JP2000289303A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To render the measurement of black formation pixel numbers simple and inexpensive by measuring black formation pixel numbers by the sample of a random sampling data from an image data. SOLUTION: The image reading part 2 of a digital copying machine 1 operates to image form and photoelectric transfer the reflection image of illumination of line light sources 6 to a CCD sensor 13 via reflection mirrors 7, 9, 10 regarding a manuscript placed on a contact glass 5; then outputting the image data of a dot matrix to a signal processing part 3. In the processing part 3, the image data is amplified by an amplifier 14 to subsequently be converted from an analogue value to a digital value, and also inputted in a printing control part 17 as a binary image data at an image processing part 16. A random sampling timing generation circuit of the control part 17 generates the timing signal of random small number pixel sampling from the image data of a trim circuit of the control part 17 for the purpose of sampling every picture data at a pixel number counter circuit, thus estimating an average value of the image data of a population. In this manner, the measurement of black formation pixel numbers can be done simply at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image in pixel units, such as a laser printer, a digital copying machine, a facsimile machine, and the like.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus such as a laser printer, a digital copying machine, a facsimile machine, etc., uses a photoconductor by a deflecting means comprising a polygon mirror to deflect a laser beam from a recording light source comprising a laser diode modulated by image data. There is used an image forming apparatus equipped with a device that scans in the main scanning direction and moves the photoconductor in the sub-scanning direction to write an image on the photoconductor one line at a time. In such an image forming apparatus, there is an image forming apparatus that counts image data for each pixel and controls a toner supply amount based on the count data.

Japanese Patent Application Laid-Open No. 5-88554 discloses an image forming apparatus having a developing means for visualizing a latent image formed in pixel units by using a developer, a counting means for counting the number of pixels of the latent image, Detecting means for detecting the concentration of the developer in the developing means, inferring means for inferring the supply amount of the developer from the deviation and the rate of change of the output of the detecting means from a reference value, and replenishment based on the inferring means. And a replenishing unit for replenishing the developing unit with an amount of the developer every time the counting unit counts a predetermined number of pixels.

[0004]

In the above image forming apparatus, when forming an image of 600 dpi on A3 paper,
The number of dots per sheet is about 34.8 million dots,
To count the number of black pixels printed on one A3 sheet,
A counter capable of counting the total number of pixels is required. To realize this with a binary counter, a 26-bit counter is required, which complicates the configuration and increases the cost. The counter is synchronized with the image data for counting the number of pixels. Need to be.

If each pixel is weighted with 16 levels of density, a 4-bit adder and its carry are counted.
A 25-bit counter synchronized with the image data is required, which complicates the configuration and increases the cost. In a system in which the control unit does not have a clock synchronized with the image data and a modulation signal for driving the laser is directly input from an external controller, the number of pixels cannot be counted by the counter.

The input parameters for controlling the toner replenishment amount include not only the above-mentioned count value but also a photosensor for detecting the amount of toner adhered to the photoconductor, a toner density sensor for detecting the toner density of the developer, and a photoconductor. The toner supply amount is calculated and controlled using data from a potential sensor or the like that detects the surface potential of the toner, but the toner supply amount obtained by this calculation does not require much accuracy. Does not require much accuracy.

It is an object of the present invention to provide an image forming apparatus which can realize a counting means for counting the number of black forming pixels with a simple and low-cost configuration. It is another object of the present invention to provide an image forming apparatus capable of realizing a cumulative addition means for cumulatively adding image data having a plurality of bits of density information to each pixel with a simple and low-cost configuration.

According to a third aspect of the present invention, there is provided a counting means for counting the lighting time of the light source means when the control section does not have a clock synchronized with the image data and a modulation signal for driving the light source means is directly input from outside. It is an object of the present invention to provide an image forming apparatus which can realize the above with a simple and low-cost configuration. A fourth object of the present invention is to provide an image forming apparatus capable of realizing a counting means for counting the number of black forming pixels with a simple and low-cost configuration.

It is another object of the present invention to provide an image forming apparatus capable of realizing a simple and low-cost accumulating means for accumulating and adding image data in which each pixel has a density weight. According to a sixth aspect of the present invention, the counting means for counting the lighting time of the light source means when the control section does not have a clock synchronized with the image data and a modulation signal for directly driving the light source means is inputted from the outside is simplified. An object of the present invention is to provide an image forming apparatus that can be realized with a low-cost configuration.

