Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
2002-11-25
2004-11-02
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250S252100
Reexamination Certificate
active
06812467
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus for reading images from a photographic film disposed on an image reading optical path.
2. Description of the Related Art
An apparatus for reading images from photographic film is known as a film scanner which irradiates the film with light from a light source. Images recorded on the film are read usually by detecting light transmitted through the film with a CCD sensor or the like.
The primary function of the photographic film reading apparatus is to read images from photographic film as noted above. In recent years, however, it has been proposed to improve image quality by detecting also scratches or dust made or adhering to the photographic film as images, determining positions of the scratches or dust on the film, and correcting photo images affected by the scratches or dust.
A technique for detecting such scratches and dust on photographic film is disclosed in U.S. Pat. No. 5,266,805 (correspondence to Japanese Patent Laying-Open Publication H6-28468), for example. According to this prior technique, scratches and dust on photographic film are identified from an image read from the film by using infrared light and an image read from the film by using visible light. This technique, in general, utilizes phenomena that visible light is modulated both by an image recorded on photographic film and by scratches and dust made or adhering to the film, whereas infrared light is modulated by the scratches and dust through scattering, but is not influenced by the image on the film.
A similar technique for detecting such scratches and dust on photographic film is disclosed in Japanese Patent Laying-Open Publication H9-163133. This technique uses dark field illumination instead of infrared light illumination.
An image other than one acquired by visible light is required to detect scratches or dust on photographic film. In the former of the conventional techniques, light for irradiating photographic film is successively switched by means of a rotating filter between visible light and infrared light. A visible image and an infrared image are obtained at different points of time. In the latter technique, an optical system for obtaining a visible image and one for obtaining an image different from the visible image are arranged in separate locations to obtain the two types of images sequentially.
However, each of the above prior techniques detects a visible image and a different image (infrared image) at different points of time, which results in an extended time required for detecting the images. Where two optical systems are arranged in separate locations, the two types of images could be associated in an inaccurate positional relationship. Further, the two separate optical systems have the drawback of enlarging an apparatus configuration.
SUMMARY OF THE INVENTION
This invention has been made having regard to the state of the art noted above, and its object is to provide a photographic film image reading apparatus for detecting a visible image and an infrared image speedily, while enabling an accurate determination of a positional relationship between the two images.
The above object is fulfilled, according to this invention, by an apparatus comprising a visible light sensor for detecting a visible image based on visible light irradiating a photographic film, and an infrared light sensor for detecting an infrared image based on infrared light irradiating the photographic film. The visible light and infrared light are emitted from a light source to travel simultaneously along an image reading optical path and irradiate the photographic film.
The light source emits visible light and infrared light so that the two types of light concur in the film image reading optical path to irradiate the photographic film. The visible light sensor detects a visible image of the photographic film, while the infrared light sensor detects an infrared image thereof.
With this construction, since visible light and infrared light concur in the film image reading optical path, a visible image and an infrared image of the photographic film may be acquired by a single photometric stage, and that at the same time. Thus, a photographic film image reading apparatus is provided which is capable of detecting both a visible image and an infrared image promptly while accurately determining a positional relationship between the two images.
In an embodiment of this invention, the visible light sensor and infrared light sensor are disposed in different positions, the film image reading optical path including an optical path branching unit for directing the light emitted from the light source toward the visible light sensor and the infrared light sensor. Preferably, the optical path branching unit is arranged to direct the visible light toward the visible light sensor and the infrared light toward the infrared light sensor.
With this construction, the optical path branching unit disposed on the film image reading optical path directs the visible light toward the visible light sensor, and the infrared light toward the infrared light sensor.
The visible light sensor which detects visible images and the infrared light sensor which detects infrared images have a similar construction as sensors, and may therefore be integrated. However, a system that handles both visible images and infrared images is not necessarily common. It is difficult to manufacture an image reading sensor integrating an infrared light sensor and a visible light sensor at low cost.
Thus, the optical path branching unit is placed on the film image reading optical path as described above. This enables the visible light and infrared light to concur in the same optical path even where the visible light sensor and infrared light sensor are separate entities.
As a preferred embodiment for directing the visible light toward the visible light sensor and the infrared light toward the infrared light sensor, it is proposed that the optical path branching unit be formed of a cold mirror. A cold mirror is often used as a reflector for a lamp to reflect visible light and pass infrared light in order to avoid overheating of an illuminating optical path. Design load may be lightened by utilizing an existing cold mirror as the optical path branching unit.
It is advantageous to provide an infrared light cut filter between the cold mirror and the visible light sensor. Where the cold mirror is used to reflect visible light, part of infrared light could mix into the light reflected by the cold mirror. Such part of infrared light may be intercepted reliably by the infrared light cut filter to prevent overheating of the visible light sensor and detect visible images properly. Moreover, this infrared light cut filter is disposed in a portion of the optical path used only for guiding the visible light. Thus, a conventional infrared light cut filter may be used as it is, without increasing design load.
In a preferred embodiment of this invention, the image reading optical path includes an infrared light cut filter and a light adjustment filter arranged between the light source and the photographic film, the light adjustment filter adjusting the light to a predetermined color balance before irradiating the photographic film. Wavelength characteristics of light transmittance of the infrared light cut filter and the light adjustment filter combined allow transmission of infrared light in a set wavelength range, and cut infrared light outside the set wavelength range, in order to enable image detection by the infrared light sensor.
Not only an infrared light cut filter but a light adjustment filter usually is designed to intercept infrared light. In order to detect an infrared image of photographic film, the infrared light cut filter and light adjustment filter of such design must be removed from the film image reading optical path. Otherwise, these filters will impede detection of the visible image of the photographic film, and cause overheating of components arranged on the optical path. Thus,
Arikawa Koji
Kobayashi Kazuhiro
Nakamura Shigetaka
Tsuji Hidekazu
Fulbright & Jaworski L.L.P.
Hannaher Constantine
Lee Shun
Noritsu Koki Co., Ltd.
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