JPH03165178A - Picture reader - Google Patents

Abstract

PURPOSE:To adjust density automatically by inserting a filter to an optical path of a laser beam while no picture information medium is loaded so as to set the gain based on an output subject to offset adjustment for a logarithmic amplifier in this case. CONSTITUTION:With no picture information medium X loaded, scanning is implemented, an output of a logarithmic amplifier 19 in this case is read to make zero point adjustment, then the offset is set. Similarly, with no picture information medium XF loaded, a prescribed filter 25 is inserted to the optical path of a laser beam to apply scanning and the output subject to offset adjustment of the logarithmic amplifier 19 is read to apply tilt adjustment thereby setting the gain. Thus, after the offset and gain are set, the set offset and gain are given to the output of the logarithmic amplifier 19 at the read of the picture information medium XF to attain density adjustment automatically. Thus, the density adjustment is set automatically with optimum condition.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention scans a film or original containing image information with a laser beam, photoelectrically converts the transmitted light or reflected light, and then performs logarithmic conversion to obtain density information of the image. The present invention relates to an image reading device that obtains images.

<Prior Art> Conventional image reading devices of this type include the following.

The X-ray film as an image information medium is irradiated with laser light from a laser light source using a rotating polygon mirror that rotates at high speed, and the X-ray film is repeatedly scanned in one direction (main scan). The X-ray film itself is moved in a direction perpendicular to the scanning direction (sub-scanning) to scan the entire surface of the X-ray film. Then, the transmitted light or reflected light of the X-ray film is received, photoelectrically converted, and logarithmically converted.
After undergoing D conversion, shading correction, etc., the image is stored in an image memory (see Japanese Patent Laid-Open No. 60-96075).

<Problem to be Solved by the Invention> However, in such an image reading device, the image signal obtained by photoelectric conversion is logarithmically converted by a logarithmic amplifier (LOG amplifier) to obtain density information. In the past, a variable resistor was manually set while reading a film with a certain optical density, and density adjustments such as zero point adjustment were performed using a semi-fixed resistor such as a trimmer, which was cumbersome and , there was a problem that it was inaccurate.

SUMMARY OF THE INVENTION In view of these conventional problems, it is an object of the present invention to enable automatic density adjustment.

<Means for Solving the Problems> For this reason, the present invention irradiates and scans an image information medium with a laser beam, photoelectrically converts the transmitted light or reflected light of the medium, and then performs logarithmic conversion using a logarithmic amplifier. In an image reading device that obtains density information of an image, as shown in Fig. 1, an output adjustment circuit for density adjustment that gives offset and gain to the output of the logarithmic amplifier is installed at the subsequent stage of the logarithmic amplifier, but when there is no image information medium. an offset setting means for setting an offset based on the output of the logarithmic amplifier; and an offset setting means for setting an offset based on the output of the logarithmic amplifier, and a filter inserted in the optical path of the laser beam in the absence of an image information medium to set the gain based on the offset-adjusted output of the logarithmic amplifier at this time. This configuration includes a gain setting means for setting the gain.

<Operation> In the above configuration, the density adjustment described below is performed when the apparatus is started up or every time an image information medium is read once.

First, scanning is performed in the absence of an image information medium, the output of the logarithmic amplifier at this time is read, and the zero point is adjusted (and an offset value is set).

Next, in the same state that there is no image information medium, a predetermined filter is inserted into the optical path of the laser beam and scanning is performed, and the offset-adjusted output of the logarithmic amplifier at this time is read.
Set the gain value to adjust the slope.

After the offset and gain are set in this manner, the set offset and gain are applied to the output of the logarithmic amplifier when reading the image information medium, and density adjustment is automatically performed.

<Example) An embodiment of the present invention will be described below.

FIG. 2 shows the overall configuration of this apparatus, in which a film mounting table 2 is provided on the upper part of the main body frame 1, and the X-ray film XF placed there is transported by a transport system unit 3 including a pulse motor.
On the way, the image is conveyed by passing downward between the optical system unit 4 and the light receiving system unit 5, and the image is read.

Thereafter, the X-ray film XF is discharged to a film discharger 7 via a 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, which rotates at a predetermined speed in a horizontal plane. . The laser beam reflected by the rotating polygon mirror 14 repeatedly scans the X-ray film XF to be read from right to left through the fθ lens 5, 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, the entire surface of the X-ray film XF is scanned by these.

The laser beam that has passed through the X-ray film XF is reflected by the reflective surface 17a of the elliptical mirror type condenser 17, is condensed, and is received by the photodiode 18 as a photoelectric converter. Here, the reflective surface 17a of the condenser 17 forms a part of an ellipse, and a photodiode 18 is arranged at one focal point.

The image signal obtained by photoelectric conversion by the photodiode 18 is logarithmized by the logarithmic amplifier 19 and converted into a density signal. Then, the output adjustment circuit 20 applies an offset and a gain to adjust the density. After being A/D converted by the A/D converter 21, shading correction is performed by the shading correction circuit 22, and the image memory 2
3.

Here, in the optical path of the laser light from the laser diode 11, a solenoid 24 connects the ND to neutral density).
The filter 25 can be taken in and out. This ND filter 25 is for reducing the amount of light by, for example, about 1%.

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

This output adjustment circuit 20 includes an adder 3 for offset adjustment.
1, a multiplier 32 for gain adjustment, and a low-pass filter 33.

The offset OF to the adder 31 and the gain G to the multiplier 32 are set by the control CPU or by the offset adjustment means and gain adjustment means configured by software in the circuit, 35.36.

