DE102016116120B4 - Method for operating a cooking appliance and cooking appliance - Google Patents

Abstract

Method for operating a cooking appliance (10) with at least one treatment device (11) for treating the food (6) to be cooked in at least one cooking chamber (12), wherein at least one characteristic parameter of the food (6) to be cooked is recorded without contact using at least one measuring system (7). and wherein the treatment device (11) is at least partially controlled as a function of the determined parameter and wherein, for this purpose, electromagnetic measuring radiation, preferably in a frequency band, is generated with at least one transmitting device (17) and introduced into the cooking chamber (12) and with at least one receiving device (27) is received and evaluated, characterized in that for at least some frequencies of the frequency band, a first propagation time of the measurement radiation is determined for at least a first measurement section (1), which extends between the transmission device (17) and an end face (16 ) of the food to be cooked (6) and that at least a second propagation time of the measurement radiation is used for at least a second measurement section (2), which extends from the transmitting device (17) through an air layer to a food support (13) on which the food to be cooked ( 6) and that on the basis of the first and the second transit time at least a first difference is determined, which corresponds to a transit time of the measuring radiation through a layer of air with at least approximately the same extent as that of the cooking item (6) and that to determine the parameter of the cooking item ( 6) the first difference is compared with at least one transit time of the measurement radiation through the item to be cooked (6).

Description

The present invention relates to a method for operating a cooking appliance and a cooking appliance with at least one treatment device for treating food to be cooked in at least one cooking chamber. The cooking appliance comprises at least one measuring system for contactless detection of at least one characteristic parameter of the item to be cooked.

In order to achieve an optimal cooking result, it is usually necessary to take certain properties of the food into account. Such information about the food to be cooked is particularly important for the reliable execution of automatic programs. For example, for a tasty preparation of a roast in an oven using an automatic function, the size of the roast and whether the roast is still frozen, for example, should be taken into account.

It is also advantageous if certain properties of the food to be cooked can be independently recorded and taken into account by the cooking appliance. Particularly convenient for the user is z. B. a non-contact detection of the food properties.

In the prior art, therefore, cooking devices have become known which use the radar principle in order to obtain information about the food in a non-contact manner. However, very complex and cost-intensive radar technology is often used for this purpose. In addition, the known devices and methods can be improved with regard to the statements that can be made on the basis of the radar information about the food. For example, it is often only possible to make relative statements about the condition of the food to be cooked, so that only specific changes can be detected over a longer cooking time.

It is therefore the object of the present invention to provide a method for operating a cooking appliance and a cooking appliance which enable improved non-contact characterization of the food to be cooked by means of electromagnetic measuring radiation.

This object is achieved by a method having the features of claim 1 and by a cooking appliance having the features of claim 16. Preferred features are the subject matter of the dependent claims. Further advantages and features emerge from the general description of the invention and the description of the exemplary embodiments.

The method according to the invention is used to operate a cooking appliance. The cooking appliance comprises at least one treatment device for treating food to be cooked in at least one cooking chamber. At least one characteristic parameter of the item to be cooked is recorded without contact using at least one measuring system. The treatment device is at least partially controlled as a function of the parameter determined. The measuring system comprises at least one transmitting device and at least one receiving device. Electromagnetic measuring radiation is generated with the transmitting device and introduced into the cooking chamber. The electromagnetic measuring radiation is received with the receiving device. The received measurement radiation is evaluated. At least one first propagation time of the measurement radiation is determined for at least one first measurement section. The first measuring section extends between the transmitting device and an end face of the item to be cooked that faces the transmitting device. At least a second propagation time of the measurement radiation is used for at least one second measurement section. The second running time that is used is provided in particular by at least one variable that corresponds to the running time. The second measuring section extends from the transmitting device through a layer of air to a food support on which the food rests. At least one first difference is determined on the basis of the first and the second transit time. The first difference corresponds to a transit time of the measuring radiation through a layer of air with an at least approximately the same extent as that of the food to be cooked. To determine the parameter of the item to be cooked, the first difference is compared with at least one transit time of the measurement radiation through the item to be cooked.

The method according to the invention has many advantages. A significant advantage is that runtime measurements are carried out to determine the parameter of the food to be cooked. Such transit time measurements can also be technically implemented inexpensively in a cooking appliance or a cooking chamber. The runtime measurement offers very reliable and reproducible measurement results, from which a great deal of information about the food to be cooked can be obtained.

The first difference between the first runtime and the second runtime is particularly advantageous. This runtime difference reliably and reproducibly describes a runtime through a layer of air that corresponds to the expansion of the food to be cooked. Knowing the first difference, the influence of the geometric expansion of the food to be cooked on the parameter to be determined can be reliably calculated out. As a result, not only relative parameters of the food to be cooked can be determined with the method according to the invention, but also actual ones Characteristics of the food. Thus, a reliable statement about a parameter cannot only be made by long-term observation of the food over the entire cooking time. On the other hand, a meaningful parameter can be determined at any point in time before or during or even after cooking. Without the first difference, for example, no statement can be made as to whether the delay in the running time is caused by particularly thick food or by thin food with a particularly high refraction. With the method according to the invention, on the other hand, the actual breaking of the food to be cooked can be determined since the influence of the geometric thickness of the food to be cooked can be calculated out.

At least a third propagation time of the measurement radiation is preferably determined for at least a third measurement section. The third measurement section extends from the transmitting device through the item to be cooked to a rear side of the item to be cooked that faces away from the transmitting device. In particular, at least one second difference is determined on the basis of the first and third transit times. The second difference preferably corresponds to the propagation time of the measuring radiation through the food to be cooked. The third propagation time measurement and the subsequent formation of the difference with the first propagation time offer a particularly reliable and technically uncomplicated possibility of determining the propagation time of the measuring radiation through the cooking item and, moreover, its actual material properties.

The third measurement section is in particular an extension of the first measurement section. As a result, the transit time required for the measuring radiation to pass through the food to be cooked can be described in a particularly good approximation on the basis of the second difference. The measuring sections run in particular perpendicularly to the food support on which the food rests. The measuring sections can also run horizontally and/or transversely to the food support. It is also possible for the third measurement section and the first measurement section to run parallel to one another. The third measuring section and the first measuring section preferably run adjacently through the food to be cooked.

The third propagation time is preferably determined by at least one reflection measurement. The transmitting device and the receiving device are preferably located on one side of the food support and/or the food to be cooked. The first transit time and/or the second transit time are also particularly preferably recorded using at least one reflection measurement. A reflection measurement can be carried out particularly reliably and inexpensively in a cooking chamber of the cooking appliance.

