JP4663433B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus such as a printer or a copying machine, and in particular, the type, quality, and printing state of a recording medium on which an image is formed, such as paper, is determined by sensing using high-frequency electromagnetic waves. The present invention relates to an image forming apparatus for setting image forming conditions.

Conventionally, in image forming apparatuses such as copying machines, ink jet printers, and laser printers, setting of image forming conditions (setting of printing operation conditions, etc.) so that an optimal image can be formed according to a recording medium (printing medium) to be printed. It is carried out. In that case, a person who has installed a printing medium, specifically, plain paper, glossy paper, OHP paper, etc. in the apparatus mostly sets the paper type for the apparatus by operating a button.

In this case, when an operation for setting the paper type is wrong, a desired image is not formed, or in some cases, printing is performed again, so that the image forming efficiency is reduced or paper or ink is wasted.

In order to solve this, there has been proposed an image forming apparatus that automatically sets a printing operation condition, an image forming operation, and the like by discriminating the type and state of paper using electromagnetic waves (Patent Document 1 and Patent). Reference 2). Further, there has been proposed a medium information sensing device that propagates electromagnetic waves in a space and senses through detection of the surface or internal image information of an overlapped object and an image forming apparatus using the same (see Patent Document 3). ).
JP 2000-171416 A JP 2001-13088 A JP 2005-78464 A

However, the proposed examples of Patent Document 1 and Patent Document 2 relate to a transmission type paper type detection device that detects using electromagnetic waves transmitted through paper. In recent years, with the miniaturization of devices such as copying machines, various devices are also required to be miniaturized, and the installation space is limited. In such a situation, it is necessary to arrange an electromagnetic wave generation device and an electromagnetic wave detection device so that paper is sandwiched between transmissive paper type detection devices, and it is considered that the place where the device can be installed is limited. It is done. As a result, it is considered that the type and state of the paper cannot be detected at a desired location, and a higher-definition image may not be obtained. The proposed example of Patent Document 3 detects the state of a laminated object using electromagnetic waves, but is different from an apparatus that sets image forming conditions for an object based on the detection result.

In view of the above problems, an image forming apparatus of the present invention includes a generation unit for generating an electromagnetic wave having a frequency in the terahertz region, a detection unit for detecting the electromagnetic wave reflected by a stacked recording medium, and the recording Acquires information for detecting the type of the recording medium by monitoring a signal obtained from the reflected electromagnetic wave obtained by using the detection unit and a storage unit for previously storing information for detecting the type of the medium and, by the storage unit and the acquired information is compared with the information stored, anda calculation unit for detecting a type of the recording medium, information for detecting a type of the recording medium It is seen containing a rate and propagation delay intensity of pulses the signal has to decrease, the calculation unit, by counting the pulses the signal has, the thickness of the stacked recording medium The It acquires the position of each said recording medium relating to direction, and detects a type of the recording medium for each pulse the signal has.

According to the above-described image forming apparatus of the present invention, since the reflected electromagnetic wave from the recording medium on which the image is formed is used, an image forming apparatus that can reduce the restriction on the installation space of the apparatus and can set the installation place relatively flexibly it can.

Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described. In this embodiment, the electromagnetic wave irradiation means irradiates a recording medium such as a printing medium with a high frequency electromagnetic wave in a frequency range of 30 GHz to 30 THz. This electromagnetic wave is a continuously generated electromagnetic pulse having a half width of 10 ⁻¹² seconds or less and including the Fourier spectrum in the frequency range, or a continuous high coherence electromagnetic wave having a single frequency in the frequency range. . The detecting means detects a reflected electromagnetic wave whose propagation state has changed due to reflection of the recording medium. On the other hand, the storage means, though data of the reflected electromagnetic wave from a recording medium in which the propagation state is changed due to the state of the various recording media are stored, determination means, is the detected and the stored data The state of the recording medium irradiated with the electromagnetic wave is determined by comparing with the detection data of the reflected electromagnetic wave. The setting means automatically sets the image forming conditions for the recording medium automatically and optimally based on the determination.

