JPH0433464A - Original reader - Google Patents

Abstract

PURPOSE:To set an image sensor always following the optimum operating point of the sensor by controlling a luminous quantity from a light source so that the image sensor reaches the optimum operating point based on the saturating point. CONSTITUTION:An image sensor 9 detects a light radiated from a light source 7 and reflected on an original 1 and outputs a relevant signal. Moreover, a saturating point detection means 11 detects a saturating point of the image sensor 9. Then a light source control means 12 controls the luminous quantity radiated from the light source 7 so that the image sensor 9 reaches the optimum operating point based on the saturating point. Thus, an original reader to be set following the optimum operating point of the image sensor 9 at all times is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a document reading device using a CCD image sensor or the like.

[Conventional technology] The configuration of a conventional example will be explained with reference to FIG.

FIG. 6 is a block diagram showing a conventional document reading device.

In FIG. 6, the conventional document reading device includes a document table (2) on which a document (1) is placed, a reference white plate (3), a transparent reading reference white plate (4), and a document table (2). It consists of a transmission reading illumination lamp (5) provided above and an optical unit (6) provided below the document table (2).

The optical unit (6) is an illumination lamp (7) such as a fluorescent lamp.
, a light converging fiber lens (8), and a one-dimensional CCD
It is composed of an image sensor (9).

Next, the operation of the above-mentioned conventional example will be explained with reference to FIGS. 7 and 8.

FIG. 7 is a characteristic diagram showing the characteristics of the CCD image sensor, and FIG. 8 is a characteristic diagram showing the characteristics of the illumination lamp.

In FIG. 7, the horizontal axis shows the exposure amount, and the vertical axis shows the signal output level.

In FIG. 8, the horizontal axis represents ambient temperature and the vertical axis represents relative illuminance.

The entire document (1) is read by moving the optical unit (6) in the direction of arrow a.

However, there are variations in the characteristics of the CCD image sensor (9). For example, as shown in FIG. 7, the sensitivity of COD image sensor B is better, and the saturation level of C
CD image sensor A is more expensive. SA and SB indicate their respective saturation exposure amounts.

The operating point of the CCD image sensor (9) is shown in FIG.
In this case, when the CCD image sensor (9) is replaced with a CCD image sensor (9) having characteristics B due to maintenance or the like, the signal output level will be saturated. Moreover, in the opposite case, the S/N ratio of the output signal becomes poor.

Furthermore, the relative illuminance of the illumination lamp (7) changes depending on the ambient temperature, as shown in FIG. 8, so there is a similar problem.

[Problems to be Solved by the Invention] In the conventional document reading device as described above, the operating point of the CCD image sensor deviates from the optimum value due to variations in the characteristics of the CCD image sensor, illumination lamp, etc. and changes over time. There was a problem that the image quality deteriorated.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a document reading device that can always follow and set the optimal operating point of an image sensor.

[Means for Solving the Problems] A document reading device according to the invention of claim 1 is provided with the following means.

[1] An image sensor that detects light emitted from an illumination light source and reflected by a document and outputs a corresponding signal.

[2] Saturation point detection means for detecting the saturation point of this image sensor.

[3] Illumination light source control means for controlling the amount of light emitted from the illumination light source so that the image sensor reaches an optimal operating point based on the saturation point.

Further, the document reading device according to the invention of claim 2 is provided with the following means.

[1] An image sensor that detects light emitted from an illumination light source and reflected by a document and outputs a corresponding signal.

[2] Saturation point detection means for detecting the saturation point of this image sensor.

[3] Image sensor driving means for controlling the accumulation time of the image sensor so that the image sensor reaches an optimal operating point based on the saturation point.

[Operation] In the first aspect of the invention, the image sensor detects the light emitted from the illumination light source and reflected by the document, and outputs a corresponding signal.

Further, the saturation point of the image sensor is detected by the saturation point detection means.

Based on the saturation point, the illumination light source control means controls the amount of light emitted from the illumination light source so that the image sensor reaches an optimal operating point.

In the second aspect of the invention, the image sensor driving means controls the storage time of the image sensor so that the image sensor reaches an optimal operating point based on the saturation point.

[Embodiment] The structure of an embodiment of the invention of the first claim will be described with reference to FIG.

FIG. 1 is a block diagram showing an embodiment of the invention of claim 1, in which the document table (2), the reference white plate (3), the optical unit (6) to the CCD image sensor (9) are arranged in the conventional device described above. It is exactly the same as that of .

In FIG. 1, the embodiment of the invention of the first claim includes exactly the same components as the conventional device described above, a signal processing circuit (10) connected to a CCD image sensor (9), and a CCD image sensor (9). a signal level detection section (11) connected to the sensor (9); and a lighting power supply control section (12) whose input side is connected to the signal level detection section (11) and whose output side is connected to the illumination lamp (7). It consists of

Note that the optical unit (6) is movable in the direction of arrow a.

Next, the operation of the above embodiment will be explained with reference to FIG.

FIG. 2 is a characteristic diagram showing the operation of the embodiment of the invention as claimed in claim 1.

In FIG. 2, the horizontal axis shows the exposure amount and the vertical axis shows the signal output level. When the exposure amount is in the P range, the S/N is poor,
When it is in the Q region, it is good, and when it is at the X point, it is the optimal operating point.

Before starting to read the manuscript (1), carry out the following steps,
The operating point (M light amount) of the CCD image sensor (9) is adjusted to a predetermined percentage (for example, 70%) of the saturation exposure amount.

