JP3140306B2 - Signal processing circuit for optical encoder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing circuit for an optical encoder used for a mouse or a trackball, and more particularly to a signal processing circuit for shaping an analog detection signal obtained from a light receiving element into a rectangular waveform. About.

[0002]

2. Description of the Related Art An optical rotary encoder used in an XY coordinate input device such as a mouse or a trackball usually detects the rotation of a ball contained in a casing to obtain the XY coordinate. The operation moving direction and the operation moving amount of the input device are obtained.

In this case, an XY coordinate input device (for example, a mouse) having an optical rotary encoder includes a ball rotatably contained in a mouse and a plurality of balls arranged at a predetermined pitch in a circumferential direction. A pair of disc-shaped light-shielding plates (rotary encoder plates) having slits, a pair of rotating shafts provided at the center of the light-shielding plate, and contacting the ball and rotating with the rotation of the ball; , Two light emitting elements and two light receiving elements, each of which is opposed to each other via the slit arrangement part, and a casing for accommodating them. Here, one set of the light emitting element and the light receiving element performs detection in the X-axis direction (detection of the X-axis direction component of the movement of the mouse), and the other set of the light emitting element and the light receiving element performs the detection in the Y axis direction. The detection (detection of the Y-axis direction component of the movement of the mouse) is performed. Each of the set of one and the other light-emitting elements and light-receiving elements is composed of two light-emitting elements and light-receiving elements, and one light-receiving element of one set sends out an A-phase signal and a B-phase signal, respectively. . These A-phase and B-phase signals are ideally 90
It is a substantially sinusoidal analog waveform signal with different degrees of phase,
Each signal is converted into a rectangular wave digital signal (binary phase pulse signal) by a signal processing circuit, and then supplied to a microprocessor or the like inside or outside the mouse,
The moving direction and the moving amount of the mouse are obtained, and the result, that is, necessary control according to the mouse movement is performed by a control device such as a host computer connected to the mouse.

FIG. 8 is a plan view showing a schematic configuration of the inside of a mouse which is an XY coordinate input device having the above-mentioned optical rotary encoder, and FIG. 9 shows a disk-shaped light shielding plate provided in the mouse of FIG. FIG. 10 is a block diagram showing an example of a conventional optical rotary encoder signal processing circuit provided in the mouse of FIG. 8, and FIG. 11 is a signal waveform obtained from the processing circuit shown in FIG. FIG. 4 is a signal waveform diagram showing an example of the above.

In FIG. 8, reference numerals 1 and 2 denote disc-shaped light shielding plates (rotary encoder plates), and reference numerals 3 and 4 denote rotating shafts, 5A, 5B,
6A and 6B are light emitting elements such as light emitting diodes (LED),
7A, 7B, 8A, and 8B are light receiving elements such as phototransistors; 9 is a ball that can be rotated by moving a mouse;
Is an urging roller, 11 is a spring, and among the reference numerals 1 to 8, odd numbers represent components in the X-axis direction, and even numbers represent components in the Y-axis direction. It shows the components on the B-phase side.

The light shielding plates 1 and 2 are made of non-transparent synthetic resin. As shown in FIG. 9, a large number of slits 12 are formed and arranged at a predetermined pitch in the circumferential direction. The rotary shafts 3 and 4 are integrally formed so that the axial direction is perpendicular to the plate surfaces of the light shielding plates 1 and 2. A first set of two light-emitting elements 5A, 5B and light-receiving elements 7A, 7B are respectively arranged opposite to each other on the slit arrangement portion of the light shielding plate 1 so as to sandwich the slit arrangement portion. The light-emitting elements 6A, 6B and the light-receiving elements 8A, 8B of the second set are also opposed to each other at the slit arrangement portion of the second set. The light shielding plate 1, the rotating shaft 3, and the two light emitting elements 5A and 5B and the light receiving elements 7A and 7B, which are components in the X-axis direction, are housed inside an encoder case (not shown), respectively. 1 and the rotating shaft 3 are rotatably supported inside the encoder case. Similarly, the light shielding plate 2, the rotating shaft 4, and the two light emitting elements 6A and 6B and the light receiving elements 8A and 8B, which are components in the Y-axis direction, are also housed in an encoder case (not shown), respectively. The light shielding plate 2 and the rotating shaft 4 are also rotatably supported inside the encoder case. A part of both rotating shafts 3 and 4 are both exposed from the encoder case, and their peripheral surfaces are in frictional contact with a rotatable ball 9. An urging roller 10 is pressed against the ball 9 by the resilience of a spring 11 to constantly urge the ball 9 in the directions of the two rotating shafts 3 and 4 so that the ball 9 and the two rotating shafts 3 and 4 are in good condition. It is configured to make frictional contact. The rotating shafts 3 and 4 are arranged so that their axes are oriented in the Y-axis direction and the X-axis direction, that is, orthogonal to each other. The ball 9 is attached to the spring 11 with respect to these axes. Force roller 1
0, an intermediate direction between the X-axis direction and the Y-axis direction,
In other words, bias is applied to both rotating shafts 3 and 4 from a direction of approximately 45 degrees.

The operation of the XY coordinate input device (mouse) having the optical rotary encoder configured as described above is as follows.

When the operator grips the mouse body (casing) and moves it on a base plate (not shown), the ball 9 rotates due to friction between the base plate and the ball 9.
As the ball 9 rotates, the two rotating shafts 3 and 4 that are in frictional contact with the ball 9 rotate, and the two light shielding plates 1 and 2 that are integrally formed with the two rotating shafts 3 and 4 simultaneously. Rotate. As described above, a large number of slits 12 are formed in the both light shielding plates 1 and 2 in the circumferential direction at a predetermined pitch, and when the two light shielding plates 1 and 2 rotate, the first pair of pairs is formed. The light from the light emitting elements 5A and 5B to the light receiving elements 7A and 7B and the light from the light emitting elements 6A and 6B forming the second pair to the light receiving elements 8A and 8B alternately pass through the multiple slits 12, respectively. The first set of both light receiving elements 7A and 7B and the second set of both light receiving elements 8A and 8B transmit an A-phase signal and an A-phase signal corresponding to the cut-off or transmission of the light, respectively. A B-phase signal is sent. When the mouse is moved at a constant speed, the A-phase signal and the B-phase signal are substantially sinusoidal analog waveform signals, and the phase difference between the A-phase signal and the B-phase signal is 90%. Degrees, that is, each optical element with respect to the slit 12, in particular, the first set of both light receiving elements 7A and 7B and the second set of both light receiving elements 8A and 8B so as to have a quarter period.
Are positioned and held inside the encoder case.

Next, the A-phase signal and the B-phase signal are converted into two rectangular wave digital signals (binary phase pulse signals) by a signal processing circuit described below. The microprocessor or the like performs calculations and the like to detect the moving direction and the moving amount of the X-axis component and the Y-axis component of the mouse main body corresponding to the rotation of the ball 9. That is, the microprocessor or the like determines the rotation direction of the ball 9 (whether the movement of the mouse body is rightward or leftward) based on the delay and advance of the phase of the A-phase signal and the B-phase signal in the X-axis direction, and the pulse of the digital signal. The movement amount of the mouse body in the discrimination direction is obtained from the number, and similarly, the rotation direction of the ball 9 (movement of the mouse body is forward or backward) In addition to determining the direction, the amount of movement in the determination direction is obtained from the number of pulses of the digital signal.

FIG. 10 is a block diagram showing an example of a signal processing circuit of a conventional optical rotary encoder. The waveform shaping circuit described in Japanese Utility Model Laid-Open Publication No. 1-167622 is applied to the mouse shown in FIG. It is a block diagram in case. Here, since the processing circuits in the X-axis direction and the Y-axis direction are the same, only a circuit portion for processing the A-phase signal and the B-phase signal in the X-axis direction is shown in a block diagram.

In FIG. 10, 13A and 13B are amplification circuits, 14A and 14B are positive side peak value detection circuits, and 15A and 1
5B is a negative side peak value detection circuit, 16A, 16B, 17A,
17B is a resistor having the same resistance value, 18A and 18B are rotation / stop discriminating circuits, 19A and 19B are threshold level switching circuits, 20A and 20B are rectangular wave processing circuits, and other components the same as those shown in FIG. Have the same reference numerals. Also, the alphabet A at the end of the code,
B represents a component on the A-phase side and a component on the B-phase side, respectively.

