JP2002163963A - Optical type touch switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superior detecting circuit having a large S/N ratio and a superior detecting sensitivity while an outgoing beam emitted from a light emitting element will make the total internal reflection in case a finger does not contact with a touch face. SOLUTION: In an optical type touch switch using the light emitting element and a light receiving element, the outgoing beam emitted from a light emitting element enters into a light guide body, and the incident light is reflected by the touch face installed at the light guide body, and the reflected light is led to the light receiving element, and when a finger does not contact with the touch face, almost all of the incident light led to the light guide body enters from the light emitting element is made to have the total internal reflection at the touch face and to enter into the light receiving element, and when the finger contacts with the touch face, a part of the light transmits through the finger, and by utilizing the fact that the incident light to enter into the light receiving element greatly decreases as the other light has irregular reflections by the finger, a contact of the finger is made to be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to, for example, home appliances,
More particularly, the present invention relates to an optical touch switch provided in a vending machine, an in-vehicle device, and the like.

[0002]

2. Description of the Related Art This type of optical touch switch is used for home appliances,
It is provided in vending machines, in-vehicle devices, and the like, and is used to input control information for controlling these devices.
An example of such a switch will be described with reference to FIGS.

FIG. 6 is a cross-sectional view of an essential part of an optical touch switch. Reference numeral 1 denotes a light-emitting element which emits visible light or infrared light, and an infrared light-emitting element is generally used. Reference numeral 2 denotes a light receiving element, which reflects light emitted from the light emitting element with a finger and receives the reflected light. Reference numeral 3 denotes a printed circuit board for mounting the light emitting element and the light receiving element. Although not shown in the drawing, the printed circuit board receives a drive circuit for driving the light emitting element and the output of the light receiving element in addition to these components. Electronic components forming a detection circuit and the like for detecting contact of a finger are mounted.

A panel 4 is made of a material through which light emitted from the light emitting element can pass. And
When the finger F contacts the panel surface in the upward direction of the light emitting element, the contact is detected. Reference numeral 5a denotes outgoing light emitted from the light emitting element, and 5e denotes reflected light obtained by reflecting the outgoing light with a finger.
The reflected light is incident on the light receiving element 2, and the detection circuit including the light receiving element detects the contact of the finger with the panel.

In this switch, the light emitted from the light emitting element is reflected by the finger F, and the reflected light is received by the light receiving element. Therefore, the switch can detect even in an approaching state other than the contact of the finger with the panel. The light receiving level of the light receiving element is small when the finger F is far from the panel, becomes large when the finger F is close to the panel, and becomes maximum when the finger F comes into contact with the panel. Therefore, this switch can detect from the approach of the finger to the panel to the touch, and various uses have been proposed, but they are omitted here.
In many cases, the switch is used as a single switch rather than as a keyboard in which a plurality of switches are mounted at one place.

A plurality of optical touch switches are assembled,
FIG. 7 shows an example of a switch effective for such a switch, which is sometimes used as a keyboard. In FIG. 7, 6 is a light guide plate, 7a to 7d are light emitting elements, and 2 is a light receiving element for receiving light emitted from the light emitting element. And
This light receiving element is provided commonly to the four light emitting elements. These light emitting element and light receiving element are the same as the light emitting element and light receiving element described in FIG. Reference numeral 3 denotes a printed board on which the device is mounted, and F denotes a finger.

FIG. 7 shows a keyboard composed of four switches, and a switch A includes a light emitting element 7a and a light receiving element 2a.
, A switch B is a detection circuit including the light emitting element 7b and the light receiving element 2, and a switch C is a detection circuit including the light emitting element 7c and the light receiving element 2. Configured and switch D
Is composed of a detection circuit including the light emitting element 7d and the light receiving element 2.

The four light-emitting elements emit pulses in order, and when no finger touches the light guide plate surface, light emitted from the light-emitting elements passes through the light guide plate and is emitted to the outside.
Therefore, when there is no finger contact, light does not enter the light receiving element. However, it does not mean that light is not incident at all, and external light may be incident. This light is incident as noise light that does not contribute to the detection of finger contact. Then, when there is a finger contact for pressing the switch on the light guide plate surface, that is, when there is a finger contact on the switch B as shown in the figure, the light emitting element 7
The light emitted from b is transmitted to the outside through the light guide plate, but is reflected by the finger, and the reflected light enters the light receiving element through the inside of the light guide plate as shown in the figure. Since the detection circuit manages the light emission timing of the light emitting elements that emit light in order, it knows the light emitting element when the light receiving element has output, and detects that the switch B has been pressed. .

