DE102007021677A1 - Combustible gas e.g. methane, absorption-spectroscopic verification method, involves adjusting charge coupled device by automated adjustment system, and maximizing intensity of light transmitted by laser and received by device - Google Patents

Abstract

The method involves transmitting an infra-red light on an optical path (6) from a wavelength modulatable infra-red laser (8) to a reflection system and from the reflection system to a charge coupled device (CCD) (12). The laser, the reflection system, and the CCD are adjusted by an automated adjustment system such that the light transmitted by the laser passes through the path from the laser by an open volume (4) to the reflection system and from the reflection system by the open volume to the CCD. An intensity of the light transmitted by the laser and received by the CCD is maximized. An independent claim is also included for a device for absorption-spectroscopic verification of combustible gas in an open volume.

Description

The The invention relates to a method and an apparatus for absorption spectroscopic detection of at least one combustion gas in an open volume.

spectroscopic Devices for the detection of gases in open volumes are already known. Preferably, an infrared light is emitted Laser diode used. In some versions, the light is on Laser diode on a direct light path through the open volume too sent to a spaced light detector. For other versions the laser diode and the light detector are arranged adjacent. In these, the light is spaced by the open volume Retroreflector sent from which it then to the local near the Laser diode arranged light detector is reflected back.

at some embodiments These spectroscopic devices continue to be an additional Laser used, whose light to maintain the optical Adjustment is used. Gas detection and adjustment are therefore with made of separate light sources.

Characteristic in these arrangements is that the laser diode for gas detection and the light detector, or the laser diode and the retroreflector decoupled from each other and spaced in the open volume arranged are, for example, on opposite walls of a production hall.

For the gas detection becomes the wavelength range of the light generated by the laser diode via an absorption line of a to be monitored Gas modulated. Indicates the open volume of this to be monitored Gas on, as the light passes through the open volume the absorption line of the gas in the light spectrum with an amplitude registered by the concentration of the gas in the open Volume depends. The light received by the detector is then processed with algorithms Processed from the amplitude of the absorption line, the absorption strength and thus determining the amount of gas in the open volume.

adversely In such spectroscopic devices, the orientation the diode or the detector to the spaced retroreflector unpredictably changed can be. For example, you can thermal fluctuations the wall material to which the device is mounted, subject to expansion or contraction. These thermal fluctuations, for example, by one-sided on a wall incident sunlight or by the uneven arrangement of heat generating machines in the open volume, for example in a production hall. An impairment orientation is also affected by the influence of soil or wall vibrations possible, as they often do in production halls by electro-mechanical large devices caused. In a change the alignment is the effectiveness of the gas detection due the resulting light intensity attenuation limited or even stopped and must be restored through a complex news become.

Becomes in the restoration of the optical adjustment an additional Laser used, increased this is the apparatus and thus the financial expense of Gas detection. Continue to have the additional one Laser and its control electronics on the device to the actual Gas detection matched or integrated into such a device become.

The have for adjusting an optical adjustment commonly used adjusting means often a limited Accuracy regarding the position to be set. This uncertainty occurs in particular then, if by the adjusting means when adjusting a change in direction is made. The restricted Accuracy is preferred in the art by choice high quality material components or by increasing the Adjustment time compensated. The use of high quality material components increases the costs for the adjusting means. The increase the Verstellzeit extended the period in which a restoration of the optical adjustment is made, which in turn sets the period for the actual gas detection reduced.

Further is on the method for determining the amount of gas in the open Volume disadvantageous that the evaluation of an absorption line of a to be monitored Gases vulnerable is against interference, which can occur during light emission or light reception. So can Defects, even temporary Defects, the diode material and / or the detector material, the wavelength specific at the wavelength the absorption line of the gas to be detected occur to a significant impairment the sensitivity and the precision lead the gas detection.

It is also possible that absorption lines of gases which occur in any proportions of atmospheres or environments, for example water vapor (H ₂ O) or carbon dioxide (CO ₂ ), intervene with the preferred absorption line of the gas to be monitored for detection and thus erroneously lead to an event resulting from this interference, for example triggering an alarm.

