WO2005015138A1

WO2005015138A1 - Ultraviolet light measure

Info

Publication number: WO2005015138A1
Application number: PCT/KR2004/002021
Authority: WO
Inventors: Se Hoon Koh; Kyun Chae Koh
Original assignee: Alphacube Co., Ltd.
Priority date: 2003-08-11
Filing date: 2004-08-11
Publication date: 2005-02-17

Abstract

The present invention relates to a personal UV meter. The UV meter includes a sensor unit having a first sensor for measuring UV rays B(UV-B) having a wavelength of 280 to 320 nm that causes a burn in the skin, and/or a second sensor that measures UV rays A(UV-A) having a wavelength of 310 to 400 nm that makes the skin dark, a display unit that displays the intensity of UV rays measured in the UV sensor as an UV index, a sun protect index (SPF or PFA) and a possible UV exposure time, a calculation unit that calculates a value displayed on the display unit, an alarm unit that issues an alarming sound when the skin is exposed to the UV before a time set in the display unit elapses.

Description

ULTRAVIOLET LIGHT MEASURE

Technical Field

The present invention relates to a personal ultraviolet (UV) meter. More particularly, the present invention relates to a personal UV meter in which light having a wavelength of 280 to 400nm that is

harmful to the human body is received to a photodiode composed of gallium nitride (GaN), a sensitivity characteristic of the photodiode and an UV filter are assembled, and the bombed amount of UV rays is

measured using a sensor for receiving UV rays that is the closest to characteristics of an erythema response and a blackening response of the skin for UV rays.

Background Art Cosmetics that block UV rays are sold with a sun protect effect indicated as a sun protect index (SPF and PFA). SPF indicates a

multiple of time consumed when the skin gets burned. If a person who

gets burned when being exposed to UV rays for 10 minutes is applied with cosmetics of SPF 10, he cannot get burned for a time of 10 times,

i.e., for 100 minutes. PFA index indicates a multiple of time consumed when blackening occurs, which indicates that the skin is

blackened. If a person who gets blackened when being exposed to UV rays for 30 minutes is applied with cosmetics of PFA 4, he cannot get blackened for a time of 4 times, i.e., for 120minutes. However, most people do not know a method of deciding the sun

protect index suitable for his skin and also do not know how long his skin can be protected using UV block cosmetics. Therefore, there is a need for a personal UV meter that is capable of deciding a suitable^' sun protect index depending upon the intensity of UV rays and a skin

type. A user can receive information on skin care and health by using this meter.

Disclosure of Invention Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a personal ultraviolet (UV) meter that measures the intensity to generate a cleansing/blackening response and exactly calculates a safe exposure time when a sun protect agent is applied and the sun

protect agent is not applied depending upon the type of the skin by using a sensor having a light receiving characteristic that is mated with a cleansing/blackening response characteristic of the skin for UV

rays through combination of a sensitivity characteristic of a gallium

nitride photodiode disclosed in Korea Patent Publication No.2003- 0061704 (Date: 22 July 2003) and an UV filter.

Another object of the present invention is to provide a personal UV meter in which the intensity to generate a cleansing/blackening response is measured, and information on a recommended sun protect index (SPF(Sun Protect Factor), PFA (Protection Factor of UV-A)) necessary for safe exposure for an inputted exposure time by using a sensor having a light receiving characteristic that is suitable for a cleansing/blackening response characteristic of the skin for UV rays

through combination of a sensitivity characteristic of a photodiode and an UV filter. Still another object of the present invention is to provide a personal UN meter using a gallium nitride photodiode, which is cheap

and portable and has high efficiency. To achieve the above objects, according to the present invention, there is provided an UV meter, including: an UV sensor for measuring an UV-B index being an erythema response sensitivity characteristic of incident light, a microcomputer for performing an operation based on

the UV-B index measured in the UV sensor and a skin type index and SPF

that are inputted through an input unit to decide a safe exposure time, and a display unit for displaying the safe exposure time that is decided in the microcomputer.

It is preferred that the safe exposure time (minutes) when a sun protect agent is applied according to the SPF index is calculated according to the following equation:

Safe exposure time [minutes] = Minimum cleansing amount by the

skin type [MED] ÷ The amount of light per minute by the LN-B index [mJ/crf] x SPF index It is preferred that the safe exposure time (minutes) when a sun protect agent is not applied according to the SPF index is calculated according to the following equation: Safe exposure time [minutes] = Minimum cleansing amount by the skin type [MED] ÷ The amount of light per minute by the UV-B index

Meanwhile, according to the present invention, there is provided an UV meter, including an UV sensor for measuring an UV-B index being an erythema response sensitivity characteristic of incident light, a microcomputer for performing an operation based on the UV-B index measured in the UV sensor and a skin type index and an exposure time that are inputted through an input unit to decide a recommended SPF index, and a display unit for displaying the SPF index that is decided in the microcomputer.

