JPS6122296B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for sharpening reproductions of continuous tone originals comprising an electro-optical scanning device for the original, a device for deriving a sharpening signal, and a device for superimposing the sharpening signal on the image signal. The present invention relates to a device for controlling temperature.

It is known to affix a single color or multicolor continuous tone original image as a transparent or opaque image to a scanning drum and photoelectrically scan it. In that case, scanning is performed as follows. That is, the scanning beam forms a point on the original image, and the original image is scanned in a spiral manner by the rotational movement of the scanning drum and the movement of the scanning beam in the drum axis direction. In the case of color printing, the reflected or transmitted light reflected from the original image is separated into spectral regions of the three primary colors cyan, magenta, and yellow by a dichroic filter, and converted into electrical signals by a photoelectric conversion device.
This electrical signal is a so-called primary color signal. These primary color signals then control a recording section, such as an engraving needle or a recording lamp, and each primary color signal is then reproduced onto a record carrier fixed on a recording drum. The operation of the recording drum and of the recording section is synchronized with the operation of the scanning drum and scanning beam. That is, the recording drum and scanning drum rotate at the same speed. The recording speed may be faster or slower than the scanning speed depending on the desired magnification or reduction of the copy. The relative axial movement between scanning part and recording part, ie scanning part and record carrier, also takes place.

Because the printing ink is imperfect and factors other than the printing ink affect the final copy color throughout the copying process, in order to obtain the desired color by copying, it is difficult to obtain the desired color from the photoelectric conversion device until it reaches the recording section. The primary color signals often have to be electronically controlled once or several times in the process. In this case, for example, gradation changes, undercolor division, and color corrections are generally carried out under electronic control.

In many cases, the original image to be scanned is a photographic image in which part of the sharpness of the original image has been reduced due to film development, enlargement, or copying. must be repeated. Therefore, the second color signal other than the primary color signal is
image signal is used, and this image signal is superimposed on the primary color signal to restore sharpness. This image signal is named a sharpening signal.

This sharpening signal can be obtained, for example, by the following two methods. In the first method, the image signal obtained by scanning the original image, that is, the primary color signal, is differentiated once or several times, and the resulting sharpening signal is extracted from the primary color signal. The sharpening signal is then superimposed on the primary color signal. As a result, the primary color signals are sharpened and further processed according to the process described above.

In a second method, corresponding to the blur masking in photocopying technology, in addition to the sharp scanning points, the vicinity of the so-called scanning points is additionally scanned. The resulting signal represents the average brightness in the vicinity of this scan point and is subtracted from the primary color signal. The signal obtained as a result of the subtraction is used as a sharpening signal and superimposed on the image signal. A sharpened signal results, which is further processed in a corresponding manner.

Both of the above methods have the advantage that the reduced sharpness is restored, but relatively sharp parts of the original may be reproduced even sharper, resulting in too high a sharpness. However, if the sharpness is then lowered again, extremely detailed parts of the original image, such as textiles or patterns, will be reproduced indistinctly.

SUMMARY OF THE INVENTION It is an object of the present invention to relate to an apparatus for photoelectric copying of continuous tone originals, which overcomes the above-mentioned drawbacks and makes it possible to sharpen each part of the original independently.

According to the invention, this problem is solved in the following way: by providing a contrast evaluation circuit, the weight device increases or reduces the sharpening signal superimposed on the image signal by the output signal of the contrast evaluation circuit. We have provided a means to do so.

It is known to select the amplitude of a sharpening signal to be constant over the entire original image and to superimpose this sharpening signal on the image signal. However, in that case, it is impossible to locally change the sharpness of the original image.

When controlling the sharpening signal using a signal based on the contrast of the original image controlled by the image signal,
The sharpening signal is attenuated when the contrast of the original image is strong.

The superimposition device can be configured as a switch, for example.

Next, the present invention will be explained with reference to the drawings.

