TECHNICAL FIELD

The present disclosure relates to flash housing and a method for photographic purposes.

BACKGROUND ART

In order to be able to take photographs of a certain quality a flash device is often used to provide light or to improve the light in the photograph. Normally the cross section of the beam lobe of the flash light is supposed to cover the whole photograph which is to be taken.

The spreading angle of the beam lobe of the flash light emitted from a flash device may according to some examples be varied in order to make the flash device adjustable to the photograph which is to be taken. In a relatively small flash device, such as an external flash device connectable to a camera, the flash tube and the reflector are movable in an axial direction within the flash housing. The position of the flash tube and the reflector in the flash housing will affect the spreading angle of the beam lobe of flash light emitted from the flash device.

SUMMARY In conventional flash devices, since the cross section of the beam lobe of the flash light is supposed to cover the whole photograph, it is not very important to create a beam lobe of flash light with an even border of the beam lobe. Hence, the borders of the beam lobe of flash light emitted from conventional flash devices often are uneven with large variations in light intensity and shapes. In addition, since photographs are normally quadratic, the shape of the cross section of the flash light beam lobe is preferably quadratic. However, in order to create photographs of a high quality, where the photographer is able to enhance a photograph by means of a flash light, it is important to be able to generate a flash light with a beam lobe of a desired shape and quality.

It is an object of the invention to create a beam lobe of flash light in order to be able to take photographs of high quality. It is an object of the invention to provide a flash housing and a method performed within a flash housing, which is able to create a desired beam lobe of flash light.

According to one embodiment, a flash housing for photographic purposes is provided. The flash housing comprises: a flash forming element arranged to generate a flash light; and a lens element arranged to let at least part of the generated flash light out of the flash housing, wherein the flash housing is arranged to emit a beam lobe with an essentially circular cross section.

By emitting a beam lobe with an essentially circular cross section, the photographer is able to create a photograph with high quality. In addition, according to one aspect, the border of the cross section of the beam lobe emitted from the flash housing is even, which further improves the quality of the photograph. The even border of the cross section of the flash light beam lobe is a border or edge of said cross section which fades away evenly and with an even distribution of light along the border so that there are no sharp edges. In other words, the light intensity around the border of the cross section of the flash light beam lobe does not vary to a large extent. In addition, the light intensity of the cross section of the flash light as a whole does not vary to a large extent which creates a flash light with high quality. According to one example, the flash light beam lobe is only used on a part of the photograph, thereby creating a dynamic photograph of high quality.

According to one embodiment, the flash housing is attached to a flash holder. The flash holder and the flash housing form a flash device. The flash device is according to one example releasably attachable to a camera device.

According to one embodiment, the flash forming element comprises: a flash tube; and a reflector. According to one embodiment, the flash forming element comprises a lamp and a reflector.

A flash tube enables emitting a flash light of high intensity which often is desired when taking a photograph. According to one embodiment, the flash tube is straight.

In small flash devices, such as a flash device which is removably attachable to a camera, the volume within which the flash tube is fitted is limited. It is often difficult to create a small flash tube of a different shape, such as a horse shoe shape etc.

According to one embodiment, the reflector shape/form and the design of the lens element cooperate to obtain the beam lobe with the essentially circular cross section.

Normally, if a circular cross section of a beam lobe of a flash light is desired, the flash tube should be circular, or essentially circular, such as horse shoe shaped or circular shaped. In addition, a circular reflector should be used. However, in this specific case when a straight flash tube is used, the light emitted from the flash tube does not create a flash light beam lobe of a circular cross section. Hence, the emitted flash light beam lobe has to be reshaped in order to be able to create the desired beam lobe with a circular cross section. This reshaping of the flash light is performed by the shape or form of the reflector in combination with the design of the lens element. According to one embodiment, the shape or form of the reflector in combination with the design of the lens element may be used for forming a beam lobe with a cross section of a desired shape. By using both the shape or form of the reflector and the design of the lens element for reshaping the flash light beam lobe, a desired shape of the cross section of the flash light beam lobe may be achieved. In addition, a desired light distribution within the flash light beam lobe may be achieved, such as an even distribution of light within the flash light beam lobe. According to one embodiment, the light evenly fades away around the border of the cross section of the flash light beam lobe.

According to one example the flash forming element is axially movable within the flash housing to control the beam angle of the beam lobe of the emitted flash light. By controlling the beam angle of the beam lobe, a user friendly flash housing is achieved, wherein the photographer may adjust the beam lobe of the flash light according to the photograph to be taken.

