NO320729B1 - Device for transferring full-frame films comprising a series of images into a photosensitive material - Google Patents

Description

The invention relates to the field of image communication and apparatus or arrangements for projecting photographs. More precisely, it relates to a photographic copying apparatus (eng: printing apparatus) for copying cinema film by projection. The invention further relates to a method for producing a film from e.g. a TV signal.

More specifically, the invention relates to a device for transferring full-frame digital and/or analog full-frame films to a photosensitive material.

The present invention comprises a device for optical recording/copying of negative and/or positive full-frame digital and/or analogue films and/or computer graphics and/or video/TV signals on a negative or positive (celluloid) film of any type or manufacturer .

Two different technologies are currently used to transfer live film from digital format to analog format:

• CRT (Cathode Ray Tube)

• Laser

Movies are composed of a number of full images (frames) shown one at a time to give the impression of movement. When recording the movies, the recording can be done by dividing the image into lines and writing the image line by line.

In general, we can say that both technologies expose the celluloid film line by line within an image in contrast to the technology according to the invention which exposes the celluloid film with a full image for each exposure.

CRT technology

Cathode Ray Tube (CRT) technology uses a powerful high-resolution picture tube to project film and expose light in a 3-pass process through a rotating RGB (red, green, blue) color wheel or three separate picture tubes with separate R, G and B color filters . It uses three tubes to display each of the three basic colors, red, green and blue. The CRT technique writes one image at a time and each image point by point, line by line. There are few moving parts in a CRT machine and thus relatively little maintenance.

This technique is robust and well known. However, the quality has a reputation for having several flaws. CRT has a limited contrast range, pronounced grain structure, reflective stray light, insufficient color reproduction and requires long exposure times. The reason for many of these quality deficiencies can be found in the low light output of cathode ray tubes, the light source used in CRT recorders. To compensate for this, many methods are used: a more high-speed film (= more grainy) is used, lower density range is selected, brighter, more broadband color filters are used, resulting in insufficient color separation and low-speed shooting (15-30 sec. per . image).

Laser technology

Laser is a complex and very expensive technology. High-intensity laser light is reflected from spinning mirrors to expose the film. Laser recorders have a reputation for heavy maintenance and are very expensive. It is considered to provide a higher quality output than CRT with speeds of around 5-10 sec./frame. Like the CRT, the laser writes each image line by line.

The laser recorder relies on a host computer to process image data and transfer it one line at a time to a line buffer in the recorder. The data in the line buffer is then routed through a digital to analogue converter (digital to analogue converter, DAC) to the input of the acousto-optic modulators (AOMs) which modulate the image data on the laser beams. Before reaching the AOMs, the light from each laser is adjusted to the required intensity by an attenuator. This is supposed to adjust for variations in film batch sensitivity and compensate for variations in the laser's output energy. Inside the AOM, the laser beam passes through a crystal, and the internal lattice structure of the crystal deflects the laser beam. By exciting the crystal with a high-frequency wave, the lattice structure of the crystal, and thus the intensity of the laser beam, can be varied pixel by pixel. The three laser beams are then combined and expose the film using a rotating pentaprism; one rotation exposes one line.

The biggest disadvantage of known technique compared to the invention is the time consumption. The laser units also have a limited lifespan and replacements are expensive. The actual recording costs will thus be higher with a laser recorder than with the device according to the invention. In addition to this, the shuttles of the laser and CRT recorders must move with extreme precision throughout the exposure, since any variation in speed would cause variation in the distance between individual lines. This will in turn form artificial lines in the image.

GB A 2005 relates to a process and apparatus for transcribing a color video disc into a motion picture film. A color television signal representing a series of images is read onto the video disc, these images are reproduced on a television receiver and the screen of the television receiver is filmed by means of a camera. This corresponds to an improved version of the CRT recorder described above.

GB A 2255255 relates to an apparatus and a method for recording a video signal on cinema film. A video signal is recorded on unexposed cinema film by illuminating a DMD unit with a light source. The elements of the DMD are controlled in response to the video signal. The light is selectively reflected from the DMD on an image plane that includes film so that the light reaching the film is representative of the video signal.

US 4145710 relates to a method and a device for transferring analogue TV images to photographic film. The images from the analogue TV signals are digitized so that two half-images that make up a TV image can be brought together to give a complete TV image which can then be transferred to a film.

Otherwise, reference is made to US 5150205 and EP A2 1098536 which indicate the background technology for the invention.

The purpose of the present invention is to provide a device for transforming digital and/or analogue live films into a photosensitive material. More specifically, it is an object of the present invention to provide a device for recording full frame digital and/or analog movies, computer graphics, and/or video/TV signals on an analog film for live movies.

The purpose of the invention is achieved by means of the features of the patent claims.