In FIG. 1, the surface of the scanning drum is transparent for recording transparencies, such as transparencies 2, for example. A mask 4 and a record carrier 5 are fixed to the drum 3. The drums 1 and 3 are driven by an electric motor 7 via a shaft 6. The scanning sections 9 and 10 and the recording section 11 are also driven by the electric motor 7 via the feed screw 8. The scanning unit 9 scans the transparency 2,
The scanning unit 10 scans the mask 4. The recording unit 11 is arranged corresponding to the record carrier 5. The scanning light beam 15 enters the interior of the scanning drum 1 from the light source 12 via the lens system 13 and 14 and through the hole 16 of the mirror 17 . A mirror 18 is provided inside the scanning drum 1 . The light ray 15 is imaged by this mirror 18 at an image point 19 on the transparency 2. Light source 12, lens 13
and 14, the mirror 18 is arranged such that the scanning beam 15 is imaged at an image point 19 of the transparency 2.
When the scanning light beam 15 passes through the transparency 2, it reaches an image point 19.
is modulated by the content of the original image, passes through a lens 20 in the scanning section 9, passes through the hole 21 in the mirror 22, and reaches the color separation section. This color separation section is composed of dichroic filters 23 and 24 and photoelectric conversion devices 25, 26 and 27. The scanning beam 15 consists of three partial beams, namely partial beams belonging to each of the spectral regions of the three primary colors magenta, cyan and yellow;
It is decomposed into These partial beams are then supplied as electrical color separation signals from the output of the photoelectric conversion device. This color separation signal is called a primary color signal.

A signal obtained by uniformly and constantly illuminating an image point 33 scanning around the image point 19 is used. The geometric shape of the image point 33 can then be ring-shaped, star-shaped or sector-shaped, for example. When divided into sectors, each sector is separated by a mirror 22,
It is supplied to four corresponding photoelectric conversion devices. By subtracting the minimum signal from the maximum signal among the signals generated by the photoelectric conversion device, a signal that enhances the contrast can be obtained. This signal is passed through a signal switching element or signal modulation element 50, 53 or 91 and further through a line 40.
is superimposed on the recording signal via.

In the embodiment shown, the optical system has an additional scanning device which scans around the image point 19 of the transparency 2. This scanning device consists of a cathode ray tube 28. A rotating bright spot 30 is generated on the screen 29 of the cathode ray tube 28. The scanning light beam 31 is a bright spot 3
0 through the lens 32, the mirror 17, the lens 14, and the mirror 18 to reach the vicinity of the image point 19 of the transparency 2. The scanning beam 31 is further imaged at an image point 33, which scans the transparency 2. The image point 33 rotates around the image point 19 in synchronization with the bright spot 30 on the screen 29. A light ray 31 modulated by the original image content around the image point 19 reaches the photoelectric conversion device 34 from the image point 33 via the mirror 22 . The photoelectric conversion device 34 generates an electrical signal, ie, a so-called neighborhood signal.
The scanning drum 1 is rotated, and at the same time the scanning unit 9 is driven by the feed screw 8 and moved along the scanning drum 1 in the axial direction so that the entire original surface of the transparency 2 is completely point-scanned and line-scanned. . In that case, the light source 12, lens 13, mirror 16, lens 14, mirror 18
and a cathode ray tube 28 having a lens 32 is mechanically fixedly connected to the scanning section 9 so that said component is moved into the scanning section 9 for a predetermined stroke length determined by the lead screw.
It must be possible to move axially with the As a result, the relative movement between the scanning drum and the entire scanning section, ie, the rotation of the scanning drum and the axial movement of the entire scanning section, causes the transparency 2 to be point-scanned and line-scanned in a spiral manner.

The so-called primary color signals generated by the photoelectric conversion devices 25, 26 and 27 correspond to magenta, cyan and yellow, respectively, and reach the switch 38 via lines 35, 36, 37. Only the primary color signals corresponding to the primary colors to be recorded each time are selected by the switch 38. Usually lines 35, 36 and 37
Although a color correction circuit is inserted in , a description of the color correction circuit will be omitted. The signal from the switch 38 is recorded by the recording section 11. The recording unit 11 includes, for example, an amplifier 39. Amplifier 39 is controlled via line 40 and the output signal of amplifier 39 is connected to recording lamp 41.
is applied to A recording lamp 41 generates a light beam 42 . The light beam 42 is imaged by an optical system 43 onto the record carrier located on the drum 3 . The record carrier 5 is made of, for example, a photosensitive material. When the record carrier 5 receives the light beam 42, as a result of the relative movement between them due to the rotation of the drum 3 and the axial movement of the recording section 11, a spiral line corresponding exactly to the scanning of the transparency is caused by the light beam 42 to be drawn on the record carrier 5. recorded in

According to the present invention, a contrast evaluation circuit is provided, and for a device that superimposes a sharpening signal on an image signal, the output signal of the contrast evaluation circuit increases or reduces the sharpening signal superimposed on the image signal. . As shown in dashed lines in FIG. 1, the contrast evaluation circuit includes a transistor 50, a subtracter 48, an amplifier 57 and a diode 58, as well as lines connecting them accordingly. The output signal of this stage reaches transistor 53 via amplifier 51.