According to one example, the lens element comprises an outer surface and an inner surface. The inner surface of the lens element is the surface of the lens element facing the flash housing. The outer surface of the lens element is the surface of the lens element facing the surrounding of the flash housing. The outer surface and the inner surface may be configured to affect the flash light differently.

By using both surfaces of the lens element to affect the beam lobe of the flash light, an optimal result may be achieved.

According to one example, the outer surface of the lens element comprises a first and a second area wherein the respective areas affect the flash light differently. By dividing the outer surface of the lens element into two areas, the beam lobe may be adjusted in order to receive an optimal result, that is an optimal cross section of the beam lobe of the flash light. According to one embodiment, the outer surface of the lens element is divided into at least three areas. The respective areas may be adjusted so that the adjustment of the flash light is adjusted to where in the flash housing the flash forming element is positioned. The position of the flash forming element affects which area on the lens element will be hit by the most intensive flash light. For example, if the flash forming element is positioned in an end position closest to the lens element, the central area of the lens element will receive most of the flash light emitted from the flash forming element due to the shape of the flash tube. Hence, the central section of the lens element may be adjusted in order to affect the flash light in a desired manner when the flash forming element is in this end position. According to one example, if the flash forming element is positioned in an end position most distant from the lens element, the whole area of the lens element will receive most of the flash light. Hence, the larger area surrounding the central section of the lens element may be adjusted in order to affect the flash light in a desired manner when the flash forming element is in this end position. According to one example, the first area of the outer surface is arranged to not affect the flash light. The first area is arranged in the centre of the lens element.

The first area of the outer surface is according to one example arranged to not affect the flash light in order to be able to receive a maximal beam angle when the flash forming element is at an end position within the flash housing, closest to the lens element. Hence, a flash light beam lobe with a desired cross section shape and a desired beam angle may be achieved.

According to one example the second area of the outer surface is arranged to focus the flash light. The second area is surrounding the first area. By focusing the flash light, a beam lobe with a desired shape, desired beam angle and desired flash light intensity may be achieved. In addition, a flash light beam lobe, with an even distribution of flash light in the cross section of the beam lobe of the flash light may be achieved. The distribution of flash light refers to the intentsity distribution of the flash light. According to one example the inner surface of the iens element comprises a first and a second area wherein the respective areas affect the flash light differently. According to one embodiment, the inner surface of the lens element comprises at least three areas which areas affect the flash light differently.

By dividing the inner surface of the lens element into two areas, the beam lobe may be adjusted in order to receive an optimal result, that is an optimal cross section of the beam lobe of the flash light.

According to one example, the first area of the inner surface is arranged to disperse the flash light in direction perpendicular to the direction of the axis of the flash tube. The first area is arranged in the centre of the inner surface of the lens element. The first area of the inner surface is according to one example arranged to disperse the flash light in direction perpendicular to the axis of the flash tube in order to be able to receive a maximal beam angle when the flash forming element is at an end position within the flash housing, closest to the lens element. Hence, a flash light beam lobe with a desired cross section shape and a desired beam angle may be achieved. The first area of the inner surface of the lens element evens out the flash light beam lobe when the flash forming element is positioned at a desired position in the flash housing. Due to the shape of the flash tube the first area will be hit by an intense flash light and hence, the first area will enable shaping the flash light beam lobe, and even out the distribution of light in the flash light beam lobe. According to one example the second area of the inner surface is arranged to disperse the flash light in all directions, wherein the dispersion of the flash light in the direction perpendicular to the axis of the flash tube is larger than the dispersion of the flash light in the direction aligned with the axis of the flash tube. The second area of the inner surface of the lens element surrounds the first area. According to one example, the flash light which is reflected in the reflector and the flash light going straight from the flash tube to the lens element has an uneven intensity distribution in a direction perpendicular to the axis of the flash tube. The second area of the inner surface of the lens element spreads the flash light in this vertical direction, creating a beam lobe emitted from the flash housing with a more even intensity distribution, and in addition, with an essentially circular cross section with an even border of the cross section of the beam lobe.

According to one embodiment, a method performed within a flash housing for photographic purposes for emitting a beam lobe of flash light is provided. The method comprises: generating a flash light by means of a flash tube, modulating the generated flash light by means of a reflector and a lens element arranged to let at least part of the generated flash light out of the flash housing, which lens element comprises an outer surface and an inner surface, wherein the outer surface of the lens element comprises a first and a second area wherein the respective areas affect the flash light differently, and wherein the inner surface of the lens element comprises a first and a second area wherein the respective areas affect the flash light differently, said modulating comprises modulating the generated flash light to emit a beam lobe with an essentially circular cross section.