The discriminating means discriminates the type of the recording medium by the comparison using the detection data of the reflected electromagnetic wave at the interface of the recording medium, or the reflected electromagnetic wave data whose propagation state has changed due to the reflection of the image formed portion of the recording medium. The state of the image-formed portion is determined by comparison with the stored data. When a plurality of recording media on which an image is formed are stacked, the determining means determines the type of each recording medium by the comparison using the detection data of the reflected electromagnetic wave component at the interface of each recording medium, and the setting means Based on this determination, the image forming conditions for each recording medium can be set automatically and optimally. When the determination unit determines the state of the image-formed part by the comparison, the setting unit automatically sets the image forming conditions for the image-formed part automatically and optimally in real time based on this determination.

In the present embodiment, an electromagnetic wave that includes a Fourier frequency in the millimeter wave to terahertz region (30 GHz to 30 THz) is used as an electromagnetic wave for reading the state of the recording medium. By using electromagnetic waves in the terahertz region, it is possible to propagate in the thickness direction due to the high transparency of sheet-like paper and plastics, which are printing media, and reflection, propagation delay, etc. due to changes in the dielectric constant of the substance Therefore, information corresponding to the state or properties of the recording medium can be easily obtained.

Information on the state or property of paper or the like can be identified and distinguished as changes in the delay time, amplitude, waveform, etc. of the electromagnetic wave reflected at the interface of the sheet-like medium when the reflected electromagnetic wave is used. When the sheet-like medium is laminated and an electromagnetic wave pulse is used, the detection of the location in the thickness direction of the sheet-like medium can be performed by observing the reflected echo of the emitted electromagnetic wave. If a pulse with a half-value width of about 0.4 psec is used as the electromagnetic wave and the pulse can be separated to half of the pulse width, the distance d corresponding to the delay time τ of 0.2 psec is as follows from the following equation: I want.
d = τc / 2 (c: speed of light) (1)
That is, since d = 30 μm is obtained, it is possible to read information on the state or properties of even a thin sheet of medium thickness such as this one by one. In this way, it is possible to inspect the type of each sheet of about 30 μm in the thickness direction. Information on the location in the thickness direction can be read by sweeping the delay circuit as will be described in an embodiment described later.

When the electromagnetic wave is a continuous electromagnetic wave having a single frequency in the frequency range, the detector side performs mixing with the received signal using the oscillation side electromagnetic wave as a reference wave, performs waveform analysis by Fourier transform, and records Changes in the propagation state of the reflected electromagnetic wave from the medium with respect to the reference wave are detected. Means such as interference measurement may be used as the waveform analysis. In the case of electromagnetic waves from a laminated recording medium, a plurality of electromagnetic waves whose phases are shifted according to the number of recording media are mixed with the reflected electromagnetic waves. The reference wave is shifted to make a reference wave, each reference wave and the received signal are mixed, and a waveform analysis is performed by Fourier transform to detect a change in the propagation state of the electromagnetic wave from each recording medium. Also in this case, means such as interference measurement may be used as the waveform analysis. In addition to paper and plastic, the recording medium may be paper or plastic on which printing or image formation has already been performed. The state of electromagnetic waves also changes depending on the state of adhesion of ink or toner, and by detecting this, more accurate image formation becomes possible.

Embodiments of the image forming apparatus of the present invention using high-frequency electromagnetic waves will be described below with reference to the drawings. However, materials, structures, devices, systems, etc. are not limited to those listed here.

Example 1
Example 1 of the present invention will be described. In the image forming apparatus according to the first exemplary embodiment, the type of a printing medium that is a recording medium such as a plurality of sheets is determined, and an image forming condition for the medium is optimally set based on the result. The principle of the apparatus of this embodiment will be described with reference to FIGS. Consider a case in which the type is determined in a state where a plurality of print media as sheet-like objects 1 are stacked as shown in FIG.