In the A-phase signal processing circuit, the output of the light receiving element 7A is connected to the amplifying circuit 13A, and the output of the amplifying circuit 13A is connected to the + side peak value detecting circuit 14A and the -side peak value detecting circuit. In addition to being connected to the circuit 15A, it is also connected to one input terminal of the rectangular wave processing circuit 20A. The outputs of the plus side peak value detection circuit 14A and the minus side peak value detection circuit 15A are output from the rotation / stop determination circuit 18A.
Are connected to the two input terminals of
The output of the stop determination circuit 18A is connected to the control input terminal of the threshold level switching circuit 19A. The output of the positive side peak value detection circuit 14A is the resistance 16A
The output of the negative side peak value detection circuit 15A is also connected to one end of the resistor 17A. Further, the other ends of the resistors 16A and 17A are connected to each other, and this connection point is connected to a threshold level switching circuit 19.
A is connected to one input terminal, and the other input terminal of the threshold level switching circuit 19A is grounded.
The output of the threshold level switching circuit 19A is connected to the other input terminal of the rectangular wave processing circuit 20A, and the output of the rectangular wave processing circuit 20A is connected to an input port of a microprocessor (not shown).

The operation of the signal processing circuit thus configured is as follows.

First, the signal converted into an electric signal by the light receiving element 7A is amplified by the amplifier circuit 13A and then input to the one input terminal of the rectangular wave processing circuit 20A. Here, similarly to the input signal, the amplified signal output from the amplifier circuit 13A is a substantially sinusoidal analog signal as described above when the mouse body is moving at a constant speed. The amplified signal is also input to the + side peak value detection circuit 14A and the −side peak value detection circuit 15A at the same time, and the + side peak value (maximum value) V1 of the amplified signal is obtained by the both peak value detection circuits 14A and 15A. ,-Side peak value (minimum value)
V2 is detected and output. These positive side peak values V
The 1, -side peak value V2 is supplied to one end of each of the resistors 16A and 17A, and the connection point between the resistors 16A and 17A is connected to the midpoint potential Vc of V1 and V2, that is, (V1 + V
2) / 2 is obtained, and this potential Vc is supplied to one input terminal of the threshold level switching circuit 19A. The + side peak value V1 and the -side peak value V2 are also supplied to a rotation / stop determination circuit 18A. The rotation / stop determination circuit 18A blocks light based on whether the peak values V1 and V2 are equal. It is determined whether the plate 1 is stopped or rotating, and this determination signal is output to the control input terminal of the threshold level switching circuit 19A. In response to the discrimination signal, the threshold level switching circuit 19A switches the output signal to the midpoint potential Vc when the light shielding plate 1 is rotating and to the 0 level (ground level) when the light shielding plate 1 is stopped. It is supplied to the other input terminal of the rectangular wave processing circuit 20A as a threshold level of the circuit 20A. According to the threshold level thus determined, the analog amplified signal input to one input terminal of the rectangular wave processing circuit 20A is converted into a rectangular wave digital signal having a duty ratio of approximately 50%. Is input to the input port of the microprocessor (not shown) as described above.

The above description is for the signal processing circuit on the A-phase side in the X-axis direction.
The circuit configuration and operation are exactly the same in the axial direction,
These descriptions are omitted to avoid duplication. As described above, the phase difference between the A-phase signal and the B-phase signal is set so that a 90-degree phase difference is obtained. The microprocessor detects the phase difference between the two signals and the number of pulses of the digital signal. Then, the moving direction and the moving amount of the mouse body are calculated.

Next, a signal waveform obtained by the signal processing circuit shown in FIG. 10 will be described. In FIG.
(A) is the waveform of the analog A-phase signal and B-phase signal output from the amplifier circuits 13A and 13B, respectively, and (b) is
A-phase side digital signal waveform (pulse signal waveform) shaped into a rectangular wave by the phase-side rectangular wave processing circuit 20A,
(C) is a B-phase side digital signal waveform (pulse signal waveform) shaped into a rectangular wave by the B-phase side rectangular wave processing circuit 20B, and time is plotted on the horizontal axis in each waveform diagram.

Here, for the sake of simplicity, the mouse body is moved at a constant speed, and the positive side peak value V1 and the negative side peak value V2 are absolutely determined on both the A-phase side and the B-phase side. The values are assumed to be equal. The analog A-phase signal and the B-phase signal have a constant amplitude (V1-
V2) and a cycle (wavelength) T, and the phase of the A-phase signal is delayed by 90 degrees, that is, T / 4 from the phase of the B-phase signal. These analog signals are
As shown in FIGS. 11B and 11C, the midpoint potential Vc, in this case, the 0 level is set as the threshold level, and the rectangular wave processing circuits 20A and 20B respectively set the H level (for example, 5V) and L level. Level 2 (for example, 0V)
The waveform is shaped into a rectangular wave digital signal composed of values.
In the signal processing circuit shown in FIG. 10, since the midpoint potential Vc between the peak values V1 and V2 is set to the threshold level, the duty ratio of the digital signal waveform (H with respect to the period T) Level or L
The ratio of the time of the level state) becomes 50%, and the state in which the phase of the digital signal on the A-phase side is delayed by 90 degrees with respect to the digital signal waveform on the B-phase side is maintained. As described above, these digital signals are captured by the microprocessor, and the processed result is transmitted to a control device such as a host computer, for example, such that the cursor on the display moves in accordance with the movement of the mouse body. Controlled. When the mouse body is moved in the direction opposite to the direction in the case shown in FIG.
A signal waveform having a phase relationship advanced by a degree is obtained.

In the signal processing circuit of the conventional optical rotary encoder described with reference to FIGS.
When shaping the waveform of an analog amplified signal based on the outputs of the light receiving elements 7A and 7B into a rectangular digital signal, the midpoint potential Vc between the positive side peak value V1 and the negative side peak value V2.
Is the threshold level, the light receiving element 7
Even if the amount of light received by A and 7B changes and the amplified output fluctuates, there is an advantage that a stable duty ratio of 50% can be obtained and the phase difference between the A-phase signal and the B-phase signal can be reliably obtained.

[0019]

However, in the signal processing circuit of the conventional optical encoder as described above, the plus and minus side peak value detection circuits 14A and 15A, the rotation / stop determination circuit 18A, and the Requires the threshold level switching circuit 19A, and the circuit configuration is very complicated. The peak value detection circuits 14A and 14B
As an actual circuit for realizing the above, a peak hold circuit including an operational amplifier, a capacitor, and the like is generally used.
In addition, a timing generation circuit for resetting the peak hold circuit at predetermined time intervals is required. Further, when this signal processing circuit is applied to an XY coordinate input device such as a mouse, there are A-phase and B-phase in the X-axis direction and the Y-axis direction, respectively.
Each of these circuit blocks requires four sets, and the circuit configuration is further complicated, which is an obstacle in reducing the size and cost of the XY coordinate input device or the signal processing circuit of the optical encoder. .

Further, there is a possibility that the light shielding plates 1 and 2 are stopped at a position where the amplified signals output from the amplifier circuits 13A and 13B are near the 0 level. In this case, the rectangular wave processing circuit 20A , 20B, the threshold levels of the square wave processing circuits 20A,
The level of the output signal (digital signal) of 20B fluctuates by going to H level or L level, and this unstable signal is incorrectly recognized by the square wave processing circuits 20A and 20B, for example, by a microprocessor. Have done
When this signal processing circuit is employed in an XY coordinate input device such as a mouse, there is also a disadvantage that a cursor displayed on a display device such as a host computer moves against the intention of an operator such as a mouse. Was.

An object of the present invention is to provide a stable signal irrespective of the stop position of the light-shielding plate, which has a simple structure, can be reduced in size and can be manufactured at low cost, in view of the above-mentioned state of the art. An object of the present invention is to provide a signal processing circuit for an optical encoder.

[0022]

In order to achieve the object of the present invention, the present invention comprises a pair of light receiving elements which are arranged opposite to a light emitting element via a light shielding plate having a number of slits, and A signal processing circuit for an optical encoder, comprising a pair of rectangular wave processing means for shaping a particular analog waveform signal obtained from the light receiving element into a rectangular waveform, wherein the pair of rectangular wave processing means have a hysteresis characteristic. , And a DC bias voltage set between two threshold levels of the logic circuit is applied to the inputs of the logic circuits, and the outputs of the pair of light receiving elements are respectively connected to AC. The configuration is such that they are connected and connected to the inputs of the pair of logic circuits, respectively.

The light emitting element comprises a light emitting diode, and a current adjusting resistor is connected in series with the light emitting diode. The potential of the resistor or the light emitting diode is used as the DC bias voltage for the pair of logic devices. The configuration is applied to each input of the circuit.

Further, the resistor for current adjustment comprises a plurality of resistors, and at least one of the plurality of resistors is a resistor whose resistance value can be adjusted.

The logic circuit including the pair of inverters and the like is configured to be a circuit housed in the same integrated circuit package.