In In this case, the sensitivity to false alarms can be reduced be by adding several devices for absorption spectroscopic Detection of a gas to be monitored or different to be monitored Using gases. However, this means that the apparatus and the Personal expenses for the maintenance of the various devices accordingly elevated.

Of the The present invention is therefore based on the technical problem a method and an apparatus for absorption spectroscopic detection indicate at least one combustion gas in an open volume, which at least partially remedy the disadvantages described above, and generally with less equipment and human effort can be used.

The technical problem is caused by a method of absorption spectroscopic Detection of at least one combustion gas in an open volume solved, with the infrared light on an optical path through the open volume one, in particular wavelength-modulatable, Infrared light source to a reflection system and of the reflection system is sent through the open volume to a light detector at the absorption strength of the at least one fire gas from that of the infrared light source emitted and received by the light detector light on hand one, in particular having one or more absorption lines, Absorbance pattern of the at least one combustion gas quantified in which a signal, in particular a pre-alarm signal or alarm signal is activated or is generated when the previously determined absorption of the at least one fire gas is fire characteristic, and in which the infrared light source, the reflection system and / or the light detector be aligned by an automated adjustment system so that the light emitted by the infrared light source is the light path from the infrared light source through the open volume to the reflection system and passes from the reflection system through the open volume to the light detector, wherein the intensity of the light emitted by the infrared light source and the light detector received light is optimized, in particular maximized, is.

Farther becomes the technical problem with a device for absorptionsspektroskopischen detection solved by at least one combustion gas in an open volume, with one, in particular wavelength modulatable, Infrared light source, with a reflection system, with a light detector, and with an automated adjustment system, the infrared light source, the reflection system and the light detector in the open volume are arranged so that the light path of the infrared light source emitted light through the open volume to the reflection system and from the reflection system through the open volume to the light detector runs, characterized in that the infrared light source, the reflection system and / or the light detector from the automated adjustment system are alignable so that emitted by the infrared light source Light the light path from the infrared light source through the open Volume to the reflection system and of the reflection system through passes through the open volume to the light detector.

By the use of an automated adjustment system is ensured that the device is largely continuous, without human intervention is ready for use. changes the orientation of the components of the device, for example the infrared light source, are by the automated alignment corrected in a timely manner. This reduces in particular the maintenance the device considerably.

By the determination of the absorption strength a fire gas from an absorption pattern as opposed to a single absorption line leaves the effect of a wavelength-specific disturbance in the Reduce light-emitting or light-receiving process. The goodness of the An evaluation obtained absorption strength of a combustion gas can thus elevated which reduces the risk of false alarms. In addition, through the consideration of several fire gases in the evaluation not only a possible false alarm but it can be prevented by a differentiated evaluation in terms of the absorption strengths different combustion gases possibly also between different Types of fires be differentiated.

The Device is preferably used in an open volume. This means that no separately closed volume, for example a measuring cell is provided, into which the fire gas to be examined Gas must be introduced. In particular, it is intended that Infrared light source and the light detector and the reflection system at opposite sides, the open volume bounding walls, for example one Production hall, arrange so that the light path between the walls round trip can run. However, it is also possible to detect fire gases in a closed volume, for example a measuring cell, if this is for the application appears advantageous.

As combustion gases gases are to be understood, which can arise in combustion processes. In addition, these gases must have an absorption pattern comprising one or more absorption lines in the infrared spectral range in order to be detectable by a spectroscopic detection method. Examples of combustion gases are carbon monoxide (CO), methane (CH ₄ ), ammonia (NH ₃ ), ethene (C ₂ H ₄ ) or nitrous oxide (N ₂ O). However, the abovementioned list of combustion gases is not exhaustive and may include, for example, other hydrocarbons in addition to methane.

For the abovementioned combustion gases, spectroscopic detection in the wavelength range from 2.2 μm to 2.4 μm is preferred because of the absorption patterns present there. In particular, the combustion gases CO, CH ₄ , NH ₃ and C ₂ H _{4 are} detected in the wavelength range from 2338 nm to 2340 nm.