It is possible and preferred that at least a fourth propagation time of the measurement radiation is determined for at least a fourth measurement section. The fourth measuring section extends at least through the food to be cooked and through a food support on which the food to be cooked rests. At least a fifth propagation time of the measurement radiation is preferably also determined for at least a fifth measurement section. The fifth measurement section corresponds in particular to the fourth measurement section without the food to be cooked. In particular, the measurement radiation in the fifth measurement section passes through the objects that the measurement radiation also passes through in the fourth measurement section of the cooking item, but with the exception of the cooking item. The fourth and fifth measurement sections preferably run essentially parallel to one another. The fifth measurement section is preferably an extension of the first measurement section. It is also possible for the first measurement section and the fifth measurement section to run parallel to one another. At least one third difference is preferably determined on the basis of the fourth and fifth runtime. The third difference corresponds to the propagation time of the measuring radiation through the food to be cooked.

The measurement of the fourth and fifth transit time is preferably carried out by at least one transmission measurement. The transmitting device and the receiving device are preferably arranged on opposite sides of the food support and/or the food to be cooked. The food support preferably has at least one section that is at least partially transparent to the measuring radiation. For example, the food support is made from a permeable material. The food support can also have recesses, for example in the manner of a grating. A transmission measurement offers the advantage that the measurement radiation only has to pass through the objects once. This is particularly advantageous with highly absorbent materials, since the signals are correspondingly less weakened.

In the context of the present invention, using the second runtime is understood in particular to mean that both a runtime and a variable characterizing the runtime and, for example, a time and/or a distance can be offset.

It is particularly preferred that the second transit time is recorded by at least one measurement with the measurement system. The second transit time is particularly preferably recorded by at least one reflection measurement and/or transmission measurement. It is possible that the second running time for a specific cooking process is recorded only once. It is also possible that the second running time is measured at least twice or several times during a specific cooking process. As a result, a change in the position of the food support can be reliably detected, for example. For example, when a user pushes the food support further up during the cooking process in order to align the food closer to a heat source. Determining the second transit time by means of a measurement thus offers a particularly reliable determination of the parameter, since the precise distance between the food support and the transmitting device is known.

It is also possible and preferred that the second running time is determined based on an insertion position of the food support in the cooking chamber. The distance between the food support and the transmitting device can be determined based on the insertion position. For example, an assignment of insertion positions and distances is stored in the measuring system. Based on the distance, the second propagation time can then be reliably derived based on the phase velocity of the measurement radiation in air. This running time determined in this way is then used in particular as the second running time. The insertion position can be identified, for example, based on at least one user input. The insertion position can be specified for a user. A different sensory detection of the insertion position is also possible, for example a mechano-sensory detection by means of a contact switch.

In a particularly preferred development of the method, at least one geometric dimension of the item to be cooked is determined as a characteristic parameter. The geometric dimension is determined at least approximately, in particular using a product of the first difference and a phase velocity of the measurement radiation in air and/or vacuum. The geometric dimension determined in this way preferably relates to the region of the item to be cooked in which the first measuring section meets the item to be cooked and/or in which the third measuring section runs through the item to be cooked. The geometric dimension is particularly preferably a geometric height of the food to be cooked. The height of the food to be cooked provides a particularly informative parameter of the food to be cooked. For example, a required cooking time can be determined particularly reliably using this parameter. It is also possible that a cooking time stored in a program function is adjusted based on the geometric dimensions of the food to be cooked with at least one time safety interval. As a result, cooking times that are too short or too long can be avoided in a particularly reliable manner.

The first measuring section preferably extends to a highest area on the end face of the item to be cooked. The third measuring section preferably extends to the same area on the front side of the item to be cooked as does the first measuring section. This enables a particularly precise determination of the maximum geometric dimension and preferably the maximum height of the food to be cooked. It is also possible for the first measuring section to extend to a central area of the end face of the item to be cooked. The highest area of an item to be cooked is also often located in a central area of the end face, so that a measurement section arranged in this way also allows a very reliable statement to be made about the maximum height of the item to be cooked.

The first measuring section can also extend to any desired area on the front side of the item to be cooked. For example, measurements that do not relate to the geometric height or dimensions of the item to be cooked do not need to be measured at the highest point of the item to be cooked. For measurements to determine other parameters, for example, any point on the face can be selected. The geometric dimensions of the food to be cooked can then be determined at this measuring point on the basis of the difference formation and offsetting of the transit times described above. In order to determine the parameter, it can be advantageous to measure in an area of the food to be cooked where the thickness of the food to be cooked is small because there the measurement signal is less strongly damped by absorption in the food to be cooked. For the determination of other parameters, however, the first measuring section is preferably aligned to a higher area and/or to the highest area of the end face of the item to be cooked, provided that the measuring signal is strong enough there

The end face can be arranged, for example, on an upper side and/or underside and/or on a lateral area of the item to be cooked, depending on which of the sides of the item to be cooked faces the transmission device. The rear side of the item to be cooked is preferably on a side of the item to be cooked that is opposite the front side. In a reflection measurement, the rear side of the item to be cooked is preferably on a side of the item to be cooked that is opposite the transmitting device and/or receiving device. In the case of a transmission measurement, the rear side is preferably on a side of the item to be cooked that faces the receiving device.

It is possible and preferred that a plurality of first transit times is determined. The first measurement sections extend in particular to different points on the end face of the item to be cooked. The first running times recorded in this way are preferably compared with one another, so that the shortest running time between the transmitting device and the item to be cooked can be determined. The first difference is then preferably formed on the basis of the shortest transit time and the second transit time. This has the advantage that the first difference corresponds at least approximately to a maximum height of the food to be cooked.

A plurality of third running times is preferably also determined, with the third measurement sections extending in particular to different points on the end face of the item to be cooked. The third measuring sections preferably extend to the same points on the end face of the food to be cooked as do the associated first measuring sections. As a result, the information derived from the second difference is particularly reliable and reproducible.

It can be provided that the measurements of the propagation times are carried out at the various points on the end face of the item to be cooked using a plurality of transmitting devices and/or receiving devices. Then preferably the signal of that transmitting device and/or receiving device is used which transilluminates the item to be cooked at the point with the greatest geometrical dimension. It is also possible that the transmitting device and/or receiving device comprises at least a plurality of antennas and preferably an antenna array. The individual antennas are then preferably addressed in a phase-controlled manner, so that the measurement radiation can be emitted in a pivoted manner in the manner of a transmission lobe. This enables the food to be cooked or the food support to be scanned. At least one transmission angle is then preferably determined and adjusted by a corresponding evaluation of the measurement radiation received at the individual antennas. This transmission angle is then preferably used for the further measurements of the propagation times and in particular for the measurement of the first and/or second and/or third propagation time. In this case, the propagation times which have a comparable transmission angle are preferably offset against one another to form a difference.

