Image reading device

Abstract: This invention provides an image reading device capable of precise detection of the optical signal over a wide wavelength range, by forming a photoelectric converting unit for converting the visible light into an electrical signal and a photoelectric converting unit for converting the invisible light into an electrical signal, in monolithic manner on a single semiconductor chip.

Description: The present invention relates to an image reading device adapted for use in an image forming apparatus such as a facsimile, an image scanner, a copying machine or the like, and more particularly to an image reading device and a photoelectric converting element capable of converting optical signals not only of visible spectral region but also of invisible spectral region into electrical signals. From WO 91/03031 is known a method and a means for checking genuineness of paper money which are based upon detection of characteristic difference in the printing process for genuine bank notes and counterfeit bills produced with a color copying machine. The detection is conducted in narrow wave length bands respectively in typical red and blue color ranges and simultaneously in particular directions, with reflected and scatted light. Detection of intensity in a correspondingly narrow band near the maximum sensitivity range of the eye, e.g. in the green range, and in another direction, is also conducted for reference purposes. Preferably the measurement is made in a particularly selected point where the contents of blue and red in the print of the genuine bank note is at an extreme, e.g. high or low. US-A- 4 146 792 discloses a device for checking the authenticity of valuable paper which is secured against forgery. The device includes a light source for exciting fluorescent substances on the paper to fluoresce in the visible, resp. invisible spectral range. The light emitted by the fluorescent paper is focussed on an arrangement of like photocells so that each of the photocells is struck by monochromatic light only, and each photocell measures the fluorescence of the paper at a different wave length. In the field of image reading device, there are already known a charge-coupled device (CCD), a MOS device and an amplifying device formed by connecting a capacitative load to the emitter of a phototransistor, as disclosed in the U.S. Patent No. 4,791,469 granted to the inventors T. Ohmi and N. Tanaka. Also there are recently conceived various applications, and image reading devices having novel functions are being required. For example the copying machine is required, in addition to the improvement in image quality and the color image reproduction, to have the ability to recognize, reproduce and record an invisible image to the human eyes. An example of such invisible image is the image formed with ink absorbing infrared light. In general, the sensor for detecting the invisible light is an individual device, and requires a new design concept for effecting image detection, in combination with a sensor for detecting the visible light. As a basic design concept, the present inventors already found a technology of incorporating a sensor for visible light detection and a sensor for invisible light detection in a single semiconductor chip. However, said technology still has a room for improvement. On the other hand, the image quality improvement and the color copying capability of the copying machine has brought the danger of forgery of bandnotes, stamps, valuable securities etc. into reality. For this reason, in the recognition of banknote or the like, there have been devised various methods such as detection of the stamp pattern on the banknote. Also utilizing the fact that the pattern of the original image is formed with certain color hues, the present applicant already proposed a method of recognizing the banknote etc. from the color hue of said original pattern. Also certain banknotes enable recognition of the true one and the false one, by printing a predetermined mark with fluorescent ink which emits the visible light when irradiated with ultraviolet light. Also for forming such predetermined mark, the use of ink capable of absorbing the infrared light was also proposed by the present applicant. In such infrared light detecting device, the Japanese Patent Application Laid-open No. 4-286350 of which U.S. counterpart is U.S. Serial No. 139174 entitled "Image Processing Apparatus and Method Therefore" filed on October 21, 1993 proposing to achieve making compact of the device and easy optical adjustment by a monolithic structure of a sensor for ordinary color image formation and a sensor for infrared light detection, thereby enabling to use a common optical system. However, such conventional system is difficult to design in common for plural valuable securities, because a visible pattern is the target of recognition. Therefore, for distinguishing the valuable securities of N kinds, it has been necessary to select the features of N kinds in advance and to independently recognize each security, and it has been difficult to realize such apparatus inexpensively. Also a CCD sensor for reading the images of visible and infrared regions by