Image reading device for photographic printing

Abstract: An image reading device for photographic printing comprising an optical lens mechanism, a monochrome CCD image device arranged at a focal position on an optical axis of the optical lens mechanism, a filter rotation plate having a plurality of color filters rotatably arranged on the optical axis, and a cut filter for blocking unnecessary light arranged on the optical axis, wherein a light quantity correction means for obtaining stepwise spectral characteristics is arranged on the optical axis. The reflected light due to the conventional ND coating and the influences of the boundary plane and the parallel degree between the cut filter and the color filter are disappeared, whereby the occurrence of flare, ghost and color divergence can be prevented.

Description: The present invention relates to an image reading device for photographic printing in a photo-processing apparatus. More particularly, the present invention relates to an image reading device for photographic printing for reading the color image stored in the film by the CCD image element. In the printing device for printing the color image stored in the developed film onto a photosensitive material, there is used an image reading device for photographic printing for reading the color image. As this image reading device for photographic printing, there are two kinds of devices, the one using the color CCD image element (hereinafter referred to as "color CCD") and the other using the monochrome CCD color element (hereinafter referred to as "monochrome CCD") to convert it to the color image by the color filter (spectral filter). The device using the color CCD is generally not used because the spectral characteristics do not match with the sensitive material (paper sensitivity) in the photo devices (printer). On the contrary, the device using the monochrome CCD is, as shown in Fig. 9 and Fig. 10, composed of an optical lens mechanism 101 comprising a zoom lens arranged opposite to the film; a filter rotation disk 102 having color filters, a blue filter B, a green filter G and a red filter R, coaxially in the peripheral direction thereof; and a monochrome CCD 103. Since the light voltage of the respective filters B, G and R is strong in the order of filters R, G and B, the light quantity of the respective filters B, G and R is balanced by applying a dark ND coating to the filter R to restrict the transmitting light quantity and a ND coating thinner than that to the filter G, with making the light voltage of the filter B to be a reference. Thus, the device using the monochrome CCD has been generally used, since it can obtain the necessary spectral characteristics freely by combining color filters. However, since the film of the ND coating becomes a strong reflection surface, the reflected light on the surface of the monochrome CCD 103 is sometimes reflected by the film of the ND coating to be incident over the monochrome CCD 103. In such a case, there is the problem that a phenomenon to degrade the contrast of the imaging plane of the monochrome CCD 103 (hereinafter referred to as a "flare") tends to be caused. There is further the problem that the light reflected several times on the surface of the zoom lens reaches the film surface to generate an image being out of focus other than the regular image (hereinafter referred to as a "ghost") tends to be generated. Furthermore, since cut filters 104 for removing the ultraviolet rays and infrared rays are stuck to the color filters B, G and R, other than respective spectral transmission films, the boundary plane to be stuck is likely to be the reflection surface, and the parallel degree of the stuck two filters is deteriorated due to the error of adhesive precision, so that the parallel degrees of respective filters B, G and R against the monochrome CCD 103 becomes non-uniform, which causes the problem that a color divergence is likely to be caused. US Patent 4809198 describes a method for setting and managing photographic printing conditions of a photographic printing system, wherein monocolor red, green and blue light is generated, a recording material is exposed thereto, reference images with density steps are prepared, said densities of the three colour lights are measured, the measured densities are stored in a memory, amounts of exposure necessary for obtaining predetermined densities are determined, differences between said amounts of exposure and the reference amounts are obtained, and the amount of exposure for photographic printing is corrected in order to control the printing conditions. In US 4942424 there is disclosed a colour photographic printing method of printing a colour film on the basis of a value of a light measuring device having a spectral sensitivity distribution which coincides with or is similar to a spectral sensitivity distribution of colour paper layers sensitive to red, green and blue. The method comprises the steps of calculating the film characteristics of a film to be printed, comparing the film characteristics of a reference film with that of the film to be printed, and correcting the printing condition of the reference film according to the result of the comparing step as well as calculating the amount of exposure for printing. JP-A-05063894 describes a picture reader provided with a photo electric conversion means with plural line sensors arranged at a tilt with respect to the optical axis of