Patent Application
20090296365
The present invention relates generally to coin collecting and valuation of coins, and more particularly, to a color-controlled source used to quantitatively evaluate the coins.
The interest in the collection and conservation of coins and related objects has been historically considered a personal interest activity, with little formal standards or controls concerning the trading of coins. The recent rise in the value of coins compared to earlier levels has promoted the trading of coins to a higher degree of professional structure, most significantly by the advent of commercial third party coin grading services who have developed systems to apply a widely accepted quality grade (based on a numerical scale from 1 to 70 with 70 being the highest quality). After examining and determining the grade of a coin, the commercial services place the coin in a clear plastic holder in which a grade label with a reference barcode is affixed. The clear plastic holder is then ultrasonically welded around the coin, thus permanently linking the grade to the coin within the case. A barcode is linked to the database which can be searched to confirm that the referenced coin was graded by the commercial service, along with some additional transaction details such as the date, place, person grading the coin, etc.
The grading service charges a fee for the provided services and gives a warranty of grading accuracy as part of the transaction value. The result of this commercial service is to allow the plastic encapsulated coins to be more readily traded as their trade value is directly linked to the professional quality grade on the plastic holder.
However, the current commercial grading services can lack repeatability and consistency. Further, current services are unable to prevent “grader shopping” in which a coin owner may specifically hunt for the highest value for a given coin by removing the coin from the plastic holder and re-submitting it since there is currently not a mean to identify a specific coin outside of the labeled box or other rigorous objective means for identifying a specific coin.
Moreover, coin grades are frequently influenced by color or tonality of the coin surfaces. These parameters can have a significant effect on a valuation level of a coin. However, imaging a coin using an improper or non-repeatable light source can either intentionally or unintentionally significantly alter the color or tonality of the coin when creating a reference coin image. Therefore, an improved illumination source is needed for coin imaging systems.
In addition to coin grading, with the increasing use of on-line cataloging, internet sales and auctions, and other electronic media to exchange coins, the use of digital images for the cataloging and valuing of coins is becoming increasingly important. However there are a number of challenges for the illumination of coins. The coins are made of differing material which cause a variation in reflectivity and scattering. An improved illumination source is needed for the proper imaging of coins.
In various exemplary embodiments, a coin illumination source is disclosed. In one embodiment the coin illumination source comprises a geometric feature configured to surround a coin under evaluation, a plurality of illumination sources mounted on an outer portion of the geometric feature, and a viewing aperture located on the feature and configured to capture an image of the coin.
The appended drawing illustrates an exemplary embodiment of the present invention and must not be considered as limiting its scope.
With reference to
The viewing aperture 105 may be used to house, for example, a digital lens imaging system once a required color-temperature or range of temperatures is established within the translucent hemisphere 101. The viewing aperture 105 may also be used to determine or set a specified illumination level or color-temperature prior to imaging the coin set on the plate 103 inside the translucent hemisphere 101. Intensity level measurements of light are well-known in the art. Other illumination and color balancing techniques are described, below.
In an exemplary embodiment, each of the plurality of illumination sources 107 may individually be controlled for an overall intensity level. Further, shadowing effects may be achieved by varying an intensity level from one side of the translucent hemisphere 101 to another. Depending upon the source chosen, the plurality of illumination sources 107 may individually be controlled for color-temperature or wavelength as well. In all cases however, all variations can be measured and recorded to provide repeatable and consistent configurations.
Color-control may be obtained in a variety of ways. For example, a color meter (e.g., a Konica-Minolta CR-400 Chroma Colorimeter manufactured by Konica-Minolta Sensing Americas, Inc., 101 Williams Drive Ramsey, N.J. 07446 USA) may be used to record and achieve a specific color balance. Frequently, a 5500° K (Kelvin) to 7000° K color-temperature measurement emulates typical daylight illumination. In some cases, a ultraviolet or near-infrared (near-IR) wavelength may be needed. Overall, there are several ways to vary color-balance.
