KR100316446B1 - Device for expanding light-amount correction dynamic range - Google Patents

Abstract

(Problem) Even if the exposure gradation number is increased in order to enlarge the exposure dynamic range, the cost can be reduced without increasing the storage capacity of the light amount correction storage unit.

(Solution means) In order to increase the number of exposure gray levels, the input data is n + k bits, and the LUT1 stores the output concentration with respect to the number of exposure gray levels for each sensitivity of the entire photosensitive agent. The output n + k bits of LUT1 are selected only valid n bits from selector 1 to use the m bits required by the photosensitizer and are output to LUT2. In the LUT2, luminance information for correcting luminance unevenness of the light emitting dot of the printhead is stored in a capacity equivalent to n bits, and temporarily stored in the n-bit equivalent FIFO. The output of the FIFO is again converted to n + k bits by the selector 2 and output to the gradation control means 4, and the printhead is gradation controlled to n + k bits. At this time, the luminance unevenness is corrected to n bits, but in the present situation, the necessary precision is sufficient.

Description

Light quantity correction dynamic range expansion device {DEVICE FOR EXPANDING LIGHT-AMOUNT CORRECTION DYNAMIC RANGE}

INDUSTRIAL APPLICABILITY The present invention is applied to an optical printer using a fluorescent display tube as a light source of a printhead in order to form an image on a photosensitive film in a color printer, and extends a light quantity correcting dynamic range in which light quantity correction of the printhead is performed to enlarge the exposure dynamic range. Relates to a device.

In an optical printer such as a color video printer, a fluorescent display tube having a plurality of light emitting dots is used as a light source of a printhead to form an image on a photosensitive member (photo paper or photosensitive film) having a photosensitive agent.

Since each light emitting dot of this printhead has brightness unevenness, the light quantity correcting circuit corrects and outputs this uneven brightness.

7 is a configuration diagram showing a conventional light quantity correction circuit.

In order to enlarge the light quantity dynamic range of the optical printer using a plurality of photosensitizers having different sensitivity, it is configured to increase the number of exposure grayscales, that is, increase the data bit width of the input data and the exposure process.

For example, the bit width of the input data is n (for example, 8 bits) as image data of bit width n + k (when the increase k is 3 bits wide in total 11 bits wide).

The input data refers to the lookup table LUT1 for the sensitivity correction of the photosensitive agent, that is, the characteristic line corresponding to the concentration distribution characteristic of the photosensitive agent, and an exposure gray level corresponding to the photosensitive agent being used is obtained.

Thereafter, the light quantity is corrected, that is, obtained by referring to the lookup table LUT2 which stores the characteristic of the output density corresponding to the exposure gray level in order to correct the luminance unevenness of the light-emitting dot, and temporarily stores it in the temporary storage memory 31 such as FIFO. The output is output to the printhead via the gray scale control means (driver circuit) 32 of the printhead.

As described above, even when the input / output data lines are all n + k bit widths (11 bits), the measurement accuracy of the photometer is about 1% and the accuracy of 8 bits of resolution (1/256 = 0.4%) or more. You can't.

The LUT2 stores correction data for correcting luminance unevenness of each dot of the printhead. The LUT2 is generated from measurement data measured by a light quantity meter at the time of manufacture of the printhead, and exposed at 8 bits (256 gray scales). From the beginning, the width has an error of about 2.5 gradations.

Therefore, even if the input / output data line is increased to n ≥ 8 (bits), the precision of the light quantity measuring instrument cannot be improved, and the bit of this increment k only increases the capacities of LUT2 and FIFO. There is no effect of improving image quality.

In addition, since LUT2 requires high-speed access, expensive ones such as SRAM are used. However, increasing unnecessary capacity of this LUT2 only increases costs and wastes memory.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and even when the number of exposure gradations is increased in order to enlarge the exposure dynamic range, the light quantity correction dynamic range can be lowered without increasing the storage capacity of the light quantity correction storage unit. It is an object to provide a device.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing a light amount correcting dynamic range expanding apparatus of the present invention.

Fig. 2 is an input / output characteristic diagram of LUT1 of the same apparatus, and the output density with respect to the exposure amount is shown for each film having different sensitivity.

3 is a diagram showing n-bit selection states of selectors 1 and 2 (film 1).

4 is a diagram showing an n-bit selection state of selectors 1 and 2 (film 2).

Fig. 5 shows the n-bit selection states of selectors 1 and 2 (film 3).

Fig. 6 shows the n bit selection states of selectors 1 and 2 (film 4).

7 is a view showing a conventional light amount correction circuit.

