JP2005214805A - Sensor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor device capable of outputting a stable signal. <P>SOLUTION: A code reader 23 that is the sensor device is constituted of a photosensor 31 of a photoreception element, an I-V conversion circuit 32, a gain regulation amplifier (GCA) 33, an A/D converter 34, and a control circuit 35. A D/A converter 36 and a resistance R are provided in the I-V conversion circuit 32. An output current Ip of the photosensor 31 is converted into a voltage by the I-V conversion circuit 32, and a voltage signal is output to the A/D converter 34 through the GCA 33 to be converted into a digital signal. A control circuit 35 extracts information of the maximum value, the minimum value and an amplitude value from the voltage signal converted into the digital signal, controls an off-set voltage by controlling an output voltage Vda of the A/D converter 34, and controls the GCA 33 to control the amplitude value of the voltage signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sensor device that performs control so as to obtain a stable output from a current-driven sensor.

  In the prior art, in order to obtain a stable output from a sensor such as a photosensor (current-driven sensor), the output from the sensor is converted into IV (current-voltage) and then a gain adjusting amplifier GCA (Gain). Control Amplifier) amplifies and attenuates the amplitude of the main signal. As such a gain adjustment method, by setting a correction parameter and keeping the closed loop gain constant by this correction parameter, even if the gain of the controlled object changes with the operating state, the influence is removed and a constant dynamic characteristic is obtained. Is known (see, for example, Patent Document 1).

JP-A-7-84604

  However, when the technique described in Patent Document 1 is used for gain adjustment of the output of the current driven sensor, the offset voltage generated due to the characteristics of the current driven sensor is also amplified and attenuated together with the main signal. Due to the offset voltage of the driving sensor, the voltage value of the main signal may be saturated at the upper limit or the lower limit, and it is difficult to obtain a stable output.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a sensor device that makes it possible to obtain a stable output without being affected by a current-driven offset voltage.

  In order to solve the above-described problems, a sensor device according to the present invention includes a current-voltage conversion unit that converts an output current of a current-driven sensor into a voltage, and gain adjustment amplification that outputs a voltage signal by controlling the amplitude of the voltage. And the maximum value, minimum value, and amplitude value from the voltage signal, and based on these values, the offset voltage of the voltage signal is controlled by the current-voltage conversion means, and the amplitude of the voltage signal is controlled by the gain adjustment amplification means. And a control means for performing the above.

  In addition, the current-voltage conversion means includes an offset voltage adjusting resistor connected to the output of the current-driven sensor and a D / A converter that applies a pull-up voltage to the offset voltage adjusting resistor. The offset voltage is controlled by changing the pull-up voltage with a voltage control signal from the control means.

  Further, the control means includes an A / D converter that digitizes a voltage signal, and obtains a maximum value, a minimum value, and an amplitude value based on the digitized voltage signal.

  Further, the control means described above maintains the output voltage of the D / A conversion means when the voltage signal is within a predetermined range between 0 V and a predetermined voltage value and the amplitude is not less than the predetermined value. When the voltage signal is within the above-mentioned predetermined range and the amplitude is smaller than the predetermined value, the output voltage of the D / A conversion means is increased or decreased, and the amplitude is increased by the gain adjustment amplification means to minimize the voltage signal. When the voltage is 0 V and the amplitude is greater than or equal to a predetermined value, the output voltage of the D / A converter is increased, and when the minimum voltage of the voltage signal is 0 V and the amplitude is smaller than the predetermined value, D / When the output voltage of the A conversion means is increased and the amplitude is increased by the gain adjustment amplification means, the output of the D / A conversion means when the maximum voltage of the voltage signal is a predetermined voltage value and the amplitude is greater than or equal to the predetermined value. Reduce the voltage and the voltage signal When and amplitude large voltage is the predetermined voltage value is smaller than the predetermined value, the lower the output voltage of the D / A converting means, characterized in that to increase the amplitude by the gain adjusting amplifier means. The aforementioned predetermined voltage value is set for each sensor device and is an upper limit value that can be read as an output signal. The predetermined value of the amplitude is the lowest amplitude value that can be read as the output signal. For example, a value that is 30% of the predetermined voltage value is set as the predetermined value of the amplitude.

