DE19936958A1 - Light source for endoscopy has LEDs arranged on concave surface of calotte shell, with separate focussing lenses for each LED - Google Patents

Abstract

The light source has multiple LEDs (7 to 9) arranged on a surface (10), the light being focussed on an input portion (3) of a light guide (2). Each LED is separately provided with a focussing device (5). The surface (10) is preferably a calotte shell surface. The focussing devices are arranged on the concave side of the shell, aligned with the input of the light guide.

Description

The invention relates to a light source, in particular for use in the Endoscopy is used and provided with several LEDs arranged in one area is whose light is focused on the coupling point of an optical fiber.

Such a light source is in the utility model DE 298 12 048 U1 be wrote. For focusing the LEDs arranged in a flat surface, the known A common lens is used for the light source. Since about 150 to 200 LEDs are needed to make one light source with one for the Endosko To build up sufficient light output, such an arrangement is almost impossible to realize because the converging lens must have a diameter, which is larger than the carrier area required by the arrangement of the LEDs.

The focus at the coupling point of the light guide should not exceed approx. 2 mm stride. Since the converging lens used in the known light source Luminous flux under the above-mentioned conditions only has a high loss Coupled into the light guide, to make it stand out through the arrangement to compensate for the loss called for, more LEDs are required than the one to be achieved Light output is actually only needed. However, more LEDs mean again a larger converging lens, and this has an even worse coupling of the Light in the light guide result, so that the known light source here to the The limits of what is possible.

In general, LEDs have a spherical shape without additional focusing Beam characteristics with a beam angle of approx. 100 ° to 140 °. To the to realize light source shown in the utility model mentioned however, LEDs with preferably parallel beam paths are required to ensure the loss should be kept low when coupling with the converging lens. Through the he The parallel beam path would therefore be required in addition to the aforementioned collection lens requires additional focusing units.  

DE 197 48 446 A1 describes a device for controlling a large number known from light emitting diodes, each with one or more current sources the same brightness can be set for one or more LEDs. there the device has a storage device in which the for controlling the LEDs required control parameters can be stored, and an on Control device controls the LEDs based on the stored control parameters. Thus, this known device is used to Match the brightness of the individual LEDs. The device he therefore possible by individually setting the current through each LED according to the parameters stored in the allocated memory, the Difference in brightness or the spread of the brightness of the individual LEDs compensate.

It is an object of the invention to provide a light source that is particularly suitable for use suitable for endoscopy, with several LEDs arranged in one area, whose light is focused on the coupling point of a light guide, that the luminous efficacy of the LEDs is optimized, the manufacturing costs and the Ge importance of the light source are low and high reliability of the light source is guaranteed. In addition, both the luminous flux and the Lichtver distribution of the light source can be specifically controlled or regulated.

Starting from a generic light source of the type mentioned this object is achieved in such a way that each LED has a focusing device assigned. The focusing devices bundle the light from her ordered LED on a focus point, which is at the coupling point of the light is located at the proximal end. These are expediently LEDs arranged and fastened in shots of a spherical cap, and the focus Siereinrichtung are on the concave side of the spherical cap, the Axes of the LEDs and the focusing devices on the specified Fo kuspunkt are aligned, which is also on the axis of the spherical cap.

To inexpensive and simple assembly of the light source according to the invention To enable, the spherical cap carrying the LEDs consists of two or more interconnected and adjoining shell segments. With this measure can both the electrical connection of the LEDs with each other  manufactured as well as the spatially correct alignment of each LED can be achieved. The shell segments thus form a carrier and at the same time provide the elec electrical connection between the LEDs mounted on the shell segments. The division of the spherical cap into shell segments, in particular into two halves form, brings the advantage that the carrier is automatically equipped with the LEDs can be and thus enable economical production.

The shape of the half-shells also influences the focus. If the half peel z. B. are made to fit each other exactly by injection molding there are, with regard to the manufacturing tolerance of the half shells in relation to the Focusing no problems. The tolerances for the assembly and that then glue the LEDs and the focusing lenses on the concave side of the half shells are no longer a problem since the LEDs and the focusing device assigned to each LED is not assembled as a unit. Because each LED has a spherical radiation pattern and the associated focus unit focuses the light on the focus point, minor effects Tolerances when mounting the LEDs no longer focus on, because the Focusing unit fixed directly on the concave inside of the half shells, e.g. B. is glued, and the shell segments have a low manufacturing tolerance point. This eliminates the need to adjust or align the individual LEDs rational production of the light source allowed.

