WO2009041803A2

WO2009041803A2 - Image scanning device and method

Info

Publication number: WO2009041803A2
Application number: PCT/MY2008/000113
Authority: WO
Inventors: Hock Woon Hon
Original assignee: Mimos Berhad
Priority date: 2007-09-25
Filing date: 2008-09-25
Publication date: 2009-04-02
Also published as: WO2009041803A3; MY144951A

Abstract

An image scanning device comprising of energy ray sensitive elements (101), lenses (103), a slit collimator (104) and a controller (105) is disclosed. Energy ray sensitive elements (101) refer to photo sensitive materials to capture visible light or thermal sensitive materials to capture infrared, which gives electrical signal corresponding to incident energy ray. The energy ray sensitive elements (101) are arranged in an array and the lenses (103) are arranged in an array and placed in front of the sensitive elements (101). The slit collimator (104) is used to select energy ray column to be acquired at a time. The controller (105) is used to control the motion of the slit collimator (104) from a start position to an end position, to stop at every column and acquire image data of an exposed energy ray sensitive column at a time, whereby the sequence of acquiring columns of images forms a two dimensional image.

Description

IMAGE SCANNING DEVICE AND METHOD

The present invention relates generally to image scanning device and method. More particularly, the present invention relates to scanning of images using an array of photosensitive elements incorporating a line-scan sensor with synchronized mechanical motion of a slit collimator.

BACKGROUND TO THE INVENTION

Apparatus such as digital copying machine, bar code reader and scanner rely on image forming device to scan and form image. It is usually built to be very small to fit a semiconductor chip so that it can be space efficient. Due to its size and structure, the device is built as a micro-electromechanical (MEMS) device.

A widely used mechanism uses a beam supported type vibration mirror driven by electrostatic force. There are a few embodiments to achieve this mechanism.

An embodiment uses a mirror substrate supported by two beams provided on the same line. The two beams are twisted to perform reciprocating motion with electrostatic force exerted between the mirror substrate. It happens that the two beams are used as rotating axis.

•Another embodiment uses an electrostatically-actuated vibration mirror. There is a vibration mirror that causes a mirror substrate to perform reciprocating motion. The ₍vibration mirror is driven to perform reciprocating motion at a resonance point. 'However, the vibration mirror has a swing angle and resonance point that varies according to ambient temperature.

An attempt to reduce variation of the swing angle uses an electric resistive element to serve as heater so that temperature variation is suppressed by increasing or decreasing the heat value of the electric resistive material. However, the electric resistive material may not be reliable in a beam that is easily deformed. Furthermore, the electric resistive material and control element will complicate the device further.

Another embodiment uses a polygon mirror as a deflector that scans an optical beam. To capture high resolution image, it is necessary to further increase the movement speed of the mirror. However, the bearing supporting the mirror may generate heat and noise.

A novel approach of capturing image is desirable to overcome the above-mentioned drawbacks.

SUMMARY OF THE INVENTION

The present invention is an imaging technique to acquire two-dimensional images using a single line-scan sensor with synchronized capturing mechanism of a controllable slit collimator. The imaging concept allows the selection of a region of interest where the field of view of the captured window can be determined by the distance traveled by a slit collimator. The selection of the capturing field of view / window can be achieved by selecting the start and end traveling position of the slit collimator. In this way, image of a static object can be obtained when the slit collimator travels perpendicular to the sensor.

The imaging technique is desired to capture image with spectral range of interest. To capture visible light, a photo sensitive element is used. To capture infra red energy, a thermal sensitive element is used. Energy ray refers to any electromagnet wave with spectral range of interest.

It is an object of the present invention to use a lower number of energy ray sensitive elements, i.e. a single line-scan sensor, to produce an equivalent two-dimensional image as produced by a standard matrix pixel array. Energy ray sensitive elements such as photo sensitive element is desired to capture visible light while thermal sensitive element is desired to capture infra red energy.

It is another object of the present invention to provide a simple electronic setup as compared to a standard two-dimensional matrix setup; only one column of information is read out from sensor at a given time. Therefore, only the column readout circuit is required to do so.

It is yet another object of the present invention to allow the image resolution to be tweaked by varying the number of energy ray sensitive elements in a column without significantly increasing the complexity of the setup. It is a further object of the present invention to act as a standard line-scan sensor to acquire image of a moving object with the position of the slit collimator fixed at a certain predefined position within the traveling range. The line-scan sensor formed in this manner has the flexibility to acquire information from specific view by selecting specific position for slit aperture of the slit collimator.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in greater detail, by way of an example, with reference to the accompanying drawings, in which:

Fig. 1 illustrates a diagram of energy ray sensitive element capturing energy rays from different directions;

Fig. 2 illustrates a diagram of image scanning method according to the present invention;

Fig. 3 illustrates a cross section view of an embodiment of the image scanning method in a microelectronic mechanical system (MEMS) structure;

Fig. 4 illustrates a top view of the image scanning device according to Fig. 3; and

Fig. 5 illustrates a flow chart of a method to capture image.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to Fig. 1, there is illustrated an embodiment of the present invention for image scanning device. An energy ray sensitive element 101 is used as a sensor to capture desired image. The energy ray sensitive element may be a photo sensitive element which is desirable to capture visible light or a thermal sensitive element which is desirable to capture infrared energy. A plurality of energy ray sensitive elements 101 is arranged in a column to capture energy rays from different directions

102 through lens array 103. A plurality of lenses is arranged in a column of lenses

103 in front of the energy ray sensitive element to focus incident energy ray to the energy ray sensitive elements 101. Incident energy ray from various directions within the field of view of the lens can be focused on the energy ray sensitive element during the motion of the slit collimator at a given time. Thus, the basis of the sensing mechanism is described.

