DE112007003037T5 - Infrared-suppressed light sensors and use of backlight control sensors - Google Patents

Abstract

Light sensor, which has the following features:
a layer of a first conductivity type,
a second conductivity type region in the first conductivity type layer to form a PN junction photodiode having the first conductivity type layer; and
an oxide layer under the PN junction;
wherein carriers are formed in the layer of the first conductivity type when light including both visible light and infrared (IR) light impinges on the light sensor;
wherein a portion of the carriers formed by the visible light is captured by the second conductivity type zone and contributes to a photocurrent generated by the light sensor; and
wherein a further part of the charge carriers, which is formed due to the IR light penetrating through the oxide layer, is absorbed by the oxide layer and / or a material under the oxide layer and thus does not contribute to the photocurrent, resulting in that the photocurrent mainly represents visible light.

Description

priority claim

• Provisorische US-Patentanmeldung Nr. 60/869,700 mit dem Titel „Light Sensors with Infrared Suppression”, eingereicht am 12.12.2006;
• US-Patentanmeldung Nr. 11/621,443 mit dem Titel „Light Sensors with Infrared Suppression”, eingereicht am 9.1.2007; und
• US-Patentanmeldung Nr. 11/950,325 mit dem Titel „Backlight Control Using Light Sensors with Infrared Suppression”, eingereicht am 4.12.2007.

This application claims priority over the following applications:

• Provisional US Patent Application No. 60 / 869,700 entitled "Light Sensors with Infrared Suppression" filed 12.12.2006;
• U.S. Patent Application No. 11 / 621,443 entitled "Light Sensors with Infrared Suppression" filed Jan. 9, 2007; and
• U.S. Patent Application No. 11 / 950,325 entitled "Backlight Control Using Light Sensors with Infrared Suppression" filed on Dec. 4, 2007.

background

In The interest in the use of ambient light sensors, z. For use as energy saving light sensors for displays, for controlling the backlight of portable devices, such as As mobile phones and laptop computers, and for various other types of light level measurement and management, grown. In addition exists for various reasons an interest in the realization of such ambient light sensors using complementary metal oxide semiconductor (CMOS) technology. First, CMOS circuitry is generally less expensive than other technologies, such as Gallium arsenide or bipolar silicon technologies. Furthermore CMOS circuitry generally consumes less Performance than other technologies. Additionally, CMOS photodetectors can be on the same substrate be formed like other low power CMOS devices, such as B. Metal oxide semiconductor field effect transistors (MOSFETs).

1 shows a cross section of a conventional CMOS light sensor 102 which is essentially a single CMOS photodiode, also referred to as a CMOS photodetector. The light sensor 102 includes an N ⁺ zone 104 which is heavily doped, and a P ^- zone 106 (which may be an epitaxial P ^- zone) which is lightly doped. All of the above elements are most likely formed on a P ⁺ or P ⁺⁺ substrate that is heavily doped. It should be noted that 1 and all other figures representing light sensors are not drawn to scale.

With further reference to 1 form the N ± zone 104 and the P ^- zone 106 a PN junction, more specifically an N ⁺ / P ^- transition. This NP junction is reverse biased, e.g. Using a voltage source (not shown), causing a depletion zone around the PN junction. When light 112 on the photodetector 102 (and in particular to the N ⁺ zone 104 ), electron-hole pairs occur in and adjacent to the diode depletion zone. Electrons immediately become the N ⁺ zone 104 pulled while holes down to the P ^- zone 106 to be driven. These electrons (also called charge carriers) become in the N ⁺ zone 104 captured and generate a measurable photocurrent, the z. B. can be detected using a current detector (not shown). This photocurrent shows the intensity of the light 112 what allows the use of the photodetector as a light sensor.

A problem with such conventional photodetectors is that they can both visible light and non-visible light, such. B. infrared (IR) light detect. This is from the graph in 2 clearly representing an exemplary spectral response of a human eye. It should be noted that the human eye does not perceive IR light beginning at about 800 nm. Thus, the response of a conventional photodetector can be significantly different from the response of a human eye, especially if the light 112 is generated by an incandescent light source that generates large amounts of IR light. This leads to significantly different from the optimum settings when such a sensor 102 is used for setting a backlight or the like.

It There is a desire to provide light sensors that provide spectral sensitivity which are more similar to that of the human eye is. Such light sensors can z. B. for adequately adjusting the backlight of Ads or the like can be used.

Summary

embodiments The present invention relates to light sensors used as ambient light sensors are particularly useful because such sensors are used can, to provide a spectral response similar to that of the human Similar to eye is. Accordingly, you can the light sensors of embodiments of the present invention sometimes as sensors for visible Ambient light be designated.

Embodiments of the present invention also relate to devices and systems comprising such light sensors. In one embodiment, a system includes a display, a light source for viewing the display from behind lights, and a controller to control the brightness of the light source. The system may also include a light sensor to generate a photocurrent that primarily represents the visible light, and the controller may control the brightness of the light source based on a level of the photocurrent. Alternatively, the system may include a light sensor that generates a first photocurrent and a second photocurrent, wherein the first photocurrent indicates both the visible light and the IR light, and the second photocurrent indicates the IR light. In such an embodiment, the controller may control the brightness of the light source based on a level of a differential photocurrent that is generated by determining a difference (which may be a weighted difference) between the first and second photocurrents.

According to specific Embodiments includes a light sensor comprises a layer of a first conductivity type and a zone a second conductivity type in the layer of the first conductivity type to form a PN junction photodiode with the layer of the first conductivity type. Furthermore there is an oxide layer under the PN junction. Become a carrier generated in the layer of the first conductivity type when light, the includes both visible light and infrared (IR) light hits the light sensor. Part of the charge carriers, the due to the visible light is generated by the zone of the second conductivity type captured and carries to a photocurrent generated by the light sensor. One further part of the charge carriers, which is due to the IR light, which penetrates the oxide layer is through the oxide layer and / or a material under the oxide layer absorbs and carries thus not contributing to the photocurrent, causing the photocurrent to be primarily the represents visible light.

According to specific embodiments, the layer of the first conductivity type may be a P ^- layer and the zone of the second conductivity type may be an N ⁺ zone. In other embodiments, the layer of the first conductivity type may be an N ^- layer, and the second conductivity type zone may be a P ⁺ zone.

According to others embodiments According to the present invention, a light sensor comprises a layer a first conductivity type and a first and a second zone of a second conductivity type in the layer of the first conductivity type. The first zone of the second conductivity type and the layer of the first conductivity type form a first PN junction photodiode. The second zone of the second conductivity type and the layer of the first conductivity type form a second PN junction photodiode. At least one more, belonging to the CMOS technology layer covers the second Zone of the second conductivity type (but not the first zone with the second conductivity), where which blocks at least one more layer of visible light while the same transmits at least a portion of the infrared (IR) light. Become a carrier in the layer of the first conductivity type generated when light, both visible light and IR light includes, impinges on the light sensor. Part of the charge carriers, the due to the visible light and the IR light coming on the first Zone of the second conductivity type impinges, is created by the first zone of the second conductivity type captured and carries to a first photocurrent, which is both the visible light and indicates the IR light. Another part of the charge carriers, the due to the IR light is created by the at least one more Layer passes through the second zone of the second conductivity type captured and carries to a second photocurrent, which indicates the IR light. A differential photocurrent, By determining a difference between the first and the second photocurrent is generated has a spectral sensitivity on, in which a substantial portion of the IR light is taken out is. At the difference that is used to calculate the differential current generate, it can be a weighted difference, which compensates for at least a portion of the IR light not passing through the at least one more layer goes through.

