CN102980585A - Analog-type sun sensor and method - Google Patents

Abstract

The invention discloses an analog-type sun sensor and a method. The sun sensor comprises a light introducing device, a light position sensor and a calculating device, wherein the light introducing device is used for receiving sunlight and introducing the sunlight into a light-sensing surface of the light position sensor through an incidence hole; the light position sensor is used for generating corresponding signals of four paths of currents according to the position of a solar facula on the light-sensing surface; and the calculating device is used for calculating an incidence angle of the sunlight according to the signals of the four paths of currents. According to the method, the incidence angle of the sunlight can be obtained in real time through calculation according to differences of obtained signals of the four paths of currents generated on the light position sensor during the sunlight incidence, the testing calibration steps are simple, and the accuracy is high.

Description

A kind of analog sun sensor and method

Technical field

The present invention relates to the quick field of satellite technology and the sun, especially, relate to a kind of analog sun sensor and method.

Background technology

Sun sensor is indispensable photoelectricity attitude sensor on the satellite, so all satellites all are equipped with sun sensor.It is the attitude of determining satellite by the position of measuring the relative satellite body coordinate system of the sun, and sun sensor is except can also be used to the instrument of protecting sensitivity very high the attitude information for satellite provides, such as star sensor, imaging load etc.

Sun sensor is just towards miniaturization, high precision, high stability, low-power consumption, long-life future development at present.Gradually to the development of the planar array detectors such as CCD, APS CMOS, this will promote Highgrade integration and the modularization of sun sensor to its detector element by photoelectric cell.The formation of sun sensor mainly comprises three aspects: optical head, Sensor section and signal processing.Optical head can adopt the modes such as slit, aperture, lens, prism.Sensor can adopt photoelectric cell cmos device, code-disc, grating, photodiode, line array CCD, area array CCD, the devices such as APS CMOS, SMART.Signal processing can adopt separate electronic components and parts, single-chip microcomputer, programmable logic device (PLD) etc.By the difference of working method, it is several sun sensor can be divided into 01 formula sun sensor, analog sun sensor and digital sun sensor.

(1) 01 formula sun sensor is called again the discoverable type sun sensor, as long as there is the sun just to produce output signal, but in general in order to reach purposes such as removing noise, interference, need to generally get 50%～80% of solar peak value signal for sensor arranges a decision threshold, only have and when sun signal surpasses this threshold value, just think and found the sun, thereby this sun sensor precision is not high.

(2) analog sun sensor is also referred to as the cosine detecting device and adopts photovoltaic devices as light activated element more, therefore the intensity of its output signal electric current is relevant with solar incident angle when sun signal shines thereon, can utilize the size of output current to judge the incident angle of sunshine.Satellite mainly relies on the bigness scale amount that this sensor is finished attitude at present.But this sun sensor precision based on cell piece is not high, can not satisfy the requirement of high-precision attitude control system.

(3) digital sun sensor mainly contains two kinds of CCD and APS CMOS, and its detector element has linear array and face battle array two classes.The linear array digital sun sensor calculates the incident angle of sunshine by calculating the deviation of sunray relative center on detector; Face battle array digital sun sensor then by calculating the center-of-mass coordinate position of solar facula on the face battle array with respect to the deviation of optical centre position, calculates the incident angle of sunshine.But this digital sun sensor treatment circuit based on CCD/CMOS is complicated, and reliability is low.

From present both at home and abroad typical sun sensor product, analog sun sensor is compared with digital sun sensor, the advantage such as have that principle simply is easy to realize and field angle is large.But the measuring accuracy of analog sensor is lower than digital sun sensor, is difficult to satisfy the high-precision requirement that satellite attitude control system improves day by day; In addition, analog sun sensor is subject to the interference of other celestial body easily owing to mostly adopt photoelectric cell as Sensitive Apparatus, and for example the reflected light of the earth all can cause the interference to analog sun sensor.And digital sun sensor can overcome this interference, and measuring accuracy will be higher than analog sun sensor.

In summary, traditional analog formula sun sensor sensor precision is not high enough, the digital sun sensor circuit is complicated, volume and weight is large and precision is low, can not satisfy the requirement of microsatellite.

Summary of the invention

The object of the invention is to provide analog sun sensor and the method that a kind of volume is little, lightweight, low in energy consumption and precision is high, to solve traditional sun sensor circuit complexity, volume and weight greatly and the not high technical matters of precision.