From this point onwards, the energy ray sensitive material 101 is referred as a sensor 101. The column of sensor and lens forms a combination to acquire a one- dimensional image. A plurality of column of sensor and lens arranged to form an array of sensor and lens with synchronized slit collimator motion forms the basis for capturing two-dimensional images.

A slit collimator 104 is placed in front of the lenses 103 to allow a one-dimensional image to be captured at a given time, as shown in Fig. 2. The slit aperture 104 allows incident light from specific direction to fall on the sensor column 101. The motion of slit collimator 104 is governed by a controller 105 to move across the columns of sensors 101. The motion of the slit aperture 104 is synchronized with the acquisition of image 106 to form a two-dimensional image of a targeted scene. The direction of motion of the slit collimator 104 shall be perpendicular to the lens array 107.

A structure for microelectronic mechanical system (MEMS) application using the above-mentioned concept will now be described in detail.

Fig. 3 and Fig. 4 show a detailed structure of the proposed embodiment of the invention for MEMS application. A slit collimator 304 is used to block unwanted light into sensor 305. A filter 302 is used to allow only a certain range of spectrum energy to reach the sensor. Lens 303 allows energy ray to focus into sensor 305. Lens 303 will focus incident light from various direction into sensor 305. A slit aperture 307 allows a certain amount of light to enter sensor 305.

The sensor 305 has photo sensitive properties or thermal sensitive properties. The sensor receives energy ray and converts them into electrical signals. The electrical signals are sent to an electronic reader 306, which then reads out one-dimensional image data from the column of sensors. A slit collimator control 311 is used to control the motion and position of the slit collimator 304. It selectively allows and disallows light from certain directions to enter sensor 305 through the slit aperture 307. The slit collimator 304 can also be set a start and end position of the slit collimator 304 motion to select a region of interest view. A synchronizer 308 is used to synchronize motion of the slit collimator 304 and the electrical signal from reader for image capture. Selective energy ray 312 may pass through slit aperture 307 to reach sensor 305. Fig. 3 shows the assumption for first order of geometry for the ray. Rays that are marked in a dotted line refers to blocked lights 312 and possible light path 309 if the slit aperture 307 allows it to reach the sensor 305.

The operation and technique according to a preferred embodiment of the present invention will now be described.

Image scanning uses a method illustrated in a flowchart, as shown in Fig. 5. At the beginning, the device is initialized to reset the slit collimator to its home position 501, which is on the first opening. At the same time, memory to store image is cleared. Then, the area of interest selected logic is determined 502. If the area of interest is not selected, than the start and end position of the control for slit collimator would be set to minimum and maximum values; which is the full traveling distance 504. With the data for area of interest, the sensor window is then exposed to a light source or scene of interest 506. The sensor is exposed to collect photons 508. In order to speed up the scanning process, minimum light integration is recommended. Once, minimum light collection is reached, data is transferred to the memory in electronic reader 510. When data transfer is completed, the logic of the position of last slit aperture position is determined 512. If the last position is not reached, the slit aperture is moved to the next aperture position 514. At the next slit aperture position, the sensor is exposed and the process of light collection and data transfer is repeated. It is repeated until the last aperture position is reached, where a two dimensional-image is then formed 516.

The method described can also be operated to act as a line-scan sensor to acquire image of a moving object with the position of the slit collimator fixed.

Accordingly, the present invention has a simple setup of scanning image by using a plurality of column of sensors incorporating synchronized motion of a slit collimator to produce a two-dimensional image. Although the descriptions above contain many specificities, these should not be construed as limiting the scope of the embodiment but as merely providing illustrations of some of the presently preferred embodiments. The imaging technique can be applied to standard optics as well as MEMS devices.

Claims

1. An image scanning device comprising: energy ray sensitive elements (101) arranged in an array; lenses (103) arranged in an array and placed in front of the sensitive elements (101); a slit collimator (104) which selects energy ray column to be acquired at a time; and a controller (105) which controls the motion of the slit collimator (104) from a start position to an end position, to stop at every column and acquire image data of an exposed energy ray sensitive column at a time, wherein the sequence of acquiring columns of images forms a two- dimensional image.

2. An image scanning device according to claim 1, wherein the energy ray sensitive elements (101) are photo sensitive materials to acquire visible light image.

3. An image scanning device according to claim 1, wherein the energy ray sensitive elements (101) are thermal sensitive materials to acquire infrared image.

4. An image scanning device according to claim 1, wherein the slit collimator (104) is controlled to have a motion perpendicular to the lens array (103).

5. An image scanning device according to claim 1 , wherein the controller (105) allows the selection of a start and end position.

6. An image scanning device according to claim 1 , further comprising a filter (302) to select energy ray with spectrum of interest.

7. An image scanning device according to claim 1, wherein the slit collimator (304) has a slit aperture size similar to the energy ray sensitive material (305).

8. An image scanning device according to claim 1 , further comprising a reader (306) to read signals of a single column of image data.

9. A method to form image comprising the steps of: initializing a slit collimator to a home position (501 ); clearing reader memory; checking if area of interest is selected (502), whereby if the area of interest is not selected, than selection of a start and end position for the slit collimator (504) is performed, and whereby if the area of interest is selected or the start and end position is defined, than exposure of a column of sensor by the slit collimator (506) is performed; exposing the sensor for light collection (508); acquiring and sending signals of a column from sensor to reader memory (510); checking if end position of slit aperture is reached (512), whereby if the end position of slit aperture is not reached, moving the slit aperture to the next column and the process of exposing the said column and sending signals from sensor to reader is repeated for the said column (514), and if the end position of slit aperture is reached, scanning a two dimensional image (516), wherein the sequence of acquiring columns of images forms a two- dimensional image.