SE505477C2 - Device for reading and converting optical information into digital representation - Google Patents

Abstract

The present invention relates to an arrangement and a method respectively for reading and converting optic information to electronic representation. According to the invention this conversion takes place without any analogue intermediate storing and each pixel forming a picture element comprises a light valve device which is controllable by a controlling device and the arrangement furthermore comprises photo detecting devices (2') of a detecting unit (2) wherein to each photo detecting device (2') at least one light valve device of a light valve unit is arranged, wherein the photo detecting device(-s) (2') detects/detect incident photo energy and when a given value of photo energy is reached deliver/delivers a signal for controlling the corresponding controlling device.

Description

505 477 2 is transferred to a digitally storable image that can be reproduced on a monitor or output as a photographic image in a printer. However, the use of such CCD sensors is associated with a number of problems and involves a number of practical limitations. One problem is the difficulty of obtaining the same sensitivity in all pixels. It is associated with a number of difficulties in transporting the charges generated in each pixel out of the sensor without being affected and changed by other phenomena such as residual charges, dark current, crosstalk, etc. before being registered with the corresponding digital value in an A / D converter.

These and other difficulties mean that it becomes both technically complicated and expensive to manufacture a CCD matrix sensor. It is particularly difficult to produce a CCD matrix sensor that provides sufficient image representation according to the x-ray image quality. Depending on the number of pixels, ie the more pixels (pixels) a sensor contains, the more pixels the incident image is divided into and the higher becomes the resolution, ie the better the image can be reproduced.

THE OBJECT OF THE INVENTION = The object of the present invention is to provide a device for reading and converting optical information into digital representation. The invention also has for its object an image sensor where high resolution can be obtained in a simple and inexpensive manner. An additional goal is to convert the image or optical information into digital representation without degeneration. Another object of the invention is that the light-sensitive elements of the device or sensor should be able to be given uniformity in a simple manner.

Further objects of the invention consist in simple manufacture of a device which is also inexpensive, easy to use, etc. More particularly, the invention has for its object to provide a device for reading and converting optical information into digital representation or recording by which stored image information can also be played back or displayed. Such a device is stated in claims 15 to 22.

The invention further has for its object to provide a method for reading and converting optical information into digital representation.

A device by which both these and other objects are achieved is indicated by the features stated in the characterizing part of claim 1. A method for reading and converting optical information into digital representation is stated in claim 23. Preferred embodiments are stated by the features stated in the subclaims.

According to the invention, the conversion of the optical information into digital representation takes place directly without analogue needle storage. Each pixel comprises an aperture device controllable by a control device, an aperture unit being formed by a set of aperture devices.

Through a number of photodetecting devices forming a detection unit, at least one aperture device being arranged for each photodetecting device, the photodetecting device detects incoming light energy in the current pixel and when a certain value of the light energy is reached, the photodetecting device outputs a signal to the current control device. . The device can of course be designed in a number of ways. For example, a photodetection device can be assigned to a plurality of aperture devices or only one as well as the control device can be separate or common to the different aperture devices.

In particular, achieving the given light energy in a particular pixel leads the control device to interrupt an opening operation in progress in the aperture device. In the case that more than one aperture device responds to each detection device, the detection device can either read the aperture devices sequentially or two or more simultaneously at different designs. The photodetecting device may in particular consist of a phototransistor which emits an electrical signal when its surface is struck by photoenergy or according to further alternatives it may consist of a photodiode or a photodiode in combination with a light emitting diode.

In particular, the control device regulates the current or corresponding aperture device in such a way that it is opened at a speed which follows a given curve until a certain value of the light energy detected light energy is reached, whereby it emits a signal.

This given curve is especially such that it always has a positive derivative during opening. The regulation can especially be performed in such a way that the detected light energy corresponds to the eye's sensitivity characteristics. Alternatively, it is adapted so that the detection device reads the light with a curve that does not correspond to the eye's response curve, which is why a so-called P-function for compensation and adjustment. In particular, this P-compensation can be obtained by means of a sawtooth generator. You can also linearize the detector. When using a constant opening speed, the compensation must be made later.

The resolution is varied by varying the detection density in a manner known per se.

According to a special embodiment, a number of pixels can be arranged so as to form a matrix for forming a so-called matrix sensor, wherein a set of detection devices are arranged in connection with the aperture matrix comprising a number of pixels. According to a particularly advantageous embodiment, the mixer device is comprised of ferroelectric liquid crystals, FLC. The ferroelectric liquid 505 477 crystals are preferably in smectic AF phase. Preferably, the liquid crystal is surface-stabilized, whereby the voltage across crystals contained in the grating can be varied by means of a generator device, for example a sawtooth generator, the detection devices being arranged in a plane parallel to the mixer device matrix.

