JPH06255173A - Image recording apparatus - Google Patents

Abstract

PURPOSE:To prevent the density irregularity by changing the ratio of a first and a second times of a first image signal by means of a second image signal generating means and outputting the ratio to a light emitting means. CONSTITUTION:When a random numbers generator 27 inputs a random numbers signal VR of (m) bits to a random numbers converter 30 synchronously with a clock signal, the random numbers converter 30 converts the random numbers signal VR to a random numbers signal V1 of a different value. The converted random numbers signal V1 is sent to a random numbers detecting part 31 via a latch 28. The random numbers detecting part 31 detects a symbol of a random numbers (y) represented by the random numbers signal V1, and outputs V3 (+/-signal) indicating the symbol to an AND/OR circuit 33. Moreover, the random numbers detecting part 31 detects an absolute value of the random numbers (y) ¦y¦ and outputs as a signal V2 to a selector 32. The selector 32 extracts a terminal corresponding to the absolute value ¦y¦ from (n) terminals I1-In, and outputs a signal delayed by a selected delay circuit Di as an image signal Vdi to the AND/OR circuit 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus for controlling light emission of a light beam according to an image signal and scanning the light beam onto a photosensitive material to record an image.

[0002]

2. Description of the Related Art As a method for forming an image on a photosensitive material (hereinafter referred to as a film) based on a halftone dot signal generated by a halftone dot generator, a focusing optical system having a light emitting source is used. Is used. An example of an image recording apparatus using such an image forming optical system is one using a polygon mirror (rotating polygon mirror), an f.theta. Lens, and a laser diode (referred to as LD) (see FIG. 1 described later).
reference). In this case, as the film, for example, FIG.
A lith film having a density-light quantity characteristic as shown in 3 is widely used. Therefore, it is necessary to set the light amount of the light applied to the film to a value equal to or more than the light amount required for the film to be exposed (light amount P _{TH in} FIG. 13).

[0003]

However, due to the following reasons, the exposure amount per unit area on the film cannot reach the critical exposure amount of the film, and there are cases where the film is not sufficiently blackened. . As such a reason, it can be mainly mentioned that the resolution of the imaging optical system is lowered. Specifically, it is as follows.

When the depth of focus of the imaging optical system (f.theta. Lens or the like) is deepened, the light beam cannot be sufficiently narrowed down, so that the light beam becomes thick and the resolving power is lowered. On the contrary, if the light flux is sufficiently narrowed down, the depth of focus becomes shallow, which is contrary to the following reasons.

Since the mechanical accuracy of the focal plane of the imaging optical system is not high enough to absorb the influence of the depth of focus described above, unfocused light flux is projected onto the focal plane, which is a so-called out-of-focus state. As a result, the resolution was further reduced.

In plane scanning, where scanning over the film,
Since the optical focal plane is curved, the image is out of focus and the resolution is further reduced.

When the film is irradiated with a light beam which is not sufficiently narrowed down for the above reasons (1),
As shown in (b), the exposure amount 13 cannot reach the critical exposure amount 12 of the film, so that the film is not blackened. For this reason, an accurate halftone dot area cannot be secured, and uneven density occurs. On the other hand, FIG. 14A shows the case where a sufficiently narrowed luminous flux is applied, and the shaded portion in the drawing is the blackened portion.

Here, the point that a desired halftone dot shape cannot be obtained when a light beam that is not sufficiently narrowed down due to the above-mentioned reasons is irradiated will be specified. FIG. 15 is a diagram showing the exposure amount per unit area when the light beam is scanned in the main scanning direction X. In the figure, 13 is the exposure amount when a light beam that cannot reach the critical exposure amount 12 is irradiated, and the broken line 1
Reference numeral 5 denotes an exposure amount when a light beam in an ideal state (a sufficiently narrowed state) is emitted. When the ideal light beam represented by the broken line 15 is irradiated, the exposure area (ON range) becomes the range X ₀ . However, when the light amount of the light beam is the exposure amount 13, the exposure amount is represented by the alternate long and short dash line 14 when viewed as a whole,
In this case, the substantial exposure area is the range X ₁ (X ₁ <
X ₀ ), and portions corresponding to both ends of the halftone dot shape that should be originally obtained are not exposed. FIG. 16 schematically shows this state. As shown in the figure, an unexposed portion 10 is generated and a blackened portion 11 is reduced with respect to a desired halftone dot shape (50% halftone dot).

