JPS639280A - Recorder having means for correcting density of picture - Google Patents

Abstract

PURPOSE:To compensate effect due to the change in the sensitivity and gamma characteristic of a recording medium, deterioration in the lighting body and heater and environmental change by providing a density correction means correcting the density of a picture so as to input the corrected picture signal. CONSTITUTION:An input picture signal is A/D-converted and inputted to a lookup table 3 via a selector 2. As the table 3, a standard sensitivity table and each table having a prescribed % of deviation are provided and a gradation curve changeover switch 4 is connected to them. The switch 4 is changed over in response to the sensitivity of the recording medium to keep gray balance independently of the sensitivity of medium. An output of the table 3 is converted into an analog signal by the D/A converter 5 and the result is outputted as an output picture signal whose density is corrected for driving a fiber optical tube.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a recording device for recording an image corresponding to an input image signal on a recording medium, and in particular, the present invention relates to a recording device for recording an image corresponding to an input image signal on a recording medium, and in particular, the present invention relates to a recording device for recording an image corresponding to an input image signal on a recording medium, and in particular, The present invention relates to a recording device that is capable of making corrections according to the situation.

[Background of the invention]

Recording media used in recording devices include photographic paper, photosensitive film, instant film, ink sheets, and others, and the recording section for recording on these is FOT.
(Faiha Optical Tube), CRT (Cathode Ray Tube), Summar/Nod, etc.

However, recording media mind, there are variations in its sensitivity,
For this reason, if the input image is recorded as it is by the recording section, the density will change by the amount corresponding to the sensitivity variation, and in color images, if the sensitivity balance of each color is out of order, gray will not appear, There is a problem in that the color balance of the entire image is disrupted and the image quality is degraded.

For example, for color photographic paper, each color has a ±10
There is a sensitivity variation of about 1.5%, and depending on storage conditions, a further change in sensitivity of about ±5% is expected.

Furthermore, with the ink sheets (heat-transferable ink ribbons) used in thermal heads, it is difficult to express subtle gradations, especially in low-depth areas, due to differences in the film thickness and quality of the applied ink. Met.

[Purpose of the invention]

An object of the present invention is to solve the above-mentioned problems by making it possible to correct the depth of an input image signal.

[Structure of the Invention] To this end, in the present invention, in a recording apparatus having a recording section that receives an image signal, scans a recording medium, and records an image corresponding to the image signal, -1- corrects the density of the image. comprising a density correction means for
The image signal corrected by the density correction means was configured to be input to the recording section.

〔Example〕

Examples of the present invention will be described below. In this embodiment, an example will be described in which the above-mentioned FOT is used in the recording section. In this case, the recording medium is photosensitive I4144, for example, color photographic paper, and the recording surface (tube surface) of the FO]
Exposure scanning is performed by moving (scanning) the color photographic paper relative to the photographic paper.

In general, the gamma characteristic curve (characteristic of color intensity relative to input light energy) of this color photographic paper hardly changes, and only the sensitivity changes. This means that if we look at the relationship between the amount of light (man-powered light energy) and the density, the characteristic curve will shift in parallel as shown in Figure 1. The amount of light may be corrected in a direction that compensates for the change.

109 E 11e1+-P oq EOLD + A
...(1) A] 1 and ENEw:
Light amount after correction Eo+,n: Light amount before correction A: Correction value Sensitivity changes can be corrected by this equation (1).

However, the voltage applied to the FOT (input voltage corresponding to the image signal) and the output light amount of the FOT are p. Since 9 is not linear, calculation of 2fi1 is difficult. That is, when creating a correction table, at least the 1°9 relationship between the input terminal and the output light amount must be calculated.

This relationship, as shown in FIG. 2, differs depending on each FOT, and it would be very time-consuming and impractical to measure this relationship for all FOTs used.

Therefore, this relationship is approximated (1u) and calculated as follows.The color density of color photographic paper obtained when the input voltage to the FOT (in processing, the A/D converted bit value) is changed. As shown in Figure 3, the characteristic curve of color photographic paper has a density of 0.5 to 1.5 as shown in Figure 1.
Since it is almost a straight line between the lines, the following algorithm is created using this relationship.

■Print the wedge on standard-sensitivity color photographic paper.
Then, the characteristics of each color shown in FIG. 3 were measured.

(2) Characteristic Curve Human Determine an arbitrary point between 0.5 and 1.5 of the above-mentioned density, and then determine a concentration difference of 0.1 (this corresponds to a difference in sensitivity of about 10%). ) Look at the large bit value of the point. Then, the difference between this large bit value and the input bit value of the original point is used as a correction value.

For example, if the major bit value for density 0.8 is 518, and the major bit value for density 0.9 is 539, then the correction value, which is the difference between the two bits, is 19, which is the standard sensitivity lookup value. The value obtained by adding 19 to each up table becomes the table for photographic paper with 10% lower sensitivity, and the value obtained by subtracting 19 becomes the table for photographic paper having higher sensitivity of 109A. That is, in this example, -30, -20, -10,0
, →10, +20, →-30 (%) River thing Let, respectively, +57, →-3F+, +19.0, -19, -
Correction can be made by adding hint values of 38 and -57 to the values in the standard sensitivity lookup table.

