JPH0752125B2 - Irradiometer - Google Patents

Description

TECHNICAL FIELD The present invention is capable of accurately quantitatively detecting radiation power in a wide range from the ultraviolet wavelength range to the infrared wavelength range, and is compact and lightweight as a portable device. Irradiance meter which was made.

Conventional technology It has been a long time for detecting radiation power (for example, mW · cm ^-2 unit), and thermocouples and thermopile arrays (thermopile) that have black sensitivity on the light-receiving surface and have no wavelength dependence of sensitivity have been used. It was used, but these have a large zero point drift,
The response time (time constant) is also large. In addition, it was difficult to practically use because sufficient sensitivity could not be obtained.

Recently, a radiation detection element utilizing the pyroelectric effect has been developed as an alternative to these. However, pyroelectric radiation detection elements are insensitive to steady (non-time-varying, constant intensity) incidence, responding only to the differential variation of the incident radiation. Therefore, the pyroelectric radiation detecting element is often used for detecting a transient change phenomenon such as a fire occurrence or a change in radiation by an intruder.

Problems to be Solved by the Invention In order to measure the amount of stationary light with a pyroelectric radiation detection element, it is usually necessary to drive the rotating sector with a motor or the like to interrupt the input radiation. When a irradiance meter is constructed by combining this with a transmission diffusion structure that approximates the light receiving angle sensitivity characteristic of the receiver to the cosine law, the rotating sector blocks the radiation by sweeping the light receiving surface from the edge of the light receiving surface. However, there is a problem that the incident angle characteristic of the light receiver changes with time.

In addition, the device is complicated, precise, and large-scale, and thus is not suitable for a portable irradiometer.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above conventional problems and to provide a small, lightweight and portable irradiance meter that quantitatively and accurately detect irradiance in a wide wavelength range from the ultraviolet region to the infrared region. .

Means for Solving the Problems The irradiance meter of the present invention is a pyroelectric radiation detection element, a transmissive diffusion structure that approximates its light-receiving angle sensitivity characteristic to a cosine law, and the pyroelectric radiation detection element An optical shutter that opens and closes the input radiation concentrically with respect to the center of the light receiving surface of the pyroelectric radiation detection element, and converts the photoelectric output from the pyroelectric radiation detection element into a DC output proportional to the amount of incident light. It is composed of a circuit for displaying.

Operation According to the above configuration, irradiance in a wide wavelength range from the ultraviolet region to the infrared region can be quantitatively and accurately detected by opening and closing the optical shutter once.

Example An example of an irradiance meter using an iris shutter that opens and closes electrically concentrically with a solenoid coil as an optical shutter will be described below as an example of the present invention with reference to the drawings.

FIG. 1 shows the light receiving part of the irradiance meter of this embodiment. In the figure, 1 is a pyroelectric type radiation detection element, 2 is a transmissive diffusion structure that approximates the incident angle sensitivity characteristic of the pyroelectric type radiation detection element 1 to a cosine law, 3 is an iris shutter that opens and closes electrically in concentric circles, 4 Is a solenoid coil for opening and closing the iris shutter 3.

The operating principle of the above device is shown below. Light E (t), which has a small temporal change as shown in FIG. 2, is made incident on the transmissive diffusion structure 2. At this time, when the iris shutter 3 is opened and closed with a time characteristic of Q (t), light of q (t) is incident on the pyroelectric radiation detection element 1. At this time, the change in incident light q (t)
Is as shown in FIG. 3 and is expressed by the following equation.

q (t) = E (t) · Q (t) (1) The pyroelectric radiation detection element 1 outputs an output proportional to the derivative of the incident light q (t) as shown in FIG. 4 (a). Generate a voltage R (t). R (t) is represented by the following equation.

R (t) = dq / dt (2) This output fluctuation is transient, and since it is a differential value, the amplitude of the voltage and the intensity of the incident are not proportional, so measure this voltage value. However, it does not measure the amount of incident light. Here, when the differential voltage R (t) is integrated by the integrating circuit, the output S (t) proportional to the incident light q (t) is obtained by the integration. That is, This is shown in FIG. 4 (b). The amplitude of this restored signal is E
(T) (average of values between t ₁ and t 2 in FIG. ₂ ). In reality, this integrated value is charged by charging a capacitor or the like, but since the charge is gradually discharged and attenuated, it is held by the sample hold circuit immediately after the end of the integration (t ₂ ).

In this device, the shutter opening time Δt = | t ₂ −t ₁ | is set sufficiently larger than the time constant of the differential response of the pyroelectric radiation detection element 1.