For achieving the above object, the invention provides a kind of analog sun sensor, comprising:

The light introducing device is used for receiving sunshine, and is incorporated into described sunshine on the light-sensitive surface of optical position sensor by entering perforation;

Described optical position sensor is used for producing four road corresponding current signals according to the position of the solar facula on the described light-sensitive surface;

Calculation element is used for the incident angle according to described four road current signals calculating sunshine.

Further improvement as analog sun sensor of the present invention:

Preferably, described sun sensor also comprises:

Signal conditioning circuit is transferred to the AD sample circuit after described four road current signals being carried out filtering and amplification and be converted to four road corresponding voltage signals;

Described AD sample circuit is used for described four road voltage signals are sampled, and the sampled result of correspondence is transferred to described calculation element;

Described calculation element calculates the incident angle of sunshine according to sampled result corresponding to described four road current signals.

Preferably, described light introducing device is the radiation resistant glass that has covered mask layer, has offered the described perforation that enters on the described mask layer; Described optical position sensor is the PSD sensor.

Preferably, the distance B of the light-sensitive surface of described optical position sensor and described mask layer satisfies:

Wherein, described L is the diameter of the light-sensitive surface of described optical position sensor, and described θ is the incident angle of described sunshine.

Preferably, the incidence angle θ of described sunshine≤60 degree, the distance B of the light-sensitive surface of described mask layer and described optical position sensor 〉=2800 μ m; The described diameter l=200 μ m that enters perforation, the thickness of described mask layer is 100nm.

Preferably, described radiation resistant glass is provided with arrowband flow-through filter layer film system, and the logical scope of the band of described arrowband flow-through filter layer film system is the 760nm wave band.

As a total technical conceive, the present invention also provides a kind of analog sun sensitive method, may further comprise the steps:

S1: receive sunshine by the light introducing device, and be incorporated into described sunshine on the light-sensitive surface of optical position sensor by entering perforation;

S2: four road current signals that produce correspondence by described optical position sensor according to the position of the solar facula on the light-sensitive surface;

S5: calculate according to described four road current signals, obtain the incident direction of sunshine.

As further improvements in methods of the present invention:

Preferably, before the described step S5, described method also comprises:

S3: four road voltage signals that described four road current signals amplified and are converted to correspondence;

S4: described four road voltage signals are sampled, obtain corresponding sampled result;

In described step S5, described method is specially: calculate according to sampled result corresponding to described four road current signals, obtain the incident direction of sunshine.

Preferably, described four sampled result corresponding to current signal are respectively U _X1, U _X2, U _Y1And U _Y2Among the described step S5, the computing formula of the incident direction of described sunshine is as follows:

θ _X＝arctanX/D，

θ _Y＝arctanY/D，

Wherein, described θ _XAngle for sunshine and X-axis; Described θ _YAngle for sunshine and Y-axis; Described D is the distance of the light-sensitive surface of the mask layer of described light introducing device and optical position sensor;

And, described $X=\frac{L}{2}\left(\frac{(U_{\mathrm{<figure-callout\; id="2"\; label="X"\; filenames="HDA00002675459500012.png"\; state="\{\{state\}\}">X</figure-callout>}2}+U_{Y1})-(U_{X1}+U_{Y2})}{(U_{\mathrm{<figure-callout\; id="2"\; label="X"\; filenames="HDA00002675459500012.png"\; state="\{\{state\}\}">X</figure-callout>}2}+U_{Y1})+(U_{X1}+U_{Y2})}\right),$

Described $Y=\frac{L}{2}\left(\frac{(U_{\mathrm{<figure-callout\; id="2"\; label="X"\; filenames="HDA00002675459500012.png"\; state="\{\{state\}\}">X</figure-callout>}2}+U_{Y2})-(U_{X1}+U_{Y1})}{(U_{\mathrm{<figure-callout\; id="2"\; label="X"\; filenames="HDA00002675459500012.png"\; state="\{\{state\}\}">X</figure-callout>}2}+U_{Y2})+(U_{X1}+U_{Y1})}\right),$

Wherein, described L is the diameter of the light-sensitive surface of optical position sensor.