A control indicates which pixel or pixels are to be activated on the liquid crystal. For storing light energy measured in each pixel, the device further comprises an address register and a digital memory means, where further a counter is arranged for digitizing the value of the light energy before storage in the address register whereupon the information together with its address is stored in a digital memory means.

According to an alternative embodiment, a number of pixels are arranged in a row so that the device forms a row sensor. Such a device may be suitable for stationary objects etc. This line sensor can be movable, causing the sensor to sweep past the optical information to be converted in order for an image to be generated. Alternatively, the optical information may be swept past the line sensor or both options may be combined.

According to a special embodiment, the device can be designed so that it can be used as a monitor. Thereby, the detection unit comprises means for absorbing light and stored images can be displayed or played back by activating a display selector device. This can be designed so that for image display you can choose between stepping in one or the other direction. The absorbing means can then be constituted by an absorbing black surface and images stored in the memory medium are displayed by indicating their address in the address register by means of the display selection device. Via the control unit and drive electronics, the image data is thus reproduced as an image of the aperture matrix. The device, both as a sensor and as a monitor, can be arranged in a camera or the like. To form a monitor, the device can be arranged as a back piece or the like to the camera, which is so arranged in relation to the camera that the images can be easily illustrated. In particular, the device can be detachably or rotatably arranged relative to the camera or form part of it so that the images can easily be viewed only by performing a simple handshake or the like. According to an alternative, in the case that the camera consists, for example, of a SLR camera, the camera's viewfinder mirror and matte disc can be designed so that they can be rotated so much that the image matrix through reflection is illustrated and can be viewed through the viewfinder shaft. In this case, the viewfinder mirror can in particular comprise a reflective coating on both the front and the back.

According to an alternative embodiment, it is possible to arrange or integrate a set of LEDs or the like in the detection unit for illuminating the matrix.

Through the invention, it is possible to convert optical information into digital representation with high resolution and in a simple and inexpensive manner. According to a special embodiment, it becomes possible to illustrate stored electronic representation.

DESCRIPTION OF THE FIGURES The invention will be described in more detail below with reference to the accompanying figures for an explanatory and in no way limiting purpose, where Fig. 1 shows a device in the form of a sensor for reading and converting optical information into digital representation, Fig. 2 shows a device according to the invention which can be used for image display, Fig. 3a externally illustrates a device useful as a sensor and monitor arranged on a camera, Fig. 3b shows the device in Fig. 3a with an exposed image plane, Fig. 4a schematically shows a camera of mirror reflex type with a device according to the invention used as a sensor, Fig. 4b schematically illustrates the camera and the device in Fig. 4a but now in monitor position.

PREFERRED EMBODIMENTS According to a particular embodiment, described in Fig. 1, a surface stabilized photoelectric liquid crystal (FLC) is arranged in matrix form. The rear liquid crystal matrix 1 is a detection unit 2 in the form of a photosensitive matrix of photodetection devices 2 'arranged.

The matrix 1 can be said to be composed of a number of pixels arranged in matrix form. Simplified for a pixel, light can be said to be incident on an aperture device behind which a detection device 2 'is arranged, for example in the form of a phototransistor. The OH1 detection device 2 'is hit by light, ie the aperture device is open, it emits an electrical signal. Thus, if the aperture device is initially closed, no signal comes from the detection device 2 'when light is incident on the aperture device. However, if the aperture device starts to open at a time, tm by means of a control device at a certain given speed, the detection device 2 'or according to a special embodiment the phototransistor, which is so connected that at a certain incident light energy it emits a trigger signal , in achieving a given light energy, interrupting the opening operation of the aperture device at a time tr. This gives a value that is proportional to the incident light energy. What has been described here can be said to represent a pixel and the device can thus be said to comprise a number of pixels arranged in matrix form. With such a sensor according to the invention, the image information can be read directly point by point without analogue intermediate storage, where the reading can also take place in the desired manner so that e.g. the resolution can be varied. If e.g. only every third or fourth pixel on every third or fourth line is read, a low-resolution image is obtained in a simple way, and so on. The above-described mixer device can in particular consist of a liquid crystal of the ferroelectric type in smectic Aï phase.