Further, as described above, when the overlapping portion of exposure is small (cumulative exposure amount <critical exposure amount), an unblackened portion is generated at a contact between adjacent halftone dots, and such an unblackened contact is formed. As a result of continuous macros, regular unevenness of light and shade occurs (see FIG. 17).

On the other hand, as shown by the chain double-dashed line 16 in FIG. 15, when the exposure amount 16 becomes unnecessarily large due to the output variation of the LD or the like, on the contrary, the exposure region is the range X ₃ (X
₃ > X ₀ ), and even in this case, the desired halftone dot shape cannot be realized. That is, in this case, it is necessary to reduce the actual exposure amount.

Therefore, in order to correct such a problem,
It is necessary to manufacture an imaging optical system that does not cause curvature in the focal plane both mechanically and optically. However, such fabrication is technically extremely difficult.

In addition, an external factor also affects the exposure amount. For example, the light amount of the LD may change depending on the temperature characteristics and the aging characteristics, and the critical exposure amount may change depending on the conditions at the time of developing the film. There is a demand for an image recording apparatus that can improve the unevenness of light and shade that occurs on the film, taking such external factors into consideration.

[0013]

SUMMARY OF THE INVENTION The present invention has been made based on the above problems and demands, and a first object of the present invention is to prevent occurrence of regular unevenness of light and shade on a photosensitive material. .

A second object of the present invention is to prevent the occurrence of such unevenness of light and shade in accordance with the information required for image recording.

Further, according to a third aspect of the present invention, it is possible to realize the prevention of the uneven density while changing the halftone dot area ratio in various ways.
The purpose is.

[0016]

According to a first aspect of the invention, (a) a storage unit for storing and outputting a first image signal representing an image to be recorded and (b) a storage unit connected to the first After changing the ratio of the first time when the image signal is at the first level and the second time until the image signal returns to the first level after changing from the first level to the second level, it is output as the second image signal. A second image signal generating means, (c) a light emitting means connected to the second image signal generating means, for emitting a light beam when the second image signal is at the first level, and (d) a light beam for the photosensitive material. And scanning means for scanning upward to record an image on the photosensitive material.

The invention according to claim 2 is the invention according to claim 1, further comprising (e) an input signal generating means for outputting to the second image signal generating means an input signal giving information necessary for image recording. The second image signal generating means is a means for changing the ratio according to the information instructed by the input signal.

The invention according to claim 3 is the invention according to claim 1, wherein: (f) a clock signal generating means for outputting a clock signal for giving an output timing of the first image signal to the storage means; It further comprises: a random number generation unit connected to the clock signal generation unit and outputting a random number signal for instructing a random number to the second image signal generation unit according to the clock signal, the second image signal generation unit responding to the random number signal. This is a means for randomly changing the ratio.

The invention according to claim 4 is the invention according to claim 3, further comprising: (h) an input signal generating means for outputting to the random number generating means an input signal giving information necessary for image recording, The generating means is means for outputting a random number signal within a range according to the information.

[0020]

In the invention according to claim 1, the second image signal generating means receives the first image signal and changes the ratio of the first time and the second time included in the first image signal to obtain the second image. The signal is output to the light emitting means. The light emitting means receives the second image signal and emits a light beam within the time when the second image signal is at the first level, and the light beam is emitted by the scanning means only during the time when the second image signal is at the first level. Scanned over. That is, the second image signal generating means controls the irradiation time of the light beam on the photosensitive material.

According to the second aspect of the present invention, the second image signal generating means controls the irradiation time of the light beam onto the photosensitive material in accordance with the information required by the input signal generating means for image recording.