separating the spectral regions additionally requires, in comparison with the conventional sensor, an optical filter for reading the infrared light and an increased number of elements or lines of the sensor, whereby the sensor itself and the post-processing system therefor become complex and a decrease in the light-receiving area of the sensor or an increase in the size of the sensor is unavoidable. Also, since the sensor elements for the visible light and those for the infrared light are arranged on a same plane, at least one of the sensors may become out of focus, due to the difference in the focus position. Also in case of using such sensors for respectively reading the infrared information and the visible information, it becomes necessary to clearly separate the visible information and other information. Furthermore, for obtaining a satisfactory resolving power on a monolithic CCD sensor over a wide spectral range from visible to near-infrared region or from visible to near-ultraviolet region, there is required a significantly increased number of lenses, leading to an increased cost and a larger space of the device. Also in an optical system employing a short-focus lens array, it has been impossible to maintain a constant resolving power over a wide spectral range, because such lens array is composed of single lenses. Also the conventional image reading device employed in the office equipment such as copying machine is composed for example of a CCD or a MOS sensor requiring a long optical path, or a contact image sensor employing amorphous silicon, and such image reading device is sometimes combined with color filters for the color image reproduction. However, such photoelectric converting device combined with filters is not necessarily superior, in terms of spectral sensitivity and resolving power for infrared light detection, to the device for visible light detection, and still has a room for improvement. In consideration of the foregoing, the object of the present invention is to provide a compact image reading device capable of detecting the optical signal over a wide spectral range from visible to invisible region, and not giving much burden on the designing of the optical system. The above-mentioned object can be attained, according to the present invention, by an image reading device according to claim 1. The invention is further developed by the features mentioned in the subclaims. Fig. 1 is a schematic cross-sectional view of an embodiment 1-1 of the image reading device of the present invention; Fig. 2 is a chart showing spectral characteristics of color filters to be employed in the present invention; Fig. 3 is a chart showing spectral characteristics of a visible light cut-off filter to be employed in the present invention; Fig. 4 is a chart showing light emission characteristics of a light source to be employed in the present invention; Figs. 5A and 5B are schematic views of the embodiment 1-1 of the image reading device of the present invention; Fig. 6 is a schematic view of a pixel of the embodiment 1-1 of the image reading device; Fig. 7 is a chart showing spectral characteristics of infrared absorbing paint to be employed in the present invention; Fig. 8 is a chart showing spectral characteristics of a far-infrared cut-off filter to be employed in the present invention; Figs. 9A and 9B are schematic views of an embodiment 1-2 of the image reading device of the present invention; Figs. 10A and 10B are schematic views of an embodiment 1-3 of the image reading device of the present invention; Fig. 11 is a schematic view showing an example of the image information processing apparatus of the present invention; Fig. 12 is a schematic view of an original image to be read by the image reading device of the present invention; Fig. 13 is a schematic view showing the reading operation of the image reading device of the present invention; Fig. 14 is a block diagram showing a signal processing unit of the image reading device of the present invention; Fig. 15 is a block diagram of an edge enchancing circuit of the image reading device of the present invention; Fig. 16 is a schematic view of a pixel data map; The image reading device of the present invention is featured by a fact that the light-receiving face of the sensor for visible light and that of the sensor for invisible light are made respectively different for the direction of the incident light, but the planar positions (positions in a plane perpendicular to the incident direction) of said sensors are not particularly limited. However, in case of a line sensor, the sensor array for visible light and that for invisible light are preferably constructed as separate lines. Also in the sensor array for visible light, the sensor elements for red (R), green (G) and blue (B) or the sensor elements for yellow (Y), cyan (C) and magenta (M) may be positioned in an in-line arrangement or may be arranged to constitute three parallel lines. Fig. 1 is a schematic cross-sectional view of the image reading device of the present invention, wherein a sensor 2 for visible light has a light-receiving face 2' which is different from that 3' of a sensor 3 for invisible light. The photoelectric