Laser device and method for operating a laser device

FIELD OF THE INVENTION

The invention relates to the field of laser devices, which comprises a laser for emitting laser light, as well as a corresponding method for operating such kind of a laser device. Such laser devices are particularly used for light shows, communication, scientific researches or laser pointers for drawing the attention of an audience to specific parts of a picture.

BACKGROUND OF THE INVENTION

From US 2002/0071287 Al a laser device in the form of a laser pointer is known which comprises two different operating lasers of different wavelength. For safety purposes the total output of the laser pointer is kept below a defined limit by means of a circuit, which allows the operation of only one operating laser at a time.

It is a disadvantage of such kind of a laser device that an injury of a human eye is still possible although the defined safety limit for the total output is met. Even red laser light of a laser pointer, which comprises a low power in comparison to a different visible wavelength, can damage a human eye.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a laser device as well as a method of operating a laser device, which provides an increased safety.

This object is achieved by a laser device comprising an operating laser for providing an operating light at an operating wavelength and a safety light source for providing a safety light mainly at a safety wavelength, wherein the safety light source is coupled such to the operating laser that the safety light is directed in the same direction like the operating laser during operation of the operating laser, wherein the safety wavelength is better absorbable by melanopsin than the operating wavelength.

According to the invention the increased safety is not provided by adjusting the power of the emitted light but by using a human reflex. It is used the insight, that the light-sensitive ganglion cells on the retina of a human eye are activated by the light

absorption of melanopsin within the ganglion cells. Since the safety light is better absorbed by melanopsin, the safety light stimulates the ganglion cells, which in turn leads to an eyelid closure reflex. Due to the eyelid closure reflex the retina of the human eye is covered by the eyelid immediately and thus protected. The safety light source is adjusted such, that the safety light is at preferably every time at the mainly same place present as the operating light. The safety light source may be coupled to the operating laser such, for instance by an electrical circuit like a connection in series, that the safety light source is automatically switched on, when the operating laser should be switched on. When the operating light meets a human eye the safety light as well meets the same human eye. The portion of the safety light may be chosen such that an eyelid closure reflex is provoked independently from the operating light. Since only a low power of the safety light at a suitable wavelength is sufficient for initiating the eyelid closure reflex, the safety light do not have a major impact on the color of the operating light. For example a laser pointer may comprise an operating laser, which provides a mainly red light, wherein a safety light source is provided, which provides at every time during the operation of the operating laser a mainly blue light, which comprises a significant lower power than the red laser light. The operating light, which provides the wanted laser light, is not adversely affected by the safety light. Further the total output power from the laser device is only slightly increased by the safety light source. Under certain circumstances it is even possible to increase the power of the operating light without increasing the risk of damaging a human eye due to the assured eyelid closure reflex. When the safety light source comprises a laser, it is possible to provide a safety light at mainly one specific safety wavelength. However, it is possible to provide the safety light by means of a common lamp like a filament lamp or gas discharge lamp. In this case the safety wavelength is understood as the wavelength, which is emitted with the highest amount in comparison to further wavelengths emitted by the same safety light source.

Preferably the safety wavelength λ _s is 400 nm < λ _s < 550 nm, particularly 420 nm < λ _s < 535 nm, preferably 435 nm < λ _s < 528 nm, more preferred 455 nm < λ _s < 518 nm and most preferred λ _s = 485 nm ± 5 nm. At mainly 485 nm the absorption of melanopsin is at its maximum, wherein the absorption at ca. 400 nm and 550 nm is mainly at 20% of its maximum. At ca. 420 nm and 535 nm the absorption is mainly at 40% of its maximum, at ca. 435 nm and 528 nm mainly 60% of its maximum and at ca. 455 nm and 518 nm at mainly 80% of its maximum. When a safety wavelength nearer to the absorption maximum of melanopsin is chosen, the power of the safety light may be chosen lower for safeguarding the eyelid closure reflex and vice versa.

Particularly at wavelengths for orange light (590 nm - 610 nm) and red light (610 nm - 700 nm) the absorption ability of melanopsin is very low and nearly zero, so that particularly at orange or red laser light the additional particularly blue (440 nm - 500 nm) safety light is advantageous for preventing an injury of a human eye by laser light. Particularly a control circuit is provided, wherein the control circuit is connected such to the operating laser and the safety light source that the operating laser is only operable at operating safety light source. Preferably the safety light source and the operating laser are connected in series with respect to an electrical power source. If a malfunction in the safety light source occurs, which prevents the emission of the safety light, the current circuit is cut preventing the emission of the operating light. Further it is safeguarded that at every time, when the operating laser emits the operating light, the safety source is switched on for emitting the safety light.

Preferably the operating light comprises a power Pi and the safety light comprises a power P _s , which is lower than the power P ₁ , wherein the ratio of P ₈ ZP ₁ is particularly 0.005 < P ₈ ZPi < 0.5, preferably 0.01 < P ₈ ZPi < 0.1 and most preferred 0.02 < P ₈ ZPi < 0.05. Since the power P ₈ of the safety light is significantly lower then the power Pi of the operating light, the intended color of the operating light is not adversely affected by the safety light. Further the energy consumption is not significantly increased by the safety light source. Particularly the safety light comprises a power P ₈ , which is 0.01 mW < P ₈ < 1.5 mW, particularly 0.02 mW < P ₈ < 1.0 mW, preferably 0.03 mW < P ₈ < 0.8 mW and most preferred 0.04 mW < P ₈ < 0.5 mW. At this power the energy dose rate is kept low enough for preventing a damage of the human eye. At this power the time until the human eye is closed due to the eyelid closure reflex is short enough for preventing a damage of the human eye. At the same time the power is high enough that the ganglion cells initiate the eyelid reflex.