After equipping the segments with the LEDs, the focus will be on units used. These are advantageously in suitable recesses glued against the segments. After equipping with the focusing device The segments are connected to each other. This can be done by gluing or by mechanically locking the half-shells. Contacting the Both segments or half shells can be attached to the half shells orderly spring contacts. By designing the half shells as three-dimensional circuit boards can also be used to control the LEDs require electronic components, i. H. your control and dining equipment with the half shells. Of course you can the spherical cap serving as the carrier of the LEDs and the focusing devices also composed of more than two shell segments.  

In one embodiment, all LEDs emit white light. It is also possible to provide white LEDs and LEDs that emit monochromatic light send.

Furthermore, each LED can be assigned a separate feed device, so that the brightness of each LED can be controlled or regulated separately. Furthermore, the total unit of the LEDs can be divided into individual blocks or groups, in which case the of each group emitted luminous flux can be controlled or regulated separately and the lot Number of dining facilities from a common control or regulation unit can be controlled.

The invention is illustrated below with the aid of one in the drawing Described embodiment.

Fig. 1 shows a basic arrangement schematically shows a multi arranged on a spherical segment LEDs light source according to the invention,

Fig. 2 shows in a schematic sectional view of the fixing of the individual LEDs and their focusing in a spherical cap forming a shell,

Fig. 3 shows a plan view of the concave spherical cap surface of a spherical cap composed of two half-shells of a light source according to the invention, and

Fig. 4 finally shows in the form of a block diagram a plurality of LEDs, the focusing elements assigned to them, the separate feed device for each LED for variable adjustment of the luminous flux of each LED and the control unit that is common to all feed devices.

Fig. 1 schematically shows a basic arrangement of a light source according to the invention is, with only three LEDs 7, 8 and 9 are fixed with the respectively associated focusing means 5 at an arc segment of a forming support 10. Each of the LEDs 7 , 8 , 9 located on the carrier has a focus in connection with the focusing device 5 placed in front of it, or at least predominantly supplies parallel light with a negligible divergent portion, and the foci meet at a common focus point 3 . The coupling point of the light guide 2 is located at this focus point 3 . It proves to be advantageous to choose a spherical cap as the carrier 10 , since in this case all the LEDs 7 , 8 , 9 or the focusing devices 5 assigned to them have the same distance from the coupling point 3 , so that the same LEDs and the same for the entire light source Focusing devices can be used.

Starting from a conventional light source with low output, z. B. an arc lamp with 50 W power consumption and an efficiency of about 20%, it can be said that 10 W are required as equivalent light power. A typical white LED with an operating current of 20 mA and a typical forward voltage of approx. 3.6 V generates a light output of 0.0576 W, taking into account an efficiency of 80%. In order to achieve the same light output as with such a conventional arc lamp , about 173 LEDs are required for purely arithmetical purposes.

Thus, the Fig. 1, the three LEDs 7, 8, 9, only a basic arrangement. But be to construction of a practical light source under Underlying the above consideration interpretation least 150 LEDs needed. With regard to the homogeneity of the illumination z. B. an operating field via a light guide running through an endoscope, an arrangement should be aimed at in which the individual LEDs are placed as close as possible to one another.

, An embodiment of a light source according to the invention is shown in FIGS. 2 and 3, starting from the state shown in Fig. 1 Principle, shown which meets the above requirements. In this embodiment, special value was placed on a practical and inexpensive industrial manufacturability of the light source.

In the embodiment shown in FIG. 1, the question arises how the approximately 150 LEDs can be mounted in a spherical cap in such a way that the foci of each individual LED formed by the focusing devices are at a single point, in this case at point 3 meet at the proximal end of the light guide cable 2 . This would mean aligning and fixing each LED or its focusing device separately. In practice, this cannot be achieved with reasonable effort. The problem of how the individual LEDs can be electrically connected must also be solved. There is also the question of how the approx. 150 LEDs in the spherical cap can be installed using an automated system.

