WO2006027423A1

WO2006027423A1 - Input device comprising an optical sensor and a filter means

Info

Publication number: WO2006027423A1
Application number: PCT/FR2004/002114
Authority: WO
Inventors: Frédéric GUERAULT; Christophe Chesnaud
Original assignee: Simag Developpement
Priority date: 2004-08-09
Filing date: 2004-08-09
Publication date: 2006-03-16

Abstract

The invention relates to an input device comprising a first optical sensor (C1). In addition, the device, which is provided with a first synchronisation input (E1), comprises a first filter means (F1) for isolating a first detection signal (D1) in the output signal (S1) from the first sensor (C1), said detection signal being correlated with the signal received at the first synchronisation input (E1).

Description

Input device comprising an optical sensor followed by a filtering means

The present invention relates to an input device comprising an optical sensor followed by a filtering means. The field of the invention is therefore that of entering information for the control of a machine, in particular an electronic machine such as a computer.

It is thus known to control a computer 9 using a keyboard. However, using a keyboard requires prior learning and dexterity. This is not a very user-friendly control method.

It is also known to control a computer using a mouse, moving object that moves in a plane. The planar movement of the mouse is reproduced by a homothetic displacement of a cursor on the screen of the computer. The mouse is much easier to manipulate than a keyboard. However, it is an accessory that still requires a good gestural control and some experience to be used correctly.

It is also known to control a computer using a touch screen, so that there is more intermediate device between the user and the screen. A simple contact or a finger pressure on a sector of the screen triggers the execution of the command represented in this sector.

According to a first option, the capture can be achieved by means of a transparent slab, often resistive or capacitive, disposed on the screen. When a moving object such as the finger of a user presses a sector of this slab, it generates an electrical information representing the identified sector that has been subjected to the pressure of the moving object. Slab is an expensive component that is technologically complex to manufacture. In addition, its layout on the screen can affect the brightness of the latter.

According to a second option, the input can be made acoustically. In this case, the slab is composed of a material that ensures the propagation of surface acoustic waves. Transducers and ultrasonic sensors are arranged in a network to map the different sectors of the screen.

When an object is in contact with a sector of the screen, it absorbs some of the waves that cross this sector. Again, the slab is a high-tech component that is likely to severely degrade the brightness of the screen. It should also be noted that the two previous options require the use of a particular environment, that of the slab, able to ensure the location of the moving object.

According to a third option, the capture can be performed optically. In this case, a support is provided at the periphery of the front face of the screen. On this medium, a plurality of light sources such as light-emitting diodes are arranged in a matrix arrangement facing a corresponding plurality of detectors. The location of a mobile object located in the immediate vicinity of the screen is performed by identifying the sector of this screen in which all the light beams are interrupted. Here, the brightness of the screen is not disturbed but the support is still a component of relative complexity. This third option is less restrictive on the environment in which the location is practiced since it is sufficient that it is transparent. It does, however, have a limited resolution. In addition, the three previous options are poorly suited to a large screen, with an area greater than or equal to 1 square meter, if only for economic reasons.

It has therefore been proposed to use a digital imaging technique to overcome the constraints related to a physical location of the moving object. The location is here practiced on an image of a localization area appearing near the screen. This image is acquired by means of a sensor such as those used in video cameras and is then subjected to a treatment that defines the area of the screen opposite which is the moving object. As a reference, mention may be made of the international patent application WO 01 93006.

A first limitation is due to the saturation of the sensors when the brightness at the location area is high, this brightness may come in particular from powerful lighting, strong sunlight or significant reflections by metal surfaces. The output signal of a saturated sensor is unreliable because it is disturbed by unwanted signals such as parasites, which leads to a loss of useful information.

A second limitation is due to a sudden change in brightness at the location area, this variation may come from the interruption of a powerful lighting, the passage of a cloud or an undesirable shade. Indeed, imaging methods often use a subtractive technique in which a reference image is subtracted from the image being analyzed. During a sudden change in brightness, the reference image is no longer faithful to reality so that spurious signals appear in the output signal of the sensor.

A first object of the present invention is therefore to reduce the influence of ambient brightness.

According to the invention, an input device comprises a first optical sensor, a first synchronization input, a first filtering means for isolating in the output signal of this first sensor a first detection signal correlated with the signal received on the first input. a first light source whose input is connected to a first power output of a first power supply module, a second light source whose input is connected to a second power output of a second power module, 'food ; in addition, the logical sum of this first and second power outputs is applied to the first synchronization input.

In addition, the first sensor is equipped with a first bandpass filter. This reduces the effect of different light disturbances. It is then preferable that the emission spectrum of the first light source is located mainly in the bandwidth of the first filter. Moreover, the signal delivered on the first power output is not constant.

This facilitates the recovery of the detection signal. Indeed, the signal delivered by the first power output may be periodic. As a convenience, the first sensor and the first light source are assembled.

According to an additional feature of the device, the emission spectrum of the second light source is located mainly in the bandwidth of the first filter. According to a preferred embodiment of the device, the signals delivered by the two power outputs are periodic and have a constant phase shift.

