed with the length and width as one character interval. In this way, the conventional technology does not take into account the spread of the light detection area due to the thickness of the cathode ray tube glass surface, so it is difficult to accurately determine the position of characters, especially for high-definition CRTs that can display more than 6,000 characters on a single screen. There was a problem that it could not be detected.

SUMMARY OF THE INVENTION An object of the present invention is to provide a display position detection device that eliminates the above-mentioned conventional drawbacks and can accurately detect character positions on a character-by-character basis even in the case of a high-definition CRT.

[Means for solving problems]

The above purpose is to provide a means for detecting the maximum value by observing the length of the grid detected by the light pen multiple times, and for counting and detecting the grid by the counter using the maximum grid length detected by the means. This is achieved by providing a correction means for correcting the position coordinates.

[Effect]

The length of the grid is measured by counting the number of clocks while the light pen is detecting light. If we measure the length of this grid multiple times and store the longest grid length in the maximum width register, we can think of this as the length of the grid closest to the center of the light pen light detection area.
Therefore, this can be considered to be a value close to the diameter of the light pen light detection area. Therefore, by adding half of this value, that is, an approximate value of the radius of the light pen light detection area, to the horizontal character position detected by the light pen, the coordinates of the center of the light pen light detection area can be determined.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail. FIG. 5 is a block diagram showing one embodiment of the present invention, in which the correction circuit 160 is
has been added. The operations of the parts other than the correction circuit 160 are the same as those shown in FIG. 2, and a light detection grid is displayed on the CRT of the display device 50 by pressing a light pen against the CRT tube surface. The vertical character position counter 90 and the horizontal character position counter 100 count the vertical and horizontal character positions of the scanning line at that time, and these counters 90 and 100 are counted at the timing when the light detection grid of the light pen 60 is first detected. The count value is latched into the vertical character position latch register 110 and the horizontal character position latch register 120. Furthermore, in this embodiment, the light detection grid detection signal 68 from the light pen 60 is also applied to the correction circuit 160.

FIG. 6 is a block diagram showing a detailed embodiment of the correction circuit 160, in which counters 16020 and 16030
The truth table for latch registers 16040 and 16050 is shown in FIG. However, in these figures, H is high level, L is low level, X is arbitrary, ↑ is the rise from low level to high level,
Q ₀ represents the previous state, and Z represents the high impedance state.

In FIG. 6, the light detection signal 68 is a low level signal while the light pen is detecting the light detection grid. Therefore, when the light pen is not detecting light, the light detection signal 68 is high level, and the low level signal which is inverted by the inverter 16010 is sent to the counters 16020 and 16030.
Since it is input to the CLR terminal, the output value of both counters is 0. When the light pen detects light and the light detection signal 68 becomes low level, the counter 16020
EP, ET, CRT terminal and counter 16030 EP,
The CLR pin becomes high level, and first the counter
16020 starts counting the dot clock signal 72. Light pen finishes light detection and light detection signal 6
Counting continues until 8 becomes a high level. When this counter 16020 counts up midway, its RCO terminal becomes high level, and the counter 16030 starts counting. In this way, both counters count how many dots the length of the photodetection signal 68 corresponds to, as shown by the output signals of the counters (16020, 16030) in FIG. The relationship between the dot clock 72 and characters is illustrated in FIG. 10, where one character has 13 dots in the horizontal direction. and the ninth
The counter output signal in the figure shows the case where the photodetection signal 68 corresponds to 8 dots.

The counts of these counters are latched into the light detection width register 16040 when the light detection signal 68 changes to a high level after light detection of the light pen is completed (see FIGS. 8 and 9).

On the other hand, in FIG.
is input to the character clock clutch register 16050. This character clock signal 74 is
As shown in FIG. 10, the left half of the character is at a low level, and the right half is at a high level, and these light pens 60 detect light first and the light detection signal 68
When changes from high level to low level, this becomes the latch signal 16015 and the latch register 16050
Being beaten up. Therefore, the character clock clutch register 16050 stores a low level if the detection position is on the left side of the character when the light pen first detects light, and a high level if the detection position is on the right side of the character. The timing of these character clock signals 74, character clock latch signals 16015, and latch registers are shown in FIG.

