CS200684B1 - Pyroelectrical sensing element - Google Patents

Description

(54) Pyroelectric Address

The invention relates to a pyroelectric headquarters, in particular intended for epectronic applications in the infrared field.

Problems of detecting infrared radiation of low power are solved either by quantum detectors or by selective detection, which is a significant disadvantage, that it is desirable to have their headquarters cooled or non-occlusal heat detectors in the sundown of 3 nm wavelengths of radiation. whose disadvantage is the non-response rate of the electrical response as compared to the quantum detectors. The best heat detector used is the Goley cell, Saeto used in the most demanding spectrometric measurements. The most specific disadvantages are the relatively high acquisition costs, limited service life and relatively high power consumption for special applications.

These disadvantages do not have, or in principle do not have to be, pyroelectric detectors which, while maintaining high sensitivity e at room temperature, have a faster response by several orders of magnitude. So far, the technology for preparing the Detectors for these detectors has not been so high that the pyroelectric detectors are competitive.

The basic idea of the arrangement of the pyroelectric headquarters is as follows: The seat is composed of a pyroelectric material detector with homogeneous polarization, provided with electrodes perpendicular to the polarization vector. When the temperature of the aet is reduced, spontaneous charge α is formed on their electrodes. whose size is given

200 004

Ρ * Δ *.

where ρ is the pyroelectric coefficient of the pyroelectric used e A is the area of the electrodes.

Current (short-circuited) sensor electrodes is

I, Δϋ / Δ * · where δ * 3® δ ·· ονγ interval in which ee realizes charge charge from \ Q · Miao this signal current X * sensor has iu current I _n , which co-determines threshold value P _R radiant power called NEP (Nolee Equalvalent Power). Mlniaallzovat P _n • zneaoná exlaellzovet poaěr l _g / podainky X _n for the incident radiant power at the own sensor remains constant. This means aaxlaallizing the abeorpee coefficient of the sensor, alnlaalizing its thickness and active area, thermal conductivity of the sensor and its surroundings, and choosing the appropriate and aaterial kenetantaai. Of these requirements is to ensure the largest probláaea · e neaelektlvnl simultaneously high absorption in all infrared · art and minimize thermal výačnu between the sensor and okolla already component is proportional to the thermal power X _n šuaováho given as

I _n - <* 0 ♦ * TZ ♦ * TV * 4 ») ^V2 · ^w ·

1 ₃ is the thermal (Oohnaon) ionic current and 1 _τζ , ίγγ, l _T p are the temperature dual currents corresponding to the exchange of heat and the ambient sensor, whether it is radiation, watering, resp. proudinla.

The size of component ij is dependent on the material constants; i _TZ is a coaponent of the Ideal Detector principle.

In the prior art pyroelectric sensor arrangements, the sensor plate itself is mounted either on a support or ring, the size of the heat exchange being determined by the sensor and the surrounding area, and also by the size of the co-component ijy in the previous paragraph.

To minimize ionic current X _R minimizing co-component ijy α 1γ _ρ is an object of the present invention to provide a pyroelectric plate of its own sensor. It is mounted in the free space of a hermetically sealed housing at the level of the pyroelectric plate relative to the eeb and cross-circuited by their end, they are conductively connected to the conductors. The sensor housing may be heraetically sealed to the inner surface of the sensor housing and may be fixed in a solid state. Spectral transmission windows may be formed by a flexible membrane. The pyroelectric spacer may be formed from a bleached pyroelectric polyaer.

An exemplary embodiment of a pyroelectric sensor according to the invention is shown in the accompanying drawing, in which Fig. 1 shows an axial section of the pyroelectric sensor. In Fig. 2, the pyreelectric sensor is shown in section plane A-A of Fig. 1.

The pyroelectric plate 6 is provided with water-borne and absorbent layers 2, 3 of which

200 004 each is fixed by a droplet of conductive sealant 6, 7 to the respective conductor 4, 5.

The conductors 4, 5 are designed so. that the thermal conductivity of each is less than

1.3. 10 ^"2 YK ^{1" _1} l S and the LOP is between 0.1 ^ / um ^2-8 .mu.m ^second The conductors 4, 5 are cross-linked and their ends are welded and mechanically fixed by the conductive mastic capsule 101, 102, 103, 104 to their respective conductors 81, 82, 83, 84, the grommet 91, 92, 93, 94 the base plates 11. sensor housings. The sensor housing base plate 11 provided with a spectrally permeable window 14 hermetically sealed in the epoxy 163. is covered by a wolf 12 hermetically sealed in the joint 162. The cap 12 is provided with a spectrally permeable window 13 hermetically sealed in the joint 151. 152. 153. 154 and moisture sorption properties.