According to specific embodiments, it may be in the layer of the first conductivity type to form a P ^- act layer, the first zone of the second conductivity type may be a first N ⁺ region and the second region of the second conductivity type may be a second N ⁺ region , In other embodiments, it may be a N, the layer of the first conductivity type ^- acting layer, the first zone of the second conductivity type may be a first P ⁺ region and the second region of the second conductivity type may be a second P ⁺ region ,

According to certain Embodiments includes the at least one further layer is a layer of silicide. at some embodiments the at least one further layer comprises a layer of polysilicon, covering the second zone of the second conductivity type. A Layer of silicide can spread over the polysilicon. It can have more than one layer of polysilicon be used, with or without silicide layer over the top layer Polysilicon.

According to other embodiments of the present invention, a light sensor comprises a A first conductivity type layer and a first conductivity type first region in the first conductivity type layer to form a first PN junction photodiode having the first conductivity type layer. A well of the second conductivity type is also located in the layer of the first conductivity type and forms a second PN junction photodiode with the layer of the first conductivity type. In addition, a second zone of the second conductivity type is in the well of the second conductivity type, wherein the second zone of the second conductivity type is more heavily doped than the well of the second conductivity type. Charge carriers are generated in the layer of the first conductivity type when light including both visible light and infrared (IR) light impinges on the light sensor. A portion of the charge carriers resulting from the visible light and IR light impinging on the first zone of the second conductivity type is trapped by the first zone of the second conductivity type and contributes to a first photocurrent which is both the visible light as well as the IR light indicates. Another portion of the charge carriers, resulting from the IR light passing through the second conductivity type well, is trapped by the second conductivity type second region in the second conductivity type well and contributes to a second photocurrent which is the IR current. Indicates light. A differential photocurrent generated by the detection of a difference between the first and second photocurrents has a spectral sensitivity in which a substantial portion of the IR light is taken out. The difference used to generate the differential current may be a weighted difference that compensates for at least a portion of the IR light not passing through the at least one further layer.

The layer of the first conductivity type may be a P ^- layer, the first zone of the second conductivity type may be a first N ⁺ zone, the second conductivity type well may be an N-well, and the second zone of the second Conductivity type can be a second N ⁺ zone. Alternatively, the layer of the first conductivity type may be an N ^- layer, the first zone of the second conductivity type may be a first P ⁺ zone, the second conductivity type well may be a P-well, and the second zone of the second conductivity type may be a second P ⁺ -zone.

at certain embodiments At least one further layer belonging to the CMOS technology covers the second zone of the second conductivity type (but not the first zone of the second conductivity type), wherein the at least another layer of visible light blocks off while the same transmits at least a portion of the infrared (IR) light. According to certain embodiments the at least one further layer comprises a layer of silicide. In some embodiments the at least one further layer comprises a layer of polysilicon, covering the second zone of the second conductivity type. A Layer of silicide can spread over the polysilicon. It can have more than one layer of polysilicon be used, with or without silicide layer over the top layer Polysilicon.

embodiments The present invention also relates to methods for Generating a photocurrent that mainly represents visible light and thus a similar response like that of a human eye. embodiments The invention also relates to methods for generating a Differential photocurrent having a spectral response, in which a substantial portion of the IR light is taken out, and thus a similar one Responsiveness like that of the human eye. Embodiments of the The present invention also relates to methods for controlling a backlight in a system that displays and a light source to illuminate the display from behind.

at specific embodiments For example, one method comprises generating a photocurrent that is primarily visible Represents light, and controlling the brightness of the light source (which is a display illuminated from behind) based on the level of the photocurrent. The generating step may include: generating charge carriers responsively upon the reception of incident light, which is both the visible Light as well as infrared (IR) light; Capture a part the charge carrier, which arises because of the visible light, so the part of the Charge carriers too contributes the generated photocurrent; and absorbing a further portion of the charge carriers due to of the IR light is generated, so that the further part of the charge carriers is not contributes to the photocurrent, which leads to, that the photocurrent is mainly the visible light represents.

In other embodiments, a method includes generating a first photocurrent indicative of both the visible light and the IR light and generating a second photocurrent indicative of the IR light. Such a method also includes determining a differential current by determining a difference (which may be a weighted difference) between the first and second photocurrents, the differential photocurrent having a spectral sensitivity in which a substantial portion of the IR light is taken out. The method further comprises controlling the brightness of the light source (which illuminates a display backlit) based on a level of the differential photocurrent.

These Summary is not intended to be a complete description of the embodiments of the present invention. Further and alternative embodiments and the features, aspects and advantages of the present invention become from the following, detailed description, the drawings and the claims seen.

Brief description of the drawings

1 Fig. 12 is a cross-sectional view of a conventional CMOS photodetector type light sensor.

2 Figure 4 is a graph illustrating exemplary spectral response of a human eye.

3 shows a cross-sectional view of a light sensor according to an embodiment of the present invention.

4A shows a cross-sectional view of a light sensor according to another embodiment of the present invention.

4B FIG. 12 is a rough block diagram explaining how a difference between photocurrents detected by the two photodetectors of the light sensor of FIG 4A be generated.

5A shows a cross-sectional view of a light sensor according to another embodiment of the present invention.

5B FIG. 10 is a graph illustrating a simulated spectral response obtained using the light sensor of FIG 5A is reached.

5C FIG. 12 shows a cross-sectional view of a variation of the light sensor incorporated in FIG 5A is shown.

5D FIG. 10 is a graph illustrating a simulated spectral response obtained using the light sensor of FIG 5C is reached.

6A shows a cross-sectional view of a light sensor according to another embodiment of the present invention.

6B FIG. 10 is a graph illustrating the simulated spectral sensitivity produced using the light sensor of FIG 6A is reached.

6C shows a cross-sectional view of a light sensor, which corresponds to that of 6A is similar, but also features of the sensor of 4A includes.

6D shows a cross-sectional view of a light sensor, which corresponds to that of 6A is similar, but also features of the sensor of 5A includes.

7 FIG. 12 shows a rough block diagram of a system including an LCD display and one of the light sensors of the present invention to provide a system according to an embodiment of the present invention that can control backlighting.

8A summarizes certain methods according to embodiments of the present invention for controlling a backlight in a system that includes a display and a light source to illuminate the display from behind.

8B provides additional details about one of the steps of 8A ,

9 summarizes alternative methods in accordance with embodiments of the present invention for controlling a backlight in a system that includes a display and a light source to illuminate the display from behind.