A seventh object of the present invention is to provide an image forming apparatus capable of realizing the fourth to sixth aspects of the present invention with a simpler and lower-cost configuration. It is an object of the present invention to provide an image forming apparatus in which the means for generating a sampling clock in the invention according to the fourth or fifth aspect can be realized with a simple and low-cost configuration. A ninth aspect of the present invention is to provide an image forming apparatus capable of obtaining more accurate statistical values in the fourth to sixth aspects.

[0011]

According to a first aspect of the present invention, there is provided an image forming apparatus for forming an image based on image data by using a sample of image data randomly extracted from the image data. It has a counting means for counting the number of black forming pixels.

According to a second aspect of the present invention, there is provided an image forming apparatus for forming an image using image data having a plurality of bits of density information in each pixel, wherein the image data is sampled by using a sample of image data randomly extracted from the image data. Is provided.

According to a third aspect of the present invention, there is provided a light source means for generating a light beam, a deflecting means for deflecting and scanning the light beam from the light source means, and scanning and exposing the surface to be scanned by the light beam from the deflecting means. An image forming apparatus that forms an image by forming a latent image on the surface to be scanned by on-off modulating the light beam with a modulation signal generated from image data,
Means for sampling the on / off state of the modulation signal at random time instants, and estimating the cumulative on time of the light beam based on the ratio of the number of times of sampling to the number of times of on / off. It is.

According to a fourth aspect of the present invention, there is provided an image forming apparatus for forming an image based on image data input in synchronization with an image clock, wherein the image data is sampled by a sampling clock having a cycle different from the image clock. A counting means for counting the number of black forming pixels from the sampled image data is provided.

According to a fifth aspect of the present invention, there is provided an image forming apparatus for forming an image based on a plurality of bits of image data input in synchronization with an image clock, wherein the image data is generated by a sampling clock having a period different from the image clock. It is provided with a cumulative addition means for capturing and cumulatively adding the captured image data.

According to a sixth aspect of the present invention, there is provided a light source means for generating a light beam, a deflecting means for deflecting and scanning the light beam from the light source means, and scanning and exposing the surface to be scanned by the light beam from the deflecting means. An image forming apparatus that forms an image by forming a latent image on the surface to be scanned by on-off modulating the light beam with a modulation signal generated from image data,
Counting means for sampling whether the luminous flux is on or off with an asynchronous sampling clock from the modulation signal, and counting the number of times of the sampled on or off; and the number of ons counted by the counting means Alternatively, there is provided a means for estimating the cumulative ON time of the light beam based on the ratio of the number of times of OFF to the number of times of sampling.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the fourth to sixth aspects, the cycle of the sampling clock is a cycle that is slower than the cycle of the pixel clock.

The invention according to claim 8 is the image forming apparatus according to claim 4 or 5, further comprising clock counting means for counting a pixel clock, wherein the clock counting means generates a signal each time a predetermined value is counted. Is the sampling clock.

According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the fourth to sixth aspects, the sampling clock has no periodicity with respect to a frequency of the image data.

[0020]

FIG. 2 shows an embodiment of the present invention. The first embodiment is an embodiment of the invention according to claim 1, and is an image forming apparatus including a digital copying machine 1 using a semiconductor laser as a light source. The digital copier 1 reads an image of a document (not shown), inputs the image, and outputs the image data as image data. The digital copier 1 performs signal processing for performing various processes on the image data input by the image reading unit 2. The unit 3 and an image printing unit 4 that prints image data output from the signal processing unit 3 on a recording material such as plain paper or an OHP sheet and outputs the image data are sequentially connected. .

More specifically, in the digital copying machine 1, the image reading unit 2 includes a first light source 6 and a reflecting mirror 7 which are elongated in the main scanning direction below a document table 5 made of contact glass. A scanning unit 8, a second scanning unit 11 including a pair of reflection mirrors 9, 10, an imaging optical system 12, and a CCD (Charge Coupled).
The first scanning unit 8 and the second scanning unit 11 are supported movably in the sub-scanning direction such that the speed ratio is 2: 1.

The signal processing unit 3 is provided with a C
An amplifier 14 connected to a CD sensor 13 and an A / DC
(Analog Digital Converte
r: analog / digital converter) 15, an image processing unit 16 for performing various processes on image data, and an image for modulating a semiconductor laser that emits a laser beam with raster image data from the image processing unit 16. A print control unit 17 as an image formation control unit for converting the data into data, and an LD (Laser Di) as a light source modulation unit for driving and controlling the image printing unit 4 based on the image data from the print control unit 17.
(mode: semiconductor laser) Modulating section 18 and the like are sequentially connected.

