WO2004008114A1

WO2004008114A1 - Method and device for the differentiated, target structure-dependent illumination and viewing of surfaces and their substructures

Info

Publication number: WO2004008114A1
Application number: PCT/EP2003/007392
Authority: WO
Inventors: Jürgen Fraatz
Original assignee: Medical Laser Rent E.K.
Priority date: 2002-07-10
Filing date: 2003-07-09
Publication date: 2004-01-22
Also published as: AU2003250008A1; DE10230955A1; DE10230955B4

Abstract

The invention relates to a method for the differentiated, target structure-dependent illumination and viewing of a surface. According to the inventive method, the surface is illuminated with elliptically polarized light, the light reflected by the surface being blocked or allowed to pass by at least one observation system containing an analyzer, in order to view the light reflected by the surface or scattered on a substructure of said surface as a highlighted feature. The invention also relates to a device for carrying out the inventive method.

Description

Method and device for differentiated, target structure-dependent lighting and viewing of surfaces and their substructures

The invention relates to a method for differentiated, target structure-dependent lighting and viewing of a surface, in which a surface is illuminated by means of elliptically polarized light. The invention further relates to a device for differentiated, target structure-dependent lighting and viewing of a surface with at least one lighting system, comprising a light source and a polarizer unit, and with at least one viewing system, comprising analyzer elements.

It is generally known that depending on the observation target of e.g. damp and / or high-gloss surfaces, the reflected light significantly impairs the view.

For example, the observation and recognition of structures in a material on the basis of light scattering and / or reflection below its surface is made more difficult by light which is reflected directly from the surface of this material. In the field of dermatology e.g. the detection of subepidermal structures, i.e. Structures below the surface of the skin are complicated by the light reflected from the surface of the skin.

To examine a superficial relief structure, for example the surface of the skin, the preferred information carrier in turn is only the reflected light, while the light scattered and / or reflected from deeper layers impairs the view.

Furthermore, in order to assess the result or to control many medical or technical interventions and work, a lamp must also be able to produce lighting conditions that are as similar as possible to daylight, so that the natural appearance of the surface including the reflected and scattered portion can be viewed and the result of a work tailored to natural lighting conditions can be.

In addition, it seems important to be able to set the size of the lighting area to an optimum, e.g. To prevent reflections on instruments that surround the viewing area.

WO 00/11451 A1 describes a method and an arrangement consisting of an illuminating device and a viewing unit, which perform the tasks of selective relief structure observation and the suppression of surface reflection through the use of a rotatable linear polarization filter behind a light source in connection with a stationary linear polarization filter as an analyzer within the observation unit. Here, both devices are to be used as a coherent system with holder and fastening devices during an examination.

It is disadvantageous that this system does not provide for the light source also to be used as conventional lighting with a daylight-like spectrum and unpolarized light. Furthermore, in the case of the possibility of separating light source and viewing unit, which is also described, it is very disadvantageous that for one or more viewers with different positions and locations, different direction-dependent structural information is emphasized relative to the plane of incidence of the light.

Furthermore, DE 199 10 079 C1 discloses a method and a device for preventing reflections using polarized light describes working field lighting with a linearly polarizing filter, the light coming from the surface to be viewed being analyzed with another freely rotatable, linear polarizing filter.

This arrangement has the disadvantage that, according to Fresnell's formulas, both the proportion of the surface, e.g. of a skin surface, as well as the proportion of light entering the viewing medium depend strongly on the angle of incidence and the direction of polarization relative to the plane of incidence, and thus the image quality as a function of the position of the light source relative to the viewing surface, e.g. the patient.

This is particularly disadvantageous if several viewers look at the same surface from different directions despite an individually adjusted analyzer position of the viewing unit or if an individual viewer changes his position relative to the illumination source and / or viewing area. Furthermore, the rotatable filter of the viewing device, which is only permeable to linearly polarized light, must be readjusted after the viewer changes position.

