JPS62223636A - Light chopper device for photometry instrument - Google Patents

Abstract

PURPOSE:To freely change the attitude of an instrument without any special adjustment and to eliminate an error in measurement by automatically correcting the influence of the gravitational flexure of a light chopper which uses a bimorph body. CONSTITUTION:The light chopper 1 is fitted to the upper end of the bimorph body 2. The lower end of the bimorph body 2 is fixed to a base 3 and the upper end is in a free cantilever state; and the bimorph body flexes to right and left and the chopper 1 is also displaced accordingly as shown by arrows 1b and 1c. A light control plate 4 has an aperture 4a in the center and the chopper 1 covers the aperture to intercept light passing through the aperture and moves away from the aperture 4a to allow light to pass through the aperture. Then when the device is slanted to right or left, the bimorph body 2 flexes by its own weight and the weight of the chopper 1. The bimorph body 2 is at its standard attitude when set vertically and the chopper 1 shields the aperture 4a by a half while no voltage is applied to the bimorph body 2. The chopper 1 swings around this position to right and left and the time ratio of the interception of the light is equalized.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an optical chopper used in various photometric devices, and particularly to a vibrating optical chopper using a bimorph.

B. Conventional techniques 1.i In photometry, it is better to apply an alternating current to the 1= signal to remove the offset of the photometering circuit and improve the S/'N ratio. In order to remove the radiation noise from the
In many cases, the beam is incident on the beam. Conventionally, such an optical chopper has generally used a system in which a disc provided with an opening is rotated by a motor. However, this type of optical chopper is structurally large, and the higher the rotational precision of the motor, the more expensive it becomes, and the longer its lifespan becomes. Therefore, the fact that they are inexpensive, highly reliable, small and lightweight has started to attract attention.

By the way, in an optical converter using a bimorph, it is necessary to make the bimorph thin and long in order to obtain a sufficient amount of displacement for intermittent light. In other words, bimorph is a device in which two piezoelectric elements are pasted together and an electric current is applied so that one side stretches and the other side contracts.The amount of deflection at the tip of the bimorph is inversely proportional to the 1.5 to 2 power of the thickness, and 1.5 of the length. It is proportional to ~2, so in order to increase the deflection of the bimorph, it is necessary to make it thinner and longer.
This increases the ease with which the bimorph is deflected by external forces, and the amount of deflection due to the chopper's gravity changes depending on the orientation of the device, which may change the ratio of the light intermittent period and cause measurement errors. Although it is possible to manually correct the influence of the deflection caused by the electric power of the 5-chopper, it is difficult and troublesome to redo the correction each time the device is moved.

Problems to be Solved by the Invention The present invention automatically corrects the influence of gravitational deflection of an optical chopper using a bimorph, and freely changes the orientation of the photometric device without special adjustment scanning. The aim is to prevent mistakes in measurement from occurring.

Means for resolving the 23-hour residence A stage is provided to detect the constant change (i minutes) of the chopper held in the bimorph, the output of this detection means is converted into a DC voltage signal, and this voltage signal is A displacement of the chopper in the opposite direction to the constant displacement is fed back to the bimorph as a wet bias input.

The action chopper is held by a bimorph, and an alternating current voltage or positive and negative pulse voltages are applied to the bimorph to cause it to vibrate, thereby performing a chopping operation.

When the bimorph is vertical, there is no effect of gravity, but when the bimorph is horizontal or tilted, the center position of the chopper's vibration is shifted from when the bimorph is vertical due to the deflection of the bimorph due to gravity. This shift is what is referred to as permanent displacement in the previous section. When this deviation is detected and converted into a DC voltage signal, and this voltage signal is superimposed on the AC or pulsed voltage applied to the bimorph, the bimorph causes a constant displacement and returns to its displacement point. It will be made to vibrate around the center.

If we feed back this constant displacement to cancel out the constant deflection of the bimorph due to gravity,
The displacement of the chopper due to gravity is corrected, and no matter what direction the photometer is pointed, the displacement of the chopper due to gravity is corrected by automatically following the change in attitude, ensuring correct photometry at all times. Become.

EXAMPLES In the examples described below, the present invention is applied to a radiation thermometer.

Example 1. A first embodiment is shown in FIG. 1. In FIG. 1, reference numeral 1 denotes an optical chopper, which is attached to the upper end of the bimorph 2 by one inch. The lower end of Bimorph 2 is fixed to Isamu Base 3, and the upper end is a free cantilever beam, which bends left and right as shown in the figure.
In addition, the chopper 1 is also displaced in the direction of the force indicated by arrows 1b and lc. 4 has an aperture 4a in the center for light regulation, and when the chopper 1 covers this aperture, light passing through the aperture is blocked, and when the chopper 1 avoids 3A from the aperture 4a, the light passes through the aperture. No. 27, passing through, shows an aspect of this embodiment. In this figure, light passes through the opening 4a of the light regulating plate 4 from the left and right. The radiation thermometer measures the temperature of the subject by measuring infrared rays from the subject, and an infrared sensor 6 is placed immediately after the opening 4a.

