JPH0928678A - Apparatus for determining stress - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an apparatus for determining stress and obtaining an evaluation value with universality using the difference between a skin temperature of peripheral portion and a skin temperature of trunk portion without requiring a long time for the determination. SOLUTION: An infrared ray image of the face of a subject is detected by a thermocamera 1, each of the temperature data at the nose portion and the forehead portion are extracted by a time difference enumerating unit 2 of the stress determining circuit 7 and then the temperature difference ΔT between them is calculated. A stress estimation formula stored in an S-ΔT characteristic memory 4 is read out by an S-ΔT characteristics processing unit 3 of the stress determining circuit 7, the temperature difference ΔT enumerated before is substituted into the stress estimation formula, thereby a degree of stress S is calculated. The degree of stress S is output from a printer 5 and/or presented on a display 6. Thus the degree of stress can be determined based on the estimation formula on determination of stress in practice therefore changing of the estimation formula is not necessary for every subject thereby a reasonable degree of stress can be readily obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a state of tension, excitement,
Alternatively, the present invention relates to a stress measurement device that quantitatively measures a stress level in a stress state such as an awake state.

[0002]

2. Description of the Related Art Conventionally, a stress level has been evaluated in order to manage a self-health state. For example, chaos analysis is performed on measurement data of a pulse wave at a fingertip, and this is obtained. A device for estimating the degree of stress based on a chaos attractor has been proposed. In this device, the pattern of the chaotic attraction drawn on the display is visually determined, and the degree of stress is qualitatively evaluated.

[0003] It has been known that the skin temperature of a peripheral part such as a fingertip of a human decreases at the time of stress, and the amount of decrease in skin temperature is measured. It is possible.

[0004]

However, in the evaluation of the stress level based on the chaos attractor, there is a problem that it is difficult to quantitatively grasp the stress level. on the other hand,
Although a quantitative evaluation value can be obtained by the stress level evaluation method based on the amount of decrease in peripheral skin temperature, there is individual difference in the amount of decrease in peripheral skin temperature due to stress load, and universal stress There is a problem that the evaluation value of degree cannot be obtained. In addition, in order to accurately measure the amount of decrease in skin temperature from a resting state, it is necessary to maintain a resting state until the skin temperature becomes constant. Changes in temperature and humidity cause errors due to differences in the environment.

An object of the present invention is to provide a stress measuring apparatus which can obtain a universal evaluation value and does not require a long time for measurement.

[0006]

A stress measuring device according to the present invention is a temperature for measuring a temperature difference ΔT between skin temperatures of a peripheral part (eg, nose part) and a trunk part (eg, forehead part) of a human body exposed to the outside. A difference measuring means and a stress estimation formula that expresses the stress level S as a linear expression of the temperature difference ΔT, wherein an average value of the temperature differences ΔT when various stresses are applied to a large number of subjects is the stress level S. A memory means storing a predetermined stress estimation formula in which a proportional coefficient is determined so as to be within a range of 40% to 60% of the entire scale (for example, 50%) and a stress estimation formula stored in the memory means. Based on the measured value of the temperature difference ΔT, a stress degree calculating means for calculating the stress degree S and an output means for outputting the calculated stress degree are provided.

Specifically, the stress estimation formula is expressed by the following equation (2).

S = 33.59 × ΔT where S = 0 when S <0, S = 100 when S> 100

[0008]

In the present invention, the difference ΔT between the peripheral skin temperature and the trunk skin temperature is used to evaluate the degree of stress. Peripheral skin temperature changes depending on the level of stress,
As the stress level increases, the skin temperature in the peripheral area decreases.
In addition, if the environmental conditions such as environmental temperature and humidity change, the skin temperature of the peripheral area also changes. On the other hand, the skin temperature of the trunk does not change depending on the magnitude of stress, but changes only according to changes in environmental conditions. Therefore, if the difference between the skin temperature at the peripheral portion and the skin temperature at the trunk is taken, the temperature change component due to the change in environmental conditions is canceled out, and the temperature difference becomes an index representing only the magnitude of the stress level. Further, according to the difference between the skin temperature of the peripheral portion and the skin temperature of the trunk, the resting state is not used as a standard as in the conventional case, so that the temperature measurement value may be an instantaneous value and the measurement does not take time.

In the present invention, an experiment is performed in which various stresses are applied to a large number of subjects in advance and the temperature difference ΔT is actually measured, and the average value of the measured data is calculated. Then, the proportionality coefficient is determined so that the average value of the temperature difference ΔT is about 50% of the entire scale of the stress level S, and a linear stress estimation equation is derived. In this preliminary experiment, since various stresses are applied to a large number of subjects, the temperature difference ΔT for each subject depends on the degree of the stress applied to each subject and the individual difference in the sensitivity of each subject to stress. Will be statistically distributed accordingly. Here, if the average value of the temperature difference ΔT is taken, it is considered that the average value corresponds to the temperature difference when the degree of stress is about 50%. Therefore, the derived stress estimation formula is obtained by statistically processing individual differences,
It is a universal expression of the relationship between stress level and temperature difference.