converting elements (sensor elements) constituting the light-receiving face of the present invention are advantageously composed of photo-voltaic elements or photoconductive elements such as photodiodes or phototransistors. The photoelectric converting elements for converting the optical signal of the visible region into the electric signal may be constituted by the elements composed of a material capable of selectively absorbing the optical signal of the visible region only, or by the elements provided with a filter capable of transmitting the light of visible region but intercepting the light of a spectral region to be utilized for photoelectric conversion in other photoelectric converting elements, among the invisible region. More specifically, for obtaining a black-and-white signal, there is attained selective sensitivity in the visible wavelength region from 400 to 700 nm, by selecting the material constituting said elements or by providing the elements with a filter selectively transmitting the light of the above-mentioned wavelength region. Also the optical signal of a specified region within the visible spectral region may be obtained by constructing said elements with a material selectively having sensitivity in said specified region, or by providing the elements with a filter capable of transmitting the light of said specified spectral region. Also for obtaining color signals, such as of red (R), green (G) and blue (B), there are employed elements of plural kinds, consisting of elements (R elements) having selective sensitivity in the R region (spectral region for example from 580 to 700 nm), elements (G elements) having selective sensitivity in the G region (spectral region for example from 480 to 580 nm), and elements (B elements) having selective sensitivity in the B region (spectral region for example from 400 to 480 nm). Also in this case, there may be employed elements composed of materials having selective sensitivities in, namely capable of selectively absorbing the lights of the above-mentioned R, G and B regions, or provided elements having sensitivity in all the R, G and B regions with filters selectively transmitting the lights of said R, G and B regions respectively. Alternatively, a position of a semiconductor junction such as a PN junction of the photodiode or the phototransistor may be varied to obtain a selective sensitivity. Fig. 2 is a chart showing the representative spectral characteristics of the light transmitted by the filters, wherein the relative sensitivity in the ordinate corresponds to the transmittance for the visible light. In case the elements are given the selective sensitivities by the selection of the constituting materials, the elements are formed with the materials having the light absorbing characteristics corresponding to the relative sensitivities shown in Fig. 2. In the present invention, any of the visible and invisible spectral regions, and the R, G and B spectral regions are not clearly distinguished by the wavelength, but the photoelectric converting elements to be employed therein need only to be so constructed as to photoelectrically convert the ultraviolet, blue, green, red and/or infrared lights by a necessary amount and substantially not to convert the unnecessary lights, in order to obtain the required signals. On the other hand, for converting the optical signal of the invisible spectral region into the electrical signal, there are employed cphotoelectric converting elements having selective sensitivity for example for the ultraviolet light or the infrared light. Also in this case there may be employed elements composed of a material having selective sensitivity in said invisible spectral region, or elements composed of a material having sensitivity in a wide spectral range including said invisible spectral region, composed with a filter having selective transmittance for the light of said invisible spectral region. Fig. 3 is a chart showing representative spectral characteristics of the above-mentioned filter, wherein the relative sensitivity in the ordinate corresponds to the transmittance for the invisible light. There is shown an example of filter having selective sensitivity in the infrared region (wavelength region for example above 750 nm), but such example is not limitative. The solid-state image reading device of the present invention may be constructed as a color line sensor as shown in Fig. 1, in which the elements for visible light and those for invisible light are periodically arranged in mutually separate lines. Preferably it is so constructed that a pixel in terms of the resolving power of the color signal contains an element (R element) having selective sensitivity in the R region, an element (G element) having selective sensitivity in the G region, an element (B element) having selective sensitivity in the B region, and an element (IR element) having selective sensitivity in the invisible region. The optical signal to be detected may be generated from a three-dimensional image or a two-dimensional image, and a representative example of said two-dimensional image is a flat image such as an original document. Consequently, in case of use in a system for reading