[0026]

The rectangular wave processing means for shaping the analog waveform signal obtained from the light receiving element into a rectangular waveform is constituted by a logic circuit composed of an inverter or the like having a hysteresis characteristic, and two threshold levels of the logic circuit are inputted to the input of the logic circuit. Apply the DC bias voltage set in between,
Since the output of the light receiving element is AC-coupled (AC-coupled) and connected to the input of the logic circuit, a voltage obtained by superimposing the AC component of the output of the light receiving element on the DC bias voltage is applied to the input of the logic circuit. The bias voltage level is supplied to the logic circuit when the light shielding plate is stopped.
The logic circuit has a hysteresis characteristic, that is, the output is H
Since the threshold level when the level changes from the L level to the L level and the threshold level when the level changes from the L level to the H level have different characteristics, the light shielding plate stops regardless of the stop state of the light shielding plate. From the logic circuit. In addition, the circuit configuration is a simple configuration including a circuit element for obtaining a DC bias voltage, a circuit element for AC coupling, and a logic circuit element including an inverter and the like. It is possible to reduce the size and cost of the entire device such as the XY coordinate input device to be incorporated.

Further, the light-emitting element is constituted by a light-emitting diode, and a current adjusting resistor is connected in series with the light-emitting diode. The potential of the resistor or the light-emitting diode is used as the DC bias voltage to be input to the logic circuit. When the bias voltage is applied, the bias voltage is obtained by using the forward voltage (forward voltage) of the light emitting diode, so that a circuit element such as a resistor for setting the bias voltage is not required, and the signal processing circuit is more improved. Can be simplified.

Further, when the current adjusting resistor connected in series with the light emitting diode is constituted by a plurality of resistors including an adjustable resistor, the threshold level of a logic circuit including an inverter or the like is set to a threshold level. Even if there is a variation, it is possible to appropriately set the DC bias voltage by adjusting the resistance value of the adjustable resistor, so that a rectangular wave ( (A binary phase pulse signal).

Further, when the logic circuit including the pair of inverters and the like is configured by a circuit housed in the same integrated circuit package, there is almost no variation in characteristics such as threshold levels of the pair of logic circuits. For,
Since only one type of DC bias voltage is input to the logic circuit, circuit elements for setting the DC bias voltage can be shared, and the number of circuit elements can be reduced.

[0030]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of a signal processing circuit for an optical rotary encoder according to the present invention. FIG. 2 is a signal waveform showing an example of a signal waveform obtained from the signal processing circuit of FIG. FIG. The signal processing circuit of FIG.
The XY coordinate input device such as a mouse as shown in FIGS. 8 and 9 is provided.
-Only a circuit portion for processing the A-phase signal and the B-phase signal in the X-axis direction of the Y coordinate input device is shown in detail. Since the internal configuration of the mouse as the XY coordinate input device provided with the signal processing circuit of the present embodiment is the same as that shown in FIGS. 8 and 9, the detailed description of the mechanism is omitted and 1, the same components as those shown in FIGS. 8 and 9 are denoted by the same reference numerals.

In FIG. 1, reference numerals 5A and 5B denote infrared light emitting diodes which are light emitting elements, and reference numeral 21 denotes a light emitting diode 5A,
A current adjusting resistor (resistance value is several hundred ohms) for limiting the current flowing to 5B, 7A and 7B are opposed to the light emitting diodes 5A and 5B via the light shielding plate 1 at the slit arrangement portion of the light shielding plate 1 shown in FIG. The arranged phototransistors (light receiving elements), 22A and 22B are emitter resistors connected to the emitters of the phototransistors 7A and 7B,
23A and 23B are Schmitt trigger input inverters having a hysteresis characteristic as a logic circuit (for example, TC4584BP of Toshiba C-MOS logic IC), 2
4A and 24B connect the outputs (emitters) of the phototransistors 7A and 7B and the inputs of the inverters 23A and 23B to A.
C (AC) coupling capacitors, 25A and 25B, connect the potential of the current adjusting resistor 21 to the inverters 23A and 23A.
An input resistor (resistance value is on the order of MΩ) applied to the input of B, and a microprocessor (MPU) 26 connected to the output terminals of the inverters 23A and 23B. In addition, alphabets A and B at the end of the code represent the components on the A-phase side and the B-phase side, respectively.

The light emitting elements 5A and 5B and the current adjusting resistor 21 are connected in series between a 5V power supply line (constant voltage) and ground, and the light receiving element 7A and the emitter resistor 2 are connected.
2A, the light receiving element 7B and the emitter resistor 22B are also connected in series between the power supply line and the ground. A connection point A between the light receiving element 7A and the emitter resistor 22A is connected to an inverter (logic circuit) 23 via a coupling capacitor 24A.
A connection point between the light receiving element 7B and the emitter resistor 22B is connected to the input terminal of the inverter A via a coupling capacitor 24B. Light emitting element 5
The connection point C between B and the current adjusting resistor 21 is connected to the coupling capacitor 24A and the inverter 23 via the input resistor 25A.
A, that is, the input terminal of the inverter 23A, and the input terminal of the inverter 23B, which is the connection point between the coupling capacitor 24B and the inverter 23B, via the input resistor 25B. Note that the potential at the connection point c is set to be a potential between a first threshold level Vth1 and a second threshold level Vth2 (preferably, an intermediate potential between the two threshold levels). ing. Further, the inverters 23A and 23B are constituted by integrated circuits (ICs) housed in the same package, and the constant voltage of 5 V is also supplied to the power supply terminals of the ICs. In addition,
Light from the light emitting elements 5A and 5B is projected onto a set of light receiving elements 7A and 7B forming a pair through a plurality of slit arrangement portions formed at a predetermined equal pitch in the circumferential direction of the light shielding plate 1. When a mouse with a built-in signal processing circuit is moved at a constant speed as described in the related art, a signal having a phase difference of 90 degrees with respect to a light receiving element is generated. Light receiving elements 7A and 7B are positioned and arranged in the mouse casing so as to be obtained from 7A and 7B.

The above configuration shows a circuit portion for processing the A-phase signal and the B-phase signal in the X-axis direction.
Since the circuit part for processing the A-phase signal and the B-phase signal in the Y-axis direction is configured in exactly the same way as the circuit part in the X-axis direction, the circuit in the Y-axis direction is not shown.

FIG. 2 is a signal waveform diagram showing an example of a signal waveform obtained in each part when the signal processing circuit shown in FIG. 1 operates when the mouse is operated at a normal constant operation speed. The voltage level is on the axis and the time is on the horizontal axis. 2A shows the waveforms of the A-phase signal and the B-phase signal obtained at the connection points A and B, and FIG.
A and B-phase signals obtained at the connection point between A and the input resistor 25A, that is, at the input terminal of the inverter 23A and the input terminal of the inverter 23B which is the connection point between the coupling capacitor 24B and the input resistor 25B. Represents each waveform and threshold levels of the inverters 23A and 23B,
(C) is a pulse signal waveform obtained from the output end of the A-phase inverter 23A, and (d) is a B-phase inverter 23B.
Represents a pulse signal waveform obtained from the output terminal of the first embodiment.

Next, the operation of the signal processing circuit according to the first embodiment will be described with reference to the schematic configuration diagram inside the mouse shown in FIG. 8 and the signal waveform diagram shown in FIG.

First, when the operator moves the mouse at a normal constant speed on a base plate (not shown) on which the mouse is placed, the light shielding plates 1 and 2 are moved in accordance with the amount and speed of the movement. (See FIG. 8) rotates, and the light shielding plate 1 in the X-axis direction
Each light emitted from the light emitting elements 5A and 5B with the rotation of
The light is transmitted or cut off in response to the non-arrival, and is supplied to the light receiving elements 7A and 7B intermittently forming a pair. Light receiving element 7
In FIGS. 2A, 7A and 7B, the continuity (the photocurrent flowing through the phototransistor) changes in response to the intermittent light supplied from the light emitting elements 5A and 5B. A-phase signal as shown in FIG.
A B-phase signal is also formed at the connection point b on the side of FIG. Here, if the characteristics of the two light emitting elements 5A and 5B and the two light receiving elements 7A and 7B are not uniform, as shown in FIG. 2A, the amplitudes and DC components (DC components) of the A-phase signal and the B-phase signal are changed. Components) are somewhat different.
Here, since the mouse is moving at a constant speed, A
Each of the phase signal and the B-phase signal has a sinusoidal waveform, and the phase difference between both waveforms is 90 degrees.