(Explanation of symbols for the main parts of the drawing)

2a: n + k bit busline 2b: n bit busline

3: Temporary storage memory (FIFO) 4: Gradation control means

LUT1: Lookup Table (For Sensitivity Correction) LUT2: Lookup Table (For Luminance Stain Correction)

In order to solve the above problems, the light quantity correcting dynamic range enlargement apparatus of the present invention corrects the luminance unevenness of each light emitting dot of the print head resulting from the light emitting dots arranged in a line shape as described in claim 1, In the apparatus for enlarging the light quantity correction dynamic range by increasing the number of exposure gray scales by using a photosensitive member of a plurality of different photosensitive agents,

A first lookup table having a storage capacity corresponding to input data enlarged by n + k bits, for storing an output concentration corresponding to an exposure gray level for each type of the entire photosensitive agent;

Among the n + k bits of data output from the first lookup table, the m bits (n ≦ m ≦ n + k) required for the photosensitive agent used (n ≦ m ≦ n + k) are used as the exposure gradation, and the low (mn) bits are higher than the two selectors. a first and second selectors for selecting the remaining n bits without selecting the sum (k) bits of the (n + km) bits;

A second lookup table provided between the first selector and the second selector, in which luminance information for correcting luminance unevenness of each light emitting dot of the printhead is stored in a capacity equivalent to n bits, and the first selector A temporary storage memory provided between the second selector and the exposure data of one line of the print head at a capacity equivalent to n bits;

And a gradation control means provided at the rear end of the second selector and controlling light emission of each light emitting dot of the printhead based on data enlarged by the n + k bits.

When the exposure gradation number is increased to n + k bits in order to enlarge the exposure dynamic range, the n + k bits of input data are input to the apparatus.

The lookup table 1 stores an output density corresponding to the number of exposure gradations in the photosensitive agent having various sensitivity at a resolution equivalent to n + k bits.

Since the m bits are used as the exposure gradation among the output n + k bits of the lookup table 1, the first selector does not select the sum (k) bits of the lower (mn) and upper (n + km) bits, Selects n bits to output to the second lookup table.

The second lookup table and the temporary storage memory that store the luminance information for correcting the luminance unevenness of the light emitting dot of the printhead can be configured with a capacity equivalent to n bits.

The output n bits of the temporary storage memory are increased by n + k bits by the second selector and input to the gradation control means.

The gradation control means controls the gradation of the print head with a resolution of n + k bits, but corrects the inner luminance unevenness by n bits based on the output of the temporary storage memory.

1 is a block diagram showing a light amount correction dynamic range expanding apparatus of the present invention.

In the apparatus 1, the same code | symbol is attached | subjected to the same component part as before.

The input data is input to the lookup table LUT1 for sensitivity correction of the photosensitive film, that is, the concentration distribution characteristic of the photosensitive agent is discretized and stored (concentration distribution characteristic line). This LUT1 is composed of a storage element such as a RAM.

The input data has a predetermined bit width n + k (n = 8, 11 bits in total of k = 3) and is input to the LUT1 via the bus line 2a of the corresponding bit width n + k.

LUT1 outputs an exposure gradation number corresponding to the photosensitive film being used. 2 is an input / output characteristic diagram of the LUT1, and data of a predetermined concentration is output in correspondence with a predetermined exposure amount indicated by the input data.

In this LUT1, concentration distribution characteristic lines relating to the photosensitive film are stored, and the input / output relationship shown in FIG. 2 is obtained based on this concentration distribution characteristic line.

Specifically, at the time of changing the sensitivity of the photosensitive film, the concentration distribution characteristic line corresponding to this sensitivity is written in LUT1.

The output of LUT1 is connected to selector 1. Selector 1 converts the n + k bit width output from LUT1 to n bit width and selects a corresponding bus line based on a control signal input through a control line from a control unit (CPU) (not shown). Connect. In other words, the selected 8-bit wide bus line among the 11-bit wide bus lines 2a is connected to the 8-bit wide bus line 2b, and the other 3-bit wide portions are not connected to the bus line 2b. Shall be. This bit selection condition is described later.

Selector 1 and LUT2 are connected to the n-bit bus line 2b. The LUT2 stores light characteristics for correcting lightness unevenness of the light emitting dots of the print head, that is, characteristics of the output density corresponding to the exposure gray level.

Temporary storage memories 3 such as LUT2 and FIFO are also connected to the n-bit bus lines 2b, and the output of LUT2 is temporarily stored in the temporary storage memory 3.

Both of these LUT2 and the temporary storage memory 3 have a capacity for storing the n-bit data.

The bus line 2b of the bit output by the temporary storage memory 3 is connected to the selector 2. As shown in FIG. The selector 2 converts and outputs the bit width of n output from the temporary storage memory 3 into n + k bit widths, and selects and connects the corresponding bus lines based on the control signal from the CPU, similarly to the selector 1. That is, based on the bit selection conditions described later, the bus lines of the 8-bit width selected from the bus lines 2b of the overall 8-bit width are connected to the bus lines 2a of the 11-bit width. Other 3-bit wide bus lines that are not directly connected are fixed at H or L.