As described above, when the light pen 60 finishes detecting light, the vertical character position latch register 11
0, the horizontal character position latch register 120, the photodetection width register 16040 in the correction circuit 140, and the character clock latch register 16050 have all been latched, but the rising edge of the photodetection signal 68 at this time Processing device 140 by
is activated, and the program processing shown in FIG. 1, which is a feature of the present invention, is started. In this process, first
Vertical character position latch register 11 by 10 and 20
0 and the horizontal character position latch register 120 is read. Next, in process 30, the light detection width register 16040 and the character clock clutch register 16050 are read. This is performed by causing the processing unit 140 to read data via the data bus 130 by setting the decode signal 18 in FIG. 6 to a low level. Next, in process 40, the maximum width register 16064 in FIG. 6 is read.
This maximum width register 16040 is RAM (Random
This is a 1-byte register in the Access Memory) 16060, and although it is omitted in the figure, it is set to 0 as an initial value. This reading is performed by setting the R/W signal 144 to a low level and the decode signal 16 to a low level. Next, in process 50, it is determined whether the value of the photodetection width register 16040 is larger than the value of the maximum width register 16064, and if it is, in process 60, the value of the photodetection width register 16040 is moved to the maximum width register 16064, and the value is equal to or small, process
Run 70. In process 70, an initial value is written to the subtraction counter 16062. This writing is performed by the R/W signal 144.
This is executed by setting the signal to high level and the decode signal 16 to low level. This initial value is used to determine how many times the photodetection interrupt processing is to be performed, and is set to 10 in this embodiment. process
At 80, 1 is subtracted from the subtraction counter, and this result is 0.
It is determined whether the light detection signal is larger than that, and if it is larger, processing 90 is executed to wait for the next photodetection signal, and if it becomes 0, processing 100 is executed. Process 90 is a process in which the light pen detects the next grid and waits for an incoming light detection signal. When the light pen detects the next grid and a light detection signal is received, the process is executed again from the beginning of the process, that is, process 10. In this example, the initial value of the subtraction counter 16062 is set to 10, so the processing
10 to 90 will be executed 10 times and the length of the grid will be measured 10 times and the longest one will be stored in the maximum value register 16064. For example, FIG. 10 shows an example of a display surface detected by a light pen, where there is a grid with lengths G1, G2, and G3. If this is detected repeatedly as many times as the number set in the subtraction counter and the maximum value is determined, the maximum length _G2 is stored in the maximum width register 16064, and the process proceeds to process 100.
In processing 100, the character clock clutch register
Determine whether the value of 16050 is 0. This is to determine whether the light detection position is on the left half or the right half of one character. If the value of the character clock clutch register 16050 is 0, that is, the light detection position is in the left half of one character, process 110 is executed, and if it is 1, that is, the light detection signal is in the right half of one character, process 120 is executed. be done.

This process 110 or 120 is for correcting the horizontal character position. In the case of Fig. 11, the vertical position y+1 of point P2 where the grid length reaches the maximum value G2 passes through the center of the light pen light detection area, so this value y+1
1 may be used as the detection position. However, since the horizontal position value x is the x coordinate of point P2, correction is required to set the center position of the light pen light detection area as the detection position. Therefore, when point P2 is on the left half of one character frame, the value of register 16050 is 0.
In this case, in process 110, [horizontal character position] = [read value of latch register 120] + 1/2 [value of maximum width register (G2)] / [number of horizontal dots in one character] ... (1 ), and when point P2 is also in the right half, register
If the value of 16050 is 1, in this case, the above formula (1) is executed in process 120.
The value obtained by adding 1 to the right side of is calculated as the horizontal character position. However, division by the number of horizontal dots in one character is
This is because the character position is expressed in units of characters as described above.

When the above correction process is completed, 0 is finally written to the maximum value register 16064 in process 130.
This is executed by setting the R/W signal 144 to a high level and the decode signal 16 to a low level in FIG. 6, thereby completing preparations for detecting the character position of the next character.

〔Effect of the invention〕

According to the present invention, by having a light detection position correction circuit that takes into account the spread of the light detection area due to the thickness of the display surface of the display device, accurate display position detection for each character can be achieved even in high-precision display devices. It has the effect of being able to do the following.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of display position detection processing in the device of the present invention, FIG. 2 is a block diagram of a conventional display position detection device, and FIG. 3 is a diagram showing the spread of the light detection area by the cathode ray tube glass surface. Figure 4 is an explanatory diagram of the light pen detection area and light detection coordinates.
FIG. 5 is a block diagram showing one embodiment of the device of the present invention, FIG. 6 is a detailed diagram of the correction circuit, and FIGS.
9 is a diagram showing the truth values of counters and registers, FIG. 9 is an operation time chart of the correction circuit, FIG. 10 is a diagram showing the relationship between characters and clock signals, and FIG. 11 is a diagram showing character positions in the device of the present invention. It is an explanatory diagram of a calculation method. 50... Display device, 60... Light pen, 70... Timing generator, 80... Grid control circuit, 90... Vertical character position counter, 1
00...Horizontal character position counter, 110...Vertical character position latch register, 120...Horizontal character position latch register, 130...Data bus, 14
0...Processing device, 150...Address bus, 16
0...Correction circuit.

Claims (1)

[Claims] 1. Vertical and horizontal character position counters having as their counts the current scan position on the CRT screen by counting the dot clocks from the start of the vertical and horizontal scan, and the characters pressed onto the CRT screen. A counter reading means reads the count values of the vertical and horizontal character position counters at the timing when a scanning line enters the light detection area of the light pen, and a dot clock measures the grid length from when the scanning line enters the light detection area until it exits. Maximum grid length detection means for detecting by counting and repeating the detection a plurality of times to detect the maximum value of the grid length obtained each time, and a value obtained by halving the maximum grid length detected by the means. The value added to the horizontal character position read by the counter reading means is the corrected horizontal character position, and if the position where the scanning line enters the light detection area is within the right half of the character frame on the CRT screen. A correction means is provided for correcting the corrected horizontal character position so that, when determined from the value of the character clock signal, the value obtained by adding the horizontal length of one character to the corrected horizontal character position is set as the corrected horizontal character position. Display position detection device.