It is always desirable that the first filtering means be provided for practicing synchronous detection. However, when the camera is placed behind the moving object, it is impossible, without knowing the size of it, to estimate the distance which separates it of the screen. On the other hand, the interposition of any body between the camera and the moving object would hide the latter, thereby prohibiting its location. Therefore, care should be taken to install the image sensor relative to the screen. In order to overcome the deficiencies of the imaging technique on a single image, the known principle of stereovision is put into play. This principle makes it possible to determine the real position of the object in space by using two images taken from different angles of view. We can even use more than two images. The international patent application WO 99 40562 discloses a device that detects the finger of a user when it comes into contact with the screen, this without prior information on the finger (its size, for example). International patent application WO 02/29722 describes an imaging method requiring several cameras.

The above imaging systems have another limitation if the location area is not physically delimited, for example by means of a frame. Solutions have been proposed to overcome this limitation but they are unsatisfactory because they require complex computing power quite considerable and they do not eliminate all difficulties. A satisfactory solution in this respect proposes to locate only identified objects such as a suitable glove or a marker; US Pat. No. 2001,024,512 contemplates the use of an infra-red label. However, this solution does not allow the location of any object.

A second object of the present invention is therefore a high-reliability optical capture device capable of locating all types of objects.

According to the invention, the device comprises a second optical sensor, provided with a second synchronization input, and it comprises a second filtering means for isolating in the output signal of this second sensor a second detection signal correlated to the received signal. on the second synchronization input.

According to a first option, the second sensor is equipped with a second band-pass filter whose bandwidth is distinct from that of the first filter.

In addition, the second power output is also connected to the second synchronization input. In addition, the emission spectrum of the second light source is located mainly in the bandwidth of the second filter.

Then, it is desirable that the second filtering means is provided for practicing synchronous detection. According to a second option, the device comprising a second optical sensor, this device being provided with a second synchronization input, it comprises a second filtering means for isolating in the output signal of this second sensor a second detection signal correlated to the second signal received on the second synchronization input. Preferably, the second sensor is equipped with a second bandpass filter whose bandwidth is identical to that of the first filter.

In addition, the logical sum of the first and second power outputs is applied to the second synchronization input.

In addition, the second filtering means is provided for practicing synchronous detection.

Advantageously, the second sensor and the second light source are assembled.

The present invention will now appear in greater detail in the context of the following description of exemplary embodiments given by way of illustration with reference to the appended figures which represent: FIG. 1, a diagram of a device provided with a sensor and a light source, Figure 2, a diagram of a device provided with a sensor and two light sources, and - Figure 3, a diagram of a device provided with two sensors and two light sources.

The elements present in several figures are assigned a single reference.

With reference to FIG. 1, a first optical sensor C1, such as a CMOS or CCD detector used in the cameras, delivers a first output signal S1 to a first filtering means F1.

A first light source L1 is here arranged coaxially with the sensor C1, so that it surrounds it. This first source L1 is powered by the output P1 of a first power supply module AL1. Preferably, this light source L1 has a narrow-band emission spectrum and is therefore arranged a first optical filter pass- low PB1 on IΘ first sensor C1, filter whose bandwidth covers most of this emission spectrum. When it is necessary to overcome disturbances due to ambient light, this bandwidth is located at least partly outside the visible spectrum. A first optical filtering is thus performed.

It is also possible to perform an electronic filtering, in which case it is desirable that the signal delivered by the first power supply module AL1 is not constant. Indeed, if this signal is periodic, the first filtering means can easily combine this periodic signal and the first output signal S1.

According to a preferred embodiment, the first power output P1 delivers a pulsed periodic signal, in other words a signal taking a non-zero constant value, a first plateau, during a first fraction of the period and taking a zero value during the remainder of the period. this period. Thus, the first filtering means F1 produces a first detection signal D1 which is equal to the first output signal in the presence of the first stage and which is zero in the opposite case. In fact, this detection signal D1 results from the logic function AND applied to the first output signal S1 and to the signal derived from the first power output P1. We can thus speak of synchronous detection, whereas it is a temporal correlation.

It is also conceivable to perform a frequency correlation. In this case, the first power supply module AL1 preferably delivers a sinusoidal signal characterized by a detection frequency. The first filtering means F1 now isolates the first detection signal D1 by retaining the component of the first output signal S1 appearing at the detection frequency.

It will be noted that it is possible to combine within the first filtering means a temporal correlation and a frequency correlation.

With reference to FIG. 2, according to a first variant, the device comprises a second light source L2 fed by a second power output P2 of a second power supply module AL2. Here again, the bandwidth of the first filter PB1 covers most of the emission spectrum of this second light source L2.

Now, the first synchronization input E1 is no longer connected to the first power output P1 but receives the output signal of an operator OP which performs the logic function OR signals from the first P1 and second P2 power outputs . The first power output P1 delivers as above a pulsed signal characterized by a first stage.

The second power output P2 delivers a pulsed signal of the same period characterized by a second bearing, signal out of phase with the previous one, so that the two bearings are not present simultaneously.

Here again, the first detection signal D1 results from the logic function AND applied to the first output signal S1 and to the signal injected on the first synchronization input E1.