FIG. 5 is a diagram showing a flow rate correction circuit using method 4 as described above.The input image signal is A/D converted RW I
The signal is converted into a digital signal of 8 bits 1 to 1, and is inputted to a lookup signal 3 consisting of a ROM via a data selector 2.

In addition to the table for standard sensitivity, this Lookup Chiful 3 also has -30, -20
, -10,'' -10, -I20, -1-30 (%), respectively. Then, image data from the A/D converter 1 is input to eight of the Atreneu lines,
A gradation curve switching switch (dip switch or rotary switch) circuit 4 is connected to the remaining three lines. This switching switch/notch circuit 4 can be operated arbitrarily by the user, whereby one table is selected from the sensitivity table or other table for the mark <1. Therefore, note 1. By switching this changeover switch circuit 4 according to the sensitivity of the direct medium, it is possible to maintain the gray balance related to the sensitivity of the medium.Also, this lookup table 3 includes a table for switching between three color tables. The 3-bit color switching signal is also misaligned.

Then, the output from this lookup table 3 is D
The signal is converted into an analog signal by the /A converter 5, and then output as a density-corrected output image signal for driving an FOT (not shown).

Reference numeral 6 denotes a test pattern generator, and by inputting the test pattern signal from this generator into the lookup table 3 via the data selector 2, and operating the changeover switch circuit 4, the test pattern can be converted into a correction value. You will be able to set. A gray chart is suitable as this test pattern, and the test pattern generating circuit 6 in this case may be a simple dip switch. That is,
By selecting the table for phantom sensitivity using changeover switches 1 and 4 and outputting a gray scale, it is possible to make corrections for the sensitivity by adjusting the color tone at that time.

FIG. 6 is a diagram showing a density correction circuit of another embodiment. In this example, the contents of the look-up table 3' are used as a table for standard sensitivity, and the adder 7 is used to realize the function of the gradation curve changeover switch 4 described above. 8 is a correction value generation circuit for generating a correction value for addition/subtraction in the adder 7, and 9 is a changeover switch for setting the correction value.

FIG. 7 is a diagram showing a circuit in which the input image signal is kept as an analog signal without moisture correction. In this example, the operational amplifier 10 calculates the correction value set by the polyolium 11. One circuit is provided for each color signal. In this circuit, the correction will be qualitative.

In addition, in the calculation of the correction value explained above, in order to ensure further accuracy, instead of deciding on one point as in the previous example, the difference in the number of bits at two points is detected and the two points are calculated. The correction value can also be determined by the weighted average used.

That is, the bit values at densities α1 and α2 and densities β1 and B2 on the standard sensitivity chifur are A1, A2, and B4, respectively.
, B2, and if the bit value determined by the current input image signal is 8, the relationship with the corrected bit value B is approximately AA, BB.

It can be calculated as A2 AI B2 BI A z A + . For example, α, =0.5, α2=0.
6, β, =1.5, β2=1. ．． 6 is possible.

If this value B is added or subtracted from the input image signal,
A more accurate correction value can be determined. The circuit applied in this case is the circuit shown in FIG.

The following explanation is based on the case where the FOT is used as the recording unit, but the same applies when the thermal head 1 is used. In this case, the corrected output image signal 1 is converted into the energy applied to the thermal head. Ru. In addition, although we have explained how to correct variations in sensitivity with Di I-, it is also possible to correct for deterioration of light emitters such as FOT and heat generating elements such as thermal heads, and it is also possible to correct for changes in the environment such as temperature and humidity. It is also possible to correct for Furthermore, it is possible to cope with changes in the gamma characteristics of the recording medium.

〔Effect of the invention〕

As described above, according to the present invention, since the input image signal can be density-corrected, it is possible to compensate for the effects of changes in the sensitivity and gamma characteristics of the recording medium, deterioration of the light emitter and heating element, environmental changes, and the like.

[Brief explanation of the drawing]

Figure 1 shows the gamma characteristic curve of a specific color of color photographic paper, Figure 2 shows the light intensity characteristics with respect to the voltage applied to the FOT as a recording section, and Figure 3 shows the digital equivalent of the voltage applied to the FOT. FIG. 4 is a diagram showing density characteristics of color photographic paper with respect to bit values, FIG. 4 is a diagram for explaining correction, and FIGS. 5 to 7 are diagrams showing density correction circuits according to embodiments of the present invention. Agent Patent Attorney” = Tsuneaki Nagao Figure 3 (Koito Bank L

Claims (6)

[Claims] (1) A recording apparatus having a recording section that receives an image signal and scans a recording medium to record an image corresponding to the image signal, comprising a density correction means for correcting the density of the image, the density correction means A recording device characterized in that the image signal corrected by the above is input to the recording section. (2) The recording apparatus according to claim 1, wherein the density correction means includes means having correction data corresponding to the sensitivity of the recording medium, environmental conditions, etc. (3) Claim 1 or 2, characterized in that the density correction means has a look-up table.
Recording device as described in section. (4) The recording device according to claim 3, wherein the look-up table contains two or more types of gradation data, one of which can be artificially selected. . (5) The recording apparatus according to claim 1 or 2, wherein the density correction means includes an operational amplifier. (6) The first aspect of the present invention is characterized in that the density correction means includes test pattern generation means that is connected to the image signal and selectively to the density correction means at a preceding stage thereof.
Recording device as described in section.