JPH05134806A - Light pen address detector - Google Patents

Abstract

PURPOSE:To provide a light pen address detector which can exactly detect the address (XY coordinates) of the light pen regardless of the brightness of a CRT. CONSTITUTION:When the light pen 3 presses the screen of a display device 1, a signal is transmitted to a display controller 2 so as to show that the switch of the light pen 3 is turned on. In response to the signal, the display controller 2 transmits an instruction signal to the display device 1 so as to instruct that a mark is outputted for displaying the entire screen in blue for one frame period. The display controller 2 transmits a signal to the display device so that the brightness can be turned to a peak state only for the same time simultaneously with this mark signal. Thus, since the light to be picked up is set at a peak level without fail even when the light pen 3 is normally used at any brightness level, there is no X address difference caused by the brightness and the address of the light pen can be exactly calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color CRT display device using a light pen and a device for detecting the address of the light pen in a display controller.

[0002]

2. Description of the Related Art A light pen is well known as a coordinate input means for directly pointing a target point manually when drawing a figure or the like on a screen of a CRT using a computer or the like.

As described in, for example, "Computer System Equipment" (Electronic Science Series 90, Kogyo Shuppan), a light pen is a photodetector that originally detects a bright spot on a display surface and outputs a signal. Thus, the structure is as shown in FIG. Then, the following operation can be performed under the control of the console control unit.

(A) Identify mode: When the light pen detects a bright spot on the display unit and generates a signal, the display operation of the entire display device is stopped as it is, and the light pen shines on the computer. A signal is sent to notify that a point has been detected.

With this, the computer can know the following contents about the data indicated by the operator with the light pen.

In other words, by reading the SCC of the reshuffle memory, it is possible to determine what number command the display data is,
Alternatively, what kind of figure is a part, by reading the memory contents indicated by SCC, what kind of command is the data, and by reading the XY register, the coordinates of the bright point on the display surface. You can check the position. (B) Tracking mode: The position of the light pen can be input to the computer by tracing the display surface with the light pen. As a result, it is possible to specify an arbitrary position on the display surface and input the trajectory of the light pen.

In this operation, when the light pen detects a bright spot on the display surface and knows the position of the light pen, the bright spot is displayed in the vicinity of the light pen at a constant cycle from the next time and detected by the light pen. And know the new position.

FIG. 4 shows the actual operation principle. The center position of the light pen that I knew at a certain moment was (X
n−1, Yn−1) and the center position of the light pen moves to (Xn, Yn) at the next moment,
(Xn, Yn) can be known by the following method.

That is, the already known position (Xn-1, Y
A cross that is sufficiently large compared to the field of view of the light pen centering on n-1) is displayed as shown in the figure. The positions of the points within the range that the light pen can detect as bright spots are XL to XR and YH, respectively.
~ YL, the newly obtained center point (Xn, Yn
) Is Xn = (XL + XR) / 2, Yn = (YH + YL)
/ 2 is required. (Xn, Yn) is used to detect the next moving point. By detecting the moving points one after another in this way, it is possible to always grasp the position of the light pen, regardless of the position on the display surface.

The tracking operation is actually performed in synchronization with the display repetition frequency.

When determining the XY coordinates of the display surface of a color CRT display device using a light pen, if it depends only on the light existing on the screen at that time, naturally no characters or figures are displayed. The address of the light pen cannot be detected in the background portion. For this reason, pressing the switch of the light pen signals the CRT for one frame to flash the entire screen in blue and display the detection mark.

When the display start position is set to X = 0 and Y = 0, the X and Y counters count until the light pen picks up the mark light.

Further, the coordinates are determined by adding or subtracting the shift due to the response time of the light pen to the count number.

At this time, software corrects the light emission of the light pen mark on the CRT and the delay of the light receiving circuit of the light pen.

Here, the time delay in the process of converting the light emitted from the CRT into an electric signal through the light receiving circuit of the light pen is greatly affected by the brightness of the CRT. As a result, there is a problem that an error occurs in the detection address of the light pen due to the brightness of the CRT.