a read optical system. The purpose is to reduce the capacitance of a delay element by correcting any of the distances between object images among the plural line sensors with chromatic aberration of an image forming lens. From JP-A-02150830 there is known a light measuring instrument for a photographic printer. For the tricolor separate light measurement, colour filters are put in a printing optical path. Respective points of the image of a photographic film, which are projected through the colour filters are measured by an image sensor through a ND filter. In JP-A-06250298 is a photographic printing/exposing controller. Its purpose is to adjust the exposure of each colour for an original image by means of the control of a colour filter and a shutter. The controller makes it unnecessary to use an optical shutter plate having special spectroscopic characteristics. The present invention has been completed under the above background and is defined by the appended claims 1-8. It is therefore a primary object of the present invention to provide an image reading device for photographic printing which can prevent the occurrence of the flare, ghost and color divergence and can obtain a clear color image. In accordance with the invention, there is provided an image reading device for photographic printing, comprising an optical lens mechanism, a monochrome CCD image device arranged at a focal position on an optical axis of the optical lens mechanism, a filter rotation plate having a plurality of color filters rotatably arranged on the optical axis, and a cut filter for blocking unnecessary light existing on the optical axis, characterized in that a light quantity correction means having a stepped spectral transmission filter characteristic over the spectral range of visible light is arranged on the optical axis. According to the image reading device for photographic printing of the invention, by arranging the light quantity correction means on the optical axis instead of the ND coating applied to the color filters G and R, and by synthesizing the light quantity correction means and the cut filter, the reflected light due to the ND coating and the influences of the boundary plane and the parallel degrees of the cut filter and the color filter disappear, whereby the occurrence of flare, ghost and color divergence can be prevented. Furthermore, by tilting at least one of the cut filters and the light quantity correction means against the optical axis, the reflected light from the image-sensing plane of the monochrome CCD is not reflected to be incident over the image-sensing plane, and thus flare, ghost and color divergence can be further prevented. Fig. 1 is a schematic view of a photographic printing device which uses an image reading device for photographic printing of the present invention; Fig. 2 is an elevational view showing one embodiment of the image reading device for photographic printing according to the invention; Fig. 3 is a left side view of the image reading device for photographic printing in Fig. 2; Fig. 4 is a spectral characteristic curve of the light quantity correction means in Fig. 2; Fig. 5 is an elevational view showing another embodiment of the light quantity correction means in Fig. 2; Fig. 6 is an elevational view showing another embodiment of the image reading device for photographic printing according to the invention; Fig. 7 is an elevational view showing still another embodiment of the image reading device for photographic printing; Fig. 8 is an elevational view showing yet another embodiment of the image reading device for photographic printing according to the invention; Fig. 9 is an elevational view showing the conventional image reading device for photographic printing; and Fig. 10 is a left side view of the image reading device for photographic printing in Fig. 9. Next, the image reading device for photographic printing of the present invention is explained based on the accompanying drawings. As shown in Fig. 1, the photographic printing device A which uses the image reading device for photographic printing of the present invention receives the light irradiated from a light source A1 via a mirror A2, reads the color image stored in the film F fed out from the negative mask N by the image reading device for the photographic printing, and, based on the read image information, performs printing to a photosensitive material P. As shown in Figs. 2 and 3, the image reading device for photographic printing 1 according to the invention comprises an optical lens mechanism 2, a monochrome CCD 3 arranged at a focal position of the optical axis L of the optical lens mechanism 2, a filter rotation plate (hereinafter referred to as "rotation plate") 5 having a plurality of color filters 4 rotatably arranged on the optical axis L, and a cut filter 6 for blocking unnecessary light existing on the optical axis L. The optical lens mechanism 2 is composed of, for example, a group of zoom lenses for enlarging the image stored in the film F. As the monochrome CCD 3, for example, an inter line type CCD solid-state image sensing device can be used, although this is not particularly limited in the present invention. The rotation plate 5 is in a disk-like form and the respective color filters 4 are housed in the rectangular holes 7 formed in the coaxial positions in the peripheral direction. The color filters 4 are a blue filter B, a green filter G and a red filter R in order. As