JPH0318993Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Application This invention relates to an optical input device for inputting information in a device for optically detecting the position of an object.

(b) Prior Art and its Problems Conventionally, the optical input device is generally constructed as shown in FIG. 3. That is, the detection panel 1 formed into a square shape has four walls L ₁ , L ₂ , L ₃ ,
A position detection surface 2 is formed surrounded by L ₄ .
On one wall L1 of this detection panel ₁ , light emitting diodes a are arranged at predetermined intervals (eight in this example), and on a wall _L2 opposite to the wall _L1 , a pair of each light emitting diode a is arranged. eggplant phototransistor b
are arranged. Similarly, wall L ₃ of panel frame 1
There are light emitting diodes a (16 in this example) on the wall.
A phototransistor b is arranged in _L4 .
Thus, on the position detection surface 2, a grid-like optical path (part of which is indicated by the broken line in FIG. 3) is formed by the light emitting diode a and the phototransistor b, which form a pair. .

Although not shown, each light emitting diode a
Predetermined wiring is provided to the phototransistors b, and the specified pairs of light emitting diodes a are turned on one after another, and the light is emitted to the corresponding phototransistor b. Then, by touching a desired position on the position detection surface 2 with a finger or the like, the finger or the like blocks the light passing through the optical path formed between the pair of light emitting diodes and the light receiving element, thereby detecting the light on the input panel. Position detection is being performed.

In order to explain the position detection operation, Fig. 4 shows the third
A partial view of the figure is shown. In FIG. 4, a light emitting diode a and a phototransistor b are designated as a pair, and light is emitted from the light emitting diode a. When the detected object 3 is on the optical path connecting the light emitting diode a and the phototransistor b, the detected object 3 blocks the light P ₁ traveling straight from the light emitting diode a to the phototransistor b, and the light P ₁ passes through the phototransistor b. will not be reached. By the way, out of the light emitted from the light emitting diode a, the detection panel 1
In some cases, the light P ₂ reflected by the inner wall ₄ of the wall L ₄ is received by the phototransistor b. In this case, there was a problem that the position of the object to be detected 3 could not be detected.

The object of this invention is to provide an optical input device in which light reflected from a light source by an inner wall of a detection panel does not reach a pair of light receiving elements.

(C) Means for solving the problem In this invention, an antireflection protrusion having a length of at least d ₁ +d ₂ /4 is provided on the position detection surface side at approximately the center of the inner wall of the detection panel. However, d ₁ is the width of the light source, and d ₂ is the width of the light receiving element.

(d) Effect The light reflected from the light source by the inner wall of the detection panel and directed towards the light receiving element paired with the light source is always blocked by the anti-reflection protrusion and never reaches the light receiving element. do not have.

(E) Embodiment FIG. 1 shows an embodiment of this invention, in which each inner wall 1 _to 4 of the walls L ₁ to _{L 4} of the detection panel 1 has a wall _d extending toward the center of the detection surface 2. Antireflection protrusions H ₁ , H ₂ , H ₃ , and H ₄ having a length of ₁ + d ₂ /4 are provided. Here, d ₁ is the width of the light-emitting diode a, especially the width of the light-receiving surface, and d ₂ is the width of the phototransistor b, especially the width of the light-receiving surface. Each of the above projections
The widths of H ₁ , H ₂ , H ₃ , and H ₄ are made thin enough so that the grid-like optical path formed by each pair of light emitting diode a and phototransistor b is not blocked. There is.

FIG. 2 shows an explanatory diagram for determining the length of the protrusion. In Figure 2, detection panel 1
The distance from the inner wall ₄ to the center of the pair of light emitting diodes a is h. h is also the distance from the inner wall ₄ to the center of phototransistor b. Consider the optical path through which light emitted from light emitting diode a is reflected by inner wall ₄ and received by phototransistor b. This light path
The light from the light emitting diode at a distance of (h-d ₁ / ₂ ) from the inner wall ₄ is reflected at the _Q1 point on the inner wall 4, and the light from the inner wall ₄ is (h+
The light path S ₁ is received by the phototransistor b at a distance of d ₂ /2), and the light from the light emitting diode at a distance of (h + d ₁ /2) from the inner wall ₄ is reflected at _two points Q on the inner wall ₄ and reflected from the inner wall ₄ . This is the optical path between the optical path S2 and the optical path _S2 , which is received by the phototransistor b at a distance of (h- _d2 /2). Here, the center position of the inner wall ₄ is O,
Let the distance of inner wall ₄ be 2w. Then, the inner wall ₄ was set as the X axis, and the axis passing through O and perpendicular to the X axis was set as the Y axis.
Consider the XY plane. At this time, the coordinates of the start and end points of each optical path _{S 1 and S 2 are} known, and the inclination of the optical path on the By solving, we obtain OQ ₁ = x ₁ = w (d ₁ + d ₂ )/4h + d ₂ - _{d 1} , OQ ₂ = x ₂ = w (d ₁ + d ₂ )/4h + d ₁ - d ₂ , and further optical path S ₁ Letting the intersection point of and S ₂ be Q ₃ , OQ ₃ =y=d ₁ +d ₂ /4 is obtained, proving that the intersection point Q ₃ is a point on the y-axis. As is clear from Figure 2, the inner wall ₄
The light from the light-emitting diode a that should be reflected by the phototransistor b and received by the phototransistor b must pass through a plane perpendicular to the position detection surface 2 side and at a distance of d ₁ + d ₂ /4 from the center position O of the inner wall ₄ . Become. Therefore, by providing the protrusions H ₁ to H ₄ on each of the inner walls ₁ to ₄ , the phototransistor b of the reflected light from each inner wall can be
The incident light is completely blocked by the protrusion.

As a special case, when the width d ₁ of the light emitting diode a and the width d ₂ of the phototransistor b are equal, y=d ₁ /2=d ₂ /2, x ₁ =x ₂ .

In addition, if it is known that the intersection of optical paths S ₁ and S ₂ is on a plane perpendicular to the center position O of the inner wall ₄ , y/x ₁ = h−d ₁ due to the mechanical similarity relationship. Since /2/w−x ₁ =h+d ₂ /2/w+x ₁ holds true, this equation can be solved to obtain y=d ₁ +d ₂ /4.

(f) Effect This device is designed to prevent light from being reflected by the inner wall of the detection panel and entering the light-receiving element paired with the light source. Since the light is blocked by the light receiving element, the light does not enter the light receiving element. Therefore, the presence or absence of an object and its position can be accurately measured.
Erroneous detection can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of this invention;
FIG. 2 is an explanatory diagram of the principle of this invention, FIG. 3 is a plan view of a conventional optical input device, and FIG. 4 is an explanatory diagram of problems with the device of FIG. 3. 1...Detection panel, 2...Position detection surface 3...Detected object, a...Light emitting diode, b...Phototransistor, _L1 , _L2 , _L3 , _L4 ...Wall, ₁ , ₂ ,
₃ , ₄ ...Inner wall, _H1 , _H2 , _H3 , _H4 ...Protrusion.

Claims (1)

[Claims for Utility Model Registration] A detection panel having a position detection surface, and a pair of light receiving elements and a light source arranged oppositely with the position detection surface in between, wherein light from the light source is transmitted to the detection panel. In the optical input device that is reflected by the inner wall of the detection panel and enters the light receiving element, at least d ₁ +d ₂ /4 (d ₁ is the width of the light source) on the position detection surface side approximately in the center of the inner wall of the detection panel. , d ₂ is the width of the light-receiving element).