the image of an original document, there is preferably provided illumination means for illuminating the original. Such illumination means may be composed for example of a light-emitting diode, a xenon lamp or a halogen lamp. Fig. 4 shows representative light emission spectral characteristics of the light source. However the light source needs only to emit the light of a spectral region required corresponding to the optical signal to be detected, and is not limited to that having the characteristics shown in Fig. 4. A light source emitting the light of the characteristics shown in Fig. 4 can at least provide the light in the R, G and B regions and the infrared light in the invisible spectral region. In the following there will be explained embodiments of the present invention, but it is to be understood that the present invention is not limited to these embodiments but can be realized in any form attaining the objects of the present invention. (Embodiment 1-1) Fig. 5A is a plan view, seen from above, of a CCD 1 serving as the image reading device, and Fig. 5B is a cross-sectional view thereof. The CCD 1 is composed of a first element array 100 and a second element array 101. In the first element array 100, the elements are cyclically provided with R filters 102, G filters 103, and B filters 104, formed by evaporation, in the order of R, G, B, R, G, B,.... thereby constituting a reading system in which a pixel 105, consisting of a set of three elements of R, G and B, constitutes a minimum reading area. The filters provided by evaporation on respective elements have the spectral characteristics as shown in Fig. 2. On the other hand, in the second element array 101, the elements are arranged with a pitch equal to three times of the pitch of the elements in the first element array 100. Stated differently, the element pitch of the second array 101 is same as the pixel pitch of the first element array 100. The second element array 101 is provided, by evaporation, with a visible light cut-off filter of the characteristics shown in Fig. 3, so that the light components less than 700 nm are cut off and the element array 101 can read the infrared component. Also, as shown in Fig. 5B, the second element array 101 has a step difference d of 300 µm to the first element array 100, for obtaining a longer optical path. This is because the focal length of the optical system varies depending on the wavelength, and the image becomes out of focus for the infrared light unless the optical path is made longer. Fig. 6 shows the dimension and the positional relationship of the elements of the first element array 100 and the second element array 101. It is assumed that the reading unit has a resolving power of 400 dpi and that, for the purpose of simplicity, an equal-size optical system is employed. For realizing the resolving power of 400 dpi, the minimum reading area becomes 63.5 x 63.5 µm. Consequently the size of the R, G and B elements becomes 21.1 x 63.5 µm, while the IR elements becomes 63.5 x 63.5 µm. The distance between the first and second element arrays is selected as 127 µm. Stated differently, said arrays are separated by a distance corresponding to twice of the array 100 or 101. The signals read by the arrays 100, 101 are so controlled as to be transmitted to a signal processing unit 211. (Embodiment 1-2) In this embodiment, the element array 101 can read the signal in a spectral region exceeding 700 nm, but the infrared absorbing paint has a spectral distribution having an extremely narrow band width, with a peak at 800 nm, as shown in Fig. 7. However, depending on the light source to be employed, there may be provided enough energy even in a region exceeding 1000 nm. If such light source is employed, the discrimination of absorption becomes difficult because of the unnecessary energy above 800 nm. For this reason, the element array 101 is preferably provided with a far infrared cut-off filter of the characteristics as shown in Fig. 8. Said far infrared cut-off filter may be provided in any position in the optical path, because, in the element array 100, the far infrared light is already cut off by a filter evaporated on the surface of the elements. For example, said filter may be conveniently positioned in front of or behind a lens 209, because the filter can be easily replaced when the fluorescent characteristics of the fluorescent paint to be printed on the original document is varied. (Embodiment 1-3) In the foregoing embodiments, the color sensor is constructed as shown in Figs. 5A and 5B. In the present embodiment, the substrate of the CCD is formed in an inclined shape as shown in Figs. 9A and 9B, in such a manner that the first line 100 and the second line 101 has a optical path difference d of 300 µm. In this manner the visible optical signal and the infrared optical signal are both in focus, so that the precision of discrimination becomes improved. Also as a variation of this embodiment, a similar effect can be obtained by placing planar CCD sensors in an inclined position. (Embodiment 1-4) In this embodiment, a color sensor consisting of an array 171 having sensitivity to blue, an array 172 having sensitivity to green, an array 173 