In the actual measurement of the stress level, the skin temperatures of the peripheral part and the trunk of the human body are simultaneously measured, and the temperature difference ΔT between them is calculated. Then, the stress level corresponding to the temperature difference ΔT is calculated based on the stress estimation formula.

[0011]

According to the stress measuring device of the present invention, a universal and quantitative stress level can be obtained. Needless to say, in the measurement of skin temperature, measurement in a resting state is unnecessary, and an instantaneous value may be captured, so that a long time is not required for measurement.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows the structure of a stress measuring device, which is equipped with a thermo camera (1) for measuring the skin temperature of the nose, which is the peripheral part, and the forehead, which is the trunk. The thermo camera (1) is connected to a stress measurement circuit (7) composed of a microcomputer or the like, and a stress level S derived by the circuit is output to a printer (5) and / or a display (6). .

The stress measurement circuit (7) is a thermo camera
A temperature difference calculation unit (2) that extracts temperature data of the nose and forehead from the infrared face image captured by (1) and calculates a temperature difference ΔT between the two, and stress based on the calculated temperature difference ΔT. An S-.DELTA.T characteristic processing unit (3) for calculating the degree S, and an S-.DELTA.T characteristic memory (4) storing a predetermined stress estimation formula.

The stress estimation formula stored in the S-ΔT characteristic memory (4) is as follows: Th forehead skin temperature and T for nose skin temperature.
n is represented by the following equation (3).

S = 33.59 × (Th−Tn) where S <0, S = 0, and S> 100,
S = 100. As a result, the stress level S becomes 0-1.
It is represented in the range of 00.

Next, various types of measurement data that are the basis of the stress measurement method according to the present invention will be described. FIG.
The result of the preliminary experiment for 117 subjects is shown. In the preliminary experiment, skin temperature and nose in the forehead in a resting state and various stress load states (tracking work to track one point moving on the screen by mouse operation, auditory stimulation by stimulation sound of different sound pressure, etc.) Measure skin temperature,
7 is a graph showing a relationship between two skin temperatures. As shown in the figure, the skin temperature varies depending on the subject when there is no stress, that is, at rest, but in all subjects, the skin temperature shows almost the same value in the forehead and nose. On the other hand, in a stressed state, the nose skin temperature is lower than the forehead skin temperature and varies.

At rest, as shown in FIG. 3, the nose skin temperature and the forehead skin temperature are substantially the same in all subjects.
Naturally, the forehead is the torso, and its skin temperature does not change depending on the load of stress. Therefore, as a reference value of the decrease in the nasal skin temperature, the forehead is replaced with the nasal skin temperature at rest. Skin temperature can be adopted.

In a stress load state, the temperature difference between the nose skin temperature and the forehead skin temperature fluctuated as shown in FIG. 4, and the average value was 1.49 ° C. In preliminary experiments,
Since various stresses are applied to a large number of subjects, the temperature difference ΔT for each subject is determined statistically according to the degree of stress applied to each subject and individual differences in the sensitivity of each subject to stress. Will be distributed. Here, if the average value of the temperature difference ΔT is taken, it is considered that the average value corresponds to the temperature difference when the degree of stress is about 50%.

Therefore, when the temperature difference ΔT is 1.49 ° C.,
The stress level S is 50, and the temperature difference ΔT is 2.98, which is twice as large
In the case of ° C., the stress estimation formula of the above equation 3 was derived with the stress degree being 100. Note that the estimation formula of Equation 3 is
Since the derivation is based only on data in the range of 34 ° C. <Th <36 ° C., the condition is satisfied only in this range.

FIG. 4 is a plot of only the temperature measurement data under the stress load condition, and shows the relationship between the nose skin temperature and the forehead skin temperature when the stress degree is 50 and 100 as described above. Indicated by a broken line. As shown in the drawing, the temperature measurement data varies substantially evenly around a broken line with a stress level of 50.

FIG. 5 shows the temporal changes of the forehead skin temperature, the nose skin temperature, and the stress degree calculated by the above equation (3) for a specific subject. Here, after the eyes were kept at rest, psychological evaluation was performed using the questionnaire shown in FIG. 6, and after that, the work for stress load was performed through the eyes closed at rest. After a psychological evaluation using a questionnaire and a closed eyes, a psychological evaluation was finally performed using a questionnaire.