The above methods are all based on the use of linearly polarized light for surface illumination and the preservation of the polarization properties after reflection and successive depolarization after penetration into the material to be considered. Under crossed polarizers of the illumination and viewing unit, one obtains an optimal view for sub-surface structural elements, while the relief structure is highlighted when the filter is placed in parallel. The disadvantages of the arrangements described are inherent to the system due to the use of linearly polarized light for illuminating the surface and the associated direction-dependent effects. It is known to apply elliptically polarizing foils directly to the surfaces to be viewed in order to increase contrast and reduce reflections on computer screens, display surfaces, etc.

Some theoretical foundations and the possible use of a circularly polarizing filter to improve visibility in the field of biomicroscopy are described by E. Peli, Arch Ophtalmol 1985; 103: 670-2.

WO 94/09463 discloses a method and devices consisting of an illumination apparatus and a viewing unit in order to find or determine dielectric or depolarizing substances on metallic surfaces. Specifically, the application as an ice warner on aircraft wings is described. The device and method of this document are based on the different reflection and depolarization behavior of different materials, so that here the effect of a depolarizing effect with low reflection of a first dielectric layer compared to a polarization-maintaining effect with simultaneous strong reflection of a second metallic layer is used for coating detection. The proportion of light reflected by the dielectric covering surface is not taken into account here. The devices and methods mentioned are in principle not intended for the relief and / or substructure characterization of dielectrically uniform surface areas.

The object of the invention is to design a method for illuminating and viewing surfaces and an apparatus for carrying out the method from essentially known optical components in such a way that the method and the apparatus are optimized both as a conventional lighting system and as a lighting and viewing system Recognition of a relief structure of the surface or sub-surface areas thereof is to be used and the same structural information with the same image quality is to be displayed for the at least one observer from different positions relative to the light source and / or viewing surface with the illumination surface possibly being varied. With regard to the method for illuminating, the object is achieved according to the invention in that at least one light source in optional connection with a polarizer unit is used within at least one lighting system in such a way that when the polarizer unit (s) are used, elliptically or circularly polarized light with different directions of rotation or unpolarized Light can be produced by omitting the same for surface lighting. It is thus possible to continuously adjust the polarization from circularly left-turning via elliptical polarization to circularly rotating to the right.

Surface illumination with elliptically or circularly polarized light in conjunction with appropriately adapted viewing systems avoids the disadvantages of linear polarization known in the prior art due to the directional dependence. Elliptically polarized light retains its polarization property after reflection. Here, the direction of rotation that can be observed largely independently of the direction and not, as in the prior art, the linear direction of polarization of the light can be used to suppress or emphasize the light component reflected from the surface.

With the viewing system comprising at least one analyzer, the light reflected from the surface is partially or completely blocked or transmitted in order to highlight either the light reflected from the surface or the light scattered and / or reflected on a substructure of this surface. The size of the diffraction field is preferably set using an iris diaphragm.

The analyzer elements for elliptically or circularly polarized light can be used according to the invention within the viewing system in such a way that one or more viewers can individually set whether one of the viewers can be set either by adjusting the polarization characteristic of the light illuminating the surface of a light source or by changing the transmission characteristic of the viewing system Surface structure such as a relief or sub-surface structures can be considered highlighted. The relief or The substructure portion of the image to be viewed can be infinitely adjusted within wide limits.

Here is in the frame. of the present invention, the light which is scattered and / or reflected on a sub-surface structure, a so-called sub-structure, means the light which is transmitted through the surface of a material - e.g. of a dielectrically uniform material - penetrates into the material and is then scattered out of it or reflected back.

This backscattering or reflection from deeper layers takes place partly in the direction of the light reflected on the surface and can be discriminated against by the invention.

The backscattering or reflection in the material takes place on irregularities, inclusions, etc., i.e. generally on structural elements below the illuminated surface, the substructures mentioned.

