GB2154734A - Electro-optical mouse - Google Patents

Abstract

An electro-optical omni-directional mouse system for controlling the movement of a cursor comprises a mouse 1 movable over a planar surface 3 without regard to the mouse's angular orientation with respect to the pattern on the surface, which includes reflective areas separated by non- reflective portions (eg, areas separated by line segments). A source 7 is rigidly fixed to the mouse housing 5 to emit light that impinges on the surface. Four photodectors 15 are rigidly fixed to the housing to receive the subsequently reflected light and output signals in response thereto as the mouse moves over the planar surface. Amplifiers and comparators transform this output into binary code, from which a microcomputer decodes the binary pattern into distance and direction data, and then processes these data to form position signals for controlling the cursor. The detected surface is optically imaged onto the photodetectors so that the width of a line segment is magnified to correspond to the size of each detector. <IMAGE>

Description

SPECIFICATION Electro-optical mouse TECHNICAL FIELD The present invention relates to the field of controlling the movement of a cursor on a cathode ray tube. In particular, it relates to such control through the use of an optical transducer to convert translational movement of that transducer over a surface to corresponding X and Y axis signals.

BACKGROUND OF THE INVENTION As less highly trained and technically competent persons use computers it has become more desirable to simplify their operation and make the computer "user friendly." One successful technique has been to provide the user choices on a cathode ray tube ("CRT") and to have the user manipulate a cursor to select one of the choices: Of the known techniques one of the most popular is cursor control through a "mouse". The cursor is a dot or line on the CRT which the user can move. A "mouse" is a small box or housing which the user can freely move over a horizontal surface, such as a desk. The cursor generally follows the movements of the mouse.

That is, if the mouse is moved horizontally, the cursor moves horizontally.

Early mice were mechanical. Illustrative of this type of mouse is that shown in Hawley, U.S.

Patent No. 3,892,963. The movable housing carries two position wheels which rotate about axes which are perpendicular.

One wheel has its axis aligned with the longitudinal axis of the housing and the other wheel has its axis aligned along the transverse axis of the housing. Each axis is connected to an optical encoder, which sends signals to the computer to control cursor movement on one axis of the CRT. The cursor translates on the CRT along a vector which forms an angle to the vertical-up direction on the CRT equal to the angle between the vector that is aligned with the motion of the mouse and the vector aligned with the longitudinal-forward axis of the mouse. Thus, the cursor follows the movement that the mouse makes with respect to itself and is independent of the orientation of the mouse with respect to the surface upon which it translates. Other mechanical mice are taught by Engelbart, U.S. Patent No. 3,541,541; Koster, U.S. Patent No.

3,541,521;-and Page, U.S. Patent No. 4,303,914.

These mechanical mice are of course limited by various mechanical constraints. For example, satisfactory frictional contact has to exist between the horizontal surface and the position wheels.

Furthermore, manufacturing processes are relatively expensive because of the required mechanical tolerances. Also mechanical mice are subject to mechanical wear and can be easily damaged by dropping.

Meyer, U.S. Patent No. 3,297,879, disclose one encoder that overcomes many of these disadvantages. In one embodiment of Meyer a stationary grid, comprising mutually orthogonal sets of parallel nonreflective bands, is formed on a reflective surface. A light source and four photocells are incorporated into a movable reading head. The light source illuminates the grid and the photocells detect reflected light from the grid. A plate having four sets of transmissive slits two of which are aligned with each set of parallel, non-reflective bands, is positioned in front of the photocells, each photocell being associated with one set of slits. The slits in each of the two sets of slits associated with each set of bands are aligned out of phase.During movement of the reading head the amount of light reflected by the reflective space between the nonreflective bands and received by each photocell via the intervening slits oscillates between dark and light, causing each photocell to output a pulsating signal. The number of pulsations depends upon the number of bands which have been crossed and thus is indicative of the distance traveled. Moreover, since the slits are out of phase, the movement of the reading head in one direction will cause the output of one of the two correspondingly aligned photocells to change first and movement in the opposite direction will cause the other photocell to change first. Thus, the encoder is direction sensitive. Meyer also produces two signals, each representing one orthogonal direction.However, because Meyer's housing must maintain a given angular relation with the surface, the housing in Meyer must be physically constrained. Accordingly, Meyer mounts his housing on a four-bar parallel linkage or on an X-Y set of orthogonal parallel guides. Furthermore, Meyer has the disadvantage of requiring both a surface and a screen having optically readable markings.