By emitting a beam lobe with an essentially circular cross section, the photographer is able to create a photograph with high quality. In addition, according to one

embodiment, the border of the cross section of the beam lobe emitted from the flash housing is even, which further improves the quality of the photograph. According to one example, the flash light beam lobe is only used on a part of the photograph, thereby creating a dynamic photograph of high quality. According to one embodiment, the light distribution within the beam lobe is even which improves the quality of the flash light emitted from the flash housing. The light distribution is affected by the flash tube, the reflector and the lens element.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following description of embodiments of the proposed technique, reference will be made to the accompanying drawings of which: Figure 1 schematically illustrates a flash device according to different embodiments.

Figure 2a schematically illustrates a flash housing according to different embodiments.

Figure 2b schematically illustrates components of a flash housing according to different embodiments.

Figure 3a schematically illustrates a flash housing according to different embodiments. Figure 3b schematically illustrates a flash housing according to different embodiments.

Figure 4a-c schematically illustrates a reflector according to different embodiments.

Figure 5a-b schematically illustrates a lens element according to different

embodiments.

DETAILED DESCRIPTION

The cross section of the beam lobe is the cross section perpendicular to the main direction of light. In other words, the cross section is aligned with the direction of the axis of the flash tube.

Figure 1 illustrates a flash device 1 according to one example. The flash device 1 is arranged to be used for photographic purposes. According to one example, the flash device 1 is arranged to be releasably attachable to a camera. The flash device 1 comprises in the illustrated example a flash holder 20 and a flash housing 2 hinged onto the flash holder 20. The flash device further comprises a releasable battery 30, attached to the flash holder 20. The flash housing is equipped with a lens element 3 arranged to affect the generated flash light in a desired way.

Figure 2a schematically illustrates a cross section of a flash housing 2, used for photographic purposes, viewed from above. The flash housing 2 is arranged to emit a beam lobe 100 of flash light. The flash housing 2 comprises a flash tube 9 partly enclosed by a reflector 4. In a not illustrated example, an alternative flash forming element may be used, for example a lamp and a reflector. The flash tube 9 is in the illustrated example straight. The flash tube may instead have another shape. The reflector 4 has in the illustrated example an essentially oval cross section. The reflector 4 is three dimensional and of a parabola shape. The reflector 4 is arranged to reflect at least part of the flash light emitted from the flash tube 9 in order to direct substantially all of the flash light generated by or emitted from the flash tube 9 towards a lens element 3. In addition, the reflector 4 is arranged to reflect at least part of the flash light in order to make the cross section x of the reflected part of the flash light beam lobe directed towards the lens element 3 as circular as possible, given the available space and construction of the flash housing 2 and the components within the flash housing 2.

The reflector 4 and the flash tube 9 are in the illustrated example arranged in a holding element 8. The holding element 8 may be made of a material which is heat resistant, for example ceramics, glass, metal or similar.

The holding element 8 is in the illustrated example arranged in a carrier 7 which is movably attached to the flash housing 2 by means of a number of guiding elements (not disclosed). The carrier 7 is arranged to be axially movable inside the flash housing 2. A positioner 6 positions the carrier 7 axially in the flash housing 2. According to one embodiment, the positioner comprises a step motor. The position of the carrier 7 and thereby the flash tube 9 and the reflector 4 affects a beam angle a of the emitted beam lobe 100. When the carrier 7 is positioned in an end position close to the lens element 3, the beam angle a of the beam lobe 100 is a maximum beam angle for the beam lobe 100 of the emitted flash light. When the carrier 7 is positioned in an end position most distant from the lens element 3, the beam angle a of the beam lobe 100 is a minimum beam angle a for the beam lobe 100 of the emitted flash light. The lens element 3 is arranged to let at least part of the flash light generated by the flash tube 9 and the reflector 4 out of the flash housing 2. Ideally, ail of the light generated by the flash tube 9 and the reflector 4 is emitted from the flash housing 2. However, some of the flash light may be absorbed by the inner walls of the flash housing 2 etc. The lens element 3 comprises an outer surface 3a and an inner surface 3b. According to an example, the respective surfaces 3a, 3b affect the flash light differently.

Figure 2b schematically illustrates an exploded view of the carrier 7, the holding element 8, the reflector 4 and the flash tube 9. Figure 3a schematically illustrates a flash device 1 comprising a flash housing 2 and a flash light beam lobe 100 emitted from the flash housing 2. The flash light beam lobe has a beam angle a and an essentially circular cross section x.

