JPS62109377A - Optical system position detector - Google Patents

Abstract

PURPOSE:To shorten the scanning time of the titled detector for sequentially scanning by providing a second load capable of being connected in parallel with a first load connected with a photo detector, and controlling to switch the connection of the first and second loads by a control signal to shorten time from the OFF of a light emitting element to ON of next light emitting element. CONSTITUTION:Lights from a plurality of light emitting elements are received by individually corresponding photo detectors B1-Bn, and the light passages between the light emitting elements and the photo detectors are shielded by the outputs of the photo detectors B1-Bn to detect the shielded position. The second loads r1-rn capable of being connected in parallel with the first loads R1-Rn connected with the photo detectors B1-Bn are provided in this position detector to control to switch the connections of the first loads R1-Rn and the second loads r1-rn by a control signal. The loads r1-rn are commonly connected, for example, with the collector side of a switching transistor Q to control the transistor Q by the control signal input to a control terminal 2, and a falling time constant is reduced by decreasing the value of the entire load through parallel connection.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a circuit for performing sequential scanning in a position detection device constituted by a plurality of light emitting elements and light receiving elements.

BACKGROUND OF THE INVENTION A typical prior art is an optical input device that inputs information using a stylus, a finger, or the like.

This optical human power device detects light from a plurality of arranged light emitting elements using light receiving elements that individually correspond to the light emitting elements, and traces the light path from the light emitting elements to the light receiving element using a stylus pen or finger. This allows the coordinate position input by the stylus pen or finger to be detected and information to be input.

A circuit diagram of a light emitting element used in this type of optical input device is shown in FIG.

This circuit diagram shows a control circuit 10 and signals outputted from the control circuit 10 to light emitting elements A, ~A, respectively.

It is composed of transistors S and -S1 that supply to the circuit. The control circuit 10 sequentially applies rHJ level signals to the bases of the transistors S1 to S7, thereby causing the light emitting elements A, -A, . . . to emit light one by one.

FIG. 4 shows a light receiving element circuit diagram.

This light receiving element circuit diagram shows the light emitting elements A1 to A.

Light-receiving elements B, ~B7 provided correspondingly to each other, and a load resistor R connected to the cathode side of these light-receiving elements.
It is read by the reading circuit 11 via I"R- and buffer U I""U-.

In this way, from the light emitting elements A, ~A, to the light receiving element B,
When the optical path leading to ~Bn is blocked by a stylus pen, a finger, etc., it will be detected by the reading circuit 11 and the corresponding information will be input.

(Problem to be Solved by the Invention) However, in the light emitting element circuit and light receiving element circuit having such a configuration, the light emitted from the light emitting element is transmitted not only to the corresponding light receiving element but also to the light emitting element arranged in the vicinity of the light emitting element. Light also enters the other light-receiving elements, and the plurality of light-receiving elements are simultaneously turned on. However, due to the response characteristics of the light-receiving element, even if the light-emitting element is turned off, the element, once turned on, will not be turned off until a certain period of time has elapsed. For example, i
0IJL, then OFF L, immediately i
When the +1st light emitting element is ON and the light of the corresponding 4+1st light receiving element is detected, even if the i+1th light is blocked by the indicator, the i+1th light receiving element is turned ON by the ith light emitting element. It may remain. FIG. 5 shows the signal state when such a situation occurs. On the other hand, in order to prevent this kind of malfunction, for example, i
After turning off the th light emitting element, U. Sufficient time (tl) until the input signal of , can be determined to be at rLJ level.
It is conceivable to turn on the i+1th light-receiving element after elapse of , but if this is done, a problem arises in that the scanning time becomes significantly longer.

(Means for solving the problem) The present invention receives light from a plurality of light emitting elements by individually corresponding light receiving elements, and based on the output of the light receiving elements,
In a position detection device that detects a position where an optical path between a light emitting element and a light receiving element is interrupted by blocking the optical path, a second load connectable in parallel with a first load connected to the light receiving element is provided. A load is provided, and the first load and the second load are connected to each other.
The connection to the load is switched and controlled by a control signal.

(Function) After the i-th light emitting element turns OFF and immediately before the 1+1st light emitting element turns ON, the first load and the second load are connected in parallel using a control signal, and the value of the entire load is reduced to reduce the fall. Decrease time constant and shorten delay time.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a circuit diagram of a light receiving element in an optical position detection device according to the present invention.

Note that the light emitting element circuit diagram used is the same as the conventional one.

In FIG. 1, load resistors R9 to R, . . . are connected from the cathode sides of the light receiving elements B 1 to B, . . . via lines 1.1, . Each of these lines 1.1... is connected via a diode D, ~D7 to a respective second load resistor r, ``-r,'', and these second
The loads r, ``-r,'' are commonly connected to the collector side of the switching transistor Q. This switching transistor Q is controlled by a control signal input to the 171? output terminal 2. This control signal is As shown in Fig. 2, this is a pulse signal that is output immediately before outputting the control signals 81 to S1.When this control signal is at the rHJ level, each of the second loads r1 to r, . The combined resistance seen from the lines 1, 1, . The resistance becomes the load.On the other hand, the control signal is rL
At J level, line 1.1...
The load resistance seen from the above becomes the value of the first loads R1 to R7.

FIG. 2 shows a signal waveform when an indicator is present between the i+1th light emitting element and the light receiving element in the light receiving element circuit having such a configuration.

In FIG. 2, immediately after the i-th light emitting element is turned off, the control 11 signal output from the control terminal 2 is at the "L" level, and the load is only R3°1, so that IJ;
+1 input signal causes the input voltage to drop according to the conventional curve. On the other hand, the control signal input from control terminal 2 is r
When the HJ level is reached (timing L), the load becomes a parallel circuit of R3° and rill, and U. The input signal of 1 falls at a steep slope. As a result, the signal for turning on the i+1th light emitting element can be output after the period L2 shown in the drawing, and this t2 is the delay period L1 shown in FIG.
It can be made extremely short compared to .

(Effects of the Invention) As described above, according to the present invention, the light emitting element can be turned off.
The time until the next light emitting element is turned on can be further shortened, and the scanning time of an optical position detection device that performs sequential scanning can be shortened.

[Brief explanation of drawings]

Fig. 1 is a light receiving element circuit diagram in an optical position detection device according to the present invention, Fig. 2 is a timing chart 1-2 showing the operation of the light receiving element circuit diagram, Fig. 3 is a light emitting element circuit diagram, and Fig. 4 is a light emitting element circuit diagram. Conventional light receiving element circuit diagrams, FIGS. 5 and 6 are timing charts for explaining the operation of the conventional light receiving element circuit diagrams. A, -A,...Light emitting element 81~B,...Light receiving element R3~R,...First load r, ~r,...Second load Fig. 7 Fig. 4

Claims (1)

[Claims] 1) Light from a plurality of light emitting elements is received by individually corresponding light receiving elements, and an optical path between the light emitting elements and the light receiving elements is blocked based on the output of the light receiving elements. By,
In a position detection device configured to detect the blocked position, a second load is provided that can be connected in parallel with the first load connected to the light receiving element, and the connection between the first load and the second load is controlled. An optical position detection device characterized in that switching is controlled by a signal.