U.S. Patent No. 4,390,873 to Kirsch ("Kirsch I") shows an attempt to emulate optically the prior art mechanical mice. Kirsch I comprises a mouse having a light source and a four-quadrant photodetector, a surface having an optically contrasting checkerboard pattern having various assigned position states over which the mouse housing translates, and a logic circuit having a read only memory. Each of the squares in the checkerboard pattern defines a position state in two directions at the same location. As the housing translates over the surface the logic interprets the output from all of the four detectors, refers to the read only memory to determine the position state at which the housing is located, and produces an output signal to represent the housing's position in relation to the surface.

Although the Kirsch I mouse is not physically restrained, it suffers from many of the same disadvantages which attend other prior art optical mouses. Because of its surface pattern and the assignment of position states to indicia thereon, the Kirsch I mouse is limited to determining movement in only two directions, and then only with respect to the surface, i.e., the cursor moves with respect to the surface indicia. For example, if the longitudinal axis of the housing is at an angle with respect to the lines defining the checkerboard pattern, and the housing is moved parallel to those lines, the cursor will move horizontally (or vertically).

Thus, unlike the prior art mechanical mice, the Kirsch I mouse is sensitive to its orientation with respect to the surface pattern. A rotation of the mouse of greater than 45 in either direction from the nominal pattern orientation affects the decoded signal. Furthermore, the Kirsch I mouse requires encoding of the output of its quadrature detector in order for a conventional computer to utilize its output.

Another optical mouse is shown in U.S. Patent No. 4,364,035 to Kirsch (Kirsch II). It discloses a read head employing a movable detector which slides over a surface having two parallel sets of perpendicular lines, each set being of a different color. The detector includes a light source which emits light of each color in an alternating sequence. Four light detectors are positioned for receiving light reflected from the surface. By clocking the emission of the respectively colored light and the detector output signal, electrical outputs are obtained representing reflection from the respective sets of colored lines. Such signals are used to establish line crossings, thereby deriving a position signal for the cursor.

The Kirsch II mouse also has the disadvantage that the output is indicative of mouse housing movement with respect to the surface pattern. Thus, it too is sensitive to surface orientation.

Furthermore, the use of two colors results in a mouse system that is more complicated than is the case in a "single color" system. Differently colored marks must be applied to the surface, two light sources must be incorporated in the system, and clocking means must be provided for activating the respective light sources in alternating sequence in accordance with the decoding technique. Also, since an acceptable two-color grid requires the use of precisely controlled amounts of exotic inks, the manufacture of the grid becomes a difficult and expensive process.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an optical mouse.

It is a further object of the present invention to provide such a mouse that employs a single light source.

It is a further object of the present invention to provide such a mouse in which the mouse output is relative to mouse movement only and independent of the relative orientation of the surface upon which the mouse translates.

It is another object to provide such a mouse which can determine movement in all directions regardless of its orientation with respect to the surface pattern over which it translates.

It is another object to provide such a mouse having a reflective surface on which a pattern can be applied using ordinary inks or pigments.

It is a further object of the present invention to provide a mouse that does not utilize a quadrature decoding technique.

It is a further object of the present invention to provide such a mouse that can determine the direction of its movement with respect to itself and independent of its orientation to the pattern over which it translates.

It is a further object of the present invention to provide such a mouse that has redundant direction and movement information through use of non-quadrature decoding.