In the invention according to claim 3, while the first image signal is supplied to the second image signal generating means in synchronization with the clock signal, the random number generating means also outputs the random number signal to the second image signal generating means. . The second image signal generating means is
The ratio of the first time and the second time of the first image signal is randomly changed according to the random number signal. That is, the second image signal generating means randomly controls the irradiation time of the light beam on the photosensitive material.

In the invention according to claim 4, the second image signal generating means is a ratio of the first time and the second time of the first image signal within a range determined according to information necessary for image recording. Will be changed at random.

[0024]

【Example】

 A. First embodiment

(1) Optical / Mechanical Structure of Image Recording Device

FIG. 1 is a perspective view schematically showing the mechanical and optical structure of the image recording apparatus. The configuration shown in this figure is a component common to each of the embodiments other than the first embodiment described below.

The LD1 oscillates in response to the drive signal V _DR created from the image signal. The polygon mirror 2 rotates about its axis 8 and emits a light beam LB emitted from the LD 1.
Is reflected in the direction of the f · θ lens 3. Then, the light beam LB is scanned in the main scanning direction X on the film 4 (lith film) via the f · θ lens 3. In this case, as is known, the scanning speed of the light beam LB in the main scanning direction X is proportional to the angular speed of the polygon mirror 2.

On the other hand, the film 4 is moved in the sub-scanning direction Y by the cylinder 5 rotating around the central axis 9 and the pressing rollers 6 and 7.

The scanning range of the light beam LB on the film 4 is narrower than the scanning range of the light beam LB in the main scanning direction X (see FIG. 7).

(2) Electrical configuration of image recording device

FIG. 2 is a block diagram showing the electrical construction of the drive portion of the LD1. First, the image signal V _I to be recorded
Are stored in the dot generator 18 in advance. The dot generator 18 generates a serial image signal V _IMG (1 bit signal) from a parallel image signal V _I and latches the image signal V _IMG for each scanning line 20.
Output to. The main image signal V _IMG is a beam ON / OFF signal for turning ON / OFF the light emission (light beam LB) of the LD 1. That is, a desired halftone dot is formed according to the image signal V _IMG .

The latch 20 includes a clock generator 19
Are connected, and the latch 20 synchronizes with the image signal V _CL in synchronization with the clock signal V _CL output by the clock generator 19.
Outputs ₀ .

[0033] The output terminal of the latch 20, (n-1) I n terminals and OR number of delay circuits D ₁ ~D _n-1 and the selector 22
One input end of the circuit 23 is connected. Moreover,
The output terminals of the delay circuits D _{1 to} D _n-1 are connected to the I _{1 to} I _n-1 terminals of the selector 22, respectively, and the output terminal O of the selector 22 is the other input terminal of the OR circuit 23. It is connected to the.

On the other hand, the numerical value generator 21 has an input unit 25 (C
It stores a constant numerical value (displayed in m bits) commanded by an input signal V _IN given from a portion provided with a PU, a keyboard, etc.). This numerical value is one of the n terminals I _{1 to} I _n of the selector 22.
It is a value indicating _i (i: 1 to n). Therefore, n = 2
The relationship of ^m is established. Further, the clock generator 19 is connected to the control end of the numerical value generator 21. Therefore, the numerical value generator 21 outputs the signal V _S for instructing the numerical value to S ₁ of the selector 22 in synchronization with the clock signal V _CL.
And outputs it to the ~S _m terminal. As a result, the selector 22 determines that S
In synchronization with the signal V _S given in ₁ to S _m terminal, selects a terminal to which the signal V _S is corresponding to a number of instructions from the _I I ~I _n-1 terminals or I _n terminal. In this case, different delay amounts are set for the delay circuits D _{1 to} D _n-1 .

The output end of the OR circuit 23 is connected to the LD drive circuit 2
4 and the output end of the LD drive circuit 24 is connected to LD1.

(3) Operation of LD drive section

It is now assumed that the input signal V _IN is a signal for instructing the i-th I _i terminal of the selector 22. In this case, the numerical value generator 21 outputs the numerical value corresponding to the I _i terminal as the signal V _S. As a result, part of the image signal V ₀ is input to the i-th delay circuit D _i (set to the delay time Δt _i ) and part of it is directly input to the OR circuit 23. The image signal V ₀ input to the delay circuit D _i is delayed by the delay time Δt _{i and then} output from the O terminal of the selector 22 to the OR circuit 23 as the delayed image signal V _Di. When i = n, the delay time Δt _n is 0 and the relationship V _Dn = V ₀ is established. The above-mentioned delay is shown in the timing chart of FIG.

