COLOR-PICTURE ANALYZING APPARATUS WITH RED-PURPOSE AND GREEN-PURPOSE FILTERS

Abstract: A color-picture reading apparatus comprises blue, red-­ pupose, green-purpose fluorescent lamps, a red filter in front of the red-purpose lamp for solely the red radiation, a green filter in front of the green-purpose lamp for solely passing the green radiation, and a circuit for subsequently switching on and off the three lamps. Both the red filter and the green filter comprise a first filter for cutting the short wavelength radiation and a second filter for cutting the long wavelenth radiation. The first filter is a glass filter and the second filter is an interference filter. All of the three lamps have a short afterglow time.

Description: The present invention relates to a color-picture analyzing apparatus comprising first lamp means for propagating blue spectral radiation toward said color-picture ; second lamp means for directing spectral radiation inclusive of red radiation toward said color-picture ; third lamp means for directing spectral radiation inclusive of green radiation toward said color-picture ; and, means for subsequently switching on and off said three lamp means. Such color-picture analyzing apparatus is described for example in JP-A-55-30214. Conventionally, a color-picture analyzing apparatus is provided in a color facsimile machine, color copying machine, and color scanner for analyzing the color-picture into the red component, green component, and blue component by optically scanning the color-picture, so that they are electrically converted and outputted. To analyze the red, green, and blue components from the color-picture, various types of filters are presented through which reflected radiations from the color-picture are passed to pick-up picture information for a specific wavelength zone. Some conventional blue fluorescent lamp can respond speedy and has a short afterglow time while the conventional red and green fluorescent lamps inevitably have relatively long afterglow times (several-about 10 msec). It may, therefore, be difficult to provide a superior reading apparatus for rapidly analyzing the color-picture. Accordingly, it is an object of the present invention to provide an improved color-picture analyzing apparatus for analyzing a color-picture rapidly. It is another object of the present invention to provide an improved color-picture analyzing apparatus suitable for a color facsimile machine, color copying machine, and color scanner for analyzing a color-picture, featured in that each of blue, red-purpose, and green-purpose fluorescent lamps has a short afterglow time. It is a further object of the present invention to provide an improved color-picture reading apparatus for analizing a color-picture by sequentially switching on blue, red-purpose, and green-purpose fluorescent lamps, red-purpose and green-purpose fluorescent lamps being faced by filter meas comprising a first filter for cutting the short wavelength radiation and a second filter for cutting the long wavelength radiation. In accordance with the present invention, the color-picture analyzing apparatus is characterized in that it further comprises : red filter means for solely passing the red radiation, said red filter means being positioned between the second lamp means and the color-picture, said red filter means comprising a first glass filter for cutting the short wavelength radiation and a first interference filter for cutting the long wavelength radiation ; and, green filter means for solely passing the green radiation, said green filter means being positioned between the third lamp means and the color-picture, said green filter means comprising a second glass filter for cutting the short wavelength radiation and a second interference filter for cutting the long wavelength radiation. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein: FIG. 1 is a side view of a color-picture reading apparatus according to the present invention; FIG. 2 is a sectional view of a filter for red and green according to the present invention; FIGS. 3(1) and 3(2) are a graph showing a distribution of emission energy of a blue fluorescent lamp and a red- and green-purpose fluorescent lamp, respectively, used for the present invention; FIG. 4 is a graph showing spectral characteristics of an infrared-cut filter used for the present invention; FIGS. 5(1) through 5(3) are graphs showing the spectral characterostics of an interference filter against blue, green, and red, respectively; FIG. 6(1) is a graph showing the spectral characteristics of a glass filter, FIG. 6(2) shows those of an interference filter, and FIG. 6(3) shows those of a green filter according to the present invention; and FIG. 7(1) is a graph showing the spectral characteristics of a glass filter, FIG. 7(2) shows those of an interference filter, and FIG. 7(3) shows those of a red filter according to the present invention. DESCRIPTION OF THE INVENTION FIG. 1 is a side view of a color-picture reading