Further, the image printing unit 4 includes an LD modulation unit 18
A light source means 19 comprising a LD unit incorporating a semiconductor laser as a recording light source for generating a light beam modulated in accordance with the modulation data, a cylinder lens 20, an LD
A polygon mirror 21 as deflection means for deflecting and scanning the laser beam generated by the unit 19; a motor (not shown) for rotating the polygon mirror 21 at a constant rotation speed; Lens 23 for condensing an image on the photoreceptor 22 at a predetermined interval in the sub-scanning direction to form an image and scanning at a constant speed; and fθ lens 23 disposed at a position in front of the effective writing area in the main scanning direction. Beam detecting means 2 including a photodetector as a synchronous detector that generates a synchronous detection pulse signal XDETP when receiving a laser beam from the lens 23.
And 4. The synchronization detection pulse signal XDETP from the light detector 24 is fed back to the print control unit 17 of the signal processing unit 3.

In the image printing section 4, the laser beam generated from the LD unit 19 passes through the cylinder lens 20, enters the polygon mirror 21 rotating at a predetermined rotation speed, and is deflected and scanned there. After that, fθ
The light is condensed on the photoconductor 22 and the photodetector 24 via the lens 23. As the photoconductor 22, for example, a photoconductor drum is used, but a photoconductor belt or the like may be used.

In the digital copying machine 1 having such a configuration, the image reading unit 2 reads and inputs image data from a document, and the image printing unit 4 prints the data on printing paper and outputs the data. The image data is temporarily stored in the signal processing unit 3, and the input speed of the image reading unit 2 and the output speed of the image printing unit 4 are arbitrated.

More specifically, in the digital copying machine 1, the image reading section 2 illuminates the original placed on the contact glass 5 with the line light source 6 and reflects the reflected light images on the reflection mirrors 7, 9, and 10. An image is formed on the CCD sensor 13 by the imaging optical system 12 via the CCD, and the photoelectric conversion is performed by the CCD sensor 13, and the first scanning unit 8 and the second scanning unit 11 are scanned in the sub-scanning direction. The image data of the dot matrix is output to the signal processing unit 3 line by line as main scanning lines that are continuous in the scanning direction.

At this time, the CCD sensor 13 outputs one line of image data one pixel at a time in a main scanning direction at a predetermined pixel clock after resetting the address by the line synchronization signal LSYNC.
Are sequentially output line by line to the signal processing unit 3 at a predetermined line cycle caused by the scanning speed of the first scanning unit 8 and the second scanning unit 11, the reading cycle of the CCD sensor 13, and the like.

Therefore, in the signal processing unit 3, the image data sequentially input line by line from the CCD sensor 13 is amplified by the amplifier 14 and converted from an analog value to a digital value by the A / DC 15; After executing various processes such as a brightness correction process and a scaling process, the print control unit 17 stores it as binary (black and white) image data (or image data pulse-width modulated one pixel at a time in accordance with the image density). Enter in the means. Then, the print control unit 17 reads out the image data from the storage unit in accordance with the print output speed. The print control unit 17 performs various processes such as range restriction and γ conversion on the image data, and then outputs the image data to the LD modulation unit 18. The LD modulator 18 is a print controller 17
The driving current modulated in accordance with the image data from the image printing unit 4 is output to the LD unit 19 of the image printing unit 4.

In the image printing section 4, the LD unit 19
The semiconductor laser is driven in accordance with the image data by the drive current from the D modulation section 18, and the semiconductor laser emits a laser beam modulated in accordance with the image data.
This laser beam is converged by the cylinder lens 20, is deflected and scanned by the polygon mirror 21, is corrected by the fθ lens 23, and forms an image on the surface of the photosensitive drum 22 that moves in the sub-scanning direction.

The surface to be scanned of the photosensitive drum 22 is uniformly charged by the charging means and then exposed to a laser beam from the fθ lens 23 to form an electrostatic latent image of a dot matrix. The toner image is developed by the developing device to form a toner image, and the toner image is transferred to the printing paper by the transfer unit and is fixed to the printing paper by the fixing unit, thereby performing image printing.