the driving device of the rotation plate 5, there can be used known motors, for example, a stepping motor and the like. In addition, differing from the conventional filters G and R, the ND coating for restricting the amount of transmitting light is not applied to the filters G and R. The cut filter 6 is a filter to which a coating is applied to remove the ultraviolet rays and the infrared rays affecting the light quantity balance of the respective filters B, G and R. The image reading device for photographic printing according to the invention has the characteristic feature that a light quantity correction means S1 is arranged in front of the rotation plate 5 (on the right side of Fig. 1). The light quantity correction means S1 is, in the present embodiment, based in a front portion of the optical lens mechanism 2. This light quantity correction means S1 is arranged so that a stepped spectral characteristic can be obtained, as shown in Fig. 4, while different ND coatings are conventionally applied to the filters G and R, respectively, in order to obtain the sensitivity balance of the monochrome CCD by the respective filters B, G and R. Thereby, the necessary spectral sensitivity can be obtained as a whole. Namely, the light quantity correction means S1 is such a means that a plurality of metal oxide films which balance the light quantity of the filters B, G and R are combined to be coated on the surface of the color balance filter comprising a transparent glass to obtain the stepped spectral characteristic. Also, as the light quantity correction means S1, as shown in Fig. 5, a color balance mirror M for obtaining the stepwise reflective spectral characteristics as shown in Fig. 4 might be used on the optical axis L, instead of the mirror A2 shown in Fig. 1. On the surface of this color balance mirror M, the coating is applied by combining a plurality of metal oxide films as described above. By using the color balance mirror M, the constituent part can be made simpler than in the case where the color balance is taken by filters. In the present embodiment, flares can be reduced by arranging the light quantity correction means S1 in front of the optical lens mechanism 2. Furthermore, the light quantity correction means S1 is attached with being tilted by 5° or so against the optical axis L. Thereby, it can be prevented that the reflected light on the plane of the monochrome CCD 3 reflects again to enter into the CCD 3, whereby no ghost is caused. Incidentally, in the present invention, the tilt angle of the color balance filter is made to be 5°, but it is not limited thereto, and can be properly selected in the range of, for example, from 5 to 10°, according to the image sensing area. Moreover, the tilt direction is not particularly limited. Next, another embodiment of the image reading device for photographic printing according to the invention will be described. As shown in Fig. 6, the image reading device for photographic printing 11 has a light quantity correction means S2 different from the light quantity correction means S1 in the image reading device for photographic printing 1 in that the cut filter 6 and the light quantity correction means S1 are synthesized to make one filter. Namely, in the light quantity correction means S2 of the present embodiment, the coating to balance the light quantity of the respective filters B, G and R and the coating to remove the ultraviolet rays and infrared rays are applied on the back face and on the surface of one color balance filter 8, respectively. Moreover, this color balance filter 8 is also arranged in front of the optical lens mechanism 12 and tilted by about 5° against the optical axis L, as described above. Incidentally, in the light quantity correction means S2 of the present invention, one sheet of color balance filter 8 integrally composed of the cut filter and the color balance filter is used. However, in the present invention, it is not particularly limited thereto, and one cut filter 6 and a light quantity correction means S1 can be provided in parallel to be synthesized. The image reading device for photographic printing 11 of the present embodiment is not so affected by the parallel degree of respective filters B, G and R and the cut filter 6, compared to the image reading device for photographic printing 1, thereby flares and the like can be further prevented. Furthermore, by integrally synthesizing the cut filter and the color balance filter, the number of parts can be reduced to make the image reading device compact. Next, further another embodiment of the image reading device for photographic printing according to the invention will be described. As shown in Fig. 7, the image reading device for photographic printing 21 is different from the image reading device for photographic printing 11 in that a rotation plate 25 is arranged within the lens group of the optical lens mechanism 22. The optical lens mechanism 22 is divided into the first lens mechanism 22a and the second lens mechanism 22b. The light quantity correction means S3 is arranged in front of the first lens mechanism 22a. The light quantity correction means S3 can integrally synthesize the cut filter and the color balance filter, or synthesize them in parallel, as in the light quantity correction means S2 in the image reading device for photographic printing 11. Furthermore, at least one of rotation plate 25 and the light quantity correction means S3 can be