The optical chopper 1 is arranged in front of the light regulating plate 4 at a position close to the plate.

When the above-mentioned device is tilted to the right or left in FIG.
At this time, when no voltage is applied to the bimorph 2, the chopper 1 is configured to block exactly half of the opening 4a of the light regulating plate 4, and the chopper 1 swings left and right around this position, causing intermittent light. The time ratios are made equal.

In the above-mentioned embodiment, two openings 4a and 4mu are arranged below the opening 4a of the light regulating plate 4 as a means for detecting the displacement of the chipper 1 due to gravity with respect to the vertical position of the bimorph 2. At the reference position, each of the apertures is shielded by half of its area by the chopper 1, and as shown in FIG. Photodiodes 5b and 5c were arranged as photodetecting elements.

With this configuration, when chopper 1 is not vibrating,
The same New Year's Day is incident on the diodes 5b and 5c, and their outputs are equal. When chopper 1 is vibrated in this state, the I output of four diodes 5c becomes an alternating current signal with the same frequency and equal amplitude. When the device is tilted, chopper 1 shifts to either the left or right side due to gravity. , for example to the right (
When q, the output of photodiode 51) increases and the output of 5c decreases, and when chopper 1 is vibrated in this state, an AC signal on which a DC component corresponding to the increase/decrease in output is superimposed is output from 5b and 5c. be done. In this way, the star of the DC component in the output signals of the photodiodes 5b and 5c is the detection signal of the threshold shift due to the gravity of the chopper 1, and this is converted into a DC voltage, amplified, and applied to the bimorph 2, and the gravitational force is applied to the bimorph 2. By generating a deflection force in the opposite direction to the deflection caused by
The above threshold shift is corrected.

FIG. 3 shows a circuit for performing the above-mentioned correction. Four diodes 5Ll and 5C are connected differentially to form a differential amplifier kn.
(Connected to the inverting terminal of 5A I. Since the increases and decreases in shielding by the chopper 1 of the openings 4b and 4c in the light regulating plate are opposite to each other, the order 1 of the AC signal output from the photodiodes 5b and 5c is They are shifted by half a period from each other, so in the output when 5b and 5c are connected differentially, the AC component is canceled out and the difference in the DC component is input to the differential amplifier A1. The non-inverting terminal is connected to the slider of the potentiometer 15a.At the reference position mentioned above, the DC components of the outputs of the photodiodes 5b and 5c are theoretically equal and the inverting terminal input of the differential amplifier A1 is 0.
Therefore, the non-inverting terminal input can be set to 0, but in reality, the difference in the characteristics of the photodiodes 5b and 5c, the aperture 4
Due to the shape error of b and 4c, the difference between the DC components of the outputs of 5b and 5c is not O, so the jt dynamic amplifier A1 at the reference position
Set the potentiometer 15E in advance so that the output becomes 0.
This is done by adjusting L. In this way, the output of the differential amplifier A1 corresponds to the difference in the DC component based on the gravity (threshold shift) of the chopper 1 in the outputs of the photodiodes 5b and 5c, and this is input to the non-inverting terminal of the amplifier A2. An AC signal for driving the chopper 1 is input from the terminal Sc to the inverting terminal of the amplifier A2.
is applied to bimorph 1. In this case, terminal Sc
If the input of the differential amplifier A is 0, the output voltage of the differential amplifier A will be applied to the bimorph 1 as is. Amplifier A2 is configured such that the polarity of this applied voltage causes bimorph 1 to deflect in the opposite direction to the deflection due to gravity.
The output side of is connected to the terminal of bimorph 1. Therefore, if the gain of Al is made sufficiently large, the deflection of the bimorph 1 due to gravity can be corrected by the output of A2. Terminal Sc
The AC signal for driving the bimorph that is input to A2 is as it is.
Since the applied force is reversed by , the chopper 1 maintains its normal position and vibrates even under the influence of gravity. Since the alternating current components of the outputs of the phytodiodes 5b and 5c of the capacitor 14b do not have completely the same amplitude due to dimensional errors in the apertures 5b and 5c and variations in the characteristics of the photodiodes 5b and 5c, some alternating current components remain in the output of the differential amplifier A1. Embodiment 2 was provided to absorb this and send only the complete DC component to the amplifier 3A2. In this embodiment, the output of the infrared sensor 6 shown in FIG. 1 is used to detect the displacement of the chopper 1 due to gravity. Therefore, structurally, it is the first.
In FIG. 2, the light regulating plate 4 does not have openings 4b and 4c, and there is no photodiode 5b.

