[DESCRIPTION]

[Invention Title]

LENZ ASSEMBLY FOR ADJUSTING WHITE BALANCE FOR CAMERA

[Technical Field]

The present invention relates to a lens assembly for adjusting the white balance of a camera, and more particularly to a lens assembly for adjusting the white balance of a digital camera which enables the white balance of a digital camera to be conveniently and precisely adjusted.

[Background Art]

As is generally known in the art, cameras serving as photographing devices are categorized as film cameras or digital cameras depending upon whether a medium on which a photographed image is stored comprises film or an electronic storage medium such as a CCD (charge coupled device) and a CMOS (complementary metal oxide semiconductor). Also, cameras are categorized as still cameras or moving picture cameras depending upon whether the cameras have a moving picture photographing function. Hereinafter, the term 'camera' will be used to include both still cameras and moving picture cameras.

Most digital cameras have a white balance adjustment function. White balance is a feature which allows a digital camera to be appropriately adjusted so as to recognize true white as white when photographing an object based on whiteness. More concretely described, a light source has a peculiar color which is called a color temperature and is expressed in degrees Kelvin (° K). In the case of a human, when a scene such as a landscape is illuminated by a light source having a certain color temperature, since humans can automatically adjust their perception, a difference in the perception of color does not occur. However, in the case of a camera, since color temperature is superimposed on an inherent color, the color sensibility is greatly influenced by the light source. For example, sunlight has a high color temperature in the middle of a sunny day and is perceived as blue, whereas it has a low color temperature at sunrise and sundown and is perceived as red. In this example, if photographing is conducted without

taking any measures, due to change in color temperature of the light source, the color of the resultant image varies from blue to red.

In order to compensate for this problem, for the most part, the current digital cameras are configured in a manner such that a user can select a color temperature corresponding to one of various situations such as sunlight, cloudiness, an incandescent lamp, a fluorescent lamp and shade. The digital cameras also have an automatic white balance adjustment function for automatically adjusting white balance using a sensor even when the selection of a color temperature is not made. Further, professional digital cameras have a function allowing a user to directly select a desired color temperature as a numerical value. However, in most cases, the circumstances under which human beings lead everyday life do not have a single light source. For example, in the case of a room, it is conceivable that a fluorescent lamp is turned on, an incandescent lamp is also turned on, and a small amount of sunlight streams into the room through a window. Therefore, since the room has complex light sources, it is actually difficult to precisely determine the color temperature.

In consideration of this fact, most digital cameras have a custom white balance function which is well known as a 'preset mode ¹ . The custom white balance function allows the reference of white for a camera to be set under a photographing situation having various light sources and an R/G/B (red/green/blue) color balance process to be conducted based on the reference of white for a camera. A custom white balance process is generally conducted in a manner such that exposure is measured on the gray surface of a gray card, and the white surface of a white card is photographed so that the resultant color temperature is established as a preset value for the camera.

[Disclosure]

[Technical Problem]

However, even in this case, since the white card is made of paper (pulp) and the kinds of white and gray are various, it is actually impossible to precisely adjust the white balance. Moreover, because the white card or

gray card does not have any object (a focus object) to be focused by the camera lens, an 'automatic focus' mode, recognized as one of the functions for enabling quick photographing of the digital camera, cannot be used. Therefore, it is necessary to switch from the 'automatic focus' mode to a 'manual focus' mode, adjust the white balance and then switch again from the 'manual focus' mode to the 'automatic focus' mode to enabling photographing. This procedure is inconvenient and cumbersome and requires substantial time, therefore it is impossible to be immediately ready for an urgent opportunity.

[Technical Solution]

Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a lens assembly for adjusting the white balance of a camera which is constructed to be carried so that the lens assembly can be used in place of the conventional white card or gray card when a user adjusts the custom white balance of a digital camera, to enable the white balance to be precisely adjusted under any light source.