Next, the A-phase signal at the connection point A is supplied to the coupling capacitor 24A, and similarly, the B-phase signal at the connection point B is supplied to the coupling capacitor 24B, and the A-phase signal and the B-phase signal are respectively coupled. Capacitors 24A, 2
4B, and only the AC component (AC component) is transmitted to the input terminals of the inverters 23A and 23B.

The light emitting element 5B and the current adjusting resistor 2
At the connection point c with 1, a potential is obtained by subtracting the voltage drop of the light emitting elements 5A and 5B from the voltage of the power supply line of 5V. That is, the infrared light emitting diode 5 as a light emitting element
Since the forward voltage of A and 5B is generally 1.2 V as a reference value, the potential V3 at the connection point c is 2.6 V (5-
1.2 * 2) is obtained. This potential V3 is used as a DC bias voltage (hereinafter, referred to as a bias voltage) via the input resistors 25A, 25B and the inverters 23A, 23B, respectively.
It is transmitted to the input terminal of 3B. And the inverter 23A
2 (b), the AC component of the A-phase signal and the potential V3 at the connection point c are superimposed. Similarly, the potential at the input terminal of the inverter 23B is As shown in FIG. 2B, the potential is A of the B-phase signal.
The C component and the potential V3 are superimposed. In other words, the input terminals of the inverters 23A and 23B have their voltage levels swinging up and down in accordance with the amplitudes of the A-phase signal and the B-phase signal around the voltage (potential V3) which is almost half of the power supply voltage. When the light shielding plate 1 is not rotating, the levels of the A-phase signal and the B-phase signal do not change, and there is no AC component. Therefore, the potentials at the input terminals of the inverters 23A and 23B are set to the potential V3. Will be kept.

Next, the A-phase signal and the B-phase signal, which are sinusoidal analog signals centered at the potential V3, are
The waveforms are shaped into rectangular pulse signals (digital signals) by 3A and 23B, respectively. Here, since the inverters 23A and 23B are logic circuits of a Schmitt trigger input having a hysteresis characteristic, the input level (the first level) when the output changes from the H level (for example, 5V) to the L level (for example, 0V). Threshold level V
2 (b), the input level (second threshold level Vth2) when the level changes from the L level to the H level. The Toshiba TC4
In 584BP, the first threshold level Vth1 is 3.0 V, the second threshold level Vth2 is 2.3 V, and the inverters 23A,
When the voltage at the input terminal of 23B becomes 3.0 V or more, its output becomes L level (for example, 0 V), and when the voltage at the input terminal becomes 2.3 V or less, the output becomes H level (for example, 5 V).
From the output terminals of the inverters 23A and 23B,
A rectangular pulse signal waveform (digital signal) as shown in FIGS. 2C and 2D is obtained according to the amplitudes of the A-phase signal and the B-phase signal shown in FIG.

The A-phase side and the B-phase waveform thus shaped
The phase-side digital signal is supplied to the input port of the microprocessor 26 connected to the output terminals of the inverters 23A and 23B, as described in the related art. Then, this microprocessor 26 has the configuration shown in FIGS.
The direction of movement (right or left) of the mouse in the X-axis direction component is determined based on the delay and advance of the phase of the digital A-phase signal and B-phase signal shown in FIG. The movement amount in the determined direction is obtained from the number of edges obtained by combining the above and the B-phase signal. Note that the waveform-shaped digital A-phase signal and B-phase signal are different from each other in amplitude difference between the A-phase signal and the B-phase signal in the analog waveform and the first and second threshold levels V.
The phase difference is completely 90 due to the influence of th1 and Vth2.
Although the degree is not so high, the relationship between the phase advance and the delay is maintained, so that the microprocessor 26 does not erroneously determine the moving direction of the mouse.

In the above description, the analog A-phase signal and the B-phase signal in the X-axis direction are subjected to waveform shaping processing to obtain two pulse waveform signals having different digital phases. The signal processing circuit and the signal processing operation when two pulse waveform signals having different phases are obtained from the analog A-phase signal and the B-phase signal are completely different from those in the X-axis direction described with reference to FIGS. Similar, so
Description in the Y-axis direction is omitted. The digital A-phase signal and the B-phase signal in the Y-axis direction are also supplied to the input port of the microprocessor 26, and similarly to the X-axis direction, the direction of movement of the mouse in the Y-axis direction component (forward or backward) ) And the amount of movement in that direction. Then, by combining these data in the X-axis direction and the Y-axis direction, the moving direction and the moving amount as the mouse are determined, and as a result, necessary control such as the movement of the cursor in accordance with the movement of the mouse is performed. Is performed by a control device such as a host computer connected thereto.

As described above, in the first embodiment of the present invention, the rectangular wave processing circuit for shaping the analog waveform signals obtained from the light receiving elements 7A and 7B into a rectangular digital waveform is provided by the inverter 23A having the hysteresis characteristic. 23B
A bias voltage (potential V3) set to a potential between two threshold levels Vth1 and Vth2 of the inverters 23A and 23B is applied to the input terminals of the inverters 23A and 23B, and the light receiving element 7A , 7B in an AC-coupled manner, the input terminals of the inverters 23A, 23B are supplied with a voltage in which the AC component of the output of the light receiving elements 7A, 7B is superimposed on the bias voltage. Become. When the light shielding plate 1 is stopped, as described above, the levels of the A-phase signal and the B-phase signal appearing at the connection points A and B do not change, and the potentials at the input terminals of both the inverters 23A and 23B change. Is also kept at the potential V3 as the bias voltage set between the threshold levels Vth1 and Vth2, so that the output ends of the inverters 23A and 23B having hysteresis characteristics are independent of the stop position of the light shielding plate 1. Is
The level (H level or L level) immediately before the stop of the light shielding plate 1 can be stably obtained. Therefore, the level of the input port of the microprocessor 26 to which the inverters 23A and 23B are connected is also stabilized, and the microprocessor 26 performs erroneous recognition. As a result, a display device such as a host computer to which the mouse is connected is connected. Is not controlled against the intention of the mouse operator.

In the first embodiment described above,
The characteristics of the light emitting elements 5A and 5B and the light receiving elements 7A and 7B vary or the characteristics change over time, and the output voltage of the phototransistor as the light receiving element, that is, the A-phase signal and the B-phase signal at the connection points A and B Even if there is a difference between the amplitude and the DC component between them, the signals are AC-coupled and transmitted to the inverters 23A and 23B. 2
Since two pulse signals having a phase difference can be reliably obtained from the output terminal of 3B, the rotation direction of the light shielding plate 1 (ball 9) is not erroneously detected.

The waveform shaping circuit for obtaining a rectangular wave in the first embodiment includes inverters 23A and 23B.
And a very small number of circuit elements including coupling capacitors 24A and 24B and input resistors 25A and 25B connected to the input terminals of the inverters 23A and 23B, thereby greatly simplifying the signal processing circuit. Therefore, the signal processing circuit of the optical rotary encoder and the X-
The size and cost of the Y coordinate input device can be reduced.

Further, in the first embodiment, the light emitting element is constituted by the light emitting diodes 5A and 5B, and connected in series with the light emitting diodes 5A and 5B.
Current adjusting resistor 21 for limiting current flowing through A and 5B
Of the inverter 23A,
Since the bias voltage is obtained by using the forward voltage of the light emitting diodes 5A and 5B by applying the voltage to the input terminal of the input terminal 23B, there is no need to separately provide a circuit element such as a resistor for setting the bias voltage, and the signal The circuit configuration of the processing circuit can be made simpler. Since the forward voltages of the light emitting diodes 5A and 5B have little variation, a stable bias voltage is applied to the inverters 23A and 23B.
To the inverters 23A and 2A.
From 3B, a pulse waveform with a stable duty ratio can be obtained.

In the first embodiment, a C-MOS logic IC containing six (six) inverter circuits is used as the inverters 23A and 23B.
(TC4584BP). Therefore, characteristics such as threshold levels of the two inverters 23A and 23B hardly vary. If these variations cannot be ignored, it is necessary to set a bias voltage according to each inverter. In the embodiment of the present invention, such a need is eliminated, only one kind of bias voltage is required, and a circuit element (current adjusting resistor 21) for setting the bias voltage can be shared, and the number of circuit elements can be reduced. The circuit configuration of the signal processing circuit can be further simplified. Since the C-MOS logic IC has six circuits, the inverter in the Y-axis direction also uses the other two circuits in the IC, so that four inverters as rectangular wave processing means mounted on the mouse are used. The inverter can be constituted by one IC.