apparatus of the present invention. It is applicable to a color facsimile, color copying machine, and color scanner. With reference to FIG. 1, a document 1 having thereon a color-picture to be readout is transported along the direction of the arrow by transport means (not shown). To emit light toward the document 1, three light emitting sources 2A, 2B, and 2C are provided. A first source 2A is a blue fluorescent lamp for providing blue spectral radiations characterized in that the emission energy of FIG. 3(1) with a short afterglow time is provided. The term "afterglow time" is referred to as the interval when the lamp continues to propagate some radiation after the power supply to itself has been shut off. During the afterglow time, the spectral characteristics of all the fluorescent lamps as used for the present invention is unchanged although its emission level is relatively small. For the present invention, both second and third fluorescent lamps 2B and 2C propagate the spectral emission energy as shown in FIG. 3(2). In FIG. 3(2), the data as plotted in the solid line relate to the green-purpose flurorescent lamp while the data in the broken line relate to the red-purpose lamp. These lamps can be called cool white fluorescent lamps although not limited to the cool white type so long as each of them can cover the red or green spectral zone. They comprise fluorescent materials to cover the emission over the wide range with a short afterglow time. The second lamp 2B has an emission band sufficient to cover the red zone. For example, such a lamp may comprise a fluorescent material of trade name "SPD-103A", available fron Toshiba Corporation, Japan. The "SPD-103A" can provide a short afterglow time of about 10 micro sec. The lamp 2C has an emission band sufficient to cover the green zone. For example, such a lamp may comprise mixed components of trade name "SPD-11N" by Toshiba Corporation and "SPD-103A". Since the "SPD-11N" can provide a short afterglow time of about 2 micro sec, the mixed material can provide an afterglow time in the same order. Thus, the afterglow time of each lamp is sufficiently short. In front of the lamps 2B and 2C, a red filter 3 and a green filter 4 are positioned. The red filter 3 is composed of a glass filter 3A for cutting short wavelength waves and an interference filter 3B for cutting long wavelength waves. The green filter 4 consists of a glass filter 4A and an interference filter 4B, too. The construction of each filter 3 or 4 is indicated in FIG. 2. Preferably, the glass filter 3A (4A) and the interference filter 3B (4B) are integrally overlayed. It may be possible that they are separated from each other. First, light is emitted from the lamps 2A, 2B, and 2C, and reflected by the document 1, so that the reflected light is further reflected by a reflection mirror 5 and is incident upon a reading lens 7 via an infrared-cut filter 6. The light passing through the lens 7 is incident upon a charge coupled device (CCD) image sensor 8. The image sensor 8 can provide signals corresponding to the reflected light into a processing circuit 9. The processing circuit 9 outputs signals for red components SR, green components SG, and blue components SB. FIG. 4 shows the spectral characteristics of the infrared-cut filter 6 which is only exemplary although not limited to such an example. Regarding the red filter 3 and the green filter 4, they may be replaced by a filter comprising a single material, solely, selected from a gelatin filter, a glass filter, and an inteference filter. However, such a single filter has inferior characteristics. The gelatin filter cannot provide a good transmission factor and is weak to heat. The glass filter cannot provide a good transmission factor. Although the interference filter can provide a good transmission factor, its spectral characteristics can be great changed depending on a change in the incident angle of light incident upon itself. FIGS. 5(1), 5(2), and 5(3) show graphs representing the spectral characteristics of the interference filter with the blue, green, and red radiation, respectively. These graphs indicate that when the incident angle is oblique, for example, 45 degrees, the spectral transmission zone can be shifted toward the short wavelength zone while a small transmission zone starts to appear at the long wavelength zone. According to the present invention, to eliminate the above problem, each of the red filter 3 and the green filter 4 is provided. They may comprise an overlay structure of a glass filter and an interference filter. FIG. 6(1) is a graph representing the spectral characteristics of the glass filter 4A of the green filter 4 for cutting the short wevelength. As shown, even when the incident angle of the light becomes oblique, the spectral transmission zone cannot be shifted although the spectral characteristics become small as compared with the case of the incident angle of 90 degrees. FIG. 6 (2) shows a graph indicative of the spectral characteristics of the