The device according to an embodiment of the invention comprises a digital head which comprises at least one light source, a color filter, a light modulation device and a projecting lens, a shutter device, a film transport device and a combined control system which is partly included in the digital head, which comprises user interface, transport and shutter synchronization, image calibration system and "graphical computer interface". The components are preferably attached to a mechanical structure and enclosed in a housing.

The photosensitive material on which the digital and/or analogue live films are to be projected can e.g. be a celluloid film, photosensitive paper, or any other photosensitive material suitable for carrying a representation of a living film. In a preferred embodiment, the photosensitive material is adapted to display live films. Both the original digital and/or analogue film and the projection can be either positive or negative.

The light source emits light into the optical path of the digital head. Between the light source and the light modulation device in the light path, is a color filter. This can be a rotating color wheel, divided into lots of different colors, passing lights of different colors sequentially (in series). The colors of the color wheel will preferably be the three primary colours, red, green and blue. Alternatively, light may pass through a separate color filter for different colors, to be transmitted to separate color modulation devices. The latter provides the best optical performance, since all colors are transmitted continuously in parallel.

The light modulation device for modulating the light from the light source can e.g. be a DMD (digital micromirror device), as part of a DLP (digital light processing) device, transmissive LCD (liquid crystal device) device or a reflective LCD device. The light modulation device must be a full-frame digital device

(ie be able to display all image lines at once). The light modulation device may be of a type that modulates all three primary colors (red, green, blue (RGB)), or the device may comprise three light modulation devices, each capable of modulating one of the three primary colors.

The digital head also includes processing electronics and software to process input image data. The input image data may be in any type of displayable image format, digital or analog, such as television formats, video formats, computer graphics formats, etc. The image representation may be either a positive or a negative representation. Processing electronics and software can be adapted to process both digital and analogue data, and includes e.g. AD converters to convert an analog signal to a digital signal for further processing, video decoding and video de-interlacing elements to convert video signals to signals viewable by a digital system, etc. Processing electronics/software further controls the light modulation device according to known protocols/standards to provide the correct modulation of the light to be projected onto the photosensitive material. The processing of the input image data takes care of the representation of a live film in such a way that the number of full frames per the time unit in the original film corresponds to the number of projected full frames per unit of time. The projected images can be either positive or negative according to the desired use of the product.

At least one projection lens with fixed or variable focal length for scaling the entire image of the live film to fit the photosensitive material, e.g. celluloid film, is placed in the light path after the light modulation device(s). The variable focal length is achieved through a combination of lenses where the positions of the lenses can be varied manually or automatically.

The light from the light source follows a light path through the color filter, is reflected from or is transmitted through the light modulation device, and is focused on the photosensitive material by the projecting lens(es).

As mentioned earlier, the image data is received by the digital head through the graphic computer interface connected to the digital head. The graphical computer interface comprises a processor and data transmission lines, and preferably a monitoring device. The monitoring device may be adapted to display the image data that is input to the digital head. The graphical computer interface may be adapted to connect to external equipment for transferring and/or displaying image data. The live movies transferred to the digital head may have a digital or an analog representation, and the graphical computer interface is adapted to receive and/or transmit both analog and digital data.

A graphical user interface may additionally be connected to the digital head, to receive and display information regarding the progress of exposure of images on the photosensitive material. This information may include calibration reference, film reference (eg film name, duration, format, etc), film length used, measured image quality, estimated time remaining, alarms in case of broken film, etc.

The photosensitive material is placed in a film transport device. The film transport device comprises rollers arranged at a distance from each other. The rollers form two magazines which stop the light from being transmitted through to the photosensitive material, a supply magazine for unexposed, and a second storage magazine for exposed photosensitive material, e.g. film. Their storage capacities can e.g. be 305, 610 or 1220 metres. The photosensitive material is transferred from one roll to the other, thus defining a plane which coincides with a plane through the focal point/projection point. The transport device further comprises film guide latches to secure the photosensitive material in the correct position, film port, film aperture port to allow light to expose the photosensitive material, and film channel representing the path of the photosensitive material. The control signal for

the film transport device is generated in the digital head.

A shutter is located in front of the aperture port. The shutter can be of a mechanical type or alternatively e.g. an LCD shutter. Control electronics in the digital head can control the operation of the shutter. Alternatively, the shutter can be controlled by the transmitting device. When the shutter is closed, no light is transmitted to the photosensitive material, but when the shutter opens, light is transmitted to the photosensitive material and the image is taken/recorded. The time that the shutter is required to be open can be determined by control electronics in the digital head based on information received from at least one image sensor located adjacent to the photosensitive material, which relates to image quality. The image sensors can sense brightness, color saturation, contrast, etc. The sensor values corresponding to each of these quality factors are compared in the digital head with pre-stored calibration values, and based on the differences of the values, the correct exposure time is selected from a table.

