JPH0423986B2 - - Google Patents

Description

[Detailed description of the invention] B. Purpose of the invention [Industrial application field] The present invention relates to an image reading device.

More specifically, the present invention relates to an image reading apparatus that converts an image to be read into an electrical signal (time-series electrical pixel signal) using a one-dimensional or two-dimensional image sensor such as a CCD array, and then performs reading processing.

[Conventional technology]

Image reading apparatuses of this type are well known, and FIG. 3 shows, as an example, a very schematic configuration of an apparatus for reading and processing required frame image information on a microfilm.

Reference numeral 1 denotes a film frame illumination section, and the illumination section automatically searches (not shown) three required film frames to be read and processed in the film 2 (roll microfilm, microfissure film, microstrip film, etc.). Located by mechanism or by manual search. 4 is the film frame 3
This is an illumination system that illuminates the area from below, and the illumination light transmitted through the film is imaged on the light receiving surface of the image sensor 6 via the projection optical system 5. When the image sensor 6 is a two-dimensional image sensor, the entire image formed is read and processed as time-series electrical pixel signals by the sensor's own electrical main scanning/sub scanning mechanism. When the image sensor 6 is a one-dimensional image sensor, an electric main scanning mechanism along the length of the sensor 6 and a mechanical relative sub-scanning movement between the sensor 6 and the film frame 3 cause the entire image to be formed. It is read and processed as a time-series electric pixel signal.

A time-series electrical pixel signal, which is an image reading signal outputted from the image sensor 6, is input to an image reproducing device or recording device (not shown) such as a laser beam printer mechanism, display device, facsimile receiving device, etc., and is inputted into an image reproducing device (not shown) or a recording device, etc., which corresponds to the read image. Images are reproduced or stored.

[Problem that the invention seeks to solve]

By the way, in this type of image reading apparatus, the image reading signal level output from the image sensor 6 is the same for each image to be read, regardless of the difference in image density level and base density level of each image to be read. The amount of illumination light for each image to be read is automatically controlled so as to maintain an approximately constant appropriate output level throughout.

Specifically, in the reading processing cycle of each image to be read, the illumination system 4 illuminates the image 3 to be read with a preset standard illumination light intensity, and the image sensor 6 reads the image with that light intensity. let This image reading process is called pre-reading. The control circuit compares the image reading signal level output from the image sensor 6 in this pre-reading process with a reference signal level, and automatically corrects and controls the illumination light amount of the illumination system 4 to an appropriate illumination light amount based on the comparison. Thereafter, the image sensor 6 reads the image 3 to be read illuminated with the appropriate illumination light amount after the correction (normal reading process of the image to be read), and inputs the read signal to a reproduction device or the like. It is something.

However, this had the following problems.

That is, there are images to be read that are in a base density state where the image sensor 6 is saturated (outside the sensitivity range), and in such cases, the image is read with a preset constant reference illumination light amount. The illumination becomes inappropriate (excess/deficiency of illumination light amount), and the automatic correction control of the image illumination light amount by the above-mentioned pre-reading is not performed properly.

The present invention aims to solve the above problems.

B. Structure of the Invention [Means for Solving Problems] The present invention provides an illuminating means for illuminating an image to be read, a projection imaging optical system for projecting the image to be read, a projection observation plate for the image to be read, and a projection viewing plate for projecting the image to be read. an image sensor that converts the formed image to be read into an electrical signal and reads it;
an optical path switching movable mirror that normally sets the projection optical path of the projection optical system to the projection observation plate side and switches the optical path to the image sensor side by operating in response to a read command signal; A light receiving sensor receives the image light to be read based on the reference illumination light amount from the mirror in the optical path switching operation process, and a pre-reading process of the image to be read by the image sensor based on the light amount of the image to be read detected by the light receiving sensor. A control circuit system that determines the appropriate amount of illumination light at the time and corrects the amount of image illumination of the illumination means to the determined amount of light, and an image reading signal output from the image sensor during the pre-reading process with the corrected amount of image illumination. a control circuit that determines an appropriate amount of illumination light during a normal reading process of the image to be read by the image sensor based on the level, and re-corrects the amount of image illumination light of the illumination means to the determined light amount; The gist of the present invention is an image reading device characterized by the following features.

[Effect]

That is, with the above configuration, the image illumination light amount of the illumination means is adjusted so that the illumination light amount of the image to be read in the pre-reading process of the image to be read is individually appropriate depending on the image condition of the image to be read. Correction is automatically controlled. Therefore, even if the image to be read is in an image state that is outside the sensitivity range of the image sensor, pre-reading of the image to be read is always performed in a state of appropriate light amount.

〔Example〕

FIG. 1 is a very schematic block diagram of an embodiment of the apparatus of the present invention, and FIG. 2 is a block diagram of an example of a control circuit. Components common to those in the device shown in the example shown in FIG. 3 are designated by the same reference numerals and will not be described again.

