JPS5926052B2 - How to determine the position of a light pen on a CRT display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a CRT display that displays a pattern according to data written in a digital memory.
In a device in which a light pen is opposed to a CRT screen and required data can be written to an address in a digital memory corresponding to this opposed part, the part opposed to the light pen on the CRT screen, in other words, a pattern is displayed. In terms of the light pen pointing position to be displayed, that is, the digital memory, the present invention relates to a method of determining the address of the area where the data of the pattern to be displayed is to be written.

By placing the light pen close to a CRT screen, it optically detects the scanning line that appears on the opposite side using a photoelectric conversion element such as a phototransistor, converts it photoelectrically, and outputs it as a pulsed electrical signal. Based on this electric signal and a signal related to beam scanning of the CRT, the area on the CRT screen that is opposite to the light pen, or directly the area on the CRT screen where the scanning line is detected by the light pen, is detected. Used to recognize location. The number of scanning lines that can be sensitively detected by the light pen depends on the brightness of the screen and the area of the light-receiving surface, but by adjusting the sensitivity, it can be set to about 3 to 10 per field of interlaced scanning. Fourth,
Figure 5 shows the positional relationship between the light pen's scanning line detection range (indicated by a circle) and multiple scanning lines, and the light pen's pulse output waveform diagram (however, the time axis is shown so that it changes each time the scanning line changes). This is a comparison between the Since a light pen is held in the hand and held close to and facing the CRT screen, even if you aim at a certain area and hold the light pen close to the CRT screen, it is inevitable that the pen will be slightly misaligned and become a detection target. The length of the topmost line (first line) of the scanning lines (five lines in this case) within the detection range becomes longer as shown in Figure 4 or shorter as shown in Figure 5. . Generally, the pulse output g4 of the line pen obtained by detecting the first line is used to recognize the area facing the light pen, so that the area facing the light pen is detected in the vertical direction of the screen. A slight positional deviation will be magnified and detected as a large horizontal positional deviation.
The above-mentioned CRT display has a drawback in that it is difficult to display a desired pattern. The present invention has been made in view of such circumstances, and it
It is an object of the present invention to provide a light pen pointing position determination method that stably recognizes the horizontal position of a close opposing portion of a light pen with respect to a screen, and makes it possible to display a desired pattern.

The light pen pointing position determining method according to the present invention is a CRT screen that displays a pattern based on data written in a digital memory in response to the output of a light pen facing a CRT screen.
In an RT display, the light pen detects multiple scanning lines per field and sets the sensitivity to obtain the corresponding pulse output for each line, and then calculates the required data based on the light pen's second and subsequent pulse outputs in one field. It is characterized by determining the address of the digital memory to be written to.

The present invention will be explained in detail below based on drawings showing embodiments thereof.

FIG. 1 is a block diagram schematically showing the main parts of the CRT display according to the present invention, FIG. This is a time chart showing details. In this CRT display, a light pen 13 is placed close to the screen of the CRTl2, and when the light pen 13 is moved, a pattern following the movement trajectory is displayed on the CRT screen.
This system can be called a television blackboard system in which the T-screen is used as a blackboard and the light pen is used as a chalkboard.

In the figure, reference numeral 1 denotes an oscillator circuit that generates a basic tarock pulse with a frequency equal to or higher than that of a counter clock d, which will be described later. Vertical synchronizing pulse a that appears at a rate of once [Figure 2 A],
Excluding the horizontal synchronizing pulse b whose period is shorter than the period of the vertical synchronizing pulse a [Fig. A display period pulse C of an appropriate length that appears once each between adjacent horizontal synchronizing pulses B and b (Fig. 2 c, Fig. 3 opening), and a counter clock d that appears while the display period pulse c appears. [Fig. 2 2, Fig. 3 C], a write pulse e falling in synchronization with the rising edge of the vertical synchronous pulse a, which has a narrower width than the vertical synchronous pulse a [Fig. 2 E], and the vertical synchronous pulse a. A narrow width set pulse f (see FIG. 2) which falls in synchronization with the falling edge is created. The vertical synchronizing pulse a is input to the vertical drive circuit 3 and amplified, and the horizontal synchronizing pulse b is input to the horizontal drive circuit 4 and amplified, and then applied to the CRT12, so that the beam of the CRT12 is synchronized with them. scan.