Next, the operation of the contrast evaluation circuit will be explained.
Simultaneously with the scanning and recording, the photoelectric conversion device 34
A near-field signal is generated. This neighborhood signal is supplied via line 44 to an RC element consisting of a resistor 45 and a capacitor 46. line 3
5 and a signal supplied via a decoupling resistor 47 is subtracted from the nearby region signal by a subtraction circuit 48,
The resulting difference signal is applied between the collector and emitter of transistor 50 and, via polarity inversion stage 51, between the collector and emitter of transistor 53. Next, the signal is passed through the variable resistor 54,
It is superimposed on the primary color signal of line 40 as a so-called sharpening signal for improving sharpness. transistor 5
If a connection line is used instead of between the collector-emitters of 0 and 53 and the difference signal is superimposed on the primary color signal via this connection line, known blurring masking will be achieved. In contrast to known blur masking, in the embodiment of the invention transistors 50 and 53 are inserted as modulation elements or signal switching elements in the signal path of the near-field signal. When the image point 33 orbits or scans surfaces of various densities while orbiting around the image point 19, the signal from the photoelectric conversion device 34 becomes a high frequency signal with alternating amplitude. This signal is resistor 5
5 and a capacitor 56 to an amplifier 57. A diode 58 is connected downstream of the amplifier 57. Diode 58 is transistor 5
0 base and allows only negative signal amplitude to pass. A resistor 59 is provided to adjust the operating point of the transistor 50, and a resistor 52 is provided to adjust the operating point of the transistor 53.
is provided. Both resistors are connected to the positive terminal of a voltage source (not shown). The negative signal supplied by the diode 58 renders the transistor 50 non-conductive, and as a result, the RC is output from the photoelectric conversion device 34.
The sharpening signal being applied to the collector of transistor 50 via elements 45 and 46 is blocked between the collector and emitter. The sharpening signal is therefore blocked between the collector and emitter of the transistor 50 only if a high-frequency signal with alternating amplitude is supplied by the photoelectric conversion device 34, i.e. only if the density around the image point 19 is not uniform. Ru.

On the other hand, if the density around the image point 19 is uniform, the transistor 50 does not block the sharpening signal, and the sharpening signal is fully activated, resulting in improved sharpness. A sharpening signal that improves sharpness is extracted from the neighborhood signal. The nearby area signal is obtained from the rotating bright spot 30 of the cathode ray tube 28, as described above.
FIG. 2 is a block diagram of an electron beam deflection circuit device that causes the electron beam of the cathode ray tube 28 to move in a circular motion. As shown in FIG. 1, this circuit device includes an electron beam deflection circuit 60
and a control circuit 61 that controls the brightness of the electron beam at a constant level. Control circuit 61 that controls the electron beam
will not be explained in detail. This control device supplies a constant voltage to adjust the operating point of the cathode ray tube.

An electron beam deflection circuit for rotating the electron beam is a transformer 6 controlled via a high frequency generator 62.
It is composed of 3. The secondary winding of the transformer 63 is connected to horizontal deflection plates 64, 65 of the cathode ray tube 28. Via a capacitor 66 and a resistor 67, as well as an amplifier 68, the secondary voltage of the transformer 63 is supplied to the vertical deflection plates 69, 70 of the cathode ray tube. As a result, the vertical deflection plates 69,7
The phase of the deflection voltage applied to the horizontal deflection plates 64 and 65 is shifted by 90 degrees from the phase of the deflection voltage of the horizontal deflection plates 64 and 65. As a result, the electron beam is deflected so that it circulates according to the Lissajieu figure. In this case, the frequency of the high frequency generator 62 is set several times higher than the image point scanning frequency,
It is desirable to ensure that the area around the scanned image point is scanned at the required speed.

The effect of the sharpening signal can be varied by controlling the sharpening signal in relation to only one color selected in the original image. For example, in reproducing skin color, it is desirable to transfer the skin color without sharpening. To this end, a color selection circuit 71 can be provided that supplies a negative signal via the diode 72 only when the selected color is scanned in the original image. A transistor 53 is connected downstream of the diode 72, which becomes non-conducting when the base voltage becomes negative and prevents the sharpening signal from passing between collector and emitter.

Next, the color selection circuit 71 will be explained in detail with reference to FIG. The primary color signals corresponding to magenta, cyan and yellow reach color selection circuit 71 via lines 35, 36 and 37, respectively. First of all, above 3
The differences between the two primary color signals and the corresponding fixed values mgo, cyo, geo are formed. That is, each primary color signal is supplied to one input of operational amplifiers 76, 77 and 78, which are connected as differential amplifiers. On the other input side of the operational amplifiers 76, 77, 78, constant signal values mgo,
cyo and geo are supplied. The outputs of the operational amplifiers are connected to a multiplication stage 82, which multiplies the outputs of the operational amplifiers 76, 77, 78 with each other. The circuit structure of the multiplication stage 82 is well known and, for example, a multiplication device that performs multiplication using the nonlinear characteristic curve of a rectifier or the nonlinear characteristic curve of a vacuum tube is available, so a description thereof will be omitted.