That is, the light pen has a light receiving range to some extent, and the light receiving range changes depending on whether the brightness level of the CRT is high or low. When the brightness of the CRT is high, the light in the peripheral part of the light receiving field can also be sensed, and when the brightness is low, the light is picked up at the outer side, but when the brightness is low, the light is picked up at the inner side, so it is possible to detect light at the same part. It has the problem of being disabled.

That is, in FIG. 5, when the light pen is vertically applied to the screen, the light-receiving visual field 10 of the light pen at high brightness, the light-receiving visual field 12 of the light pen at low brightness, the true pointing position 14,
The detection position 16 by the light pen at low brightness and the detection position 18 by the light pen at high brightness are shown. Thus, C
Due to the brightness difference on the RT screen, a large change occurs in the detection position even though the designated position is the same.

In FIG. 6, when scanning with the same clock, light passes at a high speed in the X direction, while
Since the Y direction needs to be counted (detected) only once for each raster (scan), even if the position is slightly shifted, a large positional displacement does not occur. However, when the clock frequency is further increased, the deviation of the Y axis also becomes large, and stable coordinates cannot be obtained only by correcting the deviation of light detection due to the response time of the light pen.

[0019]

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide an apparatus capable of accurately detecting the address of a light pen regardless of the brightness on the CRT screen. ..

[0020]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides C
Means for detecting the screen address by detecting the depression of the light pen in the non-display area or the area including the background portion on the RT, and in response to the detection, outputting a mark of a predetermined color to the CRT for one frame period. Means for flashing the entire screen with this predetermined color, and a brightness correction means for displaying the entire screen at a constant brightness of the highest level, regardless of the brightness level used on the screen at the time of flashing by this flash means. It is characterized by including.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a CRT display device to which the present invention is applied. In the figure, the CRT display device 1 is supplied with a video signal from the display control device 2. The brightness of the display device 1 can be set to the highest level of a desired level by an external signal.

When the light Ben 3 pushes the screen of the display device 1, a signal indicating that the switch of the light pen 3 is turned on is transmitted to the display control device 2. In response to this, the display control device 2 transmits an instruction signal to the display device 1 so as to display a mark for displaying the entire screen in blue for one frame period.

A feature of the present invention is that the display control device 2 is provided with means for transmitting a signal for bringing its brightness to the maximum state to the display device 1 for the same time at the same time as the signal of this mark. ..

As a result, no matter which brightness level the display device 1 normally uses, the light pen 3 always picks up the highest level of light, so that there is no difference in X address due to brightness.

Specifically, an accurate address can be obtained by sending a signal having a certain constant as a correction value.

In this way, since the error between the position where the CRT display screen is pressed with the light pen and the address (coordinates) actually obtained by the program is reduced, the light pen use range in the display area becomes dense, The usage of the light pen becomes more effective.

That is, if the error is large, the effective range of the light pen becomes coarse as shown in FIG. 2A, but the error becomes small, so that the effective range becomes as shown in FIG. 2B. Become dense.

[0029]

As described above, according to the present invention,
Regardless of the brightness level of the light pen, the light to be picked up is always at the highest level by the brightness correction means, so that the address (XY coordinate) of the light pen can be accurately obtained regardless of the brightness of the CRT. ..

[Brief description of drawings]

FIG. 1 is a configuration diagram of a CRT display device applied to the present invention.

2A and 2B are explanatory views showing changes in the effective range of the light pen according to the present invention.

FIG. 3 is a cross-sectional view showing the structure of a general light pen.

FIG. 4 is an explanatory diagram showing the principle of address detection accompanying movement of a light pen.

FIG. 5 is a diagram showing a detection position by a light pen that changes according to the level of luminance of a CRT.

FIG. 6 is a diagram showing a scanning operation of a CRT screen.

[Explanation of symbols]

 1 ... CRT display device 2 ... Display control device 3 ... Light pen

Claims (1)

[Claims] 1. A means for detecting the screen address by detecting the depression of a light pen in a non-display area or an area including a background portion on a CRT, and in response to the detection, a predetermined color for a period of one frame on the CRT. The means for outputting the mark to flash the entire screen with this predetermined color, and the brightness for displaying the entire screen at the maximum level of constant brightness, regardless of the brightness level used on the screen at the time of flashing by this flash means. A light pen address detection device comprising: a correction unit.