It is a further object of the present invention to provide a means for controlling the position of a cursor which is inexpensive to manufacture, easy to operate, and mechanically rugged.

Also, it is an object of the present invention to provide a means for controlling the position of a cursor which does not have a slit plate interposed between the photosensitive means and the grid.

In the present invention a light source emits light, which is reflected from a reflective surface onto four photodetectors arranged in a square pattern. The light source and photodetectors are rigidly fixed inside the housing, which is movable over the reflective surface. The pattern on the reflective surface may be a grid of orthogonal or hexagonal lines or curvilinear segments (or a matrix of squares, hexagons, or circles, respectively). This pattern is optically imaged onto the four photodetectors such that the width of a line segment is optically magnified to correspond to the distance between centers of adjacent photodetectors. During movement of the housing, the magnified image of the illuminated pattern moves across the four detectors. As a result of this movement, the photodetectors sense changes in light intensity and generate electrical signals representing crossings of lines and spaces.

The electrical signals output by the photodetectors are input into four amplifiers. The output of each amplifier is "low" when light is reflected onto the corresponding photodector. The output of each amplifier is "high" when little or no light is reflected. The output of each amplifier is intput to a corresponding comparator, which switches when the amplifier output voltage crosses a predetermined threshold. The outputs of the comparators are input to a microcomputer.

The electrical signals generated by the photodetectors are translated into direction information by relating the sequence of changes in the signals to the relative position of the photodetectors in the housing. Distance information is obtained by counting signal changes as a function of direction.

The four photodetectors, which are rigidly fixed inside the mouse housing in a square pattern, are aligned orthogonally with respect to the housing. Thus, movement of the housing in a horizontal direction can be detected by noting the sequence of signal changes in either the upper or lower two photodetectors. The width of a pattern line as imaged on the photodetectors cannot cover all photodetectors simultaneously, thus if one pair (e.g. the upper two elements) is covered by a horizontal line segment, the other pair (e.g. the lower two elements) can be used to sense horizontal movement. Similarly, vertical movement can be translated from the sequence of signal changes in either the two right-side or two left-side elements.This method of translating changes in the imaged pattern into X-Y distance and direction data as related to the movement of the detector which is rigidly fastened to the housing can be seen to be unaffected by the orientation of the housing on the pattern.

The X-Y distance and direction information is output to drive a cursor, the position of which is changed in response to the output information.

BRIEF DESCRIPTION OF THE DRAWINGS The optical mouse of the present invention will be described in detail with reference to the following drawings: Figure 1 is a side cross-sectional view of one embodiment of the electro-optical mouse of the present invention.

Figure 2 is a plan view of a four-photodetector array for use in the mouse of Fig. 1.

Figures 3a and b are plan views of portions of possible grid patterns of the present invention, indicating the position of the area observed by the photodetector array of Fig. 2 in relation to the grid pattern.

Figure 4 is a diagram of the circuitry used in the mouse system of the present invention.

Figure 5 is a diagrammatic view of the detector output pattern for the A and B quadrants of the photodetector array when the area observed by the photodetector array moves in either direction along row I or row II of Fig. 3a.

Figure 6 is a side cross-sectional view of another embodiment of the optical mouse of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 shows the preferred embodiment of the position control system 1, which is movable over surface 3. The system 1 comprises a housing 5, a light source 7 and a detecting means 9.

The light source 7 is powered through conductors 11 and 1 3. Detecting means 9 includes photodetector array 15, which receives light reflected from surface 3 and transmitted through imaging lens 1 7. Conductors 1 9 feed the signal from array 1 5. Light source 7 and detecting means 9 are each rigidly fixed relative to housing 5 by fastening means affixed to internal shelves 21 and 23.

Housing 5 is provided with low-friction spacers 25 and 27 which elevate the body of the housing, including lens 1 7 and detecting means 9, above surface 3 by the distance required to satisfy the optical magnification required. Spacers 25 and 27 may be made of a material that will minimize wear of surface 3 and enable the housing 5 to slide easily over that surface.