It is possible for a plurality of running times to be determined while the food support and the food to be cooked are pushed into the cooking space and/or pulled out of the cooking space. Such an embodiment of the method is particularly advantageous since it is particularly easy to achieve that the respective measurement sections can extend to different points on the food or the food support. The measurements are preferably carried out continuously. In this way, the second runtime is preferably measured via the second measuring section when it is pushed in. This preferably takes place when the transmitting device and/or receiving device is aligned in such a way that there is no food to be cooked in the second measuring section. First transit times are preferably also measured during insertion and/or extraction. Preferably, the shortest first transit time is then determined, as described above, in order to determine the shortest distance between the transmitting device and the item to be cooked and thus its maximum height. Preferably, the measurement of the third transit time along the third measurement section also takes place during insertion. It is also possible that the fourth and/or fifth running time is measured during insertion.

In particular, the second running time is only measured once during the cooking process. The second running time is preferably determined at the beginning of the cooking process. It is also possible that the first running time is measured only once and preferably at the beginning of the cooking process. The first and second running time can also be measured repeatedly. The third running time and/or the fifth running time are preferably measured repeatedly before and/or during and/or after the cooking process.

In a further advantageous embodiment of the method, at least one phase velocity of the measuring radiation in the food to be cooked is determined as a characteristic parameter of the food to be cooked. The phase velocity is preferably determined using the first and second difference. In particular, the phase velocity is determined using a quotient of the first and second difference, which is multiplied by the phase velocity of the measurement radiation in air and/or in a vacuum. It is also possible that the third difference is used to determine the phase velocity of the measuring radiation in the food to be cooked. The phase speed in the food to be cooked is a particularly informative parameter that can be used, for example, to derive information about the moisture content, the temperature and/or the state of aggregation of the water contained in the food to be cooked.

In another advantageous embodiment of the method, at least one real part ε _{r ′} of the relative complex permittivity ε _r of the item to be cooked is determined as the characteristic parameter of the item to be cooked. In order to determine the real part ε _{r ′} of the relative complex permittivity ε _r , the first and the second difference are preferably set in relation. In particular, a quotient of the squares of the first and second transit time difference is formed for this purpose. It is also possible that the third difference is used to determine the real part ε _{r ′} of the relative complex permittivity ε _r . It is also possible that the relative complex permittivity with real and imaginary parts is determined as a characteristic parameter.

The real part makes a statement about the reversible storage capacity of electromagnetic radiation in the food, while the imaginary part describes how much electromagnetic energy is irreversibly converted into heat through absorption in the food. The real and imaginary parts depend on the food, the condition of the food, the temperature and the frequency. If the high-frequency sensor only works at a single frequency f ₀ , only ε _{r '} (f ₀ ) and ε _r'' (f ₀ ) can be determined. The frequency dependency is not recorded. However, since the frequency dependence of the real part ε _{r ′} (f) and the imaginary part ε _r ″(f) in particular has conspicuous cooking product characteristics, a high-frequency sensor with a high frequency bandwidth supplies more information than a narrow-band sensor.

The relatively complex permittivity is particularly well suited as a parameter since it changes in particular with the temperature and/or moisture content of the food to be cooked and the end of the cooking time can therefore be determined particularly reliably. It is also possible for a thawing process to be monitored using the relative complex permittivity. The method according to the invention has the advantage here that not only the change in the relative complex permittivity during cooking or thawing can be detected, but also the actual relative complex permittivity at a given point in time is measured. In this way it can be recognized whether the food to be cooked is still frozen or raw or already cooked, without the need for lengthy time monitoring. The type and condition of the food to be cooked can be estimated via the course of the relative complex permittivity over the frequency.

In a further refinement, it is possible for an insertion position of the item to be cooked in the cooking chamber to be determined as a characteristic parameter. The insertion position is preferably determined at least approximately using a product of the second transit time and a phase velocity of the measurement radiation in air and/or in a vacuum. The shelf height of the food rack is particularly helpful, for example to enable a distribution of top and bottom heat that is adapted to the respective shelf height. In addition, by determining the insertion height, a message can be issued to the user if he has selected an unfavorable insertion position for a specific program.

If the insertion height of the food support is known, for example through a user input or user guidance, there is no need to measure the second running time. However, an additional measurement of the second running time is advantageous, since when using supports for cooking with different base geometries the distance between the transmitting device and/or receiving device and the support surface of the cooking product does not correspond to the insertion height.

It is possible for at least one amplitude of the measurement radiation to be detected after the item to be cooked has passed through it at least once. An amplitude after a single pass is preferably recorded in a transmission measurement. It is also possible for at least one amplitude to be detected after the item to be cooked has passed through it several times, for example in a reflection measurement. The amplitude is preferably compared with at least one other amplitude which was recorded under comparable conditions without the food to be cooked passing through. The amplitudes are preferably set in a ratio to one another which corresponds to the attenuation of the measuring radiation by the food to be cooked. In particular, a quotient of the two amplitudes is formed. It is also possible that at least one wave property other than the amplitude is detected, for example a frequency and/or a phase position and/or a polarization.

In a further preferred embodiment it is provided that at least one penetration depth of the measuring radiation into the food to be cooked is determined as a characteristic parameter. The penetration depth is preferably determined based on the damping and a geometric dimension of the food to be cooked in the measurement area. It is also possible for the penetration depth to be determined on the basis of the damping and at least one user input with regard to the dimensions of the item to be cooked. The penetration depth is an advantageous parameter for controlling the cooking process, since it depends, for example, on the moisture content and temperature of the food to be cooked. The imaginary part of the relative complex permittivity can be calculated from the penetration depth, the known measuring frequency and the real part of the relative complex permittivity determined via the phase velocity in the food. The imaginary part of the relative complex permittivity provides information about the frequency dependency of the absorption of electromagnetic waves in the food to be cooked.

It is possible for at least one contour of the item to be cooked to be determined as a characteristic parameter. For this purpose, the food to be cooked and the transmitting device and/or the receiving device are preferably positioned in a large number of orientations relative to one another. In each of the alignments, measurement radiation is transmitted and/or detected at least once. In particular, at least one wave property and/or transit time of the measurement radiation is recorded at least once in each of the alignments. It is possible for the item to be cooked to be rotated at least partially and preferably completely during the measurements. For example, the food to be cooked can be rotated about a vertical axis. It is possible for the food to be cooked to be arranged on a rotatable support surface. It is also possible that the transmitting device and/or the Emp catching device are moved at least partially and preferably completely around the food to be cooked.

