JP2939757B2 - Image reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial application field> The present invention relates to a method of scanning a film or an original having image information with a laser beam, photoelectrically converting transmitted light or reflected light thereof, and further logarithmically converting the density information of the image. The present invention relates to an image reading device for obtaining

<Prior Art> Conventionally, as this type of image reading apparatus, there is the following.

An X-ray film as an image information medium is irradiated with laser light from a laser light source using a rotating polygonal mirror called a polygon mirror that rotates at high speed, and repeatedly scans (main-scans) the X-ray film in one direction. The X-ray film itself is moved (sub-scanning) in a direction perpendicular to the scanning direction to scan the entire surface of the X-ray film. Then, the transmitted light or the reflected light of the X-ray film is received and photoelectrically converted, and after being subjected to logarithmic conversion, A / D conversion, shading correction and the like, it is stored in an image memory (see JP-A-60-96075).

<Problem to be solved by the invention> However, in such an image reading apparatus,
Density information is obtained by logarithmic conversion of the image signal obtained by photoelectric conversion using a logarithmic amplifier (LOG amplifier). Conventionally, a variable resistor is set manually while reading a film with a certain optical density In addition, since the density adjustment such as the zero point adjustment is performed by using a semi-fixed resistor such as a trimmer, there is a problem that it is troublesome and inaccurate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems, and has as its object to automatically perform density adjustment.

<Means for Solving the Problems> For this reason, the present invention is to scan the image information medium by irradiating the medium with laser light, photoelectrically convert the transmitted light or reflected light of the medium, and then logarithmically convert the logarithmic amplifier. In an image reading apparatus for obtaining density information of an image, as shown in FIG. 1, an output adjustment circuit for density adjustment for giving an offset and a gain to its output is provided after a logarithmic amplifier, while an image information medium is not provided. Offset setting means for setting an offset based on the output of the logarithmic amplifier, and inserting a filter in the optical path of the laser light in the absence of the image information medium, and setting the gain based on the offset-adjusted output of the logarithmic amplifier at this time. And a gain setting means for setting.

<Operation> In the above configuration, the following density adjustment is performed at the time of starting the apparatus or each time the image information medium is read once.

First, scanning is performed without an image information medium,
At this time, the output of the logarithmic amplifier is read, and an offset value is set to adjust the zero point.

Next, a scan is performed by inserting a predetermined filter into the optical path of the laser beam in the absence of the image information medium, and the offset-adjusted output of the logarithmic amplifier is read at this time, and a gain value is set to adjust the inclination. I do.

After the offset and the gain are set in this way, the set offset and the gain are given to the output of the logarithmic amplifier when reading the image information medium, and the density is automatically adjusted.

<Example> An example of the present invention will be described below.

FIG. 2 shows the overall configuration of the apparatus, in which a film mounting table 2 is provided on the upper part of a main body frame 1 and X is placed there.
The line film XF is a transport system unit 3 including a pulse motor.
, And is passed downward between the optical system unit 4 and the light receiving system unit 5 on the way to read an image. Thereafter, the X-ray film XF is discharged to the film discharge plate 7 via the film discharge guide 6.

FIG. 3 shows the configuration of the optical system unit and the light receiving system unit.

Laser light generated from a laser diode 11 as a laser light source is shaped by a collimator lens 12, reflected by a mirror 13, and then directed to a rotating polygon mirror 14 called a polygon mirror that rotates at a high speed in a horizontal plane at a predetermined speed. . The laser light reflected by the rotary polygon mirror 14 repeatedly scans the X-ray film XF to be read from right to left through an fθ lens 15 which forms an image at a distance proportional to the incident angle θ with respect to the optical axis. Since the X-ray film XF is also sent downward by the pulse motor 16 of the transport system unit, these scan the entire surface of the X-ray film XF.