[0009]

However, in such an optical touch switch, there is a problem that the amount of light incident on the light receiving element is small when a finger touches the switch. Considering this point in the case of FIG. 6, most of the emitted light emitted from the light emitting element passes through the panel, and most of the light passing through the panel reaches the finger and is reflected by the finger. Since the reflection surface of the finger is an uneven surface, the reflected light is not only reflected light directed toward the light receiving element, but also much reflected light not directed to the light receiving element. That is, the light that has reached the finger is not effectively used for detecting contact of the finger with the panel. As a result, the amount of light incident on the light receiving element is small.

Next, consider FIG. Most of the light emitted from the light emitting element passes through the light guide, and most of the light passing through the light guide reaches the finger, where some light passes through the finger and most of the light passes through the finger. Light will be reflected,
Since the reflection surface of the finger is uneven, the reflected light is not only reflected light that reaches the light receiving element while totally reflecting inside the light guide, but most of the reflected light is not suitable for the light receiving element. ing. For this reason, the amount of light incident on the light receiving element when the finger comes into contact with the light guide is reduced as in the case of FIG.

In the touch switches of FIGS. 6 and 7, since the signal level is low, the S / N ratio is low, and the detection circuit is complicated and expensive. In the present invention, by increasing the difference (signal level) between the light receiving level received by the light receiving element when the finger touches the switch and the light receiving level received by the light receiving element when the finger does not touch the switch, the S / N ratio is increased and the detection sensitivity is improved. It is intended to provide a good and inexpensive optical touch switch.

[0012]

The present invention is configured as follows to solve the above-mentioned conventional problems.

(1) In an optical touch switch using a light emitting element and a light receiving element, when light emitted from the light emitting element enters the light guide and a finger or a predetermined object does not contact the touch surface, the light emitting element is used. Most of the light incident on the light guide is totally reflected on the touch surface and is incident on the light receiving element. When a finger or a predetermined object comes into contact with the touch surface, the incident light is irregularly reflected by the finger or the predetermined object and received. The contact of a finger or a predetermined object is detected by utilizing the fact that incident light incident on the element is greatly reduced.

(2) In the optical touch switch described in the item (1), the emitted light emitted from the light emitting element is guided to the illumination window other than detecting the contact of a finger or a predetermined object.

(3) In the optical touch switch described in (1) or (2), the size of the switch is reduced by providing the light guide with a total reflection surface other than the touch surface.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a conventional detection method, when a finger comes into contact with a panel or a light guide, light emitted from a light emitting element is reflected by the finger, the reflected light is incident on a light receiving element, and the incident light is reflected. The contact of the finger was detected by detecting the amount of light.
That is, the contact of the finger is detected based on whether or not the detection level of the light receiving element is equal to or higher than a predetermined level. Then, there is a problem that the amount of light input to the light receiving element when the finger contacts the switch is small.

The reason why the amount of light is small is that the light reflected from the finger cannot be effectively guided to the light receiving element because the reflection surface of the finger is uneven. Then, the inventor thought that if the reflection surface of the finger is uneven, and the light that reaches the finger is irregularly reflected by the finger, the diffusely reflected light should be considered as an opposite signal. Then, when an optical touch switch was prototyped and examined from such a concept, an optical touch switch with higher sensitivity than before was obtained. Hereinafter, details of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory view of a main part of an optical touch switch according to the present invention, showing a case where no finger touches a touch surface. 1 is a light emitting element, 2 is a light receiving element, 8 is a light guide, and 9 is a touch surface with which a finger contacts. Incident on Outgoing light 5a emitted from the light emitting element
Is totally reflected on the touch surface and the reflected light is directed to the light receiving element. As shown in the figure, the shape of the light guide has the same incident angle and reflection angle with respect to the touch surface as shown in FIG.
5 °. Therefore, in the touch switch of this drawing, most of the light incident on the light guide is totally reflected on the touch surface and reaches the light receiving element. Incidentally, the incident angle and the reflection angle are different depending on the refractive index of the light guide. In consideration of the condition for total reflection in the case of Mitsubishi Rayon's acrylite, it is necessary to set this angle to about 42 ° or more. is there.