In the illustrated embodiment source 7 is a light-emitting diode (LED). Light source 7 emits light that lies preferably in either the red or the infrared portions of the spectrum. Light shield 29 prevents light source 7 from illuminating detecting means 9 directly. Ideally, source 7 is mounted so that it is positioned close to surface 3. This will ensure that light emitted by source 7 will impinge on surface 3 at a relatively narrow spot with a higher light intensity than if positioned further away.

As can be seen in Fig. 2, photodetector array 1 5 comprises four photodetectors, hereafter referred to as detectors A through D inclusive. Photodetector array 1 5 may be a standard fourquadrant photodetector. Each detector responds independently when radiant energy impinges on its surface area by producing an electrical current proportional to the intensity of the radiant energy.

Fig. 3 shows two possible embodiments of the optically contrasting areas of surface 3. These optically contrasting areas can be applied through conventional printing techniques. Both areas 33 and nonreflective line segments 31 can be made of ordinary materials but of contrasting colors. For example, white or light-colored paper having black line segments printed thereon is suitable. Alternatively, a sheet of transparent photographic film with black line segments spaced thereon can be placed on a reflective surface.

In Fig. 3a the non-reflective line segments 31 applied to the reflective surface define reflective square areas 33. In an alternative embodiment (not illustrated) an array of non-reflective areas (corresponding in position and size to areas 33) is applied to a reflective surface. In this case the non-reflective areas applied to the reflective surface define a reflective grid of line segments (corresponding in position and size to line segments 31). In both embodiments each line segment has a width equal to one arbitrary unit and each square area has sides with a length equal to two arbitrary units.

In the embodiment of Fig. 3b line segments 31 define hexagonal areas 33. As will be evident to one skilled in the art, many repetitive patterns are suitable and the two illustrated in Fig. 3 are merely illustrative. Indeed, line segments 31 may be circular and areas 33 could be nonreflective discs.

When light is emitted by source 7 and reflected by surface 3, the optically contrasting pattern of segments 31 and areas 33 is optically imaged onto the detectors A through D of the photodetector array 1 5. The imaging lens 1 7 magnifies the image of the surface so that the width of a segment 31 is magnified to approximately equal the distance between centers of segments detector when the image impinges on the detector array 1 5. For example, if segments 31 have a width of 0.01 inch and detector spacing is 0.05 inch, then a magnification of 5X would be required.

The portion of surface 3 which is imaged onto the four detectors of photodetector array 1 5 is depicted in Fig. 3a for twelve different positions of housing 5. The imaging of surface 3 onto the photodetectors is depicted by superimposing detectors A through D onto the imaged surface position. As can be seen, one arbitrary unit of surface area is imaged onto one detector.

As one example, rows I, II, and Ill of Fig. 3a each depict translation of housing 5 from left to right at four stages. Columns I', II', and Ill' each depict translation of housing 5 from top to bottom at three stages. Althqugh each position is separated from adjacent positions by a distance of four arbitrary units in Fig. 3a, the following discussion will treat the adjacent positions as if they denoted successive translational steps of one arbitrary unit.

Fig. 4 shows the circuitry for the preferred embodiment of the present invention. Resistors 41, 43 and 45 are connected in series across the terminals of a power supply 46. The common cathode 47 of photodetector array 1 5 is connected at a junction located between resistors 41 and 43.

Anodes of detectors A through D, respectively, are each electrically connected to the negative input port of the corresponding one of amplifiers 57, 59, 61, and 63. These amplifiers may be in the form of a quad amplifier, for example, quad amplifier TL064. Each amplifier has two input ports and an output port. The output port of each amplifier is electrically connected to the negative input port of the same amplifier by way of resistors 65, 67, 69, and 71, respectively.

The positive input ports of amplifiers 57, 59, 61, and 63 are electrically connected in common to junction 73, which is connected to common cathode 47. The reference voltage supplied to the second positive input port of each amplifier and to the photodetector common cathode is equal to a first predetermined value.