The laser beam transmitted through the X-ray film XF is reflected by the reflection surface 17a of the elliptical mirror type condensing body 17, is collected, and is received by the photodiode 18 as a photoelectric converter. here,
The reflecting surface 17a of the light collector 17 forms a part of an elliptical shape, and a photodiode 18 is arranged at one focal position.

The image signal obtained by the photoelectric conversion by the photodiode 18 is logarithmically calculated by a logarithmic amplifier 19 and converted into a density signal. Then, the output adjustment circuit 20 gives an offset and a gain to adjust the density. And the A / D converter 21
After the A / D conversion, the image data is subjected to shading correction by the shading correction circuit 22 and stored in the image memory 23.

Here, ND (neutral density) is applied to the optical path of the laser beam from the laser diode 11 by the solenoid 24.
The filter 25 is put in and out. This ND
The filter 25 is for reducing the amount of light, for example, by about 1%.

 FIG. 4 shows the configuration of the output adjustment circuit 20.

The output adjustment circuit 20 includes an adder 31 for offset adjustment.
And a multiplier 32 for gain adjustment and a low-pass filter 33.

Offset OF to adder 31 and gain G to multiplier 32
Is set by an offset adjusting means and a gain adjusting means constituted by software in a control CPU or a circuit, and is provided through data lines 34 and D / A converters 35 and 36.

In this embodiment, the gain adjustment multiplier 32 is provided after the offset adjustment adder 31. However, as shown in FIG. 5, the gain adjustment multiplier 32 and the offset adjustment The adders 31 may be arranged in this order.

The setting of the offset and the gain is performed according to the routine shown in the flowcharts of FIGS. These are performed in the order of an offset setting routine and a gain setting routine when the apparatus is started or before each image reading operation.

First, the offset setting routine will be described with reference to the flowchart of FIG. This routine corresponds to offset setting means.

In step 1 (shown as S1 in the figure, the same applies hereinafter), the counter C is set to an initial value of 255 (FF). This value is for detecting an abnormality in the circuit when the signal does not reach the specified value even if the adjustment operation is repeated the number of times, and varies depending on the circuit system. Also, in step 2, the offset OF is set to the initial value 0.
To

 In step 3, scanning is performed for one line.

In the next step 4, the A / D converter 21 converts the A / D signal from the photodiode 18 through the logarithmic amplifier 19 and the output adjustment circuit 20.
The converted line data is stored in the line memory.

In the next step 5, the minimum value is searched for from the data stored in the line memory, and this is set to M (see FIG. 8). In this embodiment, the minimum value is used as a representative value of the line data since the minimum digital value is used when the maximum amount of light is incident on the photoelectric converter. When designed so as to output the maximum digital value, the maximum value or the like may be used.

In the next step 6, the value of the minimum value is set value a '<M
<Set value a (where a is a set value of about 10 in decimal notation and a 'is a set value of about 5 in decimal, assuming that the output range is 000 to FFF)
It is determined whether or not.

In the case of NO, the process proceeds to step 7, where the counter C is decremented by one. Next, the routine proceeds to step 8, where it is determined whether or not the counter C has become 0. In the case of YES, the processing shifts to error processing. If NO, go to step 9 and enter offset OF
Is increased or decreased by 1 and the process returns to step 3.

If the determination in step 6 is YES, ie, a '<M
If <a, escape to step 10. Thereby, the offset OF value is determined.

Next, the gain setting routine will be described with reference to the flowchart of FIG. This routine corresponds to gain setting means.

In step 21, the solenoid 24 is turned on, and the ND filter 25 is inserted into the optical path of the laser beam.

In step 22, the counter C is set to an initial value of 255 (FF). In step 23, the gain G is set to an initial value.

 In step 24, scanning is performed for one line.

In the next step 25, the line data is stored in the line memory.

In the next step 26, the minimum value is searched for from the data stored in the line memory, and this is set to M.

In the next step 27, the value of the minimum value M is set to the set value b <M
It is determined whether or not a set value c (b is an expected value of about −10 at a predetermined optical density (D = 2), and c is an expected value of about +10).

