FI117806B - Flash Device - Google Patents

Description

117806

Flash Device

The invention relates to a flash unit according to the preamble of claim 1.

When shooting in poor lighting conditions, a flash connected to the camera is used to illuminate the subject. Current digital cameras are often designed to be so compact that, due to lack of space, the light source of the flash has to be moved inside the camera near the lens; such 10 cameras are e.g. almost all flashes integrated into existing personal digital cameras equipped with digital cameras.

The light sources used in the photographic technique generally emit light in all directions and their radiation intensity varies greatly in different directions.

In current digital cameras, light enters the illuminated area from the light source, generally through a circular or at least circular symmetrical aperture / lens, causing the illuminated area to become more or less circular. However, since films and most other image recording and viewing systems (such as television, LCD projectors) are usually based on more or less rectangular, for example, rectangular, image areas (e.g., TV 4: 3), they arrive at corners of the illuminated area. easily less light than other parts, which naturally reduces *: * ·: picture quality. Digital cameras that are connected to mobile devices **: · like mobile phones, there is still a particular problem with low battery power, which • · * *; * · *. limits the power of the light source used in the flash unit. When illuminating 25 subjects with a low-power light source, the area of the image is easily formed if the light source emits too much light outside the field of view.

Some lighting systems for solving the above problem are known in the art. For example, a system is known from US-A-30 5 823 662 in which light emitted from a light source is collected by a suitable, generally rectangular lens on one side of the light source and a light reflected from the light source in the opposite direction. It is mentioned in the publication that the system is capable of collecting more than 50% of the light emitted by the light source into the desired rectangular area. However, with regard to current digital cameras mounted on, for example, portable telephones, the system known from the above-mentioned US patent is insufficient in light collecting power, because flashes installed inside digital cameras 5 have to use relatively low power light sources. Further, the illumination system disclosed in the aforementioned U.S. Patent is too complex and bulky to be used as a flash light target for digital cameras.

It is an object of the invention to overcome the drawbacks of the prior art described above. Accordingly, it is a first object of the invention to provide a flash unit, particularly adapted for use inside digital cameras, capable of directing light emitted from a light source to a substantially rectangular (rectangular or square) illuminated area. Another object of the invention is to provide a flash light device 15 whose light collection system is capable of targeting almost all of the light from a light source to a desired area. It is a third object of the invention to provide a flash unit which provides a uniform illumination of the target area.

The foregoing objects are achieved by the flash unit 20 of claim 1, wherein the light source is in close proximity to the lens inside the photographic device and the light emitted by the light source is converted through the lens to illuminate an approximately rectangular region. In a flash unit, the light source is an LED that emits a circular meter of light *: ··: and the lens has a refractive area as well as a total reflective area, the lens ·: · 25 consisting of a single unit. Preferably, most of the light intensity, preferably greater than 80%, of the light emitted by the LED is derived from light whose emission direction is scattered perpendicular to the direction of the light rays through the front face of the LED and the outer surface of the lens.

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The invention is based on the fact that the circumferential light distribution emitted by the LED placed inside the camera is changed by a uniform inner and outer surface! ···. through a lens such that the area to be illuminated is substantially square or * · '** rectangular. The lens itself has two distinct areas: the refractive area of the lens * · ·, which is located in the center of the lens, and the total reflection area of the lens, 4 · ·: the region of reflection of the lens located in the periphery of the lens. There are still two different optical surfaces in the refractive area of the inner surface of the lens 35: a center surface which already forms a final rectangle (rectangle or square) of the 3 117806 illuminated area and the circumferential surface around the center surface to balance the intensity of light entering the area. The total reflective edge region of an ounce generally consists of a first surface guiding light rays to a second surface in a direction parallel to or nearly parallel to it and a second reflecting surface at a 90 degree angle to its incident angle.

The advantage of such a lens over the lighting system disclosed in U.S. Patent No. 5,823,662 is its structural simplicity (only one lens) and hence the small space requirement, which makes it well suited for flash light targeting in digital cameras.