Referring to FIG. 3, the spherical segment of two segments in the form of half-shells 12, 13. The half-shells 12 , 13 are designed as three-dimensional printed circuit boards and thus serve on the one hand as carriers for the LEDs 11 mounted on the inside of the half-shells 12 , 13 and their associated focusing devices 15 , and on the other hand they provide the electrical connections between the individual LEDs 11 and . 14 according to Fig. 2 in the form of conductor tracks forth. Each half-shell 12 , 13 is thus at the same time carrier and electrical connection element. The division of the spherical cap into several shell segments, preferably into two half-shells, has the advantage that the half-shells can be automatically and inexpensively fitted with the LEDs, and this enables economical production of the light source.

The shape of the half-shells 12 , 13 is also responsible for the focusing. Since the half-shells can be manufactured to size by injection molding, there are no problems with regard to the manufacturing tolerance of the half-shells with regard to the mounting of the focusing devices. Only the tolerance when assembling and then gluing the LEDs on the inside of the half-shells must be taken into account with regard to the accuracy of the focusing. In the embodiment shown in FIG. 2, this problem was solved in that each LED 14 and the focusing device 15 associated with each LED no longer form a unit as in FIG. 1.

Each LED 14 has a spherical radiation pattern. The focusing devices 15 focus the light emitted by each LED onto the focal point 3 . Small tolerances in the assembly of the LED no longer affect the focusing, since the focusing devices 15 are fixed directly in the half-shells 12 , 13 and the half-shells have a low manufacturing tolerance.

Thus, an adjustment or alignment of the LEDs on the intended The focus point is eliminated and the light source according to the invention is therefore efficient automatically populated.

After equipping the half-shells 12 , 13 with the LEDs 11 and 14 , lenses are installed as focusing devices 15 . These are advantageously glued in. After equipping the half-shells with the focusing devices 15 , the two half-shells are connected to one another along the dividing line T. This can be done by gluing or mechanically locking the two half-shells, at the same time the contacting of the two half-shells is carried out by spring contacts, not shown, which are provided along the dividing line T.

By designing the half-shells 12 and 13 as three-dimensional circuit boards, it is additionally possible to accommodate the electronic components 16 required for controlling the LEDs, as will be explained below with reference to FIG. 4, on the half-shells.

With the embodiment of the light source shown in FIGS. 2 and 3, the requirements with regard to low power loss, optimized focusing and cost-effective and automated production can be achieved. Due to the low power loss of the entire light source, each LED can be assigned a small, inexpensive supply device or a power supply unit, since no ignition voltage or the like is required. Due to the low loss performance and the associated low heat development, active heat dissipation, such as, for. B. by a fan.

Since the lifespan of LEDs is approximately 100,000 hours, you do not have to use one soon replacement of the light source expected after initial start-up become. The maintenance and maintenance costs are therefore minimal. A This eliminates the need to replace the lamp on site. The structure an inexpensive reliable light and therefore portable light source is made possible. The reliability of the light source is extremely high because Even if one LED fails, this is still possible due to the large number of functions capable LEDs does not matter.  

The embodiment shown in FIG. 4 as a block diagram of a light source according to the invention not only allows the total emitted light current, but also to adjust the light distribution.

Due to the nature of the object to be examined, e.g. B. the Surface of a hollow organ to be examined endoscopically conventional light sources that only control or regulate the ins total luminous flux emitted allow for inhomogeneous illuminations come, d. that is, the mean of the brightness across the entire image though corresponds to the desired value, but within certain parts of the image comes to overexposure. Depending on the type of brightness control, these can Glare causes the brightness to be reduced and therefore others Parts of the picture are not sufficiently illuminated, which is the case with photographic or video recordings of the organ under consideration leads to poor images.