Preferably, described optical position sensor is the PSD sensor, the distance B of the light-sensitive surface of described mask layer and described optical position sensor=2800 μ m.

The present invention has following beneficial effect:

1, analog sun sensor of the present invention is incident on the optical position sensor so that optical position sensor produces four road current signals by sunshine, and calculation element is processed and calculated four road current signals, can realize measuring in real time the incident angle of sunshine.It is simple in structure, and is low in energy consumption, and small volume, cost are lower.

2, analog sun sensitive method of the present invention, optical position sensor produces four road current signals when obtaining sunshine incident, and calculate the incident angle that can obtain in real time sunshine according to this four road current signal, the test calibration step of the method is simple, and precision is higher.

Except purpose described above, feature and advantage, the present invention also has other purpose, feature and advantage.The below is with reference to figure, and the present invention is further detailed explanation.

Description of drawings

The accompanying drawing that consists of the application's a part is used to provide a further understanding of the present invention, and illustrative examples of the present invention and explanation thereof are used for explaining the present invention, do not consist of improper restriction of the present invention.In the accompanying drawings:

Fig. 1 is the composition structural representation of the analog sun sensor of the preferred embodiment of the present invention 1;

Fig. 2 is that the sunshine of the preferred embodiment of the present invention 1 incides principle schematic on the optical position sensor by the light introducing device; And

Fig. 3 is the schematic flow sheet of the analog sun sensitive method of the preferred embodiment of the present invention 2.

Marginal data:

1, light introducing device; 2, mask layer; 3, radiation resistant glass; 4, enter perforation; 5, optical position sensor.

Embodiment

Below in conjunction with accompanying drawing embodiments of the invention are elaborated, but the multitude of different ways that the present invention can be defined by the claims and cover is implemented.

Embodiment 1:

Referring to Fig. 1, analog sun sensor of the present invention comprises following three parts at least:

1, the light introducing device 1, is used for sunshine is incorporated into by entering perforation 4 light-sensitive surface of optical position sensor 5.

In the present embodiment, light introducing device 1 has been offered perforation 4 for having covered the radiation resistant glass 3 of mask layer 2 on the mask layer 2.Also be provided with arrowband flow-through filter layer film system on the radiation resistant glass 3, the logical scope of the band of arrowband flow-through filter layer film system is preferably 760nm.The silica-based optical filter of the preferred employing of arrowband flow-through filter layer film system of present embodiment, its optical filtering tunic system is by silicon and the alternately laminated multilayer dielectric film system that forms of silicon dioxide.There is high transmittance in arrowband flow-through filter layer film system to 760nm left and right sides narrow band light; By the optical filtering mask design the quick spectral range of the sun is limited to the 760nm wave band and can reduces earth reflected light to the energy barycenter impact of sun sensor, improve precision.

2, optical position sensor 5, are used for producing four road corresponding current signals according to the position of the solar facula on the light-sensitive surface.

In the present embodiment, optical position sensor 5 is PSD(Position Sensitive Detector) sensor.The principle of work of analog sun sensor sensor is similar to corona, and the PSD installation of sensors is on the projecting plane that is parallel to perforation 4.Under the irradiation of the parallel incident light with different incidence angles (angle between the normal of sunshine and PSD sensor), sunshine is projected as solar facula (speck) by the perforation 4 that enters on the mask eyeglass on the PSD sensor, the geometric center of solar facula is relevant with solar angle, change along with incident angle, cause the change of facula position on the sensor, thereby cause the variation of current output sensor signal.

The field angle of analog sun sensor is mainly determined by optical system parameter.Optical system must guarantee in field range sunshine by on the light introducing device 1 enter the solar facula projection of perforation 4 on optical position sensor 5 can be collected.Provided the pinhole imaging system synoptic diagram among Fig. 2.Wherein, l is the diameter into perforation 4, and L is the diameter of the light-sensitive surface of optical position sensor 5, is that aperture is in the full-size of the photosensitive region imaging of position transducer.During actual design, the distance B of the light-sensitive surface of optical position sensor 5 and mask layer 2 satisfies:

Wherein, L is the diameter of the light-sensitive surface of optical position sensor 5, and θ is the incident angle of sunshine.And, when θ is 60 °, satisfy the condition of L 〉=l, then sunshine can be collected by the projection that enters the solar facula of perforation 4 on optical position sensor 5 on the light introducing device 1.During practical application, the incidence angle θ of sunshine≤60 degree, the distance B of the light-sensitive surface of mask layer 2 and optical position sensor 5 〉=2800 μ m.In the present embodiment, θ preferably is set to 60 °, and mask layer 2 preferably is set to D=2800 μ m with the distance of the light-sensitive surface of optical position sensor 5; The diameter that enters perforation 4 preferably is set to l=200 μ m; The thickness of mask layer 2 preferably is set to 100nm.