The output of the selector 2 is input to the gradation control means 4 via the bus line 2a of the bit width n + k. The gradation control means 4 is constituted by a driver IC for driving a printhead, and the input data has a resolution of n + k bit width (11 bits) and controls gradation control of the printhead.

As shown in Fig. 2, the exposure gray level of the LUT1 is a resolution of 11 bits in total, which corresponds to different photosensitive members as shown. In this example, it is assumed that four types of photosensitive members of different photosensitive agents are used.

The inner film 1 is a photosensitive film having the highest sensitivity of the photosensitive agent, and gradually decreases the sensitivity in order of the films 2 and 3, and the film 4 is the photosensitive film having the lowest sensitivity of the photosensitive agent.

As shown, when the exposure gradation number is set to 11 bits of resolution, the film 4 having the lowest sensitivity has the density characteristic distribution discretized over the entire gradation number (2048 gradations), but the density characteristic of the film 1 having the highest sensitivity. The distribution is saturated near 256 gradations. Moreover, film 2 is saturated near 512 gradations, and film 3 is saturated near 1024 gradations.

As described above, when the number of exposure tones of LUT1 is set to 11 bits of high resolution and the configuration is set to the film having the least sensitivity, the more tones that are relatively sensitive, the more tones decrease.

Therefore, the bit combinations of the bus lines 2b most suitable for each of the above films 1 to 4 are selected, and n-bit (8-bit) bus connections are made for all films. 3 to 6 are diagrams showing the selected connection state of the selectors 1 and 2, respectively.

Here, with respect to the n + k-bit bus line 2a, when m bits (n ≦ m ≦ n + k) are used as the exposure gradation according to the sensitivity characteristic of the film (photosensitive agent), they differ from the lower (mn) bits. (n + km) The remaining n bits are selected without selecting the sum (k) bits of the bits (bit selection condition).

3, the selective connection state regarding the film 1 is shown.

Film 1 of high sensitivity saturates around 8 bits (256 gray scales) even with 11 bits of resolution, so m = 8, n = 8, k = 3, and the upper 3 bits of the total 11 bits based on the bit selection conditions. Is not connected to the bus line 2b. Selector 1 opens the output ports of the upper 3 bits (10, 9, 8 bits), and selector 2 ensures that the output of the upper 3 bits is a fixed value (L). Accordingly, the film 1 can obtain an 8-bit 256-gradation resolution in one gradation step.

4, the selective connection state regarding the film 2 is shown.

Slightly sensitive film 2 saturates around 9-bit equivalent (512 gradations) at 11-bit resolution, so m = 9, n = 8, k = 3, and selector 1 shows the upper two bits ( The output ports of 10 and 9 bits) and the least significant bit (0 bits) are opened, and the selector 2 is such that the output ports of the same bits are fixed values (L). As a result, the film 2 can obtain an 8-bit 256-gradation resolution in two-gradation steps.

5, the selective connection state regarding the film 3 is shown.

Slightly low film 3 saturates around 10-bit equivalent (1024 gradations) at an 11-bit resolution, so m = 10, n = 8, k = 3, and the upper 1 bit in selector 1 based on the selection conditions. The output ports of (10 bits) and least significant 2 bits (0, 1 bit) are opened, and the selector 2 is such that the output of the same bits is a fixed value (L). Thereby, the film 3 can obtain the resolution of 8-bit 256 gradation in 4 gradation steps.

6, the selective connection state regarding the film 4 is shown.

Film 4 of the lowest sensitivity saturates around 2048 gradations of 11-bit resolution, so m = 11, n = 8, k = 3 and the least significant 3 bits (0, 1, 2) in selector 1 based on the selection conditions. Bit) output port, and selector 2 sets the output of the same bit to a fixed value (L). Thereby, the film 4 can obtain the resolution of 8-bit 256-gradation in 8-gradation steps.

In this manner, by forming 8 bits between the selectors 1 and the selector 2 with respect to all the films 1 through 4, the storage capacity equivalent to 8 bits with respect to the LUT2 and the temporary storage memory 3 provided between the selectors 1 and the selector 2 is reduced. Can be provided, and an insignificant increase in capacity of these LUT2 and the temporary storage memory 3 can be prevented.

And in order to select the effective n-bit corresponding to a plurality of types of film, the control signal based on following formula (1) is output to the selector 1, 2.

smallest integer that satisfies x ≥ log ₂ (k + 1) x ... (1)

Therefore, based on said Formula (1), the control signal at the time of using four types of films like the said structure can be selected by the control signal like 4 in total with 2 bits. As a result, two control lines are connected between the selectors 1 and 2 and the CPU.