Detailed description

light is absorbed with a characteristic depth, which is due to the wavelength the light is determined. At certain wavelengths, such as z. Visible light in the range of about 400 to 700 nm, is the absorption depth about 3.5 microns or less. In contrast, the absorption depth for IR light greater than that of visible light. For example, the absorption depth for IR light is 800 nm about 8 μm, and the absorption depth for IR light of 900 nm is larger than 20 μm. embodiments of the present invention as described below use this phenomenon.

3 shows a cross-sectional view of a CMOS light sensor 302 according to an embodiment of the present invention. The light sensor 302 includes an N ⁺ zone 304 in a relatively flat P ^- layer 306 under which an oxide layer 310 is provided. At the oxide layer 310 can it be z. For example, it may be silicon dioxide but is not limited thereto. At the P ^- layer 306 it may be an epitaxial P ^- layer, but this need not be the case.

According to specific embodiments, the depth or thickness of the N ⁺ zone is 304 between about 0.05 and 0.15 μm, and the depth or thickness of the P ^- layer 306 is between about 0.1 and 0.3 microns, wherein the thickness of the P ^- layer 306 preferably about twice the thickness of the N ⁺ zone 304 is. According to specific embodiments, the thickness of the oxide layer is 310 an odd multiple of a quarter wavelength of the IR light. When IR light of 800 nm, and thus a quarter wavelength of 200 nm (ie, 0.2 μm), is adopted, the thickness of the oxide layer may be 0.2 μm, 0.6 μm, 1.2 μm, etc.

When light 312 (which includes both visible light and IR light) to the N ⁺ zone of the sensor 302 a large portion of the visible light photons pass through the N ⁺ zone 304 and the P ^- zone 306 absorbed. These photons contribute to the photocurrent passing through the sensor 302 is produced. In contrast, most of the IR light penetrates the oxide layer 310 and is from the substrate layer 307 (which may, for example, be a silicon layer) absorbs and thus does not contribute to the photocurrent passing through the sensor 302 is produced. In this way, the contribution of the IR light to the photocurrent is significantly reduced and preferably eliminated. Thus, as the photocurrent passes through the sensor 302 is generated, mainly based on visible light, the sensor 302 a spectral sensitivity compared to the conventional sensor 102 more like that of a human eye.

In other words, charge carriers are in the P ^- layer 306 generated when light 312 , which includes both visible light and infrared light, on the light sensor 102 incident. Part of the charge carriers, which is created by visible light, pass through the N ⁺ zone 304 captures and contributes to a photocurrent passing through the light sensor 102 is produced. Another part of the charge carriers, which arises due to the IR light, the oxide layer 310 penetrates through the oxide layer 310 or a material 307 separated from the diode under the oxide layer and thus does not contribute to the photocurrent. As a result, the photocurrent mainly represents the visible light.

The referring to 3 described embodiments may be prepared using silicon on insulator (SOI) technology, wherein a thin silicon layer on an insulator, for. As silicon dioxide, is arranged, which in turn on a base substrate (also known as handling wafer) is arranged. This enables separation of the active silicon layer containing circuit patterns from the base substrate. With reference to 3 it can be at the P ^- zone 306 to be such a thin active silicon layer, the oxide 310 may be such an insulator and the substrate 307 it can be a basic substrate. According to specific embodiments, the base substrate (e.g. 307 ) to suppress reflection that might otherwise be caused by the base substrate. If this is the case, the IR light that is the oxide insulator 310 penetrates, through chip housing material such. As an epoxy or a molding material absorbed.

With reference to 3 Alternatively, the described embodiment may be fabricated using silicon on sapphire (SOS) technology, wherein a thin silicon layer is grown on a sapphire (Al ₂ O ₃ ) substrate, ie, an oxide. With reference to 3 it may be in the P ^- zone 306 to be such a thin active silicon layer, and the layers 310 and 307 are replaced by a single sapphire layer.

Although in 3 For example, embodiments of the present invention include multiple such PN junctions over a single oxide layer or multiple oxide layers. In other words, embodiments of the present invention also include multiple such photodetectors that are used together to generate a photocurrent. One of ordinary skill in the art will recognize how this plurality of photodetectors also applies to the embodiments described below. These IR suppression concepts could alternatively be realized using a P ⁺ / N ^- photodiode design, as described in more detail below.

4A shows a cross-sectional view of a CMOS light sensor 402 according to another embodiment of the present invention. The light sensor 402 is shown to be the same two photodetectors 403a and 403b which are preferably sufficiently spaced apart so that they may be considered substantially separated from each other. Additionally or alternatively, the two photodetectors 403a and 403b be separated from each other using an insulating zone (not shown).

The photodetector 403a , which is an N ⁺ zone 404a in a P ^- layer 406 essentially does not differ from a conventional photodetector such. B. with reference to 1 described. So if light 412 on the photodetector 403a shows, the photocurrent passing through the photodetector 403a is generated, both visible light and IR light, the impinges on the detector.

The other photodetector 403b similarly includes an N ⁺ zone 404b in the P ^- layer 406 , which may be an epitaxial P ^- layer. The N ⁺ zone of the photodetector 403b however, is of a silicide layer 408 covered in the CMOS process. The silicide layer 408 is impermeable to visible light (ie, does not transmit visible light), but transmits some of the IR light. So if light 412 on the light sensor 402 shows, the photocurrent passing through the photodetector 403b is generated, non-visible light incident on the detector, but indicates IR light which impinges on the detector.

Thus, the sensor generates 402 a first photocurrent indicating both visible light and IR light and a second photocurrent indicating IR light. In accordance with embodiments of the present invention, by detecting a difference between such photocurrents, a differential photocurrent indicative of primarily visible light may be generated. Such a differential photocurrent corresponds to a spectral sensitivity similar to that of the human eye.

In other words, the light sensor includes 402 the 7-layer 406 in which the N ⁺ zones 404a and 404b are located. The N ⁺ zone 404a and the P ^- layer 406 form a first PN junction photodiode 403a And the N ⁺ region 404b and the P ^- layer 406 form a second PN junction photodiode 403b , The silicide layer 408 , which belongs to the CMOS technology, covers the N ⁺ zone 404b (but not the N ⁺ zone 404a ) to thereby block visible light while transmitting at least a portion of the IR light. Charge carriers are generated in the P ^- layer when light 412 , which includes both visible light and IR light, on the light sensor 402 incident. Part of the charge carriers, due to the visible light and the IR light, on the N ⁺ zone 404a hit, arises, is through the N ⁺ zone 404a captures and contributes to a first photocurrent that indicates both visible light and IR light. Another part of the charge carriers, which arises due to the IR light, that through the silicide layer 308 passes through the N ⁺ zone 404b and contributes to a second photocurrent that indicates the IR light. A differential photocurrent generated by the determination of a difference (well, a weighted difference) between the first and second photocurrents has a spectral sensitivity in which at least a majority of the IR light is taken out.

The thickness of the silicide layer 408 , which depends on the CMOS process, is usually on the order of about 0.01 μm to 0.04 μm, but is not limited thereto. This thickness affects the amount of IR light that the silicide 408 penetrates and to the photocurrent of the detector 403b contributes. Even a very thin layer of silicide 408 blocks off a part of the IR light. Thus, according to specific embodiments of the present invention, an empirically determined weighting factor is used to compensate for the photocurrent passing through the photodetector 403b is generated, indicating only a portion of the IR light that is on the photodetector 403b incident.