It is preferred that the microcomputer calculates SPF according to the following equation:

SPF = The amount of light per minute by the UV-B index [mJ/cπf] X Going-out time [minutes] ÷ Minimum cleansing amount by the skin type (MED)

Meanwhile, according to the present invention, there is provided an UV meter, including an UV sensor for measuring an UV-B index being

an erythema response sensitivity characteristic of incident light, a microcomputer for performing an operation based on the UV-B index

measured in the UV sensor and a skin type index that inputted through an input unit to decide a safe exposure time of the skin on which a

sun protect agent is not applied, and a display unit for displaying the safe exposure time of the skin on which the sun protect agent is not applied, which is decided in the microcomputer. It is preferred that the UV sensor comprises a photodiode that converts an inputted optical signal into an electrical signal, an UV filter that is disposed in an optical path before an incident light

reaches the photodiode, and a measurement unit electrically connected

to the photodiode, for measuring the amount of the converted electrical signal to determine a corresponding UV-B index from the amount of the measured value, wherein in at least some of periods 280 nm to 320 nm wavelength, transmissivity of the UV filter is formed so that the ratio of a relative amount of a value corresponding to a

product of transmissivity of the UV filter and a relative response intensity of the photodiode for respective wavelengths corresponds to

the ratio of a relative amount of the relative response intensity on a blackening response spectrum curve on the curve of the skin for

respective wavelengths.

Meanwhile, according to the present invention, there is provided an UV meter, including an UV sensor for measuring an UV-A index being

an erythema response sensitivity characteristic of incident light, a microcomputer for performing an operation based on the UV-A index measured in the UV sensor and a skin type index and a PFA index that are inputted through an input unit to decide a safe exposure time, and

a display unit for^' displaying the safe exposure time that is decided in the microcomputer. It is preferred that the safe exposure time (minutes) when a sun

protect agent is applied according to the SPF index is calculated according to the following equation: Safe exposure time [minutes] = Minimum blackening amount by the skin type [MPD] ÷ The amount of light per minute by the UV-A index

[mJ/cn] X PFA index It is preferred that the safe exposure time (minutes) when a sun

protect agent is not applied according to the SPF index is calculated according to the following equation: Safe exposure time [minutes] = Minimum blackening amount by the skin type [MPD] ÷ The amount of light per minute by the UV-A index

an erythema response sensitivity characteristic of incident light, a microcomputer for performing an operation based on the UV-A index

measured in the UV sensor and a skin type index and an exposure time that are inputted through an input unit to decide a recommended PFA index, and a display unit for displaying the PFA index that is decided in the microcomputer.

It is preferred that the microcomputer calculates the PFA index

according to the following equation: PFA = The amount of light per minute by the UV-A index[J/cπ] x Going-out time [minutes] ÷ Minimum blackening amount by the skin

type (MPD) Meanwhile, according to the present invention, there is provided an UV meter, including an UV sensor for measuring an UV^~A index being an erythema response sensitivity characteristic of incident light, a microcomputer for performing an operation based on the UV-A index

measured in the UV sensor and a skin type index that inputted through an input unit to decide a safe exposure time of the skin on which a sun protect agent is not applied, and a display unit for displaying the safe exposure time of the skin on which the sun protect agent is

not applied, which is decided in the microcomputer. It is preferred that the UV sensor comprises a photodiode that

converts an inputted optical signal into an electrical signal, an UV filter that is disposed in an optical path before an incident light

reaches the photodiode, and a measurement unit electrically connected to the photodiode, for measuring the amount of the converted

electrical signal to determine a corresponding UN-B index from the

amount of the measured value, wherein in at least some of periods 310 nm to 400 nm wavelength, transmissivity of the UV filter is formed so that the ratio of a relative amount of a value corresponding to a product of transmissivity of the UV filter and a relative response intensity of the photodiode for respective wavelengths corresponds to the ratio of a relative amount of the relative response intensity on a

blackening response spectrum curve on the curve of the skin for

respective wavelengths. It is also possible to perform the operation using the amount of an electrical signal that is generated from a photodiode by means of light that passes through an UV filter instead of ideal UV-B index and UV-A index.