The above-mentioned sensor values are also the basis for the control signal from the digital head to the light modulation device(s). If the detected values for e.g. color balance, black level, contrast, etc, deviate from the expected/preferred values, the digital head transmits the signal to the light modulation device to reduce the deviation.

Other sensors can also be included in the system and sensor data fed to the digital head. Examples of such sensor data are film break (a sensor that detects the presence of a photosensitive material in the exposure area), film movement speed, length of exposed film, etc. This information can be transferred to the graphical user interface to be displayed to the user of the device.

The transfer to the photosensitive material can be carried out using two different methods. In a preferred method, which is carried out using the system described above, the live films are transmitted/recorded frame by frame. The transport of the photosensitive material is periodic, with pauses in the movement until a full image has been exposed on the photosensitive material. The time period for stopping the movement can be a predetermined time period, or the transport of the photosensitive medium continues when sensor values satisfy reference values.

The alternative method uses continuous movement of the photosensitive material, recording the live film line by line to project one full line at a time. To carry out this method, the light modulation device must be of a linear type, preferably a linear version of the above-mentioned types of modulators.

The invention will now be described in more detail by way of example and with reference to the accompanying drawings. Fig. 1 is a schematic view of the device according to the present invention.

Fig. 2 shows a configuration of the optical path inside the digital head.

Fig. 3 shows an alternative configuration of the optical path inside the digital head. Fig. 4 shows a block diagram illustrating the signal communication in the device according to the invention. Fig. 1 gives an overview of the device according to the invention. The digital head 10 plays a central role in the device, receiving, processing and transmitting signals to/from the other components of the device. The digital head 10 additionally comprises essential optical components, which will be explained later in connection with fig. 2 and 3. The digital head 10 is connected to the graphic computer interface 11 via a signal cable 20, e.g. a serial line, a serial digital interface (Serial Digital Interface, SDI) or digital visual interface (Digital Visual Interface, DVI). The live film input data was transferred from the graphic computer interface 11 to the digital head 10 and is processed there. The data processing results in a set of instructions to the imaged optics in the digital head and instructions to a film transport control 13 and a shutter 22. The optics in the digital head 10 transform the processed image data into modulated light representing the image to be recorded on the photosensitive material 26. The photosensitive material is in one embodiment celluloid film.

A projection lens 17 is also included in the optical head. The projection lens 17 projects light representing the image onto the film to expose the area of the film where the light projects the image. The projection lens 17 is preferably a high-quality lens with excellent optical properties, such as small abrasions, small reflections in the visible wavelength spectrum, uniform color and brightness, etc.

A shutter 22 controls the amount of light reaching the film. The shutter is in one embodiment a mechanical shutter, but in another embodiment can be an LCD shutter. The time period of the open shutter 22 determines the amount of light that exposes the film. The open-close operation of the shutter 22 is controlled from the digital head 10, by open/close signals transmitted over the electronic connection 24.

A transport system 14 for the film is provided near the digital head output and the shutter 22. The film 26 is wound on at least two roller devices 15a, 15b; one supply device 15a for providing the device with unexposed film and one temporary storage device 15b for winding the exposed film until the desired amount of images is recorded. The rolling devices are preferably covered by a light-tight housing. The roller devices 15a, 15b are rotated by means of motor devices, e.g. servo motors. The roller devices 15a, 15b are separated to release a quantity of film for exposure. Between the two roller devices 15a, 15b, the transport system 14 comprises film guide locks 16 to control the path of the film between the roller devices 15a, 15b. The transport system 14 further includes a film aperture port to allow light to reach the film on a defined portion of the film.

At least one image sensor 23 is provided near the film aperture port. The image sensor/sensors 23 detect the recorded image quality and transmit sensor information to the digital head 10. The image sensor 23 can e.g. detect brightness, color balance, color saturation and contrast in the image. The sensor values for each characteristic are compared to reference values stored in the digital head. If the difference is greater than a predetermined threshold value, the digital head sends corrected instructions to the imaging optics to achieve better recording performance.

The information from image sensors is also used to control the shutter 22. When the sensor values corresponding to exposure times are different from the desired values, the digital head extends or decreases the shutter's open time period.

A film transport controller 13 controls the progress of the film in the transport system 14 by controlling the motors of the roller devices 15a, 15b. The film transport control receives synchronization information from the digital head and rotates the rollers accordingly. The synchronization information from the digital head may include start and stop signals, interval times, film speed, etc., ensuring that the correct portion of the film is exposed for each frame.