The modulated radiation in the spectral region of the transmittance of the window 13 impinging on the conductive absorber layer 2 induces temperature modulation of the pyroelectric plate 1 and hence the corresponding alternating signal on the conductive absorber layers 2, 3, which function as electrodes. This signal is passed through conductors 81, 82, 83, 84 to an evaluation circuit (not shown), which may advantageously be placed in an integrated form directly in the sensor housing consisting of a base plate 11 and a wolf 12. In some application cases it may be advantageous to use wolf pyroelectric The wires are fused in a row next to the eebe, with one wired conductor being equal to the wafers and the other wires of each wiring being individually led.

If the pyroelectric sensor according to the invention is used as a calibration radial, a calibrated radiation source is ground to the window 14, the radiation of which is modulated at the same frequency as the radiation detected but the opposite phase.

The pyroelectric sensor according to the invention can also be used for highly demanding applications in spectrometry, where in addition to the high threshold sensitivity requirement, there is a non-selectively wide response requirement in the far infrared range. The problem of spectrally independent absorption of the sensor itself is the absorption of the material of the sensor itself, and in the case of insufficiency an auxiliary abeorption layer is used in thermal contact with the sensor itself. For the spectroscopic purposes in the infrared wavelength range, only the metal abeorption layers can be used, which, even in the far infrared region, provide non-electromagnetic absorption with negligible thermal inertia. The application of an optimum thickness of this layer is individually dependent on the type of metal or the elite of the metal and is associated with considerable optimization technological difficulties. The relative disadvantage of the metal absorbing layer is its high odrazivoet e negative consequences not the size of the signal current I _e. This drawback can be remedied by using special blades with negligible reflectors. However, these blacks are not applicable in the far infrared range. Ooeud has no known sensor arrangement which, while maintaining a peak value of P _{n of the} order of 1θ "^^ / Ηζ ^ ^2, is also applicable in the far infrared range.

Both of the aforementioned sailplanes have a pyroelectric sensor in the arrangement according to the invention, wherein, for example, a pyroelectric plate 1 cut from a crystal of trglycine sulfate in a direction perpendicular to its polar axis and ground to a thickness of about 10 µm is provided with conductive

200 804 absorbent layers having a composition of, for example, 80% Ni and 20% Cr and a thickness of 10 ² / m.

While the prior art pyroelectric sensors are suitable for near and medium infrared radiation data, with their peak, laboratory-achieved NEP being reported as P _R 10 ^ ^ / Hz ^ ² , the pyroelectric sensor thus prepared is also suitable for remote infrared detection. , in addition, the order of the same NEP. At the same time, it meets the prerequisites for easier availability, as would be the case with foreign products.

Another possible use of the pyroolectric sensor according to the invention is the detection of the mass wave of the surrounding environment, especially in the aubactuatle of the field, and this is the case if the window 13 or the window 14 are formed from a resilient partition, e.g.

The pyroelectric sensor according to the invention can advantageously be used in infrared spectrometry, in particular in the far infrared range, as a calibration radioaotr, in an infrared radar in cooperation with a laser, e.g. COg and the like.

Claims (4)

P fi E D Μ £ T INVENTION A pyroelectric sensor comprising a pyroelectric plate provided with conductive and absorbent layers of conductive bonded and lead wires and housed in a housing provided with at least one transparent window positioned opposite the pyroelectric plate, characterized in that the pyroelectric plate (1) of the housing itself is mounted in the free space pads (11) and wolf (12) by means of lead wires (4,5) forming a carrier and pyroelectric wafers (1), wherein the lead wires (4,5) are at the level of the pyroelectric wipe (1) extremely crossed with each other conductively connected to through conductors (81,82,83,84). 2. A pyroelectric sensor according to claim 1, characterized in that the sensor housing is sealed in a sealed manner and a solid state material (6) is attached to the inner surface of the sensor housing. 3. Pyroelectric sensor according to claim 1, characterized in that the spectral transmissive windows (13, 14) are formed by a flexible membrane. 4. Pyroelectric sensor according to claim 1, characterized in that the pyroelectric plate (1) is formed from a pyroelectric polymer film.