Here, in the image printing section 4, when the laser beam scanned by the polygon mirror 21 is incident on the synchronization detector 24 immediately before the effective writing area of the photosensitive drum 22, the synchronization detector 24 outputs a synchronization detection pulse signal. XDETP is output, and the print control unit 17 of the signal processing unit 3
The timing is controlled by the synchronization detection pulse signal XDETP from the controller. Thus, the print control unit 17 outputs the image data to the print output of the image printing unit 4 at an appropriate timing. Control of these series of operations is performed by a CPU as control means (not shown).

FIG. 1 shows a part of the print control unit 17. In the print control unit 17, image data is written from the image processing unit 16 to the buffer memory 31. The image data written in the buffer memory 31 is read out from the buffer memory 31 by the buffer memory read control circuit 32 in synchronization with the synchronization detection pulse signal XDETP from the synchronization detector 24 and the print clock in accordance with the print output speed. .

The range of the image data read from the buffer memory 31 is limited by the trimming circuit 33 so that an image is not formed outside the range of the printing paper.
Further, in the case of multi-valued image data, after various processing such as γ conversion for converting the image data so that the print density and the image data are linear are executed by the processing circuit 34, the forced lighting circuit 35 outputs A logical sum is obtained with a forced lighting signal for forcibly lighting the semiconductor laser so that the laser light is incident on the laser beam 24, and is output to the LD modulator 18.

Here, the forced lighting timing generation circuit 36
Generates a timing signal for forcibly turning on the semiconductor laser so that laser light is incident on the synchronization detector 24 in synchronization with the synchronization detection pulse signal XDETP from the synchronization detector 24, and the forcible lighting circuit 35 is forcibly turned on. A forced lighting signal is generated based on the timing signal from the timing generation circuit 36, and the forced lighting signal is ORed with image data from the processing circuit 34 and output to the LD modulator 18.

In the case of this embodiment, the image data output from the trimming circuit 33 is taken into the pixel count circuit 37 from the flow of the image data.

Conventionally, the pixel number counting circuit counts or integrates all the pixels to be printed, and requires hardware such as a dedicated large counter as described above because of the large number of pixels and the high pixel rate. Met.

Meanwhile, in statistics, there is a technique called section estimation (reference: statistical analysis that can be easily understood, book:
(Sadao Ishimura, published by Tokyo Book Co., Ltd.). This is to estimate population information from randomly extracted data. For example, the number of dots per sheet of A3 size paper is about 34.8 million dots, and when 500 pixels are black out of data of 1000 pixels randomly extracted from the data, a 95% confidence coefficient is obtained. It can be said that 47% to 53% of the pixels are black. It can be said that the accuracy of this value is sufficient for calculating the toner consumption.

For example, a general linear velocity of an image forming apparatus that performs 40 A4 size copies per minute is 200 mm /
s, and A3 size paper 1
The time required for image formation per sheet is about 2 seconds. In this time, one out of the image data for one A3 size sheet
In the process of extracting image data of 000 pixels, it takes 2 ms per pixel. This number is a speed sufficient for software processing by the CPU, and does not require special hardware for counting and integrating the number of pixels, and can be realized at low cost. Even if the function of counting and integrating the number of pixels is realized by hardware,
Since it can be made with an it counter, it can be realized with smaller hardware than a 26-bit counter required to count all pixels printed on one A3 sheet.

In the first embodiment, the random extraction timing generation circuit 38 outputs image data (image data to be printed on one print sheet) output from the trim circuit 33.
A timing signal for extracting image data more randomly is generated. For example, a timing signal for randomly extracting image data of 1000 pixels from image data printed on one A3 size sheet is generated. .

The pixel count circuit 37 includes a trim circuit 3
3 is sampled by the timing signal from the random extraction timing generation circuit 38 (the image data from the trimming circuit 33 is sampled at the timing when the timing signal is input from the random extraction timing generation circuit 38). ), The number of black print pixels is counted based on the sample, and the count value is output to the CPU. The CPU
The number of black print pixels per print sheet is estimated from the count value (count value per print sheet) of the pixel count circuit 37 by the above-described statistical method, and the toner supply amount is determined based on the estimated value. To determine. The developing unit is supplied with toner from a toner replenishing unit, and the toner replenishing unit is controlled by the CPU and replenishes the developing unit with toner by the amount of toner replenishment determined by the CPU.