First, the white surface of the reference white plate (3) (which may also serve as a shading correction plate) is subjected to photoelectric conversion, and its output level is observed by the signal level detection section (11).

The illumination power supply control unit (12) increases the light intensity of the illumination lamp (7) in steps, and determines the light intensity at which the output of the CCD image sensor (9) reaches the saturation point.

Then, as shown in FIG. 2, the light intensity of the illumination lamp (7) is lowered to a predetermined percentage of the saturation point.

Therefore, variations in the sensitivity and saturation exposure of the CCD image sensor (9), variations in the amount of light from the illumination lamp (7), changes in the amount of light due to ambient temperature and aging, changes in the amount of light in optical systems such as lenses and mirrors, etc. , the optimum operating point of the CCD image sensor (9) can be always followed and set for operating point variation factors.

Further, the configuration of an embodiment of the invention according to the second claim will be explained with reference to FIG.

FIG. 3 is a block diagram showing an embodiment of the invention of the second claim, in which the document table (2), the reference white plate (3), the optical unit (6) to the signal level detection section (11) are This is exactly the same as the embodiment of the invention claimed in claim 1.

In FIG. 3, the embodiment of the invention claimed in the second claim has the same components as the invention claimed in the first claim described above, and a CCD image sensor (9) whose input side is connected to the signal level detection section (11). ) with the output side connected to the sensor drive circuit ( ).
13).

Next, the operation of the above embodiment will be explained with reference to FIGS. 4 and 5.

FIGS. 4(a) to 4(d) are C of the embodiment of the invention of the second claim.
Waveform diagrams showing the operation when the accumulation time of the CD image sensor is changed, and FIGS. 5(a) to (d) are waveform diagrams showing the operation when the tarok frequency of the CCD image sensor of the embodiment of the invention of the second claim is changed. FIG. 2 is a waveform diagram showing the operation of FIG.

Before starting to read the manuscript (1), carry out the following steps,
The operating point (exposure amount) of the CCD image sensor (9) is adjusted to a predetermined percentage (for example, 70%) of the saturation exposure amount.

First, the white surface of the reference white plate (3) (which may also serve as a shading correction plate) is subjected to photoelectric conversion, and its output level is observed by the signal level detection section (11).

The sensor drive circuit (13) changes the accumulation time of the CCD image sensor (9) as shown in FIG. 4(b) or (d), and the output of the CCD image sensor (9) reaches the saturation point. Find the amount of light that reaches .

Then, the accumulation time is controlled by the sensor drive circuit (13) so that it becomes a predetermined percentage of the saturation point.

Further, in another embodiment of the invention of the second claim, the sensor drive circuit (13) changes the tarok frequency of the CCD image sensor (9) as shown in FIG. 5(b) or (d). Then, the amount of light at which the output of the CCD image sensor (9) reaches the saturation point is determined.

Then, the clock frequency is controlled by the sensor drive circuit (13) so that it becomes a predetermined percentage of the saturation point.

Therefore, there are effects similar to those of the invention of the first claim described above.

In addition, in each of the above embodiments, a CCD image sensor was explained, but α-3i type image sensor, MO3 type CC
A similar operation can be expected if it has saturation characteristics such as a D image sensor.

Incidentally, in the above description, the case where the present invention is used in a contact type reading device has been described, but it goes without saying that it can also be used in other reduced type reading devices.

[Effects of the Invention] As described above, the present invention provides an image sensor that detects light emitted from an illumination light source and reflected by a document and outputs a corresponding signal, and a saturation point detector that detects the saturation point of this image sensor. and illumination light source control means for controlling the amount of light emitted from the illumination light source so that the image sensor has an optimal operating point based on the saturation point, or Since the image sensor driving means controls the storage time of the image sensor so as to reach the operating point, it is possible to always follow and set the optimum operating point of the image sensor.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the invention of the first claim,
FIG. 2 is a characteristic diagram showing the operation of the embodiment of the invention claimed in the first claim, FIG. 3 is a block diagram showing the embodiment of the invention claimed in the second claim, and FIGS. 4 and 5 are diagrams showing the operation of the embodiment of the invention claimed in the second claim. FIG. 6 is a block diagram showing the conventional document reading device, FIG. 7 is a characteristic diagram showing the characteristics of the CCD image sensor, and FIG. 8 is the characteristics of the illumination lamp. It is a characteristic diagram. In the figure, (1) ... Original, (2) ... Document table, (3) ... Reference white plate, (7) ... Illumination lamp, (8) ... Light converging fiber lens. , CCD image sensor, ... signal level detection section, ... illumination power supply control section, ... sensor drive circuit. In each figure, the same symbols indicate the same or corresponding parts (9)...
・ In addition, is shown.

Claims (2)

[Claims] (1) an image sensor that detects light emitted from an illumination light source and reflected by a document and outputs a corresponding signal; a saturation point detection means that detects a saturation point of the image sensor; 1. A document reading device comprising: illumination light source control means for controlling the amount of light emitted from the illumination light source so that the illumination light source has an optimal operating point. (2) an image sensor that detects light emitted from an illumination light source and reflected by a document and outputs a corresponding signal; a saturation point detection means that detects a saturation point of the image sensor; and a saturation point detection means that detects the saturation point of the image sensor. 1. A document reading device comprising an image sensor driving means for controlling an accumulation time of the image sensor so that the image sensor has an optimum operating point.