The particular embodiment according to Fig. 1 is described in more detail below and can be said to constitute a substantially complete sensor for direct digitization of image information. According to the described embodiment, the liquid crystal matrix 1 (also called the diaphragm matrix) comprises a surface-stabilized ferroelectric liquid crystal (FLC) in Aïfas which is arranged between two glass plates with electrodes in a manner known per se. Behind this, a detection unit 2 in the form of a photosensitive matrix of photodetection devices 2 'is arranged where the detection devices 2' can for instance consist of phototransistors or photodiodes or photodiodes and light emitting diodes in combination. According to a special embodiment (not shown), the photodetection unit 2 could be arranged directly on the liquid crystal matrix, or the aperture network matrix 1, and on its rear glass plate, respectively. In the example shown, the detection unit is arranged at a distance from the aperture matrix 1 and parallel thereto.

By means of, for example, a sawtooth generator 3, an electric field is generated over the liquid crystal matrix or the aperture matrix 1. The strength of this field increases linearly with time until the field reaches a given maximum voltage, whereupon the field is rebuilt. The control device or control unit 4 controls which element or elements in the aperture matrix 1 are to be opened at a given time, ie a pixel on the FLC or the corresponding photodetection device 2 'is activated. The control unit 4 thereby opens and closes the aperture devices in, for example, a linear scanning motion. Each liquid crystal element in the diaphragm matrix 1 or the liquid crystal matrix acts as a combined mixer and shutter. Because one or more adjacent elements can be activated simultaneously, an image can be resampled. In the inactivated position, the liquid crystal matrix 1 is opaque.

In order to obtain information about the gray scale in each pixel, the opening in the liquid crystal matrix (respective aperture device) is performed in an accelerating manner, ie with a positive derivative of the opening speed function at each point. Thus the light transmittance is low at the beginning and high at the end. The light passing through the liquid crystal matrix, or the aperture devices included in the aperture unit or the aperture matrix 1, respectively, is detected by the photodetection devices 2 ', for example constituted by photodiodes. If several light-sensitive elements are included, the output signals sn sN ..., sn are summed from the various detection devices 2 'and compared in a comparator or comparator 10 with a reference signal, VM. If a signal is larger than VM, the current opening operation of an aperture device or a liquid crystal element is interrupted, whereupon a new cycle with new aperture devices or liquid crystal elements is started by the control unit 4 undergoing one cycle and thus advancing to the next. By allowing the detection devices 2 ', for example the photodiodes, to be sensitive to different light wavelengths, it becomes possible to read in a color image. The grayscale information is obtained by reading a time period counter (counter) 6 at the end of each cycle. This information together with the information on which element (s) are activated or which aperture devices are opened is stored in an address register 5 during a completed cycle. Counter 6 thus calculates from the digital value the light level measured in each pixel and the address register 5 thus receives the image in digital form.

The digitized image information is then stored in a digital memory medium 7. The registration of an image thus reaches 505 477 in such a way that, if the liquid crystal matrix 1 is seen as a diaphragm array with one aperture device per pixel, if an image is projected on the sensor, the pixel removal takes place according to a sequence stored in the address register 5 from which the control unit 4 retrieves its information about which pixel is to be read. This pixel is then activated in accordance with the above by the electric field from the sawtooth generator 3 and the drive signals A, B which constitute control signals for the liquid crystal matrix 1. At the same time, the photodetecting devices 2 'are also activated (for simplicity, all detection devices' denoted by 2' are also if these may be different). At the beginning of a ramp in the sawtooth generator 3, a start signal is also given to the counter 6 which then receives a stop signal from the control unit 4 when a certain light energy has been detected or when a certain aperture has been reached. The information in the counter about the light energy in the activated pixel or pixel is then transmitted as described above to the address register 5 for storage together with information about the address in the memory medium 7. The counter 6 is then reset and the address following the address is activated according to the given sequence. In an analogous manner, addresses stored in the address register 5 are scrolled through until these are stored together with the corresponding information in the memory medium 7.

In the example shown, the liquid crystal forming a matrix is regulated by drive electronics 9 comprising drive circuits.

In this case, the pixel address Q and the transparency of the current and current elements in the matrix (signal from the sawtooth generator 3) constitute input signals. The clock reference of the counter 6 consists of the clock generator 8. The drive signals denoted by A and B in the figure thus constitute control signals for the liquid crystal (matrix).

According to an alternative embodiment (not shown), a number of pixels defined according to the invention may be arranged in a row instead of in a matrix, to form a row sensor. In order for the image to be digitally representative, either the line sensor must move over an optical image in an image plane or the optical image must sweep over the sensor, this line by line registering and building up a digital representation of the optical image. Such an embodiment is useful, for example, for motionless images. What has been described above with reference to a so-called matrix sensor essentially also applies to a row sensor.

The invention can advantageously be designed in a number of different ways.