According to the first embodiment, in an image forming apparatus for forming an image based on image data, a counting means for counting the number of black forming pixels from a sample of image data randomly extracted from the image data. The provision of the pixel number counting circuit 37 and the random extraction timing generation circuit 38 makes it possible to realize a counting means for counting the number of black forming pixels with a simple and low-cost configuration. The number can be estimated.

The second embodiment of the present invention is an embodiment of the second aspect of the present invention. In the second embodiment, in the first embodiment, the signal processing unit 3 includes
Image data sequentially input line by line from the CD sensor 13 is amplified by an amplifier 14, converted from an analog value to a digital value by an A / DC 15, and various processes such as a brightness correction process and a scaling process are performed by an image processing unit 16. And then input it to the storage unit of the print control unit 17 as 8-bit image data having density information (image data having a plurality of bits of density information for each pixel).

Here, the method of section estimation in statistics can obtain, with a certain degree of reliability, the average value of the density of a plurality of bits of image data in which each pixel is weighted with the density. In other words, it is possible to obtain the average value of the population with a certain degree of reliability from the average value obtained from the value obtained by accumulating the data of a small number of pixels randomly extracted from the image data of a plurality of bits in which the weight of each pixel is weighted. it can.

Therefore, the random extraction timing generation circuit 3
Numeral 8 generates a timing signal for randomly extracting data of a small number of pixels from the image data (image data printed on one printing sheet) output from the trimming circuit 33. It is assumed that a timing signal for randomly extracting data of 1000 pixels from image data to be printed on paper is generated.

The pixel number counting circuit 37 samples the image data output from the trimming circuit 33 for each pixel in accordance with the timing signal from the random extraction timing generating circuit 38 (image data from the trimming circuit 33). Is sampled for each data of a small number of pixels at the timing when the timing signal is input from the random extraction timing generation circuit 38), and the image data is cumulatively added for each pixel by the sample, thereby obtaining the density value of each pixel. And outputs the accumulated value to the CPU. C
PU is the cumulative addition value (1) from the pixel count circuit 37.
The average value of the count value (count value of each pixel) from the pixel count circuit 37 is obtained from the count value of each pixel per print sheet) by the above-described statistical method, thereby obtaining the total value per print sheet. It is assumed that the average value of the number of print pixels (the average value of the image data from the trim circuit 33) is estimated, and the toner supply amount is determined based on the estimated value. The developing unit is supplied with toner from a toner supply unit.
Controlled by the PU, the developing unit is replenished with toner by the toner replenishing amount determined by the CPU.

According to the second embodiment, in an image forming apparatus for forming an image from image data having a plurality of bits of density information in each pixel, a sample of image data randomly extracted from the image data is used. Since a pixel count circuit 37 and a random extraction timing generation circuit 38 are provided as a cumulative addition means for cumulatively adding image data, a cumulative addition means for cumulatively adding image data having a plurality of bits of density information to each pixel is provided. This can be realized with a simple and low-cost configuration, and the average value of the image data of the population can be estimated with a simple and low-cost configuration.

The third embodiment of the present invention is an embodiment of the third aspect of the present invention. In the third embodiment, in the first embodiment, as shown in FIG.
The external controller 39 receives the print clock and the synchronization detection pulse signal XDETP from the synchronization detector 24, and
A modulation signal for driving the semiconductor laser of the LD unit 19 is output at a predetermined timing. Note that the print clock may be generated inside the controller 39.

The modulation signal from the controller 39 is LD
A signal for controlling the on / off of the semiconductor laser of the unit 19, which may be a binary signal that switches between high (high level) and low (low level) depending on whether it is on or off one pixel at a time, or image density one pixel at a time. May be a signal that has been pulse width modulated according to The modulated signal output from the controller 39 is applied to the forced lighting circuit 3 in order to irradiate a laser beam to the synchronization detector 24 in the print control unit 17 to obtain a synchronization detection signal.
5, the logical sum of the signal and the forced lighting signal for forcibly lighting the semiconductor laser of the LD unit 19 is calculated, and the LD modulator 18 is turned on.
Output to

The modulation signal output from the controller 39 is also taken into the pixel count circuit 40. The random extraction timing generation circuit 41 generates a timing signal for randomly extracting image data from the image data (image data printed on one sheet of printing paper) output from the controller 39. For example, one A3 A timing signal for randomly extracting image data of 1000 pixels from image data to be printed on paper of a size is generated.