A particular advantage of the invention compared to all the methods known in the prior art is therefore essentially independently of the viewing direction and / or lighting direction of being able to selectively highlight image information from the optionally structured surface of an illuminated material or the optionally structured depth of the same material. The image information which is normally superimposed undisturbed on account of the principle of superposition can be distinguished from one another on the surface and sub-surface due to different polarization properties due to different polarization properties. The relief or The substructure portion of the image to be viewed can be infinitely adjusted within wide limits.

In this respect, the method and the device according to the invention can only improve the recognition of the relief or substructure, for example of organic or inorganic material surfaces, if they have a certain transparency for the light wavelength used, because only in this way it is ensured that the light gets under the surface of the material and is scattered back and / or reflected back out of the material, ie there are radiation components that can be separated from one another. The penetration depth can vary from material to material. Likewise, the penetration depth can depend on and / or be adjusted by the light wavelength used, so that by using different wavelengths when viewing one and the same material, image information can be obtained from regions of different depths.

The solution according to the invention can be used in particular in the context of medical and aesthetic-cosmetic interventions and examinations e.g. on the skin as well as on any organic and inorganic substances.

The method according to the invention has the following advantages:

The lighting system and the viewing system can be designed in such a way that comparable contrasts and image qualities for the at least one viewer are also achieved and are maintained if the lighting system and viewing system are used as separate units.

Larger areas can be illuminated more brightly because the lighting system can be dimensioned more flexibly as a unit that is not to be carried on the body and in a fixed connection with the viewing system and can therefore be designed to be significantly more powerful.

To illuminate large areas, several lighting systems that generate elliptically polarized light with the same direction of rotation can be used flexibly and flexibly without the polarization filter settings of the light sources used having to be re-coordinated for each lighting and viewing situation.

Very light and conveniently portable viewing systems are available to the observer. The lighting system can be designed in such a way that comparable contrasts and image qualities, ie emphasizing relief or substructure, are also retained for the viewer when the light source and / or viewing system is moved or rotated relative to the surface or is illuminated from above and the viewer is viewed from look in different directions on a surface, eg a surface to be treated.

This system is therefore designed in such a way that when using a common lighting system for several viewers with the same viewing systems, comparable viewing conditions are available. By changing the direction of rotation of the incident light, the viewing mode changes equally for all observers.

It is also possible to use observation systems with variable analyzers, which leave it up to the observer to decide whether the light reflected from the surface is transmitted or blocked. Regardless of the set direction of rotation of the incident light, it is possible for every observer to choose the viewing mode that suits his own needs, without influencing the view of other observers.

In addition, there is an advantage that the apparatus according to the invention can be used with unpolarized light as a conventional light source if the polarizer unit is removed. By using an iris diaphragm in front of an imaging lens, the size of the illumination field can be adjusted as required.

In connection with the method according to the invention and its advantages mentioned, the associated device for carrying out the method is characterized in that elliptically polarized light from elliptical (e.g. circular) right to elliptical (e.g. circular) can be produced in a continuously rotating manner as required and the changeover by simply rotating a linear polarizer and / or an optical delay element of the lighting system. Thus, by changing the Polarization characteristic of the incident light by means of a viewing system that is reflected from a surface or the light scattered on its substructure is emphasized regardless of direction. The relief or substructure portion of the image to be viewed can be infinitely adjusted within wide limits.

A solution according to the invention is described on the basis of an exemplary embodiment and the associated drawings. Here show:

Figure 1: the lighting system

Figure 2; the viewing system.

Figure 1 shows an illumination system 1 for skin examination, which e.g. can be arranged as a ceiling, wall, table construction or on a tripod as a hand or head lamp etc. In the direction of the person to be examined, the elements provided for lighting are arranged as follows:

The halogen lamp 1.1 to be selected depending on the application is preferably followed by a UV filter 1.2 and an IR filter 1.3. The size of the illumination field can be set with an iris diaphragm 1.4. The illumination field is preferably generated using a convex lens system, the objective 1.5. A linearly polarizing filter 1.6 is located behind the lens 1.5. This is followed by a λ / 4 delay element 1.7. The linearly polarizing filter 1.6 and the delay element 1.7 can be rotated relative to one another in such a way that elliptically polarized light can be produced with right-hand and left-hand aisle as required.