4B shows how such a weighted subtraction can be achieved, e.g. Using a current trimmer 417 and / or a current amplifier 418 and a difference device 419 , In the difference device 419 it may be a differential amplifier, but it is not limited thereto. The current trimmer and the current amplifier can be implemented using amplifiers having appropriate gains to provide the desired weighting. As with all embodiments of the present invention, the appropriate weighting values may be determined in any of a number of different ways. For example, simulations can be used, trial and error experiments can be used, or theoretical calculations can be performed. More likely, combinations of these various techniques may be used to properly select the appropriate weighting factors. For example, simulations and / or theoretical calculations may be used to determine approximate weighting factors (which may, for example, result in specific values for resistors of an amplifier circuit), and then trial-and-error experiments may be used to fine-tune the factors. Values are performed. It is also possible that photocurrents are converted into voltages (eg, using transimpedance amplifiers), and the voltages can be adjusted appropriately and a voltage difference determined. These are just a few examples that are not intended to be limiting. One of ordinary skill in the art will recognize that many other ways of adjusting currents and / or voltages fall within the spirit and scope of the present invention. For example, programmable devices (eg, a programmable digital-to-analog converter (DAC)) may be used to properly adjust voltages and / or currents. An advantage of using a programmable device is that it selectively selects the appropriate gain (s) based on additional variables, such as. B. temperature, can adjust. It was It should also be appreciated that current signals or voltage signals may be converted to the digital domain and that all further processing of these signals (eg, setting one or more signals and detecting a difference between signals) may be performed in the digital domain rather than analog components use. Such digital domain processing may be performed using dedicated digital hardware or a general purpose processor such as a digital processor. As a microprocessor done. Other techniques for detecting the differential photocurrent are also within the scope of the present invention.

5A shows a cross-sectional view of a CMOS light sensor 502 according to another embodiment of the present invention. The light sensor 502 is shown to be the same two photodetectors 503a and 503b which are preferably sufficiently spaced apart so that they may be considered substantially separated from each other. Additionally or alternatively, the two photodetectors 503a and 503b be separated from each other using an insulating zone (not shown).

The photodetector 503a , which is an N ⁺ zone 504a in a P ^- layer 506 essentially does not differ from a conventional photodetector such. B. with reference to 1 described, and the photodetector 403a , referring to 4A is discussed. Thus, for additional details of the photodetector 503a referred to the above descriptions. When light 512 on the photodetector 503a shows, the photocurrent passing through the photodetector 503a is generated, both visible light and IR light, which impinges on the detector.

The other photodetector 503b also includes an N ⁺ zone 504b in the P ^- layer 506 , The N ⁺ zone of the photodetector 503b however, is of a polysilicon (poly-Si) layer 510 covered in the CMOS process. Such a poly-Si layer 508 which is normally used to form a gate of a CMOS transistor is opaque to visible light (ie, does not transmit visible light), but it does pass some of the IR light. So if light 512 on the photodetector 503b shows, the photocurrent passing through the photodetector 503b is generated, non-visible light incident on the detector, but the same indicates IR light which impinges on the detector.

Thus, the sensor generates 502 a first photocurrent indicating both visible light and IR light and a second photocurrent indicating IR light. According to embodiments of the present invention, by detecting a difference between such photocurrents, a differential photocurrent may be generated which primarily indicates visible light. Such a differential photocurrent thus indicates the spectral sensitivity of a human eye.

In other words, the light sensor includes 502 the P ^- layer 506 in which the N + zones 504a and 504b are located. The N ⁺ zone 504a and the P ^- layer 506 form a first PN junction photodiode 503a And the N ⁺ region 504b and the P ^- layer 506 form a second PN junction photodiode 503b , The poly-Si layer 510 , which belongs to the CMOS technology, covers the N ⁺ zone 504b (but not the N ⁺ zone 504a ) to thereby block visible light while transmitting at least a portion of the IR light. Charge carriers are generated in the P ^- layer when light 512 , which includes both visible light and IR light, on the light sensor 502 incident. Part of the charge carriers, due to the visible light and the IR light on the N ⁺ zone 504a hit, arises, is through the N ⁺ zone 504a captures and contributes to a first photocurrent that indicates both visible light and IR light. Another part of the charge carriers, which arises due to the IR light, through the poly-Si layer 510 passes through the N ⁺ zone 504b and contributes to a second photocurrent that indicates the IR light. A differential photocurrent generated by the determination of a difference (well, a weighted difference) between the first and second photocurrents has a spectral sensitivity in which at least a majority of the IR light is taken out.

5B FIG. 12 is a graph illustrating a simulated spectral response using the light sensor. FIG 502 from 5A is reached. With reference to 5B represents the line 522 the simulated spectral sensitivity of the normal photodetector 503a and the line 524 represents a simulated spectral response of the photodetector 503b that of the poly-Si layer 510 covered, dar. line 526 represents the differential response associated with the differential photocurrent, wherein the amount of photocurrent from the photodetector 503b multiplied by a weighting factor (also called the normalization factor) of 1.42. Techniques similar to those described above with reference to 4B can be used to generate the differential photocurrent. Other techniques for determining the differential photocurrent are also within the scope of the present invention.

In an alternative embodiment is a layer of silicide over the poly-Si layer 510 of the photodetector 503b formed, which leads to an embodiment, the features of the embodiments of the 5A and 4A combined.

In a further embodiment, the in 5C is shown includes a sensor 502 ' the photodetector 503a and a photodetector 503b ' , the two layers of poly-Si 510 ₁ and 510 ₂ which is above the N ⁺ zone 504b are formed. 5D FIG. 10 is a graph illustrating the simulated spectral response produced using the light sensor. FIG 502 ' from 5C is reached. With reference to 5D represents the line 522 ' the simulated spectral sensitivity of the normal photodetector 503a and the line 524 ' represents the simulated spectral sensitivity of the photodetector 503b ' that of the two poly-Si layers 510 ₁ and 510 ₂ The line 526 ' represents the differential response, wherein the amount of photocurrent from the photodetector 503b ' multiplied by a normalization factor of 1.42. Techniques similar to those described above with reference to 4B can be used to generate the differential photocurrent. Other techniques for detecting the differential photocurrent are also within the scope of the present invention.

Even more layers of poly-Si may be added, if desired. In an alternative embodiment, a layer of silicide over the topmost poly-Si layer (e.g. 510 ₂ ) of the photodetector 503b ' formed, which results in an embodiment, the features of the embodiments of the 5C and 4A combined.

With reference to 2 It can be seen that the spectral sensitivity of a human eye reaches its maximum at about 550 nm. With reference to the lines 526 and 526 ' in the 5B and 5D It can be seen that maxima in the simulated differential spectral sensitivities for the sensors 502 and 502 ' occur between 400 nm and 500 nm. According to specific embodiments of the present invention, a green filter (eg, a filter of about 550 nm) may be applied across the sensors 502 and 502 ' to cause the maxima of the differential response to be closer to 550 nm.