Another object of the present invention is to provide a lens assembly for adjusting the white balance of a camera which is constructed to enable focusing to be conducted even under an automatic focus mode so that it is not necessary to change a photographing mode to a manual focus mode when adjusting the custom white balance of a digital camera.

[Advantageous Effects]

According to the features of the lens assembly for adjusting the white balance of a camera according to the present invention, since the lens assembly is constructed to be easily carried, the custom white balance of various digital cameras can be quickly and precisely adjusted so that it is possible to precisely photograph and store important moments using digital cameras .

Further, since the custom white balance can be adjusted even under the automatic focus mode, inconvenience, which is otherwise encountered when switching a focus mode to adjust white balance, is eliminated, and the time

required for changing the focus mode can be decreased, whereby the ability to spontaneously take photographs is increased. [Description of Drawings]

FIGs. Ia and Ib are front and side views illustrating a lens assembly for adjusting the white balance of a camera in accordance with an embodiment of the present invention;

FIG. 2 is an exploded perspective view illustrating the lens assembly for adjusting the white balance of a camera shown in FIG. 1;

FIG. 3 is a cross-sectional view taken along the center portion of the lens assembly shown in FIG. 1;

FIGs. 4a and 4b are front and side views illustrating a lens assembly for adjusting the white balance of a camera in accordance with another embodiment of the present invention; and

FIGs. 5a and 5b are front and side views illustrating a lens assembly for adjusting the white balance of a camera in accordance with still another embodiment of the present invention. description of Reference Numerals for Main Parts on Drawings> 100, 100', 100": lens assembly 110, 110', 110": lens frame 112, 112', 112": circular rim 112a: circular inclined part 112b: circular shoulder for condenser lens 112c: circular shoulder for mixing board 112d: circular shoulder for fastening cap 114, 114', 114": hanger section 114a, 114a', 114a' ¹ : suspension slot

120: condenser lens 122: convex center part

124: flat peripheral part 130: mixing board 132, 132', 132": circular projection peripheral part 134, 134', 134": holed center part 134a, 134a', 134a": center hole 140: reflection sheet 150: rear cap [Best Mode]

In order to achieve the above objects, a lens assembly for adjusting the white balance of a camera according to the present invention comprises a lens frame! a mixing board formed in the shape of a plate, secured to the lens frame, and having a holed center part in which a plurality of holes having predetermined shapes are defined into a predetermined pattern to mix light externally incident thereon and to output mixed light! and a reflection sheet placed below the holed center part. [Mode for Invention]

Hereafter, a lens assembly for adjusting the white balance of a camera in accordance with a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

FIGs. Ia and Ib are front and side views illustrating a lens assembly for adjusting the white balance of a camera in accordance with an embodiment of the present invention, FIG. 2 is an exploded perspective view illustrating the lens assembly for adjusting the white balance of a camera shown in FIG. 1, and FIG. 3 is a cross-sectional view taken along the center portion of the lens assembly shown in FIG. 1. FIGs. 1 through 3 illustrate a lens assembly for adjusting the white balance of a digital camera which has a relatively medium-sized lens diameter, for example, about 85 mm. As shown in FIGs. 1 through 3, the lens assembly 100 for adjusting the white balance of a camera (hereinafter, simply referred to as a "lens assembly") according to this embodiment of the present invention comprises a lens frame 110 composed of a circular rim 112 which has a relatively medium-sized diameter of about 85 mm, and a plurality of lens component parts sequentially stacked in multiple layers in the thickness-wise direction of the circular rim 112.

In the above-described construction, a plurality of circular shoulders 112b, 112c and 112d are formed in the shape of a step in the thickness-wise direction of the circular rim 112. The circular shoulders 112b, 112c and 112d are brought into contact with lens component parts to prevent the lens component parts from moving. It is preferable that the lens frame 110 have a color of black, which renders a warm feeling, or gray, which renders a

somewhat hard feeling. In the drawings, the unexplained reference numeral 114 designates a hanger section which projects parallel outward of the circular rim 112 to ensure easy carrying and handling of the lens assembly 100, and 114a designates a suspension slot which is defined in the hanger section 114 to allow a suspension cord, etc. to be inserted or tied therein.