The CRT12 has m pixels in the horizontal direction and n pixels in the vertical direction, and the counter clock d is set so as to correspond to each pixel in the horizontal direction, that is, while one display period pulse appears. It is arranged so that m counter clocks d appear. Since this system performs interlaced scanning, n/2 display period pulses c appear during one field, that is, between adjacent vertical synchronizing pulses A and a. In other words, 1
n/2 scan lines per field will contribute to the display. Now, the above counter clock d is CRTl2
A digital memory 11 that stores data to be displayed is connected directly to the counting terminal of the counter 8 for giving an address when reading data, and also to a counting terminal for giving an address when writing data to the memory 11. The signal is inputted to the counting terminal of the counter 9 via an AND gate 7. Counters 8 and 9 each have a counter clock d
and the clock d1 that has passed through the gate 7, that is, the output j of the gate 7 [Fig. 2-2, Fig. 3-Fig. It will be done. The reset pulse f is input to the reset terminals of counters 8, 9 and an N-ary counter 14, which will be described later, and the counted value is set to zero by the input. The selector 10 is supplied with a display period pulse c as a selection control signal, and while this pulse c is being input, the count value output of the counter 8 is selected as the selector output, and during other periods, the count value output of the counter 8 is selected as the selector output. The count value output of is selected as the selector output. The write pulse e is given to the memory as a write enable signal, and when the write pulse e is given, since the display period pulse c has not appeared at this time, the counter given via the selector 10 The count value output of 9 is used as a write address, and data (not shown) is written into the memory area of that address. This data is of course binary data, and is configured to include whether it is emitted or dimmed, and in the case of color display, a color code. In this system, one frame consists of two fields with the same content. Therefore, except when the memory contents are rewritten between adjacent fields, each pixel and the adjacent pixel above (or below) it will have the same display. The reason for this configuration is to save the capacity of the memory 11 by taking advantage of the fact that the display does not require as much resolution as a general moving image display. That is, the number of addresses in the memory 11 is MXn/2.
As mentioned above, the read address and the write address are set to zero by the set pulse f in synchronization with the vertical synchronizing pulse a, and then the counter clock d appears m times for each display period pulse related to the horizontal synchronizing pulse b. is the count value of counters 8 and 9, so memory 1
The address system of No. 1 does not consist of horizontal addresses and vertical addresses, but has a structure in which pixel numbers and memory addresses correspond in order according to the scanning locus of the CRT beam from the left to the lower right of the CRT screen of one field. . Therefore, while the display period pulse c appears, data is read out from the memory 11 in the order of the pixel numbers according to the count value of the counter 8 that is updated successively, and this data is combined with the display period pulse c. The signal is input to a D/A (digital/analog) conversion circuit 6 via an AND gate 5 which has two inputs, where it is converted to an analog video signal and applied to the CRT 12, so that each pixel can display a corresponding image. It is set as. On the other hand, the scanning line detection output of the light pen 13 is input to the amplifier circuit 17 and amplified, and then waveform-shaped by the binarization circuit 18 as a binary output g [Fig. 2, Fig. 3, 2]. Become.

This output g is directly input to the AND gate 15 and is also input to the counting terminal of the N-ary counter 14. Then, the carrier output of the N-ary counter 14 is converted to the above AN.
I am using D Gate 15 as someone else's power. Reference numeral 16 denotes an R-S flip-flop, to which the output h of the AND gate 15 (FIG. 2 H, FIG. 3 H) is input to the set terminal S, and the vertical synchronizing pulse a is input to the set terminal R. It is designed so that it will be done.

And the Q output of the flip-flop 16 [Fig.
] is designed to function as an AND gate. Therefore, the counter clock d, which is another input of this AND gate 7, can pass through the AND gate 7 while the Q output 1 is at a high level, in other words, while the flipflop 16 is being set, as shown in FIG. An output j as shown in FIG. 3 is obtained from the AND gate 7. Note that the value of N in the N-ary counter 14 must be larger than 2 and smaller than the number of scanning lines that can be detected by the light pen 13. In other words, when using the above number of lines, it is the same as determining the light pen pointing position based on the first line of the detection scanning lines, and this is the same as determining the position indicated by the light pen based on the first line of the detection scanning lines. This is clear from the comparison of the corresponding pulse output G5. Generally, the value of this N is 13 for the light pen.
It is appropriate to select approximately κ of the number of detection scanning lines. This is because the amount of horizontal displacement of the intersection point between the outer edge (that is, the circumference) of the protruding circular light pen detection range and the scanning line accompanying the vertical displacement of the detection range is smaller as the scanning line is closer to the center. Therefore, when determining the sensitivity of the light pen 13 so that the number of detection scanning lines is 5 as shown in FIGS. 4 and 5, it is preferable to set N=3. Now, the method of the present invention is implemented by a circuit configured as described above,
The circuit for writing data to the memory 11 when the sensitivity is set so that the number of detection scanning lines of the light pen 13 is set to 5 as described above, and when the N-ary counter 14 is a ternary counter. The operation will be explained.