The output port of each amplifier is in turn electrically connected to the positive input port of the corresponding one of comparators 75, 77, 79, and 81. The negative input ports of comparators 75, 77, 79, and 81 are electrically connected in common to junction 83, which is located between resistors 43 and 45. The theshold voltage supplied to the negative input port of each comparator is equal to a second predetermined value. One skilled in art would recognize that a high-gain comparator could be substituted for each amplifier 57, 59, 61 and 63 and comparator 75, 77, 79 and 91.

The output port of each comparator is in turn electrically connected to an input port of microcomputer 85. Also connected to microcomputer 85 are switches 87, 89 and 91. Capacitor 93 and resistor 95 are series-connected across the supply voltage. This circuit is electrically connected to the reset input port of microcomputer 85 at junction 97, which lies between capacitor 93 and resistor 95. The host (now shown) is connected to microcomputer 85 by way of inverter 99 and by way of inverter 101. Clock 103, connected to microcomputer 85, provides a clock signal.

Microcomputer 85 is electrically connected to light source 7 by way of inverter 105 and resistor 107 connected in series. Finally, microcomputer 85 is electrically connected to a power supply 109 and power supply decoupling means 111.

OPERATION During operation, housing 5 is gripped by the operator's hand and moved in any direction by sliding over the surface 3. Source 7 is positioned so that the emitted light impinges on surface 3. The light is then reflected if it impinges on reflective areas 33 or is absorbed if it impinges on non-reflective segments 31. Detecting means 9 is positioned so that light emitted by source 7 and reflected by areas 33 is then detected by photodetector array 1 5.

Each detector of array 1 5 detects light independently, outputting a signal in response to light impinging on its surface. Detector A outputs a signal to amplifier 57, detector B to amplifier 59, detector C to amplifier 63, and detector D to amplifier 61. Each amplifier produces an output voltage which goes negative with increasing input signal with respect to the reference voltage.

Thus, when light is reflected onto a photodetector, the output of the corresponding amplifier is "low". When that detector no longer detects light (i.e., "sees" a non-reflective segment on surface 3), the output of the corresponding amplifier goes "high".

The outputs of amplifiers 57, 59, 61, and 63 are fed to the comparators 75, 77, 79, and 81, respectively. Each comparator switches when the output voltage of the corresponding amplifier crosses the threshold voltage. The output ports of the comparators 75, 77, 79, 81 are connected to the microcomputer 85, which reads the output pattern at a regular rate.

The binary output read by microcomputer 85 for each of the positions shown in Fig. 3a is as follows: ROW I RCti II RCW III A ABCD ABCD 1010 1011 1110 0000 0011 1100 0101 0111 1101 1010 1011 1110 Column I Column II Column III ABCD ABCD ABCD 1010 0000 0101 loll 0011 0111 1110 1100 1101 The coded outputs are fed from comparators 75, 77, 79, 81 to microcomputer 85. Microcomputer 85 translates the output generated by detectors A and B (or C and D) into horizontal movement data and the outputs generated by detectors A and C (or B and D) into vertical movement data. By reading the coded output pattern, microcomputer 85 determines the distance and direction of mouse travel.

Fig. 5 shows the AB output pattern for mouse motion from left to right and from right to left along either row I or row II of Fig. 3a. For motion from left to right, the sequence of AB states is as follows: 10 00 01 10 00 01 for motion from right to left, the sequence of AB states is as follows: 100100100100.

When microcomputer 85 processes the coded output pattern for the A and B detectors, it determines the direction of travel for each instance in which a digit of the binary pattern has changed. Depending on the direction of travel of the mouse as determined by microcomputer 85, the horizontal movement of the cursor is controlled correspondingly. The cursor moves right or left one corresponding unit for each arbitrary unit traveled by the mouse in response to commands from microcompter 85. Microcomputer 85 controls the vertical movement of the cursor by processing the AC (or BD) output pattern in a similar way.