Some combustion gases occur in certain combustion processes. CO is produced essentially in all types of fire. As smoldering fires are to understand fires that occur at low temperature and low oxygen supply. NH ₃ occurs especially in smoldering fires of fertilizers and smoldering fires of other organic substances.

The automated adjustment system directs the light detector and / or Preferably, the infrared light source is that of the infrared light source emitted light travels a light path through the open Volume from the infrared light source to the reflection system and from the reflection system through the open volume to the light detector runs. In particular, the light path with the automated adjustment system by at least one translational movement in at least one of three spatial directions independently be maintained from each other. In addition, it is possible the Light path through at least one rotational movement about at least one Maintain axis of rotation around. Preferably, the alignment happens thereby means for every spatial direction or for each Rotary axis individually arranged, controllable stepper motors.

The automated adjustment system is preferably two perpendicular to each other running axes of rotation independently pivotable. Is of it a rotation axis vertically, thus perpendicular to Tangential plane of the ground, and the other horizontal, ie parallel to the tangential plane of the soil, causes a rotation of the automated adjustment system about the vertical axis a horizontal Alignment and rotation about the horizontal axis a vertical one Orientation. As a biaxial mount, for example, such used as they are in simple astronomical telescopes be used to the trajectory of a celestial body consequences.

When Infrared light sources can For example, infrared laser or light emitting diodes (LED) used become. Furthermore, the infrared light source can in particular also optical elements, such as optical lenses include, with which focuses the emitted infrared light in a suitable manner and the light path through the open volume to the reflection system can be sent.

Preferably For example, the infrared light source is a wavelength modulatable infrared laser. The modulation of the wavelength can in particular over the control of the used for pumping the laser active material electric current. However, it is also possible the modulation over to carry out a control of the temperature of the laser-active material. The Modulability of the wavelength allows it, entire absorption patterns comprising several absorption lines a fire gas or more fire gases spectroscopically record and thus prove their absorption strengths.

In a further preferred embodiment of the device has the Reflection system on a retroreflector. A ray of light that on one of the reflective surfaces of the retroreflector becomes parallel to the impinging Beam with a slight spatial Offset reflected back in the direction he came from. In this case, it is preferable to use the infrared light source and the light detector adjacent to each other adjacent to arrange so that by the spatial offset generated by the retroreflector that of the Infrared light source emitted light is supplied to the light detector.

in the Contrary to configurations of spectroscopic gas detectors in which the light path of the light emitted by the light source directly to the light detector, let yourself by using a retroreflector the light path from the light source easily doubling to the light detector. An extension of the light path increases the Sensitivity of gas detection in the open volume and allows the Gas detection also in volumes otherwise sufficient for gas detection long light paths are not feasible. In addition, with such a Arranging the effect of temperature or pressure gradients in each other adjacent air layers traversed by the light on the light path be at least partially compensated.

In a further preferred embodiment of the device has the Reflection system on a mirror system. Such a mirror system preferably has at least two, in particular imaging, mirror on. Furthermore, the mirror system can also other beam-deflecting Include elements such as prisms or deflecting mirrors. When using a Mirror system leaves by appropriate arrangement of the mirror and optionally the beam-deflecting elements, as opposed to use a retroreflector, the light path from the light source to the light detector not just double, but by a certain integer multiple this basic light path length multiply. The sensitivity of the gas detection is accordingly essentially also increased by this factor.

With The device described here can be light paths of several Meters, for example ten meters to several hundred meters, to reach.

When Light detector may be a semiconductor detector, such as a photodiode array or a "chargecoupled device "(CCD) become. It is possible optical filters at a location of the light path, preferably immediately in front of the light detector, to arrange that from the infrared light source emitted light passes through this optical filter. By The choice of appropriate optical filters can be light with non-infrared Wavelength, For example, visible daylight, largely, especially predominantly, be filtered out of the detection process. Furthermore, it is possible to the optical detector imaging optical elements, such as optical Lenses to arrange, by means of which the infrared light in a suitable Were collected and mapped on the light-sensitive surface of the light detector can be.

