WO2012007580A2

WO2012007580A2 - Assembly and method for detecting different optical wavelengths

Info

Publication number: WO2012007580A2
Application number: PCT/EP2011/062151
Authority: WO
Inventors: Michael Gieseler; Manfred Sorst
Original assignee: Zentrum Mikroelektronik Dresden Ag
Priority date: 2010-07-15
Filing date: 2011-07-15
Publication date: 2012-01-19
Also published as: WO2012007580A3

Abstract

The invention relates to an assembly and method for detecting different optical wavelengths. The aim of the invention is to provide an assembly and method which do not require any additional process steps during chip production and are thus more cost-effective in the production. The assembly achieves this aim by providing a first photodiode (1) having a first conversion characteristic with regard to optical wavelength and a second photodiode (2) having a conversion characteristic with regard to optical wavelength differing from the first conversion characteristic, both photodiodes being arranged directly adjacent to each other on a semiconductor chip (3).

Description

Arrangement and method for detecting different

Light Wavelengths The invention relates to an arrangement for detection

different wavelengths of light, preferably for

Determination of illuminance. The arrangement is preferably used for determining an illuminance which is adapted to the perception of the human eye (visible-eye characteristic).

The invention also relates to a method for detecting different wavelengths of light, preferably for

Determining an illuminance, in which in two different light wavelength ranges depending on a conversion of the detected wavelength intensity in each one

electrical size is done.

Semiconductor arrangements are known in the prior art in which on a semiconductor surface

Filter layers are applied, which only happen the visible wavelengths of light.

Furthermore, semiconductor devices are known, which use two similar photodiodes, wherein a photodiode of the radiation is exposed directly and a second is provided with an intermittent metal cover to prevent direct irradiation. This second photodiode therefore only receives charge carriers from the depth of the

Crystals, which are preferably generated by infrared light components (IR light components). An example of this is disclosed in the patent of TAOS US 6,596,981 Bl. From this it is known with respect to the circuit arrangement that

Transimpedance amplifier with subsequent voltage ADC and current ADC use find. TAOS further describes that one ADC in turn to implement the two

Channel information is used, which can be disadvantageous with respect to the so-called flicker noise.

Another example of such semiconductor arrangements is the semiconductor sensor ISL29015 from Intersil.

These prior art solutions have the disadvantage of requiring a cover or a special filter for at least one photodiode. These will

Usually generated in additional treatment steps in the chip production and thus cause a

Additional expenses within the manufacturing process and associated higher costs.

A procedural implementation of the detection

different wavelengths of light according to the state of

Technology at the companies TAOS and Intersil for the calculation of a so-called Visible Eye characteristic is the

Revelations show that in the basic equation

Lux = kl * blue + k2 * is assumed to be red, where kl and k2 are given variable in regions as a function of the IR component. However, TAOS in US 6,596,981 Bl describes detecting the spectral content of the incident light.

The invention is therefore based on the object, a

Provide arrangement and a method for detecting different wavelengths of light, which no additional

Need treatment steps in the chip production and thus are cheaper to manufacture.

According to the invention, this object is achieved by a first photodiode having a first light wavelength conversion characteristic and a second photodiode

Photodiode with a differing from the first light wavelength Umset zcharakteristik immediately are arranged side by side on a semiconductor chip.

According to the invention, two photodiodes are used which have different light wavelength conversion characteristics. For example, the first photodiode can preferably convert blue and green light components, while the second photodiode preferably converts red light components. Both photodiodes have one for infrared light

comparable wavelength conversion characteristic. The two photodiodes are right next to each other on one

Semiconductor chip arranged so that they are almost equal to a light illuminating the area of the two photodiodes

be irradiated at the same intensity.

In one embodiment of the invention it is provided that over the first and the second photodiode a common

optical window is arranged.

Over both photodiodes, a translucent window is arranged such that both photodiodes are irradiated with almost the same intensity. The translucent window has no filter properties. The remaining area of the

Chip surface must be opaque with a

Be provided coating or cover.

In a further embodiment of the invention, it is provided that the common optical window is arranged in a chip housing. If the semiconductor chip spent in a chip package, so the translucent window in one, the

Semiconductor chip covering area of the

Chip housing can be arranged and allows such a uniform irradiation of both photodiodes. According to the invention, the object is procedural ig This is achieved in that in a first method step, a difference, based on a first electrical quantity, between the two electrical quantities is formed, that in the second method step a linearization of this difference takes place within a wavelength range of the visible light, that a calculation of an average light wavelength L using the difference formed in the first process step takes place and that a convolution operation is performed using a quadratic form and is outputted as a result of the calculation as a value for illuminance.

The first and second photodiodes having different wavelength conversion characteristics generate first and second electrical quantities. This can

For example, be a voltage or a frequency, wherein the frequency can be generated from a voltage generated first. These electrical quantities are converted according to the illustrated method steps into an output value which corresponds to a illuminance,

for example, as a lux value.

Another possibility is to use a current ADC (current-to-analog-to-digital converter) around the

electrical quantity, which is a photocurrent, to convert into a digital output value corresponding to the current. For this purpose, starting with the first method step, the

Forming the difference obtained, subsequently calculated in a second step, a mean lambda and in the last step, a non-linear

Convolution operation performed. In one embodiment of the method it is provided that the electrical variable is a current. From the light wavelengths received by the photodiode a current is generated, which can subsequently be converted into a voltage. From this current or the voltage generated therefrom, a frequency corresponding to the voltage can be generated in a further conversion step.

According to the state of the art, a frequency or a digital output value is usually generated from the current.

