JP2013145133A - Infrared ray measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared ray measuring device capable of preventing an ambient light component from being contained as noise and preventing malfunction by relatively simple measurement when measuring infrared ray reflection light by proximity measurement.SOLUTION: When a proximity object 40 is irradiated with infrared ray from an infrared light emission diode 42, infrared reflection light reflected by the proximity object 40 and light from a light source 41 are received by a light receiving element 3. The infrared reflection light is measured at a period of 1/4 the period of a commercial power source frequency, and a first measured value by the infrared reflection light, and a second measured value and a third measured value measured before and after the measurement time of the first measured value in a non-light emitting state of infrared are outputted. An infrared reflection light illuminance is calculated by subtracting the averages of the second and third measured values from the first measured value. In measurement by a proximity measurement part, measurement for each 1/4 the period of the commercial power source frequency is performed two times in succession. The minimum value among infrared reflection light illuminance calculated for each measurement or the average value of the calculated infrared reflection light illuminance is outputted as a calculation result.

Description

  The present invention relates to an infrared measuring device including an infrared sensor.

  For example, in mobile devices such as mobile phones, PDAs (Personal Digital Assistants), notebook PCs (Personal Computers), and tablet PCs, car navigation systems, single-lens digital cameras, etc., the touch panel system has become available as LCD screens become larger and higher in resolution. The adoption of liquid crystal is increasing. In these devices, illuminance sensors and proximity sensors are being mounted.

  The illuminance sensor is a sensor for detecting the brightness of the surroundings, and thereby, the brightness of the liquid crystal backlight can be controlled according to the surrounding brightness. On the other hand, the proximity sensor is a sensor that detects that an object has approached the device, and is used, for example, to prevent malfunction due to a part of the human body coming into contact with the touch panel.

  For example, touch panel smartphones turn off the touch panel display to prevent malfunctions due to ears or faces touching the touch panel when making a phone call. An optical proximity sensor is mounted to detect that an ear, a face, or the like is approaching.

  The optical proximity sensor detects the proximity object by causing the infrared LED to emit light in pulses and measuring the reflected light from the object using a photodiode having a sensitivity peak in the infrared region. In addition, in order to extract only light in the infrared region, an infrared transmission filter is provided to cut off ultraviolet rays and visible light.

  However, the measurement of the proximity object is performed in an environment where ambient light including infrared components such as sunlight, incandescent lamp, and halogen light exists. Therefore, it is necessary to remove the infrared component of the ambient light from the measurement value obtained by the proximity measurement and extract only the reflected light from the object.

  For example, as shown in Patent Document 1, in order to distinguish between environmental changes such as incandescent lamps and direct sunlight that are essentially detected by an infrared sensor, and objects that the user wants to detect, such as the human body Proposed to determine whether the incandescent lamp has been turned on or the approach of the human body has occurred by measuring and calculating the change time of the output of the infrared sensor and comparing it with a predetermined threshold value Has been.

JP 2010-185851 A

  However, since the change time of the infrared sensor is measured and calculated, and compared with the threshold value, measurement data when the incandescent lamp is turned on is necessary. It is not possible to accurately determine whether or not they are approaching. For example, incandescent lamps and halogen light emit light at a frequency twice the commercial power supply frequency (50 Hz, 60 Hz). For this reason, in a light source such as incandescent light or halogen light, the light emission intensity of the light source fluctuates at a constant period with time. As a result, since the light obtained by adding the infrared component of the ambient light to the infrared reflected light from the object is measured, the infrared component of the ambient light becomes noise, and the accurate illuminance of the infrared reflected light can be measured. Can not.

  Moreover, since it is considered necessary to change the threshold value depending on the type of light source of ambient light, it is extremely complicated.

  The present invention was devised to solve the above-described problem, and when measuring infrared reflected light by proximity measurement, it is possible to prevent ambient light components from being included as noise by relatively simple measurement. An object of the present invention is to provide an infrared measuring device capable of preventing malfunction.

  In order to achieve the above object, an infrared measuring device of the present invention measures an infrared light emitting element that irradiates an infrared ray with a nearby object, and infrared reflected light reflected by the neighboring object, and performs one measurement. Accordingly, the first measurement value obtained by measuring the infrared reflected light at a quarter of the period of the commercial power supply frequency, and the measurement time of the first measurement value when the infrared light emitting element is not emitting light. Proximity measurement unit having means for outputting second measurement value and third measurement value measured at the time before and after, calculation processing of measurement data from the proximity measurement unit, and processing from the first measurement value An arithmetic processing unit having means for calculating the infrared reflected light illuminance by subtracting the average of the second measurement value and the third measurement value, and the measurement by the proximity measurement unit is performed at a frequency of the commercial power supply frequency. Each quarter measurement is carried out twice in succession, And main feature to output a minimum value or the calculated average value of the infrared reflection light intensity of the issued infrared reflection light intensity as a calculation result.