Brief Description of Drawings Further objects and advantages of the invention can be more fully understood from the following detailed description taken in

conjunction with the accompanying drawings in which: FIG. 1 is a block diagram showing the construction of a 2

channels UV meter of the GaN type in which first and second UV sensors having a 1-channel for measuring an erythema response sensitivity characteristic and a 2-channel for measuring a blackening response

sensitivity characteristic are used according to the present invention;

FIG. 2 is a block diagram of a 1-channel UV meter of a the gallium nitride type in which an UV sensor for measuring one of an erythema response sensitivity characteristic and a blackening response sensitivity characteristic is used according to the present invention; FIGS. 3a and 3b show light receiving units 200 and 200' for the UN meter of the GaΝ type according to the present invention; FIG. 4 is a graph showing representative UV transmissivity of the light receiving units 200 and 200' shown in FIGS. 3a and 3b;

FIG. 5 is a graph showing the relationship between responsivity of the GaΝ photodiode and respective wavelengths of UV rays! FIG. 6 is a graph showing the relationship between an erythema response spectrum that indicates the degree of skin damage by UV rays and responsivity of the GaΝ photodiode that reacts upon UV rays having a wavelength of 280 to 320nm that pass through an l-N filter according

to the present invention; FIG. 7a is a graph showing optimum blackening responsivity of

the UV meter of the gallium nitride type according to the present

invention; FIG. 7b is a graph showing filter UV transmissivity of a blackening response sensor! and FIG. 8 is a flowchart illustrating the operation of the 2-

channel UV meter of the GaΝ type. Best Mode for Carrying Out the Invention The present invention will now be described in detail in connection with preferred embodiments with reference to the accompanying drawings. FIG. 1 is a block diagram showing the construction of a 2 channels UV meter of the GaN type in which first and second UV sensors having a 1-channel for measuring an erythema response sensitivity characteristic and a 2-channel for measuring a blackening response sensitivity characteristic are used according to the present invention.

FIG. 2 is a block diagram of a 1-channel UV meter of a gallium nitride type in which an UV sensor for measuring one of an erythema response sensitivity characteristic and a blackening response sensitivity characteristic is used according to the present invention. As can be seen from FIG. 2, in FIG. 2, only one of the first channel for sensing the erythema response and the second sensors for sensing the blackening response in FIG. 1 is adopted. Thus, description on them

will be omitted and only FIG. 1 will be described in detail. In FIG. 1, a power supply unit 10 is connected to an operational

unit (microcomputer) 50 and supplies power. An oscillating unit 11 is

connected to the microcomputer 50 and outputs a signal of a given frequency to the microcomputer 50.

A real time clock (RTC) unit 12 is connected to the

microcomputer 50 and supplies current date, time, etc. to the microcomputer 50. In order to operation the time of the RTC unit 12, an oscillator (not shown) having a predetermined period is connected to the RTC unit 12. In this time, a standard period is 32,768-KHz. A

clock of this period operates the time of the UV meter, or a clock supplied is divided into given periods and is used for calculation in the microcomputer 50.

A switch 13 is connected to the microcomputer 50 and has various keys such as Next Key, Set key, Up key and Down Key for setting the skin type index, a PA value, a SPF value, an exposure time, a time,

etc. A first sensor 20 is an erythema response UV sensor for

converting an optical signal into an electrical signal and is connected to the microcomputer 50. The first sensor 20 measures the relative intensity indicating how easily light incident to a receiving window of the UV meter from the outside generates the erythema response in at least some of periods of wavelength 280 to 320nm that

contributes the erythema response. To this end, an UV filter is preferably disposed along the incidence path of light so that the light can pass through the filter with different transmissivity by the

wavelength and a photodiode measures the intensity of the light. The photodiode has unique relative response intensity by the

type and wavelength. It is preferred that a product of transmissivity

of the UV filter by the wavelength and the relative intensity of the photodiode is consistent with the erythema response spectrum that indicates the relative intensity that contributes an erythema response by the wavelength by controlling transmissivity by the wavelength of the UV filter. In this time, the UV filter is formed by depositing plural layers of coating materials on UV transparent glass. Quartz,

sapphire, optical glass, etc. can be selectively used as the UV

transparent glass. A high refractive index UV coating material that is repeatedly deposited on the UV transparent glass may selectively

employ one of A1₂0₃, Sb₂0₃, CaF₂₎ CaF₃, Hf0₂, LaF₃, NaF₃₎ Pr₂0₃, Pr₆0n, Na₃AlF₆, Ta₂0₅, ThF₄, YbF₃, Y₂0₃, Zr0₂ and the a low refractive index UV coating material may selectively employ one of Si0₂, SC2O₃, MgF₂, ZnSe, Ge, sulfide(Oxides), fluorides and ZnS. It is preferred that the UV

filter has transmissivity for UV rays in at least some of periods of 280nm to 320nm of the entire UV band and very low transmissivity in other regions.