The measurement can be repeated any number of times by opening and closing the shutter at any time. Further, even if there is a variation in the operation of the shutter, if Δt is sufficiently large, the differential signal can be taken in completely, so the integrated value, that is, the measured value does not change.

Calibration of measured values may be performed, for example, by using a light bulb of known radiation amount and opening and closing the shutter in front of it, and measurement of dark input may be performed in front of a dark curtain at the same temperature as the ambient temperature. Good.

The light receiving angle sensitivity characteristic of the light receiver is approximated to the cosine law by the transmissive diffusion structure 2. The diffused light from the transmission / diffusion structure 2 is interrupted by the iris shutter 3 and enters the light-receiving surface of the pyroelectric radiation detection element 1. The iris shutter 3 is arranged near the light receiving surface of the pyroelectric type radiation detection element 1. At this time, the iris shutter 3 is electrically opened and closed by the solenoid coil 4 in a concentric pattern. By aligning the center of the concentric opening / closing of the iris shutter 3 with the center of the transmission / diffusion structure 2 and the center of the light-receiving surface of the pyroelectric radiation detection element 1, how the opening of the iris shutter 3 is temporally changed. Even in such a state, the light receiving angle sensitivity characteristic of the light receiver approximates to the cosine law. Therefore, the opening / closing of the iris shutter does not change the light receiving angle sensitivity characteristic of the light receiver with time, and does not impair the cosine law approximation.

The iris shutter is generally much lighter and thinner than a motor-driven rotating sector, and can have a larger angle of incidence from the pyroelectric radiation detection element, which is a light receiving element, than the rotating sector. . Further, unlike the rotating sector, it is not necessary to drive it constantly, and since the opening / closing operation is limited to only during measurement, power consumption is small. Therefore, the irradiance meter using the pyroelectric radiation detection element and the shutter has excellent characteristics even when it is portable.

EFFECTS OF THE INVENTION The present invention provides a pyroelectric radiation detecting element, a transmissive diffusing structure for approximating its angular sensitivity characteristic to a cosine law, and input radiation to the pyroelectric radiation detecting element, the pyroelectric radiation detecting element. With respect to the center of the light receiving surface, an optical shutter that opens and closes concentrically and is intermittent, and a circuit that converts the photoelectric output from the pyroelectric radiation detection element into a DC output proportional to the amount of incident light and displays the result.
It has the following effects.

(1) An irradiance meter that quantitatively and accurately detects irradiance in a wide wavelength range from the ultraviolet region to the infrared region can be configured by opening and closing the optical shutter once.

(2) The shutter is generally much lighter and thinner than a motor-driven rotating sector, and the angle of incidence from the pyroelectric radiation detection element, which is a light receiving element, can be set larger than that of the rotating sector. it can. At this time, since the optical shutter is opened and closed concentrically, the change in the light receiving angle sensitivity characteristic of the light receiver is small with time due to the opening and closing of the shutter. Therefore, it is possible to obtain the irradiance meter whose light-receiving angle sensitivity characteristic is close to the cosine law.

(3) The shutter does not need to be constantly driven like a rotating sector, and the opening / closing operation is limited to only during measurement, so power consumption is small. For this reason, the irradiance meter using the pyroelectric radiation detection element and the shutter is small and lightweight, and has excellent characteristics for portable use.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a light receiving portion of an irradiance meter in one embodiment of the present invention, FIG. 2 is a view showing a temporal change of light incident on the irradiance meter, and FIG. 3 is a pyroelectric radiation detecting element. FIG. 4 (a) shows the response output of the pyroelectric type radiation detection element, and FIG. 4 (b) shows the integrated response output of the pyroelectric type radiation detection element. It is a figure which shows the waveform integrated by the circuit. 1 ... Pyroelectric radiation detection element, 2 ... Transmission / diffusion structure, 3
...... Iris shutter, 4 ... Solenoid coil.

Claims (1)

[Claims] 1. A pyroelectric radiation detecting element, a transmissive diffusing structure for approximating a light-receiving angle sensitivity characteristic of the pyroelectric radiation detecting element to a cosine law, and an input radiation to the pyroelectric radiation detecting element. An optical shutter that opens and closes concentrically with respect to the center of the light receiving surface of the pyroelectric radiation detection element, and a circuit that converts the photoelectric output from the pyroelectric radiation detection element into a direct current output proportional to the amount of incident light and displays it. Irradiometer consisting of.