In the first embodiment, even when the mouse is moved at a slow operation speed, the analog A-phase signal and the B-phase signal appearing at the connection points A and B are output from the light emitting elements 5A and 5B. The light changes in an analog (sinusoidal) manner in accordance with the cutoff or transmission of the light by the light shielding plate 1, and these signals also have an AC component. Then, as the operation speed of the mouse, more precisely, the rotation speed of the light shielding plates 1 and 2 becomes slower, the change in the amplitude of the A-phase signal and the B-phase signal also becomes slower.
And the amplitude of the A-phase signal and the B-phase signal at the input terminals of the inverters 23A and 23B become smaller after AC coupling. This is because the AC components of the A-phase signal and the B-phase signal obtained from the light receiving elements 7A and 7B decrease as the rotation speed of the light shielding plate 1 decreases. Although the charge / discharge speed does not completely catch up with the change in the amplitude of the A-phase signal and the B-phase signal,
When the rotation speed of the light shielding plate 1 becomes lower than a certain speed (minimum speed vt), A at the input terminals of the inverters 23A and 23B is reduced.
The amplitude of the phase signal and the phase B signal is reduced, and the inverter 2
The voltage at the input terminals of 3A and 23B does not become higher than the first threshold level Vth1, or conversely, does not become lower than the second threshold level Vth2. As described above, the levels of the A-phase signal and the B-phase signal at the input terminals of the inverters 23A and 23B are
A, 23B both threshold levels Vth1 and Vt
During the interval h2, the output levels of the inverters 23A and 23B do not change, and as a result, the movement of the cursor and the like displayed on the display device is not controlled. However, the minimum speed vt at which the outputs of the inverters 23A and 23B do not change depends on the coupling capacitors 24A and 24B and the input resistors 25A,
The value can be adjusted by changing the value of 25B, and in this embodiment, the time constant is set so that the minimum speed vt does not hinder practical use.

When the mouse is moved slowly,
The fact that the output levels of the inverters 23A and 23B do not change has the following effects. That is, for example,
When a straight line or the like is drawn on the display device, the cursor or the like is moved only in the X-axis direction (or the Y-axis direction). Mouse only in the direction)
It is extremely difficult to use a ruler.
An axial (or X-axis) component is present. However, a direction (eg, Y-axis direction) orthogonal to the direction in which the cursor or the like is to be moved (eg, X-axis direction)
Is extremely slow, that is, the rotation speed of the light shielding plate 2 is extremely low.
Since the output of the inverter (not shown) in the axial direction does not change, it is possible to easily move the cursor or the like only in the X-axis direction. This effect when the mouse is slowly moved is similarly exerted in the second and third embodiments described later. The user operates the trackball ball instead of the mouse to move the cursor or the like on the X-axis. Alternatively, the same can be said for the case of moving only in the Y-axis direction.

The configuration for obtaining the bias voltage supplied to the input terminals of the inverters 23A and 23B by using the forward voltages of the infrared light emitting diodes 5A and 5B is limited to that shown in FIG. Instead, for example, a configuration as shown in FIG. The resistance value of each current adjusting resistor connected in series with the light emitting diodes 5A and 5B is set so that the bias voltage obtained by these modifications also falls between the two threshold levels Vth1 and Vth2 of the inverter. Have been.

FIG. 3A shows a current adjusting resistor 21a, a light emitting diode 5A, and a light emitting diode 5 in order from a power supply voltage (power supply line) of 5V to GND (ground).
B, a current adjusting resistor 21b is connected in series to obtain a bias voltage of 2.6 V from a connection point between the current adjusting resistor 21a and the light emitting diode 5A;
As in the embodiment, the voltage obtained by superimposing the A-phase signal and the B-phase signal after AC coupling on the bias voltage is applied to the inverter 23.
A and 23B are respectively supplied to the input terminals.

FIG. 3B shows a current adjusting resistor 21c, a light emitting diode 5A, a light emitting diode 5B, and a current adjusting resistor 21d in order from the power supply voltage of 5V toward GND.
Are connected in series, and a bias voltage of 2.6 V is obtained from the connection point between the two light emitting diodes 5A and 5B.
Similarly to this, this bias voltage is applied to the inverters 23A and 23A.
B is supplied to the input terminal of B.

FIG. 3C shows that the current adjusting resistor 21e, the light emitting diode 5A, and the light emitting diode 5B are connected in series from the power supply voltage of 5V toward GND, and the connection between the light emitting diodes 5A and 5B. A bias voltage is obtained from the point, and the voltage is 1.2 V which is a forward voltage of the infrared light emitting diode. In this modification, although the inverter is not shown, the TTL logic IC (7
4LS14), and the reference values of the first and second threshold levels Vth1 and Vth2 of the TTL logic IC when the power supply voltage is 5V are 1.6V and 0.8V, respectively. The value of 1.2V of the bias voltage is the most preferable value located at an intermediate value between the two threshold levels.

FIG. 3D shows a current adjusting resistor 21f, a light emitting diode 5A, a current adjusting resistor 21g, and a light emitting diode 5B in order from the 5V power supply voltage to GND.
Are connected in series and input to the A-phase and B-phase inverters from the connection point between the light emitting diode 5A and the current adjustment resistor 21g and the connection point between the current adjustment resistor 21g and the light emitting diode 5B, respectively. First and second bias voltages are obtained. In this way, by making the bias voltages on the A-phase side and the B-phase side different, the ICs constituting the A-phase side and the B-phase side inverters are different, and the characteristics such as the threshold level of both inverters are changed. It is possible to cope with the case where there is a difference.

As described above with reference to the modified example based on FIG. 3, the bias voltage should be between the two threshold levels Vth1 and Vth2 of the inverter, preferably, an intermediate value between them. Thus, a configuration for obtaining various bias voltages can be adopted.

FIG. 4 is a circuit diagram showing a second embodiment of the signal processing circuit for an optical rotary encoder according to the present invention. As in the first embodiment, the mouse and the like shown in FIGS. 4 is provided in the XY coordinate input device for detecting the rotation of the ball, and FIG. 4 shows only a circuit portion for processing the A-phase signal and the B-phase signal in the X-axis direction.

In FIG. 4, reference numerals 27 and 28 denote bias voltage setting resistors (hereinafter, referred to as bias resistors).
In addition, the same components as those shown in FIG. 1 are denoted by the same reference numerals.

The difference between the second embodiment and the first embodiment is that in the first embodiment, the connection point c between the light emitting element 5B and the current adjusting resistor 21 is input. While the bias voltage is obtained by connecting to the input terminals of the inverters 23A and 23B via the resistors 25A and 25B, in the present embodiment, in order to obtain the bias voltage, between the power supply line of 5V and the ground. Bias resistor 2 connected in series
7 and 28 are separately provided, and the connection point D of the two bias resistors 27 and 28 is connected to the input terminals of the inverters 23A and 23B via the input resistors 25A and 25B, respectively, and the potential at the connection point D is used as the bias voltage. In this respect, only the configuration is the same as that of the above-described first embodiment, and the detailed description of the same portions will be omitted to avoid duplication.

The inverters 2 on the A-phase side and the B-phase side
The input terminals of 3A and 23B are supplied with voltages in which the A-phase signal and the B-phase signal (analog signal) from which the DC components have been removed by the coupling capacitors 24A and 24B are superimposed on the bias voltage at the connection point d, respectively. As shown in FIG. 2, inverters 23A and 23A having hysteresis characteristics
The waveform is shaped into a rectangular pulse signal (digital signal) by 3B. Here, the potential at the connection point d is 2.65 V which is an intermediate potential between the two threshold levels Vth1 and Vth2 of the inverters 23A and 23B.
The resistance values of the bias resistors 27 and 28 are set such that A pulse signal having a phase difference obtained from the output terminals of the inverters 23A and 23B is supplied to an input port of a microprocessor 26 at the next stage, as in the first embodiment. The direction and amount of movement in the direction component are obtained.

The circuit configuration for processing the A-phase signal and the B-phase signal in the Y-axis direction and the signal processing operation in this embodiment are the same as those in the X-axis direction described with reference to FIG. The A-phase signal and the B-phase signal in the Y-axis direction, which have been waveform-shaped, are also supplied to the microprocessor 26 to determine the direction and amount of movement of the mouse in the Y-axis direction component.

In the second embodiment of the present invention, the bias voltage is changed to a dedicated bias resistor 2.
7, 28, the light emitting diodes 5A, 5B
, The bias voltage can be easily set to an arbitrary voltage such as an intermediate voltage between the first and second threshold levels Vth1 and Vth2 of the inverters 23A and 23B. Therefore, for example, a logic IC having a power supply voltage of 3.3 V is employed as the inverters 23A and 23B, and when obtaining a bias voltage of 0.8 V, for example, which matches the threshold level of the IC, the light emitting diodes 5A and 5B The resistance values of the bias resistors 27 and 28 can be set without worrying about the current flowing through the bias resistors 27 and 28.