The pixel count circuit 40 samples the on / off state of the modulation signal from the controller 39 based on the timing signal from the random extraction timing generation circuit 38, and counts the number of on / off times. The count value is output to the CPU. The CPU calculates the count value of the pixel count circuit 40 (the count value per print sheet).
From the ratio of the number of times of sampling per print sheet to the number of times of on (or off), the cumulative on-time of the laser beam is estimated by the above-mentioned statistical method, and toner replenishment is performed based on the estimated value. Determine the amount. The developing unit is supplied with toner from a toner replenishing unit, and the toner replenishing unit is controlled by the CPU and replenishes the developing unit with toner by the amount of toner replenishment determined by the CPU.

In the third embodiment, an LD unit 19 as a light source for generating a light beam, a polygon mirror 21 as a deflecting device for deflecting and scanning the light from the light source, and a light beam from the deflecting device are used. An image forming apparatus that scans and exposes a surface to be scanned, and forms an image by forming a latent image on the surface to be scanned by modulating and turning off the light beam by a modulation signal generated from image data.
The number of pixels as means for sampling the on / off state of the modulation signal at random time instants and estimating the cumulative on-time of the light beam based on the ratio of the number of times of sampling to the number of on / off times Count circuit 40,
Since the control unit includes the random extraction timing generation circuit 41 and the CPU, there is no clock synchronized with the image data.
The counting means for counting the lighting time of the light source means when a modulation signal for directly driving the light source means is inputted from the outside can be realized with a simple and low-cost configuration, and the lighting time of the light source means with a simple and low-cost configuration Can be inferred.

FIG. 4 shows a part of a print control unit according to another embodiment of the present invention. This fourth embodiment is one embodiment of the invention according to claim 4. In the fourth embodiment, in the first embodiment, the print control unit 17 writes multi-valued image data having density information or binary image data without density information from the image processing unit 16 into the buffer memory 31. It is. This buffer memory 31
Is read from the buffer memory 31 by the buffer memory read control circuit 32 in synchronization with the synchronous detection pulse signal XDETP from the synchronous detector 24 and the print clock in accordance with the print output speed.

The range of the image data read from the buffer memory 31 is limited by the trimming circuit 33 so that an image is not formed outside the range of the printing paper.
Further, in the case of multi-valued image data, after various processing such as γ conversion for converting the image data so that the print density and the image data are linear are executed by the processing circuit 34, the forced lighting circuit 35 outputs A logical sum is obtained with a forced lighting signal for forcibly lighting the semiconductor laser so that the laser light is incident on the laser beam 24, and is output to the LD modulator 18.

In the case of this embodiment, the image data output from the trimming circuit 33 is taken into the pixel count circuit 37 from the flow of the image. The pixel number counting circuit 37 samples the image data from the trimming circuit 33 for each sampling clock generated by the sampling clock generating circuit 42 and black pixels (black forming pixels).
And outputs the counted value to the CPU.

The CPU estimates the number of black pixels in the population (the number of black pixels per print sheet) from the count value of the pixel count circuit 37 by a statistical method, and based on the estimated value, the toner supply amount. To determine. The developing unit is supplied with toner from a toner replenishing unit, and the toner replenishing unit is controlled by the CPU and replenishes the developing unit with toner by the amount of toner replenishment determined by the CPU.

Conventionally, the sampling clock is a printing clock, and the image count circuit counts or integrates all the pixels to be printed. Therefore, hardware such as a dedicated large counter circuit is required as described above because of the large number of pixels and the high pixel rate.

In statistics, as described above, there is a technique called section estimation, which is to estimate population information from randomly extracted data. For example, the number of dots per sheet of A3 size paper is about 34.8 million dots, and when 500 pixels are black out of data of 1000 pixels randomly extracted from the data, a 95% confidence coefficient is obtained. It can be said that 47% to 53% of the pixels are black. The same applies to the case of cumulatively adding a plurality of bits of image data in which each pixel has a density weight, and the average of the population is calculated by the average value obtained from the value obtained by cumulatively adding the data of a small number of pixels extracted at random. The value can be determined with a certain degree of reliability. That is, it is possible to estimate the number of all pixels by counting a small number of randomly extracted pixels without counting all the pixels to be printed.
This method is particularly effective because the accuracy required for counting the number of pixels performed to calculate the toner consumption is not strict.