Figure 3b schematically illustrates the flash device 1 comprising a flash housing 2 and a flash light beam lobe 100 emitted from the flash housing 2 from a front view.

Figure 4a -c is a schematic illustration of the reflector 4 viewed from different angles, see the coordinate systems illustrated in the figure. Figure 4a is a front view of the reflector 4. The sides of the reflector 4 are shaped in order to be able to fit a flash tube 9. As can be seen, the reflector 4 is of an essentially oval shaped cross section. Figure 4b illustrates a cross section of a side view of the reflector 4. Figure 4c illustrates a side view cross section of the reflector. The reflector has a certain expansion or depth and formation or design in the z-direction of the coordinate system of figure 4a. In addition, the reflector has a certain extension and formation in the x-direction of the coordinate system of figure 4a. In addition, the reflector has a certain extension and formation in the z-direction of the coordinate system of figure 4a. The variables in the x, y, and z-directions or, in other words, the design of the reflector is a result of experiments for making the flash light reflected in the reflector create a beam lobe with an as circular cross section as possible. In addition the reflector is arranged to create a beam lobe with a cross section of essentially the same size as the lens element when the flash forming element 9 is in its end position in the flash house, distant from the lens element 3. Figure 5a is a schematic illustration of an outer surface 3a of a lens element 3. The outer surface of the lens element 3 is the surface of the lens element which is furthest away from the flash forming element 4, 9. The outer surface 3a of the lens element 3 comprises a first 30 and a second area 35. The respective areas 30, 35 affect the flash light differently. The first area 30 is an elongated shape which is elongated in a direction aligned with the direction of the axis of the flash tube 9. The first area 30 is positioned in the centre of the lens element 3. According to the illustrated example, the elongated shape of the first area 30 of the outer surface 3a is an oval. The shape of the first area 30 may vary. The first area 30 is arranged to not affect the flash light. The second area 35 is surrounding the first area 30. The second area 35 is arranged to focus the flash light.

Figure 5b is a schematic illustration of an inner surface 3b of a lens element 3. The inner surface 3b of the lens element 3 is the surface of the lens element 3 facing the flash forming element 4, 9. The inner surface 3b of the lens element 3 comprises a first 40 and a second area 45. The respective areas 40, 45 affect the flash light differently. The first area 40 is an elongated shape which is elongated in a direction aligned with the direction of the axis of the flash tube 9. The first area 40 is arranged in the centre of the lens element 3. According to the illustrated example, the shape of the first area 40 corresponds to the shape and size of the flash tube 9 or to the area that will receive the most intensive light from the flash tube. The first area 40 is arranged to disperse the flash light in a direction perpendicular to the direction of the axis of the flash tube 9. The second area 45 is surrounding the first area 40. The second area 45 is arranged to disperse the flash light in all directions, wherein the dispersion of the flash light in the direction perpendicular to the direction of the axis of the flash tube 9 is larger than the dispersion of the flash light in the direction aligned with the axis of the flash tube 9.

The reflector 4 and the design of the lens element 3 cooperate to obtain the beam lobe 100 with an essentially circular cross section x. In addition, the reflector 4 and the design of the lens element 3 cooperate to obtain a beam lobe of flash light with an even intensity distribution of flash light, and with a border of the cross section of the flash light which is soft and even.

When the flash tube generates a flash light, part of the flash light will be reflected in the reflector 4 and part of the light will go straight from the flash tube 9 towards the lens element 3. According to one example, when the flash forming element 4, 9 is in its end position distant from the lens element 3, the part of the flash light going straight from the flash tube 9 toward the lens element 3 will have a beam lobe with a cross section of a size corresponding to the size of the cross section of the lens element 3. However, since the shape of the flash tube 9 is straight, focused light from the flash light will have a rectangular shape aswell. have a shape that corresponds to the shape of the flash tube 9, that is, a rectangular shape. Due to the laws of optics, the intensity of the light close to the edge of the cross section of the beam lobe will be weaker that he intensity of the light in the centre of the cross section of the beam lobe. The beam lobe of the part of the light which is reflected in the reflector 4 will have a rounder cross section due to the shape of the reflector 4. The flash housing, the flash tube 9 and the reflector 4 are arranged to create beam lobes with cross sections that corresponds to the size of the cross section of the lens element or that are smaller than the cross section of the lens element in order to minimize flash light hitting the inner parts of the flash housing 2, so that all of the flash light will be transmitted through the lens element 3.