Next, a case where a finger is brought into contact with the touch surface of the touch switch will be described with reference to FIG. In FIG. 2, reference numeral 1 denotes a light emitting element, 2 denotes a light receiving element, 5a denotes outgoing light emitted from the light emitting element, and 9 denotes a touch surface. These are all the same as FIG. In this figure, the finger is in contact with the touch surface. In FIG. 1, most of the outgoing light emitted from the light emitting element is reflected on the touch surface and proceeds toward the light receiving element. However, in FIG. 1, the outgoing light emitted from the light emitting element reaches the touch surface and reaches the touch surface. Although the reflected light is totally reflected when there is no finger, the optical condition of the boundary surface changes due to the presence of the finger, and the light reaches the finger without being totally reflected.

Part of the light that reaches the finger is refracted light 10e transmitted through the finger, and part of the light is reflected on the surface of the finger.
Since the optical conditions are not constant at the boundary between the finger and the touch surface, the reflected light is irregularly reflected without going in a fixed direction. Therefore, some light reaches the light receiving element, and most of the light does not reach the light receiving element. Although FIG. 1 shows the reflected light as 5b,
In this drawing, the reflected light is shown as a plurality of reflected lights because the reflected light is irregularly reflected like 10a, 10b, 10c, and 10d. Of these, only the reflected light 10a reaches the light receiving element, and the other reflected light does not reach the light receiving element.

In the conventional method, when the finger touches the touch surface, how much light reaches the light receiving element, that is, the contact of the finger is detected based on the increase amount. In FIG. 2, the reflected light 10a is the light, but in the present invention, when the finger comes into contact with the touch surface, the amount of light reaching the light receiving element is reduced, that is, the amount of decrease is detected. In FIG. 2, since the reflected light beams 10b, 10c, and 10d do not reach the light receiving element, all of these light beams become detection signals. The detection signal includes the refracted light 10e transmitted through the finger. As a result, a large difference between the amount of light incident on the light receiving element when the finger touches the touch surface and when the finger does not touch the touch surface can be obtained. it can.

In the above description, the object in contact with the touch portion is limited to a finger. However, the optical touch switch of the present invention is an object other than a finger, for example, a gloved hand. The contact can be sufficiently detected even when the finger is touched, and can be sufficiently detected even when the finger is touched with the pointing stick, and is not limited to the finger.

Next, the present optical touch switch can be easily applied to an "illuminated touch switch" having an illumination function. When the touch switch is provided in a dark place such as at night, when the switch is operated, the position of the switch may not be known and it may be troublesome. For this reason, an "illuminated touch switch" having a function of illuminating a place where the switch is located is used in such a place. The light emitting element used for this switch is not an infrared light emitting element but a visible light emitting element for illumination. FIG. 3 is a perspective view of the "illuminated touch switch", in which 11 is a case, 9 is a touch surface, and 12 is an illuminating window. Light is emitted from the illuminating window to the outside to illuminate the periphery of the switch.

Here, light emission of the light emitting element will be described. To detect whether or not a finger has touched the touch surface of the touch switch, the light emitting element must emit light, but the light emitting element does not need to emit light continuously. Although continuous light emission may be performed, pulse light emission is usually performed to reduce power consumption.

For example, when pulse emission is performed at a duty of 10%, 90% of the time is an idle time that is not necessary for detecting a touch switch. Since the light-emitting element emits light for 10% of the time, some of the light is used to illuminate the illumination window. However, since the light-emitting time is short, it does not contribute much to illumination. For this reason, light is emitted by adding a certain percentage of the idle time, and the emitted light is guided to an illumination window to illuminate the periphery of the switch.

FIG. 4 shows an "illuminated touch switch" in which an illumination window is added to the optical touch switch described with reference to FIGS.
FIG. In FIG. 4, 1 is a light emitting element, 2 is a light receiving element, 8 is a light guide, 9 is a touch surface, 5a is outgoing light emitted from the light emitting device, 5b is reflected light totally reflected on the touch surface, and Reference numeral 12 denotes an illumination window. In this drawing, a part of the light emitted from the light emitting element 1 is guided to the illumination window 12 and emitted from the window.