As shown in the figure, when the eyes are at rest, the stress level is low and the stress level increases during the work. From this graph, the stress level according to the estimation formula of the present invention accurately represents the change in the stress load state. It can be said that.

FIG. 7 shows various stress load states of 168 subjects at an ambient temperature of 25 ° C.
(Video game, addition by mental arithmetic, appreciation of video), the horizontal axis indicates the stress estimation result by Equation 3, and the vertical axis indicates the subjective stress report value (0 to 100) from the subject. It is. As the subjective stress report value, an item having the highest reported value was selected from the question items of the questionnaire shown in FIG. 6, and the reported value was used as the subjective stress report value.

When the correlation between the stress estimation result and the subjective stress report value was examined, the correlation coefficient between them was r =
As high as 0.511, the validity of the stress estimation formula of the present invention was proved. Accordingly, the proportional coefficient 33.59 of the above equation (3)
Is a statistical numerical value derived from the average value of the temperature difference ΔT, but represents a universal characteristic relating to human stress, and is considered to have physiological significance.

As described above, a certain functional relationship is established between the stress level S and the temperature difference ΔT because the nose skin temperature is subtracted from the forehead skin temperature to obtain the environmental conditions such as environmental temperature and humidity. It is considered that this is because the temperature change component due to the change is offset, and the nose skin temperature is largely changed by the stress load, whereas the forehead skin temperature is not affected by the stress.

In the stress measuring apparatus of FIG. 1, the stress estimation formula of the above-mentioned equation 3 is stored in the S-ΔT characteristic memory (4), and the stress level is actually measured according to the procedure shown in FIG. First, in step S1, an infrared face image of a subject is detected by the thermo camera (1). In step S2, the temperature difference calculation unit of the stress measurement circuit (7)
After the temperature data of the forehead and nose are extracted by (2), the temperature difference ΔT is calculated in step S3.

Next, in step S4, a stress measurement circuit
The S-ΔT characteristic processing unit (3) of (7) is an S-ΔT characteristic memory
The stress estimation formula stored in (4) is read out, and the calculated temperature difference ΔT is substituted into the stress estimation formula,
The stress level S is calculated. The stress level S calculated in this way is determined by the printer (5) and / or
Alternatively, the value is output to the display (6), and the value is displayed. After that, in step S6, it is determined whether or not the measurement is to be terminated, and then the measurement processing is terminated.

In the above-mentioned stress measuring device, a stress estimation formula that can be universally applied to a plurality of subjects is derived based on the result of the preliminary experiment. Is calculated,
It is not necessary to switch the stress estimation formula for each subject, and a reasonable degree of stress can be easily obtained. or,
In measuring skin temperature, without waiting for a steady state,
Since an instantaneous value only needs to be captured, quick measurement is possible.

The description of the above embodiments is for the purpose of illustrating the present invention and should not be construed as limiting the invention described in the claims or reducing the scope thereof. Further, the configuration of each part of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made within the technical scope described in the claims.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of a stress measurement device according to the present invention.

FIG. 2 is a flowchart illustrating a process at the time of stress measurement.

FIG. 3 is a graph showing the relationship between forehead skin temperature and nose skin temperature in a stress-free state and a stressed state.

FIG. 4 is a graph in which a straight line representing a stress level of 50 and a stress level of 100 is entered in the same relation in a stressed state.

FIG. 5 is a graph showing changes over time in skin temperature and stress level.

FIG. 6 is a diagram showing a questionnaire used in the experiment.

FIG. 7 is a graph showing a correlation between a stress estimation result and a subjective stress report value.

[Explanation of symbols]

 (1) Thermo camera (2) Temperature difference ΔT calculation unit (3) S-ΔT characteristic processing unit (4) S-ΔT characteristic memory (5) Printer (6) Display (7) Stress measurement circuit

Claims (2)

[Claims] 1. A stress measuring device for measuring a stress level applied to a human body, comprising: a temperature difference measuring means for measuring a temperature difference ΔT between a skin temperature of a trunk of a human body and a skin temperature of a peripheral part of the human body; In the stress estimation equation expressed as a linear expression of the temperature difference ΔT, the average value of the temperature difference ΔT when various stresses are applied to many subjects is the stress level S.
Based on the stress estimation formula stored in the memory means, the predetermined stress estimation formula is stored, and the proportional coefficient is determined so as to fall within the range of 40% to 60% of all scales of A stress measuring device comprising: a stress degree calculating means for calculating the stress degree S from an actual measured value of the difference ΔT; and an output means for outputting the calculated stress degree. 2. The stress measuring device according to claim 1, wherein the stress estimation formula is represented by the following formula 1. ## EQU1 ## S = 33.59 × ΔT However, when S <0, S = 0. When S> 100, S = 100.