A second sensor 21 is a blackening response UV sensor for

converting an optical signal to an electrical signal and is connected to the microcomputer 50. The second sensor 21 measures the relative

intensity indicating how easily light incident to the receiving window of the UV meter from the outside generates the erythema response in at least some of periods of wavelength 310 to 400nm that mainly

contributes the erythema response. To this end, an UV filter is preferably disposed along the incidence path of light so that the light can pass through the filter with different transmissivity by the wavelength and a photodiode measures the intensity of the light. The

photodiode has unique relative response intensity by the type and wavelength. It is preferred that a product of transmissivity of the UV filter by the wavelength and the relative intensity of the photodiode is consistent with the erythema response spectrum that indicates the relative intensity that contributes an erythema response by the wavelength by controlling transmissivity by the wavelength of the UV filter The second sensor 21 corresponds to sensors (200 and 200' shown in FIGS. 3a and 3b) for obtaining UV-A Index depending upon a blackening response action spectrum wavelength of 310 to 400nm and

measures UV-A Index being a blackening response sensitivity

characteristic. The sensors 200 and 200' used in the present invention are

shown in FIGS. 3a and 3b, and UV light transmissivity, a sensitivity characteristic and a response characteristic curve for the sensors 200

and 200' are shown in FIGS. 4 to 7b.

FIGS. 3a and 3b show the light receiving units (sensor) 200 and

200' of the meter of the GaN type. In FIGs. 3a and 3b, reference numerals 101 and 101' indicate casings of the meter of the GaN type.

Reference numerals 201 and 201' and 202 and 202' indicate quartz lens for focusing light regardless of a light-receiving angle. This lens is preferably a fly-eye lens. If the light-receiving sensor is 1, it is preferred that a common lens is used. If two sensors are mounted in the meter, the lens is improved considering exactness,

assembly property, design, etc. of the sensor. Reference numerals 204 and 204' and 205 and 205' indicate GaN photodiode sensors. This

photodiode sensor is mounted in a semiconductor chip (not shown). The quartz lens 201 and 202 are disposed corresponding to the sensors 204 and 205 and the quartz lens 201' and 202' are disposed corresponding to the sensors 204' and 205' . The quartz lens 201 and 201' and the sensors 204 and 204' can be spaced apart from the lens 202 and 202' and the sensors 205 and 205' by some distance so that they correspond one another. Further, the quartz lens 201 and the sensor 204 can be disposed separately from the quartz lens 202 and the sensor 205. FIG. 4 is a graph showing representative UV transmissivity of the light receiving units 200 and 200' of the GaN type meter shown in FIGS. 3a and 3b. FIG. 5 is a graph showing the relationship between

responsivity of the GaN photodiode and respective wavelengths of UV rays. As shown in FIGS. 4 and 5, the UV filter usually transmits UV

rays whose wavelength is 280 to 320nm. The GaN photodiode responds in

almost the same characteristic as an erythema response spectrum curve defined in CIE (Commission Internationale de I'Eclairage) as shown in

FIG. 6 in response to UV rays having a wavelength of 280 to 320nm that transmits the UV filter. FIG. 6 is a graph showing the relationship between an erythema response spectrum that indicates the degree of skin damage by UV rays and responsivity of the GaN photodiode that reacts upon UV rays having a wavelength of 290 to 320nm that pass through an UV filter according to the present invention; FIG. 7a is a graph showing optimum blackening responsivity of

the UV meter of the gallium nitride type according to the present invention and FIG. 7b is a graph showing filter UV transmissivity of a blackening response sensor. A storage unit 40 shown in FIG. 1 stores data measured in the first and second UV sensors 20 and 21 or data inputted to an input

unit. The microcomputer 50 performs a predetermined operation based on received data, stored data or the data measured in the UV sensor and controls a display unit to display the calculated results.

The microcomputer 50 can decide a safe exposure time by performing an operation based on the intensity of light or an UV-B

index which is measured in the UV sensor and a skin type index and SPF

which are received through the input unit. Meanwhile, the microcomputer 50 can decide a recommended SPF by performing an operation based on the intensity of light or an UV-B

index which is measured in the UV sensor and a skin type index and an exposure time which are received through the input unit. Also, the microcomputer 50 can decide a safe exposure time of the skin on which a sun protect agent is not applied by performing an operation based on the intensity of light or an UN-B index which is measured in the UV sensor and a skin type index which is received through the input unit. In addition, the microcomputer 50 can decide a safe exposure

time by performing an operation based on the intensity of light or an UV-A index that is measured in the UV sensor and a skin type index and

a PFA index that are received through the input unit. Further, the microcomputer 50 can decide a recommended PFA index by performing an operation based on the intensity of light or an UV-A index that is measured in the UV sensor and a skin type index and an exposure time which are received through the input unit. Furthermore, the microcomputer 50 can decide a safe exposure time of the skin on which a sun protect agent is not applied by

performing an operation based on the intensity of light or an UV-A index that is measured in the UV sensor and a skin type index that is

received through the input unit.

