JPH01290369A - Picture reader - Google Patents

Abstract

PURPOSE:To relax the effect of a minute foreign material on a film clipping pressing board by correcting luminous quantity based on an average luminous quantity data obtained from two positions or over in case of reading luminous quantity distribution. CONSTITUTION:The luminous quantity distribution is read by driving a carriage 9 with a pulse motor 13 in the absence of a film 2 between press boards and moving a projected image to an optional position. Luminous quantity correction coefficients alphai1-alphaino are obtained from the luminous quantity distribution read at optional plural positions and its mean value alphai is stored in the memory. When a start button is depressed, an aperture card 1 sticked to the film 2 is set to the carriage 9, the film 2 stored with picture information is clipped by transparent press boards and moved to a picture read position. The luminous quantity correction coefficient alphai is called from the memory corresponding to the picture element (i) and multiplied with an output signal Yi from a CCD 6 detected at the read position and the result is stored in a picture memory.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an image reading device that sandwiches a film between two pressure plates, projects the film image information onto a photoelectric conversion element, and performs scanning reading. The present invention relates to a device that corrects a scanning read signal based on the obtained light intensity distribution.

(Prior Art) Recently, image reading devices using photoelectric conversion elements have been widely used as input/output devices for facsimiles and computers. As one device for this method, a microfilm image is scanned by sandwiching a film between two pressure plates, irradiating it with a light source such as a halogen lamp, and projecting the film image onto a photoelectric conversion element through a projection lens. In this device where the reading device is located, the document is film, so the dynamic range of the read image signal is narrow and the light intensity distribution is not uniform over the entire surface of the film, so the light intensity distribution obtained with this optical system is Based on this, the output signal of the photoelectric conversion element is corrected.

To explain specifically, the image information (transmittance) of the film is xI, the light intensity distribution is 11%, the output signal of the photoelectric conversion element is Y,
Then, Y r QCX t ・Eng, ...■. Here, i is the pixel address of the photoelectric conversion element,
FIG. 7 shows that when the light intensity distribution Ii is not uniform on the photoelectric conversion element, even though the image information X of the film is -like,
This shows that the output signal YI is no longer uniform. This means that the true image information X+ of the film cannot be obtained from the output signal Y. Output signal Y of photoelectric conversion element
In order to obtain the true image information of the film from , the equation 0 may be modified to use the relational expression: Moreover, the formula (■) becomes as follows.

X I = α 1 ・ Y , ・・・■,
α Direct = A / I + ...■
Here, αi is a light amount correction coefficient, and A is a conversion constant for converting the output signal Yl into image information xl. In other words,
The true film image signal Xl can be obtained by multiplying the output signal Y1 of the photoelectric conversion element by the light intensity correction coefficient 01.

(Problem to be Solved by the Invention) However, in such a conventional example, when reading the light intensity distribution, the pressure plate surface that is in close contact with the film is imaged on the light receiving surface of the photoelectric conversion element. There is a problem in that a false light intensity distribution is known due to the influence of minute foreign matter adhering to the surface, and normal correction cannot be made to the read signal of the film image information.

Therefore, the present invention has been made to solve the above-mentioned problems of the conventional example, and its purpose is to provide an image reading device that can alleviate the adverse effects of minute foreign matter on the pressure plate and that can perform appropriate light intensity correction. Our goal is to provide the following.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, a film is sandwiched between two pressure plates, and is illuminated with a light source to form an image of film image information on a photoelectric conversion element. In an image reading device that reads a light amount distribution prior to scanning reading and performs scanning reading based on the light amount distribution, when reading the light amount distribution, based on the average value of light amount data obtained at at least two or more locations. It is configured by performing light amount correction using

(Function) In the present invention having the above configuration, when reading the light amount distribution, the light amount is corrected based on the average value of the light amount data obtained at at least two locations, so that minute foreign particles on the pressure plate can be detected. This is a mitigation of the impact.

(Example) The present invention will be explained below based on the illustrated example. 1st
The figure is a schematic perspective view of an image reading device to which an embodiment of the present invention is applied. Size: 28 mm x 39.6 mm) is attached. The film 2 is sandwiched between pressure plates (FIG. 2) which will be described later, and is illuminated by a lamp 3 and a condenser lens 4 as light sources. The projected image is formed via a projection lens 5 on the scanning plane of a CCD 6, which is a one-dimensional photoelectric conversion element. CCD6 has a light receiving element (pixel) of p=7
5000 bits are arranged in parallel at a μm pitch and have a length of 35 mm.

As shown in FIG. 2, the aperture card 1 is transported along the groove of the carriage 9 by a card transport system (not shown).
When the film 2 reaches the pressure plate 22 in the corner window provided near the center of the carriage 9, the conveyance force of the card conveyance system stops.
It has a structure in which the film 2 is held between pressure plates 22 and 23.

In addition, in FIG. 1, the carriage 9 has both ends of a wire 11 hooked to a hook 10, and the wire 11 is hooked to a boo 912 rotatably attached to a fixed shaft and a pulley 14 attached to the shaft of a pulse motor 13. is rotated, and is moved along the guide shaft 7.8 by the drive of the pulse motor 13. The pulse motor 13 is set to obtain the moving amount a of the carriage 9 with one pulse. Reference numeral 15 denotes a light shielding plate for detecting the home position of the carriage 9, and as the carriage 9 moves, the photosensor 16 is shielded from light. This light shielding position is the home position HPI of the film 2, and the rotation angle of the pulse motor 13 at this time is set to 0 pulses. The home position HPI here is the position where the CCD 6 starts reading image information on the film 2.