Preferably the infrared light source and the light detector are close to each other mounted on a platform. The term platform is very much here far to understand and, for example, one with an open one Cover provided hollow cylinder. In the example of the hollow cylinder can the infrared light source and the light detector in the hollow cylinder be arranged adjacent so that the light emitting part of Infrared light source and the light-sensitive part of the light detector the open end face of the hollow cylinder facing, wherein the open end then in the direction of the spaced reflection system is aligned. However, it is also possible to have a different arrangement the infrared light source and the light detector at the platform choose. In this case, the hollow cylinder is still in particular with equipped transfer optics, such as deflecting mirrors, provided, to supply the infrared light to the light detector.

The The method described below is automated by executing various algorithms executed. A human intervention is always possible though not mandatory.

at the implementation of the method for the absorption spectroscopic detection of at least a fire gas in an open volume is the infrared light of the infrared light source emitted and passes through the light path through the open volumes to the reflection system, for example the retroreflector, and from the reflection system through the open volume to the light detector.

The Spectrum of the infrared light received by the light detector has an absorption pattern of the at least one combustion gas with one of the concentration of the at least one combustion gas in the open Volume dependent absorption strength on. Due to this absorption strength can be in the open Volume Existing concentration of at least one fire gas be determined. As absorption patterns are within the scope of this application always to understand one or more absorption lines of a combustion gas, where the absorption lines also depending on the spectral resolution at least partially overlap can.

Especially it is preferred if for the determination of the absorption strength a fire gas a multiple absorption lines comprehensive absorption pattern considered becomes. This will affect the influence of wavelength-specific noise the wavelengths individual absorption lines reduced to the evaluation of the absorption strengths and the goodness improved fire gas detection. The several absorption lines are in particular by the wavelength modulation of the infrared light source detected.

Farther it is preferable if the light received by the light detector evaluated not only on a fire gas but on several combustion gases becomes. By doing so, the basis to which one is possibly supports the following signal, broader and thus reduces the risk of false alarms. It may, for example, the ratio of the absorption strengths of different combustion gases for the Presence of a fire. Again, the wavelength modulation the infrared light source can be advantageously applied.

Preferably, the method detects CO and CH ₄ as combustion gases. Alternatively, however, the detection of CO and CH _{4 can} also be combined with other combustion gases.

The multiple combustion gases preferably have absorption lines and / or absorption patterns in the same wavelength range on, so the absorption levels the multiple fire gases in the wavelength modulation of the infrared light source can be determined in an evaluation step. The consideration allows multiple combustion gases for example, the presence of a fire with high safety determine and pretend to be a fire Event, such as a gas leak, delineate. Furthermore can through the consideration several types of combustion gases and, where appropriate, dangerousness of the fire become.

going from the evaluation for determining the absorption strengths of a or more fire gases that the absorption strengths and / or the conditions the absorption strengths are fire-characteristic, a signal is triggered. Brand Characteristic is the absorption strength of a combustion gas when the concentration derived from it of the combustion gas in the open volume exceeds a value, the under typically natural occurring concentrations, for example in the case of an open-air monitoring, or typically customary occurring concentrations, for example in the case of a production hall monitoring, lies. The thresholds of the brand characteristic can be estimated Brand gas concentrations are preferably before the implementation of the method or before Commissioning of the device and are in particular to the open volume in which the fire gas detection is carried out, customized.

at the signal may be an optical signal, for example a flashing light, an acoustic signal, for example a sequence of tones, or any other convenient signal. Especially It is the task of the signal, people on the result of the fire gas detection to draw attention. For example, the signal can also be sent an electronic message, such as an email or Short message, with a to the result of the fire gas detection adjusted content or a comparable electronic signal include.

The signals activated or generated by the device are used in the Essentially divided into alarm signals and pre-alarm signals. One Alarm signal is activated or generated, for example, when the absorption intensities different combustion gases are all fire characteristic independent of each other. In such a case, with high probability of the Existence of a fire. A pre-alarm signal is for example, activated or generated when the absorption strength of only one of the several proven fire gases brand characteristic is. However, it is also possible activate or generate an alarm signal when the absorption strength of is fire characteristic only to one of several fire gases, if For example, this one fire gas taken by itself already one noxious Has effect.