The safe exposure time, etc. that is decided in the microcomputer 50 is displayed on the display unit. The display unit

includes a predetermined display on which numbers can be displayed.

The intensity of a data incident light measured in the UN sensor, an UV-B index, an UV-A index, SPF, a PFA index, etc. are inputted. There is a table in which a reference table (see Table 1) by the user' s skin type. Table 1: Reference table by the skin type

Table 2: Minimum cleansing amount by the skin type, and the intensity of radiation per minute by the UV-B index

Table 3: Minimum blackening amount by the skin type, and the intensity of radiation per minute by the UV index

Erythema Response Time and Blackening Response Time

1) SPF Index (UV-B Index) The first UV sensor 20 measures the intensity regarding how strong UV rays will generate an erythema response using the photodiodes sensors 204 and 204' that obtain the erythema response of the skin for UV rays through combination of a sensitivity

characteristic of the photodiode and the UV filter and UV transparent lens 201 and 201' . This value can be converted to an UN index. Thereby, it is possible to induce a formula for calculating a safe exposure time depending upon the skin type by directly examining the

type of a skin response to UV rays with response to an adult. Safe exposure time (TMED; minute) where a sun protect agent is not applied by SPF = Minimum cleansing amount by the skin type (MED)

÷ The amount of light per minuet by the UN-B index [mJ/cD] (A)

Table 4: Minimum cleansing amount by the skin type and amount of light by the UN-B index and an expected MED arrival time [minute]

Although the UV-B index is subdivided into 15 steps in Table 4, the present invention is not limited to it. ^• It will be evident that the UV-B index can be divided into several steps, as described above, and the intensity of radiation per minute by the index can be also divided. For explanation' s convenience, only UV indices 1 and 15

have been described in the skin types 1 to 6. Those skilled in the art will easily know a safe exposure time for the UV indices 2 to 14 from the above description.

Furthermore, the minimum cleansing amount by the skin type is

set based on clinical demonstration made by the inventor and the fact that is generally known. That is, MED 20 is a value to generate an

erythema response when a person whose a skin type is 1 is exposed to

20 mJ/cin² for 1 day. MED 120 is a value to generate an erythema

response when a person whose a skin type is 6 is exposed to 120 mJ/cπ for 1 day.

Further, in Table 4, the value 33 indicates an expected MED arrival time and indicates a time that arrives from the UV index 1 by the skin type to the minimum cleansing. Meanwhile, a SPF index that is needed to protect the skin even when the skin is exposed to UV rays during that time can be expressed

into the following equation. SPF = The amount of light per minute by the UV-B index [mJ/cn]

x Going-out time [minutes] ÷ Minimum cleansing amount by the skin

type (MED) (B) SPF that is needed to protect the skin for 3 hours is set in

Table 5. Meanwhile, a safe exposure time when a sun protect agent of a set SPF is applied on the skin can be calculated by the following

equation. Safe exposure time (TMED, minutes) when a sun protect agent is applied according to an SPF index = Minimum cleansing amount by the

skin type [MED] ÷ The amount of light per minute by the UV-B index

[mJ/αrf] X SPF index (C)

Table 5

In Table 4 and 5, in order to obtain a value of SPF, an UV-B index value is calculated by allocating the amount of UV rays that arrive at the surface for 1 day to 0.6 to 9.0 mJ/cπf by comparing a measured value of an UN-B index and clinical demonstration using the meter invented by the inventor and a common UV meter. It is evident that the values of Table 4 and 5 can be modified by measuring the amount of the UV rays depending upon an actual UV-B index. 2 PFA Index (UV-A Index)

In the present invention, the intensity of UV rays is measured in the second UV sensor 21 using the sensors 205 and 205' for obtaining characteristics of a blackening response of the skin for UV rays through combination of the sensitivity characteristic of the photodiode and the UV filter and UV transparent lens 202 and 202' . Of course, this value can be converted to an UV index. From the above result, a formula for calculating a safe exposure time from the amount of UV (MPD) that is needed to generate

blackening depending on the skin type by directly examining the type

of skin response for the UV rays with respect to an adult. Safe exposure time (TMPD; min) when a sun protect agent is

applied = Minimum blackening amount by the skin type (MPD) ÷ the intensity of radiation per minute by the UV-A index [J/cnf] x PFA index (D) Table 6; Minimum blackening amount of the skin type, amount of light by the UV-A index and expected MPD arrival time (minute)

Although the UV-A index is subdivided into 15 steps in Table 6,

the present invention is not limited to it. It will be evident that the UV-A index can be divided into several steps and the MPD can be also divided, as described above. For explanation' s convenience,

only UV Index 1 and 15 has been described in the skin types 1 to 6.