Thus, an object 012 present in the first beam FA1 coming from the first light source L1 and in the second beam FA2 coming from the second light source L2 will appear clearly in the first detection signal D1 during the first and second levels.

On the other hand, an object O1 contained in the first beam FA1 but not appearing in the second beam FA2 will appear in the first detection signal D1 very clearly during the first stage and much less clearly, if it is not at all, during the second tier.

Similarly, an object 02 in the second beam FA2 but not appearing in the first beam FA1 will appear in the first detection signal D1 very clearly during the second stage and much less clearly, if it is not at all, during the first landing.

Thus, it is easy to identify the objects present in a location zone defined by the intersection of the first FA1 and second FA2 beams, because they produce the same information during the two levels, which is not the case for objects located in outside this area. With reference to FIG. 3, in order to benefit from the advantages inherent in stereovision, the device furthermore comprises a second optical sensor C2 delivering a second output signal S2.

In addition, a second filtering means F2 is provided for isolating in the second output signal S2 a second detection signal D2 correlated to the signal received on a second synchronization input E2.

The second sensor C2 is preferably equipped with a second bandpass filter PB2 whose bandwidth is identical to that of the first bandpass filter PB1.

The second synchronization input E2 is connected to the first synchronization input E1 and, therefore, in the present case, the second filtering means F2 functions as the first F1. According to one variant, the second band-pass filter PB2 has a different bandwidth than that of the first band-pass filter PB1. In this case, the emission spectrum of the second light source L2 is adapted to the second bandpass filter PB2. Naturally, the first E1 and second E2 sync inputs are no longer connected. The first F1 and second F2 filtering means operate as indicated above with reference to Figure 1.

The advantage of this variant is to take advantage of two detection signals D1, D2, each in a separate optical band. Thus, if one of these bands has troublesome disturbances, it is still possible to process the information in the other band.

The embodiment of the invention presented above was chosen for its concrete character. It would not be possible, however, to exhaustively list all the embodiments covered by this invention. In particular, any means described may be replaced by equivalent means without departing from the scope of the present invention.

Claims

1) Input device comprising a first optical sensor C1, a first synchronization input E1, a first filtering means F1 for isolating in the output signal S1 of this first sensor C1 a first detection signal D1 correlated to the signal received on said first synchronization input E1, furthermore comprising a first light source L1 whose input is connected to a first power output P1 of a first power supply module AL1, a second light source L2 whose input is connected to a power supply second power output P2 of a second power supply module AL2, characterized in that the logical sum of this first P1 and this second P2 power outputs is applied to said first synchronization input E1.

2) Device according to claim 1, characterized in that said first sensor C1 is equipped with a first bandpass filter PB1.

3) Device according to claim 2, characterized in that the emission spectrum of said first light source L1 is located mainly in the bandwidth of said first filter PB1.

4) Device according to any one of the preceding claims, characterized in that the signal delivered on said first power output P 1 is not constant.

5) Device according to claim 4, characterized in that the signal delivered by said first power output P1 is periodic.

6) Device according to any one of the preceding claims, characterized in that said first sensor C1 and said first light source L1 are assembled.

7) Device according to any one of the preceding claims, characterized in that the emission spectrum of said second L2 light source is located mainly in the bandwidth of said first filter PB1.

8) Device according to any one of claims 1 to 3, 6 or 7, characterized in that the signals delivered by said power outputs P1, P2 are periodic and have a constant phase shift.

9) Device according to claim 8, characterized in that said first filtering means F1 is provided for practicing synchronous detection.

10) Device according to any one of the preceding claims characterized in that, comprising a second optical sensor C2, provided with a second synchronization input E2, it comprises a second filtering means F2 for isolating in the output signal S2 of this second sensor C2 a second detection signal D2 correlated to the signal received on said second synchronization input E2.

11) Device according to claim 10, characterized in that said second sensor C2 is equipped with a second bandpass filter PB2 whose bandwidth is distinct from that of said first filter PB1.

12) Device according to any one of claims 10 or 11, characterized in that said second power output P2 is also connected to said second synchronization input E2.

13) Device according to claim 12, characterized in that the emission spectrum of said second light source L2 is located mainly in the bandwidth of said second filter PB2.

14) Device according to any one of claims 10 to 13, characterized in that said second filtering means F2 is provided for practicing synchronous detection.

15) Device according to any one of claims 1 to 9 characterized in that, comprising a second optical sensor C2, provided with a second synchronization input E2, it comprises a second filtering means F2 for isolating in the output signal S2 of this second sensor C2 a second detection signal D2 correlated to the signal received on said second synchronization input E2.

16) Device according to claim 15, characterized in that said second sensor C2 is equipped with a second bandpass filter PB2 whose bandwidth is identical to that of said first filter PB1.

17) Device according to any one of claims 15 or 16, characterized in that the logical sum of said first P1 and second P2 power outputs is applied to said second synchronization input E2.

18) Device according to claim 17, characterized in that said second filtering means F2 is provided for practicing synchronous detection.

19) Device according to any one of claims 15 to 18, characterized in that said second sensor C2 and said second light source L2 are assembled.