  The infrared measuring device of the present invention is an infrared measuring device for measuring a proximity object from infrared reflected light including an irradiation component from a light source whose emission intensity varies at a predetermined cycle, and irradiates the proximity object with infrared rays. An infrared light emitting element and infrared reflected light reflected by the proximity object of the infrared light are measured, and the infrared reflected light including an irradiation component from the light source is converted into a light emission intensity fluctuation period of the light source by one measurement. Of the first measurement value measured at a period of 1 / N (N is an integer of 2 or more), and the time before and after the measurement time of the first measurement value when the infrared light emitting element is not emitting light. A proximity measurement unit having means for outputting the measured second measurement value and the third measurement value; and processing the measurement data from the proximity measurement unit to calculate the second measurement value from the first measurement value And the infrared reflected light illuminance is calculated by subtracting the average of the third measured values. The measurement by the proximity measurement unit is performed N times continuously for every 1 / N of the emission intensity fluctuation period, and the infrared reflection calculated for each measurement. The main feature is that the smallest value of the light illuminance or the average value of the calculated infrared reflected light illuminance is output as the calculation result.

  The infrared measurement device of the present invention includes a proximity measurement unit that measures the illuminance of infrared reflected light reflected by a proximity object, and an arithmetic processing unit that performs arithmetic processing on measurement data from the proximity measurement unit. In addition, the proximity measurement unit can measure the first measurement value obtained by measuring the infrared reflected light at a quarter of the period of the commercial power supply frequency in one measurement and the infrared light emitting element in a non-light emitting state. The second measurement value and the third measurement value measured at times before and after the measurement time of the one measurement value are output. Further, the arithmetic processing unit calculates the infrared reflected light illuminance by subtracting the average of the second measurement value and the third measurement value from the first measurement value.

  The measurement by the proximity measurement unit is performed twice in succession every 1/4 of the cycle of the commercial power supply frequency, and the smallest value or the calculated infrared value of the infrared reflected light illuminance calculated for each measurement. The average value of reflected light illuminance is output as a calculation result. For this reason, the ambient light component is substantially removed, the noise component is eliminated, and malfunction due to proximity measurement can be prevented.

  In addition, the proximity measurement unit replaces the infrared reflected light with a period of 1/4 of the period of the commercial power supply frequency, and from a light source whose emission intensity varies with a predetermined period by one measurement. A first measurement value obtained by measuring infrared reflected light including an irradiation component at a period of 1 / N of the light emission intensity fluctuation period of the light source, and a measurement time of the first measurement value when the infrared light emitting element is not emitting light. The second measurement value and the third measurement value measured at the time before and after are output. Further, the arithmetic processing unit calculates the infrared reflected light illuminance by subtracting the average of the second measurement value and the third measurement value from the first measurement value.

  Here, the measurement by the proximity measurement unit is performed N times continuously every period 1 / N, and the smallest value or the average of the calculated infrared reflected light illuminance among the infrared reflected light illuminance calculated for each measurement. The value is output as the calculation result. For this reason, the ambient light component is substantially removed, the noise component is eliminated, and malfunction due to proximity measurement can be prevented.

It is a figure which shows the whole structure of the infrared measuring device of this invention. It is a figure which shows the measurement timing of proximity measurement. It is a figure which shows the measurement timing by the measurement of multiple times of proximity measurement. It is a figure which shows the flowchart regarding the proximity measurement of this invention. It is a circuit block diagram which shows the principal part of an infrared reflected light light receiving element, a DC component removal amplifier, and an AD converter. It is a figure which shows the time chart of the main signals in the circuit block diagram of FIG. It is a figure which shows the fluctuation | variation of the emitted light intensity of an incandescent lamp. It is a figure which shows the basic measurement timing of proximity measurement. It is a figure which shows the component contained in the measured value of each measurement time of FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. The drawings relating to the structure are schematic, and there may be a case where portions having different dimensional relationships and ratios are included between the drawings.

The overall configuration of the infrared measuring apparatus of the present invention is shown in FIG. The optical signal detection unit includes a proximity measurement unit 50, an illuminance measurement unit 51, a timing control circuit 7, an oscillation circuit 8, a register circuit 14, a PS interface 15, a POR (power-on reset) 16, an I ² C interface 17, and the like. ing. Here, the POR 16 initializes the IC when the power is turned on.

  Further, an MCU (micro control unit) 44, an infrared light emitting diode 42, and the like are provided. The MCU 44 is an external control unit, and performs on / off switching of the proximity measurement unit 50, on / off switching of the illuminance measurement unit 51, and the like. The optical signal detection unit is also provided with a GND terminal for LEDs, a GND terminal for circuit elements, and the like. A capacitor 43 is inserted between the terminal of the power supply voltage VDD and GND, thereby cutting high frequency noise.

  The proximity measurement unit 50 includes an LED pulse generator 1, an infrared LED driver 2, a light receiving element 3, a DC component removal amplifier 4, an AD converter 5, a logarithmic converter 6, and a PS control logic 18. The PS control logic 18 is a logic circuit for controlling the proximity measurement unit 50. The PS control logic 18 performs processing such as calculation and determination based on digital data from the AD converter 5 and the register circuit 14. The cathode of the infrared light emitting diode 42 supplied with the power supply voltage VDD is connected to the terminal of the ILED. The infrared light emitting diode 42 is a diode that emits light in the infrared region. The light receiving element 3 is composed of a photodiode having a sensitivity peak in the infrared region in order to detect infrared rays with high sensitivity. Moreover, the photodiode which cuts visible light and an ultraviolet-ray, and has the infrared rays permeation | transmission filter which permeate | transmits infrared rays in a light-receiving surface may be used.

  On the other hand, the illuminance measurement unit 51 includes a light receiving element 9, an amplifier 10, a capacitor 11, an AD converter 12, and an ALS control logic 13. The ALS control logic 13 is a logic circuit for controlling the illuminance measurement unit 51. The light receiving element 9 is configured by a photodiode having a sensitivity peak in the visible light region in order to measure the illuminance of the light source 41 serving as ambient light.