For example, the image produced may originate from an imaging camera optics or from the projection of a transparent or view image as in a scanner. Furthermore, the number of detection devices need not correspond to the number of pixels, pixels, in the liquid crystal.

Furthermore, alternatives to a ferroelectric liquid crystal are also conceivable. As mentioned above, a detection device may cover or correspond to several pixels or pixels; however, it is essential that only one of these pixels or pixels (corresponding to one and the same detection device) is activated each time, ie these are read and activated separately.

Fig. 2 shows an example of how the device can also be used for monitoring. The above description of Fig. 1 is also largely applicable to this embodiment, which is why only the playback (display) function is described. In the described example, the detection unit 2 is provided with an absorbent, black surface (not shown). After images have been registered and stored in the digital memory medium 7, these images can be displayed ("played back") by activating an image display selector ll, for example comprising two pushbuttons or the like by means of which it is possible to step by step through the The images are stored in the desired direction, forwards or backwards depending on which button is pressed. Here, of course, a number of other design options are possible and the stepping can be effected in a number of different ways. If, for example, the key marked with + is pressed, the image is displayed. last registered by indicating the address of this image in the address register 5 so that image data from the digital memory medium 7 via the control device or control unit 4 and the (FLC) drive electronics 9 are reproduced as an image on the image matrix or FLC matrix 1.

Another alternative for playback or display of images (not shown) is that an active light source is arranged behind both the image matrix and the detection unit. Alternatively, a set of LEDs or the like may be provided or integrated in the detection unit for displaying the stored images for lighting reasons. Address generation takes place for playback, for example according to the same linear scanning function as during recording, but the speed can be selected in a different way.

Fig. 3a schematically shows an example of how a device according to the invention finds its application in combination with, for example, a system camera 13. The device can then be accommodated in a removable, alternatively fold-out or similar, back piece 12, in analogy with a film magazine. In order to view stored images, the back piece 12 (shown separately in Fig. 3b) is then removed, it could also be folded out or the like whereupon the image matrix (FLC matrix) 1 is exposed and with the aid of the image selector 11 the images can be displayed on the image matrix one way or the other.

In Figs. 4a and 4b, respectively, the application of the device to a camera 16 is illustrated by so-called mirror-reflection type 16. In Fig. 4a the camera's viewfinder mirror 14 and matte plates 15 are arranged in position for image recording while viewfinder mirror 14 and matte plates 15 in Fig. 4b are rotated 90 ° so that the image matrix or FLC matrix 1 is visible through the viewfinder shaft, i.e. 505 477 the device is used for image monitoring. In this case, the viewfinder mirror 14 may be provided with a reflective coating on both the front and the back.

The invention will of course not be limited to described embodiments but can be varied freely within the scope of the claims.

Claims (26)