The first area 40 of the inner surface of the lens element 3 is arranged to disperse the flash light in direction perpendicular to the axis of the flash tube 9. The major part of the flash light hitting the first area 40 of the inner surface of the lens element 3 when the flash forming element is in its end position closest to the lens element, is flash light that goes straight from the flash tube 9 towards the tens element 3, hence, the light in the centre of the cross section of the beam lobe of flash light going straight from the flash tube 9 towards the lens element 3. By means of the first area 40, this part of the flash light which comprises intensive flash light will be dispersed in a direction perpendicular to the axis of the flash tube 9. The other part of the beam lobe of flash light going straight from the flash tube 9 towards the lens element 3, and the beam lobe of reflected flash light will to a large extent hit both the first and the second area 40, 45 of the inner surface 3b of the lens element 3. The second area 45 of the inner surface 3b of the lens element 3 is arranged to disperse the flash light in all directions. Further, the dispersion of the flash light in the direction perpendicular to the axis of the flash tube 9 is larger than the dispersion of the flash light in the direction aligned with the axis of the flash tube 9. This dispersion will partly compensate for the uneven intensity distribution of flash light in a cross section of a beam lobe of the flash light, both the part of the flash light that goes straight from the flash tube to the lens element 3 and the part of the flash light that is reflected in the reflector 4 before hitting the lens element 3. By means of this design of the inner surface 3b of the lens element 3, the beam lobe of flash light is affected so that the cross section of the beam lobe will be essentially circular. In addition, by means of this design, the flash light is evenly distributed within the beam lobe.

The first area 30 of the outer surface 3a of the lens element 3 is arranged to not affect the flash light. The second area of the outer surface 3a of the lens element 3 is arranged to focus the flash light. Hence, when the flash forming element 4, 9 is in its end position distant from the lens element 3, the cross section of the beam lobe of the flash light transmitted through the inner surface 3b is essentially of a circular shape. The second area 35 of the outer surface 3a is arranged to focus the flash light, and hence to create a beam lobe with an as small cross section as possible for that specific device. The part of the beam lobe hitting the first area 30 will not be focused. However, this part of the flash light is not very large when the flash forming element 4, 9 is in its end position distant from the lens element 3.

According to one example, when the flash forming element 4, 9 is in its end position closest to the lens element 3, a large part of the flash light emitted from the flash tube 9 will hit the first surface 40 of the inner surface 3b of the lens element. Hence, the large part of the flash light will be dispersed in a direction perpendicular to the axis of the flash tube. The part of the flash light reflected by the reflector 4 and the part of the flash light that goes directly from the flash tube 9 towards the lens element 3 and which does not hit the first area 40 of the inner surface 3b will hit the second area 45 and hence be dispersed in all directions, but wherein the dispersion in the direction perpendicular to the axis of the flash tube 9 is larger than the dispersion of the flash light in the direction aligned with the axis of the flash tube 9.

Once the beam lobe of the emitted flash light hits the outer surface 3a of the lens element 3, the part of the beam lobe which hits the first area 30 is not affected by the outer surface of the lens element, and hence, the beam angle of this part of the flash light will not be affected. The part of the beam lobe of the flash light hitting the second area 35 of the lens element 3a will focus the flash light. However, since most of the flash light will hit the first area 30, 40 of the inner surface 3b and the outer surface 3a, the dispersion of the flash light will be large, and hence a beam lobe with an as large cross section as possible for that specific device is created.

The flash tube 9 together with the reflector 4 and the lens element 3 together form a beam lobe of flash light with a cross section which is substantially circular. In addition, the reflector 4 and the lens element 3 affect the flash light so that the border of the cross section of the beam light is even and so that the light intensity distribution within the flash light beam lobe is even. The even distribution of flash light within the beam lobe, the circular cross section of the flash light beam lobe and the even border of the cross section of the flash light beam lobe enables a photographer to take a photograph of high quality.

According to one aspect is also disclosed a method performed within a flash housing 2 for photographic purposes for emitting a beam lobe of flash light is provided. The method comprises:

- S1 : generating a flash light by means of a flash tube 9,

- S2: modulating the generated flash light by means of a reflector 4 and a lens element 3 arranged to let at least part of the generated flash light out of the flash housing, which lens element comprises an outer surface 3a and an inner surface 3b, wherein the outer surface 3a of the lens element 3 comprises a first 30 and a second area 35 wherein the respective areas 30, 35 affect the flash light differently, and wherein the inner surface 3b of the lens element 3 comprises a first 40 and a second area 45 wherein the respective areas 40, 45 affect the flash light differently, said modulating comprises modulating the generated flash light to emit a beam lobe with an essentially circular cross section.