FIG. 3A shows the image signal V ₀ (first image signal). In this example, its level is time t.
_It is assumed that it is at H level (corresponding to the first level) from ₁ to time t ₂ , and at L level (corresponding to the second level) from time t ₂ to time t ₄ . That is, H
The time at the level and the time at the L level are equal to each other and are both time T ₀ . On the other hand, the delayed image signal V _Di is the image signal V _{0 as} shown in FIG.
The signal is delayed by the delay time Δt _i . As a result, the image signal V _B (corresponding to the second image signal) which is the output signal of the OR circuit 23 is at the H level from time t ₁ to time t _{3 as} shown in FIG. , Time t ₃
From the time to the time t ₄ , the signal is at the L level. In this way, the image signal V _B becomes a signal that the time at the H level is longer than the time at the L level. In this case, the ratio γ between the time T ₁ when the image signal V _B is at H level and the time T ₂ when it is at L level is γ = T ₁ / T ₂ =
(T ₀ + Δt _i ) / (T ₀ −Δt _i )> 1. This image signal V _B is passed through the LB drive circuit 24 to drive signal V _DR.
Therefore, in this embodiment, the lighting time of the LD1 becomes longer by the delay time Δt _i than in the case where the image signal V ₀ is directly applied to the LD1.
Note that FIG. 3D shows the time axis.

In this way, the lighting time of the LD1 is set to the delay time Δ
Since the length is extended by t _i, even when the film 4 is irradiated with the light flux whose exposure amount per unit area does not reach the critical exposure amount, the number of overlapping exposure portions increases, resulting in the accumulation per unit area. It is possible to secure the light amount above the critical exposure amount. FIG. 4 schematically shows this point. As shown in the figure, since the shaded portion is the overlapping exposure, the exposure amount can be increased as a whole, and the portion having the critical exposure amount or more is blackened. In this case, since the light beam LB is continuously scanned in the main scanning direction X, the overlapping exposure portions are successively generated, and it is possible to prevent the occurrence of density unevenness that appears macroscopically.

Here, in the timing chart shown in FIG. 5 ((d): time axis), (a) shows the clock signal V _CL and (b) shows the image signal V ₀ . However, FIG.
In the figure, black (exposure) and white (no exposure) are alternately repeated. Therefore, as the image signal V ₀ , H level and L level are alternately repeated 1
It becomes a bit signal. The image signal V _B obtained in this embodiment is just equivalent to the signal shown in FIG. That is, the signal at the H level is uniformly extended by the delay time Δt (here, the delay time is referred to as Δt).

On the other hand, FIG. 6 does not show a case in which black and white are alternately and repeatedly exposed as shown in FIG.
The case of exposure is shown as black, black, black, white, white, black, black ((a): clock signal V _CL , (b): image signal V ₀ ). Also in this case, the image signal V _B has a delay time Δ of a time when it is at the H level, as shown in FIG.
The signal is extended by t.

The value of the input signal V _{IN supplied} from the input section 25 can be variously changed according to the information required for image recording. That is, depending on such information,
A delay circuit can be selected to control the extension time of the lighting time of the LD1. Such information includes the following.

First, the value of the numerical value output by the numerical value generator 21 can be changed according to the screen ruling.
In this case, when the number of screen lines is increased, the time during which the image signal V _B is in the H level time may be shortened (the ratio γ may be decreased), so that a delay circuit having a shorter delay time Δt _i may be used. Numerical generator 2 to choose
The value to be stored in 1 should be set.

On the contrary, when it is desired to further reduce the number of screen lines, the numerical value is determined so that the delay circuit having the longer delay time Δt _i is selected.