FIG. 5 is a plan view showing a schematic configuration of the inside of a mouse provided with a signal processing circuit for an optical rotary encoder according to a third embodiment of the present invention, and FIG. 6 is a light receiving device arranged in the mouse shown in FIG. FIG. 6A is an explanatory view showing the external appearance of the element and the internal circuit. FIG. 6A is an external view of the light receiving element, and FIG.
FIG. 7 is a circuit diagram of a light receiving element, and FIG. 7 is a circuit configuration diagram showing a third embodiment of an optical rotary encoder signal processing circuit according to the present invention provided in the mouse of FIG. 5, and FIG. Only a circuit portion for processing the A-phase signal and the B-phase signal in the X-axis direction of the mouse is shown in detail.

In FIG. 5, reference numerals 1 and 2 denote disc-shaped light shielding plates (rotary encoder plates) made of a non-transparent synthetic resin formed by molding, and reference numerals 3 and 4 are integrally formed with the light shielding plates 1 and 2. A rotating shaft 9 whose axial directions are orthogonal to each other is rotated by the movement of the mouse, and a ball that transmits the rotation to the rotating shafts 3 and 4 is in contact with the ball 9, and a rotatable urging roller 11 is A spring for biasing the ball 9 in both axial directions of the two rotating shafts 3 and 4 via a biasing roller 10. These components are the same as those described above with reference to FIGS. 8 and 9. Therefore, the same components as those shown in FIG. 8 are denoted by the same reference numerals, and a detailed description of the same components will be appropriately omitted as necessary to avoid duplication of description. Reference numerals 35 and 36 denote light-emitting elements composed of infrared light-emitting diodes, and reference numerals 37 and 38 denote light-receiving elements (packages). Of the reference numerals 1 to 4 and 35 to 38, odd numbers indicate an X-axis direction and even numbers. Represents a component in the Y-axis direction.

The light receiving element 37 in the X-axis direction is shown in FIG.
As shown in FIG. 7, two phototransistors 37A and 37B forming a pair are arranged in close proximity to each other in the package, and both phototransistors 37A and 37B are chips formed on the same semiconductor wafer. In addition, characteristics such as light sensitivity and amplification rate are uniform. Similarly, the light-receiving element 38 in the Y-axis direction also has two phototransistors 38A and 38B, which are a pair of chips formed on the same semiconductor wafer, arranged close to and parallel to each other in a package. , 38B have the same characteristics. The alphabets A and B at the end of the code represent the components on the A-phase side and the B-phase side, respectively, and the phototransistors 37A and 37B (38
6A are connected and shared inside the light receiving element as shown in FIG. 6B.
3 shows only three terminals in the external view of the light receiving element.

As shown in FIGS. 8 and 9, a large number of slits 12 are formed and arranged at predetermined equal pitches in the circumferential direction of the light-shielding plates 1 and 2 at the center thereof.
The rotating shafts 3 and 4 are integrally formed so that the axial direction is perpendicular to the plate surfaces of the light shielding plates 1 and 2. A light emitting element 35 and a light receiving element 37 are opposed to each other at the slit arrangement portion of the light shielding plate 1 with the light shielding plate 1 interposed therebetween, thereby forming a pair with the light emitting element (light emitting diode) 35 by a phototransistor 37A, 37B are arranged to face each other so as to sandwich the slit arrangement portion. Similarly, a light-emitting element 36 and a light-receiving element 38 are also arranged opposite to each other in the slit arrangement portion of the light-shielding plate 2 via the light-shielding plate 2, thereby forming a pair with the light-emitting element (light-emitting diode) 36. A set of 38A and 38B are arranged to face each other with the slit arrangement portion interposed therebetween. In a mouse case (not shown), the light-shielding plate 1 and the rotating shaft 3 and the light-shielding plate 2 and the rotating shaft 4 are rotatably supported, respectively, and a part of both of the rotating shafts 3 and 4 has its peripheral surface rotated. Possible ball 9
The urging roller 10 is pressed against the ball 9 by the elastic force of the spring 11. For this reason,
The ball 9 is always urged in the directions of the two rotating shafts 3 and 4, so that the ball 9 and the two rotating shafts 3 and 4 make good frictional contact. The axes of the two rotating shafts 3 and 4 are Y.
It is arranged orthogonally so as to face the axial direction and the X-axis direction,
With respect to these axes, the ball 9
And the biasing roller 10 biases the rotating shafts 3 and 4 in a direction intermediate between the X-axis direction and the Y-axis direction, that is, in a direction of approximately 45 degrees.

As is clear from the above description, the difference in mechanical structure between the mouse in this embodiment and the mouse shown in FIG. 8 is that the mouse shown in FIG. The light-emitting elements 5A, 5B, 6A, 6B and the light-receiving elements 7A, 7B, 8A, 8B each of which is paired with the light-emitting elements 5A, 5B, 6A, 6B are separately provided for each phase, whereas in the present embodiment shown in FIG. , The light emitting elements 35 and 36 are configured by a common light emitting diode on the A phase side and the B phase side,
The light receiving elements 37 and 38 are configured such that two phototransistors 37A and 37B and 38A and 38B for the A-phase side and the B-phase side formed on the same semiconductor wafer are respectively housed in the same package. It is in. Then, the phototransistors 37A, 37B or 38
The positions of the two phototransistors are determined in accordance with the pitch of the slit 12 so that the A-phase signal and the B-phase signal having phases shifted by 90 degrees from A and 38B are obtained. Note that the light emitting element 35 on the X-axis direction side sandwiches the light shielding plate 1 so that the center thereof is located at an intermediate point between the two phototransistors 37A and 37B so that light is irradiated equally to the two phototransistors 37A and 37B. Similarly, the light emitting element 36 and the light receiving element 38 are arranged such that light is emitted from the light emitting element 36 on the Y axis direction side to the phototransistors 38A and 38B equally.

The operation of the mouse according to the present embodiment is almost the same as the operation of the mouse shown in FIG. 8, and here, the main points of the operation will be described.

When the operator grips the mouse body (casing) and moves it on a base plate (not shown), the ball 9 rotates due to friction between the base plate and the ball 9.
As the ball 9 rotates, the two rotating shafts 3 and 4 that are in frictional contact with the ball 9 rotate, and the two light shielding plates 1 and 2 that are integrally formed with the two rotating shafts 3 and 4 simultaneously. Rotate. When the light shielding plates 1 and 2 rotate, the phototransistors 37A and 37B forming a pair from the light emitting element 35
And the light from the light emitting element 36 to the pair of phototransistors 38A and 38B,
A pair of both phototransistors 37A and 37B, which alternately block or transmit light, is formed by a number of slits 12 provided at a predetermined equal pitch on both light shielding plates 1 and 2, and A pair of phototransistors 38A and 38B, which form a pair, respectively transmit an A-phase signal and a B-phase signal corresponding to the blocking or transmission of the light. When the mouse is moved at a constant speed, the A-phase signal and the B-phase signal are substantially sinusoidal analog waveform signals, and the phase difference between the A-phase signal and the B-phase signal is 90%. , That is, the phototransistors 37A, 37B and 38 in the light receiving elements 37 and 38 with respect to the slit 12 so as to have a 1/4 cycle.
A, 38B are arranged.

Next, the A-phase signal and the B-phase signal are converted into two rectangular wave digital signals (binary phase pulse signals) in a signal processing circuit according to a third embodiment of the present invention described below with reference to FIG. ), And the microprocessor performs an operation or the like on the two digital signals in the same manner as in the first embodiment.
The moving direction and the moving amount of the X-axis component and the Y-axis component of the mouse body corresponding to the rotation of the ball 9 are detected.

In FIG. 7, reference numeral 35 denotes an infrared light emitting diode which is the light emitting element shown in FIG.
Phototransistor as a light receiving element shown in
FIG. 7 shows only a circuit portion for processing the A-phase signal and the B-phase signal in the X-axis direction. In the figure, reference numeral 30 denotes a current adjusting resistor for limiting the current flowing through the light emitting diode 35, and reference numeral 31 denotes a trimming resistor whose resistance value can be adjusted. The other components are the same as those shown in FIG. Have the same reference numerals. Note that, similarly to the first embodiment shown in FIG.
The components on the phase side and the phase B side are shown.