Normal illuminance measurement of ambient light is performed as follows. When light from the ambient light source 41 is received by the light receiving element 9, a photocurrent is generated in the light receiving element 9 by a photoelectric conversion action. This photocurrent is integrated by an integration circuit including an amplifier 10 and a capacitor 11, and the value is input to the AD converter 12. The AD converter 12 is an integral AD converter. The digital value AD-converted by the AD converter 12 is transmitted to the ALS control logic 13. The ALS control logic 13 calculates the illuminance based on the AD converted digital value, and this data is transmitted to the register circuit 14 and held in the register circuit 14. The ambient light measurement data held in the register circuit 14 is output to the MCU 44 via the I ² C interface 17.

  Next, the measurement of infrared reflected light by proximity measurement is performed as follows. First, the LED pulse generator 1 generates a base pulse for causing the infrared light emitting diode 42 to emit light, and supplies the pulse to the infrared LED driver 2. The LED driver 2 changes the pulse signal for driving the infrared light emitting diode 42 based on the pulse signal from the LED pulse generator 1. Since the light emitting diode is current driven, a current pulse signal is output from the infrared LED driver 2. In the infrared LED driver 2, a current pulse signal of 5 mA to 200 mA can be created, and for example, a current pulse signal in the range of 5 mA to 10 mA is used. Further, the duty ratio of the current pulse signal can be changed variously, but the light emission period can be set to 250 μS, for example.

  In this way, when the current pulse signal for driving the light emitting diode is supplied from the infrared LED driver 2 to the infrared light emitting diode 42, the infrared light emitting diode 42 performs a light emitting operation during the ON period of the current pulse signal for driving, Repeat this. The proximity measurement unit 50 and the illuminance measurement unit 51 are operated in a time division manner. The reason why the infrared light emitting diode 42 is not caused to emit light during the operation of the illuminance measuring unit 51 is that light received from the infrared light emitting diode 42 becomes an error signal to the illuminance measuring unit 51.

  Infrared rays emitted from the infrared light emitting diode 42 reach the near object (object) 40 and are reflected. The infrared reflected light reflected and returned from the proximity object 40 is received by the light receiving element 3. As will be described later, ambient light measured before and after the measurement of the infrared reflected light is also measured by the proximity measuring unit 50 when it is received by the light receiving element 3. The infrared reflected light is converted into a photocurrent by the light receiving element 3 and output to the DC component removing amplifier 4. In order to detect infrared reflected light received at a predetermined period, the DC component removal amplifier 4 removes a DC component that becomes noise from the photocurrent and amplifies the periodic component.

  The photocurrent amplified by the DC component removal amplifier 4 is input to the AD converter 5. The AD converter 5 is an integral AD converter. As will be described later, the integration type AD converter 5 is configured to discharge the capacitor by dividing the charge into a collective discharge and a step discharge. The batch discharge time and the stage discharge time are counted, the total charge amount of the capacitor is calculated from the counted time, and a digital value corresponding to the result is output as a conversion result of the AD converter 5. The

The output of the AD converter 5 is input to the logarithmic converter 6 and converted into a logarithm. The logarithmic converter 6 converts, for example, 21-bit input data into 8-bit logarithmic data and outputs it. Logarithmic data from the logarithmic converter 6 is input to the register circuit 14 and held therein. The digital data held in the register circuit 14 is output to the MCU 44 via the I ² C interface 17. On the other hand, when proximity measurement is performed and proximity detection is performed, an interrupt signal is transmitted to the MCU 44 via the PS interface 15.

  Next, the basic measurement timing in the proximity measurement of the infrared measurement device is shown in FIG. As shown in FIG. 8, in the case of an incandescent light source or halogen light source that has an infrared component and whose light emission intensity fluctuates at a predetermined cycle, the light emission intensity by the light source fluctuates like a sine wave at a constant cycle with time Therefore, the ambient light irradiance due to the infrared component of the ambient light also varies. For example, incandescent lamps and halogen light emit light at a frequency twice the commercial power supply frequency (50 Hz, 60 Hz).

  FIG. 7 shows an actual measurement of the illuminance of the incandescent lamp. The vertical axis represents emission intensity (arbitrary unit), and the horizontal axis represents time (mS). As shown in the figure, one block of the time scale is 2 mS. FIG. 7A shows a light emission intensity waveform of the silica bulb. FIG. 7B shows a light emission intensity waveform of the clear light bulb. 7A and 7B emit light at a frequency of 120 Hz.

  Therefore, before and after measuring the reflected light from the object by causing the infrared LED to emit light, measure the infrared component of the ambient light, and subtract the average of these values from the measured infrared reflected light from the object. To remove the infrared component of ambient light.

As shown in FIG. 9, when the infrared LED is caused to emit light at time t2 and the infrared reflected light is measured, the infrared component of the ambient light is measured at times t1 and t3 when the infrared LED does not emit light before and after time t2. If the measured values at t2 are M2, t1, and t3 are AIR1 and AIR3, respectively, and M2 is an added value of the ambient light component AIR2 and the infrared reflected light component LED1, the radiation of the infrared reflected light is emitted. Illuminance LED1 is
LED1 = M2- (AIR1 + AIR3) / 2 (1)
Calculate with Here, the ambient light measurement at the times t1 and t3 and the infrared reflected light measurement at the time t2 are performed by the proximity measurement unit 50, and the irradiance is calculated based on the photocurrent from the light receiving element 3. .