tilted against the optical axis. The image reading device for photographic printing 21 of the present embodiment has a rotation plate 25 arranged within the lens group of the optical lens mechanism 22. Therefore, the reflected light from the image sensing plane of the monochrome CCD 23 is not a parallel beam, whereby the reflected light is not reflected again on the monochrome CCD 23. As a result, the occurrence of flares and ghosts can be prevented. Next, still another embodiment of the image reading device for photographic printing according to the invention will be described. As shown in Fig. 8, the image reading device for photographic printing 31 is different from the image reading device for photographic printing 11 in that the rotation plate 35 is arranged at a position ahead of the optical lens mechanism 32. The other features are identical with the image reading device for photographic printing 11. In addition, the position of the rotation plate 35 is not particularly limited in the present invention. Since the device is made compact, however, it is desired that the rotation plate should be arranged at a position apart from the optical lens mechanism 32 by, for example, 3 to 10 mm. Incidentally, the image reading device for photographic printing in the present invention is used to be mounted on the photographic printing device which reads the spectral data of the color image which is stored in the film and incident from the optical lens mechanism and respective filters B, G and R by rotating the rotor plate, then calculates the exposure conditions based on the data, and prints the image on the photosensitive material according to the conditions. Therefore, this printing device can obtain clear prints, while preventing flares, ghosts and the color divergence by the image reading device for photographic printing in the present invention. As described above, according to the image reading device for photographic printing of the invention, by arranging the light quantity correction means having stepwise spectral characteristics on the optical axis, and by synthesizing the light quantity correction means and the cut filter, the reflected light due to the conventional ND coating and the influences of the boundary plane and the parallel degree between the cut filter and the color filter disappear. Thereby the occurrence of flare, ghost and color divergence can be prevented. Furthermore, by tilting at least one of the cut filter and the light quantity correction means against the optical axis, it is prevented that the reflected light from the image sensing plane of the monochrome CCD is reflected to be incident over the image sensing plane, whereby the occurrence of flare, ghost and color divergence can be further prevented. Furthermore, by integrally synthesizing the light quantity correction means and the cut filter, the number of parts can be reduced to make the image reading device compact. Furthermore, by separating the cut filter from the rotor plate, arranging it to the optical lens mechanism, and tilting it against the optical axis, the occurrence of the color divergence can be further prevented. Though several embodiments of the present invention are described above, it is to be understood that the present invention is not limited only to the above-mentioned and various changes, and modifications might be made without departing from the scope of the appended claims.

Claims: An image reading device for photographic printing, comprising an optical lens mechanism (2, 12, 22, 32), a monochrome CCD (3, 23) image device arranged at a focal position, on an optical axis (L) of the optical lens mechanism (2, 12, 22, 32), a filter rotation plate (5, 25, 35) having a plurality of color filters (4) rotatably arranged on the optical axis (L), and a cut filter (6) for blocking unnecessary light existing on the optical axis (L), characterized in that a light quantity correction means (S1, S2, S3) having a stepped spectral transmission filter characteristic over the spectral range of visible light is arranged on the optical axis (L), such as to balance the light quantity transmitted by the color filters (4). The device of claim 1, wherein the light quantity correction means (S1, S2, S3) is housed within the optical lens mechanism (2, 12, 22, 32). The device of claim 1 or 2, wherein the light quantity correction means (S2) is a color balance filter (8) in which coating for restricting the amount of transmitting light is applied to a surface of the color balance filter (8). The device of claim 1, wherein the light quantity correction means (S1) is a color balance mirror (M) in which a coating for restricting the amount of transmitting light is applied to a surface of the color balance mirror (M). The device of claim 1 or 2, wherein the light quantity correction means and the cut filter are synthesized. The device of claim 1 or 2, wherein the filter rotation plate (25) is disposed within the optical lens mechanism (22). The device of claim 1 or 2, wherein the filter rotation plate (35) is disposed in front of the optical lens mechanism (32). The device of claim 1 or 2, wherein, at least one of the light quantity correction means and the cut filter is tilted against the optical axis (L).

Inventors: NAKAO HIROTO, NAKAO, HIROTO, Nakao, Hiroto, c/o Noritsu Koki Co., Ltd.
Applicants: NORITSU KOKI CO LTD, NORITSU KOKI CO., LTD.
Application year: 1995
Main classification: G03B27
IPC codes: G03B27