At least one radargram is preferably created. In particular, the intensity of the reflection is recorded as a function of time for each angle of orientation. The data recorded in this way are preferably converted by migration calculations into at least one radar image of the contour of the item to be cooked. Kirchhoff migration and/or intersection-based imaging are preferably used for this purpose. Other migration methods are also possible. The object contour preferably corresponds to a section in the plane of the transmitting device and/or receiving device. The contour of the item to be cooked provides information about the weight and/or the volume of the item to be cooked, for example, and can therefore be used particularly well to determine the cooking time. It is also possible that a three-dimensional shape of the food to be cooked is determined. For example, the contours of several sectional planes of the food to be cooked are determined and offset against each other.

It is possible for at least one reflection diagram and/or transmission diagram to be evaluated by the evaluation device in order to determine a propagation time and/or at least one wave property of the measurement radiation. The reflection diagram and/or transmission diagram is preferably recorded along at least one section and/or area in the cooking chamber. For example, a detection takes place over the surface of the food support. Such an evaluation of reflection and/or transmission diagrams has the advantage that numerous individual and point measurements can be replaced. At least one reflection diagram and/or transmission diagram is preferably evaluated to determine the first and/or second and/or third and/or fourth and/or fifth propagation time and/or amplitude. It is also possible for at least one transit time and/or at least one wave property to be recorded by a point measurement.

For example, a radargram is recorded for this purpose, which describes the reflected power as a function of the transit time in air for a number of points on the route and/or area in the cooking chamber. The distance specified in the radargram then preferably corresponds to a distance from which the respective reflection appears to come if it had only traversed an air gap. It is possible for the radargram to be optimized and, for example, sharpened and/or smoothed using at least one migration method. By evaluating such a radargram, for example by the evaluation device with an appropriate algorithm or appropriate software, the transit times and/or attenuations for the respective areas of the food or food carrier can then be determined. The necessary data is recorded, for example, while the food to be cooked is being pushed into the cooking chamber. The transmitting device and/or receiving device is then preferably positioned in a stationary manner in relation to the cooking chamber. It is also possible for the transmitting device and/or receiving device to be at least partially moved and/or pivoted in order to record the radargram. It is also possible for a plurality of antennas to be distributed in the cooking chamber, through which the measurement radiation emitted by at least one transmission device can be received at different angles.

In all of the configurations, it is preferable for at least one transit time and/or at least one wave property of the measurement radiation to be measured repeatedly during a cooking process. The repeatedly measured running times and/or wave properties are preferably offset against one another to determine the characteristic parameter of the food to be cooked. For example, continuous measurements are provided during the cooking process. At least the first and/or third transit time is particularly preferably measured repeatedly. It is also possible that all transit times are measured repeatedly.

A change in the characteristic parameter of the item to be cooked over time is particularly preferably considered. A change in the propagation times and/or wave properties of the measurement radiation over time is particularly preferably also recorded and used to determine the characteristic parameter. In particular, at least one measurement also takes place before and/or after the cooking process. In addition to reliable monitoring of the cooking process, this also enables an advantageous control of the cooking result.

The cooking appliance according to the invention comprises at least one treatment device for treating food to be cooked in at least one cooking chamber. The cooking appliance comprises at least one measuring system with which at least one characteristic parameter of the item to be cooked can be recorded without contact. The treatment device can be controlled at least partially by at least one control device as a function of the determined parameter.

The measuring system comprises at least one transmission device for generating and emitting electromagnetic measurement radiation into the cooking chamber. The measuring system comprises at least one receiving device for receiving the measuring beam lung. The measuring system comprises at least one evaluation device for evaluating the measurement radiation. In this case, the measuring system is suitable and designed to determine at least a first propagation time of the measuring radiation for at least a first measuring section. The first measuring section extends between the transmitting device and an end face of the item to be cooked that faces the transmitting device. The measuring system is suitable and designed to use at least a second propagation time of the measuring radiation for at least a second measuring section. The second measurement section extends from the transmitting device through a layer of air to a food support on which the food rests. The evaluation device is suitable and designed to determine at least one first difference based on the first and the second transit time. The first difference corresponds to a transit time of the measuring radiation through a layer of air with an at least approximately the same extent as that of the food to be cooked. The evaluation device is suitable and designed to compare the first difference with at least one propagation time of the measuring radiation through the cooking item in order to determine the parameter of the cooking item.

The cooking appliance according to the invention also offers many advantages. A significant advantage is that the cooking device enables a particularly reliable characterization of the food to be cooked. As a result, the treatment device and, for example, a heating device can be adapted to the respective properties of the food to be cooked. In addition, the cooking appliance can monitor the cooking process and reliably recognize the finished cooking point. In addition, the measuring system of the cooking appliance can be implemented using inexpensive radar technology.

The cooking appliance is particularly preferably suitable and designed to be operated according to the method described above. It is possible that the second running time is stored in the evaluation device. It is also possible that the measuring system is suitable and designed to record the second transit time by at least one reflection measurement and/or transmission measurement.

The transmitting device and/or the receiving device are preferably at least partially designed and suitable for processing measurement radiation of at least two different frequencies between 10 megahertz and 100 gigahertz in a frequency bandwidth of at least 10% of the center frequency of the frequency band used. The transmitting device and/or the receiving device are particularly preferably designed and suitable for transmitting or receiving ultra-broadband signals. The processing device is also preferably designed to evaluate ultra-broadband signals. This allows the frequency dependency of the parameters to be measured as well as their time dependency.

The measurement radiation is, in particular, radar radiation. The measurement radiation is preferably emitted in a frequency range from 2.4 GHz to 2.5 GHz with a bandwidth of 0.1 GHz in particular. A frequency range from 57 GHz to 64 GHz with a bandwidth of 7 GHz is also preferred. In particular, the measurement radiation is emitted as an ultra-short pulse.

It is also preferred that the transmission device is at least partially designed and suitable for transmitting measurement radiation as at least one pulse at least intermittently and in particular repeatedly. In this case, the pulse duration is in particular shorter than one nanosecond. The pulse duration is preferably in the hundreds of picoseconds or less.

The measuring system particularly preferably comprises at least one ultra-broadband radar device and/or is designed as such. In particular, the ultra-broadband radar device comprises at least one radar sensor and preferably a frequency-modulated continuous-wave radar sensor.

The ultra-broadband radar device is preferably suitable and designed to transmit and receive ultra-broadband signals. In this case, in particular, an ultra-short pulse can be emitted, which includes the widest possible frequency spectrum according to the corresponding Fourier transformation. The frequency range comprises in particular at least 250 megahertz and preferably at least 500 megahertz and/or at least one gigahertz and/or at least 5 gigahertz and particularly preferably more than 10 gigahertz. Radar information can be generated and evaluated with such an ultra-broadband radar device, so that spectral information with very good resolution is obtained. As a result, the item to be treated can be characterized in a correspondingly precise manner and individual parameters can be spatially allocated and displayed.