  However, in the above calculation method, depending on the measurement time, as shown in FIG. 8, the emission intensity of the ambient light may peak at the measurement time t2 of the infrared reflected light, and in this case, at the time t2. The ambient light irradiance measured at time t2 is higher than the ambient light irradiance measured at t1 and t3 before and after. That is, AIR2> (AIR1 + AIR3) / 2 may be satisfied. In this case, even if an attempt is made to remove the ambient light component by the above equation (1), it cannot be completely removed.

  Thus, the ambient light component may remain without being removed in the calculation result of the infrared reflected light irradiance LED1 by the above formula (1), and the irradiance with the ambient light component added as noise may be left. Even if there is no proximity object, it is calculated, which causes a malfunction of determining that the proximity object exists.

  FIG. 2 shows the change in irradiance and the measurement timing of proximity measurement regarding the infrared light component of ambient light emitted from a light source such as an incandescent lamp or halogen. The vertical axis represents irradiance related to the infrared light component of ambient light, and the horizontal axis represents time.

  As described above, in the proximity measurement, when the time t2 when the infrared reflected light including the ambient light is measured overlaps the time when the ambient light intensity is the highest as shown in FIG. 8, the measurement is performed at t1 and t3 before and after the time t2. Even if the average of the ambient light irradiance is subtracted, the ambient light component cannot be removed.

  On the other hand, FIG. 2 shows the timing of proximity measurement different from FIG. The intensity of the ambient light varies periodically. FIG. 2A shows a case where measurement is performed at times t4, t5, and t6 between the maximum value and the minimum value of the ambient light irradiance. The infrared light emitting diode 42 is caused to emit light at time t5 and infrared reflected light including ambient light is measured. At times t4 and t6 when the infrared light emitting diode 42 does not emit light before and after time t5, the infrared light component of ambient light is measured. Measure. As described above, the intensity of ambient light such as an incandescent lamp or halogen fluctuates periodically with a sine wave. Therefore, it is preferable to take time intervals between times t4, t5, and t6 so that (t5-t4) and (t6-t5) are equal.

Since the ambient light irradiance at time t4 is X1, the ambient light irradiance at time t5 is X2, and the ambient light irradiance at time t6 is X3, X2 is an intermediate value between X1 and X3.
X2≈ (X1 + X3) / 2 (2)
It becomes. Therefore, if the measurement irradiance including infrared reflected light and ambient light at t5 is L and the irradiance of only the infrared reflected light is R, then R = L−X2. The measured irradiance at t4 is X1, and the measured irradiance at t6 is X3. Therefore, when calculated by the equation R = L− (X1 + X3) / 2, the ambient light component is approximately equal to the above equation (2). Removed.

  Next, FIG. 2B will be described. FIG. 2B shows a case where the measurement is performed at time t8 at which the ambient light intensity is minimum and at times t7 and t9 before and after the time t8. At time t8, the infrared light emitting diode 42 is caused to emit light and infrared reflected light including ambient light is measured. At times t7 and t9 when the infrared light emitting diode 42 does not emit light before and after time t8, the infrared light component of ambient light is measured. Measure. Here too, for the same reason as in FIG. 2A, it is preferable to take time intervals between times t7, t8, and t9 so that (t7-t8) and (t9-t8) are equal.

Since the ambient light irradiance at time t7 is Y1, the ambient light irradiance at time t8 is Y2, and the ambient light irradiance at time t9 is Y3, Y2 is the minimum value.
Y2 <(Y1 + Y3) / 2 (3)
It becomes. That is, Y2− (Y1 + Y3) / 2 <0, and a negative value is obtained if only the ambient light irradiance is calculated. Therefore, if the measurement irradiance including infrared reflected light and ambient light at t8 is L and the irradiance of only the infrared reflected light is R, then R = L−Y2. The measured irradiance at t7 is Y1, and the measured irradiance at t9 is Y3. Therefore, when calculated by the equation R = L− (Y1 + Y3) / 2, the ambient light component is approximately equal to the above equation (3). Removed.

  As described above, if any one of the measurement patterns shown in FIGS. 2A and 2B can be used, the ambient light component that becomes noise can be substantially removed. Therefore, the measurement method shown in FIG. 3 allows the measurement patterns shown in FIGS. 2A and 2B to be used.

  In the measurement of FIG. 3, the first proximity measurement and the second proximity measurement are performed twice in a cycle that is ½ of the period of change in ambient light emission intensity. In other words, proximity measurement is continuously performed twice at a frequency twice the frequency of the change in ambient light emission intensity.

  For example, as shown in FIG. 3A, in the first proximity measurement, measurement is performed at times t11, t12, and t13. t12 is a measurement time of infrared reflected light including ambient light, and t11 and t13 before and after t12 are measurement times of only ambient light. Here, the emission intensity of the ambient light at time t12 is maximized, and the ambient light component remains as noise as described with reference to FIG.

  On the other hand, in the second proximity measurement, since the measurement is performed after ½ of the period of change in ambient light emission intensity from the first proximity measurement, the measurement time t15 of the second proximity measurement is This corresponds to the time when the emission intensity of the ambient light is minimum, and the infrared reflected light including the ambient light is measured. Further, by measuring the irradiance of only ambient light at times t14 and t16 before and after time t15, the measurement pattern shown in FIG. 2B can be configured. As described above, in the measurement patterns at times t14, t15, and t16, the ambient light component that becomes noise can be substantially removed.