In a further embodiment of the invention it is provided that the calculation according to the formula

k * blue

Illuminance = is performed.

(LL- _L ML-L _Z )

Here L describes a mean lambda, k a

Form factor from the conversion of the irradiation power into the LUX definition and LI, L2 the lower and upper zero point of the Human Eye characteristic (Visible-Eye characteristic).

The invention will be described below with reference to a

Embodiment will be explained in more detail. In the

accompanying drawings shows

1 is a representation of a wavelength intensity

Diagram for two inventively used

Photodiodes with different wavelengths

conversion characteristics,

Fig. 2 shows an inventive arrangement of two photodiodes in a chip layout and

Fig. 3 in the upper diagram representation of the results of a folding operation for the monochromatic light shown in the lower diagram (continuous

Trace / red curve) with the well-known Human Eye

Curve .

According to the invention, use is made of two photodiodes 1 and 2 with different wavelength conversion characteristics. In this case, a first photodiode 1 preferably converts blue and green light components, as shown in FIG. 1 as a continuous line trace. A second photodiode 2 preferably converts red light components, as shown in FIG. 1 as a dashed-dotted line. Both

Photodiodes 1 and 2 have, for example, a for

Infrared light (IR) comparable transmission characteristics.

The first and the second photodiode 1 and 2 are arranged on the semiconductor chip 3 with a very small distance from each other, so that both are irradiated below a common, arranged over two photodiodes 1 and 2, optical window of the incident light in the same intensity. The optical window, which is not shown in the figure 2, can also in a housing of the

Semiconductor chips 3 may be arranged.

Each photodiode generates its own photocurrent. These are converted separately into a digital signal.

This digital signal may be, for example, a frequency signal at a voltage-frequency conversion or the output code of an ADC.

These two digital signals are converted by means of the method described below into an intensity value which corresponds to the intensity perceived by the human eye in sunlight.

FIG. 2 shows an exemplary floorplanning of an entire chip 3 which, in addition to a sensor structure which also contains the two photodiodes 1 and 2, contains further components. In this

Representation is the first photodiode 1 with "blue" and the second photodiode 2, the square marked "IR". The arranged next to the photodiodes rectangles are the

associated AD converter. Next to it is the structure marked "Dark" for capturing the

Dark currents. This structure includes two

Compensation sensors, just in case the

Dark currents for "blue" and "IR" are the same size, only one compensation sensor on the chip 3 is required.

According to the invention, an integrable solution for

Determining the visible eye characteristic of preferably a blue-sensitive first 1 and a red-sensitive second photodiode 2 and a circuit arrangement for direct conversion of the photocurrents by means of a voltage-frequency converter used.

According to the prior art is using a

complicated nonlinear formula, which on one

external computer is implemented, for example, a characteristic of the human eye modeled.

According to the invention, the intensity in several

Determined process steps, which are listed below:

a) Calculation of a "blue" characteristic

relative difference (blue-red) / blue. "Blue" and "red" indicate the converted photocurrents, b) linearization of this related quantity in the range of visible light, ie in the wavelength range from 450 nm to 670 nm. c) calculation of a mean wavelength of light L below

Use of the referred / normalized determined under a.)

Difference. d) Simplified convolution operation using a square shape

k * blue

Illuminance = (L-L L-Lz)

At the same time, the zero crossings of the denominator polynomial become

for example, chosen so that the convolution operation has its maximum on the average of the Visible Eye spectrum (550nm - 555nm). The filter bandwidth is symmetrical about this mean and is 170 nm. Thus, the zeroes Li = 465nm and L2 = 635nm. The factor k is chip related

empirically so to determine, such that at maximum

Intensity, for example, using a 16-bit resolution, a maximum intensity value is displayed.

This can be in the chip architecture an electronic

Component that is programmed only once at the user (OTP register), be provided.

In the upper diagram of Figure 3, the result of a

Convolution for the one shown in the lower diagram

monochromatic light (continuous line / red curve) compared with the known human eye curve (dash-dot line / green). Despite the simple method, it shows a very good agreement in many areas with regard to the ideal human eye characteristic.

The determined mean wavelength L can be used both as an intermediate result of the method and for outputting the average color value of a light signal. Reference sign list

first photodiode

second photodiode

Semiconductor chip

Claims

claims

1. Arrangement for detecting different

Light wavelengths, preferably for determining an illuminance, characterized in that a first photodiode (1) with a first

Light wavelength conversion characteristic and a second photodiode (2) with a from the first

distinctive light wavelength Umset zcharakteri stik are arranged directly adjacent to each other on a semiconductor chip.

2. A semiconductor device according to claim 1, characterized

in that a common optical window is arranged above the first and the second photodiode (1, 2).

3. A semiconductor device according to claim 1 or 2, characterized in that the common optical window is arranged in a chip housing.

4. Method for detecting different

Wavelengths of light, preferably for determining an illuminance, in which in each of two different light wavelength ranges a conversion of the

detected wavelength intensity in each one

electrical size occurs, thereby

characterized in that in a first

Step, a relation to a first electrical magnitude difference between the two electrical variables is formed, that in the second process step a linearization of this difference

within a wavelength range of the visible light, a calculation of a mean wavelength of light L using the first

Process step formed difference and that a convolution operation using a

quadratic shape and that is output as a result of the calculation as a value for illuminance.

Method according to claim 4, characterized

characterized in that the electrical quantity is a current.

A method according to claim 4 or 5, characterized

characterized in that the calculation according to the

f ^ bl cm,

Formula Illuminance = _(L _ _{L) H, (} LL ₎ ^{by <} ? ^ef is ührt.