A pulse that is narrow in the time domain is assigned to a radar signal that is broadband in the frequency domain: the more broadband in the frequency domain, the narrower the band in the time domain. An extremely narrow bandwidth in the time domain enables the resolution required for small transit time differences of pulses with the speed of light. If the pulse width is of the order of magnitude of the expected runtime differences or if the maximum of the pulse can only be determined with one degree of accuracy because it is so wide or noisy which is in the order of magnitude of the runtime differences, it is not possible to measure the runtime differences with the desired accuracy. Therefore, a certain minimum bandwidth of the radar is required. In addition, the frequency dependency of the parameters can be measured over a wide frequency range. This provides useful additional information.

The treatment device is preferably designed as a thermal heating source and/or a heating device for dielectric heating of items to be treated, or includes such a device.

Further advantages and features of the present invention result from the exemplary embodiments, which are explained below with reference to the enclosed figures.

• 1 eine rein schematische Darstellung eines erfindungsgemäßen Gargerätes mit einem Garraum in einer Vorderansicht;
• 2 eine stark schematische Darstellung eines Gargerätes in einer geschnittenen Vorderansicht; und
• 3 eine stark schematische Darstellung eines Gargerätes mit skizzierten Messabschnitten.

In the figures show:

• 1 a purely schematic representation of a cooking appliance according to the invention with a cooking chamber in a front view;
• 2 a highly schematic representation of a cooking appliance in a sectional front view; and
• 3 a highly schematic representation of a cooking appliance with sketched measurement sections.

The 1 shows a cooking appliance according to the invention from 10, which is designed here as a baking oven 200. The cooking appliance 10 is operated according to the method according to the invention. The cooking appliance 10 is provided here as a built-in appliance. It is also possible for the cooking appliance 10 to be in the form of a cooker or stand-alone appliance. The cooking appliance 10 has a cooking chamber 12 which can be closed by a door 202 . In the cooking chamber 12 there is a product to be cooked 6 on a product support 13. The product support 13 is inserted on a product support receptacle 204 (not visible here).

A treatment device 11 is provided for preparing the food 6 to be cooked. The treatment device 11 comprises a plurality of heating devices 203, of which only one heating device 203 designed as a circulating air heating source can be seen in the view shown here. Various heating devices 203 are available for heating the cooking chamber 12 . Among other things, heating is possible with a circulating air heat source, with top and bottom heat, in hot air mode and/or with a grill function. It is also possible for the oven 200 to be designed as a combination appliance with a microwave function and/or a steam cooking function.

The cooking appliance 10 here includes a control device 14 for controlling or regulating appliance functions. By means of the control device 14, for example, the heat output of the heating devices 203 is set such that temperatures in the cooking chamber 12 are in the range of a required target temperature. Various operating modes and preferably various program operating modes and automatic functions can also be executed via the control device 14 .

The cooking device 10 can be operated here via an operating device 201 . For example, the operating mode, the operating temperature and/or a program operating mode or automatic function can be selected and set. The operating device 201 here includes a display, via which the user is shown information about the operational sequence and the cooking process. The user can also make entries via the operating device 201 , for example to store an insertion height of the food support 13 or information about the food 6 in the cooking appliance 10 . For this purpose, the operating device 201 can have one or more keys and/or be designed as a touch-sensitive surface or touch screen.

The cooking appliance 10 has a measuring system 7 that is shown in a highly schematic manner. The measuring system 7 is provided for the contactless determination of various characteristic parameters of the food 6 to be cooked. The measuring system 7 here comprises a transmitting device 17 and a receiving device 27 as well as an evaluation device 37. Electromagnetic measuring radiation and in particular radar radiation is generated with the transmitting device 17 and sent into the cooking chamber 12. At least part of the measuring radiation interacts with the item to be cooked 6 and is reflected and/or transmitted by it. The reflected and/or transmitted measurement radiation is received again by the receiving device 27 .

In this case, for example, a propagation time of the received measurement radiation is recorded by the measurement system 7 . For example, a characteristic wave property of the received measurement radiation is also detected by the measurement system 7, for example the amplitude, frequency, phase and/or polarization. The measurements relate to propagation times and/or attenuation of the measurement radiation up to the item to be cooked 6, to behind the item to be cooked 6 and through the item to be cooked 6. The measurements are preferably carried out in reflection and/or transmission.

The evaluation device 37 determines from the propagation time and/or from the change in the wave property of the received measurement radiation The characteristic parameters of the item to be cooked 6 are related to the transmitted measurement radiation. The determined parameters are taken into account, for example, by the control device 14 when setting the treatment device 11 or heating device 203 .

In the 2 a cooking appliance 10 is shown in a highly schematic, sectional front view. The measuring system 7 here comprises a transmitting device 17 and a receiving device 27 which are made available by a radar sensor 47 . The radar sensor 47 is part of an ultra wide band radar device.

The radar sensor 47 is preferably a broadband or ultra-broadband radar sensor 47. A large bandwidth enables a high spatial resolution and a small minimum measurement distance, which is particularly advantageous in small cooking chambers 12. The radar sensor 47 is designed here, for example, as an FMCW radar sensor (frequency-modulated CW/continuous wave sensor). The radar sensor 47 preferably has at least one semiconductor component or chip based on silicon and, for example, SiGe for its analog part (front end of the radar sensor 47). Such a radar sensor 47 offers a corresponding measurement accuracy and is particularly inexpensive.

The measuring system 7 and in particular the radar sensor 47 preferably work in a frequency range at a sufficiently large distance below or above the dipole resonances of food. This ensures that the item to be cooked 6 is sufficiently transparent for the measuring radiation and reflection can take place on the outside of the food. Since food 6 usually has a high water content, a preferred frequency range is between 1 GHz and 50 GHz.

The radar sensor 47 particularly preferably works in an internationally approved frequency band. For example, the radar sensor 47 operates with a 0.1 GHz bandwidth in the ISM band from 2.4 GHz to 2.5 GHz. The radar sensor particularly preferably works with a 7 GHz bandwidth in the ISM band between 57 GHz and 64 GHz. The oscillator input is preferably controlled via a voltage. In particular, the radar sensor 47 has at least one I and one Q receiver. The analog part of the radar sensor 47 preferably has an I and a Q output for each independent receiving antenna. Radar sensor 47 preferably measures the position and/or distance and/or angle of food 6 to sensor 47.

The radar sensor 47 preferably includes at least one oscillator, one power amplifier, one low-noise amplifier (at the antenna input), one IF amplifier and AD converter. After the AD converter, the signal is evaluated in the periphery using digital signal processors, FPGA and/or a small CPU. For example, FFT, FFT-1, convolutions, filtering, etc. are provided for this purpose.