In addition, according to the value of the recording linear density, LD1
It is also possible to control the extension time of the lighting time of. Here, the recording linear density corresponds to the center-to-center distance between adjacent exposure pixels. In this case, when it is desired to set the recording linear density to a large value, the time during which the image signal V _B is at the H level may be shortened, and therefore, the delay circuit having the short delay time Δt _i is stored in the numerical value generator 21. It is only necessary to set the numerical value to be set. On the contrary, when the value of the recording linear density is set small, it is necessary to set the numerical value so as to select the delay circuit having the longer delay time Δt _i .

Further, depending on the self-developing characteristic of the film 4,
It is also possible to determine the numerical value to be stored in the numerical value generator 21. That is, since the critical exposure amount may need to be changed depending on the development conditions after the film 4 is exposed, it is necessary to determine the exposure amount in consideration of this manifest characteristic. Therefore, it is necessary to control the lighting time of LD1. In consideration of this point, an appropriate numerical value from the input unit 25,
That is, the input signal V _IN for instructing an appropriate delay circuit is given to the numerical value generator 21.

Furthermore, since it is necessary to control the lighting time of the LD 1 in consideration of the change in the light amount of the LD 1,
The delay circuit can be selected according to the observation result of the light amount of 1. In this case, the amount of LD1, in order to vary the temperature characteristics and aging characteristics, etc., when the light amount becomes greater, it is necessary to reduce the exposure amount, a short delay of more delay time in this case Delta] t _i A numerical value for selecting a circuit is stored in the numerical value generator 21. LD on the contrary
When the light amount of 1 decreases, it is necessary to increase the exposure amount. Therefore, in order to increase the ratio γ described above, a numerical value for selecting a delay circuit having a longer delay time Δt _i is determined.

As a method of measuring the light quantity of the LD 1, there is a method as shown in FIG. 7, for example. That is, the optical sensor 32 is provided on the extension of the central axis 9 of the cylinder 5, and the optical sensor 32 detects the light beam LB and outputs the light amount signal to the current / voltage converter 33. The signal converted by the current / voltage converter 33 is sent to the CPU 35 via the A / D converter 34, and the CPU 35 determines a numerical value indicating an appropriate delay circuit according to the result of the detected light amount signal. , And outputs the result as the input signal V _IN2 to the above-mentioned numerical value generator 21 and stores it.

When the numerical value stored in the numerical value generator 21 is changed according to the value of the screen ruling or the like as described above, the extension time of the lighting time of the LD 1 can be changed according to the change. In the case of FIG. 5C described above, the delay time Δt changes as the above numerical values are changed.

Although the numerical value generator 21 outputs the signal V _S in synchronization with the clock signal V _CL in the first embodiment, the present invention is not limited to this. For example, it is possible to always output the signal V _S giving a numerical value by a clock signal different from the clock signal V _CL . In this case, the clock signal serves as a start signal for outputting the signal V _S.

Further, in the first embodiment, the H level corresponds to the first level and the L level corresponds to the second level, but the opposite form (the first level to the L level and the second level to the H level). It can also consist of levels). Further, in addition to the LD1, a light emitting diode or the like can be used as a light emitting element. With respect to these points, the same holds true in each of the examples described later.

B. Second embodiment

FIG. 8 shows the electrical construction of the LD drive section in the second embodiment, and the other construction is similar to that of the first embodiment. The second embodiment is different from the first embodiment described above in that an AND circuit 26 is provided instead of the OR circuit 23. The other points are the same as those in the first embodiment. By forming the image signal V _B1 using this AND circuit 26, it is possible to control the lighting time of the LD 1 to be short, contrary to the case of the first embodiment. That is, the second embodiment is to cope with the case where the exposure amount of the light beam irradiated on the film 4 is the exposure amount 16 in FIG.