The Alignment essentially involves the actuation of the automated Adjustment system arranged adjusting means, such as stepper motors. The following is an example of always talking about stepper motors. However, it is also possible to use other suitable adjusting means. The stepper motors are preferably within a predetermined step range adjusted by previously specified step increments. After every adjustment a step increment then becomes the effect of the adjustment to the intensity of the infrared light received by the light detector detected.

Especially become in alignment direction changes of the adjustment largely, preferably completely, avoided. That way the influence of inaccuracies, which are preferred in direction changes the adjustment occur, keep low. In particular, can be so the influence of the gear play of a stepping motor on the accuracy reduce the alignment.

Preferably The stepper motors are brought into a position in which the intensity of the light emitted by the infrared light source and the light detector reached maximum light. At this procedure is particularly advantageous that no additional light signal, for example an additional one Laser beam, is needed, to make an alignment or message, but that for the Alignment also for the fire gas detection provided infrared light is used. Consequently is the apparatus and control engineering effort for the fire gas detection reduced.

In a preferred embodiment of the method, the automated adjustment system performs at least two-stage alignment, for example with a coarse alignment and at least one subsequent fine alignment. The first stage of the alignment, for example the coarse alignment, comprises in particular the checking of a large solid angle range with large step increments of the stepping motor. In the solid angle range sampled in the first stage, the region with the highest received intensity is determined. This area with the highest received intensity is then used as a smaller solid angle area for the following level of alignment. The second stage of the off Direction, for example, the fine alignment, in particular includes the review in the smaller solid angle range with smaller increments of the stepping motor. The size of the solid angle range to be tested, and thus the number of stages of alignment, is fundamentally limited by the gear play of a stepping motor occurring, for example, in the event of a change in direction.

Especially it is advantageous in the orientation and / or Nachrichtung, the Adjustment of the stepper motors during the alignment cycle determined highest received intensity. This means that the stepper motors are not based on the number of steps in which the highest received intensity exhibiting attitude. Rather, at the Setting the stepper motor the received intensities with the highest received intensity compared, and the setting is chosen at the received intensity within certain tolerance limits with the highest intensity received.

By this type of alignment affects the example as a gear play the stepper motors occurring inaccuracy of the adjusting means, the usual Step error has the consequence, the quality of the alignment is not, so that stepper motors with lower technical requirements can be used, which in particular reduces the cost of the device.

Preferably The automated alignment is recurring during the Operating the device, for example, at regular intervals, carried out. These Embodiment of the method is particularly suitable when interference or impairments by an unintentional change in the orientation of the Elements of the device, such as the light detector, with high frequency are expected. For example, is the device placed in an environment where they have strong vibrations for a long period of time is suspended is a regular change the orientation predictable. These regular changes can be made by the during the Operational recurring alignment can be effectively corrected.

It but it is also possible that the alignment in addition or alternatively targeted at one for the effectiveness of the method adverse weakening the intensity performed by the light becomes. This embodiment of the method is particularly suitable when disorders or impairments by an unintentional change in the orientation of the Elements of the device are unlikely. In this case will be the time required for the alignment and the resulting interruption of the fire gas detection as low as possible held.

In Another preferred embodiment of the method is the intensity of the light emitted by the infrared light source and the light detector received light quantified. Unlike the wavelength-specific light attenuation By the absorption of the fire gases the intensity of the light becomes on the light path, for example, by scattering and absorption on particles present in the air, for example liquid or solid Aerosols, toned down. Such particles, for example soot particles, ash particles or smoke, step up in fires and can do that Light passing through a particle-enriched open volume running, essentially wavelength-unspecific weaken. This substantially non-wavelength attenuation may be in addition to the absorption strengths the combustion gases used to indicate the presence of a fire.

Accordingly may be a signal, in particular a pre-alarm signal or alarm signal, be activated or generated when the intensity of the infrared light source emitted and received by the light detector light brand characteristic attenuated is. As a fire characteristic, a weakening of the light, for example be scored if the light detector is within a short period of time, for example, ten minutes perceives occurring attenuation of the light, not by a change the orientation of the infrared light source or the light detector was caused. Preferably, the intensity is considered fire characteristic attenuated if they one at the beginning of commissioning of the device Value falls below.