Next, the lens component parts include a condenser lens 120, a mixing board 130, and a reflection sheet 140. The condenser lens 120 has a circular plate-shaped configuration. The condenser lens 120 is secured to the circular shoulder 112b for the condenser lens, which is formed at the top in the thickness-wise direction of the circular rim 112, to focus light reflected from the reflection sheet 140 and the mixing board 130 both of which will be described below. The mixing board 130 also has a circular plate-shaped configuration. The mixing board 130 is secured to the circular shoulder 112c for the mixing board, which is formed directly below the circular shoulder 112b for the condenser lens at a predetermined separation from the circular shoulder 112b for the condenser lens, to appropriately mix and adjust light externally incident thereon. The reflection sheet 140 is disposed below the mixing board 130. In this construction, the condenser lens 120 may be formed of transparent glass or synthetic resin. The synthetic resin may comprise polycarbonate. Further, it is preferable that a particular part of the condenser lens 120, having a predetermined radius when measured from the center of the condenser lens 120, be formed to be convex in order to improve concentration efficiency. Hereinafter, the convex part of the condenser lens 120 is referred to as a convex center part 122, and the flat part around the convex center part 122 is referred to as a flat peripheral part 124.

The mixing board 130 is composed of a holed center part 134 and a circular projection peripheral part 132. In the holed center part 134, a plurality of holes having appropriate sizes and shapes are defined at the center portion of the circular plate while forming appropriate angles with respect to one another. On the circular projection peripheral part 132, a

plurality of circular projections, each having a triangular cross-sectional shape, are formed around the holed center part 134. Synthetic resin may be used as the material of the mixing board 130. It is preferred that the mixing board 130 have a color of pearl gray, which has a brightness corresponding to an intermediate level between a white card and a gray card.

Due to the fact that the holed center part 134 has the plurality of holes, the holed center part 134 can perform a function of adjusting direct and indirect light. The holed center part 134 can comprise a center hole 134a which is defined, for example, at the very center of the holed center part 134 to have a predetermined diameter, a plurality of triangular holes which are located to diverge from the center hole 134a, openings which are defined by cutting a circle into pieces, rectangular slits, and so forth. The center hole 134a may function to provide a focal point for the camera lens when adjusting the color temperature. The holed center part 134 of the mixing board 130 according to this embodiment of the present invention has a total of 21 holes. Each of the circular projections of the circular projection peripheral part 132 has a triangular sectional shape to perform a function of adjusting the polarization of light. The reflectance of the circular projection peripheral part 132 varies depending upon the number of the circular projections, the vertical angle of each circular projection, the height of the crest and depth of the valley of the circular projection, etc. In this embodiment, the number of circular projections is set at 5.

The reflection sheet 140 is installed below the holed center part 134 of the mixing board 130 to perform a function of reflecting light which is incident through the holed center part 134. The reflection sheet 140 may be formed by processing polycarbonate resin with silver or by applying paint having high reflectance to the resin. At this time, since no holes are defined in the circular projection peripheral part 132, it is preferred that the reflection sheet 140 have a size capable of covering only the holed center part 134.

In the drawings, unexplained reference numeral 150 designates a

protective cap for preventing the mixing board 130 and the reflection sheet 140 from being released or damaged. The protective cap 150 is secured to the circular shoulder 112d for the protective cap, which is formed at the bottom in the thickness-wise direction of the circular rim 112. The condenser lens 120, the mixing board 130 and the protective cap 150 can be secured to their respective circular shoulders 112b, 112c and 112d through ultrasonic fusion, etc. Preferably, in order to ensure that the convex center part 122 does not come into direct contact with a flat support surface when the lens assembly 100 of the present invention is placed on the flat support surface, the corresponding portion of the circular rim 112 is formed to have a thickness which is greater than that of the convex center part 122 of the condenser lens 120. In this case, it is preferred that the corresponding portion 112a (hereinafter, referred to as a "circular inclined part") of the circular rim 112 be inclined to be diverged toward the upper end of the circular rim 112.