interference filter 4B for cutting the long wavelength waves to serve as the green filter 4. As shown, when the incident angle of the light becomes oblique, the spectral transmission zone may be shifted toward the short wavelength zone. However, these effects can be cut out by the characteristics of the glass filter 4A. The spectral transmission zone at the long wavelength can be cut out by infrared-cut filter 6. Thus, the green filter 4 can provide the spectral characteristics as shown in FIG. 6 (3) which is a combination of the glass filter 4A having the characteristics of FIG. 6 (1) and the interference filter 4B having the characteristics of FIG. 6 (2). The green filter 4 is characterized in that the spectral characteristics can be changed relatively over its transmission factor even when the light is obliquely incident. In combination with the lamp 2C having a short afterglow time, the green filter 4 provides good green spectral radiations. FIG. 7 (1) shows a graph of the spectral characteristics of the glass filter 3A for the red filter 3. FIG. 7 (2) shows a graph of the spectral characteristics of the interference filter 3B of the filter 3. FIG. 7 (3) shows a graph of the spectral characteristics of the red filter 3 as composed with those of the glass filter 3A and the interference filter 3B. As shown, because the red filter 3 is featured in that the spectral transmission band cannot be shifted depending upon the changes in the incident angles of the light, the red filter 3 and the lamp 2B having a short afterglow time can provide the good red spectral emission. In operation, first, the lamp 2A is switched on so that the reflected light can be incident upon the CCD image sensor 8, the refleted light corresponding to the spectral emission characteristics of the lamp 2A. The CCD sensor 8 provides the signals corresponding to the reflected light into the processing circuit 9. After the processing, the processing circuit 9 outputs the blue components SB. Second, while the lamp 2A is switched off, the lamp 2B is started to be switched on so that the processing circuit 9 provides the red components SR. Last, while the lamp 2B is switched off, the lamp 2C is started to be switched on. The circuit 9 provides the green components SG. Thereafter, the document 1 is transported along the arrow direction in a predetermined distance. The above operations are repeated to subsequently analyze the color-pictures. In addition to the blue fluorescent lamp having a short afterglow time, according to the present invention, because good light emitting sources for red and green can be provided by the filters 3 and 4 in combination with the short afterglow time fluorescent lamps, the switching on and off of the lamps can be accelerated to make it possible to rapidly analyze the blue, green, and red components. In the embodiment of FIG. 1, the infrared-cut filter 6 is provided. To eliminate the filter 6, alternatively, the reflected mirror should serve to cut the infrared radiation by comprising a filter named "cold filter". While only certain embodiments of the present invention have been described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the present invention as claimed.

Claims: A color-picture analyzing apparatus comprising : first lamp means (2A) for propagating blue spectral radiation toward said color-picture (1) ; second lamp means (2B) for directing spectral radiation inclusive red radiation toward said color-picture ; third lamp means (2C) for directing spectral radiation inclusive of green radiation toward said color-picture ; and, characterized in that it further comprises : red filter means (3) for solely passing the red radiation, said red filter means being positioned between the second lamp means (2B) and the color picture (1), said red filter means comprising a first glass filter (3A) for cutting the short wavelength radiation and a first interference filter (3B) for cutting the long wavelength radiation ; and, green filter means (4) for solely passing the green radiation, said green filter means being positioned between the third lamp means (2C) and the color picture (1), said green filter means comprising a second glass filter (4A) for cutting the short wavelength radiation and a second interference filter (4B) for cutting the long wavelength radiation. The apparatus of claim 1, wherein each of said first, second and third lamp means (2A, 2B, 2C) has a short afterglow time. The apparatus of claim 2, wherein one of said second and third lamp means (2B, 2C) is a fluorescent lamp. The apparatus of claim 3, wherein the fluorescent lamp (2B, 2C) is of a cool white type. The apparatus of claim 1, wherein the red and green filter means (3, 4) each provide a spectral transmission waveband which is independent of the incident angle of the radiation emitted from the second and third lamp means (2B, 2C).

Inventors: NAGANO, FUMIKAZU
Applicants: SHARP KABUSHIKI KAISHA
Application year: 1985
Main classification: G01J3
IPC codes: H04N1, G01J3