The medium information sensing unit 5 including the electromagnetic wave transmission / reception unit of the image forming apparatus includes an electromagnetic wave pulse generator 6, an antenna 7 that emits the electromagnetic wave pulse 14 to the space, an antenna 9 that receives the reflected pulse 15 from the sheet-like medium 1, and a detector. 8. A delay unit 10 that delays the generation timing of pulses from the generator 6, a mixer 11 that mixes the delayed transmission pulse and reception pulse, and the distance of each sheet-like medium 1 is actually identified based on the delay time τ. An arithmetic unit 12 is provided that outputs a signal relating to the setting of the image forming condition by distinguishing the type and determining the type. In addition, a storage unit 13 that stores data on changes in propagation state such as a waveform change of an electromagnetic wave pulse due to reflection of plain paper, color copy paper, glossy paper, OHP sheet, or the like, which is the sheet-like medium 1, is a calculation unit 12. Can be accessed randomly. These can be integrated or integrated in one housing, but not all of them are necessarily housed in one.

As for the output of the mixer 11, the maximum output can be obtained when the timing of the received pulse coincides with the signal obtained by delaying the transmission pulse. Accordingly, by monitoring the output while sweeping and controlling the delay amount by the delay unit 10 by the arithmetic unit 12, the propagation delay time of the electromagnetic wave is identified and the distance to each sheet-like medium 1 and the received waveform from it are detected. The type can be discriminated with reference to data from the calculation unit 12. At this time, a known synchronous detection technique may be used in which the output of the electromagnetic wave pulse from the generator 6 is varied at a low frequency of the order of 100 kHz and the output of the mixer 11 is further extracted as a mixing output with the low frequency signal.

The computing unit 12 further generates a signal relating to the setting of the printing operation condition for each sheet-like medium 1 based on the discrimination of the type and outputs it to the image forming unit 2 as appropriate. In the image forming unit 2, a printing operation condition is set or reset based on a signal from the computing unit 12, and a printing operation is performed on each sheet-like medium 1. Printing operation conditions include ink ejection pressure from nozzles, printing speed, distance between printing media and nozzles for inkjet printers, etc., and fixing of toner to printing media for laser beam printers and copiers, etc. There are temperature, fixing pressure, applied voltage to the drum, and the like.

In the above configuration, the electromagnetic pulse generator 6 and the antenna 7 correspond to the electromagnetic wave irradiation means, the antenna 9, the detector 8, the delay device 10 and the mixer 11 correspond to the detection means, and the storage unit 13 corresponds to the storage means. The arithmetic unit 12 corresponds to a determination unit and a setting unit. The setting unit may be provided on the image forming unit 2 side without the function of the setting unit from the computing unit 12 side.

An example of a method for detecting the type of each sheet-like medium 1 from the reflected pulse 15 reflected from the sheet-like medium such as paper will be described with reference to FIG. Assuming that the transmitted pulse 14 at a certain time has a time waveform as indicated by reference numeral 21, the reflected pulse is reflected at the interface of the stacked sheet-like medium 1 and a plurality of reflected echo pulses are received by the detector 8. If the thickness of the sheet is d, the electromagnetic wave reflected at the front and back interfaces of the sheet propagates through the space at the speed of light c.
τ = 2d / c (2)
The time difference is caused by the time τ determined by (actually increases by √e according to the dielectric constant e of the sheet-like medium). Due to absorption and reflection loss in the sheet-like medium 1, a plurality of pulses 22 and 23 indicating reflection from each of the stacked sheets are observed while the pulse intensity gradually decreases as shown in FIG. The Then, by pulse counting, it is possible to know what number of sheet-like medium 1 is being viewed from the surface on which the electromagnetic wave 14 is incident.

In order to observe such an echo pulse, real-time observation is difficult for high-speed pulses of the order of picoseconds, so sampling measurement is performed, and the entire waveform is traced while sweeping the delay time as described above. To obtain information on each part in the stacking direction on the order of msec.