In this embodiment, the gain adjustment multiplier 32 is installed after the offset adjustment adder 31, but as shown in FIG. 5, the gain adjustment multiplier 32. They may be arranged in the order of the offset adjustment adder 31.

Offset and gain settings are made according to the routines shown in the flowcharts of FIGS. 6 and 7. 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 explained according to the flowchart shown in FIG. This routine corresponds to offset setting means.

In step 1 (denoted as Sl in the figure, below m), the counter C is set to an initial value of 255 (FF).

This value is used to detect a circuit abnormality when the signal does not reach a specified value even after repeating the adjustment operation this number of times, and varies depending on the circuit system. Further, in step 2, the offset OF is set to an initial value of 0.

In step 3, one line is scanned.

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

In the next step 5, the minimum value is searched from among the data stored in the line memory, and this value is set as M (see Figure 8).In this example, when the maximum amount of light is incident on the photoelectric converter, Since it is designed to output the minimum digital value as a signal, the minimum value is used as the representative value of line data, but if it is designed to output the maximum digital value when the maximum amount of light is incident, The maximum value or the like may be used.

In the next step 6, the value of the minimum value M is set to the set value a'<
M<setting value a (assuming that the output range is 000 to FFF, a is a setting value of about 10 in decimal notation, and a'' is 5
degree setting value).

If NO, the process proceeds to step 7, where the counter C is decremented by 1. Next, the process proceeds to step 8, where it is determined whether or not the counter C has reached O. If YES, the process proceeds to error processing. If NO, proceed to step 9, increase or decrease the offset OF by 1, and return to step 3.

If the determination in step 6 is YES, that is, 0<M<
In case a, exit to step 10. This determines the offset adjustment.

Next, the gain setting routine will be explained according to the flowchart shown in FIG. This routine corresponds to gain setting means.

In step 21, the solenoid 24 is turned on and the ND
A 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
). Further, in step 23, the gain G is set to an initial value.

In step 24, one line is scanned.

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

In the next step 26, the minimum value is found from among the data stored in the line memory, and this is set as M.

In the next step 27, the value of the minimum value M is changed to the set value b<M
<Setting value c (b is about -10, C is about +10) is determined.

If No, proceed to step 28 and set counter C to 1.
Subtract. Next, the process advances to step 29, and the counter C is O.
If YES, the signal does not reach the specified value even after repeating the adjustment operation a certain number of times, and it can be determined that there is an abnormality in the circuit system, so the process moves to error processing. If No, proceed to step 30 and set 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
If <c, exit to steps 31 and 32.

In step 31, the solenoid 24 is turned off and the
Remove the D filter 25 from the optical path of the laser beam.

In step 32, the gain G(!) is determined.

In this way, under 100% light intensity (solenoid 24 OFF
) after automatically setting the offset value of the photoelectric conversion system, 1%
Insert the ND filter into the optical path (solenoid 24 ON)
, the gain is automatically set so that a predetermined optical density (D=2) is achieved.

Note that the light scanned by the laser beam and transmitted through the X-ray film is converted into an electrical signal by the photodiode 18, and the signal becomes a current signal proportional to the amount of light, but until it is logarithmically converted, the output 18 of the photodiode S/N of
must be kept high. This is because even a slight noise becomes large in a small signal part (high concentration part) when it is logarithmically transformed. Therefore, the wiring between the photodiode 18 and the logarithmic amplifier 19 is kept as short as possible. Specifically, the photodiode 18 and the logarithmic amplifier 19 are arranged on the same substrate, and the electrical connection is made with the exception of the window for incident light. It is recommended to provide a suitable shield. That is, the entire substrate is covered with a conductive material at GND potential. This can prevent W noise from the outside.

Further, a specific circuit configuration of the logarithmic amplifier 19 is shown in FIG.

Here, in the past, a 1/V converter was interposed between the photodiode 18 and the logarithmic amplifier 19 (op-amp A1, A2), but by abolishing this, the noise of the converter is eliminated, and the temperature Stability can also be improved, and the influence of operational amplifier input voltage drift can be ignored.

Further, by appropriately combining capacitors C1 and C02, the frequency characteristics of the logarithmic amplifier can be made the same as above.

<Effects of the Invention> As described above, according to the present invention, it is possible to automatically set the density adjustment to the optimum condition when reading the density information of an image.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing the configuration of the present invention, FIG. 2 is an overall configuration diagram of an image reading device showing an embodiment of the present invention, and FIG.
4 is a circuit diagram of the reading circuit of the image reading device, FIG. 5 is a circuit diagram of the reading circuit showing another embodiment, and FIG. 6 is a diagram of the offset setting routine. Flowchart, Figure 7 is a flowchart of the gain setting routine, Figure 8 is a diagram showing the minimum value of line data, Figure 9 is a flowchart of the gain setting routine.
The figure is a circuit diagram of a logarithmic amplifier. 11...Laser diode 14...Rotating polygon mirror 16...Pulse motor 17...Concentrator 18
...Photodiode 19...Logarithmic amplifier
20... Output adjustment circuit 21... A/D converter
31... Adder 32... Multiplier

Claims (1)

[Claims] In an image reading device that irradiates and scans an image information medium with a laser beam, photoelectrically converts the transmitted light or reflected light of the medium, and then performs logarithmic conversion using a logarithmic amplifier to obtain density information of the image. , while providing an output adjustment circuit for concentration adjustment that gives an offset and gain to the output of the logarithmic amplifier,
offset setting means for setting an offset based on the output of the logarithmic amplifier when the image information medium is not present;
and gain setting means for inserting a filter into the optical path of the laser beam 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. reading device.