It will be noted, however, that the AB output pattern for mouse motion along row Ill does not vary. The sequence of AB states is as follows: 11111111..

Similarly, the AC output pattern for mouse motion along column I' does not vary, the BD output pattern for mouse motion along column Ill' does not vary, and the CD output pattern for mouse motion along row II does not vary. It is an important feature of the present invention that microcomputer 85 ignores the 11 state whenever it occurs. For example, if the AB output is 11, then microcomputer 85 automatically switches to translate the CD output. Microcomputer 85 contines to translate the received CD output until the CD output becomes 11, at which point microcomputer 85 switches to translate the AB output. In this manner, microcomputer 85 alternatingly translates either the AB or the CD output to continuously obtain horizontal position signals for controlling the cursor.Microcomputer 85 similarly switches back and forth between the AC and BD outputs to continuously obtain vertical position signals.

One skilled in the art will recognize that the output of detectors A through D is independent of the orientation of surface 3. That is, the change in state of detectors A through D depends only on the movement of the mouse with respect to itself. That is, in the mouse of the present invention, horizontal movement of the mouse results in horizontal cursor movement regardless of the angular orientation of the mouse relative to the grid position. Thus, rotation of the mouse has no significant affect on its output and, unlike many prior art mice, is not limited to providing information in only two directions (i.e., those defined by the surface grid pattern or the physical mechanisms constraining the mouse).

The microcomputer 85 is reset by means of the circuit comprising capacitor 93 and resistor 95. In addition to outputting commands to the host via inverter 101, microcomputer 85 receives information from the host via inverter 99. Power is supplied by a power supply 1 09.

Source 7 is controlled by commands output by microcomputer 85.

In accordance with the above-described embodiment, the position of a cursor can be controlled by the movement of a hand-held mouse. It is to be understood that the above description of the preferred embodiment is presented for illustrative purposes only and is not intended to limit the scope of the present invention as claimed in the appended claims.

Modifications and variations may be effected without departing from the scope of the inventive concept herein disclosed. For example, the optically contrasting surfaces and light sources may be replaced by a surface having magnetic indicia, and the detecting means may be replaced by a magnetic read transducer. In addition, it is obvious to one skilled in the art that the reflective surface could be replaced by a transmissive surface such as that depicted in part in Fig. 6. Such an embodiment would require that the light source 7 and the light-detecting means 9 be positioned on opposite sides of a transmissive surface 3'. Source 7 and the detecting means 9 are both movable and are coupled so that movement is in tandem. Suitable coupling means (not shown in Fig. 6) would be a pair of oppositing annular magnets, one magnet rigidly fixed to the source 7 and the other magnet rigidly fixed to the detecting means 9.

Thus, one skilled in the art can create various modifications without departing from the scope of this invention as defined by the following claims.

Claims (33)

1. A position control system for a cursor or the like comprising: (a) a surface having a first set of parallel line segments, the width of each of said first set of line segments being substantially different than the distance separating adjacent ones of said first set of line segments, said first set of line segments forming a first surface portion and the areas not occupied by line segments forming a second surface portion, one of said first and second surface portions being reflective and the other of said surface portions being nonreflective; (b) a housing means movable over said surface; (c) a light-emitting means rigidly fixed to said housing means and directed at said surface; and (d) a light-detecting means rigidly fixed to said housing means and positioned for receiving light emitted by said light-emitting means after reflection by said reflective surface portion, said light-detecting means producing electrical output signals in response to reception of said emitted and then reflected light.

2. A position control system as in claim 1, further comprising a coding means connected to receive said electrical output signals for transforming said electrical output signals into binary code signals, and a decoding means connected to receive said binary code signals for transforming said binary code signals into data corresponding to the distance and direction traveled by said housing means along an axis lying in a first direction relative to said first set of line segments, and connected to output position signals corresponding to said data for controlling the position of a cursor or the like.