The difference between the third embodiment shown in FIG. 7 and the first embodiment described above is that
The two light emitting elements (light emitting diodes) 5A and 5B and the current adjusting resistor 21 are connected in series between the power supply line of 5 V and the ground, and the potential of the connection point c between the light emitting diode 5B and the current adjusting resistor 21 is changed to the inverter 23A. , 23B, the input voltage of the light emitting diode 35, the current adjusting resistor 30, and the trimming resistor 31 are connected between the power supply line of 5V and the ground.
Are connected in series, the connection point E between the current adjusting resistor 30 and the trimming resistor 31 is connected to the input terminals of the inverters 23A and 23B via the input resistors 25A and 25B, respectively, and the potential of the connection point E is biased. Since this embodiment uses a voltage, and the other configuration of the present embodiment is the same as that of the above-described first embodiment, a detailed description of the same portions will be omitted to avoid redundant description.

Although not shown, the trimming resistor 31 is composed of a chip resistor having a carbon resistor printed between electrodes on a ceramic substrate, and a part of the carbon resistor is laser trimmed. This is a resistor that can increase the resistance value between the electrodes by shaving off. And this trimming resistor 31
Is connected in series with the light emitting diode 35 and the current adjusting resistor 30 as shown in FIG.
The current I flowing through 5 changes. Further, the potential of the connection point E is determined by the voltage drop due to the current I flowing through the trimming resistor 31. As described above, the trimming resistor 31 has a function as a resistor for adjusting the current flowing through the light emitting diode 35 and a function as a resistor for setting the bias voltage supplied to the inverters 23A and 23B. Note that the potential of the connection point E changes accurately depending on the current flowing through the input resistors 25A and 25B, but the resistance of the trimming resistor 31 (for example, 120Ω).
), The resistance of the input resistors 25A and 25B (for example, about 1 MΩ) is set sufficiently large, so that the potential of the connection point E is practically the potential of the current I and the resistance of the trimming resistor 31. It can be thought that it is determined.

The A-phase side and B-phase side inverters 2
The input terminals of 3A and 23B are connected to the potential (bias voltage) of the connection point E by DC coupling capacitors 24A and 24B.
A voltage on which the analog A-phase signal and the B-phase signal from which the components have been removed is superimposed is supplied, and the inverters 23A and 23B of the Schmitt trigger input having a hysteresis characteristic (Toshiba C-C The waveform is shaped into a rectangular pulse signal (digital signal) by the MOS logic IC (TC4584BP).

Here, the potential at the connection point E is equal to the two threshold levels V of the inverters 23A and 23B.
The potential is set to the optimum potential between th1 and Vth2, and the setting is performed as follows in the manufacturing process of the mouse by adjusting the resistance value of the trimming resistor 31. That is, in a state before the trimming resistor 31 is laser-trimmed, the potential at the connection point E is an intermediate potential between the two threshold levels on the specification.
The resistance values of the current adjusting resistor 30 and the trimming resistor 31 are set so as to be about 2.55 V, which is somewhat lower than 5 V. Then, the rotating shaft 3 is fixed by a jig (not shown).
Is rotated at a constant speed, and the trimming resistor 31 is laser-trimmed while observing a pulse signal obtained from the output terminal of the inverter 23A with a measuring instrument such as an oscilloscope. In response to the laser trimming, the resistance value of the trimming resistor 31 gradually increases, and as the resistance value increases, the bias voltage also gradually increases from 2.55 V, and at the same time, the duty ratio of the pulse signal also becomes the optimum value. Approaching 50%. Then, when the duty ratio becomes approximately 50% (for example, 45 to 55%), the trimming of the trimming resistor 31 is terminated. In this way, by adjusting the resistance value of the trimming resistor 31 in the manufacturing process of the mouse, the potential of the connection point E can be set to an optimum value that matches the characteristics of the individual inverter 23A. Note that also in the third embodiment, since the inverters 23A and 23B are constituted by integrated circuits housed in the same package,
There is almost no variation in characteristics such as threshold levels of the two inverters 23A and 23B.
If the resistance value of the trimming resistor 31 is adjusted according to the output waveform of the A-phase side inverter 23A, the value is also an appropriate value in the B-phase side inverter 23B. Since the duty ratios of the pulse signals output from the inverters 23A and 23B are set to be almost optimal, the phase difference between these pulse signals (the A-phase signal and the B-phase signal) is also the optimal value of 90 degrees ( A quarter cycle) can be obtained. Such a pulse signal is supplied to the input port of the next-stage microprocessor 26 as in the first embodiment, and the microprocessor 26 determines the direction and amount of movement of the mouse in the X-axis direction.

The circuit configuration for processing the A-phase signal and the B-phase signal in the Y-axis direction and the signal processing operation in this embodiment are the same as those in the X-axis direction described with reference to FIG. The A-phase signal and the B-phase signal in the Y-axis direction which have been waveform-shaped are also supplied to the microprocessor 26 to determine the direction and amount of movement of the mouse in the Y-axis direction. By synthesizing the data, the moving direction and the moving amount as the mouse can be calculated.

In the third embodiment of the present invention having such a configuration, the light emitting diode 35, the current adjusting resistor 30 and the trimming resistor 31 are connected in series, and the connection point E serving as a bias voltage is connected. Potential trimming resistor 31
Is adjusted by laser trimming to adjust the resistance value, so that even if characteristics such as threshold levels of the inverters 23A and 23B vary, a bias voltage suitable for the characteristics can be set.
Therefore, the phase is almost 9 from inverters 23A and 23B.
A pulse signal shifted by 0 degrees is reliably obtained, and the phase is not erroneously detected by a signal processing circuit such as the microprocessor 26 at the next stage. Moreover, in this embodiment, the inverter 2
3A and 23B are composed of integrated circuits (ICs) housed in the same package.
3A and 23B are logic circuits formed on the same semiconductor wafer, and their characteristics such as threshold levels are almost the same. Therefore, the trimming resistor 31 whose resistance value can be adjusted can be shared between the A-phase side and the B-phase side, and the bias voltage is set by adjusting this one trimming resistor 31 so that both the A-phase side and the B-phase side are adjusted. Can be set appropriately.

Further, in the third embodiment, the light emitting diode 35 is common to the A-phase side and the B-phase side, and the light receiving element 37 is a pair of two phototransistors 37A, which are arranged in parallel in the same package. 37B.
Therefore, the characteristics of the phototransistors 37A and 37B, such as light sensitivity, and the time-dependent characteristics are uniform, and since the light-emitting element 35 is common, the analog output signals obtained from the phototransistors 37A and 38B, respectively. The amplitudes of the (A-phase signal and the B-phase signal) become substantially equal over time, and the AC components of these signals are waveform-shaped by the inverters 23A and 23B. The duty ratio of the pulse signal can always be substantially equal between the A-phase side and the B-phase side.

Further, in the third embodiment, the light emitting element is constituted by one light emitting diode 35, and the current adjusting resistor 30 for limiting the current flowing through the light emitting diode 35.
The bias voltage is obtained by using the voltage at the connection point E between the inverter and the trimming resistor 31 as a bias voltage, and the bias voltage is obtained by using the voltage drop caused by the current flowing through the trimming resistor 31. There is no need to separately provide a resistor for setting the supplied bias voltage,
The circuit configuration of the signal processing circuit of the optical encoder can be simplified, so that the size of the circuit board and the entire device inside the XY coordinate input device such as a mouse and a trackball provided with the signal processing circuit can be reduced. The price can be reduced.

In the third embodiment of the present invention, the trimming resistor 31 is used as an adjustable resistor.
However, a semi-fixed resistor can be employed instead of the trimming resistor 31. Further, the number of adjustable resistors is not limited to one. For example, the current adjusting resistor 30 shown in FIG. 7 may be replaced with a trimming resistor or a semi-fixed resistor to provide a plurality of adjustable resistors. May be connected to the light emitting diode 35 in series.

The second and third aspects of the present invention as described above
In this embodiment, as in the first embodiment, the input terminals of the inverters 23A and 23B are connected to the inverters 23A and 23B.
B: two threshold levels Vth1, Vth2
The light receiving elements 7A and 7B (3
7A, 37B) are supplied. When the light shielding plate 1 is stopped,
Since the output levels of the light receiving elements 7A and 7B (37A and 37B) do not change and the potentials at the input terminals of the two inverters 23A and 23B are kept at the set bias voltage, the stop position of the light shielding plate 1 is not related. In addition, the level (H level or L level) immediately before the stop of the light shielding plate 1 can be stably obtained from the output terminals of the inverters 23A and 23B having the hysteresis characteristic. Therefore, the inverters 23A,
The level of the input port of the microprocessor 26 to which the 23B is connected is also stabilized, and the microprocessor 26 recognizes an erroneous state, and a cursor or the like displayed on a display device such as a host computer to which the mouse is connected operates the mouse. It can be prevented from moving against the intention of the person.