The lighting system 1 is designed in such a way that the filter 1.6 and the delay element 1.7 can be removed as a polarizer unit 1.8 and the lighting system 1 can thus also be used as a conventional light source.

The viewing system 2 shown in FIG. 2 consists of a headband magnifier 2.1 and a pivotable analyzer 2.2. The analyzer 2.2 consists of a λ / 4 retardation film facing the surface under consideration and a linear pole film attached at an angle of 45 ° to the preferred direction of the optical retardation element. If elliptically polarized light is generated with the illumination system 1, which is blocked after reflection (reversing its direction of rotation) by the analyzer 2.2 of the viewing system 2, an optimal image of the structure lying under the reflecting surface of the skin, for example the course of the blood vessels, is obtained. If the illuminating system 1 generates elliptically polarized light which is transmitted through the analyzer 2.2 of the viewing system 2 after reflection (reversing its direction of rotation), an optimal image of the superficial relief structure, for example the skin folds, is obtained. If the illumination system 1 generates unpolarized light after removing the polarizer unit 1.8, a largely natural appearance of the surface is to be considered. When using the headband magnifier 2.1, the analyzer 2.2 can be folded back for this operating mode. The illumination field sizes can be set in each of the above-mentioned operating modes using the iris diaphragm 1.4.

Claims

claims

1. A method for differentiated, target structure-dependent lighting and viewing of a surface, in which the surface is illuminated by means of elliptically polarized light, characterized in that with a viewing system containing at least one analyzer, the light reflected from the surface is blocked or transmitted in order to either the the surface reflected or the light scattered on a substructure of this surface to be emphasized.

2. The method according to claim 1, characterized in that within the viewing system, an optical delay element and a linearly polarizing filter are adjusted separately and rotatable against each other and the transmission characteristic for elliptically polarized light is set by the viewer himself.

3. The method according to any one of the preceding claims, characterized in that the passage characteristic of the viewing system is set by using differently dimensioned optical delay elements.

4. The method according to any one of the preceding claims, characterized in that within the lighting system, a linearly polarizing filter and an optical delay element are adjusted separately and rotatable relative to one another in order to be able to produce elliptically polarizing light with a right-hand or left-hand direction of rotation.

5. The method according to any one of the preceding claims, characterized in that the polarization characteristic of the light emitted by the lighting system is set by means of differently dimensioned optical delay elements.

6. The method according to any one of the preceding claims, characterized in that a camera with analyzer equipment is used as a viewing and / or image documentation system.

7. The method according to any one of the preceding claims, characterized in that the use of different light sources and / or filter elements improves visibility in different wavelength ranges.

8. The method according to any one of the preceding claims, characterized in that a freely movable or in connection with the lighting system viewing system is positioned in front of the surface to be observed.

9. The method according to any one of the preceding claims, characterized in that a surface is illuminated with at least one lighting system and viewed independently of the direction with a plurality of separately adjustable viewing systems.

10. The method according to any one of the preceding claims, characterized in that a scattering and / or reflection of the incident light on different, in particular adjustable deep substructures in the illuminated material takes place by a wavelength change in the lighting system.

11. Device for differentiated, target structure-dependent lighting and viewing of a surface for carrying out the method according to one of the preceding claims, with at least one lighting system (1) comprising a light source and a polarizer unit and with at least one viewing system (2) comprising analyzer elements, characterized in that that by illuminating with elliptically polarized light and changing the transmission direction of a viewing system, the light reflected from the surface or the light scattered on its substructures can be viewed in a direction-independent manner.

12. The apparatus according to claim 11, characterized in that

Lighting and viewing system form separate units.

13. The apparatus according to claim 12, characterized in that a viewing system (2) is designed as a conventional headband magnifying glass (2.1) or as a magnifying glass analyzer (2.2) for viewing surfaces illuminated with elliptically polarized light.

14. Use of a method or a device according to one of the preceding claims for examining the skin and its subepidermal structures.