Those skilled in the art will easily know a MPD arrival time for the UV indices 2 to 14 from the above description.

Furthermore, the MPD by the skin type is set based on clinical demonstration made by the inventor and the fact that is generally

known. That is, MPD 30 is a value to generate an erythema response

when a person whose a skin type is 1 is exposed to 30 mJ/cn for 1 day. MPD 5 is a value to generate an erythema response when a person whose a skin type is 6 is exposed to 5 mJ/cnf for 1 day. Further, in Table 6, the value 3000 indicates an expected MPD

arrival time and indicates a time (minute) that arrives from the UV index 1 by the skin type to the minimum blackening.

Meanwhile, a PFA index that is needed to protect the skin even when

the skin is exposed to UV rays for that time can be expressed into the following equation. PFA = The amount of light per minute by the UV-A index[J/cπf] x

Going-out time [minutes] ÷ Minimum blackening amount by the skin type (MPD) (E) Safe exposure time [minute] when a sun protect agent is applied according to an PFA index = Minimum blackening amount by the skin type [MPD] ÷ The amount of light per minute by the UV-A index [mJ/cnf]

x PFA index (F) A PFA index needed to protect the skin for 3 hours can be given

in Table 7 below.

Table 7

In Table 6 and 7, in order to obtain a value of a PFA index, a value of an UV-A index is calculated by allocating the amount of UV rays that arrive at the surface for 1 day to 0.01 to 0.21 J/cnf by comparing a measured value of an UV-A index and clinical demonstration using the meter invented by the inventor and a common UV meter. It is evident that the values of Table 6 and 7 can be modified by measuring

the amount of the UV rays depending upon an actual UV-A index. Also, the correlation between the PA index indicated in

cosmetics and the PFA index indicated in the present meter is as follows so that a user can select a suitable UV-A blocking cosmetics.

Cooperation relationship between the index operational unit of

the microcomputer 50 and the exposure time microcomputer will now be

described. Example 1) in the case where UV-B is 15.0, a time is calculated when a sun protect agent SPF 20 is applied

Example 2) in the case where UV-B is 15.0, a time is calculated when a sun protect agent SPF 30 is applied

Example 3) a time is calculated when a skin type, an UV-B index and a sun protect agent SPF are applied

Example 4) in the case of UV-A 15.0, a sun protect agent time calculated

Example 5) in the case of UV-A 15.0, a sun protect agent time calculated

3. SPF A SPF value is written on the cover of a sun cream. The lowest

value is 1 and the highest value is 50. <Test Example 1>

In the event that a user inputs 3 as the skin type, uses the sensor units 200 and 200' to measure the intensity of UV rays and

outputs an UV-B index 10, if a possible exposure time is calculated and a time when cosmetics are not applied is then outputted as 10 minutes by means of software, a sun protect index (SPF Index) that is needed to be exposed to sunlight for 3 hours (180 minutes) is

calculated and SPF 18 is outputted by software. Text Example of Exposure Time In the event that a user inputs 60 minutes in the hope that he wants to be exposed to sunlight for 1 hour, when a necessary SPF index

is calculated and SPF 6 is outputted as software, if a user inputs cosmetics SPF 30 that is being used currently, a possible exposure time is calculated and 300 minutes is outputted as software. <Test Example 2> In the event that a user inputs 4 as the skin type, uses the

sensor units 200 and 200' to measure the intensity of UV rays and

outputs UV-B index 5, if a possible exposure time is calculated and 27 minutes is outputted as a possible exposure time when cosmetics are not applied by means of software, a SPF index that is needed to be exposed to sunlight for 3 hours and SPF 7 is outputted by means of

software. Text Example of Exposure Time In the event that a user inputs 60 minutes in the hope that he

wants to be exposed to sunlight for 1 hour, when a necessary SPF Index is calculated and SPF 2 is outputted by software, if a user inputs cosmetics SPF 10 that is being used currently, a possible exposure

time is calculated and 270 minutes is outputted by software. 4. PA

A PA value is mostly indicated as + on the cover of sun cream. The lowest value is + and the highest value is +++. A time when blackening in which the skin becomes black occurs every person is decided by clinical researches by the skin type.