In the embodiments of the 5A and 5C as well as in the embodiment of 4A The light sensors each include a normal photodetector and a photodetector covered by at least one layer associated with CMOS technology that blocks visible light while transmitting at least a portion of the IR light. The one or more CMOS-associated layers may be, but are not limited to, a silicide layer, one or more poly-Si layers, or combinations thereof. In addition, in the embodiments of the 5A and 5C as well as in the embodiment of 4A determines a difference (and more likely a weighted difference) between the photocurrents produced by the two photodetectors, the response of the differential photocurrent (referred to as differential response) being similar to that of the human eye.

6A shows a cross-sectional view of a CMOS light sensor 602 according to another embodiment of the present invention. The light sensor 602 is shown to be the same two photodetectors 603a and 603b which are preferably sufficiently spaced apart so that they may be considered substantially separated from each other. Additionally or alternatively, the two photodetectors 603a and 603b be separated from each other using an insulating zone (not shown).

The photodetector 603a , which is an N ⁺ zone 604a in a P ^- layer 606 essentially does not differ from a conventional photodetector such. B. with reference to 1 described, and the photodetector 403a , referring to 4A is discussed. Thus, for additional details of the photodetector 603a referred to the above descriptions. When light 612 on the photodetector 603a shows, the photocurrent passing through the photodetector 603a is generated, both visible light and IR light incident on the detector to.

The other photodetector 603b includes an N-tub 612 in the P ^- layer 606 and an N ⁺ zone 604b in the N-tub 612 , where the N ⁺ -zone is more heavily doped than the N-well 612 , In this case, the PN junction of the photodiode occurs 603b between the N-tub 612 and the P ^- layer 606 , which may be an epitaxial P ^- layer, on. The N-well is preferred 604b deep enough so that it absorbs the photons of visible light, thereby increasing the extent to which the visible light contributes to the photocurrent through the photodetector 603b is reduced (or this is preferably completely prevented). In contrast, the photons of IR light penetrate deeper into the photodetector 603b under the N-tub 612 one. This causes the photodetector 603b generates a photocurrent that is mainly the IR part of the light 612 displays.

In other words, the light sensor includes 602 the P ^- layer 606 in which the N ⁺ zone 604a and the N-tub 612 are located. The N ⁺ zone 604b is located in the N-tub 612 , The N ⁺ zone 604a and the P ^- layer 606 form a first PN junction photodiode 603a , The N-tub 612 and the P ^- layer 606 form a second PN junction photodiode 603b , Charge carriers are generated in the P ^- layer when light 612 , which includes both visible light and IR light, on the light sensor 602 incident. A portion of the carriers, the result of the visible light and the IR light based on the N ⁺ region 604a is incident, is captured by the N ⁺ zone and contributes to a first photocurrent that indicates both visible light and IR light. Another part of the charge carrier, which is due to the IR light passing through the N-well, passes through the N ⁺ region 604b in the N-tub 612 and contributes to a second photocurrent that indicates the IR light. A differential photocurrent generated by the determination of a difference (well, a weighted difference) between the first and second photocurrents has a spectral sensitivity in which at least a majority of the IR light is taken out.

According to specific embodiments, the depth of the N-well is 612 between about 1 and 3 μm, and the depth of the N ⁺ zone 604b is between about 0.2 and 0.5 microns.

6B FIG. 10 is a graph illustrating the simulated spectral response produced using the light sensor. FIG 602 from 6A is achieved, wherein the depth of the N-well 612 is 2 microns. With reference to 5B represents the line 622 the simulated spectral sensitivity of the normal photodetector 603a and the line 624 represents the simulated spectral sensitivity of the photodetector 603b which is the N ⁺ zone 604b in the N-tub 612 The line 626 represents the differential response associated with the differential photocurrent, where the amount of photocurrent from the photodetector 603b multiplied by a standardization factor of 1.20. Techniques similar to those described above with reference to 4B can be used to generate the differential photocurrent. Other techniques for detecting the differential photocurrent are also within the scope of the present invention.

According to a further embodiment of the present invention, which in 6C is shown is a sensor 602 ' the sensor 602 similar, except that a layer of silicide 608 (similar to the silicide 408 , referring to 4A discussed) above the N ⁺ zone 604b is formed to a photodetector 603b ' to build. This leads to an embodiment which incorporates the features of the embodiments of 6A and 4A combined.

According to a further embodiment of the present invention, which in 6D is shown is a sensor 602 '' the sensor 602 similar, except that a layer of polysilicon 610 (similar to the poly-Si layer 510 referring to 5A discussed) above the N ⁺ zone 604b is formed to a photodetector 603b '' to build. This leads to an embodiment which incorporates the features of the embodiments of 6A and 5A combined. In addition, a silicide layer may overlay the poly-Si layer 610 be formed. One or more further layers of poly-Si may overlie the poly-Si layer 610 be formed as it is with reference to 5C was discussed. A silicide layer may be formed over the top poly-Si layer.

In the embodiments described above, the N ⁺ regions are described as being arranged or implanted in a P ^- layer. For example, the N ⁺ zone 304 in the embodiment of 3 in the P ^- layer 306 arranged or implanted. Alternatively, the zone 304 a P ⁺ zone, and the layer 306 may be an N ^- layer. Another example is the N ⁺ zones 404a and 404b in the embodiment of 4A shown to be in the P ^- layer 406 are implanted on a P ⁺⁺ layer 407 located. In alternative embodiments, the semiconductor conductivity materials are reversed. Ie. heavily doped P ⁺ regions may be implanted in a lightly doped N ^- layer on a heavily doped N ⁺⁺ layer. Similar variations also apply to the other embodiments of the present invention. Any such variation also falls within the scope of the present invention.

The light sensors of embodiments of the present invention may be used as visible ambient light sensors, e.g. B. for controlling the backlight in portable devices such. Mobile phones and laptop computers, and various other types of light level measurement and management. The term "visible ambient light sensor" is used herein in contrast to the simple "ambient light sensor" because the sensors of embodiments of the present invention are primarily responsive to visible light by suppressing or subtracting out a response to IR light. Without such suppression or subtraction, the response of a sensor would differ significantly from the response of the human eye. On the other hand, by suppressing or subtracting the response to IR light, the response is of the sensor similar to that of the human eye, which provides for a more optimal backlight control.

The Sensors for Visible ambient light is also advantageous because of the same CMOS technology which is generally less expensive than other technologies, such as Gallium arsenide or bipolar silicon technologies. Further CMOS circuitry generally consumes less Performance than other technologies. In addition, CMOS light sensors can open be formed on the same substrate as other CMOS devices with low power, such as B. Metal oxide semiconductor field effect transistors (MOSFETs).

The light sensors of embodiments of the present invention may be used in many environments, such as e.g. In an LCD display environment as mentioned above and as now described below with reference to FIG 7 described. Embodiments of the present invention also relate to systems and apparatus comprising the light sensors of the invention described above. In such devices, it may, for. As a laptop computer, a mobile phone, a music player, portable DVD players, etc. act.