  According to the sensor device of the present invention, it is possible to saturate at the lower limit and the upper limit of the signal voltage due to the influence of the offset voltage by controlling the amplitude and the offset voltage with respect to the output signal of the current drive type sensor. Can be prevented. In addition, since only the amplitude of the main signal can be amplified, a high-quality signal output can be obtained.

  FIG. 1 is a schematic diagram showing the configuration of the color thermal printer 10. The color thermal printer 10 uses a long color thermal recording paper 11 as a recording medium. The color thermal recording paper 11 is set in the color thermal printer 10 in the form of a recording paper roll 12 wound in a roll. On the side surface of the roll core 13 of the recording paper roll 12, a recording paper identification code 14 having information on the recording paper size, thermal sensitivity and fixing sensitivity is described. The recording paper roll 12 is rotated by a paper feed roller 15 in contact with the outer periphery, and the color thermal recording paper 10 is fed out and rewound.

  On the downstream side of the recording paper roll 12, a pair of conveying rollers 16 that sandwich and convey the color thermosensitive recording paper 10 is disposed, and the color thermosensitive recording paper 10 is reciprocally conveyed in the feeding direction and the rewinding direction. A thermal head 17 and a platen roller 18 are arranged on the downstream side of the conveyance roller pair 16 so as to sandwich the conveyance path of the color thermal recording paper 11. A heat generating element array 19 in which a large number of heat generating elements are arranged in a line along the main scanning direction is formed on the lower surface of the thermal head 17, and is pressed against the color thermal recording paper 11 conveyed by the conveying roller pair 16. Then, each heat generating element of the heat generating element array 19 is caused to generate heat, and each heat sensitive coloring layer is colored. Further, an optical fixing device 20 is disposed on the downstream side of the thermal head 17 and irradiates fixing light to the recorded area of the color thermal recording paper 11 to optically fix each thermal coloring layer. A cutter 21 that cuts the long color thermal recording paper 11 for each recording area is provided on the downstream side of the fixing device 20. A paper discharge port 22 for discharging the cut sheet-like color thermal recording paper 11 is disposed on the downstream side of the cutter 21.

  As shown in FIG. 2, the recording paper identification code 14 is formed by arranging 10 black or white rectangular frames F1 to F10 in a line, for example, a 10-bit code (b0, b1,... B9). It consists of The first rectangular frame F1 represents the bit b0 and is used as a paper type code. The type of recording paper is identified by this bit b0. The second and third rectangular frames F2 and F3 represent bits b1 and b2, and are used as size codes. Thereby, the size of the recording paper is identified. The fourth to seventh rectangular frames F4 to F7 represent bits b3 to b6 and are used as thermal sensitivity codes. The eighth to tenth rectangular frames F8 to F10 represent bits b7 to b9 and are used as fixing sensitivity codes.

  As a code identification method, for example, when identifying whether plain paper or sticker paper is used in the first rectangular frame F1, b0 is set to “0” when the first rectangular frame F1 is displayed as a white frame. Judged as paper. In addition, b0 is set to “1” when the black frame is displayed, and it is determined as the sticker sheet. B1 and b2 are “0,0” for A5 long size, “0,1” for A6 long size, “1,0” for A5 cut sheet size, “1,1” for A6 cut sheet size And so on.

  The recording paper identification code 14 is read by a code reading device 23 provided adjacent to the side surface of the recording paper roll 12. The code reading device 23 is connected to a system controller 24 that controls the entire color thermal printer 10. The system controller 24 acquires information relating to the recording paper type, size, and sensitivity from the code reading device 23. The system controller 24 is connected to the thermal head 17, the optical fixing device 20, and a motor 25 that rotationally drives the paper feed roller 15 and the conveyance roller pair 16, and based on information acquired from the code reader 23. Print processing is executed by controlling each unit so as to match the type, size, and sensitivity of the recording paper.

  Further, the recording paper identification code 23 may be printed in advance on the back surface corresponding to each print area, not on the side surface of the roll core, or in the form of a sheet instead of a long thermal recording paper. When the color thermal recording paper is used, the recording paper identification code 14 may be printed on the back surface of the sheet. In these cases, the code reader 23 is arranged below the conveyance path of the color thermal recording paper 11 to read the recording paper identification code 14.

  FIG. 3 is a block diagram showing an electrical configuration of the code reading device 23 which is a sensor device. The code reader 23 includes a photosensor 31 that is a light receiving element, an IV conversion circuit 32, a gain adjustment amplifier (GCA) 33, an A / D converter 34, and a control circuit 35. In the IV conversion circuit 32, a D / A converter 36 and a resistor R are provided.