Using a tri-color light source enables the user to change the color balance. For example, three light emitting diodes containing the three primary colors of red, green, and blue (RGB) may be coupled at each location of the plurality of illumination sources 107 to obtain a tri-color light source. A drive current to each color of LED will control the intensity of a given LED and hence, the overall color balance. Thus, the drive current to one or two of the colors may be controlled to achieve a particular color-temperature as noted by the color meter.
Optionally, an output of a color sensor placed within the viewing aperture 105 may be changed to achieve a preferred color temperature. For example, individual RGB outputs from a color CMOS sensor or CCD array can be tuned individually to achieve the preferred color-temperature regardless of the light source being used. (The light source needs, of course, at least some level of continuous color spectrum in the visible range. A single-temperature source (e.g., a sodium vapor lamp) can not be adjusted to other than its narrow-band color output level.)
In yet another option, a combination of light sources and color sensor output levels may both be adjusted. Further, since a variety of ways exist to establish a given color-temperature or wavelength, the translucent hemisphere 101 need not be completely uniform in either optical density or color.
In another exemplary embodiment in which color balance is unnecessary, the plurality of illumination sources 107 may be comprised of sources with a known or well-defined output.
For example, photographic flash heads are generally specified as having a known color-temperature, typically 5500° K to 6500° K. In this case, a user of the hemispherical coin illumination apparatus 100 may only be concerned with relative or absolute intensity levels between the plurality of illumination sources 107. Optionally, additional diffusers (not shown) can be utilized with any of the illumination arrangements described.
In another example, the color-temperature may be chosen to have a narrow-band output to view features of a coin other than tonality such as defects that are noticeable only when irradiated by particular wavelengths. For instance, a near-infrared (near-IR) laser (e.g., lasing at 810 nm) may be useful under such conditions. The colorimeter may still be inserted through the viewing aperture to determine the illumination bandwidth.
In yet another example, a broadband source may be used directly or with filtering mechanisms to achieve a given color-temperature. The filtering mechanism may be an optical subtractive filter or a more complex mechanism, such as a monochromator, known in the art. The broadband source may be coupled to the outer portion of the translucent hemisphere by, for example, fiber optic strands or bundles.
In another exemplary embodiment (not shown directly but readily envisioned by reference to
Another embodiment is illustrated in
The LED bank may include a number of different colored lights or lights of all one color, such as white LEDS, and some variation in angle of the lights. For example, LEDs 525, 526 may include white, yellow, blue, red, multicolor or other color selection. A user or automatic control could allow for optimal illumination of the coin. Some coins which are highly reflective may not photograph well using illumination from above. For example, newly minted silver coins have a highly reflective surface, making imaging of the surface features of the coin difficult. The lower bank of lights would allow for less direct light, which could be angled onto the coin, or scattered onto the coin.
In taking an image of the coin an automated process allows selection of the suitable illumination. This is shown with respect to
The present invention is described above with reference to specific embodiments thereof. It will, however, be evident to a skilled artisan that various modifications and changes can be made thereto without departing from the broader spirit and scope of the present invention as set forth in the appended claims. For example, particular embodiments describe techniques for measuring color-temperature with a removable colorimeter. A skilled artisan will recognize that other colorimeter types exist and may be permanently affixed to measure within the translucent hemisphere. Further, each system, once initially constructed and calibrated, may include a small reference sample, such as an 18% gray-scale reflector, to readily recalibrate the system. In certain situations, calibrating either sensors or tri-color LED arrangements to have a similar electrical output may also provide consistent color-temperatures. Also, the translucent hemisphere can take other forms as well such as a cylinder, enclosed rectangle, or other substantially-closed geometric feature. Moreover, although shown as substantially orthogonal to the plate, the viewing aperture may be located at various positions on the hemisphere to best facilitate photographing or otherwise taking measurements from a coin. These and various other embodiments are all within a scope of the present invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.
The present invention claims priority from provisional application Ser. No. 61/046,344, filed Apr. 18, 2008.
| Number | Date | Country | |
|---|---|---|---|
| 61046344 | Apr 2008 | US |