  Therefore, in the measurement pattern of FIG. 3A, the infrared reflected light illuminance R1 calculated from the measurement value of the first proximity measurement remains without removing the ambient light component, and the second proximity measurement is performed. In the infrared reflected light illuminance R2 calculated from the measured value, the ambient light component takes a negative value, so R1 is larger than R2. Therefore, by comparing R1 and R2 and outputting R2 having a smaller numerical value as the final infrared reflected light illuminance, an infrared reflected light illuminance from which ambient light is substantially removed can be obtained.

  Further, an average of (R1 + R2) / 2 of R1 and R2 may be output as the final infrared reflected light illuminance. In this case, the difference D1 between the measured value at t11 and the average measured value at t13 and the measured value at t12 is substantially equal to the difference D2 between the measured value at t14 and the average measured value at t16 and the measured value at T15. , (R1 + R2) / 2, D1 and D2 are canceled out, and the ambient light component can be substantially removed.

  Next, the measurement pattern in FIG. The first proximity measurement is performed at times t21, t22, and t23 in a region from the maximum value to the minimum value of the periodic change in the ambient light emission intensity. t22 is a measurement time of infrared reflected light, and t21 and t23 before and after t22 are measurement times of only ambient light. Here, the irradiance of ambient light at time t22 is substantially equal to the average value of the irradiance of ambient light at time t21 and the irradiance of ambient light at time t22, and is described with reference to the measurement pattern in FIG. As described above, the ambient light component is substantially removed.

  On the other hand, in the second proximity measurement, since the measurement is performed after ½ of the cycle of the change in the emission intensity of the ambient light from the first proximity measurement, the time t25 of the second proximity measurement is Measurement is performed at times t24, t25, and t26 in a region between the minimum value and the maximum value of the irradiance of ambient light. t25 is a measurement time of infrared reflected light including ambient light, and t24 and t26 before and after t25 are measurement times of only ambient light. Here, the irradiance of ambient light at time t25 is substantially equal to the average value of the irradiance of ambient light at time t24 and the irradiance of ambient light at time t26, and is described with reference to the measurement pattern in FIG. As described above, the ambient light component is substantially removed.

  As described above, in FIG. 3B, since the first proximity measurement and the second proximity measurement both constitute the measurement pattern of FIG. 2A, the measurement of the first proximity measurement is performed. The average value ((R3 + R4) / 2) of the infrared reflected light illuminance R3 calculated by the value and the infrared reflected light illuminance R4 calculated by the measurement value of the second proximity measurement is output as the final infrared reflected light illuminance. Just do it. When R3 and R4 are substantially equal, the average value may be output as described above. However, the measurement region of three points at times t21, t22, and t23 and the measurement region of three points at times t24, t25, and t26 If the positions are different, R3 and R4 will be different. In this case, R3 and R4 may be compared and the smaller one may be output as the final infrared reflected light illuminance. Since the calculated infrared reflected light illuminance is small, it can be said that the infrared reflected light illuminance is measured in a region close to the minimum value of the ambient light irradiance, and therefore approaches the measurement pattern of FIG. Removal is ensured.

  Note that the above condition may be expanded so that the proximity measurement is continuously performed N times every 1 / N of the period of change in ambient light emission intensity. In other words, the proximity measurement may be continuously performed N times at a frequency N times the frequency of the change in ambient light emission intensity. In this case, one period of change in ambient light emission intensity is equally divided into N, and proximity measurement is performed N times continuously in one period. Here, N represents an integer of 2 or more. Similarly to the description in FIG. 3, the final infrared reflected light illuminance is the smallest value among the N infrared reflected light illuminances calculated for each of N measurements, or the calculated N infrared reflected lights. What is necessary is just to output the average value of light illuminance as a calculation result.

  However, considering the load and power consumption problem due to the light emission of the infrared light emitting photodiode, the calculation processing time, etc., it is actually desirable to set N = 2.

  Artificial light sources such as incandescent lamps and halogen lights emit light at a frequency approximately twice the commercial power supply frequency (50 Hz, 60 Hz), and the light emission intensity varies. Therefore, when the proximity measurement method of the present invention is applied, proximity measurement for every quarter of the period of the commercial power supply frequency may be performed twice in succession.

  The measurement operation of the proximity measurement of the infrared measurement device of the present invention will be described below. 4 shows a flowchart of the measurement operation, FIG. 5 shows a circuit configuration of the photodiode 3, the DC component removal amplifier 4, and the AD converter unit of the AD converter 5, and FIG. 6 shows a time chart of main signals.

  When the measurement is started, the gain of ambient light is determined (S1). Based on the gain determination, a capacitor having an appropriate capacity is selected in the integration circuit and the discharge circuit of FIG.

  The integrating circuit includes an operational amplifier 68, capacitors 84 (16 pF), 85 (15 pF), 86 (1 pF) connected between the inverting input and the output of the operational amplifier 68, and switches 63 and 65 for selecting these capacitors. Consists of. In addition, the discharge circuit includes capacitors 82 (16 pF), 81 (15 pF), 80 (1 pF) connected in parallel to the output of the buffer amplifier 39, and switches 23, 24, 25, 27, which select these capacitors. 28, 30 and so on. The opening / closing operation of each switch is performed by a control signal from the PS control logic 18. The same applies to the switches described below.