9A to 9C show timing charts of the image signals V ₀ , V _Di , and V _B1 respectively. However, FIG. 7D is a time axis. Also in this figure, as in FIG. 3, the image signal V ₀ changes from the time t ₁₁ to the time t
_It is at the H level until ₁₃ and is at the L level from time t ₁₃ to time t ₁₄ . Therefore, the ratio γ of the image signal V ₀ is 1. In this case, the image signal V _B1 which is the output signal of the AND circuit 26 is time t as shown in FIG.
_At time t ₁₂ , which is delayed from ₁₁ by a delay time Δt _i , L
Rising from the level to the H level, and at time t ₁₃ , L
It becomes a signal that falls to the level. Therefore, the image signal V _B1
There time T ₁ in the H level, the image signal V _B1 is shorter than the time T ₂ in the L level, its ratio gamma, gamma =
T ₁ / T ₂ = (T ₀ −Δt _i ) / (T ₀ + Δt _i ) <1
Becomes As a result, the lighting time of the LD1 becomes shorter than that in the case where the image signal V ₀ is applied, and the overlapping exposure portion decreases, so that the exposure amount decreases as a whole, and the exposure range is adjusted to an appropriate range X ₀ . be able to.

Similarly, FIGS. 5D and 6D show the waveform of the image signal V _B1 in the second embodiment.

Also in the second embodiment, the numerical value stored in the numerical value generator 21 is changed in accordance with the change of the information (screen ruling etc.) necessary for the image recording, so that an appropriate delay time Δt _i can be obtained. It is possible to select a delay circuit to have. Therefore, each time the value of the input signal V _IN given to the numerical value generator 21 is changed, the value of the ratio γ of the image signal V _B1 changes.

C. Third embodiment

FIG. 10 is a block diagram showing the LD drive section of the image recording apparatus as the third embodiment of the present invention.
In this embodiment, an m-bit random number generator is used to randomly change the lighting time of the LD.

The m-bit random number generator 27 generates an m-bit random number in synchronization with the clock signal V _CL output by the clock generator 19. The random number is temporarily stored in the latch 28 and then output from the latch 28 in synchronization with the clock signal V _CL, and the terminals S _{1 to} S _{m of the} selector 29 are also output.
Is input to the selector 29 and the random number value is detected by the selector 29. In accordance with this detection value, the selector 29 extracts the corresponding terminal among the n terminals I ₁ ~I _n. as a result,
Depending on the n delay circuits D ₁ to D _n-1 and I _n terminal and a random number value is randomly selected, delayed signal V _Di is variously changed according to the random number value the delay time Delta] t _i Signal. As a result, the image signal V _B2 which is the output signal of the OR circuit 23 becomes a signal as shown in FIG. 5C, for example.
Since the LD1 is driven by such an image signal V _B2 , the extension time of the lighting time of the LD1 changes randomly. In this embodiment, the relationship is n = 2 ^m .

In FIG. 10, the OR circuit 23 is used to delay at random, but instead of the OR circuit 23, AN is used.
A D circuit can also be used. In this case, for example, the delay time Δt of the signal as shown in FIG.
Will change variously depending on the random number value. That is,
The ratio γ described above changes variously while always satisfying the relationship of γ <1. This makes it possible to shorten the lighting time of the LD1 by various times as compared with the case of driving with the image signal V ₀ .

D. Fourth embodiment

FIG. 11 is a block diagram showing an LD drive section of an image recording apparatus as a fourth embodiment of the present invention. In the fourth embodiment, it is possible to randomly change the extension time of the lighting time of the LD according to the random number value generated by the m-bit random number generator 27 and also to shorten the lighting time of the LD at random. To do. Further, in the fourth embodiment, the range in which the lighting time of the LD is randomly changed is also controlled in accordance with the information necessary for the image recording described above.

The random number generator 27, the random number converter 30, and the latch 28 are connected to the clock generator 20. or,
The input unit 25 is connected to the random number converter 30, and the output end of the latch 28 is connected to the random number determination unit 31.
The random number judgment unit 31 outputs the judgment result to the selector 32 and also to the AND / OR circuit 33.

First, the random number generator 27 outputs the clock signal V _CL.
When an m-bit random number signal V _R is output to the random number converter 30 in synchronization with, the random number converter 30 changes the input random number signal V _R (whose value is described as x) to a random number signal V of a different value.
Convert to ₁ (denoted as y). Although various kinds of conversion can be applied, a case of linear conversion will be described here as an example (note that non-linear conversion is also possible). That is, the random number converter 30 determines the random value x
Is converted to a random value y according to the formula of y = ax + b. Here, both the coefficient a and the intercept b are given by the input unit 25 (input signal V _IN1 ). Random signal V after conversion
₁ (m-bit signal) is sent to the random number determination unit 31 via the latch 28.