In the touch switch of the present invention, a light guide element is provided with a touch surface, and a light emitting element and a light receiving element are arranged so as to be totally reflected on the touch surface. Therefore, as shown in FIG. That is, in a configuration in which the light emitted from the light emitting element reaches the light receiving element by one reflection, the distance between the light emitting element and the light receiving element becomes large, and as a result, the outer shape of the case of the touch switch becomes large. .

Therefore, the size of the touch switch can be reduced by guiding the light emitted from the light emitting element to the light receiving element by two total reflections. In this case, a total reflection surface capable of total reflection is formed on the light guide in addition to the touch surface. An example of such an “illuminated touch switch” is shown in a sectional view in FIG.

In FIG. 5, reference numeral 1 denotes a light emitting element, 2 denotes a light receiving element, 8 denotes a light guide, 9 denotes a touch surface, 5a denotes light emitted from the light emitting element, and 5b denotes a first total reflection surface (touch surface). The reflected light 5d is reflected by the second total reflection surface, and the reflected light reaches the light receiving element. Reference numeral 5c denotes a part of the light emitted from the light emitting element, which is emitted toward the illumination window 12. By forming two total reflection surfaces as shown in the figure, the light emitting element and the light receiving element can be arranged close to each other,
As a result, the shape can be made smaller than when the total reflection surface is one.

[0030]

As described above, according to the conventional optical touch switch detection method, when a finger contacts the switch, light emitted from the light emitting element is reflected by the finger, and the reflected light is incident on the light receiving element. By detecting the amount of the incident light, the contact of the finger is detected. However, since the reflection surface of the finger is uneven, and there is light transmitted through the finger, the reflected light cannot be effectively guided to the light receiving element, and the detection signal detected by the light receiving element is small. Had become.
For this reason, the S / N ratio was small and the detection method was poor in detection sensitivity.

In the present invention, the light emitted from the light-emitting element is guided to the light guide, and the light is totally reflected by the total reflection surface formed on the light guide, so that a constant amount of reflected light is constantly reflected on the light-receiving element. When the finger is touched on the touch surface, a part of the light that has reached is transmitted through the finger and becomes transmitted light (refracted light), but most of the light is reflected on the surface of the finger. . In the reflection, since the optical reflection condition of the boundary surface is not uniform, the reflection direction is not a fixed direction but irregularly reflected. Therefore, the amount of light that can reach the light receiving element is significantly reduced. Since the amount of decrease in light is used as the detection signal, the detection signal is increased, and there is an effect that an optical touch switch having a large S / N ratio, good sensitivity, and low cost can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an optical touch switch according to the present invention.

FIG. 2 is a cross-sectional view when a finger touches the touch switch of FIG. 1;

FIG. 3 is a perspective view of the “illuminated touch switch” of the present invention.

FIG. 4 is a sectional view of the first “illuminated touch switch” of the present invention.

FIG. 5 is a sectional view of the second “illuminated touch switch” of the present invention.

FIG. 6 is a sectional view of a main part of a conventional first optical touch switch.

FIG. 7 is a sectional view of a main part of a second conventional optical touch switch.

[Explanation of symbols]

Reference Signs List 1 light emitting element 2 light receiving element 3 printed circuit board 4 panel 5a light emitted from light emitting element 5b reflected light reflected on first total reflection surface 5c light emitted from light emitting element toward illumination window 5d second total reflection Reflected light reflected by surface 5e Reflected light from finger 6 Light guides 7a to 7d Light emitting element 8 Light guide having total reflection surface 9 Touch surface of finger 10a to 10d Reflected light when finger touches touch surface 10e Transmitted light when a finger touches the touch surface 11 Optical touch switch case 12 Illumination window

Claims (3)

[Claims] In an optical touch switch using a light emitting element and a light receiving element, when light emitted from the light emitting element is incident on a light guide and a finger or a predetermined object does not contact the touch surface, the light is emitted from the light emitting element. Most of the incident light incident on the light guide is totally reflected on the touch surface and is incident on the light receiving element. When a finger or a predetermined object comes into contact with the touch surface, the incident light is received by irregular reflection on the finger or the predetermined object. An optical touch switch, wherein contact of a finger or a predetermined object is detected by utilizing the fact that incident light incident on an element is greatly reduced. 2. The optical touch switch according to claim 1, wherein the light emitted from the light emitting element is guided to an illuminating window in addition to detecting contact with a finger or a predetermined object. 3. The switch is reduced in size by providing a total reflection surface other than the touch surface on the light guide body.
3. An optical touch switch according to claim 2.