having sensitivity to red and an array 174 having sensitivity to infrared region is given step differences, matching the focal positions of respective colors. There are preferably provided a step difference d1 of 20 µm between B and G, a step difference d2 of 50 µm between G and R, and a step difference d3 of 280 µm between R and IR. These values depend on the optical system to be employed, and are preferably optimized according to each optical system. The presence of four CCD lines requires phase matching of all the color signals with a FIFO memory. Also as modifications of this embodiment, it is possible to form the substrate in inclined manner or to place a planar sensor in inclined manner. In this manner the visible optical signal and the infrared optical signal are both in focus, so that the precision of discrimination can be improved. Also the distance between the array of the infrared component reading elements and the array of the visible component reading elements, selected as an integral multiple of the resolving power of the reading system, enables electrical compensation of said difference for example by a line buffer, and facilitates comparison of the signals from the two element arrays which read a same image area. It is furthermore possible to dispense with said line buffer, by utilizing the FIFO memory for example in an edge enhancing circuit. (Image Information Processing Apparatus) In the following there will be explained a representative example of the image information processing apparatus equipped with the image reading device, according to any of the foregoing embodiments of the present invention. (Structure of Image Scanner Unit) In Fig. 11 there are shown an image scanner unit 201 for reading the original image and effecting digital signal processing, and a printer unit 202 for printing a full-color image on a sheet, corresponding to the original image read by the image scanner unit 201. In the image scanner unit 201, there is provided a mirror-surface thick plate 200. An original 204 placed on an original supporting glass (hereinafter called platen) 203 is illuminated by a halogen lamp 205, and the reflected light from the original is focused, by a lens 209, on said color sensor 1 serving as the image reading device, whereby the full-color signals of the red (R), green (G), blue (B) and infrared (IR) components are supplied to a signal processing unit 211. A reading unit 207 is mechanically moved, with a velocity v, in a perpendicular direction (hereinafter called sub scanning direction) to the electrical scanning direction (hereinafter called main scanning direction) of the color sensor, thereby scanning the entire surface of the original. The signal processing unit 211 electrically processes the read signals to separate the components of magenta (M), cyan (C), yellow (Y) and black (BK), for supply to the printer unit 202. (Structure of the Printer Unit) The image signals M, C, Y, BK supplied from the image scanner unit 210 are supplied to a laser driver 212, which in response modulates a semiconductor laser 213. The laser beam emitted therefrom is guided through a polygon mirror 214, an f- lens 215 and a mirror 216 and scans a photosensitive drum 217. A rotary developing unit 218 is composed of a magenta developing unit 219, a cyan developing unit 220, a yellow developing unit 221 and a black developing unit 222, which in turn come into contact with the photosensitive drum to develop the electrostatic latent images of M, C, Y and BK formed on the photosensitive drum 217 with corresponding toners. A sheet supplied from a sheet cassette 224 or 225 is wound on a transfer drum 223, and the toner images developed on the photosensitive drum 217 are transferred onto said sheet. After the successive transfers of the four color images of M, C, Y and BK in this manner, the sheet is discharged through a fixing unit 226. In the foregoing there has been briefly explained the structure of the scanner unit and the printer unit principally constituting the apparatus, and in the following there will be given a detailed explanation on the image scanner unit 201. (Original) Fig. 12 shows an original 630 on which a pre-registered pattern 631 is printed with infrared absorbing paint. In addition to the pattern 631, characters and images 632 are printed with ordinary ink on the original 630. The printed infrared absorbing paint, absorbing the infrared light having wavelength in excess of 700 nm, appears almost colorless to the human eyes sensitive to a spectral region of 400 - 700 nm, and is therefore extremely difficult to recognize. The spectral characteristics of said infrared absorbing paint is same as shown in Fig. 7. The amount of the above-mentioned infrared absorption can be detected by cutting off the visible light component and extracting the infrared light component only by the element array 101 in the sensor 1. (Pre-scan) The image scanner unit 201 effects a pre-scan, as a pre-treatment before the copying of the original 630, as will be explained in the following. At first the lamp 205 illuminates a white shading plate 640, fixed in a part of the platen 203 as shown in Fig. 13. The reflected image of said white shading