The random number judging section 31 judges the sign of the random number value y indicated by the transmitted random number signal V ₁ and outputs the signal V ₃ (+/− signal) indicating the sign to the AND / OR circuit 33. To do. In addition, the random number determination unit 31 determines the absolute value | y | of the random number value y.
Then, the absolute value | y | is output to the selector 32 as the signal V ₂ .

[0066] The selector 32, in response to the signal V _2, the absolute value | y | of the pins corresponding with extracts from n terminals I ₁ ~I _n in (correspondence is set in advance), is selected delay circuits _{D i (i; 1~n-1} ) signal to delayed by the image signal V when the terminal I _n is selected
₀ itself is used as the image signal V _di and the AND / OR circuit 3
Output to 3.

On the other hand, the AND / OR circuit 33 outputs the signal V ₃
AND circuit and OR which it has inside in synchronization with
Separate from the circuit. That is, when the signal V ₃ indicates +, the AND / OR circuit 33 selects the OR circuit, _obtains the logical sum of the image signals V ₀ and V _Di , and then determines the logical sum signal as the image signal V Output as _B3 . On the contrary, the signal V ₃ is −
, The AND / OR circuit 33 selects the AND circuit, calculates the logical product of the image signals V ₀ and V _Di , and outputs the logical product signal as the image signal V _B3 . Therefore, when the random number value y is a positive value, the lighting time of the LD1 is randomly extended, while when the random number value y is a negative value, L
The lighting time of D1 is shortened at random. Accordingly, depending on the value of the random number value y, the lighting time of the LD1 can be always extended at random, and conversely, the lighting time of the LD1 can be shortened at random at the same time, while the lighting time of the LD1 is extended. It is possible to mix shortening at random and change it. Specifically, it is as follows.

For example, this is the case as shown in FIGS. In this case, for simplicity of explanation,
The coefficient values a are all set to a constant value a ₁ (a ₁ > 0).

First, in the case of FIG.
From the above, the coefficient value a ₁ and the intercept b ₁ are given to the random number converter 30. Here, the intercept b ₁ is b ₁ > 0. As a result, the converted random number value y is b ₁ ≦ y ≦ y ₁ and is always a positive value. Here, the symbol y ₁ means a ₁ · 2 ^m + b ₁
Shows the value given by. As a result, the lighting time of the LD1 changes randomly in the always extending direction, and even when the exposure is performed in the out-of-focus state, it can be variously changed in the form of increasing each dot area ratio. It is possible to alleviate unevenness in light and shade.

The case of FIG. 12B is also the same as that of FIG. However, in this case, the value of the intercept b is changed to 0 value by the instruction of the input unit 25.

In the case of FIG. 7C, the intercept b is set to a negative value, that is, -b ₂ (b ₂ > 0). Moreover, in this case, the random value y can take positive and negative values. As a result, in this case, the image signal V _B3
Becomes a signal as shown in, for example, FIG.
A case where the lighting time of is randomly extended and a case where the lighting time is shortened are randomly mixed. As a result, even if the light amount of the light beam varies during exposure, it is possible to overcome the effect of the out-of-focus state and prevent the occurrence of uneven density.

On the contrary, the case of FIG. 12D is a case where the value of the random number y is always a negative value (b ₃ > 0). Therefore, the lighting time of the LD1 is always shortened randomly. This case is suitable when the light quantity of the LD 1 is always too large.

As described above, in this embodiment, by changing the values of the intercept b and the inclination a according to the information (screen ruling etc.) necessary for the above-mentioned image recording, the ratio γ can be set within various ranges. In addition, it is possible to change randomly within the range.

In the fourth embodiment, if the value of the inclination a is set to 0, the above-mentioned first and second embodiments can be realized. In this case, the value of the intercept b may be changed according to the information required for image recording.

