Induction heating apparatus

1. An induction heating apparatus, comprising:

a top plate for placing an object to be heated thereon;

a heating coil adapted to generate an induction magnetic field for heating the object;

a control portion adapted to control a high-frequency electric current applied to the heating coil for heating the object; and

an infrared-ray detection portion adapted to detect an infrared ray radiated according to a temperature of the object and to output an infrared-ray detection signal according to infrared-ray energy of the detected infrared ray;

wherein the infrared-ray detection portion includes:

an infrared-ray reception portion adapted to output a detection signal, when receiving an infrared ray radiated from the object,

an amplification portion adapted to amplify the detection signal from the infrared-ray reception portion and output the infrared-ray detection signal, and

a temperature detection portion adapted to detect a temperature of the infrared-ray reception portion and to output the detected temperature to the control portion, and

wherein the control portion includes a correction portion adapted to correct the infrared-ray detection signal and output an infrared-ray real signal by using negative-signal information about a negative signal, which is superimposed on the infrared-ray detection signal output from the infrared-ray detection portion, and which has a reverse polarity from that of the infrared-ray detection signal, and the negative-signal information is generated in response to the temperature of the infrared-ray reception portion, when the temperature of the infrared-ray reception portion is equal to or higher than the temperature detected by the infrared-ray detection portion.

2. The induction heating apparatus according to claim 1 , wherein the control portion includes a temperature-characteristic storage portion adapted to preliminarily store the negative-signal information indicative of a temperature characteristic regarding the negative signal and the temperature of the infrared-ray detection portion, and

the correction portion is adapted to correct the infrared-ray detection signal by using the negative-signal information generated on basis of the temperature characteristic indicated by the negative-signal information stored in the temperature-characteristic storage portion, and the temperature of the infrared-ray reception portion is detected by the temperature detection portion.

3. The induction heating apparatus according to claim 1 , wherein the control portion includes a sensitivity-characteristic storage portion adapted to preliminarily store the negative-signal information indicative of a sensitivity characteristic regarding the negative signal and a cutoff wavelength or a spectral sensitivity wavelength of the infrared-ray reception portion, and

the correction portion is adapted to correct the infrared-ray detection signal based on the sensitivity characteristic indicated by the negative-signal information.

4. The induction heating apparatus according to claim 1 , wherein the control portion is adapted to correct an input offset voltage signal contained in the infrared-ray detection signal.

5. The induction heating apparatus according to claim 1 , wherein the infrared-ray detection portion is adapted to superimpose a constant reference voltage on the detection signal output from the infrared-ray reception portion.

6. The induction heating apparatus according to claim 1 , further comprising a light interception portion adapted to prevent the infrared-ray reception portion from receiving an infrared ray radiated from the object,

wherein the control portion includes:

a changeover portion adapted to manipulate the light interception portion for changing over between reception of an infrared ray radiated from the object by the infrared-ray reception portion and interception of the infrared ray, and

a correction portion which is adapted to detect the negative signal superimposed on the infrared-ray detection signal, based on an output difference between an output signal from the infrared-ray reception portion, when the infrared-ray reception portion receives an infrared ray radiated from the object and an output signal from the infrared-ray reception portion when an infrared ray radiated from the object is intercepted and is adapted to correct the infrared-ray detection signal based on the detected negative signal, when the temperature of the infrared-ray reception portion is equal to or higher than a temperature detected by the infrared-ray detection portion.

7. The induction heating apparatus according to claim 1 further comprising:

a first infrared-ray reception portion adapted to detect an infrared ray radiated from the object according to the temperature of the object and is adapted to output an infrared-ray detection signal according to infrared ray energy of the detected infrared ray,

a second infrared-ray reception portion near the first infrared-ray reception portion, that is shielded in such a way as to be prevented from receiving an infrared ray radiated according to the temperature of the object and is adapted to output a dark signal, and

a correction portion which is adapted to detect the negative signal superimposed on the infrared-ray detection signal, based on an output difference between an infrared-ray detection signal from the first infrared-ray reception portion and the dark signal from the second infrared-ray reception portion and to correct the infrared-ray detection signal based on the detected negative signal when the temperature of the infrared-ray reception portion is equal to or higher than a temperature detected by the infrared-ray detection portion.

8. The induction heating apparatus according to claim 1 , wherein the infrared-ray detection portion is further adapted to condense, by a Fresnel lens, an infrared ray radiated from the object and to output a detection signal from the infrared-ray reception portion.

9. The induction heating apparatus according to claim 1 , wherein the infrared-ray detection portion is under the top plate and is adapted such that an infrared ray radiated from the object is incident to the infrared-ray detection portion through the top plate, and the incident infrared ray is condensed by a Fresnel lens having a different transmittance characteristic from that of the top plate, and a detection signal is output from the infrared-ray reception portion.

10. The induction heating apparatus according to claim 1 , wherein the infrared-ray detection portion is on the top plate and is adapted such that an infrared ray radiated from the object is incident to the infrared-ray detection portion, the incident infrared ray is condensed by a Fresnel lens, and a detection signal is output from the infrared-ray reception portion.

11. The induction heating apparatus according to claim 1 , wherein the infrared-ray detection portion is adapted such that an infrared ray radiated from the object is incident to the infrared-ray detection portion, the incident infrared ray is condensed by a Fresnel lens, and a detection signal is output from the infrared-ray reception portion, and the Fresnel lens is made of a resin.

12. The induction heating apparatus according to claim 1 , wherein the infrared-ray detection portion is adapted such that an infrared ray radiated from the object is incident to the infrared-ray detection portion, the incident infrared ray is condensed by a Fresnel lens and, a detection signal is output from the infrared-ray reception portion, and the Fresnel lens has a thickness of 1 mm or less.

13. The induction heating apparatus according to claim 1 , wherein the infrared-ray detection portion is of a quantum type.

14. The induction heating apparatus according to claim 1 , wherein the infrared-ray detection portion is adapted to have sensitivity to temperatures of 100° C. or less.

15. The induction heating apparatus according to claim 1 , wherein the infrared-ray detection portion has a maximum sensitivity wavelength in the range of 1.9 to 2.0 μm and is adapted to detect the temperature of the object when the object is at a temperature equal to or higher than 60° C.

16. The induction heating apparatus according to claim 1 , wherein the infrared-ray detection portion has a maximum sensitivity wavelength in the range of 1.5 to 1.6 μm and is adapted to detect the temperature of the object when the object is at a temperature equal to or higher than 140° C.

17. The induction heating apparatus according to claim 1 , wherein the infrared-ray detection portion is adapted such that an infrared ray radiated from the object is incident to the infrared-ray detection portion, the incident infrared ray is condensed by a Fresnel lens, and a detection signal is output from the infrared-ray reception portion, and the Fresnel lens includes a reflection reducing portion for reducing reflection of the infrared ray.