The antennas are in particular integrated directly into the chip of the radar sensor 47 or are located on or in the periphery of the chip. The radar sensor 47 can include at least one antenna. The radar sensor 47 can also have at least one transmitting antenna 17 and one receiving antenna 27 . The radar sensor 47 particularly preferably has a transmitting antenna 17 and two independent receiving antennas 27. In this case, the analog part of the radar sensor 47 has four outputs, for example, namely an I and a Q output for each receiving antenna. Such a configuration enables a particularly advantageous spatial resolution for the direction from which the respective measurement radiation comes.

The received measurement radiation or the antenna signals are preferably guided with small wave channels in the form of a rectangle or horn from the chip of the radar sensor 47 to the cooking chamber wall or to the components of the radar sensor 47 provided for evaluation. As a result, a particularly large part of the intensity of the transmitted measurement radiation can be received and evaluated again. In addition, such a connection via corresponding wave channels offers good thermal decoupling of the radar sensor 47 from the cooking chamber components that are heated during operation.

The radar sensor 47 emits the measurement radiation here as ultra-short pulses and is operated according to the principle of an ultra-wideband radar (UWB). Such a pulse includes electromagnetic waves of different frequencies and amplitudes and phase angles. Such ultra-short pulses with a correspondingly wide frequency spectrum offer particularly high measurement accuracy. In addition, such pulses are also advantageous for reliably separating reflections on the cooking chamber walls from the actual measurement signal to be evaluated.

The radar sensor 47 is arranged on an upper side of the cooking chamber 12 here. This is particularly advantageous in the case of a reflection measurement, in which the measurement radiation is reflected on the food support 13 . However, it is also possible to arrange a radar sensor 47 at a different position in the cooking chamber 12. For example, in one embodiment, a radar sensor 47 can be arranged on a side wall of the cooking chamber 12. Such an arrangement is, for example, for non-contact determination determination of the object contour is an advantage. An arrangement of a radar sensor 47 on a lower side of the cooking chamber 12 is also possible.

In one configuration, the measurement system 7 can include one or more receiving antennas 57 . Such a configuration is particularly advantageous for transmission measurements. The signals received by receiving antenna 57 are preferably forwarded to radar sensor 47 .

The 3 shows a cooking appliance 10 in a highly schematic representation. In the cooking chamber 12 there is a food support 13 with a food 6 to be cooked. An end face 16 of the item to be cooked is directed towards the transmitting device 17 of the measuring system 7 on the cooking chamber ceiling. In the representation shown here, measurement sections 1-5 are sketched as arrows, which are described in more detail below.

To determine one or more characteristic parameters of the item to be cooked 6, a transit time measurement is carried out in reflection, for example. The respective measurement radiation is emitted and received by the radar sensor 47 above the item to be cooked 6 . For this purpose, the radar sensor 47 includes corresponding transmitting devices 17 and receiving devices 27. Since the measurements take place here in reflection, the propagation times of the measurement radiation correspond to the double path of the respective measurement section. This is taken into account when evaluating the runtimes.

In this case, a first propagation time of the measurement radiation for a first measurement section through the air from the radar sensor 47 to the end face 16 of the item to be cooked 6 is determined. Here, the measurement radiation is essentially reflected at the end face 16 .

In addition, a second propagation time of the measuring radiation through the air from the radar sensor 47 to the theoretical rear side of the item to be cooked 6 is measured. The measurement radiation is essentially reflected here on the food support 13 . This corresponds here to a transit time along a second measurement section 2, which extends between the radar sensor 47 and the food support 13 on which the food 6 rests. In this case, the measuring radiation does not pass through the item 6 to be cooked, so that the transit time measurement is carried out without the item 6 to be cooked.

Furthermore, a third propagation time of the measurement radiation along a third measurement section 3 is recorded. The third measurement section 3 extends here between the radar sensor 47 and the food support 13 and passes through the food 6 to be cooked.

A first difference is formed here on the basis of the transit times for the first and second measurement sections 1, 2. This first difference corresponds to a running time through an air layer that is geometrically essentially as high as the item 6 to be cooked. A second difference is formed on the basis of the propagation times of the first and third measurement sections 1, 3. This second difference corresponds to a transit time through the item to be cooked 6. The differences describe the transit times of the measuring radiation for a geometric path of the same length in air or in the item to be cooked 6. Due to the different phase velocities in the air and in the item to be cooked 6, the transit times are of different lengths.

Meaningful parameters of the item to be cooked 6 can be determined on the basis of these running times or the first and second difference. For example, the phase velocity of the measuring radiation in the item to be cooked 6 can be determined. Based on the phase velocity, a z. B. statements about the moisture content and the temperature of the food can be made. In addition, statements about the state of aggregation of the water in the cooking item 6 are possible.

The real part ε _r ′ of the relative complex permittivity of the item to be cooked 6 can be determined on the basis of the first and second difference. On the basis of the relative complex permittivity, for example, frozen food 6 to be cooked can be distinguished from non-frozen food—both on the real and on the imaginary part. Therefore, when controlling the treatment device 11, it can be taken into account that the cooking process is preceded by thawing. In addition, the relatively complex permittivity can be used to reliably estimate the type of food to be cooked, for example meat, baked goods or vegetables. In addition, the relatively complex permittivity is observed during the cooking process through continuous measurements, so that changes over time can be registered. For example, the real part of the relative complex permittivity of a dough decreases during the baking process. On the other hand, when preparing vegetables, the real part of the relative complex permittivity increases during the cooking process. In the imaginary part, the frequency shifts for the extreme value of the dipole polarization. Thus, based on the direction of the change over time during the cooking process, a conclusion can be drawn about the type of food 6 to be cooked.

An insertion height of the food support 13 in the cooking chamber 12 is preferably also determined on the basis of the second running time. The distance between the food support 13 and the radar sensor 47 is determined from the second running time and the ver turned insertion position. Knowing the shelf height, for example, a specifically adapted distribution of top to bottom heat can be made.

Knowing the first difference, a geometric dimension 36 of the item to be cooked 6 can be determined. This dimension corresponds here to the height 36 of the item to be cooked 6. Knowing the height 36 of the item to be cooked 6, the required cooking time can be determined. In this way, for example, a minimum and/or a maximum cooking time can be defined, so that operating errors due to cooking times that are too short or too long can be reliably avoided.

The second running time for the second measuring section 2 is measured, for example, at the start of the cooking process. The second running time can also be determined by a user input regarding the insertion height of the food support 13 . It is also possible for the user to be prompted to insert the food support 13 at a specific insertion height. Corresponding running times and/or distances are preferably stored in the evaluation device 37 for the respective insertion heights. In this way, the second runtime can be reliably determined based on the insertion height, without the need for a measurement. The first running time and the third running time are repeated during the cooking process and are preferably monitored continuously. The second running time can also be determined continuously.