In a preferred embodiment of the invention, the light source of the flash unit is located inside a mobile device with a digital camera, such as a mobile phone, close to the camera lens. Particularly in mobile phones, the flash unit of the invention achieves 15 significant advantages over known flash units because the total amount of light emitted by the light source used in the flash is easily reduced due to the limited duration and power of the power source (battery). If a conventional flash unit were to be used on the flash units of cellular phones, the illuminated image area would easily be poorly and unevenly illuminated because they would reduce the illumination power by illuminating areas outside the image area. In contrast, the flash unit of the invention having an LED and a lens having a single lens surface consisting of two different optical areas, despite the relatively low illumination intensity of the LED, provides a good *: · 25 and even illumination of the entire image area.

The invention will now be described in more detail with reference to the accompanying drawings.

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Figure 1 shows the intensity of the radiation emitted by the LED and the distance of the beam in degrees from the light source to the direct direction: 30.

* ·· • ·. Fig. 2 is a schematic side elevational view of the lens and light source (LED) of the flash unit of the invention.

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Figure 3A is a photograph of the center surface of the lens of the flash unit of the invention.

Figure 3B shows a pattern provided by the center blades of the lens of the flash device according to the invention.

Fig. 3C is a photograph of the total reflective edge of the lens of the flash unit of the invention.

Figure 3D is a view of the entire lens provided by the flash unit of the invention.

Fig. 4 is a partial sectional view illustrating a lens of a flash device according to the invention.

Fig. 5 is a horizontal sectional view of an area illuminated by a flash device according to the invention.

The light distribution provided by LED 3 as such without the lens is shown in the diagram of Figure 1. This graph shows the relative intensity (%) of the light emitted by the LED on the vertical axis and the angle of the radiation in degrees on the horizontal axis in degrees perpendicular to the direction of the LED (reference direction, ie, the direction is zero perpendicular to the LED surface). . The light beams emitted from the LED are completely * ·· scattered across the front of the LED and scatter at most • · «·. ···. 20 At an angle of 90 degrees from the front of the LED perpendicular to the direction of the light from the front. In fact, more than 70% of the total intensity of the light emitted by the LED is scattered below 60 degrees and only about 40% at an angle greater than 60 degrees from the • · ** ·· 'direction of the light beams directly forward. The light distribution of the radiation emitted by the LED is circular asymmetrical from the 25 LEDs directly forward of the light rays passing through the plane of the LED face.

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The light source device according to the invention comprises a light source 3 as shown in Fig. * 2: LED 2 and a lens 2 having a uniform inner surface 20 and a uniform outer surface: ···: 200; 40 pass through the lens 2 of the flash unit 1 according to the invention as shown in Figure 2, first penetrating the inner refractive and reflective surface 20 of the lens and then the outer surface 200 of the lens flush with the body (not shown). near the inner surface 20 of the lens, for example a digital camera! -: 5 117806a, the lens 2 being either of the same material as the cellular body (e.g., a transparent plastic such as acrylic) or a separate lens embedded in the cellular body 200. The inner surface 20 of the ounce 2 is comprised of a central region 20; K, which refracts light beams 4, and a peripheral region 20, R reflecting the light beams, which will be described in more detail below. All optical surfaces of the lens 2 are so-called free. who compile uv various geometric curves and surfaces. The free-form surface 10 is a surface that is not limited to classical analytical forms, such as conical surfaces, and is defined as a surface passing through a set of control points (such as Bezier, b-spline, and NURBS surfaces). The optically active area of the ounce is generally square. The exact shape of the refractive and overall reflective inside of the lens is based on the well-known Snell Law and its application to the particular lens material. Reference is made to known literature in the art, such as Warren J. Smith's "Modern Optical Engineering" or Born & Wolf, "Principles of Optics".

Lens 2 on optically active inner surface 2; 20 is the midpoint 20a of a relatively small area 20 of central area K through which, however, much of the light 4 emitted by the LED passes; 40. Said center 20a is rectangular and is designed as a refractive surface. The middle of 20a · · ♦ * ·. * :! a side face is attached to the side of the lip, which together form a light-refractive center circumference 20b of the central region K. The peripheral surface 20b thus consists of: four side faces facing toward the outer surface, the figure showing the side face 20b3, and partly the side faces 20b1 and 20b2, which face the various sides and sides of the central C. * region. In the lens 2 shown in Fig. 2, the center surface or center 20a of the inner surface 20 of the inner region 20 is drawn near ♦ · 'as a light source LED 3 than said central surface 20a · · · ·: ***; The lateral facets of 30 associated peripheral surfaces 20b facing away from the LED used as light source 3. When used as a reference plane, · · a somewhat planar, straight face 200a of the outer surface 200 of the lens is: ···: greater than this reference plane 200a a side surface of the peripheral surface 20b associated with the central surface and inclined towards the outer surface 200; ·· *. 35 facets.