<Test Example 1> In the event that a user inputs the skin type 4 according to a

reference table by the skin type of Table 1, measure UV index and

outputs UV-A index 12, if a possible exposure time is calculated when

a sun protect agent is not applied and 115 minutes are outputted by software, ++ being UV A protection index (PA index) that is needed to

be exposed to sunlight for 3 hours is outputted by software. Test Example of Exposure Time In the event that a user inputs 60 minutes in the hope that he wants to be exposed to sunlight for 1 hour, if PA index that is needed when being exposed to sunlight for 60 minutes is calculated and + is outputted by software, a possible exposure time when ++ is inputted is calculated and 290 minutes are outputted by software. <Test Example 2>

In the event that a user inputs a skin type 4 and measures an

UV index to output UV-A index 15, if a possible exposure time when a sun protect agent is not applied and outputted as 71 minutes by software, ++ being UV-A protection index (PA index) that is needed to

be exposed to sunlight for 3 hours is outputted. Test Example of Exposure Time In the event that a user inputs 60 minutes in the hope that he

wants to be exposed to sunlight for 1 hour, if PA index that is needed when being exposed to sunlight for 60 minutes is calculated and + is

outputted by software, a possible exposure time when + is inputted is calculated and 80 minutes are outputted by software The display unit 60 displays a safe exposure time, a

recommended SPF or a recommended PFA index that is decided by an exposure time microcomputer of an UV meter microcomputer 50. Further,

the display unit 60 displays SKIN CARE, a skin type number, an UV-A

index, an UV-B index, SPF, an exposure time when a sun protect agent

is applied, an exposure time when a sun protect agent is not applied, a current date, warning, etc. An alarm unit(70) issues alarming sound or alarming emission before an exposure time set in the display unit 60 elapses to a meter

user. Further, a temperature sensor 80 senses a temperature in the air and displays a current temperature on the display unit 60. FIG. 8 is a flowchart illustrating the operation of the 2- channel UV meter of the GaN type. Referring to FIG. 8, if power is turned on to start measurement

(S701), the UV sensor measures UV rays (S702) and displays a safe exposure time of the skin on which a sun protect agent is not applied on the display unit (S703). The skin type keeps an existing value as a default. If only when the skin type is to be changed, the stored value is changed. If a SPF index is inputted (S704), a safe exposure time corresponding to it is displayed. If an expected exposure time

is inputted (S706),. a recommended SPF is displayed. It is to be noted that the flowchart of blackening response can

be performed in the same manner as FIG. 8.

An UN meter using the photodiode of the GaΝ type has been described in the present invention as an example. Those skilled in the art will know that the present invention is not limited to it but

can be applied to an UV meter using photodiodes of various types. Industrial Applicability As described above, according to the present invention, by fabricating a proper coating filter depending on a sensitivity

characteristic of a GaN photodiode, a relative sensitivity characteristic is obtained close to an erythema response action spectrum and a blackening response action spectrum. By combining a

sensitivity characteristic of a gallium nitride photodiode consisting of a small metal can package or a surface mounting type package and an UV filter, a sensor for obtaining characteristics of an erythema response and a blackening response of the skin for UV rays is obtained. Therefore, it is possible to obtain characteristics of erythema response or blackening response spectrum of the skin. Further, according to the present invention, an UV meter that is cheap, has high sensitivity efficiency and is portable is obtained using a gallium nitride photodiode.

While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be

appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.

Claims

What Is Claimed Is: 1. An UV meter, comprising: an UV sensor for measuring an UV-B index being an erythema response sensitivity characteristic of incident light; a microcomputer for performing an operation based on the UV-B

index measured in the UV sensor and a skin type index and SPF that are

inputted through an input unit to decide a safe exposure time; and a display unit for displaying the safe exposure time that is decided in the microcomputer.

2. An UV meter, comprising: an UV sensor for measuring an UV-B index being an erythema

response sensitivity characteristic of incident light; a microcomputer for performing an operation based on the UV-B index measured in the UV sensor and a skin type index and an exposure

time that are inputted through an input unit to decide a recommended SPF index; and a display unit for displaying the SPF index that is decided in the microcomputer.

3. An UV meter, comprising: an UV sensor for measuring an UV-B index being an erythema response sensitivity characteristic of incident light; a microcomputer for performing an operation based on the UV-B index measured in the UV sensor and a skin type index that inputted through an input unit to decide a safe exposure time of the skin on

which a sun protect agent is not applied; and a display unit for displaying the safe exposure time of the skin on which the sun protect agent is not applied, which is decided in the

microcomputer.

4. An UV meter, comprising: an UV sensor for measuring an UV-A index being an erythema response sensitivity characteristic of incident light; a microcomputer for performing an operation based on the UV-A

index measured in the UV sensor and a skin type index and a PFA index

that are inputted through an input unit to decide a safe exposure time; and a display unit for displaying the safe exposure time that is decided in the microcomputer.