The digital head is also connected to a user interface 12. The user interface 12 displays information regarding the recording progress, such as the amount of film remaining in the supply device 15a, remaining time for the recording, image quality, film references (name, duration, format, etc), and alarms when errors occur due to broken film or other reasons. This information is based on the sensor information contained in the digital head 10.

Fig. 2 is a diagram of a configuration of the optical components in the digital head. A light source 36 emits radiation in the visible wavelength range. The light source can be any light source with the desired wavelength emitting properties, e.g. which has good emission properties in the visible light spectrum, which has sufficient brightness to expose the film without too long shutter times, etc. In one embodiment, the light source is an off-the-shelf incandescent lamp.

A color wheel 27 placed in the light path filters out the desired colors sequentially as it rotates at a predetermined speed. The colored light is modulated by a single light modulation device 28 and is transmitted to the projecting lens 17. The projecting lens projects the modulated light onto the film 26. Fig. 3 is a diagram of another configuration of the optical components of the digital head. The light source 36 is the same as in fig. 2, but in this case the light beam passes through three separate color filters 30a-c. The three colored light beams are modulated by three separate light modulation devices 31, 32, 33, and are collected by the lens 17 to expose the film 26. Fig. 4 illustrates the signal communications in the device in according to the invention. The digital head 10 plays a central role in controlling the functions of the device. The digital head 10 receives image data from the graphic computer interface 11. The graphic computer interface 11 may be connected to an external data source 40. This may be an external computer, video machine, television or other source of image data. The digital head receives sensor data from the sensor devices 41 and uses this in processing the image data. At least some of the sensor data is displayed on the user interface 12. The digital head transmits control signals to the film transport control 13 and to the shutter, also based on the image data processing and the sensor data. The film transport control transmits control signals to the film transport system.

Claims (13)

1. Device (1) for transferring full-frame digital and/or analog films, comprising a series of full-frame images, to a photosensitive material, the device comprising a light source (36), a color filter (27), at least one projecting lens (17), a shutter device (22) and a transport device (14), characterized in that it further comprises: - a digital head (10) comprising the light source, the color filter, at least one whole-image device for light modulation (28), at least one lens for projecting the modulated light directly onto the photosensitive material (26), processing electronics and software for processing input image data, and for transport and shutter device synchronization, - a user interface, - a graphical computer interface (11) connected to the digital head and - at least one image sensor (23) connected to the digital head for sensing optical properties of the image which is projected onto the photosensitive material, the digital head using the sensor signals to control the shutter device and/or the light modulation device, while the transport device (14) is adapted to expose, batch by batch, the portions of the photosensitive material corresponding to each of the frames to the modulated projected light, in such a way that the number of frames per unit of time in the original film corresponds to the number of projected frames per unit of time . 2. Device according to claim 1, characterized in that the device for light modulation (28) is a DMD (digital micromirror device), transmissive LCD or a reflective LCD. 3. Device according to claim 1, characterized in that the graphical computer interface is adapted to receive image data from an external computer. 4. Device according to claim 1, characterized in that the image data can have a digital and/or analogue format. 5. Device according to claim 1, characterized in that it comprises only one device for light modulation, and that this light modulation device is adapted to modulate the three primary colours, red, green and blue. 6. Device according to claim 1, characterized in that it comprises three devices for light modulation, where each is adapted to modulate one of the three primary colors red, green, blue. 7. Device according to claim 1, characterized in that the color filter is a color wheel divided into sectors with different colors, preferably three primary colors, red, green, blue. 8. Device according to claim 6, characterized in that the color filter comprises separate color filters of different colors. 9. Device according to claim 1, characterized in that the digital film and/or the analogue representation of the film can either be in negative or positive format. 10. Procedure for transferring full-frame digital and/or analogue films comprising a series of full-frame images to a photosensitive material, characterized in that it comprises the following steps for each full image: a) receiving image data through a graphic computer interface (11) to a digital head (10), b) processing the image data in the digital head (10), c) modulating the light from a light source (36) by means of a device for light modulation according to the processed data, d) projecting the modulated light from the light modulation device (28) directly onto one part of a photosensitive material (26), e) sensing image characteristics with image sensors (23) located near the photosensitive material, to provide signals to the digital head relating to optical properties of the projected image, the digital head using the sensor signals to control a shutter device (22) and the light modulation device (28), f) moving the photosensitive material, by means of a transport device (14), to expose the next part, g) repeating steps d) - f) until the desired parts of the photosensitive material have been exposed for the projected modulated light, in such a way that the number of frames per unit of time in the original film corresponds to the number of projected frames per unit of time. 11. Procedure according to claim 10, characterized in that the image data can have digital and/or analogue format. 12. Procedure according to claim 11, characterized in that the processing of the image data includes converting analogue signals to digital format. 13. Procedure according to claim 10, characterized in that a full image of the film is projected onto the photosensitive material in step d).