The projection magnification β, focal length f, and pupil diameter of the projection lens 5 are β = 1.1 times, f = 101 mm, and D = 18 mm.
Because it is designed for film images (28mm x 3
9.6 mm) is 28 mm in the direction of the CCD6 light receiving element row.
Imaged with a length of X 1.1 = 30.8 mm, 440
This is 0 bit information. Also, optical path length L=(β+1)
”f/β, distance between film and lens a=f (1+1/
β), distance between lens and CCD b = f (1 + β) is L =
404.9 mm, a = 192.8 mm.

b = 121.1 mm.

FIG. 3 shows the control system of the embodiment shown in FIG. 1, in which 40 is a controller consisting of a well-known microcomputer that performs overall sequence control for each component block, and 41 has a reading start button. A keyboard 42 is a memory for storing the control procedure shown in FIG. 5 according to this embodiment and a light intensity distribution read with no film between the pressure plates; 43 is an image memory that stores the light intensity distribution for the read image signal. The corrected image information is stored.

FIG. 4 shows the relationship between the scanning plane of the CCD 6 and the projection intensification 2' of the film 2 that is imaged on the scanning plane of the CCD 6. In the figure, HPI is the home position of the film 2, and the photo sensor 16 is This is the position where the light is blocked by the light shielding plate 15 and the signal is sent.

In the above configuration, the operation of this embodiment, which will be described according to the flowchart shown in FIG. 5, starts by turning on the power to the apparatus.

The light amount distribution is read (Sl) by driving the carriage 9 with the pulse motor 13 with no film 2 between the pressure plates.
The projected image 2' is moved in the direction of the arrow (see Fig. 4), and the pulse motor 1 is moved at an arbitrary position (within the area readable by the CCD 6) after the carriage 9 has passed the home position HP1.
3 and perform the first reading. The positional relationship between the projected image 2' and the CCD 6 at this time is shown in FIG.

In the figure, the numbers assigned to each pixel on CCDe indicate pixel addresses. By performing reading in this state, a light amount correction coefficient α is determined from the obtained light amount distribution using equation 0. Thereafter, the pulse motor 13 is driven, the projection position is changed, the light amount distribution is read a second time (SL), and the light amount correction coefficient αI2 is determined. When the number of light intensity readings reaches no=5 (S2), calculate the average value a1 of the light intensity correction coefficients (α11.α1□, . . . αInO) for each pixel (S3) and store it in the memory 42. (S4
).

Next, by pressing the reading start button on the keyboard 41 (S5) and notifying the controller 40, 86
The sequence from ~S10 is executed. That is, film 2
The aperture card 1 to which is pasted is set at a proper position on the carriage 9, and the film 2 on which image information is recorded is held between glass pressure plates 22 and 23 (S6). The film image is read from the home position HPI passing point of the carriage 9 by driving the pulse motor 13 (S
7) At this time, the output signal Yl from the CCD 6 is subjected to light amount correction based on equation 0 (S8). That is, correction can be performed by reading out the light amount correction coefficient α corresponding to the pixel i from the memory 42 and multiplying the output signal Yl from each pixel by matching the value. The corrected film image information is stored in the image memory 43 (S9).

Further, reading of the film image (28 mm x 39.6 mm) is executed from the home position HPI of the carriage 9, and at this home position HPI the pulse motor 13
The rotation angle of is reset to O pulse. Pulse motor 1
3 moves the film image by a by one pulse, so when the rotation angle of the pulse motor 13 reaches 39.6/a pulse, it is determined that the entire film image has been scanned and the process ends (SIO).

As explained above, in this embodiment, when reading the light intensity distribution, by averaging the light intensity distribution data obtained at five locations, the influence of minute foreign objects on the pressure plate surface can be alleviated, and the light intensity is closer to the true value than in the past. distribution can be obtained. This allows normal correction to be made to the film image information.

In the above embodiment, a one-dimensional photoelectric conversion element is used to read the image by film scanning, but the present invention applies whether CCD scanning is used as the scanning method or two-dimensional photoelectric conversion element is used. Included in invention. However, the light intensity distribution in these cases is not simply an average of data at several locations; it is necessary to calculate local average values at several locations throughout the film image, and then approximate the light intensity distribution across the film based on that data. There is. That is, in this case, since the light amount distribution changes over the entire film image, it is necessary to calculate a light amount correction coefficient of 0 for the corresponding portion from the averaged light amount data of several locations, and then apply correction based on that.

(Effects of the Invention) The image reading device according to the present invention has the above configuration and operation, and when reading the light amount distribution, it performs light amount correction based on the average value of light amount data obtained at at least two locations. As a result, the effects of minute foreign matter on the pressure plate can be alleviated and appropriate light amount correction can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of an image reading device to which an embodiment of the present invention is applied, FIG. 2 is a perspective view of main parts showing a film holding structure in the embodiment, and FIG. 3 is a control system of the embodiment. FIG. 4 is an explanatory diagram showing the relationship between the COD scanning plane and the projected image of the film in the same embodiment, FIG. 5 is a flowchart showing the operation of the control system in the same embodiment, and FIG. 6 is the same. 7 (a), (b), and (c) are explanatory diagrams showing the reading state of a COD film projection image in the embodiment. It is a graph diagram showing the relationship with YI. Explanation of symbols 2... Film 3... Lamp (light source) 5.
...Projection lens 6...CCD (photoelectric conversion element)

Claims (1)

[Claims] A film is sandwiched between two pressure plates, illuminated with a light source to form an image of the film image information on a photoelectric conversion element, and the light amount distribution is read prior to scanning reading, and scanning reading is performed based on the light amount distribution. An image reading device that performs the following: When reading the light amount distribution, light amount correction is performed based on an average value of light amount data obtained at at least two locations.