3. A position control system as in claim 1, wherein said light-detecting means comprises first and second photosensitive surfaces, said first and second photosensitive surfaces receiving light from adjacent areas on said surface.

4. A position control system as in claim 3, wherein said surface further has a second set of parallel line segments, said second set of line segments intersecting said first set of line segments, the width of each of said second set of line segments being substantially different than the distance separating adjacent ones of said second set of line segments, said second set of line segments forming part of said first surface portion.

5. A position control system as in claim 4, wherein said second set of line segments lies substantially perpendicular to said first set of line segments.

6. A position control system as in claim 4, wherein said light-detecting means further comprises third and fourth photosensitive surfaces, said third and fourth photosensitive surfaces receiving light from areas on said surface adjacent to each other and to said respective areas from which said first and second photosensitive surfaces received light.

7. A position control system as in claim 6, wherein each of said segments has a predetermined width and each of said spaces defines an area having a distance from side to opposite side substantially equal to twice said predetermined width.

8. A position control system as in claim 6, further comprising a coding means connected to receive said electrical output signals for transforming said electrical output signals into binary code signals, and a decoding means connected to receive said binary code signals for transmitting said binary code signals into data corresponding to the distance and direction of travel of said housing means, and connected to output position signals corresponding to said data for controlling a cursor or the like.

9. A position control system as in claim 8, wherein said light-emitting means comprises a light-emitting diode.

1 0. A position control system as in claim 8, wherein said coding means comprises first through fourth amplifiers and first through fourth comparators, each of said amplifiers and comparators having first and second input ports and an output port, the output port of each of said amplifiers being connected to said first input port of the corresponding one of said comparators.

11. A position control system as in claim 10, wherein said decoding means comprises a microcomputer having first through fourth input ports, the output port of each of said comparators being connected to the corresponding one of said first through fourth input ports of said microcomputer for outputting paired sets of binary code signals to said microcomputer.

1 2. A position control system as in claim 11, wherein said first through fourth photosensitive surfaces are integrally formed as four photodectors, each of said photodectors having an output port connected to said first input port of the corresponding one of said amplifiers.

1 3. A position control system as in claim 11, wherein said second input ports of said amplifiers are connected in common to a predetermined reference voltage, and said second input ports of said comparators are connected in common to a predetermined threshold voltage.

1 4. A position control system as in claim 11, wherein said light-emitting means comprises a light-emitting diode, said microcomputer being operatively connected to said light-emitting diode for controlling the emission of light by said light-emitting diode.

1 5. A position control system as in claim 8, wherein said coding means comprises first through fourth output ports, and said decoding means translate the paired sets of binary code signals output at said first and second output ports and at said third and fourth output ports alternatingly into data corresponding to the distance and direction traveled by said housing means along a first direction.

16. A position control system as in claim 15, wherein said decoding means translates the paired sets of binary code signals output at said first and third output ports and at said second and fourth output ports alternatingly into data corresponding to the distance and direction traveled by said housing means along a second direction substantially perpendicular to said first direction.

1 7. A position control system as in claim 16, wherein said decoding means comprises recognition means and a switching means, said switching means causing said decoding means to translate the paired set of binary code signals output at two of said output ports of said coding means in response to said recognition means recognizing a predetermined noninformative paired set of signals output at the other two of said output ports of said coding means.

1 8. A position control system as in claim 1, wherein said microcomputer comprises recognition means and switching means, said switching means causing said microcomputer to translate the paired set of signals output by one pair of said comparators when said recongition means recognizes a predetermined non-informative paired set of signals output by the other pair of said comparators.

1 9. A position control system as in claim 12, further comprising optical means positioned between said surface and said photodetectors for magnifying the light reflected by a unit area of said reflective surface portion, said unit area being an area such that said light reflected by said unit area and magnified by said optical means has a cross section substantially corresponding in size to the distance between the centers of said photodectors when said reflected and then magnified light impinges on said photodector.