If NO, the process proceeds to step 28, where the counter C is decremented by one. Next, the routine proceeds to step 29, where it is determined whether or not the counter C has become 0. In the case of YES, the signal does not reach the specified value even if the adjustment operation is repeated a predetermined number of times, and there is an abnormality in the circuit system. Since it can be determined, the processing shifts to error processing.
If NO, the process proceeds to step 30, where the gain G is increased or decreased by 1, and the process returns to step 24.

If the determination in step 27 is YES, that is, b <M <
In the case of c, the process escapes to steps 31 and 32.

In step 31, the solenoid 24 is turned off, and the ND filter 25 is pulled out of the optical path of the laser beam.

 In step 32, the gain G value is determined.

As described above, after automatically setting the offset value of the photoelectric conversion system under 100% light intensity (solenoid 24OFF), a 1% ND filter is inserted into the optical path (solenoid 24ON) and a predetermined optical density (D = 2) is obtained. That is, the gain is automatically set to be as follows.

The light scanned by the laser beam and transmitted through the X-ray film is converted into an electric signal by a photodiode 18, and the signal becomes a current signal proportional to the light amount. Must keep the S / N high. This is because, in a minute signal portion (high-density portion), even a slight noise becomes large when logarithmically converted. Therefore, the wiring between the photodiode 18 and the logarithmic amplifier 19 is made as short as possible. Specifically, the photodiode 18 and the logarithmic amplifier 19 are arranged on the same substrate.
And an electric shield except for a window for incident light may be provided. That is, the entire substrate is covered with a conductive substance having a GND potential. This allows
Electromagnetic noise from outside can be prevented.

FIG. 9 shows a specific circuit configuration of the logarithmic amplifier 19.

Here, conventionally, an I / V converter was interposed between the photodiode 18 and the logarithmic amplifier 19 (the operational amplifiers A1 and A2), but by eliminating this, the noise of the converter is eliminated, and the temperature is reduced. The stability can be improved, and the influence of the input voltage drift of the operational amplifier can be neglected.

Further, the frequency characteristics of the logarithmic amplifier can be improved by an appropriate combination of the capacitors C1 and C2.

<Effects of the Invention> As described above, according to the present invention, when reading density information of an image, an effect is obtained that density adjustment can be automatically set to an optimum condition.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is an overall configuration diagram of an image reading apparatus showing one embodiment of the present invention, FIG. 3 is a main part configuration diagram of the same apparatus, and FIG. FIG. 5 is a circuit diagram of a reading circuit showing another embodiment, FIG. 6 is a flowchart of an offset setting routine, FIG. 7 is a flowchart of a gain setting routine, FIG. Is a diagram showing the minimum value of line data, and FIG. 9 is a circuit diagram of a logarithmic amplifier. 11… Laser diode, 14… Rotating polygon mirror, 16… Pulse motor, 17… Condenser, 18 …… Photodiode,
19: Logarithmic amplifier, 20: Output adjustment circuit, 21: A / D converter, 31: Adder, 32: Multiplier

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-148971 (JP, A) JP-A-62-189874 (JP, A) JP-A-1-177264 (JP, A) JP-A-63-1987 200676 (JP, A) JP-A-63-208367 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04N 1/40-1/409 H04N 1/113

Claims (1)

(57) [Claims] An image reading apparatus which scans an image information medium by irradiating the medium with laser light, photoelectrically converts transmitted light or reflected light of the medium, and logarithmically converts the light or reflected light by a logarithmic amplifier to obtain image density information. At the subsequent stage of the logarithmic amplifier, while providing an output adjustment circuit for density adjustment that gives an offset and gain to its output,
Offset setting means for setting an offset based on the output of the logarithmic amplifier when the image information medium is not present,
Gain setting means for setting a gain based on the offset-adjusted output of the logarithmic amplifier at this time by inserting a filter into the optical path of the laser light in a state where the image information medium is not present. Reader.