For example, a general linear velocity of an image forming apparatus for performing A4 size copying of 40 sheets per minute is 200 mm.
/ S, and the time required to form an image per A3 size sheet with this image forming apparatus is about 2 seconds. 100 pieces of image data for one sheet of A3 size paper
In order to extract the image data of 0 pixel, the image data may be sampled at a sampling clock every 2 ms. This sampling clock may be generated by a general-purpose timer, or a counter that generates a pulse once per 3480 pixel clocks is prepared in order to extract, for example, 1000 pixels from a pixel of 34.8 million dots. The output may be used as a sampling clock. Alternatively, a circuit can be realized relatively easily, for example, 32768 (1 of 2), regardless of the number of 1000 pixels.
The image data may be sampled 1062 times using a frequency divider that generates a pulse once per (5th) pixel clock.

The above-mentioned time of 2 ms is a speed sufficient for software processing by the CPU, and it is not necessary to provide special hardware for counting and integrating the number of pixels, and it can be realized at low cost. Alternatively, even if the function of counting and integrating the number of pixels is realized by hardware, a 10-bit counter can be used in time, so 26 bits required to count all the pixels printed on one A3 sheet.
Can be realized with smaller hardware than the counters of the above.

FIG. 5 shows a pixel count circuit 37 and a sampling clock generation circuit 42 according to the fourth embodiment.
Is shown. The sampling clock generation circuit 42 receives the print clock, and divides the frequency of the print clock by 1/2.
Times to increase the print clock to 32768 (2 to the 15th power)
A frequency dividing circuit that divides the frequency and uses it as a sampling clock outputs the sampling clock to the pixel count circuit 37.

The pixel count circuit 37 is provided with the trim circuit 3
For example, binary image data is input from 3 and the image data from the trim circuit 33 when the sampling clock from the sampling clock generating circuit 42 transitions from low (low level) to high (high level) is black image data. Is a counter whose count value is incremented when. The counter 37 is cleared at the beginning of printing one image, and the count value is read by the CPU every time printing of one image is completed. The CPU can calculate the ratio of black pixels of one image from the count value.

According to the fourth embodiment, in an image forming apparatus for forming an image by image data input in synchronization with an image clock, the image data is sampled by a sampling clock having a cycle different from the image clock. Since the pixel number counting circuit 37 is provided as counting means for counting the number of black forming pixels from the sampled image data, the counting means for counting the number of black forming pixels can be realized with a simple and low-cost configuration.

FIG. 6 shows a pixel count circuit and a sampling clock generation circuit according to a fifth embodiment of the present invention. This fifth embodiment is one embodiment of the invention according to claim 5. In the fifth embodiment, an adder 40 is used in place of the pixel count circuit 37 in the fourth embodiment, and the adder 40 includes a trim circuit 33.
Input multi-valued image data.

The adder 40 accumulates and adds the image data from the trimming circuit 33 when the sampling clock from the sampling clock generating circuit 42 changes from low to high. The adder 40 is cleared at the beginning of printing of one image, and the accumulated addition value is set to CP each time printing of one image is completed.
Read by U.

The CPU obtains the average value of the density of one image from the cumulative addition value from the adder 40 by the above-mentioned statistical method, thereby obtaining the average value (trim value) of the total number of print pixels per print sheet. The average value of the image data from the circuit 33 is estimated, and the toner supply amount is determined based on the estimated value. The developing unit is supplied with toner from a toner replenishing unit, and the toner replenishing unit is controlled by the CPU and replenishes the developing unit with toner by the amount of toner replenishment determined by the CPU.

According to the fifth embodiment, in an image forming apparatus for forming an image based on a plurality of bits of image data input in synchronization with an image clock, the image forming apparatus uses a sampling clock having a cycle different from that of the image clock. Since the adder 40 is provided as a cumulative addition means for fetching data and cumulatively adding the fetched image data, a simple and low-cost configuration of the cumulative addition means for cumulatively adding image data having a density weight to each pixel is provided. Can be realized.

In the fourth and fifth embodiments, if the ratio of black pixels of an image is obtained with higher accuracy,
If the cycle of the sampling clock is shortened and the number of times of sampling is increased, a more accurate ratio can be obtained.

The sampling is performed simply at regular intervals regardless of the effective scanning period and the invalid scanning period of printing. In the case of an image forming apparatus in which the effective scanning period is 70%, even if all the pixels count black pixels, the black pixel ratio becomes 70%.
This is because black pixels are not counted even when image data is sampled during the period of 30%, which is an invalid scanning period. In this case, the black pixel ratio of the image obtained by counting the black pixels is counted with 70% as a parameter.