3, calculation element is used for the incident angle according to four road current signals calculating sunshine.In the practical application, calculation element can share computer realization with other equipment on the satellite.

Above-mentioned analog sun sensor can be incident on the optical position sensor so that optical position sensor produces four road current signals by sunshine, and calculation element is processed and calculated four road current signals, can realize measuring in real time the incident angle of sunshine.It is simple in structure, and is low in energy consumption, and small volume, cost are lower.

Because four road current signals fainter (μ A level) that optical position sensor 5 produces are unfavorable for sampling, when used on the historical facts or anecdotes border, analog sun sensor of the present invention also can comprise following two parts:

4, signal conditioning circuit, be used for to four road current signals amplify and be converted to four road corresponding voltage signals after be transferred to the AD sample circuit.

5, AD sample circuit is used for four road voltage signals are sampled, and the sampled result of correspondence is transferred to calculation element.So that the result that calculation element will be sampled calculates, to obtain the incident angle of sunshine.

The PSD sensor is as the high impedance sensor, after its base stage is biased voltage, if irradiation is arranged on light-sensitive surface, light-sensitive surface is exported four tunnel very little current signals, when therefore carrying out voltage transitions and amplification, operational amplifier in the I/V conversion circuit of signal conditioning circuit not only will have lower bias current characteristic, and less input noise voltage and drift voltage will be arranged.Be to guarantee the resolution precision of PSD sensor, need the in addition filtering of the power supply that drives PSD sensor and operational amplifier, so signal conditioning circuit mainly comprises two parts, filtering circuit and amplifying circuit.Wherein, amplifying circuit mainly realizes by high-accuracy amplifier, and this circuit will be by the two-stage negative feedback, after the current signal of the simulation that the PSD sensor is produced amplifies conditioning, signal is sent to carries out AD in the AD sample circuit and sample.Current signal is converted to voltage signal, except being convenient to reach jamproof purpose the AD sample circuit samples.

During actual installation, have square form on the form plate of simulated solar sensor, optical system and the electronic system of sun sensor has been installed in its circuit board box.Light introducing device 1 is connected by screw and is fixed on the pressing plate, and at the upper and lower of light introducing device 1 pad is set respectively, and is inconsistent to prevent with the structure coefficient of thermal expansion and contraction.Signal conditioning circuit is connected with connector with mode to the external application bonding wire and takes corresponding shielding measure, then is fixed in the circuit board box of sun sensor.The assembly structure of each assembly of sun sensor will guarantee the realization of equipment all technical, also will guarantee simple and reliable for structurely, satisfies the requirement of space flight mechanics environment (vibration, impact and acceleration) and environment temperature.Require light introducing device 1 to remain unchanged in the error allowed band to the distance B of the light-sensitive surface of optical position sensor, light introducing device 1 can not rotation displacement, can not be because of vibration, impact, material the expand with heat and contract with cold situations such as characteristic and fragmentation, and the perforation 4 that enters on the mask layer 2 can be by volatile substance institute contamination and plugging.Be the convenient uncertain factor of when analog sun sensor is tested and install, not introducing, generally PSD sensor, light introducing device 1, housing etc. are connected firmly together, and then with the satellite frame installation together, so that can not produce relative displacement between PSD sensor, light introducing device 1, housing and the satellite, in order to set up unified, stable coordinate system.

To sum up, analog sun sensor of the present invention, sunshine is incorporated on the sensitive surface of optical position sensor 5 by light introducing device 1, so that optical position sensor 5 produces corresponding current signal, and by signal conditioning circuit, AD sample circuit and calculation element these current signals are optimized and process and to calculate, can realize measuring in real time the incident angle of sunshine.It is simple in structure, and is low in energy consumption, and small volume, cost are lower.