For example, when the maximum value of the calculated illuminance of ambient light is up to 416 μW / cm ² , the switches 23 and 24 are turned on so that the 1 pF capacitors 80 and 86 are connected to the circuit. As the maximum value of the calculated illuminance of ambient light in the case of up to 6.656mW / cm ² beyond the 416μW / cm ^2, capacitors 82 and 84 of 16pF is connected to the circuit, switch 28,30,63 is on It becomes. As the maximum value of the calculated illuminance of ambient light in the case of up 106.5mW / cm ² beyond the 6.656μW / cm ^2, the capacitor of 32pF is connected to the circuit, switch 23,25,28,24, 27, 30, 64, and 65 are turned on.

  Here, a capacitor having a capacity of 32 pF does not exist in the circuit, but when capacitors are connected in parallel, the total capacity is the sum of the capacities of the capacitors, so that the switches 23, 25, 28, If 24, 27, and 30 are turned on, a 32 pF capacitor can be obtained in the discharge circuit. If the switches 64 and 65 are turned on, a 32 pF capacitor can be obtained in the integrating circuit.

  Before performing the gain determination, first, the switches 33, 34, 35, and 36 are switched depending on whether or not the photocurrent is detected with high sensitivity. The photodiodes 37 and 38 correspond to the light receiving element 3 made of the photodiode of FIG. 1, and in an actual circuit, if light is received by a plurality of photodiodes, the sensitivity becomes high, and light is received by one photodiode. Therefore, the switches 34 and 36 are switched depending on whether or not high sensitivity measurement is performed. The photodiode 37 (× 7) has a configuration in which a plurality of photodiodes are connected in series, and the photodiode 38 (× 1) is configured by one photodiode. For example, when high sensitivity measurement is desired, the switches 33 and 36 are turned on and the switches 34 and 35 are turned off. In this embodiment, the switches 35 and 36 are opened and closed so that the photodiode 38 is used.

  Thereafter, the first ambient light measurement in the first proximity measurement in which three points of data are collected is performed. The photocurrent detected by the photodiode 38 is input to the inverting input terminal of the operational amplifier 68. At this time, the DC component of the photocurrent is cut by the DC removal amplifier 4 constituted by the constant current source 20, the switching transistor 21, the operational amplifier, etc., and the periodic component is amplified. This removes the DC voltage applied to the photodiode 38 by causing a current to flow from the cathode side to the anode side of the photodiode 38 by the constant current source 20 via the transistor 21.

At this time, the switch 31 is turned on, the switch 67 is turned on, the operational amplifier 68 is used as a buffer amplifier, and the output PAOUT1 is compared by the comparators 73-77. The voltage V _REF output from the buffer amplifier 69 is input to one input terminal of the comparator 73 as a threshold voltage. This V _REF is created through the buffer amplifier 20 with the DC bias VBG.

The output voltage V _REF of the buffer amplifier 20 is _divided by a plurality of series-connected resistors connected next, and a voltage of V _REF × _7/9 is applied to the output of the buffer amplifier 70 as a buffer amplifier. The output of 71 is V _REF × _5/9 , the output of buffer amplifier 72 is V _REF × _3/9 , the output of buffer amplifier 60 is V _REF × _2/9 , and the voltage of V _REF × _2/9 is grounded. A voltage of V _REF × _1/9 is generated at the terminal of the R / 2 resistor connected to the line. Thus, one input threshold voltage V _REF × 7/9 to the terminal of the comparator 74, while the threshold voltage V _REF × 5/9 to the input terminal of the comparator 75 is, to one input terminal of the comparator 75 The threshold voltage V _REF × _3/9 is input to one input terminal of the comparator 77, and the threshold voltage V _REF × _1/9 is input.

Here, the light detection signal PAOUT1 obtained by the first ambient light measurement is compared by each of the comparators 73 to 77 to determine which range is present. The photodetection signal PAOUT1 at this time is taken into the register circuit 14 via the logarithmic converter 6 in a period of 14 μS or less, for example. The light detection signal PAOUT1 is output to the PS control logic 18. The PS control logic 18 determines the transmitted data. If the photodetection signal PAOUT1 is larger than V _REF × 7/9 and smaller than V _REF , for example, the dynamic range may be small, and a 32 pF capacitor is selected. As described above, the control signal is transmitted to the AD converter 5, and the switches 23, 25, 28, 24, 27, 30, 64, and 65 of the AD converter 5 are turned on.

Also, large light detection signal PAOUT1 is than V _REF × 3/9 For example, if V _REF × 5/9 smaller, since the dynamic range is required to be large, as capacitors 1pF is selected, the switch 23 24 are turned on.

  As shown in FIG. 5, a grounded capacitor is inserted between the terminal of the R / 2 resistor connected to the ground line and the terminal of the comparator 77.

  As shown in FIG. 6, the period T1 of the photodetection signal acquisition and gain determination for gain determination in the first ambient light measurement described above is configured to be processed at a total of 14.1 μS, for example. FIG. 6 shows an example in which the output COUT2 of the comparator 76 is at a high level. In this example, as described above, the switches 23 and 24 are turned on so that the 1 pF capacitor is selected.