In the second and third embodiments,
There is a variation in the characteristics of each optical element, and a difference may occur between the A-phase side and the B-phase side in the amplitude or DC component of the output voltage (analog signal) of the phototransistor as the light receiving element (particularly, in the second embodiment). Case), even if the amplitude of the output voltage or the level of the DC component changes due to a change over time, since those analog signals are AC-coupled and transmitted to the inverters 23A and 23B, the difference and the level of the amplitude and the DC component are changed. The influence of the change is unlikely to extend to a rectangular wave, and two pulse signals having a phase difference can be reliably obtained from the output terminals of the inverters 23A and 23B, so that the rotation direction of the light shielding plate 1 (ball 9) is erroneously detected. Never.

The waveform shaping circuit for obtaining the rectangular wave in the second and third embodiments is the same as the inverter 2
3A, 23B, the inverters 23A, 2B
Coupling capacitors 24A, 24 connected to the input terminal of 3B
Since the signal processing circuit is made up of a very small number of circuit elements such as B and the input resistors 25A and 25B, the signal processing circuit can be greatly simplified. Therefore, the signal processing circuit of the optical rotary encoder and this signal processing circuit It is possible to reduce the size and cost of the XY coordinate input device such as a mouse to be incorporated.

Further, in the second and third embodiments, as in the first embodiment, an inverter 23 is provided.
As A and 23B, 2 in a C-MOS logic IC (TC4584BP) housing six inverter circuits.
Circuit is used. Therefore, both inverters 23A and 23B are constituted by logic circuits formed on the same semiconductor wafer.
Since the characteristics such as the threshold level of B are almost the same, only one kind of bias voltage is required, and the circuit elements for setting the bias voltage can be shared. Can be further simplified. Since the C-MOS logic IC has six circuits, the inverter in the Y-axis direction also uses the other two circuits in the IC, so that four inverters as rectangular wave processing means mounted on the mouse are used. The inverter can be constituted by one IC.

When the second and third embodiments of the present invention are applied to a mouse or the like and the cursor or the like is to be moved only in the X-axis direction or the Y-axis direction, the direction in which the cursor or the like is to be moved is The moving speed in the direction (for example, the Y-axis direction) orthogonal to the (for example, the X-axis direction), that is, the rotation speed of the light-shielding plate 2, becomes extremely slow, and for the same reason as described in the first embodiment, the Y-axis is used. Since the output of the inverter (not shown) in the direction does not change, the cursor or the like can be easily moved only in the X-axis direction. The same applies to the case where the cursor or the like is moved only in the X-axis or Y-axis direction by rotating the trackball.

In the first to third embodiments of the present invention, as the logic circuit constituting the rectangular wave processing means, the inverter 23 whose input level and output level are inverted is used.
The signal processing circuit using A and 23B has been described.
The present invention is not limited to this, and a buffer in which the input level and the output level are not inverted may be used. Alternatively, instead of the inverters 23A and 23B, a logic in which the input terminals of a two-input NAND circuit of a Schmitt trigger input are connected. A circuit may be employed.

Further, in each embodiment, the mouse having the configuration shown in FIG. 8 or 5 in which the signal processing circuit of the optical rotary encoder is incorporated has been described. It is needless to say that this signal processing circuit can be applied to a track ball that takes the

[0087]

As described above, according to the present invention,
A rectangular wave processing means for shaping an analog waveform signal obtained from the light receiving element into a rectangular waveform is constituted by a logic circuit including an inverter having hysteresis characteristics, and an input of the logic circuit is set between two threshold levels of the logic circuit. In addition to applying the applied DC bias voltage and connecting the output of the light receiving element to the input of the logic circuit by AC coupling (AC coupling), when the light shielding plate is stopped, the bias voltage level is reduced. Since the signal is input to the logic circuit, the output level immediately before the stop of the light shield plate can be stably obtained from the logic circuit regardless of the stop state of the light shield plate. There is no false detection. Further, the circuit configuration of the signal processing circuit is a simple configuration such as a circuit element for obtaining a DC bias voltage, a circuit element for AC coupling, and a logic circuit element including an inverter and the like. It is possible to reduce the size and cost of the entire device such as an XY coordinate input device in which the processing circuit is incorporated.

Further, the light emitting element was composed of a light emitting diode, a resistor for current adjustment was connected in series with the light emitting diode, and the potential of the resistor or the light emitting diode was applied as a DC bias voltage to the input of a logic circuit. In this case, since a bias voltage can be obtained by using a forward voltage (forward voltage) of the light emitting diode, a circuit element such as a dedicated resistor for setting the bias voltage is not required.
The circuit configuration of the signal processing circuit can be simplified.

Further, when the current adjusting resistor connected in series with the light emitting diode is constituted by a plurality of resistors including an adjustable resistor, the threshold level of a logic circuit such as an inverter is set to the threshold level. Even if there is a variation, it is possible to appropriately set the DC bias voltage by adjusting the resistance value of the adjustable resistor, so that a rectangular wave ( (A binary phase pulse signal).

When the logic circuit including the pair of inverters and the like is constituted by a circuit housed in the same integrated circuit package, there is almost no variation in characteristics such as threshold levels of the pair of logic circuits. For,
Since only one type of DC bias voltage is input to the logic circuit, circuit elements for setting the DC bias voltage can be shared, and the number of circuit elements can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a signal processing circuit for an optical rotary encoder according to the present invention.

FIG. 2 is a signal waveform diagram showing an example of a signal waveform obtained from the signal processing circuit of FIG.

FIG. 3 is a partial circuit configuration diagram showing a modification of the first embodiment of the present invention shown in FIG.

FIG. 4 is a circuit diagram showing a second embodiment of the signal processing circuit for an optical rotary encoder according to the present invention.

FIG. 5 is a plan view showing a schematic configuration inside a mouse provided with a signal processing circuit for an optical rotary encoder according to a third embodiment of the present invention.

6A and 6B are explanatory diagrams showing an appearance and an internal circuit of a light receiving element arranged on the mouse shown in FIG. 5, FIG. 6A is an external view of the light receiving element, and FIG. 6B is a circuit of the light receiving element; FIG.

FIG. 7 is a circuit diagram showing a third embodiment of the signal processing circuit for an optical rotary encoder according to the present invention provided in the mouse of FIG. 5;

FIG. 8 is a plan view showing a schematic configuration inside a mouse which is an XY coordinate input device having an optical rotary encoder.

9 is a plan view of a disk-shaped light shielding plate provided in the mouse of FIG. 8 as viewed from a rotation axis direction.

FIG. 10 is a block diagram showing an example of a conventional signal processing circuit for an optical rotary encoder provided in the mouse of FIG.

11 is a signal waveform diagram showing an example of a signal waveform obtained from the processing circuit shown in FIG.

[Explanation of symbols]

5A, 5B, 6A, 6B Light emitting element (light emitting diode) 7A, 7B, 8A, 8B Light receiving element (phototransistor) 21 Current adjusting resistors 21a to 21g Current adjusting resistors 23A, 23B Inverter (logic circuit) 24A, 24B Coupling capacitor 25A, 25B Input resistor 27, 28 Bias voltage setting resistor 30 Current adjusting resistor 31 Trimming resistor 35, 36 Light emitting element (light emitting diode) 37, 38 Light receiving element (package) 37A, 37B, 38A , 38B Phototransistor

Claims (4)

(57) [Claims] 1. A pair of light receiving elements arranged opposite to a light emitting element via a light shielding plate having a number of slits, and a pair of special analog waveform signals obtained from the pair of light receiving elements are respectively shaped into rectangular waveforms. A signal processing circuit for an optical encoder comprising a rectangular wave processing means, wherein the pair of rectangular wave processing means is constituted by a logic circuit comprising a pair of inverters or the like having hysteresis characteristics, and the input of the logic circuit includes the logic circuit. A DC bias voltage set between the two threshold levels is applied, and the outputs of the pair of light receiving elements are respectively AC-coupled and connected to the inputs of the pair of logic circuits, respectively. Signal processing circuit for optical encoder. 2. The light-emitting element is constituted by a light-emitting diode, and a current adjusting resistor is connected in series with the light-emitting diode. The potential of the resistor or the light-emitting diode is used as the DC bias voltage for the pair of light-emitting diodes. 2. The circuit according to claim 1, wherein the voltage is applied to an input of the logic circuit.
A signal processing circuit for an optical encoder as described in the above. 3. The current adjusting resistor comprises a plurality of resistors, and at least one of the plurality of resistors comprises a resistor whose resistance value is adjustable. Item 3. A signal processing circuit for an optical encoder according to Item 2. 4. The encoder signal processing circuit according to claim 1, wherein the logic circuit including the pair of inverters and the like is a circuit housed in the same integrated circuit package.