Embodiment 2:

Referring to Fig. 3, analog sun sensitive method of the present invention may further comprise the steps:

S1: receive sunshine by light introducing device 1, and sunshine is incorporated on the light-sensitive surface of optical position sensor 5 by entering perforation 4.

S2: four road current signals that produce correspondence by optical position sensor 5 according to the position of the solar facula on the light-sensitive surface.In the present embodiment, optical position sensor 5 adopts the PSD sensor, and the current signal of its output is the current signal of four very little (μ A levels).

S3: the voltage signal that four road current signals is amplified and are converted to correspondence.

S4: four road voltage signals are sampled, obtain corresponding sampled result.In the present embodiment, four current signals are respectively I _X1, I _X2, I _Y1And I _Y2The sampled result of corresponding voltage signal can be used U _X1, U _X2, U _Y1And U _Y2Expression, and the enlargement factor of four road current signals when converting corresponding voltage signal to is identical.

S5: calculate according to the sampled result that four road current signals are corresponding, obtain the incident direction of sunshine.

In the present embodiment, the computing formula of the incident direction of sunshine is as follows:

θ _X＝arctanX/D，

θ _Y＝arctanY/D，

Wherein, θ _XAngle for sunshine and X-axis; θ _YAngle for sunshine and Y-axis.As shown in Figure 2, D is the distance (preferred D=2800 μ m) of mask layer 2 with the light-sensitive surface of optical position sensor 5 of light introducing device 1.

In the following formula, X-axis is: $X=\frac{L}{2}\left(\frac{({\mathrm{<figure-callout\; id="2"\; label="U\; X"\; filenames="HDA00002675459500012.png"\; state="\{\{state\}\}">U</figure-callout>}}_X+U_{Y1})-(U_{X1}+U_{Y2})}{({\mathrm{<figure-callout\; id="2"\; label="U\; X"\; filenames="HDA00002675459500012.png"\; state="\{\{state\}\}">U</figure-callout>}}_X+U_{Y1})+(U_{X1}+U_{Y2})}\right),$

Y-axis is: $Y=\frac{L}{2}\left(\frac{({\mathrm{<figure-callout\; id="2"\; label="U\; X"\; filenames="HDA00002675459500012.png"\; state="\{\{state\}\}">U</figure-callout>}}_X+U_{Y2})-(U_{X1}+U_{Y1})}{({\mathrm{<figure-callout\; id="2"\; label="U\; X"\; filenames="HDA00002675459500012.png"\; state="\{\{state\}\}">U</figure-callout>}}_X+U_{Y2})+(U_{X1}+U_{Y1})}\right),$

During practical application, the enlargement factor when four road current signals convert corresponding voltage signal to is identical, so X-axis and Y-axis also can adopt following formula to carry out approximate treatment:

The position of X-axis can be calculated as: $X=\frac{L}{2}\left(\frac{({\mathrm{<figure-callout\; id="2"\; label="U\; X"\; filenames="HDA00002675459500012.png"\; state="\{\{state\}\}">U</figure-callout>}}_X+U_{Y1})-(U_{X1}+U_{Y2})}{({\mathrm{<figure-callout\; id="2"\; label="U\; X"\; filenames="HDA00002675459500012.png"\; state="\{\{state\}\}">U</figure-callout>}}_X+U_{Y1})+(U_{X1}+U_{Y2})}\right),$

The position of Y-axis can be calculated as: $Y=\frac{L}{2}\left(\frac{({\mathrm{<figure-callout\; id="2"\; label="U\; X"\; filenames="HDA00002675459500012.png"\; state="\{\{state\}\}">U</figure-callout>}}_X+U_{Y2})-(U_{X1}+U_{Y1})}{({\mathrm{<figure-callout\; id="2"\; label="U\; X"\; filenames="HDA00002675459500012.png"\; state="\{\{state\}\}">U</figure-callout>}}_X+U_{Y2})+(U_{X1}+U_{Y1})}\right),$

Wherein L is the diameter of the light-sensitive surface of optical position sensor 5.During actual design, the distance B of the light-sensitive surface of optical position sensor 5 and mask layer 2 satisfies:

Wherein, θ is the incident angle of sunshine.

To sum up, analog sun sensitive method of the present invention, optical position sensor 5 generation current signals when obtaining sunshine incident, and after these current signals are carried out filtering and the anti-interference process such as amplification, conversion, sample and calculate the incident angle that can obtain in real time sunshine, the test calibration step of the method is simple, and precision is high.