In the above configuration, the selectors 1 and 2 are constituted by selector ICs, and bit selection is performed based on a control signal from the CPU via the control line. However, the selectors 1 and 2 may be constituted by mechanical rotary switches.

According to the present invention, even when the number of exposure gradations is increased to n + k bits in order to enlarge the exposure dynamic range, only effective n bits are selected between the selector 1 and the selector 2 corresponding to the m bits required for the photosensitive agent to be used. And a storage unit for storing and correcting the luminance unevenness of the print head between the selector 1 and the selector 2, thereby storing the luminance unevenness correction with the minimum capacity and the precision necessary for the device sufficiently. To do it.

As a result, the exposure dynamic range can be increased by increasing the number of exposure gray scales without increasing the apparatus cost.

Claims (11)

In the apparatus for correcting the luminance unevenness of each light emitting dot of the print head consisting of light emitting dots arranged in a line shape, and to increase the light intensity correction dynamic range by increasing the number of exposure gray scales using a photosensitive member of a plurality of photosensitive agents having different sensitivity. In A first lookup table having a storage capacity corresponding to input data enlarged by n + k bits for storing an output density corresponding to an exposure gray level for each type of the entire photosensitive agent; Among the n + k bits of data output from the first lookup table, a low (mn) bit is formed between both selectors to use m bits (n ≦ m ≦ n + k) necessary for the photosensitive agent used as the exposure gray level. First and second selectors for selecting the remaining n bits without selecting the sum (k) bits of the upper (n + km) bits; A second lookup table provided at a rear end of the first selector, in which luminance information for correcting luminance unevenness of each light emitting dot of the printhead is stored in a capacity equivalent to n bits; A temporary storage memory provided between the second lookup table and the second selector, in which exposure data of one line of the printhead is stored at a capacity equivalent to the n-bit; A gradation control means provided at the rear end of the second selector and controlling light emission of each light emitting dot of the print head based on data enlarged by the n + k bits. Light amount compensation dynamic range expansion apparatus comprising a. The memory of claim 1, wherein the first selector converts a bit width of (n + k) output from the first lookup table into an n bit width, and the second selector outputs n bits output from the temporary storage memory. A light quantity correction dynamic range enlargement device, characterized in that the width is converted into (n + k) bit widths. 2. An apparatus according to claim 1, wherein said temporary storage memory includes a FIFO (first in, first out) memory. The apparatus according to claim 1, wherein each of the first selector and the second selector executes bit selection based on a control signal from a CPU (central processing unit). 2. An apparatus according to claim 1, wherein said first selector comprises a mechanical rotary switch and said second selector comprises a mechanical rotary switch. A device for correcting the luminance unevenness of each light emitting dot of a print head composed of light emitting dots arranged in a line shape and increasing the number of exposure gray scales by using a photosensitive member of a plurality of photosensitive agents having different sensitivities to expand the light quantity correction dynamic range. In A first lookup table having a storage capacity enlarged with (n + k) bit input data for storing respective output concentrations corresponding to the exposure gray levels classified by the photosensitive agent; In order to use the m bits (n ≦ m ≦ n + k) required for the photosensitive agent as the exposure gradation, except for the low (mn) bit and the high (n + km) bit, the outputs are output from the first lookup table (n + k) a first selector (n, m, and k are non-zero integers) configured to select up to n bits from among bits of data; In order to use the m bits (n ≦ m ≦ n + k) required for the photosensitive agent as the exposure gradation, except for the low (mn) bit and the high (n + km) bit, the outputs are output from the first lookup table (n + k) a second selector configured to select at most n bits from among bits of data; A second lookup table disposed between the first selector and the second selector and configured to store luminance information used to correct luminance unevenness between light emitting dots of the print head; A temporary storage memory disposed between the first selector and the second selector, configured to store exposure data for one line of the printhead, and having a memory capacity smaller than the n bits; And And a gradation control means provided at the rear end of the second selector and configured to control the luminance of each of the light emitting dots of the printhead based on the data enlarged by (n + k) bits. Dynamic Range Expander. 7. An apparatus according to claim 6, wherein said second lookup table is connected in series to said temporary storage memory. The bit selector of claim 6, wherein the first selector converts the (n + k) bit width output from the first lookup table into n bit widths, and the second selector outputs n bit widths from the temporary storage memory. A dynamic range expansion device for light quantity correction, characterized by converting to (n + k) bit width. 7. An apparatus according to claim 6, wherein the temporary storage memory includes a FIFO (first in, first out) memory. 7. An apparatus according to claim 6, wherein each of said first selector and said second selector executes bit selection based on a control signal from a CPU (central processing unit). 7. An apparatus according to claim 6, wherein said first selector comprises a mechanical rotary switch and said second selector comprises a mechanical rotary switch.