  Next, after a certain waiting time T2, a photocurrent integration of ambient light is started (S2). In the example of FIG. 6, the waiting time T2 is 19.8 μS. In this photocurrent integration, the switch 67 is turned off, and the switches 64 and 65 are also kept off. Further, the switches 62 and 87 are turned on. The integration of the photocurrent signal is performed by charging the capacitor 86 in the integrating circuit of the operational amplifier 68 and the capacitor 86 (1 pF).

As the capacitor 86 is charged, the output voltage PAOUT1 of the operational amplifier 68 increases with V _REF × 1/9 as an initial voltage.

The output of the operational amplifier 68 is input to the comparators 73-77. In this charging process, it is determined whether a predetermined time has elapsed since the first photocurrent integration of ambient light (S21). When a predetermined time has not elapsed since the first photocurrent integration of ambient light (S21 NO), the determination process of S31 is performed. Output PAOUT1 of integrated operational amplifier 68 becomes higher than V _REF (S31YES), comparator 73-77, respectively outputs a high level signal, the COUT0, COUT2, COUT3, COUT4, COUT5 all high-level signal . These high level signals are output to the PS control logic 18.

The PS control logic 18 determines the transmitted data, outputs a control signal to the AD converter 5, turns on the switches 22, 23, 24, 67 and starts large discharge (collective discharge) of the capacitor 86 ( S3). In the collective discharge mode, the accumulated charge in the capacitor 86 is transferred to the capacitor 80 of the discharge circuit. As a result, the output PAOUT1 of the operational amplifier 68 is reduced to V _REF × 1/9. On the other hand, when the output PAOUT1 of the operational amplifier 68 is equal to or lower than V _REF (S31NO), the determination process of S21 and S31 is repeated, and the process waits until PAOUT1 becomes higher than V _REF . However, even after the elapse of a predetermined time (S21 YES), it may PAOUT1 is not higher than V _REF. In this case, the process proceeds to the next step S4.

On the other hand, when PAOUT1 decreases to V _REF × 1/9 or less due to collective discharge, the output COUNT0 of the comparator 77 becomes a low level signal, which is transmitted to the PS control logic 18. The PS control logic 18 turns off the switches 23, 24 and 67 by the control signal, adds a predetermined value indicating the collective discharge amount to the ALUOUT signal, and finishes the collective discharge of the capacitor 86 (from S3 to S21). As a result, the output voltage of the operational amplifier 68 rises again. When the predetermined time has not elapsed since the first photocurrent integration of the ambient light and the output PAOUT1 of the operational amplifier 68 becomes higher than V _REF , the capacitor 86 is discharged once again (S3). Thereafter, the charge stored in the capacitor 86 is repeatedly discharged every time the output PAOUT1 of the operational amplifier 68 reaches V _REF until a predetermined time has elapsed from the first photocurrent integration of ambient light. .

  In PAOUT1, the state of the above charge and collective discharge is a sawtooth waveform in the charge + collective discharge time of period T3 shown in FIG. It is indicated that the period of T3 is 147 μS, for example. In this case, charging and collective discharging are repeated during the period of T3.

When the predetermined time (period T3) elapses (S21 YES), the photocurrent integration of the ambient light is terminated (S4). The switch 35 is turned off and the switch 36 is turned on, and the voltage level of the PAOUT1 signal level VC at that time is determined using the comparators 73-77. For example, Cout0 the high level signal, COUT2, COUT3, Cout 4, if COUT5 became all the low level signal, the voltage VC after charging, the voltage range of _{V REF × 1 / 9~V REF ×} 3/9 I know that there is. In this case, stepwise discharging a maximum of 32 times the voltage VC to the lower limit value V _REF × 1/9 of the voltage range _{V REF × 1 / 9~V REF ×} 3/9 (S5).

  In this step discharge mode, the switches 22, 23, 24 and 67 are turned on by the control signal from the PS control logic 18, and the step discharge of the capacitor 86 is started. In this stage discharge mode, the charge obtained by dividing the accumulated charge of the capacitor 86 into a plurality of stages is transferred to the capacitor 80 of the discharge circuit. Thereafter, by switching the switch, small stepwise small discharges are repeatedly performed by a predetermined amount until the electric charge remaining in the capacitor 86 reaches a predetermined value. The number of stage discharges is measured by a COUNTSTEP signal shown in FIG.

  Then, the value of the COUNTERSTEP signal obtained by measuring the number of stage discharges is added to the ALUOUT signal indicating the collective discharge amount, and the total charge amount of the capacitor 86 is calculated from the ALUOUT signal as a result of addition, and a digital value corresponding to the result is obtained. , And output as a conversion result of the AD converter 5.

  In this way, collective discharge and step discharge can be used properly to perform rough measurement with collective discharge and fine measurement with step discharge only at the end, thus expanding the input dynamic range without requiring complicated external control. It is possible to improve both the minimum resolution and the measurement time.

Next, the gain determination of the infrared reflected light including the ambient light component is performed by the same method as in the above-described ambient light gain determination of S1 (S6). In the same manner as described in S2 to S5 and S21 and S31, integration of the photocurrent of the infrared reflected light including the ambient light component is started (S7) until a predetermined time elapses (S22), It is determined whether or not PAOUT1> V _REF (S32). If PAOUT1> V _REF (S22 YES), collective discharge is performed (S8). After repeating the charging and collective discharging several times until a predetermined time elapses (S7, S8, S22, S32), when the predetermined time elapses, the photocurrent integration of ambient light and infrared reflected light is terminated ( S9), step discharge is performed by the number of times up to 32 steps (S10). Here, the infrared LED (infrared light emitting diode 42) emits light during a period T5 that is a total time of the gain determination time T1, the waiting time T2, and the charge + collective discharge time T3. The infrared LED emits light only when measuring the reflected infrared light.