7 shows a rough diagram of a liquid crystal display (LCD) device 700 according to an embodiment of the present invention, wherein z. B. can act as a type Gatetreiber type LCD device in the panel (GIP). The LCD device is shown as having a control circuit 700 , a gate driver circuit 702 , a data driver circuit 704 and mixed light guides and LCD panel 706 includes. The gate driver circuit 702 is sometimes referred to as the gate line driver. The data driver circuit 704 is sometimes referred to as the source line driver. The LCD device is also shown to include the same gate lines G1 to GN and data lines D1 to DM crossing each other.

At the intersection of each gate line G1 to GN and each data line D1 to DM is a thin film transistor (TFT), z. As a polysilicon or a-Si TFT. The gate of a TFT is connected to one of the gate lines G1 to GN, the source of the TFT is connected to one of the data lines D1 to DM, and the drain of the TFT is connected to a terminal (sometimes referred to as a pixel electrode) of a liquid crystal cell C1c. Another terminal of the C1c is connected to a common voltage (Vcom). Also shown is a storage capacitor Cs connected in parallel with the Clc between the drain of the TFT and Vcom. TFT, C1c and Cs may be collectively referred to as a pixel. The pixels are in a matrix in the LCD panel 706 arranged.

The gate driver circuit 702 has a plurality of gate line outputs G1 to GN, which are the gate lines G1 to GN of the panel 706 drive sequentially by providing gate drive pulses, sometimes referred to as sample pulses or gate line signals.

7 also shows a backlight source 712 in which it is z. B. can be an array of light-emitting diodes (LED) and the backlight for the LCD panel 706 supplies. Such a LED array can, for. An RGB array configured to provide white light, or the array may include white LEDs. Also in 7 shown are a backlight driver 714 and a controller 708 , It is also possible that the backlight driver 714 in the controller 708 is implemented.

The system of 7 Also includes an IR-suppressed light sensor, which may be any of the light sensors of the various embodiments of the present invention described above (ie 402 . 502 . 502 ' . 602 . 602 ' or 602 '' ) can act. In accordance with specific embodiments of the present invention, the IR-suppressed light sensor may be used as a visible ambient light sensor providing spectral sensitivity similar to that of the human eye and used to adjust the brightness of the backlight source 712 adjust.

In particular, when the light sensor 402 is used, the sensor generate a photocurrent that mainly represents visible light. The controller may adjust the backlight based on the level of such a photocurrent. The controller may adjust the level of the signal z. B. determine that the photocurrent using an analog-to-digital converter (ADC) 714 is converted to a digital signal and the digital signal to the controller 708 is delivered.

Alternatively, the light sensor 502 . 502 ' . 602 . 602 ' or 602 '' be used to generate a first photocurrent indicative of both the visible light and the IR light and a second photocurrent indicative of the IR light, so that a differential photocurrent obtained by detecting a difference between the first and the second photocurrent, has a spectral sensitivity in which a substantial portion of the IR light is taken out. The differential photocurrent can z. B. be generated in the manner described with reference to the above 4B which shows how a weighted subtraction can be achieved, e.g. Using a current trimmer 417 and / or a current amplifier 418 and a difference device 419 , Alternatively, both the first and second photocurrents may be through respective ADCs 714 be converted into digital signals, and the controller 708 For example, the difference (which may be a weighted difference) may be determined between the first and second photocurrents. It is also possible that photocurrents are converted into voltages before they are sent to an ADC 714 be delivered or before they are delivered to a differential device. In either case, the controller may determine the level of the differential photocurrent and control the brightness of the backlight source based on the level.

The control 708 , which may receive one or more signals as described above, may use such one or more signals to control the ambient light. Based on the ambient light level, the controller can 708 Adjust the brightness of the backlight to maintain an appropriate amount of backlighting with respect to the ambient light level while at the same time conserving power. In other words, the light sensors can 402 . 502 . 502 ' . 602 . 602 ' . 602 '' or 602 ' be used in a feedback loop for controlling the backlight.

The greater the brightness of the backlight, the greater the contrast, which provides a better view of a display in high visible ambient light. Conversely, if the visible ambient light is relatively weak, less contrast is needed to view the display. Thus, to reduce the power consumption resulting from backlighting, less backlighting may be used when the visible ambient light is relatively weak. Accordingly, the controller 708 the brightness of the backlight source 712 such that the backlight is reduced in response to a decrease in visible ambient light (to save power) and the backlight is boosted in response to an increase in visible ambient light. The control 708 can the backlight source 712 directly or via the backlight driver 714 Taxes.

7 shows how the light sources can be used to set the backlight of TFT LCD displays. However, embodiments of the present invention are not limited to use with such displays. Rather, embodiments of the present invention may be used with other types of backlit displays, including, but not limited to, OLED displays. Such backlit displays can z. B. belong to a portable device, including but not limited to mobile phones, laptop computers, MP3 or other music players that have a display, portable DVD players, etc.

Certain embodiments The present invention also relates to methods for producing from photocurrents, the main ones show visible light but no IR light. In other words relate to certain embodiments of the present invention also provides a method for providing a light sensor, which has a spectral sensitivity similar to that of the human Similar to eye is. additionally relate to embodiments the present invention also methods for using the im Previously described light sensors and systems and devices, use such sensors.

The rough flowchart of 8A summarizes certain methods in accordance with embodiments of the present invention for controlling backlighting in a system having a display (e.g. 706 ) and a light source (eg 712 ) to illuminate the display from behind. At step 802 For example, a photocurrent mainly representing visible light is generated. At step 804 For example, the brightness of the light source is controlled based on a level of the photocurrent in any of the ways described above. The rough flowchart of 8B Provides some additional details about step 802 , With reference to 8B be at step 812 responsive to receiving incident light including both visible light and infrared (IR) light, producing carriers. At step 814 For example, a part of the carriers formed by the visible light is trapped, so that the part of the carriers contributes to the generated photocurrent. At step 816 For example, another part of the charge carrier, which is formed due to the IR light, is absorbed, so that the further part of the charge carriers does not contribute to the photocurrent, which results in that the photocurrent mainly represents the visible light. The light sensor 302 referred to above with reference to 3 can be used to the steps 812 - 816 and more generally step by step 802 perform. A controller (eg 708 ) can be used to step 804 perform.

The rough flowchart of 9 summarizes alternative methods of the present invention for controlling a backlight in a system that includes a display and a light source to illuminate the display from the back. At step 902 a first photocurrent is generated which indicates both the visible light and the IR light. At step 904 a second photocurrent is generated which indicates the IR light. At step 906 For example, a differential current is detected by determining a difference (eg, a weighted difference) between the first and second photocurrents, the differential photocurrent having a spectral response in which a substantial portion of the IR light is removed. At step 908 For example, the brightness of the light source is controlled based on a level of the differential photocurrent in any of the ways described above. The light sensors 402 . 502 . 502 ' . 602 . 602 ' or 602 '' Can be used to follow the steps 902 - 906 perform. A controller (eg 708 ) can be used to step 908 perform.