plate 640 is focused, through the lens 209, onto the CCD 210. The image of the white shading plate 640, read by the element arrays 100, 101 of the sensor 1, is processed in the signal processing unit 211, and the data for compensating the unevenness in the illumination by the lamp 205, and the data for compensating the unevenness in the sensitivity of the element arrays 100, 101 of the sensor 1 are prepared and are stored for respective arrays. Subsequently the reading unit 207 is mechanically moved in a direction m with a velocity v by an unrepresented driving system, thereby scanning the entire surface of the original. In this operation, the signal processing unit 211 extracts the maximum and minimum values of the original density, from the image of the original 630 read by the element array 100 of the sensor 1, and calculates the print density at the copying operation. Thereafter the reading unit 207 is mechanically moved in a direction n shown in Fig. 13 with a velocity v by the unrepresented driving system, for returning to the reading start position, or, the home position. (Copying of Original and Pattern Detection) After the preparation of the above-mentioned shading correction data, the reading unit 207 returns to the home position and starts the reading of the original 630. At the same time there is detected whether the original 630 has the pattern 631. The presence or absence of the pattern is discriminated by the comparison of the information read by the element array 100 of the sensor 1 and that read by the element array 101. More specifically, the image reading for image reproduction is conducted by the element array 100, while the image reading for detecting the pattern 631 is conducted by the element array 101. In the following there will be given an explanation on the signal processing unit 211 for processing the read signals. The block diagram of said unit 211 is shown in Fig. 14. At first there will be explained the signal processing system for the element array 100. The analog image signals released from the element array 100 are entered, in the order of R, G and B and in synchronization with the drive signal for the sensor 1, simultaneously to three sample-hold circuits 121a - 121c. The sample hold circuit 121a generates a sampling signal at the timing of entry of the R signal, and is capable of retaining the analog level of the sampled signal until a next R signal is entered. Similarly the sample-hold circuit 121b generates a sampling signal at the timing of entry of the G signal and the sample-hold circuit 121c generates a sampling signal at the timing of entry of the B signal. As a result, the sample-hold circuits 121a - 121c respectively release the R, G and B signals, which are respectively supplied to A/D converters 122a - 122c, wherein the analog image signal is converted into an 8-bit digital image signal. The obtained digital signals are supplied to shading correction circuits 124a - 124c, for being subjected to shading correction. The shading correction has already been explained in relation to the pre-scanning, and the correction data for R, G and B colors prepared therein are stored in a RAM 123. During the image reading, the correction data for each element are supplied from the RAM 123 to the shading correction circuits 124a - 124c, thereby correcting the read data. The image signals released from the shading correction circuits 124a - 124c are supplied to a 5 x 5 edge enhancing circuit 125, which emphasizes the contour of the read image in the following manner. Fig. 15 shows the structure of said edge enhancing circuit 125. The edge enhancement is conducted for each of the R, G and B colors, but Fig. 15 shows the circuit for one color only. Naturally other two circuits have the identical structure. In Fig. 15 there are provided FIFO memories 131 - 134 each having a capacity capable of retaining the data of a line in the element array 100 of the CCD 210. The four FIFO memories are connected as shown in Fig. 15, so that, when the pixel data of an n-th line are entered to the FIFO 131, the FIFO memories 131, 132, 133, 134 respectively release the data of an (n - 1)-th line, an (n - 2)-th line, an (n - 3)-th line and an (n - 4)-th line. The input signal and the output signals of the FIFO memories 131 - 134 are supplied to a delay circuit 135. Said delay circuit 135 is provided with several pixel delaying circuits for the entered signal of m-th pixel, thereby providing an arithmetic operation circuit 136 with the pixel data of the (m - 1)-th, (m - 2)-th, (m - 3)-th and (m - 4)-th pixel as well as the m-th pixel. Thus the circuit 136 receives the data of 25 pixels in total. Fig. 16 shows the map of the entered data. Thus the operation unit 136 receives the data of the surrounding 24 pixels together with the data of a hatched object pixel. The operation unit 136 multiplies the data of the object pixel by 25, and subtracts the data of the surrounding pixels. Thus, if the data of the object pixel is larger than the data of the surrounding pixels, the data of the object pixel becomes even larger, and vice versa. This process increases the contrast of the contour of the image, thus enhancing the reproduced image. The