20. A position control system for a cursor or the like comprising: (a) a surface having a first set of parallel line segments, the width of each of said first set of line segments being substantially different than the distance separating adjacent ones of said first set of line segments, said first set of line segments forming a first surface portion and areas not occupied by line segments forming a second surface portion, said first surface portion having a first effect on light and said second surface portion having a second effect on light; (b) a movable light-emitting means directed at said surface; and (c) a movable light-detecting means, coupled to said light-emitting means for movement in tandem and positioned for receiving light emitted by said light-emitting means which impinges on one of said surface portions, and producing electrical output signals in response to said received light.

21. A position control system as in claim 20, wherein said surface further has a second set of parallel line segments, said second set of line segments intersecting said first set of line segments, the width of each of said second set of line segments being substantially different than the distance separating adjacent ones of said second set of line segments, said second set of line segments forming part of said first surface portion.

22. A position control system as in claim 21 wherein said first and second sets of line segments are mutually orthogonal lines.

23. A position control system for a cursor or the like comprising: (a) a surface having a first set of parallel line segments, the width of each of said first set of line segments being substantially different than the distance separating adjacent ones of said first set of line segments, said first set of line segments forming a first surface portion and the spaces not occupied by line segments forming a second surface portion, said first surface portion having a first effect on light and said second surface portion having a second effect on light, and (b) transducer means movable over said surface for producing a first electrical output when scanning said first surface portion and a second electrical output when scanning said second surface portion.

24. A position control system as in claim 23, wherein said transducer means comprises first and second transducers scanning adjacent areas on said surface, each of said transducers producing said first or said second electrical output.

25. A position control system as in claim 24, wherein said surface further has a second set of parallel line segments and a third set of parallel line segments, said second and third sets of line segments being connected to said first set of line segments, the width of each of said second and third sets of line segments being sustantially different than the distance separating adjacent ones of said second and third sets of line segments, respectively, said second and third sets of line segments forming part of said first surface portion, and said first, second and third sets of line segments enclosing areas comprising said second surface portion.

26. A position control system as in claim 25, wherein said transducer means further comprises third and fourth transducers, said third and fourth transducers scanning areas on said surface adjacent to each other and adjacent to said respective areas scanned by said first and second transducers, each of said third and fourth transducers producing said first or said second electrical output.

27. A position control system for a cursor or the like comprising: (a) a surface having curvilinear segments connected to enclose and define an array of areas, said curvilinear segments forming a first surface portion and said enclosed areas forming a second surface portion, said first surface portions having a first effect on light and said second surface portion having a second effect on light; and (b) transducer means movable over said surface for producing a first electrical output signal when scanning said first surface portion and a second electrical output signal when scanning said second surface portion.

28. A position control system for a cursor or the like as in claim 27 wherein said enclosed spaces are squares.

29. A position control system for a cursor or the like as in claim 27 wherein said enclosed spaces are hexagons.

30. A position control system for a cursor or the like as in claim 27 wherein said enclosed spaces are circles.

31. A position control system for a cursor or the like as in claim 27, further comprising a coding means connected to receive said electrical output signals for transforming said electrical output signals into binary code signals, and a decoding means connected to receive said binary code signals for transforming said binary code signals into data corresponding to the distance and direction traveled by said transducer means and connected to output position signals corresponding to said data for controlling the position of a cursor or the like.

32. A position control system for a cursor or the like as in claim 31, wherein said coding means comprises first though fourth output ports, and said decoding means translates the paired sets of binary code signals output at two of said output ports and at the other two of said output ports alternatingly into data corresponding to the distance and direction traveled by said transducer means along a first direction.

33. A position control system for a cursor or the like as in claim 32, wherein said decoding means comprises recognition means and switching means, said switching means causing said decoding means to translate the paired set of binary code signals output at two of said output ports in response to said recognition means recognizing a predetermined non-informative paired set of binary code signals output at the other two of said output ports.