  The output of the photosensor 31 passes through the IV conversion circuit 32 and the GCA 33 and is digitized by the A / D converter 34. That is, an analog signal is converted into a digital signal. The control circuit 35 acquires a signal converted into a digital signal. The control circuit 35 acquires information on the amplitude voltage, the maximum voltage, and the minimum voltage from the signal, controls the output voltage Vda of the D / A converter 36 based on the information, and further controls the GCA 33 to control the amplitude of the signal. Control.

  Below, each signal aspect and control of the offset voltage and amplitude performed based on this aspect are demonstrated. The current flowing through the photosensor 31 is Ip, the resistance in the IV conversion circuit 32 is R, the output voltage of the D / A converter 36 is Vda, the input impedance of the GCA 33 is infinite, the input voltage is Vin, and the output voltage is Vo The voltage gain is G. At this time, the output voltage Vo of the GCA 33 can be expressed by [Equation 1].

    Vo = Vmax−G (Vref−Vin)... [Formula 1]

  In [Formula 1], the output range of Vo is from 0 to Vmax. Vref is a comparative reference voltage used in the GCA 33, and here, Vmax ≦ Vref. The photosensor 31 changes Ip according to the intensity of light that is input. Therefore, the intensity of light can be read by the current change of Ip. When modulated light is input to the photosensor 31, Ip changes according to the modulation, and the change is converted into a voltage by the resistance R in the IV conversion circuit 32, and the voltage Vr can be expressed by [Equation 2]. .

    Vr = Ip × R (2)

  Therefore, the input voltage Vin of the GCA 33 can be expressed by [Equation 3].

    Vin = Vda-Vr [Equation 3]

  Next, when the output voltage Vo of the GCA 33 changes as shown in (1) to (6) below, control of the offset voltage and voltage gain will be described using the tables of FIGS.

(1) When Vo is in the range of 0 to Vmax and the amplitude voltage is a predetermined value or more.
(2) When Vo is within 0 to Vmax, but is smaller than the predetermined amplitude voltage.
(3) When the minimum voltage value of Vo is 0 and the amplitude voltage is a predetermined value or more.
(4) When the minimum voltage value of Vo is 0 and the amplitude voltage is smaller than a predetermined value.
(5) When the maximum voltage value of Vo is Vmax and the amplitude voltage is greater than or equal to a predetermined value.
(6) When the maximum voltage value of Vo is Vmax and the amplitude voltage is smaller than a predetermined value.

  Here, Vmax is an upper limit value that can be read as an output signal, and is a value set for each sensor device. The predetermined value of the amplitude voltage is the lowest amplitude value that can be read as an output signal. For example, a value of 30% of Vmax is set as the predetermined value of the amplitude.

  In the case of (1), that is, when Vo is in the range of 0 to Vmax and the amplitude voltage is equal to or greater than a predetermined value, the control circuit 35 determines that the amplitude of Vo can be read, and the offset voltage and Without controlling the voltage gain, the output Vo is obtained with the current gain G and the output voltage Vda of the D / A converter 36.

  In the case of (2), that is, when Vo is in the range of 0 to Vmax and the amplitude voltage is smaller than the predetermined value, the control circuit 35 reads an accurate signal from the output as it is because the amplitude of Vo is small. Judge that it is not possible. In the conventional control method, only the GCA 33 is controlled, and the gain G is increased to increase the amplitude. However, simply increasing the gain G may increase the amplitude of Vo, lower the voltage lower limit value to 0 or less, and saturate at the lower voltage limit. Therefore, the GCA 33 is controlled to increase the gain G, and at the same time, the output voltage Vda of the D / A converter 36 is controlled to control the output voltage Vo. Since Vr of the IV conversion circuit 32 is constant from [Equation 2], the voltage of Vin changes by ΔVda (the amount of change of Vda), so that the output voltage Vo is shifted in the direction of increase by G · ΔVda. Is done. This can prevent the output Vo from becoming 0 or less. Further, by increasing the gain G, the amplitude voltage width of Vo can be controlled to an appropriate value, and a stable output can be obtained.