  Next, in the same manner as in S2 to S5 and S21 and S31, the photocurrent integration of ambient light (S11) and the operation of repeating charging and collective discharge several times until a predetermined time elapses (S11, S12, S23). , S33), the end of photocurrent integration of ambient light (S13), and step discharge (S14) are performed. When the processes of S11 to S14, S23, and S33 are performed, the ambient light gain determination process is performed in S1, so that it is not necessary to perform the ambient light gain determination again. Calculations for noise removal are performed based on the measurement data obtained by the processes of S1 to S14, S21 to S23, and S31 to S33 (S15). This is calculated by the above equation (1) shown in FIG. That is, measure the infrared component of ambient light at times before and after the measurement time of infrared reflected light including ambient light components, and subtract the average of these values from the measured infrared reflected light from the object. Remove the infrared component of light. This calculation process is performed by the PS control logic 18.

  If the measurement data obtained by the processing of S1 to S15, S21 to S23, and S31 to S33 is data obtained by the first measurement (S16 NO), after waiting for time (S18), the second For the second measurement, the process returns to the ambient light gain determination in S1. The waiting time of S18 is set so as not to shift to the next second measurement, for example, from the start of the first measurement to 5 mS. Similarly to the first measurement process, the processes from S1 to S15, S21 to S23, and S31 to S33 related to the second measurement are performed.

  Note that the second measurement is performed after ½ of the period of change in the emission intensity of the ambient light from the first proximity measurement. On the other hand, if the data is obtained by the second measurement (S16 YES), since the measurement pattern shown in FIG. 3 is configured, the PS control logic 18 uses the two data obtained by the two proximity measurements. The calculated values are compared and the smaller one is output, or the average value of the two calculated values is output (S17). Thereby, the process ends.

  The photodetector of the present invention is particularly applicable to smartphones, mobile phones, car navigation systems, notebook computers, tablet PCs, and the like.

DESCRIPTION OF SYMBOLS 1 LED pulse generator 2 Infrared LED driver 3 Light receiving element 4 DC component removal amplifier 5 AD converter 6 Logarithmic converter 7 Timing control circuit 8 Oscillation circuit 9 Light receiving element 10 Amplifier 11 Capacitor 12 AD converter 13 ALS control logic 14 Register circuit 15 PS interface 16 POR
17 I ² C interface 18 PS control logic 40 proximity object 41 light source 42 infrared light emitting diode 44 MCU
50 Proximity measurement unit 51 Illuminance measurement unit

Claims (7)

An infrared light emitting device for irradiating a nearby object with infrared light;
A first measurement value obtained by measuring the infrared reflected light reflected by the proximity object and measuring the infrared reflected light at a period of 1/4 of a period of a commercial power supply frequency by one measurement; A proximity measurement unit having means for outputting a second measurement value and a third measurement value measured at times before and after the measurement time of the first measurement value in a state where the infrared light emitting element is not emitting light;
Computation having means for computing measurement data from the proximity measurement unit and subtracting the average of the second measurement value and the third measurement value from the first measurement value to calculate the infrared reflected light illuminance A processing unit,
In the measurement by the proximity measurement unit, the measurement is performed twice in succession every ¼ of the period of the commercial power supply frequency, and the smallest value or the calculated value of the infrared reflected light illuminance calculated for each measurement is calculated. An infrared measurement apparatus that outputs an average value of the illuminance of reflected infrared light as a calculation result.   The difference between the measurement time of the first measurement value and the measurement time of the second measurement value is equal to the difference between the measurement time of the first measurement value and the measurement time of the third measurement value. The infrared measurement apparatus according to claim 1, wherein An infrared measurement device that measures a proximity object from infrared reflected light including an irradiation component from a light source whose emission intensity varies at a predetermined cycle,
An infrared light emitting device for irradiating a nearby object with infrared light;
The infrared reflected light reflected by the proximity object is measured, and the infrared reflected light including the irradiation component from the light source is converted into 1 / N (N of the light emission intensity fluctuation period of the light source by one measurement. Is a second measurement measured at a time before and after the measurement time of the first measurement value in a state where the infrared light emitting element is not emitting light. A proximity measurement unit having means for outputting a value and a third measurement value;
Computation having means for computing measurement data from the proximity measurement unit and subtracting the average of the second measurement value and the third measurement value from the first measurement value to calculate the infrared reflected light illuminance A processing unit,
In the measurement by the proximity measurement unit, the measurement at every 1 / N of the emission intensity fluctuation period is continuously performed N times, and the smallest value or the calculated value of the infrared reflected light illuminance calculated for each measurement is calculated. An infrared measurement apparatus that outputs an average value of infrared reflected light illuminance as a calculation result.   The infrared measurement apparatus according to claim 3, wherein the light emission intensity fluctuation period of the light source is a period of a sine wave.   The infrared light measuring apparatus according to claim 4, wherein the light source emits light at a frequency twice as high as a commercial power supply frequency.   The infrared measurement apparatus according to claim 3, wherein N is two. The difference between the measurement time of the first measurement value and the measurement time of the second measurement value is equal to the difference between the measurement time of the first measurement value and the measurement time of the third measurement value. The infrared measurement apparatus according to claim 6, wherein

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