Everything else is the same, just without 5C. Therefore, explanations of the JR construction drawing and the construction of this embodiment will be omitted. In this embodiment, the infrared sensor 6 is of a thermal type and converts the temperature rise of the element when receiving light for a certain period of time into an electrical signal, so it is a kind of integral type detection element. Figure 4 shows how the output waveform of the detection element of this type of radiation thermometer varies depending on the duty of intermittent light (the time ratio between the exposure period and the light shielding period). In this case, B shows the case where the exposure period is longer with the same period, and C shows the case where the light shielding period becomes longer.The element temperature during exposure is proportional to the intensity of the incident light at a place far from the saturation temperature. rises linearly,
Therefore, the output signal also increases linearly. During the light-shielding period, the element cools linearly, the output decreases in magnitude, and the output signal becomes a triangular wave signal. If you simply remove the DC component from this triangular wave f:, you will only get a triangular wave signal with equal positive and negative amplitudes, but once you differentiate it, you will see that the rising and falling periods of the triangular wave are of equal length in the case of Figure 4A. Therefore, the differential waveform becomes a rectangular wave with equal vertical amplitude as shown in FIG. 4a. Similarly, in the case of Figure 4B, the rising period is longer than the falling period, so the pulse height on the positive side is low and the pulse height on the negative side is high, as shown in the figure, resulting in a rectangular wave, and in the case of Figure 4C, Conversely, as in C, the positive pulse is high and the negative pulse is low, resulting in a rectangular wave. Therefore, the difference between the positive amplitude and the negative IJII amplitude of the differential waveform of the output of the photodetector element becomes a detection signal for the deviation of the optical chopper, so this signal is converted into a voltage signal and the bimorph is What is necessary is to provide feedback in a direction that cancels out the deflection.

FIG. 5 is a diagram showing the circuit configuration of the above-mentioned embodiment, in which 1 is an optical chopper, 2 is a bimorph, 4 is a light regulating plate, 4a is an aperture, and 6
are optical sensors, and their configuration is the same as that in FIG. The output of the sensor 6 is taken into the microcomputer 11 via the preamplifier 7, bandpass filter 8, double-wave rectifier 9, A/D 2t'AWg], O, is converted into a temperature display signal, and is output to the display means 12. . The output of the local preamplifier 7 is 1 consisting of a capacitor 15a and a resistor 15b.
The resultant signal is differentiated by the fractional circuit and inputted to the fitting output furnace output device 15. The output of the amplifier 15 is switched by a switching element 16 and smoothed by a circuit consisting of a resistor 14c and a capacitor 14d.

A sampling signal shown in FIG. 4 is applied from the microcomputer 11 to the switching element 16, and the positive and negative amplitudes of the differential signals of the sensor output shown in FIGS. 4a, b, c, etc. are sampled. In this way, the sampled positive and negative amplitudes (11) are smoothed, so the smoothed signal is the difference between the positive and negative amplitudes of the signals a, b, c, etc. in Figure 4 (signals corresponding to 11). This is applied to the non-inverting terminal of the output amplifier 14, and its output is applied to the bimorph 2 to correct the deflection of the bimorph due to gravity. A bimorph drive signal is applied through circuit 13. The function of this output amplifier 14 is exactly the same as amplifier A2 in the previous embodiment.

Effects Since the optical chopper of the present invention uses a bimorph, it has a simple structure, is lightweight, inexpensive, and has high reliability, and the influence of gravity, which is a drawback of this type of optical chopper, is automatically corrected. Therefore, the photometric device can be used in any position without any manual adjustment.

[Brief explanation of drawings]

1 (21) is a front view of an apparatus according to an embodiment of the present invention, FIG. 2 is a side view of the same embodiment, FIG. 3 is an I'I71!? Fig. 71 is a signal waveform diagram illustrating the operating principle of another embodiment of the present invention, No. 5171.
FIG. 2 is a circuit diagram of a signal processing section of the same embodiment.

Claims (1)

[Claims] means for detecting constant displacement of the optical chopper held by the bimorph; converting the output of this detection means into a DC voltage signal; and applying this voltage signal to the bimorph to cause constant displacement of the optical chopper; An optical chopper device for a photometric device, comprising means for feeding back as a bias input that causes bending in the direction of extinction.