10 15 20 25 30 35 505 477 14 Patent claims A device for direct reading and conversion of optical information into digital representation, the device comprising a number of pixels, each pixel comprising an aperture device controllable by a control device (4), the aperture devices forming a diaphragm unit and the device further comprising a number photodetection devices (2 ') included in at least one detection unit (2), where at least one aperture device included in a diaphragm device is arranged for each photodetection device (2'), characterized in that the conversion takes place directly without analogue intermediate storage and that the control device or the control unit (4) regulates the current or corresponding aperture device in such a way that the aperture is opened at a speed which follows a given curve until a certain given value of the light energy detected by the photodetecting device (s) (2 ') is reached, whereupon this (2' ) emits a trigger signal. Device according to claim 1, characterized in that obtaining the given light energy in a pixel leads to the control device (4) interrupting an opening operation in progress in the aperture device. Device according to one of Claims 1 or 2, characterized in that a separate aperture device corresponds to each detection device (2 '). Device according to Claim 1 or 2, characterized in that more than one aperture device corresponds to each detection device (2 '), the detection device (2') reading the aperture devices (2 '). sequentially. Device according to one of Claims 1 or 2, characterized in that the detection device (2 ') reads more than one aperture device at the same time. Device according to one of the preceding claims, characterized in that the photodetection device (2 ') comprises a phototransistor which emits an electrical signal when its surface is struck by light energy. Device according to any one of claims 1 to 5, characterized in that the photodetection device (2 ') comprises a photodiode or photodiode and LED in combination. Device according to any one of the preceding claims, in that a number of pixels comprising a diaphragm device are arranged such that they are characterized by a matrix (1) for forming a matrix sensor, wherein in connection with this diaphragm matrix (1) a set of detection devices (2 ') are provided. Device according to any one of the preceding claims, characterized in that the aperture device is comprised of a ferroelectric liquid crystal (FLC). Device according to claim 9, characterized in that the ferroelectric liquid crystal is in smectic A * phase. Device according to Claim 10, characterized in that the liquid crystal is surface-stabilized, in that the voltage across the crystals contained in a lattice can be varied by means of a generator device (3), preferably preferably a sawtooth generator, where a set of detection devices (2 ') are arranged in a plane parallel to the aperture matrix (1), the device further comprising a control unit or control device (4) for activating pixels on the liquid crystal matrix (1) and against respective pixels. corresponding detection device (2 '), wherein. the device further comprises an address register (5) and a digital memory means (7), the value obtained in a counter (6) at the time of achieving a certain given light energy in the element and associated address being stored in the digital memory means (7). Device according to one of Claims 1 to 7, 9 to 11, characterized in that a number of pixels are arranged in a row so that the device forms a row sensor. Device according to claim 12, characterized in that the line sensor is movable so that for generating an electronically represented image the sensor is caused to sweep past the optical information to be converted or alternatively the optical information is swept past the line sensor or a combination of both. Device according to any one of the preceding claims, characterized in that the detection unit (2) comprises means for absorbing light and that stored images are displayed or played back by activating a display selector device (II). The device according to claim 14, characterized in that the display selector device (11) is designed so that for image display it can be selected between stepping or the like in any direction (+ -). 10 15 20 25 30 35 505 477 17 Device according to one of Claims 14 or 15, characterized in that the sawing means for absorption comprises an absorbent black surface and that images stored in the memory medium are displayed via an address indicated by the display selector device (11) in the address register (5), whereby image data via the control unit ( 4) and drive electronics (9) are shown as an image of the matrix (1). Device according to one of Claims 14 to 16, characterized in that it is arranged in a camera (13) or the like and forms a unit (12) such as a back piece or the like which is arranged in the camera (13) in such a way that the images become visible. Device according to claim 17, characterized in that the device is detachably or rotatably arranged in the camera (13) or the like. Device according to one of the preceding claims, arranged in a camera of, for example, the SLR type (13 '), characterized in that the viewfinder mirror (14) of the camera (13') and the mat plate (15) are designed so that they can be rotated so much that the image matrix reflection is illustrated and can be viewed through the viewfinder shaft. Device according to one of Claims 1 to 13, characterized in that an active light source is arranged behind the image matrix and the detection unit (2) for displaying images stored in the device. 21.. Device according to one of Claims 1 to 13, characterized in that a set of LEDs or the like is arranged or integrated in the detection unit (2) for displaying images stored in the device. 10 15 20 25 30 35 505 477 18 A method for converting optical information into digital representation, wherein a number of pixels, comprising a aperture device, receive optical information, for example in the form of a projected image or the like, the method comprising the following steps: - detection devices included in a detection unit (2) (2 ') detects the light energy in a pixel belonging to a detection device (2'), and characterized in that - the detection device (2 ') upon reaching a certain given threshold value emits a trigger signal and that each aperture device belonging to a certain detection device (2 ') is activated separately. Method according to claim 22, characterized in that the aperture devices included in the aperture unit are separately controllable by at least one control device or control unit (4) and that the method comprises the following steps: - in an address register (5) information on reading sequence of different pixels, - a control unit (4) receives information from the address register (5) about which pixel is to be read, - the control unit (4) emits a signal to the specified pixel whereupon this pixel and associated detection device is activated, - the control device controls activated aperture device (2 ') to be opened at a certain given speed v (t), - at the same time as the opening of the aperture device is started a counter (6) is started, - the detection device (2') emits a signal when a certain given threshold value of the light energy is reached, 15 20 25 30 505 477 19 - the counter (6) is stopped, - in the counter (6) the registered value is stored and the registered value in the time for achieving the given the energy is stored together with the address of each pixel in a memory medium (7), - the counter (6) is reset, - the address register (5) provides the control unit (4) with a new address indication for the following pixel and the corresponding detection device (2 ') according to the given sequence, - the steps are traversed again, etc. until the addresses given in the address register (5) have been traversed. A method according to claim 23 or 24, characterized in that the mixer unit comprises a ferroelectric liquid crystal (FLC). 25. A method according to any one of claims 22-24, characterized in that the aperture devices are arranged to form a matrix (1) and that the detection devices (2 ') form a set of, for example, phototransistors or photodiodes which are preferably arranged in a plane behind the matrix (1). 26. A method according to any one of claims 22-24, characterized in that the aperture devices are arranged in a row to form a row sensor, the row sensor being either movable in relation to the optical information or vice versa.