For example, when a print medium is set in a printer, the same type is often used, and the magnitude of the reflected echo pulse is indicated by reference numeral 24 in FIG. 2 due to the absorption of electromagnetic waves in each print medium 1. It decreases monotonously. The pulse interval is determined by the dielectric constant and thickness of the printing medium 1. If the reduction rate is determined by exp (−αL) [L is the propagation distance of electromagnetic wave] including the absorption coefficient α of the medium material, the print medium is compared with the data stored in the storage unit 13 in advance. Can be specified. Further, the propagation delay amount τ per sheet determined by the thickness of the print medium 1 and the dielectric constant ε is also used for identification of the print medium by comparing with the memory data. Furthermore, if there is absorption at a specific frequency, the print medium 1 can be identified as a change in the pulse waveform. Thus, since the type of the print medium is detected by combining a plurality of parameters, the identification sensitivity can be improved.

For example, as shown in FIG. 3, recycled paper and color copy paper have substantially the same absorption rate per sheet, but propagation delays are 0.16 psec per plain paper and 0.19 per color copy paper. psec is different. This makes it possible to distinguish between recycled paper and color copy paper. Since the absorption rate and propagation delay vary depending on the paper quality (thickness, density, weighing, moisture, etc.), it may be stored in a database in advance. When there are many parameters, it may be used together with a means for manually inputting in advance.

On the other hand, in the case where media of different quality are mixed in the set medium, for example, it can be distinguished from the fact that the pulse intensity changes extremely as in the received pulse 22 of FIG. In comparison, the type of the medium 1 can be determined from the absorption coefficient. That is, if the delay amount is different, it can be determined as a difference in pulse position, and if the pulse shape is different, it can be determined as a difference in spectrum, which may be used in combination. Then, at the time of printing each sheet-like medium 1, a signal relating to the setting of the printing operation condition for each sheet-like medium 1 is output to the image forming unit 2 based on this type discrimination.

Although the width of the electromagnetic wave pulse 21 necessary for reading is determined by the thickness of the sheet-like medium 1, it is about 100 μm in the case of ordinary paper.

Next, an example of a control method of the printer apparatus which is an image forming apparatus will be described with reference to the flowchart of FIG. When a print command is issued (step 401), the medium information sensing unit 5 of this embodiment sequentially compares the reflected pulse data from the surface of the necessary print medium 1 provided in the cassette with the database in the storage unit 13. Then, the quality of each print medium is determined (step 402). The determination result is stored in the buffer memory in the arithmetic unit 12 while incrementing the number of pieces of information being viewed by the pulse count (step 403). In this way, a plurality of pieces of information on the print medium before printing are stored in the memory, but information on the print medium 1 immediately before output from the cassette is transferred from the memory to the image forming unit 2, and the image forming conditions of the image forming unit 2 Printing (execution voltage, fixing temperature, etc.) is controlled under optimum conditions for the print medium 1 (step 404). Thereafter, if there are one or more remaining sheets, the number of sheets to be output next from the cassette is fed back to the buffer memory and the reflected pulse measurement system, and these are refreshed as appropriate (step 405). Thus, this loop is repeated until the desired printing process is completed (step 406).

In this type of control, the information of the print medium 1 stored in the cassette can be sequentially acquired from the front surface, so that the control time until print control (setting of image forming conditions) can be increased. Since the conventional print medium inspection apparatus can measure only one sheet at a time, it is necessary to measure the print medium in the transport system immediately before printing, and it is necessary to increase the response speed for setting the image forming conditions. In addition, since the conventional print medium inspection apparatus uses the transmitted electromagnetic wave from the print medium, it is necessary to arrange the apparatus with the print medium interposed therebetween, and the installation space of the apparatus is limited.

In order to perform electromagnetic wave transmission / reception using such a short pulse, a method in which the photoconductive elements 41 and 44 are irradiated with a pulse laser as shown in FIG. 5 is preferably used. The photoconductive elements 41 and 44 have the following structure. In this structure, 1.5 μm of non-doped LT-GaAs grown at a low temperature of 250 ° C. with MBE on a semi-insulating GaAs substrate is grown to 1.5 μm, and in order to increase the coupling between electromagnetic waves and space on the surface, Bowtie antennas 43 and 46 made of AuGe / Ni // Au having a gap of 5 μm are formed. Si hemispherical lenses 42 and 45 are bonded to the opposite surface in order to increase the light collection efficiency.

