JPH05126719A - Light modulation measuring device - Google Patents

Abstract

PURPOSE:To enable an irradiation light to be set to an optimum automatically by measuring light from a sample and then setting a specific irradiation light intensity and modulation amplitude based on each irradiation light intensity when the measured light output starts to be detected and saturation begins. CONSTITUTION:A computer 7 sets an AC output Jac of a modulation circuit 4 to 0 and a DC output Jdc to 0 according to an operation instruction for setting modulation from an operator. Then, Jdc is increased step by step, presence/ absence of an output of a photometry circuit 5 is checked, and then, if it is determined that there is an output, Jdc at that time Is stored as It. Furthermore, a difference between the last and current photometry outputs is obtained while increasing Jdc step by step, a timing when the difference becomes smaller than a specified value delta is detected, and then Jdc at that time is stored as Is. Then, an amplitude Jac of AC output of a circuit 4 is set as Jac= (Is-It)/2-d (d: a specified value) and a DC output is set as Jdc=(Is+It)/2, thus achieving a full-capacity measurement of a circuit 5 automatically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention irradiates a sample with light whose intensity is modulated and detects the transmitted light or scattered light which is attenuated while passing through the sample and measures the average intensity of the irradiated light. And a device for optimally setting the degree of modulation.

[0002]

2. Description of the Related Art When a sample analyzer of the type that irradiates a sample with intensity-modulated light to measure transmitted light or scattered light, the intensity of the measured light by the sample is the intensity of the irradiated light or the modulation rate. However, even if they are the same, the attenuation rate of light by the sample is significantly different, and therefore the values are different in a wide range. On the other hand, it is desirable that the photometric circuit be capable of performing photometry between the minimum value and the maximum value of the modulated light with the maximum gain without distortion. That is, the minimum value of the detected light that is transmitted through the sample or scattered becomes the minimum output in the range in which it exceeds the noise level of the photometric circuit, and the maximum value of the detected light becomes the maximum output in the distortion-free region of the photometric circuit. Therefore, it is necessary to set the average intensity and modulation degree of the irradiation light. These intensity and modulation control settings have to be set optimally every time because the average intensity of the light to be measured differs from sample to sample or by changing the measurement site even for the same sample. Conventionally, this setting must be done manually. I was going,
The measurement work was very troublesome.

[0003]

SUMMARY OF THE INVENTION The present invention is intended to automatically set the irradiation light average intensity and the modulation degree according to the sample.

[0004]

[Means for Solving the Problems] While irradiating a sample to be measured with light, the intensity of the light irradiating the sample is gradually increased from 0 without modulation, and the minimum intensity It at which a light detection signal is obtained from the photometric circuit is detected. Then, this is stored, and then the irradiation light is further strengthened to detect and store the irradiation light intensity Is when the output of the photometric circuit is saturated, and the irradiation light intensity center value is set to the minimum intensity It and the maximum intensity It. The intensity Is is set to the average (It + Is) / 2, and the modulation amplitude is set in consideration of an appropriate margin from (Is-It) / 2.

[0005]

Function: The sample to be measured is radiated with light, the light emitted from the sample is measured, and the intensity of the illuminating light is gradually increased from 0 with no modulation, and the illuminating light intensity I when the first photometric output is obtained is obtained.
t is the minimum intensity of the irradiating light that allows photometry for the sample. Similarly, the first irradiation light intensity I at which the photometric output is saturated is
s does not increase the photometric value even if the irradiation light is further increased,
That is, it means that the distortion of the measurement output only increases. Therefore, if the average of the irradiation light is set to (It + Is) / 2, the maximum possible modulation amplitude is (Is-It) / 2. Therefore, in actuality, if the modulation amplitude is set to be appropriately smaller than this, it is possible to perform measurement with the full dynamic range of the photometric circuit, and it is possible to perform measurement with maximum sensitivity.