The solution to this problem shown in FIG. 4 is achieved in that each light-generating element, ie each LED 11 ₁ , 11 ₂ , 11 ₃ , 11 ₄ . , ., via the focusing device 15 ₁ , 15 ₂ , 15 ₃ , 15 ₄ . , ., is responsible for the illumination of a certain image area, via a separate feed device for each LED or a power supply unit 17 ₁ , 17 ₂ , 17 ₃ , 17 ₄ . , ., is supplied with energy, ie each LED can be operated with an individually adjustable brightness. The consequence of this is that the brightness of the image area assigned to the respective LED can be influenced separately. For example, in the example shown in FIG. 4, the LEDs 11 ₁ and 11 ₄ in connection with the focusing devices 15 ₁ and 15 ₄ assigned to them for edge illumination and the LEDs 11 ₂ and 11 ₃ in connection with the focusing devices 15 ₂ and 15 ₃ for center-weighted illumination of the endoscopic viewed and z. B. responsible with a video camera organ area. By increasing the number of LEDs and the focusing devices, the number of image areas that can be influenced by the different brightness can be increased and a finer adjustment of the light distribution can be achieved.

The LEDs 11 ₁ , 11 ₂ , 11 ₃ , 11 ₄ . , , assigned variable feeding devices 17 ₁ , 17 ₂ , 17 ₃ , 17 ₄ . , , are controlled by a control unit 18 common to all the feeding devices. The actuators 19 , 20 connected to the inputs of the control or regulating unit 18 allow the desired variable image brightness and illumination or light distribution to be set by entering the control / regulating unit 18 setpoints from which the control / regulating unit 18 provides the corresponding control voltages the feed devices 17 assigned to the LEDs 11 are calculated.

Finally, this variable control voltage applied to the feed devices 17 on the input side is decisive for the luminous flux emitted by the respective LED 11 . Specifically, a change in the brightness means the simultaneous increase or decrease in the luminous flux of the entirety of the LEDs, and a change in the light distribution means a different increase or decrease in the luminous flux of individual or grouped LEDs 11 . The embodiment shown in FIG. 4 thus allows control of both the luminous flux and the light distribution.

It should also be mentioned that a light sensor that detects the brightness or the total luminous flux of the light source shown in FIG. 4 can be coupled to the observation optics of an endoscope. Likewise, a plurality of light sensors distributed over a wide area can be provided, which detect the light distribution and can enter a corresponding actual value signal from the control or regulating unit 18 .

The light source according to the invention not only has to emit white light LEDs, but can also use a combination of white LEDs with monochromatic Have light emitting LEDs. This can be done from the light source adapt the emitted light spectrally to certain applications. Can also all LEDs, the focusing devices assigned to them and the associated dining facilities can be divided into groups or blocks, whereby the number of LEDs of each block can be different. Each includes Group at least one LED. By separately controlling the LEDs of each group with the help of the feed devices assigned to the LEDs, each Group can be controlled separately.

In summary, with the features described above, a particular one Realize suitable light source for use in endoscopy their small size, light weight, low performance recording and its high operational reliability also for mobile use  is suitable and also powered by an accumulator or a battery can be.

Claims (9)

1. Light source, in particular for use in endoscopy, with a plurality of LEDs ( 7-9 ; 11 ; 14 ) arranged in a surface ( 10 ; 12 ; 13 ), the light of which is focused on the coupling point ( 3 ) of a light guide ( 2 ) , characterized in that a separate focusing device ( 5 ; 15 ) is assigned to each LED ( 7-9 ; 11 ; 14 ). 2. Light source according to claim 1, characterized in that the surface is formed by a spherical cap surface and the focusing devices ( 5 ; 15 ) sit on the concave side of a spherical cap ( 10 ) and are aligned with the coupling point ( 3 ) of the light guide ( 2 ) . 3. Light source according to claim 1 or 2, characterized in that the spherical cap ( 10 ) consists of at least two interconnected segments ( 12 , 13 ). 4. Light source according to claim 3, characterized in that the segments of the spherical cap ( 12 , 13 ) are designed as three-dimensional circuit boards. 5. Light source according to one of claims 1 to 4, characterized in that all LEDs emit white light. 6. Light source according to one of claims 1 to 4, characterized in that white light emitting LEDs and monochromatic light emitting LEDs are provided. 7. Light source according to one of the preceding claims, characterized records that the brightness of each LED can be changed separately and that each LED a separate dining facility is assigned. 8. Light source according to one of claims 1 to 6, characterized in that the LEDs are divided into individual groups and that the LEDs of each group are separately assigned a feed device ( 17 ). 9. Light source according to one of claims 7 and 8, characterized in that the feeding devices from a common control or regulating unit can be controlled.