5. An UV meter, comprising: an UV sensor for measuring an UV-A index being an erythema response sensitivity characteristic of incident light; a microcomputer for performing an operation based on the UV-A

index measured in the UV sensor and a skin type index and an exposure time that are inputted through an input unit to decide a recommended PFA index; and a display unit for displaying the PFA index that is decided in

the microcomputer.

6. An UV meter, comprising: an UV sensor for measuring an UN-A index being an erythema response sensitivity characteristic of incident light; a microcomputer for performing an operation based on the UV-A

index measured in the UV sensor and a skin type index that inputted through an input unit to decide a safe exposure time of the skin on

which a sun protect agent is not applied; and a display unit for displaying the safe exposure time of the skin on which the sun protect agent is not applied, which is decided in the microcomputer.

7. The UV meter as claimed in any one of claims 1 to 3, wherein the UV sensor comprises a photodiode that converts an inputted optical

signal into an electrical signal, an UV filter that is disposed in an

optical path before an incident light reaches the photodiode, and a measurement unit electrically connected to the photodiode, for

measuring the amount of the converted electrical signal to determine a corresponding UV-B index from the amount of the measured value, wherein in at least some of periods 280 nm to 320 nm wavelength, transmissivity of the UV filter is formed so that the ratio of a relative amount of a value corresponding to a product of transmissivity of the UV filter and a relative response intensity of the photodiode for respective wavelengths corresponds to the ratio of a relative amount of the relative response intensity on a blackening

response spectrum curve on the curve of the skin for respective

wavelengths.

8. The UV meter as claimed in any one of claims 4 to 6, wherein the UV sensor comprises a photodiode that converts an inputted optical

signal into an electrical signal, an UN filter that is disposed in an

optical path before an incident light reaches the photodiode, and a measurement unit electrically connected to the photodiode, for measuring the amount of the converted electrical signal to determine a

corresponding UN-B index from the amount of the measured value, wherein in at least some of periods 310 nm to 400 nm wavelength,

transmissivity of the UV filter is formed so that the ratio of a

relative amount of a value corresponding to a product of transmissivity of the UV filter and a relative response intensity of

the photodiode for respective wavelengths corresponds to the ratio of

a relative amount of the relative response intensity on a blackening response spectrum curve on the curve of the skin for respective wavelengths.

9. The UV meter as claimed in claim 2, wherein the microcomputer calculates SPF according to the following equation: SPF = The amount of light per minute by the UN-B index [mJ/cnf] X Going-out time [minutes] ÷ Minimum cleansing amount by the skin type (MED)

10. The UV meter as claimed in claim 5, wherein the microcomputer calculates the PFA index according to the following equation:

PFA = The amount of light per minute by the UN-A index[J/cnf] x

Going-out time [minutes] ÷ Minimum blackening amount by the skin type (MPD)

11. The UN meter as claimed in claim 1, wherein the safe

exposure time (minutes) when a sun protect agent is applied according to the SPF index is calculated according to the following equation:

Safe exposure time [minutes] = Minimum cleansing amount by the skin type [MED] ÷ The amount of light per minute by the UV-B index

[mJ/cnf] x SPF index

12. The UV meter as claimed in claim 1, wherein the safe exposure time (minutes) when a sun protect agent is not applied according to the SPF index is calculated according to the following

equation: Safe exposure time [minutes] = Minimum cleansing amount by the skin type [MED] ÷ The amount of light per minute by the UV-B index [mJ/cnf]

13. The UV meter as claimed in claim 4, wherein the safe exposure time (minutes) when a sun protect agent is applied according

to the PFA index is calculated by the following equation: Safe exposure time [minute] = Minimum blackening amount by the skin type [MPD] ÷ The amount of light per minute by the UV-A index

[mJ/cnf] x PFA index

14. The UV meter as claimed in claim 4, wherein the safe

exposure time (minutes) when a sun protect agent is not applied according to the PFA index is calculated according to the following equation:

Safe exposure time [minute] = Minimum blackening amount by the

skin type [MPD] ÷ The amount of light per minute by the UV-A index [J/crf]

15. The UV meter as claimed in claim 7, wherein the UV sensor calculates the amount of the electrical signal that is generated from the photodiode by means of light that passes through the UV filter instead of the UV-B index.

16. The UV meter as claimed in claim 8, wherein the UV sensor

calculates the amount of the electrical signal that is generated from

the photodiode by means of light that passes through the UV filter instead of the UV-A index.

17. The UV meter as claimed in claim 7, wherein the photodiode is a gallium nitride photodiode.

18. The UV meter as claimed in claim 8, wherein the photodiode

is a gallium nitride photodiode.