In the figure, 7 is a projection observation plate (opalescent plate, etc.) for checking the image to be read, and 8 is a movable mirror that can rotate freely around axis 9. It is held in a first position in which it intervenes in the optical path of the image optical system 5 at an angle of 45 degrees, and in this position, the image light to be read from the optical system 5 is directed toward the observation plate 7 by the lower surface of the mirror 8. After being reflected and deflected, the read image 3 of the illumination section 1 is projected onto the observation plate surface. When an image reading signal is input to the control circuit, the mirror 8 is rotated clockwise about a shaft 9 by a drive mechanism (not shown), and the mirror 8 is rotated clockwise to a point indicated by a chain double-dashed line which escapes from the optical path of the projection imaging optical system 5. It is held in the second position. In this attitude, the image light to be read from the optical system 5 is projected onto the light receiving surface of the image sensor 6 to form an image.

A light receiving sensor 10 receives image light to be read from the mirror through the slit 11a of the slit plate 11 and the diffuser plate 12 during the rotation operation process in which the mirror 8 is switched from the first attitude to the second attitude. The slit plate 11 functions to improve the accuracy of light reception.
The diffuser plate 12 functions to illuminate the light receiving sensor 10 with the average amount of image light to be read. The light receiving sensor 10 used has a dynamic range, that is, a ratio of the minimum amount of received light to the maximum (saturated) amount of received light, which is larger than that of the image sensor 6.

Next, the control system will be explained.

(1) During the rotation process of the movable mirror 8 from the first attitude to the second attitude in response to an image reading command signal, the light receiving sensor 10 detects the image density level of the image to be read based on the reference illumination light amount and the base density level. The averaged amount of light is received, photoelectrically converted, and amplified by the amplifier circuit 13.

(2) The amplified signal is digitally converted by the A/D converter 14 and input to the comparison/arithmetic circuit 15.

(3) This comparison/calculation circuit 15 performs a comparison with a reference level value, and calculates and determines the appropriate amount of illumination light during the pre-reading process of the image 3 to be read by the image sensor 6.

(4) The dimming control circuit 16 of the illumination means 4 is controlled by the output of the calculation result, and the amount of illumination light of the illumination means 4 is corrected to the amount of light determined by the above calculation.

(5) Then, the image sensor 6 performs forward scanning of the image to be read using the corrected illumination light intensity.

(6) The image reading signal output from the image sensor 6 in the pre-reading process is input to the amplifier circuit 17 and amplified.

(7) The amplified signal is digitally converted by the A/D converter 18 and input to the comparison/arithmetic circuit 19.

(8) This comparison/calculation circuit 19 performs a comparison with a reference level value, and calculates and determines the appropriate amount of illumination light during the regular reading process of the image to be read by the image sensor 6.

(9) The dimming control circuit 16 of the illumination means 4 is controlled by the output of the calculation result, and the amount of illumination light of the illumination means 4 is re-corrected to the amount of light determined by the above calculation.

(10) Then, the image sensor 6 performs normal image reading of the image to be read using the above-mentioned re-corrected illumination light intensity, and the read signal is input to the control circuit of the image reproduction device (not shown). .

(11) When the normal image reading process is completed, the movable mirror 8 is changed to the first attitude by the signal, and the illumination means 4 is returned to the initial reference illumination light amount state.

C. Effects of the Invention As described above, the present invention corrects the image illumination light amount during the pre-reading process to an appropriate light amount according to the image condition of the image to be read, so that image reading processing is always performed in an appropriate state. executed.

[Brief explanation of drawings]

FIG. 1 is a very schematic block diagram of an embodiment of the apparatus of the present invention, FIG. 2 is a block diagram of a control circuit system, and FIG. 3 is a very schematic block diagram of a conventional apparatus. 3 is a microfilm frame image as an image to be read, 4 is an illumination means, 5 is a projection optical system, 6 is an image sensor, 7 is an observation plate, 8 is an optical path switching mirror, and 10 is a light receiving sensor.

Claims (1)

[Scope of Claims] 1. An illumination means for illuminating the image to be read, an imaging optical system for projecting the image to be read, an observation plate on which the image to be read is projected, and an image to be read projected on the light receiving surface. an image sensor that converts into an electrical signal and reads it; an optical path switching movable mirror that normally forms a projection optical path of the imaging optical system on the observation plate side and switches it to the image sensor side in response to a reading command signal; a light-receiving sensor that receives image light to be read based on a reference illumination light amount from the mirror during the optical path switching operation process from the observation plate side to the image sensor side; A control circuit system that determines an appropriate amount of illumination light during a pre-reading process using an image sensor and corrects the image illumination light amount of an illumination means to the determined light amount; Control for determining an appropriate amount of illumination light during a regular reading process of the image to be read by the image sensor, based on the image reading signal level output from the image sensor, and re-correcting the amount of image illumination of the illumination means to the determined light amount. An image reading device comprising: a circuit;