A mode-locked laser 40 is used as a pulse laser having a pulse width of about 100 femto to about 1 picosecond. When the output is branched by the beam splitter 47 and applied to the photoconductive element 41 as a transmitter in which a 30 V electric field is applied to the antenna 43 by the power source 37, the pulse width ranges from several hundred femto to several picoseconds. An electromagnetic pulse is generated. If this beam is adjusted by the off-axis parabolic mirrors 49a and 49b and radiated to the space, it becomes a transmission pulse for the print medium type inspection. This pulse becomes a broadband electromagnetic wave including a Fourier frequency in the terahertz region. The reflected pulse from the print medium is collected by the off-axis parabolic mirrors 49c and 49d and detected by the photoconductive element 44 having the same structure. At this time, the current flowing at both ends of the antenna 46 is taken out as an output of the voltage across the resistor 38. However, the output corresponding to the strength of the electric field of the electromagnetic wave pulse is only at the timing when light is irradiated and the optical carrier is generated. Is obtained. Therefore, the optical delay element 39 for changing the optical path corresponds to the delay device 10 of FIG. 1, and the photoconductive element 44 is detected by the detector 8 of FIG. And the mixer 11 are combined.

The medium information sensing unit 5 can be constructed by integrating such devices. As the pulse laser, a mode-locked laser using a titanium sapphire crystal or an optical fiber is stable, but a semiconductor mode-locked laser having a saturable absorption region may be used for further miniaturization. Further, by using an optical fiber as an optical transmission line, or integrating a photoconductive element and an optical waveguide on the same substrate, a smaller and more stable device can be obtained.

In this embodiment, a signal is detected using a reflected pulse, but a transmitted pulse may be used in combination. In that case, the print medium is arranged between the electromagnetic wave generator and the other detector. However, when the reflected wave is used, the state of each surface of the stacked sheets can be determined, whereas when the transmitted wave is used, the average of the entire paper to be inspected is detected. Furthermore, in the arrangement of the generator and detector, the type that uses reflected electromagnetic waves can be placed on the same side of the medium, so that space utilization efficiency is good. Yes.

In the above configuration, pulses that are continuously output as electromagnetic waves are used. However, information on the medium can be obtained by interference with reflected electromagnetic waves using continuous waves with high coherence, such as quantum cascade lasers and resonant tunnel diode generators. You can also get In this case, the detection principle is as described above.

By providing the medium information sensing unit 5 including the electromagnetic wave transmission / reception unit as described above in a cassette or a conveyance system for setting a recording medium in a copying machine, an ink jet printer, a laser beam printer, etc., an operator can manually select a printing medium. It is possible to automatically set or change the printing operation conditions automatically without any operation. Therefore, it is possible to eliminate the time due to the printing failure and the waste of the printing medium. In addition, since the medium is detected using electromagnetic waves in the terahertz region, it is possible to detect against noise without the need for light shielding. Further, since the recording medium can be identified using a plurality of parameters, the identification sensitivity of the recording medium is improved. In the present embodiment, a method of sensing a plurality of sheets at the same time is adopted, but of course, a method of sensing one by one may be used.

As described above, according to the present embodiment, by using the electromagnetic waves in the millimeter wave to terahertz region, the type of the print medium stacked in the laminated sheet shape is inspected, and the optimum is achieved with high accuracy at high speed. Printing control can be performed. For this reason, it is possible to save time and waste of the printing medium and to improve the economy. Further, the identification sensitivity can be further improved by using an electromagnetic wave having a wavelength longer than that of light, and a plurality of print media can be collectively identified.

(Example 2)
Next, Embodiment 2 of the present invention will be described with reference to FIG. In the second embodiment, an integrated module as shown in FIG. 6 is used as a medium information sensing unit using electromagnetic pulses.