Be the preferred embodiments of the present invention only below, be not limited to the present invention, for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (10)

1. an analog sun sensor is characterized in that, comprising:

Light introducing device (1) is used for receiving sunshine, and described sunshine is incorporated on the light-sensitive surface of optical position sensor (5) by entering perforation (4);

Described optical position sensor (5) is used for producing four road corresponding current signals according to the position of the solar facula on the described light-sensitive surface;

Calculation element is used for the incident angle according to described four road current signals calculating sunshine.

2. analog sun sensor according to claim 1 is characterized in that, described sun sensor also comprises:

Signal conditioning circuit is transferred to the AD sample circuit after described four road current signals being carried out filtering and amplification and be converted to four road corresponding voltage signals;

Described AD sample circuit is used for described four road voltage signals are sampled, and the sampled result of correspondence is transferred to described calculation element;

Described calculation element calculates the incident angle of sunshine according to sampled result corresponding to described four road current signals.

3. analog sun sensor according to claim 2 is characterized in that,

Described light introducing device (1) has been for having covered the radiation resistant glass (3) of mask layer (2), offered the described perforation (4) that enters on the described mask layer (2);

Described optical position sensor (5) is the PSD sensor.

4. analog sun sensor according to claim 3 is characterized in that,

The distance B of the light-sensitive surface of described optical position sensor (5) and described mask layer (2) satisfies:

Wherein, described L is the diameter of the light-sensitive surface of described optical position sensor (5), and described θ is the incident angle of described sunshine.

5. analog sun sensor according to claim 4 is characterized in that,

The incidence angle θ of described sunshine≤60 degree, the distance B of the light-sensitive surface of described mask layer (2) and described optical position sensor (5) 〉=2800 μ m; The described diameter l=200 μ m that enters perforation (4), the thickness of described mask layer (2) is 100nm.

6. each described analog sun sensor in 5 according to claim 1 is characterized in that,

Described radiation resistant glass (3) is provided with arrowband flow-through filter layer film system, and the logical scope of the band of described arrowband flow-through filter layer film system is the 760nm wave band.

7. an analog sun sensitive method is characterized in that, may further comprise the steps:

S1: receive sunshine by light introducing device (1), and described sunshine is incorporated on the light-sensitive surface of optical position sensor (5) by entering perforation (4);

S2: four road current signals that produce correspondence by described optical position sensor (5) according to the position of the solar facula on the light-sensitive surface;

S5: calculate according to described four road current signals, obtain the incident direction of sunshine.

8. analog sun sensitive method according to claim 6 is characterized in that, before the described step S5, described method also comprises:

S3: four road voltage signals that described four road current signals amplified and are converted to correspondence;

S4: described four road voltage signals are sampled, obtain corresponding sampled result;

In described step S5, described method is specially:

Calculate according to sampled result corresponding to described four road current signals, obtain the incident direction of sunshine.

9. analog sun sensitive method according to claim 8 is characterized in that, described four sampled result corresponding to current signal are respectively U _X1, U _X2, U _Y1And U _Y2Among the described step S5, the computing formula of the incident direction of described sunshine is as follows:

θ _X＝arctanX/D，

θ _Y＝arctanY/D，

Wherein, described θ _XAngle for sunshine and X-axis; Described θ _YAngle for sunshine and Y-axis; Described D is the distance of mask layer (2) with the light-sensitive surface of optical position sensor (5) of described light introducing device (1);

And, described $X=\frac{L}{2}\left(\frac{(U_{X2}+U_{Y1})-(U_{X1}+U_{Y2})}{(U_{X2}+U_{Y1})+(U_{X1}+U_{Y2})}\right),$

Described $Y=\frac{L}{2}\left(\frac{(U_{X2}+U_{Y2})-(U_{X1}+U_{Y1})}{(U_{X2}+U_{Y2})+(U_{X1}+U_{Y1})}\right),$

Wherein, described L is the diameter of the light-sensitive surface of optical position sensor (5).

10. each described analog sun sensitive method in 9 according to claim 7, it is characterized in that, described optical position sensor (5) is the PSD sensor, the distance B of the light-sensitive surface of described mask layer (2) and described optical position sensor (5)=2800 μ m.

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