The second running time for the second measurement section 2 is preferably measured while the food support 13 is being pushed into the cooking chamber 12 . The measurements are preferably carried out continuously. If the radar sensor 47 is arranged, for example, on the ceiling of the cooking chamber 12, the first measured values are recorded in the cooking chamber 12, which is still empty, so that the running time to the cooking chamber floor is measured. The transit time measurement to the cooking chamber floor or to a side of the cooking chamber 12 opposite the transmitting device 17 can be used, for example, to calibrate the measuring system 7 .

If the food support 13 enters the measuring field of the radar sensor 47, the second running time up to the food support 13 is measured. If the food support 13 is now pushed in further, the food 6 also enters the measuring range of the radar sensor 47. The first running time and/or the third running time can now be recorded. Such an embodiment enables, with a fixedly positioned radar sensor 47, the detection of transit times along the insertion path.

In this way, for example, the maximum height 36 of the item to be cooked 6 can also be recorded when it is pushed in. In order to determine parameters other than the maximum height 36 of the item to be cooked 6, a runtime measurement can be carried out at another point of the item to be cooked 6 of any height if the geometric extent dimension 36 is determined or known for this point. For this purpose, the measurement sections 1, 3 used to form a difference preferably lie along a common alignment line.

Measuring sections at different positions in the cooking chamber 12 can also be measured by arranging two or more radar sensors 47 . For example, the second measurement section can then be measured with a radar sensor 47 and the first and/or the third measurement section can be measured with another radar sensor 47 . In addition, the maximum height 36 of the item to be cooked 6 can be determined by using a runtime of that sensor 47 which has recorded the runtime at the highest point of the item 6 to be cooked.

A radar sensor 47 with a plurality of receiving antennas 57 offers another possibility for detecting different areas of the cooking chamber 12. For example, the receiving antennas 57 can be arranged to form an antenna array. The respective reception antennas 57 are addressed in a phase-controlled manner in such a way that the transmission lobe is pivoted in such a way that the food support 13 and/or the food 6 to be cooked are scanned. The transmission angles at which the item to be cooked 6 is optimally detected are preferably used for the subsequent measurements.

The measuring system 7 is also used here to measure the attenuation of the measuring radiation. For this purpose, the amplitude of the measurement radiation is recorded and evaluated. In order to determine the damping as a characteristic parameter of the item to be cooked 6, the amplitudes along the second and third measurement sections 2, 3 are compared with one another. When evaluating a reflection measurement, the double passage of the item to be cooked 6 is correspondingly taken into account.

On the basis of the damping detected, knowing the geometric dimension 36 of the item to be cooked 6, e.g. B. the penetration depth of the measuring radiation in the cooking product 6 is determined as a characteristic parameter. The penetration depth is preferably monitored during the cooking process, since information about the change in moisture content and cooking temperature can be derived in this way. From the penetration depth or damping, the measuring frequency and the real part of the relative complex permittivity er' determined via the phase velocity in the food to be cooked Imaginary part er'' of the relative complex permittivity is calculated.

A runtime delay as a function of the dimension 36 of the item to be cooked 6 can also be determined as a further parameter. For this purpose, for example, the first and second differences are put into a ratio. The second difference corresponds to the running time in the item to be cooked 6 and the first difference to the dimension or height 36 of the item to be cooked 6 at the respective measuring point.

The measuring system 7 can preferably also be used for transmission measurements. For this purpose, a food support 13 is preferably used, which is at least partially transparent to the measuring radiation. In this arrangement of the measuring system 7, a transmission device 17 and/or a radar sensor 47 is/are preferably arranged on the ceiling of the cooking chamber 12. A corresponding receiving antenna 57 or receiving device 27 is then provided on the opposite side in the cooking chamber 12 . In particular, receiving antennas 57 are provided on the ceiling and the floor of the cooking chamber 12, the signals from which are routed to the radar sensor 47. Such a transmission measurement is advantageous when the path to and from the item to be cooked 6, which is required for a reflection measurement, weakens the measurement radiation too much.

The propagation times and other wave properties, such as the amplitude, are then determined using the measurement radiation recorded in transmission. To determine the transit time through the item to be cooked 6, for example, the transit time along a fourth measurement section 4 is first determined. The fourth measurement section 4 extends from the radar sensor 47 to the receiving antenna 57 and through the objects lying in between, such as the food support 13. The food to be cooked 6 is not passed through. The transit time along a fifth measurement section 5 is then recorded in a further measurement. This measuring section 5 extends through the same objects as the fourth measuring section, but also runs through the item to be cooked 6. The running time through the item to be cooked 6 can thus be determined using the difference in the running times of the fourth and fifth measuring section.

The damping can also be determined in a corresponding manner. The amplitudes of the measurement radiation recorded via the measurement sections 4 and 5 are set in relation to this. The various parameters are then determined on the basis of the propagation times or attenuations measured in transmission, such as the phase velocity in the food to be cooked 6, the relative complex permittivity of the food to be cooked 6 with its real and imaginary parts and/or the penetration depth into the food to be cooked 6.

The determined parameters of the item to be cooked 6 can be integrated into the operation of the cooking appliance 10 in the form of suggestions. For example, the information about the operating device 201 can be displayed in the form of plain text and/or symbols. For example, after the determination of at least one parameter, the cooking device 10 can make suggestions for a specific operating mode, a cooking time and/or an automatic program. In addition, it is possible for limitations to be specified, for example for the selectable cooking chamber temperature and/or a minimum or maximum cooking time.

reference list

1

measurement section

2

measurement section

3

measurement section

4

measurement section

5

measurement section

6

food

7

measuring system

10

cooking appliance

11

treatment facility

12

cooking chamber

13

food carrier

14

control device

16

face

17

transmission device

26

rear

27

receiving device

36

dimension, height

37

evaluation device

47

radar sensor

57

receiving antenna

200

oven

201

operating device

202

door

203

heating device

204

Food carrier holder

Claims (19)