In this integrated module, a semiconductor mode-locked laser 60 is mounted on the substrate 50 and a pulse of about 0.3 psec is generated and coupled to the optical waveguide 61. One of the propagated laser beams is irradiated to the terahertz generator 65, converted into an electromagnetic wave 66 having a pulse width of about 0.5 psec, and propagates through the transmission paths 57a and b. The other laser beam branched by the optical waveguide 61 propagates through the optical path denoted by reference numeral 64 via the optical delay device 62 and is irradiated to the detector 63.

Here, the configuration of this module will be described. An insulating resin 52 having photosensitivity is formed on a semi-insulating GaAs substrate 50, and the Y-branch optical waveguide 61 has a refractive index higher than that of the surroundings by a photolithography process only in a part of the resin 52. It has become. As this resin, for example, photosensitive polysilane [trade name: Gracia (made by Nippon Paint)] is preferably used. In addition, optical resins such as BCB and polyimide that are photosensitive are suitable as an optical waveguide / electrical insulating layer. The terahertz generator 65 is a photoconductive switch element in which an electrode is formed on undoped LT-GaAs formed by low temperature growth. When a voltage 56 is applied to both ends of the electrodes 57a and 57b, which also serve as transmission lines, and laser pulse light having a wavelength of about 800 nm is irradiated, an electromagnetic wave pulse is generated.

The photodetector 63 is a photoconductive switch element having a structure similar to that of the terahertz generator, and photocarriers are generated only at the timing when the laser pulse light is irradiated, and the magnitude of the electric field of the electromagnetic wave pulse that has propagated through the transmission path. In response to this, a current flows and can be detected as a signal. In order to separate the DC voltage on the high frequency pulse generation side, the photoconductive switch is separated from one conductor 57b of the transmission line. Therefore, by changing the delay amount of the delay device 62, it is possible to measure the temporal change in the electric field strength of the terahertz pulse. The delay device 62 can be composed of a delay waveguide (not shown), an optical switch, an element that changes the refractive index, and the like.

Also in this embodiment, the electromagnetic wave pulse 53 is radiated to the space by the antenna 51, and the reflected electromagnetic wave 54 from the recording medium is received and processed as described in the above embodiment, thereby detecting the state of the recording medium in a non-contact manner. As a detection method, in addition to the method of the present embodiment, an EO crystal is provided in front of the photodetector 63, and the time variation of the terahertz pulse intensity is made a variation of the Pockels effect of the EO crystal to branch from the pulse laser 60. The transmitted light intensity of the transmitted light may be measured by a photodetector. In order to control the beam, a hemispherical lens 58 may be mounted on the antenna 51 to form a narrow radiation angle beam 53, or the antenna may be movable to scan the beam propagation direction.

By using such an integrated module, the entire apparatus can be reduced in size and price. Here, the short pulse is generated by using one mode-locked laser, but a system in which a terahertz continuous wave is generated by beat signals of two laser diodes having different oscillation wavelengths may be used.

(Example 3)
Embodiment 3 of the present invention relates to an ink jet printer. In this embodiment, the application state (printing state) 76 of the ink 71 on the printing medium 74 is detected as shown in FIG. When the medium information sensing unit is incorporated and arranged in the print head 70, the propagation state of the reflected electromagnetic wave 73 from the ink portion after printing changes according to the printing state with respect to the transmitted electromagnetic wave 72. It is possible to detect and discriminate the printing state while printing the information stored in the memory (storage unit). Here, the print head 70 is reciprocally scanned in the direction of the arrow along the extending direction of the platen 75, and the print medium 74 is supported by the platen 75 on the opposite side of the print head 70 across the print medium 74. While being carried, it is conveyed intermittently in the direction of the arrow. Thus, two-dimensional printing is performed on the print medium 74.

In the above configuration, the degree of ink drying and the degree of penetration into the medium change under the influence of the moisture absorption state, temperature, humidity, etc. of the print medium 74, which is absorbed and propagated by electromagnetic waves as described in the first embodiment. Detection is performed as delay change, pulse waveform change, etc., and the detection result is compared with the memory data to determine and grasp the printing status. Based on this information, the print operation conditions of the ink head 70 (discharge pressure from the nozzle, temperature, distance between the nozzle and the print medium, etc.) are automatically set or changed so that the optimum print state can be achieved in real time. Printing can be performed while controlling. Other points are the same as in the above embodiment.