Since the pulse output cannot be obtained when the light pen 13 is not closely opposed to the CRT screen, the flip-flop 16 is in the set state, and the counter 9 is in the readout state during this time, and furthermore, the counter 8 is used for image display. The same counting operation is performed. However, in a certain field, the light pen 13 is placed at a desired location on the CRT screen.
When the light pens face each other in close proximity, five scanning lines will be detected at the opposing parts of the light pen, and five pulse outputs separated by approximately 1H will be input to the amplifier circuit 17, and the corresponding binary output g will be 2. It will be obtained from the value conversion circuit 18. Note that if the timing at which the light pen is opposed to the CRT screen is delayed from the timing of the scanning line at the opposing portion in that field, the pulse output of the light pen will be obtained in the next field. The five pulses of the binary output g are input to the N-ary counter 14, so the binary output g corresponds to the third pulse output of the light pen.
When the third pulse of
A high-level carry signal is obtained from , and this carry signal is input to the AND gate 15, so the third pulse of the binary output g, which is also input to the AND gate 15, passes through this gate 15 for the first time. This output h sets the flip-flop 16, sets the Q output 1 to low level, prohibits the counter clock d<7) from passing through the AND gate 7, and stops the counter 9 from counting up.

The count value of the counter 9 at this point is reset by the vertical synchronizing pulse a that precedes the field in which the light pen detects the scanning line, and then the display timing of each pixel is changed from the display timing of the upper leftmost pixel. This count value is the number of pulses of the counter clock d that are emitted one after another and has passed through the AND gate 7 up to that point in time, in other words, it is the number of elementary pulses of the output j of the AND gate 7 up to that point in time. is, for example, the address of the memory 11 assigned to the pixel located at the intersection of the third line of the five detection scanning lines shown in FIG. 4 and the outer edge of the light pen detection range, or near the horizontal left side thereof. It's summery. The count value is held as it is until the next reset pulse f is input, and since the write pulse e is given to the memory 11 prior to the set pulse f, the timing when the write pulse e is input to the memory 11 is The data that is separately input to the memory 11 is written into the corresponding area using the count value of the counter 9 given via the selector 10 as the write address. Therefore, in the next field, the above-mentioned pixel corresponding to this address will be displayed in accordance with the newly written data. Then, the counter 9 and the N-ary counter 14 are set to zero by the set signal f obtained in synchronization with the fall of the vertical synchronizing pulse a related to the write pulse e, and the flipflop is set to zero by the vertical synchronizing pulse a. 16 is set, and the vertical pulse a
This will prepare for counting in the field that follows.

Since the light pen 13 is used by moving it close to and facing the CRT screen so as to draw a desired pattern, the third line of the five scanning lines detected in the subsequent field is also detected as it moves. Based on the pulse output obtained from the line, the opposing part of the light pen 13, in other words, the indicated position where the display content should be changed is determined, and thereby the memory content of the address corresponding to the pixel at the indicated position in the memory 11 is determined. will be rewritten, and the display will be executed according to the change. As detailed above, in the present invention, the address of the digital memory where the required data is to be written is determined based on the second and subsequent pulse outputs, not depending on the first pulse output of the light pen in one field. This eliminates the inconvenience that the horizontal coordinates of the position indicated by the light pen vary greatly due to a slight variation of the light pen in the vertical direction.

Therefore, even if the light pen wobbles slightly in the vertical direction when moving the light pen horizontally to display a horizontal line on a CRT screen, this wobbling will not be magnified into an uneven horizontal line, but rather a smooth horizontal line. A horizontal line will appear. In addition, in the case of interlaced scanning in which one frame is composed of two fields, even if the light pen indication position remains constant, the position of the detection scanning line will differ slightly vertically for each successive field, and each The intersection point between the first line and the outer edge of the light pen detection range changes greatly in the horizontal direction for each field, but as in the above example,
In a system that displays data at the same address in vertically adjacent pixels so that one frame is composed of field data, the light pen instruction position is recognized based on the light pen pulse output from the first line. However, when determining the write address, the effect of the large change in the horizontal direction mentioned above is magnified. For example, if you place a ruler on the CRT screen to display a vertical line and move the light pen in a straight line, However, in the case of the present invention, such inconvenience can be eliminated. As described above, according to the present invention, it is possible to realize a CRT display capable of displaying a beautiful pattern without unnecessary unevenness using light pen output.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a block diagram schematically showing the main part of a CRT display equipped with a circuit configuration for carrying out the method of the present invention, and FIG. A time chart for explaining the operation; Figures 3 and 3 are enlarged time charts showing a portion of the time chart; Figures 4 and 5 are diagrams of the positional relationship between the scanning line and its detection range by a light pen, and the light It is an explanatory diagram showing a comparison diagram with a pulse output waveform diagram of a pen. 8, 9...Counter, 11...Memory, 12...CRT, l3...Light pen, 14...N-ary counter, 16...
Fritzbufrotzub.

Claims (1)

[Claims] 1 In a CRT display that displays a pattern based on data written in digital memory in response to the output of a light pen facing the CRT screen, the light pen detects multiple scanning lines per field and displays each A light pen pointing position determination method characterized by setting the sensitivity to obtain a corresponding pulse output, and determining the address of a digital memory where required data is to be written based on the second and subsequent pulse outputs of the light pen in one field. .