The The present invention can be practiced in many ways. The following are exemplary embodiments of the present invention with reference to the accompanying figures. In show the figures:

1 an exemplary, schematic embodiment of the device with a retroreflector as a reflection system and

2 an exemplary schematic embodiment of the device with a system of three mirrors as a reflection system.

1 shows an arrangement as it can be used as a device for the fire gas detection. The device consists of two components spaced on opposite walls 20 are attached. In between lies an open volume 4 ,

On a wall 20 At about 5 m, a component of the device, which is a wavelength-modulatable infrared laser, is mounted 8th as an infrared light source, a CCD 12 as a light detector and a biaxial mount 14 as an automated adjustment system. Furthermore, an electronic control, evaluation and alarm unit 18 adjacent to the infrared laser 8th arranged.

The electronic control, evaluation and alarm unit 18 is with the infrared laser 8th , the biaxial mount 14 and the CCD 12 Connects and regulates the wavelength modulation of the infrared laser 8th , receives and analyzes the light incident on the CCD 12 generated intensity data, and controls the at the biaxial mount 14 arranged stepper motors (not shown) to make if necessary, an alignment or Nachrichtung the mounted on the automated adjustment system components. An axis of the biaxial mount runs in a vertical direction approximately parallel to the wall 20 so that rotation about this axis causes a change in orientation in the horizontal direction. The other axis is perpendicular to the first axis and approximately parallel to the wall 20 such that rotation about this axis causes a change in vertical orientation.

On the wall 20 on the other side of the open volume 4 is a retroreflector at a height of about 5 m 10a appropriate. At approximately parallel walls 20 it is convenient, the infrared laser 8th , the CCD 12 and the retroreflector 10a at a substantially same height. However, other arrangements are possible as long as a light path 6 between the infrared laser 8th over the retroreflector 10a to the CCD 12 can be produced.

The infrared laser 8th and the CCD 12 are by means of biaxial mount 14 by pivoting the structure about the horizontal and / or vertical axis, in such a position to the retroreflector 10a brought that from the infrared laser 8th Light emitted a light path 6 through the open volume 4 to the retroreflector 10a and from there to the CCD 12 passes.

Develops at a specific location in the open volume 4 a fire 16 For example, on the ground, by the chemical reaction, for example, soot particles (not shown) and molecules of a fire gas 2 or more fire gases 2 generated. Essentially by convection but also by other air movements spread the fire gases 2 in the open volume 4 out. A certain time after the outbreak of the fire 16 reach the soot particles and also the fire gases 2 the part of the open volume 4 through which the light path 6 running. Essentially, due to scattering of the soot particles, the part of the infrared light is transmitted via the light path 6 to the CCD 12 passes, decreases. In the part of the light coming from the CCD 12 are still receiving the absorption patterns of the fire 16 generated combustion gases 2 registered with an absorption strength that is the average concentration of the combustion gases 2 in the from the light path 6 occupied partial volume of the open volume 4 equivalent.

That of the CCD 12 received light is in the electronic control, evaluation and alarm unit 18 Spectral on the intensity attenuation and on the absorption patterns of the combustion gases 2 evaluated. Is the concentration of a fire gas 2 beyond a certain tolerance range, is determined by the electronic control, evaluation and alarm unit 18 an opto-acoustic signal is triggered.

In the 2 shown arrangement is similar to 1 , Instead of a retroreflector 10a In this example, the mirror system is made up of three mirrors 10b used. A mirror 10b is between the infrared laser 8th and the CCD 12 on one side of the open volume 4 arranged. The other two mirrors 10b are adjacent to each other on the wall 20 on the opposite side of the open volume 4 , By this arrangement, the light path can be 6 between the infrared laser 8th and the CCD 12 opposite to the 1 double the example shown. This is the detection sensitivity for the combustion gases 2 also substantially doubled.