By the way, it is possible to know the state of the recording medium more accurately by individually irradiating a plurality of portions of the recording medium with electromagnetic waves and detecting the reflected waves. This is particularly effective when detecting the state of a recording medium on which a print or image has already been formed. That is, it is possible to form an image with higher accuracy by accurately discriminating between the propagation state of the electromagnetic wave in the portion where the toner or ink is adhered and the propagation state of the electromagnetic wave in the portion where the toner or ink is not adhered. It is possible to detect both by irradiating the paper with a circular spot. However, there may be a case where the electromagnetic wave of the part where toner or ink is present and the part where the toner or ink is not present are mixed, and accurate signal separation may be difficult. . Therefore, there is an advantage that individual information can be accurately obtained by individually irradiating a plurality of locations.

Furthermore, it is possible to irradiate electromagnetic waves a plurality of times or to irradiate electromagnetic waves of different frequency bands, and may be used in combination with the above-described method.

As a storage means, it is preferable to create a database in advance, but by reflecting a plurality of electromagnetic waves, one reflected wave data is made into a database and compared with other reflected wave data to determine the state of the recording medium. It is also possible to do.

1 is a block diagram illustrating an image forming apparatus according to a first embodiment of the present invention. The figure explaining the method to detect the state of a recording medium using the reflected electromagnetic waves from a laminated recording medium. The graph which shows the difference in the propagation delay amount by the kind of paper. 5 is a flowchart for explaining an example flow of print control. The figure explaining the apparatus which generate | occur | produces and detects an electromagnetic wave pulse. The perspective view explaining the integrated device which generate | occur | produces and detects the electromagnetic wave pulse in Example 2 by this invention. The perspective view explaining the information sensing part of the printing state in Example 3 by the present invention.

Explanation of symbols

1. Recording media (laminated media)
2, 12 ... Setting means (calculator, image forming unit)
5. Medium information sensing unit 6, 7, 40, 41, 43, 51, 60, 65 ... Electromagnetic wave irradiation means (electromagnetic wave generator, photoconductive element, laser, antenna)
8, 9, 10, 11, 38, 39, 40, 44, 46, 51, 60, 62, 63 ... detection means (electromagnetic wave detector, photoconductive element, delay device, mixer, laser, antenna, resistance)
12. Determining means (calculator)
13. Storage means (storage unit)
14, 21, 53, 72 ... Transmitted electromagnetic waves (transmitted pulses)
15, 22, 23, 54, 73 ... Reflected electromagnetic wave (received pulse)

Claims (4)

A generator for generating an electromagnetic wave having a frequency in the terahertz region;
A detection unit for detecting the electromagnetic wave reflected by the laminated recording medium;
A storage unit for storing in advance information for detecting the type of the recording medium;
Monitoring a signal obtained from the reflected electromagnetic wave obtained using the detection unit to obtain information for detecting the type of the recording medium, and comparing the obtained information with information stored in the storage unit By means of this, an arithmetic unit for detecting the type of the recording medium ,
Have,
The information for detecting the type of recording medium is viewed including the propagation delay of the rate and pulse intensity of the pulse of the signal has to decrease,
The calculation unit obtains a position for each recording medium in the thickness direction of the stacked recording media by counting the pulses that the signal has, and for each pulse that the signal has, An image forming apparatus for detecting a type of a recording medium . The image forming apparatus according to claim 1, wherein the calculation unit sets a condition for forming an image on the recording medium based on the detected type of the recording medium. The image forming apparatus according to claim 1, further comprising a delay unit that delays a timing at which the generation unit generates the electromagnetic wave or a timing at which the detection unit detects the electromagnetic wave. A pulse laser that irradiates the generator and the detector with a pulse laser;
The image forming apparatus according to claim 3, wherein the delay unit includes an optical delay element that varies an optical path of a pulse laser.

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