[0006]

[Embodiment] In the embodiment described below, the light is irradiated to a proper place on the surface of the human body, and the light scattered inside the human body is detected on the surface away from the light irradiation point on the human body surface. The present invention relates to a medical examination method in which information on the inside of a human body is obtained by changing the distance between a point and a detection point. As shown in FIG. 1, the irradiation light is modulated into a sinusoidal waveform by an AC signal, and the object 1 is irradiated with this to detect the scattered light in the object at a place Q apart from the irradiation point P by L. The actual path of each photon of the scattered light detected at this time is complicated, but overall, it can be seen that the path like the arrow in the figure travels at a certain speed to reach the detection point. The time difference until the light that is incident on the point P at the same time is detected at the point Q depends on the length of the arrow path, and the irradiation light is modulated by the sine wave, so the AC component of the detection signal at the detection point is Is a composite of sinusoidal alternating currents that are out of phase by the time difference due to the path of light. Actually, due to the difference in the internal tissue of the human body of the subject, the attenuation factor differs for each path, so the phase shift of the detected AC signal with respect to the modulation signal of the irradiation light causes the state of internal tissue at a certain depth of the human body. You can get information about. By performing such measurement while changing the distance L, various changes in the depth direction of the human body can be detected. The present invention provides an algorithm for automatically setting the average intensity of irradiation light and the modulation depth optimally for each measurement in the above-described measurement.

A laser is used as a light source of the light with which the subject is irradiated. The intensity modulation of laser light is performed by increasing or decreasing the laser drive current. FIG. 2 shows the configuration of the entire apparatus. 2 is a light source laser, 3 is a photodetector, 4 is a light source modulation circuit, 5
Is a photometric circuit, 1 is a subject, for example, the hand of the subject,
The optical fiber 6 optically connects the surface of the subject and the photodetector 3, and the optical fiber 6 of the subject
The measurement is performed by changing the place Q to which the tip of is touched. The output signal of the photometric circuit 5 is A / D converted, taken into the computer 7, processed by the computer 7, and displayed on the display device 8 as medical examination data. The modulation circuit 4 is a circuit that adjusts both the direct current supplied to the laser and the alternating current superimposed on it, and is controlled by the output from the computer 7. Further, the photometric circuit 5 also has a built-in phase detection mechanism so that the phase shift of the output from the computer 7 can be detected.

FIG. 3 is a flowchart of the operation when the computer 7 sets the average intensity and the modulation amplitude of the laser light. When the operator gives a modulation setting operation instruction to the computer 7, the computer starts the operation of FIG. First, the computer outputs the AC output J of the modulation circuit 4.
Set ac to 0 and DC output Jdc to 0 (a), then increase Jdc by one step (b), check the output of photometering circuit 5 (c), and check that Jd
If c is increased and there is output, then Jd at that time
c is stored as It (d), Jdc is increased by 1 step (e), the difference between the current and previous photometric outputs is calculated, and when the difference becomes smaller than a predetermined value δ, it is detected (to ) And memorize Jdc at that time as Is (g)
Then, the amplitude Jac of the AC output of the modulation circuit 4 is set to Jac = (Is-It) / 2-d, and the DC output is set to Jdc = (Is + It) / 2 (H) to end the operation. d is a predetermined value. It should be noted that when the operator gives an instruction to start the measurement to the computer 7 without performing the operator's operation called the modulation setting and only performing the measurement start operation, the computer first executes the operation shown in FIG. 3 and then starts the measurement operation. You can

[0009]

According to the present invention, it is not necessary for the operator to set the average intensity of the irradiation light and the modulation degree for each measurement, and the capacity of the photometric circuit is automatically set to the maximum. , Can automatically perform measurement with the optimum settings.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an example of a measuring method to which the present invention is applied.

FIG. 2 is a block diagram of an apparatus for performing the above measurement.

FIG. 3 is a flowchart of an automatic setting operation in the above example.

[Explanation of symbols]

 1 subject 2 light source 3 photodetector 4 modulation circuit 5 photometric circuit 6 optical fiber 7 computer 8 display device

Claims (1)

[Claims] In a measuring device that irradiates a sample with intensity-modulated light and detects transmitted or scattered light from the sample, the average level of light intensity of the light source and the amplitude of modulation are made variable, and the light intensity is increased from 0 without modulation. However, the minimum light intensity level It at which the photometric output is obtained and the light intensity level I when the photometric output begins to saturate
s is detected and the average level of the light source is (It + Is) / 2
In addition, the optical modulation measuring device is provided with automatic setting means for setting the modulation amplitude appropriately smaller than (Is-It) / 2.