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Usually, more than 60%, often up to 80-90% of the light 4 emitted by the LED 3 used as the light source passes through the center 20 of the light refractive center K of the inner surface of the lens 2; 40, depending on the light distribution emitted by the LED or other light source and the shape of the area 5 illuminated by the flash unit 1 being present. Said refractive surfaces, i.e. the central surface 20a and the lateral faces of the peripheral surface 20b connected to its edges, are formed by combining the curves into a free-form curve. Each curve is calculated to refract light 4 on a surface defined by the curve to a specific angle. The freeform curves are then connected to each other to form a continuous continuous freeform surface.

Lens inner surface 2; The inner surface region associated with the lateral facets of the light refractive peripheral surface 20b, herein referred to as the edge region R, is designed to reflect substantially all of the light incident thereon 4; 40 (ie the area is designed to be fully reflective). The first surface 20c of said light reflecting edge region 15R curves upward (the reference surface again being the plane 200a of the outer surface 200a of the lens), rising higher than the horizontal plane T extending through the top of the central surface 20a. The first surface 20c of the light reflecting region, or edge region R, shown in Figure 2, is substantially symmetrical in shape with respect to a central axis P piercing the inner surface of the lens 2. Hereby, portions of the first surface at the same distance from the central axis P are of the same shape and located at the same distance from the front surface of the outer surface of the lens \ 200 *. The second surface of the total reflective edge region R, i.e. the total reflective ** ··. * Region 20d, is directly connected to said first surface 20c, at the highest point from the outer surface 200a of the outer surface of said surface 20c, inclined therefrom and curved toward the outer surface of the lens. • · * 200a. Also, the overall reflecting second region (surface) 20d is substantially symmetrical in shape and location; The surfaces of the total reflective region 20d, which are located at the same distance from the central axis of the lens through the inner surface of the lens, are of the same shape and located at the same distance from the plane of the lens surface 200a. The first surface 20c of the peripheral region R aligns the light rays from LED 3 at different angles to this surface • · * ”· '4; 40 at an angle such that the light rays 4; 41 arrive at the second (whole) reflective region 20d at an angle such that substantially all of the light beams 41 are reflected through the second surface 20d at an angle of about 90 degrees to its direction of incident. The boundary angle of total reflection can be derived from the well-known Snell law. Said first surface 20c is formed by combining the curves into a free-form curve. Each curve is designed so that the incident light rays align it. The free-form curves are then combined into spatulas, which in turn are connected to each other to form a continuous, uniform free-form plating. Said second, total reflective region 20d is formed by combining the curves into a free-form curve. Each curve is designed to reflect light to it at a specific angle within a desired range. The free-form curves are then combined to form spatulas, which in turn are connected to each other to form a continuous, uniform shape.

The exact shape of the inner surface 20 of the lens 2 depends on several factors: the distance between the lens 2 and the light source 3, the light 4 emitted by the light source; 40, the intensity distribution, the desired shape of the illuminated area, etc. The lens-LED combination shown in Fig. 2 is intended to illuminate a square, whereby the front face 200a of the lens used therein is approximately square in shape. For example, if the aim were to illuminate a 4: 3 rectangular area, the overall face of the lens would have a more or less rectangular shape.

Figure 4 is a perspective and partially sectional view of the lens 2 of the flash unit of the invention. The figure shows the lens as well as its contact points in its operating environment, such as the shell of a mobile phone. Both surfaces (inner and outer) of the lens 2 ... T are made of acrylic or other transparent plastic material, and the outer surface 200 is smooth in this case, making it *: ··: suitable for use as an exterior surface of a mobile phone. Lens 2 ·: 25 is connected to the other parts of the phone via extensions of the inner surface 20. In the figure «· · ·. · * ·. there are also visible drainage channels 8 of the lens 2 through which the plastic is fed into the mold when the lens is molded. Injection molding preferably employs a 2-component injection molding to integrate a lens of one plastic type with surrounding support structures of another plastic type, such as a shell of a mobile phone * "· * 30. The LED (not shown) can be positioned very close to lens I '* the inner surface 20 so that the camera built into the mobile phone becomes very flat.