edge enhanced image data are supplied, through a logarithmic conversion unit 127 for effecting luminance-density conversion, and a masking conversion unit 128 for effecting optimum correlated color correction, to the printer unit. In the following there will be explained the signal processing system for the element array 101. Although it is basically same as that for the element array 100, but the edge enhancing circuit is eliminated because the image reproduction is not the object. The data released from a shading correction circuit 124d are supplied to a signal comparison circuit 126. Other input data are obtained from the edge enhancing circuit, but, as will be apparent from Fig. 6, the object pixel in the edge enhancing circuit is present on the (n - 2)-th line. The comparison of the data of the arrays 100, 101 would require a line buffer for compensating the distance of two lines as shown in Fig. 6, but the edge enhancement on the data of the array 100 provides the data corresponding to a same position on the original. The signal comparison circuit 126, serving as the discrimination means, compares the image data of the arrays 100, 101 and sends the result of comparison to an unrepresented CPU. In the signal comparison, it is to be noted that the printing ink of a high density and a low saturation tends to contain pigment of carbon black family, and such ink, absorbing the infrared light, has to be separated from the information to be discriminated. In the present embodiment, therefore, whether the IR absorption pattern corresponds to the pattern to be discriminated is identified by the comparison of the minimum value K of the R, G and B signals and the IR signal in the following manner: X = IR - const. x min(R, G, B). More specifically, the value X is determined for each pixel and is cumulatively added for the entire original, and when the cumulative value reaches a predetermined reference level, the unrepresented CPU functions as the control means for the image forming operation and controls the printer unit so as to immediately interrupt the copying of the original. There can be conceived certain variations in the image information processing apparatus explained above. For example the line position correction for the element arrays 100, 101 need not necessarily utilize the FIFO memories of the 5 x 5 edge enhancing circuit, but may instead utilize the FIFO memories for example of the error diffusion process. Also the pattern discrimination is not necessarily limited to the signal comparison in the signal comparison circuit but may rely on pattern matching according to the image shape extracted by the signal comparison, in order to control the original copying operation. In this case there is required a large and complex pattern matching circuit, but, as the kind of the original can be identified from the pattern shape, there is enabled such control as to authorize the copying operation for certain originals in response to the entry of a password, but to prohibit the copying operation for other originals. This embodiment enables precise detection of the optical signal with a wide dynamic range and over a wide spectral range, without complicating the optical system.

Claims: An image reading device (1), wherein the light-receiving face (2') of a first sensor (2) for converting the optical signal of the visible region into a first electrical signal and that of a second sensor (3) for converting the optical signal of the invisible region into a second electrical signal are arranged in a staggered manner with respect to the direction of the incident light. The image reading device according to claim 1, wherein a step difference for obtaining optical paths of different lengths is provided between the light-receiving face of the first sensor and that of the second sensor. The image reading device according to claim 1, wherein said light-receiving face of the first sensor and that of the second sensor are formed on an inclined face of the substrate in the inclined shape. An image information processing apparatus comprising an image reading device according to one of claims 1 to 3, image forming means for forming an image based on said first electrical signal, discrimination means for effecting discrimination based on said second electrical signal and a reference signal, and control means for controlling the function of said image forming means based on the output of said discrimination means.

Inventors: ARIMOTO SHINOBU, HAYASHI TOSHIO, NAGASE TETSUYA, NAKAI TAKEHIKO, SASANUMA NOBUATSU, TANIOKA HIROSHI, UTAGAWA TSUTOMU, YOSHINAGA KAZUO, ARIMOTO, SHINOBU, HAYASHI, TOSHIO, NAGASE, TETSUYA, NAKAI, TAKEHIKO, SASANUMA, NOBUATSU, TANIOKA, HIROSHI, UTAGAWA, TSUTOMU, YOSHINAGA, KAZUO, ARIMOTO, SHINOBU, C/O CANON KABUSHIKI KAISHA, HAYASHI, TOSHIO, C/O CANON KABUSHIKI KAISHA, NAGASE, TETSUYA, C/O CANON KABUSHIKI KAISHA, NAKAI, TAKEHIKO, C/O CANON KABUSHIKI KAISHA, SASANUMA, NOBUATSU, C/O CANON KABUSHIKI KAISHA, TANIOKA, HIROSHI, C/O CANON KABUSHIKI KAISHA, UTAGAWA, TSUTOMU, C/O CANON KABUSHIKI KAISHA, YOSHINAGA, KAZUO, C/O CANON KABUSHIKI KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1993
Main classification: G07D7
IPC codes: H04N1, G07D7