FIGs. 4a and 4b are front and side views illustrating a lens assembly for adjusting the white balance of a camera in accordance with another embodiment of the present invention. FIGs. 4a and 4b illustrate a lens assembly for adjusting the white balance of a digital camera which has a relatively large-sized lens diameter, for example, about 110 mm. As shown in FIGs. 4a and 4b, in the lens assembly 100' according to this embodiment of the present invention, as the lens diameter increases, the component parts of the lens assembly 100' are enlarged when compared to those of the embodiment shown in FIG. 1. The lens assembly 100' is constructed in the same way as the embodiment shown in FIG. 1, with the exception that the lens frame 110' has a color of pearl gray, and the size, number (33 in this embodiment), shape, arrangement pattern, angle, etc. of the holes that constitute the holed center part 134' of a mixing board 130' are different. In the drawings, the unexplained numerals 114' and 114a' respectively designate a hanger section and a suspension slot, 132' a circular projection peripheral part, 134a' a center hole, and 112' a circular rim.

FIGs. 5a and 5b are front and side views illustrating a lens assembly

for adjusting the white balance of a camera in accordance with still another embodiment of the present invention. FIGs. 5a and 5b illustrate a lens assembly for adjusting the white balance of a digital camera which has a relatively small-sized lens diameter, for example, about 65 mm. As shown in FIGs. 5a and 5b, in the lens assembly 100" according to this embodiment of the present invention, as the lens diameter decreases, the component parts of the lens assembly 100" are miniaturized when compared to those of the embodiment shown in FIG. 1. The lens assembly 100" is constructed in the same way as the embodiment shown in FIG. 1 with the exception that the size, number (17 in this embodiment), shape, arrangement pattern, angle, etc. of the holes that constitute the holed center part 134" of a mixing board 130" and the number (3 in this embodiment) of the triangular circular projections on a circular projection peripheral part 132" are different. In the drawings, the unexplained numerals 114" and 114a" respectively designate a hanger section and a suspension slot, 134a" a center hole, and 112" a circular rim.

When it is necessary to adjust white balance using the lens assembly 100, 100' or 100" according to the present invention, constructed as mentioned above, the lens assembly 100, 100' or 100" is grasped with one hand so that light can reach the condenser lens thereof. Then, a focusing operation is conducted using the other hand in a state wherein a digital camera, the white balance mode of which is set to a preset mode, is separated from the lens assembly 100, 100' or 100" by a predetermined distance, for example, 5 to 10 cm. In this case, even when the focus mode of the digital camera is set to an automatic focus mode, the lens assembly 100, 100' or 100" of the present invention can be focused due to the fact that the holed center part 134, 134' or 134" and the circular projection peripheral part 132, 132' or 132" of the mixing board 130, 130' or 130" form a shape. In this case, as described above, the holed center part 134, 134' or 134" of the mixing board 130, 130' or 130" functions to appropriately adjust the angle of light polarization. The light which is reflected and adjusted in the holed center

part 134, 134' or 134" and the circular projection peripheral part 132, 132' or 132" is condensed by the convex center part of the condenser lens and is incident on the digital camera to be then used in adjusting the white balance. At this time, the lens assembly having a large diameter can be used for a digital camera having a small lens diameter.

Although preferred embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claim. For example, even though efficiency and precision may be deteriorated somewhat, the condenser lens or the convex center part of the condenser lens may be removed, or the circularly projecting peripheral part of the mixing board may be removed.