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In a preferred embodiment of the invention, a hard protective film of lt *: V is still transparent on the lens 2 during injection molding.

8 117806

Figures 3A-3D illustrate how to form a rectangular (square) pattern 5 with a lens-LED combination according to the invention; 50. This pattern consists of light 4 passing through different optical regions (20a, 20b, 20c and 20d) of the inner surface of the lens 20; 42.

Figures 3A to 3C illustrate separately the pattern formed by each optically active portion of the lens, and Figure 3D shows the overall pattern formed by the lens.

Figures 3A to 3D represent the relative light intensity (%) of the respective light hood intensity. 100 in the figures thus denotes a peak intensity of 10 light and 0 denotes no light reaching the surface.

When passing through the light-refracting center surface 20a of the inner lens surface, light rays 4 emanate from the LED; 40 are folded so that a final illuminated area of rectangular shape is already formed (Fig. 3A). In the photograph 5 formed by this portion of the lens; However, the intensity of the 51 light is not yet even within the illuminated rectangle, but the center and corners of the illuminated area are illuminated more than other parts. In photo 5; 51 A represents high illumination intensity, I = 100-73%. B denotes medium high luminous intensity I = 41-72% and C denotes low luminous intensity I <41%. The peak intensity here is 72.5116 cd.

Light beams 4 arriving from the LED to the area of the peripheral surface 20b surrounding the central surface 20a of the central region; 40, in turn, fold so that the light beams 4 emanating from this region * · ♦ · * form a pattern 5; 52. In Figure 5; The maximum intensity of the incident light 52 is immediately adjacent to the edges of the rectangular region (Fig. 3B). This refractive area of the inner surface of the lens 20b does not reach much light into the center of the rectangle itself, the area is already illuminated through the central surface 20a. In this part of the photo ···, A means high illumination intensity, where I = 73-100%. B mer- ···. limits medium high intensity I = 40-72% and C low light intensity I / 40%. The peak intensity here is 47.87 cd.

· · · ··· T ": 30 The light reflected from the LED 2 at the total reflective edge region R receives relatively little light, often only about 10-20% of the total amount of light emitted from the LED!: *: * 4; 40 (Fig. 3C). The light passing through the edge region R * · ·: · 'forms a pattern 5, 53 which complements the patterns 5, 51 and 5; 52. More light arrives in the center of the illuminated area (area A) and 9 117806 more (areas). B and C) In this figure, A represents a high luminous intensity where I = 76 -100%, B represents a medium high intensity I = 41-75% and C a low luminous intensity I <41% .The peak intensity here is 65,221 cd.

Fig. 3 is a composite pattern of light transmitted by the optical surfaces 20a, 20b, 20c and 20d of the lens shown in Fig. 3D; 51, 5; 52 and 5; 53 sum and roughly square in shape. In this photograph area 5; The 50 most luminous rectangular or square areas are in the center and I = 71-100%. The edges of the illuminated area have a somewhat less illuminated peripheral area with a luminous intensity of I = 39-70%. Outside of these illuminated areas A and B, there is a very poorly illuminated area C, where I <38%. The peak intensity here is 93.69 cd.

Figure 5 further shows a cross-section of the illuminated area formed by the flash unit of the invention in a horizontal direction. From the figure it can be seen that the light intensity (given as a percentage of the peak intensity) drops sharply outside the edges of the illuminated square area. In Fig. I, denotes the intensity as a percentage of the peak intensity and X denotes the point of observation.

Only certain embodiments of the invention have been described above, and it will be apparent to one skilled in the art that the invention may be practiced in many other ways within the scope of the appended claims.

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Thus, the lens generally has a square or rectangular shape *: **; depending on the shape of the image area you want to illuminate. Alternatively, the shape of the face, edge and center of the lens 25 may also be realized in other shapes.

The overall reflective edge region R may also be implemented such that the edge region R is partially or fully metallised. In this case, the peripheral area no longer has a first surface 20c which directs the light rays to a specific path * · .. to the other surface (area) 20d of the earth, because the peripheral area reflects the outgoing light rays at a given angle to the incident angle of because of its structure.