In a preferred embodiment the safety light source comprises a safety laser for providing the safety light. Due to the safety laser the safety light may be provided at mainly one suitable specific safety wavelength. Further the safety light is well bundled rendering additional complicated optical elements unnecessary. Since the light generation of the operating light by means of the operation laser and the safety light by means of the safety light source are similar, the same optical elements may be used by the operating light as well as by the safety light. Further it is eased to direct the safety light in the same direction as the operating light.

In a further embodiment a collimator for focusing the safety light is provided. By means of the collimator safety light provided by a filament lamp or a gas discharge lamp can be focused like a laser beam. Further the beam of the safety light may be more focused than the operating light, so that a high amount of safety light at a particular light spot is provided, which comprises a high power density for initiating the eyelid closure reflex.

Particularly an optical unit for mixing the safety light to the operating light is provided. Due to the mixing the operating light as well as the safety light can be provided at the same place, so that at the same place one beam with two different wavelengths may arrive. The operating light and the safety light may be superimposed without adversely affecting each other. It can be safeguarded, that at every place, where the operating light arrives, the safety light arrives as well.

Preferably the safety light source is adapted such that the safety light provides a safety light spot, which is smaller than an operating light spot provided by the operating light, wherein particularly the safety light spot lies mainly completely within the operating light spot. By means of a low power of the safety light a high power density may be provided within the safety light spot. By means of the safety light spot the eyelid closure reflex may be provoked. Further at a moment, when a damaging amount of the operating light spot meets a human eye, the safety light spot as well meets the human eye automatically provoking the eyelid closure reflex. In a preferred embodiment the operating wavelength λ ₀ is 550 nm < λ ₀ < 700 nm, particularly 600 nm < λ ₀ < 690 nm and preferably 650 nm < λ ₀ < 680 nm. By means of these wavelengths the color of the operating light is mainly orange or red. Such colors are usually used for laser pointers. Due to the comparable low wavelength in the visible light spectrum the power is comparable low, which in turn reduces the risk of damaging a human eye. Due to the additional safety light the eye closure reflex is still maintained.

The invention further relates to a laser pointer for handheld operations comprising a laser device, which may be designed as previously described. The laser pointer particularly comprises a battery unit for applying energy to the operating laser and the safety light source. Preferably the battery applies energy to the operating laser and the safety light source only at the same time. An increased safety is not provided by adjusting the power of the emitted light but by using the human eyelid closure reflex by stimulating the melanopsin of the light-sensitive ganglion cells on the retina of the human eye. Thus, the laser pointer provides an increased safety.

The invention further relates to a method for operating a laser device, which particularly may be designed as previously described, wherein an operating light at an operating wavelength and a safety light mainly at a safety wavelength are provided at the same time and mainly the same place, wherein the safety wavelength is better absorbable by melanopsin than the operating wavelength. An increased safety is not provided by adjusting the power of the emitted light but by using the human eyelid closure reflex by stimulating the melanopsin of the light-sensitive ganglion cells on the retina of the human eye. Thus, the method provides an increased safety. The method can be further developed as illustrated with respect to the above described laser device. Particularly the powers and/or the wavelengths of the operating light and the safety light may be adjusted as illustrated with respect to the above described laser device.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. In the drawings: FIG. 1 is a schematic absorption curve for melanopsin.

DETAILED DESCRIPTION OF EMBODIMENTS The absorption curve 10 for melanopsin as illustrated in FIG .1 is a function of the relative absorption 12 in dependence of the wavelength 14 in nm. At a wavelength corresponding to yellow (570 nm - 590 nm), orange (590 nm - 610 nm) or red light (610 nm - 700 nm) the absorption ability of melanopsin is below 0.2 (yellow) or even nearly 0 (orange, red). This means the absorption ability of melanopsin is below 20% of the maximum absorption ability at ca. 485 nm. When laser light with a wavelength of 570 nm or higher meets a human eye, only very few energy is absorbed by the melanopsin in the ganglion cells on a human retina. Due to the low absorption it is likely that an eyelid closure reflex is not initiated, so that the laser light may damage the human eye.

In contrast to yellow, orange or red light at a wavelength corresponding to violet (400 nm - 440 nm) blue (440 nm - 500 nm) and green light (500 nm - 570 nm) the absorption for melanopsin is significantly higher. Thus, it is sufficient to provide by means of a safety light source in addition to an operating light provided by an operating laser a safety light, which is better absorbable by melanopsin and which comprises only a low power, for provoking the eyelid closure reflex. The safety light comprises particularly a wavelength near

to ca. 485 nm, which is near to an absorption maximum 16 of melanopsin. The combination of the operating laser with the safety light source, wherein the operating light and the safety light are directed in the same direction and particularly superimposed, leads to a laser device, which provides an increased safety. For example a laser pointer providing mainly red laser light may provide in addition a low amount of blue light at the same time for assuring the eyelid closure reflex in the case that the red laser light meets a human eye.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. For example, it is possible to operate the invention in an embodiment wherein a safety light source for provoking the eyelid closure reflex is used in a laser device used for light shows, communication, scientific researches or other applications, where a risk for blinding a human with laser light is present. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.