Even though in the foregoing, various embodiments of the present invention It should be noted that the same were presented as examples and not as limitations. It is for the relevant skilled person obvious that various changes in shape and details can be made to it, without the nature or deviate from the scope of the invention.

scope and scope of the present invention are not intended to be exhaustive any of the exemplary ones described above embodiments limited be, but only by the following claims and their equivalents be defined.

SUMMARY

It are described light sensors, mainly on visible light appeal while Infrared light suppressed becomes. Systems are described which include such light sensors. Such a system may include a display, a light source around the Backlit display, and include a control to the brightness of the light source based on a feedback to be controlled, which is received by such light sensors. It Also, methods for controlling a backlight are described.

Claims (46)

Light sensor, which has the following features: a Layer of a first conductivity type, a Zone of a second conductivity type in the layer of the first conductivity type to form a PN junction photodiode with the layer of the first conductivity type; and an oxide layer under the PN junction; wherein charge carriers in the Layer of the first conductivity type be generated when light, both visible light and Infrared (IR) light hits the light sensor; in which a part of the charge carriers, which arises due to the visible light, through the zone of the second conductivity type is captured and contributes to a photocurrent passing through the light sensor is produced; and another part of the charge carrier, the due to the IR light that penetrates the oxide layer, through the oxide layer and / or a material under the oxide layer is absorbed and thus does not contribute to the photocurrent, which that leads to the photocurrent mainly the visible light represents. Light sensor according to claim 1, wherein the layer of the first conductivity type is an epitaxial Layer has. The light sensor according to claim 1, wherein: the first conductivity type layer has a P ^- layer; and the second conductivity type zone has an N ⁺ region. The light sensor according to claim 1, wherein: the first conductivity type layer has an N ^- layer; and the second conductivity type zone has a P ⁺ region. A light sensor comprising: a layer of a first conductivity type; a first zone of a second conductivity type in the first conductivity type layer to form a first PN junction photodiode having the first conductivity type layer; a second region of the second conductivity type in the first conductivity type layer to form a second PN junction photodiode having the first conductivity type layer; and at least one further layer associated with the CMOS technology covering the second zone of the second conductivity type but not the first zone of the second conductivity type, the at least one further layer blocking visible light while the same covering at least a portion of the infrared (IR). -Light lets through; wherein carriers are formed in the layer of the first conductivity type when light including both visible light and IR light impinges on the light sensor; wherein a portion of the carriers, which is due to the visible light and the IR light incident on the first zone of the second conductivity type, is captured by the first zone of the second conductivity type and contributes to a first photocurrent which is both the visible light as well as the IR light indicates; and wherein another portion of the charge carriers resulting from the IR light passing through the at least one further layer is captured by the second zone of the second conductivity type and contributes to a second photocurrent indicative of the IR light; and wherein a differential photocurrent generated by the detection of a difference between the first and second photocurrents has a spectral sensitivity in which a substantial portion of the IR light is taken out. Light sensor according to claim 5, where the difference used is the difference current to generate a weighted difference that compensates for that at least a portion of the IR light not through the at least one passes through another layer. Light sensor according to claim 6, wherein the layer of the first conductivity type an epitaxial Layer has. The light sensor according to claim 5, wherein: the layer of the first conductivity type has a P ^- layer; the first zone of the second conductivity type has a first N ⁺ zone; and the second zone of the second conductivity type has a second N ⁺ zone. The light sensor according to claim 5, wherein: the first conductivity type layer has an N ^- layer; the first zone of the second conductivity type has a first P ⁺ -zone; and the second zone of the second conductivity type has a second P ⁺ zone. Light sensor according to claim 5, wherein the at least one further layer comprises a layer of silicide. Light sensor according to claim 5, wherein the at least one further layer is a layer of polysilicon having. Light sensor according to claim 5, wherein the at least one further layer comprises a layer of polysilicon, covering the second zone of the second conductivity type, and a Layer of silicide over the Having polysilicon. Light sensor according to claim 5, wherein the at least one further layer comprises a first layer of polysilicon, covering the second zone of the second conductivity type, and at least another layer of polysilicon over the first layer of polysilicon having. Light sensor according to claim 13, wherein the at least one further layer comprises a layer of silicide over the having top layer of polysilicon. Light sensor, which has the following features: a Layer of a first conductivity type; a first zone of a second conductivity type in the layer of the first conductivity type Formation of a first PN junction photodiode with the layer of the first conductivity type; a Tub of the second conductivity type in the layer of the first conductivity type forming a second PN junction photodiode with the layer of the first conductivity type; and a second zone of the second conductivity type in the trough of the second conductivity type, wherein the second zone of the second conductivity type dopes more is as the well of the second conductivity type; wherein charge carriers in the Layer of the first conductivity type be generated when light, both visible light and Infrared (IR) light hits the light sensor; in which a part of the charge carriers, due to the visible light and the IR light coming to the first zone of the second conductivity type impinges, through the first zone of the second conductivity type is captured and contributes to a first photocurrent, the indicating both the visible light and the IR light; in which another part of the charge carriers, which arises due to the IR light passing through the tub of the second conductivity type passes through the second zone of the second conductivity type in the tub of the second conductivity type is captured and contributes to a second photocurrent that the Indicates IR light; and wherein a differential photocurrent passing through the determination of a difference between the first and the second Photocurrent is generated, has a spectral sensitivity, in which a substantial part of the IR light is taken out. Light sensor according to claim 15, wherein the difference used to increase the differential current generate, a weighted difference that balances that at least a portion of the IR light is not through the at least one further layer passes. A light sensor according to claim 15, wherein the layer of the first conductivity type is epitaxial has sche layer. The light sensor according to claim 15, wherein: the layer of the first conductivity type has a P ^- layer; the first zone of the second conductivity type has a first N ⁺ zone; the well of the second conductivity type has an N-well; and the second zone of the second conductivity type has a second N ⁺ zone. The light sensor according to claim 15, wherein: the first conductivity type layer has an N ^- layer; the first zone of the second conductivity type has a first P ⁺ -zone; the well of the second conductivity type has a P-well; and the second zone of the second conductivity type has a second P ⁺ zone. Light sensor according to claim 15, further comprising: at least one more, belonging to the CMOS technology Layer, the second zone of the second conductivity type, but not the first zone of the second conductivity type covered, wherein the at least one further layer of visible light blocks off while it transmits at least a portion of the infrared (IR) light. Light sensor according to claim 20, wherein the at least one further layer comprises a layer of silicide having. Light sensor according to claim 20, wherein the at least one further layer is a layer of polysilicon having. Light sensor according to claim 20, wherein the at least one further layer is a layer of polysilicon, covering the second zone of the second conductivity type, and a Layer of silicide over the Having polysilicon. Light sensor according to claim 20, wherein the at least one further layer comprises a first layer Polysilicon, which is the second zone of the second conductivity type covered, and at least one more layer of polysilicon over the having first layer of polysilicon. Light sensor according to claim 24, wherein the at least one further layer comprises a layer of silicide over the having top layer of polysilicon. System having the following features: a Display; a light source to illuminate the display from behind; a Control to control the brightness of the light source; and one Light sensor to