The distribution of light emitted by the LED shown in Figure 1 applies only to a particular type of LED available on the market, and the distribution of light naturally varies. 10 inches when changing the LED type. However, the pattern given by the LED is quite typical of the LEDs available today.

The flash unit of the invention can be used in photographic equipment, especially photographic equipment for digital imaging. 5 The photographic device may also be part of a device primarily used for other purposes, such as mobile communication devices used primarily for communication.

The luminous intensity of the illuminated rectangular area obtained with each lens also depends greatly on the light source. Thus, the illumination intensity values (relative and absolute) given to the lens and its components in the example illustrated above may vary considerably depending on the shape of the lens and the power of the respective light source.

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Claims (14)

1. A flash unit (1) having a light source (3) in the immediate vicinity of the lens (2), inside the camera, and the light (4; 40) emitted from the light source is changed by mediating said lens to illuminate approximately tangular region, characterized in that - the light source of the flash unit (1) is a light emitting diode (3) which emits circular symmetrical light; is formed by a uniform piece - the area that refracts light in the lens (2) is located at the center region (K) of the inner surface (20) of the lens and the region that reflects the light of the lens is located at the edge region (R) of the inner surface of the lens. The flash assembly (1) of claim 1, comprising a light source which is a light emitting diode (3), wherein most of the intensity of its emitted light, in particular above 60% and preferably over 80%, originates from light rays which is directed from the light source to the lens, so that their direction of travel deviates no more than 60 degrees from the direction of light rays traveling perpendicular to the lens (2) via the front surface of the LED. Flash assembly (1) according to any preceding claim, characterized in that the lens (2) comprises a uniform inner surface (20) and a uniform outer surface (200) and on the inner surface (20) of the lens. light refractive area and a re-! ···. rim that totally reflects light and the outer surface of the lens is straight or double curved. «M Lightning assembly (1) according to claim 1, characterized in that the center region (K); 7 which shines light on the inner surface (2; 20b) of a lens comprises a center surface (20a), with the aid of which most of the rectangular shape of light patterns (5; 50) is illuminated with the flash unit and by the circumferential surface (20b) around the center surface, by means of which the light intensity of the illuminated area is equalized. • · · «·. t · • · ··· 14 1 1 7806 Lightning assembly (1) according to any of the preceding claims, characterized in that the peripheral surface (20; 20b) is formed by four side surfaces which are connected to the central surface, which are inclined towards the outer surface (200) of the contact point. Lightning assembly (1) according to any of the preceding claims, characterized in that the total reflecting edge area (R) on the inner surface (20) of the lens (2) is provided by a first surface (20c), which controls the light rays coming towards it. generally or almost parallel to a second surface (20d), and of said second reflecting surface (20d), which is located at such an angle with respect to the light rays (4; 41) coming from the first surface (20c) to it reflects substantially all light rays coming toward it at an approximately 90 degree angle in relation to the direction of arrival. Lightning assembly (1) according to any preceding claim, characterized in that over 60%, preferably over 80% of the light source (3) light falls on the rectangular or square area (5; 50) to be illuminated. Flash assembly (1) according to any one of the preceding claims, characterized in that the alias optical inner surfaces (20) of the lens (2) are non-formed surfaces obtained by combining suitable polynomial curves. Flash unit (1) according to any preceding claim, characterized in that the lens (2) is part of the camera's outer housing. • * · • · * Lightning assembly (1) according to claim 9, characterized in that the lens (2) consists of the same material as the body of the photographic device which comprises:. makes the lens. * * * · «·· • · ** · * 11. Flash assembly (1) according to any preceding claim, characterized in that the general shape of the lens (2) is a rectangle or a square. • · • » Lightning assembly (1) according to any of the preceding claims, characterized in that the lens (3) is made by molding one or more plastic types. best. • w 35 Lightning assembly (1) according to claim 13, characterized in that the lens (3) is molded together with a frame surrounding the lens, as in combination with the housing of a mobile telephony. 15 1 1 7806 Use of a flash unit according to any preceding claim or a mobile telephony. 5 * · • · · · · · · · 1 · · · · 1 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·