  In the case of (3), that is, when the minimum voltage value of Vo is 0 and the amplitude voltage is greater than or equal to a predetermined value, the amplitude voltage of Vo is sufficient, but the minimum voltage of Vo is 0. It is determined that the signal may be saturated and an accurate signal cannot be read. In the prior art, this is dealt with only by reducing the gain G. However, since the amplitude becomes small, in this case, the gain G remains unchanged and the output voltage Vda of the D / A converter 36 is controlled to be high. . As a result, Vin becomes high, and it is possible to control the minimum value to 0 or more while maintaining the amplitude voltage width of the output Vo from [Equation 1]. Thereby, since it is not saturated with the minimum of a voltage, the stable output can be obtained.

  In the case of (4), that is, when the minimum voltage value of Vo is 0 and the amplitude voltage is smaller than the predetermined value, the control circuit 35 has a minimum value of Vo and the amplitude voltage is small. It is determined that a correct signal cannot be read. In the control method of the prior art, the value of the resistance R of the IV conversion circuit 32 is changed to cope with it. However, in the present invention, the GCA 33 is controlled to increase the gain G, and the output voltage Vda of the D / A converter 36 is controlled to be high so that the minimum value of the output Vo is 0 or more and the amplitude voltage width is also an appropriate value. Can be controlled. Thereby, since it is not saturated with the minimum of a voltage, the stable output can be obtained.

  In the case of (5), that is, when the maximum voltage value of Vo is Vmax and the amplitude voltage is greater than or equal to a predetermined value, the control circuit 35 has a maximum value of Vo of Vmax and the amplitude voltage is sufficient, but the upper limit of the voltage Therefore, it is determined that an accurate signal cannot be read with the output as it is. In the conventional control method, the value of the resistance R of the IV conversion circuit 32 is changed. However, in the present invention, the control circuit 35 controls the output voltage Vda of the D / A converter 36 to be low while keeping the gain G as it is. As a result, Vin becomes low, and the maximum value can be controlled to Vmax or less while the amplitude voltage width of the output Vo remains unchanged. Thereby, since it is not saturated at the upper limit of a voltage, the stable output can be obtained.

  In the case of (6), that is, when the maximum voltage value of Vo is Vmax and the amplitude voltage is smaller than the predetermined value, the control circuit 35 is accurate with the output as it is because the maximum value of Vo is Vmax and the amplitude voltage is small. It is determined that a correct signal cannot be read. In the control method of the prior art, the control circuit 35 only increases the gain G. However, in the present invention, the control circuit 35 increases the gain G and decreases the output voltage Vda of the D / A converter 36. To control. As a result, Vin becomes low, the output Vo becomes lower than Vmax, and the amplitude voltage width can be controlled to an appropriate value. Thereby, since it is not saturated at the upper limit of a voltage, the stable output can be obtained.

  As described above, in each of the cases (1) to (6), by controlling the offset voltage, it is possible to eliminate the influence of the offset voltage and prevent saturation at the lower limit and the upper limit of the signal voltage. In addition, only the amplitude of the main signal can be amplified, and a high-quality signal output can be obtained. Further, since the system controller 24 of the color thermal printer 10 can acquire the code information with a high-quality signal, it is possible to execute an appropriate process corresponding to the code information without performing erroneous control.

  Next, the operation of the code reading device 23 will be described using the flowchart of FIG. The photosensor 31 receives input light and converts the light into a current signal. This current signal is converted into a voltage by the IV conversion circuit 32 and output to the A / D converter 34 via the GCA 33. The A / D converter 34 converts this voltage signal into a digital signal and outputs it to the control circuit 35.

  The control circuit 35 extracts the amplitude voltage, the maximum voltage, and the minimum voltage from the acquired voltage signal and performs correction processing. First, it is determined whether or not the signal voltage Vo is within the range of 0V <Vo <Vmax. If it is determined that 0V <Vo <Vmax is within the range, it is further determined whether or not the amplitude voltage is equal to or greater than a predetermined value. If it is determined that the amplitude voltage is equal to or greater than the predetermined value, the D / A converter is determined. The output Vda is output as it is, and the correction process is terminated. If it is determined that the signal voltage is smaller than the predetermined value, the GCA 33 is controlled to increase the gain G, and the Vda is controlled to prevent the signal voltage from being saturated at the upper or lower limit of the signal voltage. The correction process is completed by outputting the signal voltage.