generate a photocurrent, mainly the represents visible light; in which the controller controls the brightness of the light source based on a Level of the photocurrent controls; and wherein the light sensor following Features includes: a layer of a first conductivity type; a Zone of a second conductivity type in the layer of the first conductivity type to form a PN junction photodiode with the layer of the first conductivity type; and an oxide layer under the PN junction; wherein charge carriers in the Layer of the first conductivity type be generated when light, both visible light and Infrared (IR) light hits the light sensor; in which a part of the charge carriers, which arises due to the visible light, through the zone of the second conductivity type is captured and contributes to the photocurrent passing through the light sensor is produced; and another part of the charge carrier, the due to the IR light that penetrates the oxide layer, through the oxide layer and / or a material under the oxide layer is absorbed and thus does not contribute to the photocurrent, which that leads to the photocurrent mainly the visible light represents. System according to claim 26, wherein the layer of the first conductivity type has an epitaxial Layer has. The system of claim 26, wherein: the layer of the first conductivity type has a P ^- layer and the zone of the second conductivity type has an N ⁺ zone; or the layer of the first conductivity type has an N ^- layer and the zone of the second conductivity type has a P ⁺ region. A system comprising: an indicator; a light source to illuminate the display from behind; a controller for controlling the brightness of the light source; and a light sensor for generating a first photocurrent and a second photocurrent, the first photocurrent indicating both the visible light and the IR light and the second photocurrent indicating the IR light; and wherein the controller controls the brightness of the light source based on a level of a differential photocurrent obtained by determining a difference is generated between the first and the second photocurrent; and wherein the differential photocurrent has a spectral response in which a substantial portion of the IR light is taken out. System according to claim 29, wherein the light sensor comprises the following features: a layer a first conductivity type; a first zone of a second conductivity type in the layer of the first conductivity type forming a first PN junction photodiode with the layer of the first conductivity type; a second zone of the second conductivity type in the layer of the first conductivity type forming a second PN junction photodiode with the layer of the first conductivity type; and at least one more layer belonging to the CMOS technology, but not the second zone of the second conductivity type the first zone of the second conductivity type covered, wherein the at least one further layer of visible light blocks off while it transmits at least part of the infrared (IR) light; in which charge carrier in the layer of the first conductivity type be generated when light, both visible light and IR light impinges upon the light sensor; being a Part of the charge carriers, due to the visible light and the IR light coming to the first zone of the second conductivity type impinges, through the first zone of the second conductivity type is captured and contributes to the first photocurrent, the indicating both the visible light and the IR light; and where another part of the charge carriers, which arises due to the IR light passing through the at least one passes through the second zone of the second conductivity type is captured and contributes to the second photocurrent, the indicates the IR light. System according to claim 30, wherein the difference used to generate the difference current, a weighted difference that balances that at least one Part of the IR light not through the at least one more layer passes. System according to claim 30, wherein the layer of the first conductivity type is an epitaxial Layer has. The system of claim 30, wherein: the layer of the first conductivity type has a P ^- layer, the first region of the second conductivity type has a first N ⁺ region, and the second region of the second conductivity type has a second N ⁺ zone; or the layer of the first conductivity type has an N ^- layer, the first region of the second conductivity type has a first P ⁺ region, and the second region of the second conductivity type has a second P ⁺ region. System according to claim 30, wherein the at least one further layer at least one of comprising: a layer of silicide; a layer made of polysilicon; a layer of polysilicon, which is the second Zone of the second conductivity type covered, and a layer of silicide over the polysilicon; and a first layer of polysilicon, which is the second zone of the second conductivity type covered, and at least one more layer of polysilicon over the first layer of polysilicon. System according to claim 34, wherein the at least one further layer comprises a layer of silicide over a having top layer of polysilicon. System according to claim 30, wherein the light sensor has the following features: a Layer of a first conductivity type; a first zone of a second conductivity type in the layer of the first conductivity type forming a first PN junction photodiode with the layer of the first conductivity type; a Tub of the second conductivity type in the layer of the first conductivity type under Bildumg a second PN junction photodiode with the layer of the first conductivity type; and a second zone of the second conductivity type in the trough of the second conductivity type, wherein the second zone of the second conductivity type dopes more is as the well of the second conductivity type; wherein charge carriers in the Layer of the first conductivity type be generated when light, both visible light and Infrared (IR) light hits the light sensor; in which a part of the charge carriers, due to the visible light and the IR light coming to the first zone of the second conductivity type impinges, through the first zone of the second conductivity type is captured and contributes to the first photocurrent, the indicating both the visible light and the IR light; and where another part of the charge carriers, which is due to the IR light created by the heat of the second conductivity type passes through the second zone of the second conductivity type in the tub of the second conductivity type is captured and contributes to the second photocurrent, the indicates the IR light. The system of claim 36, wherein the difference used to generate the difference current is a weighted difference that compensates for at least a portion of the IR light not passes through the at least one further layer. System according to claim 36, wherein the layer of the first conductivity type an epitaxial Layer has. The system of claim 36, wherein: the layer of the first conductivity type has a P ^- layer, the first region of the second conductivity type has a first N ⁺ region, the well of the second conductivity type has an N-well, and the second region of the second Conductivity type has a second N ⁺ zone; or the layer of the first conductivity type has an N ^- layer, the first region of the second conductivity type has a first P ⁺ -zone, the well of the second conductivity type has a P-well, and the second region of the second conductivity type has a second P ⁺ - Zone has. System according to claim 39, further comprising: at least one more, belonging to the CMOS technology Layer, the second zone of the second conductivity type, but not the first zone of the second conductivity type covered, wherein the at least one further layer of visible light blocks off while it transmits at least a portion of the infrared (IR) light. System according to claim 40, wherein the at least one further layer at least one of comprising: a layer of silicide; a layer made of polysilicon; a layer of polysilicon, which is the second Zone of the second conductivity type covered, and a layer of silicide over the polysilicon; and a first layer of polysilicon, which is the second zone of the second conductivity type covered, and at least one more layer of polysilicon over the first layer of polysilicon. System according to claim 41, wherein the at least one further layer comprises a layer of silicide over a having top layer of polysilicon. Method comprising the following steps: Produce of carriers in response to receiving incident light, both which includes visible light as well as infrared (IR) light; capture a part of the charge carriers, which arises because of the visible light, so the part of the charge carrier contributes to the generated photocurrent; and Absorb one further part of the charge carriers, the due to the IR light is generated, so that the other part of the charge carriers not contributes to the photocurrent, which leads to, that the photocurrent is mainly the visible light represents. Method according to claim 43, further controlling the brightness of a light source is used, μm to illuminate a display from behind, based on the photocurrent having. Method comprising the following steps: Produce a first photocurrent, which is both the visible light and indicating the IR light; Produce a second photocurrent indicating the IR light; Determine of a differential current by determining a difference between the first and second photocurrents, the differential photocurrent has a spectral sensitivity in which a substantial Part of the IR light is taken out. Method according to claim 45, further controlling the brightness of a light source is used to illuminate a display from behind has on the differential current.