Claims (13)

Method for the absorption spectroscopic detection of at least one combustion gas ( 2 ) in an open volume ( 4 ), - in the infrared light on a light path ( 6 ) through the open volume ( 4 ) of a, in particular wavelength modulatable, infrared light source ( 8th ) to a reflection system ( 10 ) and of the reflection system ( 10 ) through the open volume ( 4 ) to a light detector ( 12 ), in which the absorption strength of the at least one combustion gas ( 2 ) from the infrared light source ( 8th ) emitted by the light detector ( 12 ) received light on the basis of, in particular one or more absorption lines having, absorption pattern of the at least one combustion gas ( 2 ), in which a signal, in particular a pre-alarm signal or alarm signal, is activated or generated when the previously determined absorption strength of the at least one combustion gas ( 2 ) is brand - characteristic, and - in which an automated adjustment system ( 14 ) the infrared light source ( 8th ), the reflection system ( 10 ) and / or the light detector ( 12 ) in such a way that that of the infrared light source ( 8th ) emitted light the light path ( 6 ) from the infrared light source ( 8th ) through the open volume ( 4 ) to the reflection system ( 10 ) and of the reflection system ( 10 ) through the open volume ( 4 ) to the light detector ( 12 ), wherein the intensity of the infrared light source ( 8th ) emitted by the light detector ( 12 ) received light, in particular maximized, is. Method according to Claim 1, in which the automated adjustment system ( 14 ) an at least two-stage alignment is performed. Method according to Claim 1 or 2, in which the information obtained from the automated adjustment system ( 14 ) alignment is carried out recurrently. Method according to one of claims 1 to 3, in which the automated adjustment system ( 14 ) targeted at a detrimental to the effectiveness of the method attenuation of the intensity of the infrared light source ( 8th ) emitted by the light detector ( 12 ) received light is performed. Method according to one of Claims 1 to 4, in which the wavelength range of the infrared light source ( 8th ) via at least one absorption pattern of the at least one combustion gas ( 2 ) is modulated. Method according to one of Claims 1 to 5, in which the intensity of the light emitted by the infrared light source ( 8th ) emitted by the light detector ( 12 ) received light is quantified. Method according to Claim 6, in which a signal, in particular a pre-alarm signal or alarm signal, is activated or generated when the intensity of the light emitted by the infrared light source ( 8th ) emitted by the light detector ( 12 ) received light is fire characteristic attenuated. Method according to one of claims 1 to 7, wherein the absorption strength of the at least one combustion gas ( 2 ) is quantified by means of an absorption pattern having a plurality of absorption lines. Method according to one of claims 1 to 8, wherein the absorption strengths of a plurality of combustion gases ( 2 ) can be quantified. Device for the absorption spectroscopic detection of at least one combustion gas ( 2 ) in an open volume ( 4 ), - with an, in particular wavelength-modulatable, infrared light source ( 8th ), - with a reflection system ( 10 ), - with a light detector ( 12 ), and - with an automated adjustment system ( 14 ), - the infrared light source ( 8th ), the reflection system ( 10 ) and the light detector ( 12 ) in the open volume ( 4 ) are arranged so that the light path ( 6 ) of the infrared light source ( 8th ) emitted light through the open volume ( 4 ) to the reflection system ( 10 ) and of the reflection system ( 10 ) through the open volume ( 4 ) to the light detector ( 12 ), characterized in that - the infrared light source ( 8th ), the reflection system ( 10 ) and / or the light detector ( 12 ) of the automated adjustment system ( 14 ) are alignable so that the of the infrared light source ( 8th ) emitted light the light path ( 6 ) from the infrared light source ( 8th ) through the open volume ( 4 ) to the reflection system ( 10 ) and of the reflection system ( 10 ) through the open volume ( 4 ) to the light detector ( 12 ) goes through. Apparatus according to claim 10, characterized in that the automated adjustment system ( 14 ) has a biaxial mount, in particular with mutually perpendicular axes of rotation. Apparatus according to claim 10 or 11, characterized in that the infrared light source ( 8th ) has an infrared laser. Device according to one of claims 10 to 12, characterized in that the reflection system ( 10 ) a retroreflector ( 10a ) or a mirror system ( 10b ) having.