  When it is determined that the voltage Vo is not within the range of 0V <Vo <Vmax, it is determined whether or not the minimum voltage value of the voltage Vo is 0V. When it is determined that the minimum voltage value is not 0 V, the process proceeds to a process for determining whether or not the maximum value of the voltage Vo is Vmax. When it is determined that the minimum voltage value is 0 V, it is further determined whether or not the amplitude voltage is equal to or greater than a predetermined value. If it is determined that it is not equal to or greater than the predetermined value, the gain G is increased by controlling the GCA 33. When it is determined that the value is equal to or greater than the predetermined value, the gain G is not controlled. Thereafter, the IV conversion circuit 32 is controlled to increase Vda and proceed to the next processing.

  Thereafter, it is determined whether or not the maximum value of the voltage Vo is Vmax. If it is determined that the maximum value is not Vmax, a signal is output and the correction process is terminated. When it is determined that the maximum value is Vmax, it is determined whether or not the amplitude voltage is equal to or greater than a predetermined value. If it is determined that the amplitude voltage is smaller than the predetermined value, the gain G is increased by controlling the GCA 33. When it is determined that the amplitude voltage is greater than or equal to the predetermined value, the gain G is not controlled. Thereafter, the IV conversion circuit 32 is controlled to lower Vda and output, and the correction process is terminated.

  Thus, even if the output level and amplitude of the photosensor 31 fluctuate, it can be corrected and a signal with a constant level and amplitude can always be output, so the distance between the recording sheet identification code 14 and the photosensor 31 is Even when the roll core 13 changes as the roll core 13 rotates, the recording paper identification code 14 can be read reliably.

  In the present embodiment, the sensor device of the present invention is described as being used in a code reading device of a color thermal printer. However, the present invention is not limited to this and can be applied to various other devices. Further, although the case where the photosensor is used as the current drive type sensor has been described, other current drive type sensors may be used.

1 is a schematic diagram illustrating a configuration of a color thermal printer 10. FIG. It is explanatory drawing which shows a recording paper identification code. It is a block diagram which shows the structure of a code reader. It is a table | surface explaining correction | amendment of a signal voltage. It is a table | surface explaining correction | amendment of a signal voltage. It is a flowchart explaining the correction process of a signal voltage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Color thermal printer 23 Code reader 24 System controller 31 Photo sensor 32 IV conversion circuit 33 GCA
34 A / D converter 35 Control circuit 36 D / A converter

Claims (4)

  Current-voltage conversion means for converting the output current of the current-driven sensor into voltage, gain adjustment amplification means for controlling the amplitude of the voltage and outputting a voltage signal, and the maximum value, minimum value, and amplitude value from the voltage signal And a control means for controlling the offset voltage of the voltage signal by the current-voltage converting means and controlling the amplitude of the voltage signal by the gain adjusting and amplifying means on the basis of these values. Sensor device.   The current / voltage converting means comprises an offset voltage adjusting resistor connected to the output of the current drive type sensor and a D / A converter for applying a pull-up voltage to the offset voltage adjusting resistor, and the control means The sensor device according to claim 1, wherein the offset voltage is controlled by changing the pull-up voltage in accordance with a voltage control signal from.   The said control means is equipped with the A / D converter which digitizes the said voltage signal, and calculates | requires the said maximum value, the minimum value, and an amplitude value based on the digitized voltage signal. The sensor device described. The control means maintains the output voltage of the D / A conversion means when the voltage signal is within a predetermined range between 0 V and a predetermined voltage value and the amplitude is not less than a predetermined value,
When the voltage signal is within the predetermined range and the amplitude is smaller than the predetermined value, the output voltage of the D / A conversion unit is increased or decreased, and the amplitude is increased by the gain adjustment amplification unit,
When the minimum voltage of the voltage signal is 0V and the amplitude is not less than the predetermined value, the output voltage of the D / A conversion means is increased,
When the minimum voltage of the voltage signal is 0V and the amplitude is smaller than the predetermined value, the output voltage of the D / A conversion unit is increased, and the amplitude is increased by the gain adjustment amplification unit,
When the maximum voltage of the voltage signal is the predetermined voltage value and the amplitude is not less than the predetermined value, the output voltage of the D / A conversion means is lowered,
When the maximum voltage of the voltage signal is the predetermined voltage value and the amplitude is smaller than the predetermined value, the output voltage of the D / A conversion means is lowered and the amplitude is increased by the gain adjustment amplification means. The sensor device according to claim 2 or 3, characterized in that

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