Further, FIGS. 12A and 12B both correspond to the above-mentioned third embodiment, and similarly (d) also corresponds to the case where the AND circuit described in the third embodiment is used. ing.

[0076]

According to the invention of claims 1 to 4, the light emission time of the light emitting means can be controlled by changing the ratio, and an accurate halftone dot area can be secured. Occurrence can be prevented.

In addition, according to the second and fourth aspects of the invention, the halftone dot area is controlled according to the information necessary for image recording such as the number of screen lines, the recording line density, the manifest characteristic and the characteristic of the light emitting means. Therefore, it is possible to accurately prevent the occurrence of unevenness in light and shade according to each information.

In the inventions of claims 3 and 4, it is possible to randomly control the light emitting time of the light emitting means by randomly changing the ratio, and it is possible to randomly change the halftone dot area. Becomes Therefore, it is possible to randomly form a blackened portion and a non-blackened portion of the contact points between the adjacent halftone dots, and it is possible to prevent uneven shading in a macroscopic view.

[Brief description of drawings]

FIG. 1 is a perspective view showing an optical and mechanical configuration of an image recording apparatus.

FIG. 2 is a block diagram showing a configuration of an LD drive unit of the first embodiment.

FIG. 3 is a timing chart showing a relationship between image signals.

FIG. 4 is an explanatory diagram showing the principle of the present invention.

FIG. 5 is a timing chart showing a relationship between a clock signal and each image signal.

FIG. 6 is a timing chart showing the relationship between a clock signal and each image signal.

FIG. 7 is a perspective view showing a configuration for detecting a light amount of a light beam.

FIG. 8 is a block diagram showing a configuration of an LD drive unit according to a second embodiment.

FIG. 9 is a timing chart showing the relationship between image signals.

FIG. 10 is a block diagram showing a configuration of an LD drive unit according to a third embodiment.

FIG. 11 is a block diagram showing a configuration of an LD drive unit according to a fourth embodiment.

FIG. 12 is an explanatory diagram showing various cases of conversion of random number values.

FIG. 13 is an explanatory diagram showing the relationship between the light amount and the density of the lith film.

FIG. 14 is an explanatory diagram pointing out a problem of the conventional technique.

FIG. 15 is an explanatory diagram showing an exposure amount per unit area on a film.

FIG. 16 is an explanatory diagram pointing out a problem of the conventional technique.

FIG. 17 is an explanatory diagram that points out the problems of the conventional technology.

[Explanation of symbols] 1 LD 2 Polygon mirror 3 f / θ lens 4 Film 18 Dot generator 19 Clock generator 21 Numerical value generator 22, 29, 32 Selector 23 OR circuit 25 Input section 26 AND circuit 27 Random number generator 30 Random number conversion Unit 31 Random number determination unit 33 AND / OR circuit

Claims (4)

[Claims] 1. A storage unit for storing and outputting a first image signal representing an image to be recorded, and (b) being connected to the storage unit, the first image signal being at the first level. Second image signal generation means for outputting as a second image signal after changing the ratio of the first time and the second time after changing from the first level to the second level and returning to the first level again. (C) a light emitting means connected to the second image signal generating means and emitting a light beam when the second image signal is at the first level; and (d) scanning the light beam onto a photosensitive material. And a scanning unit for recording the image on the photosensitive material. 2. (e) An input signal generating means for outputting an input signal giving information necessary for the image recording to the second image signal generating means, further comprising: The image recording apparatus according to claim 1, which is a unit that changes the ratio according to the information to be instructed. 3. (f) a clock signal generation means for outputting a clock signal for giving the output timing of the first image signal to the storage means, and (g) a random number connected to the clock signal generation means and instructing a random number. A random number generating means for outputting a signal to the second image signal generating means according to the clock signal, wherein the second image signal generating means is means for randomly changing the ratio according to the random number signal. The image recording device according to claim 1. 4. (h) It further comprises an input signal generating means for outputting an input signal giving information necessary for the image recording to the random number generating means, and the random number generating means has the random number within a range according to the information. The image recording apparatus according to claim 3, which is means for outputting a signal.