Then the adjusted constant signal values mgo, cyo and
If primary color signals mg, cy, ge approximately equal to geo are supplied via lines 35, 36 and 37, respectively, the signal obtained at the output of multiplier stage 82 is at a minimum. This signal is converted to the maximum signal by amplitude inverter 83 and applied to diode 72. Diode 72 then renders the base of transistor 53 non-conducting, so that the sharpening signal is blocked and not supplied to the recording section.

The resulting effects include, for example, the following points:
That is, the skin color scanned in the original image is reproduced without being sharpened by the sharpening signal.

Furthermore, it would be advantageous to control the sharpening signal according to the content of the original image by scanning a mask held in accordance with the original image in synchronization with the original image and controlling the sharpening signal using the scanning signal obtained at that time. be. For this purpose, a mask 4 is fixed on the drum 3. The mask 4 is scanned by a scanning section 10. The dark areas 85 of the mask 4 must be reconstructed using the sharpening signal. One primary color signal supplied from the photoelectric conversion device 27 via the line 35 is supplied to two RC elements, differentiated twice by the RC elements, and becomes a sharpening signal. These RC elements are resistors 86, 87
and capacitors 88 and 89. The output signal of the RC element is applied via a polarity inversion stage 90 to a transistor 91 which acts as a signal modulation element or a signal switching element. The output signal of the RC element is further supplied to the input line 40 of the recording section 11 via a resistor 92. The operating point of transistor 91 is adjusted by resistor 98. The base of the transistor 91 is connected to the diode 93, and the signal generated by the photoelectric conversion device 94 is transmitted to the signal amplifier 9.
A scanning signal for the mask 4 supplied to the diode 93 is applied to the diode 93 . The scanning beam of the mask 4 is imaged at an image point 96 of the mask 4. The scanning light beam of the mask 4 reaches the photoelectric conversion device 94 via a lens system 97 from a light source (not shown). For this purpose, a device similar to the light beam supply device described above, consisting of a light source 12, lenses 13, 14 and a mirror 18, can be used, for example. This light beam supply device is moved in the axial direction along the mask 4 by the feed screw 8 in accordance with the axial movement of the scanning section 10.

The sharpening signal is passed only when the signal generated by the scanning section 10 is weak, that is, when the dark part of the mask 4 is being scanned.

[Brief explanation of the drawing]

The drawings serve to explain the invention, and FIG. 1 is a schematic diagram of an embodiment of the invention for copying a continuous tone original;
FIG. 2 is a block diagram of a circuit device for rotating an electron beam, and FIG. 3 is an embodiment of a color signal detection circuit used in the copying machine of FIG. 1. 1... Scanning drum, 2... Transparency, 3... Recording drum, 4... Mask, 5... Record carrier, 6...
...Axis, 7...Electric motor, 8...Feed screw, 9...Original image scanning section, 10...Mask scanning section, 11...Recording section, 12...Light source, 13...Lens system, 16,2
1... Hole, 17, 18... Mirror, 19, 33... Image point, 20... Lens system, 22, 23, 24...
Mirror, 28...Cathode ray tube, 29...Screen, 3
0... Light spot, 15, 31... Scanning light beam, 32...
Lens system, 38... Selection switch, 39... Amplifier, 41... Recording lamp, 42... Recording beam, 4
3... Lens system, 47... Decoupling resistance, 48...
Subtraction circuit, 51, 90... Polarity inversion stage, 57...
Amplifier, 60...Electron beam deflection circuit, 61...Control circuit, 62...High frequency generator, 63...Transformer,
64, 65, 69, 70... Deflection plate, 68... Amplifier, 71... Color selection circuit, 76, 77, 78...
... operational amplifier, 82 ... multiplication stage, 83 ... amplitude inverter, 85 ... dark part of mask, 95 ... signal amplifier, 96 ... mask image point, 97 ... lens system.

Claims (1)

[Claims] 1. In an apparatus for controlling the sharpness of a copy of a continuous tone original, which comprises an electro-optical scanning device for the original, a sharpening signal deriving device, and a device for superimposing the sharpening signal on the image signal, the contrast evaluation circuit sharpening of a copy of a continuous tone original, characterized in that the superimposing device is provided with means for increasing or reducing a sharpening signal superimposed on the image signal by the output signal of the contrast evaluation circuit. A device that controls the degree of