Method for operating a cooking appliance (10) with at least one treatment device (11) for treating food (6) in at least one cooking chamber (12), wherein at least one characteristic parameter of the food (6) to be cooked is recorded without contact using at least one measuring system (7). and wherein the treatment device (11) is at least partially controlled as a function of the determined parameter and wherein, for this purpose, electromagnetic measuring radiation, preferably in a frequency band, is generated with at least one transmitting device (17) and introduced into the cooking chamber (12) and with at least one receiving device (27) is received and evaluated, characterized in that for at least some frequencies of the frequency band, a first propagation time of the measurement radiation is determined for at least a first measurement section (1), which extends between the transmission device (17) and an end face (16 ) of the food to be cooked (6) and that at least a second propagation time of the measurement radiation is used for at least a second measurement section (2), which extends from the transmitting device (17) through a layer of air to a food support (13) on which the food to be cooked ( 6) and that on the basis of the first and the second transit time at least a first difference is determined, which corresponds to a transit time of the measuring radiation through a layer of air with an at least approximately the same extent as that of the cooking item (6) and that to determine the parameter of the cooking item ( 6) the first difference is compared with at least one transit time of the measurement radiation through the item to be cooked (6). procedure after claim 1 , characterized in that at least a third propagation time of the measuring radiation is determined for at least a third measuring section (3), which extends from the transmitting device (17) through the item to be cooked (13) to a rear side (26) facing away from the transmitting device (17). of the item to be cooked (6) and that at least one second difference is determined on the basis of the first and third runtime, which difference corresponds to the runtime of the measuring radiation through the item (6) to be cooked. Method according to one of the preceding claims, characterized in that at least a fourth propagation time of the measuring radiation is determined for at least a fourth measuring section (4) which extends at least through the food to be cooked (6) and through a food support (13) on which the food to be cooked (6) and that at least a fifth runtime of the measurement radiation is determined for at least a fifth measurement section (5), which corresponds to the fourth measurement section without food to be cooked (6) and that at least a third difference is determined based on the fourth and fifth runtime, which Term of the measurement radiation through the food (6) corresponds. Method according to one of the preceding claims, characterized in that the second running time is detected by at least one measurement with the measuring system (7) and/or that the second running time is determined based on an insertion position of the food support (13) in the cooking chamber (12). Method according to one of the preceding claims, characterized in that at least one geometric dimension (36) of the food (6) to be cooked is at least approximately determined as a characteristic parameter using a product of the first difference and a phase velocity of the measuring radiation in air and/or vacuum. Method according to one of the preceding claims, characterized in that the first measuring section (1) extends to a highest area on the end face (16) of the cooking item (6) and/or that the first measuring section (1) extends to a central area of the End face (16) of the food (6) extends. Method according to one of the preceding claims, characterized in that a plurality of first running times are determined and that the first measuring sections (1) extend to different points on the end face (16) of the cooking item (6) and that the first running times recorded in this way correspond to one another are compared, so that the shortest distance between the transmitter (17) and the item to be cooked (6) can be determined based on the shortest runtime. procedure after claim 2 , characterized in that at least one phase velocity of the measuring radiation in the cooking product (6) is determined on the basis of the first and second difference as a characteristic parameter of the cooking product (6). procedure after claim 2 , characterized in that at least one real part of the relative complex permittivity of the cooking item (6) is determined as a characteristic parameter of the cooking item (6) and in that the first and the second difference are related to this. Method according to one of the preceding claims, characterized in that as a characteristic parameter an insertion position of the food (6) in the cooking chamber (12) based on a product of the second running time and a phase speed of the measurement radiation in air and/or vacuum is at least approximately determined. Method according to one of the preceding claims, characterized in that at least one amplitude of the measurement radiation is detected after passing through the item to be cooked (6) at least once and in that the amplitude is compared with an amplitude of the measurement radiation recorded under comparable conditions without the item to be cooked (6) and that the amplitudes are set in a ratio to each other, which corresponds to the attenuation of the measurement radiation by the cooking item (6). Method according to the preceding claim, characterized in that at least one penetration depth of the measuring radiation into the cooking item (6) is determined as a characteristic parameter on the basis of the attenuation and a geometric dimension (36) of the cooking item. Method according to the preceding claim, characterized in that as a characteristic parameter of the cooking item (6) at least one imaginary part of the relative complex permittivity of the cooking item (6) is determined and that the Method according to one of the preceding claims, characterized in that at least one contour of the item to be cooked (6) is determined as a characteristic parameter and that for this purpose the item to be cooked (6) and the transmitting device (17) and/or the receiving device (27) in a plurality of Alignments are positioned to each other and that in each alignment at least once measurement radiation is sent and detected. Method according to one of the preceding claims, characterized in that to determine at least one transit time and/or at least one wave property of the measuring radiation, at least one reflection diagram and/or transmission diagram is evaluated, which was recorded along at least one route and/or area in the cooking chamber (12). . Method according to one of the preceding claims, characterized in that during a cooking process at least one transit time and/or at least one wave property of the measuring radiation is repeatedly measured and used to determine the characteristic parameter of the item to be cooked (6). Method according to one of the preceding claims, characterized in that the parameters to be recorded are determined before and/or during a cooking process at least at one frequency and preferably at a plurality of frequencies distributed over the widest possible frequency band. Cooking appliance (10) with at least one treatment device (11) for treating the food (6) to be cooked in at least one cooking chamber (12), wherein at least one characteristic parameter of the food to be cooked (6) can be recorded without contact using at least one measuring system (7) and the treatment device (11) can be controlled at least partially as a function of the determined parameter by at least one control device (14), and the measuring system (7) has at least one transmitting device (17) for generating and emitting electromagnetic measuring radiation into the cooking chamber (12) and at least one receiving device ( 27) for receiving the measurement radiation and at least one evaluation device (37) for evaluating the measurement radiation, characterized in that the measurement system (7) is suitable and designed for this, at one or more frequencies, in each case at least a first transit time of the measurement radiation for at least a first to determine the measuring section (1) which extends between the transmitting device (17) and an end face (16) of the item to be cooked (6) facing the transmitting device (17) and to use at least a second propagation time of the measuring radiation for at least a second measuring section (2), which extends from the transmitting device (17) through a layer of air to a food support (13) on which the food (6) is lying and that the evaluation device (37) is suitable and designed for this, based on the first and the second running time, at least a first difference, which corresponds to a transit time of the measuring radiation through a layer of air with at least approximately the same extent as that of the item to be cooked (6) and that the evaluation device (37) is suitable and designed to determine the parameter of the item (6) to be cooked, the first Compare difference with at least one term of the measurement radiation through the food (6). Cooking appliance (10) with at least one treatment device (11) for treating the food (6) to be cooked in at least one cooking chamber (12), wherein at least one characteristic parameter of the food to be cooked (6) can be recorded without contact using at least one measuring system (7) and the treatment device (11) can be controlled at least partially as a function of the determined parameter by at least one control device (14), and the measuring system (7) has at least one transmitting device (17) for generating and emitting electromagnetic measuring radiation into the cooking chamber (12) and at least one receiving device ( 27) for receiving the measurement radiation and at least one evaluation device (37) for evaluating the measurement radiation, characterized in that the measuring system (7) is suitable and designed such that at least one amplitude of the measuring radiation is detected at one or more frequencies after the item to be cooked (6) has been passed through at least once, and that the amplitude is measured with a Cooking item (6) is compared under comparable conditions detected amplitude of the measuring radiation and that the amplitudes are set in a ratio to each other, which corresponds to the attenuation of the measuring radiation by the cooking item (6).

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