The fourth embodiment and the fifth embodiment are embodiments of the invention according to claim 7, and the cycle of the sampling clock is slower than the cycle of the pixel clock. 5 can be realized with a simpler and lower cost configuration.

The fourth and fifth embodiments are embodiments of the invention according to claim 8, and include a frequency dividing circuit 42 as clock counting means for counting a pixel clock (print clock). The clock counting means 42
Since the signal generated each time a predetermined value is counted is used as the sampling clock, the means for generating the sampling clock in the invention according to claim 4 or 5 can be realized with a simple and low-cost configuration.

FIG. 7 shows a part of the sixth embodiment of the present invention. The sixth embodiment is an embodiment of the invention according to claim 6. In the sixth embodiment, in the fourth and fifth embodiments, the external controller 39 receives the print clock and the synchronization detection pulse signal XDETP from the synchronization detector 24, respectively, A modulation signal for driving the semiconductor laser of the LD unit 19 is output at the timing. Note that the print clock may be generated inside the controller 39.

The modulation signal from the controller 39 is LD
A signal for controlling on / off of the semiconductor laser of the unit 19, which may be a binary signal that switches between high and low depending on whether it is on or off one pixel at a time, or pulse width modulated one pixel at a time according to the image density It may be a signal. The modulation signal output from the controller 39 is output to the
In order to irradiate a laser beam to the synchronization detector 24 and obtain a synchronization detection signal, the forcible lighting circuit 35 performs an OR operation with a forcible lighting signal for forcibly lighting the semiconductor laser of the LD unit 19 to generate an LD modulation section. 18 is output.

The modulation signal output from the controller 39 is also taken into the pixel count circuit 40. The sampling clock generation circuit 43 generates a sampling clock for randomly extracting image data from the image data (image data printed on one sheet of printing paper) output from the controller 39. For example, one sampling clock of A3 size A sampling clock for randomly extracting image data of 1000 pixels from image data to be printed on paper is generated.

The pixel count circuit 40 samples the on / off state of the modulation signal from the controller 39 using the sampling clock from the sampling clock generation circuit 43, counts the number of on (or off) times, and counts the number. The numerical value is output to the CPU. The CPU calculates the ratio of the number of times of sampling per one sheet of printing paper to the number of times of on (or off) from the count value of the pixel number counting circuit 40 (the count value per sheet of printing paper). Is estimated by the above-described statistical method, and the toner supply amount is determined based on the estimated value. The developing unit is supplied with toner from a toner replenishing unit, and the toner replenishing unit is controlled by the CPU and supplied to the developing unit with the CP.
The toner is supplied by the toner supply amount determined by U.

According to the sixth embodiment, the LD unit 19 as light source means for generating a light beam, the polygon mirror 21 as deflection means for deflecting and scanning the light beam from this light source means, An image forming apparatus that scans a surface to be scanned with a light beam, exposes the light beam, modulates the light beam with a modulation signal generated from image data, and forms an image by forming a latent image on the scanned surface by modulating off. A pixel count circuit 40 as a counting means for sampling whether the light beam is on or off with an asynchronous sampling clock from the modulation signal, and counting the number of times the sampled light is turned on or off, The cumulative ON time of the luminous flux is determined by the ratio of the number of times of ON or OFF and the number of times of sampling counted by the means. Since the CPU is provided as an estimating unit, the control unit does not have a clock synchronized with the image data, and counts the lighting time of the light source unit when a modulation signal for directly driving the light source unit is input from the outside. The means can be realized with a simple and low-cost configuration.

Note that, in the sixth embodiment, the invention according to claim 7 may be applied so that the invention according to claim 6 can be realized with a simpler and lower-cost configuration.

It is desirable that the sampling clock has no periodicity with respect to the frequency of the image data from the viewpoint of random extraction of the image data. For example, image processing using a dither matrix in units of three pixels is performed. In the sampling of the image data at a cycle of a multiple of 3, the sampled information is shifted, and is not random sampling. However, this does not apply if the phase of the sampling clock is random in each line.

Therefore, the seventh embodiment of the present invention is the same as the fourth to sixth embodiments, except that the sampling clock generation circuits 42 and 43 are connected to the image data (image data from the trim circuit 33, controller This is a sampling clock generating circuit for generating a sampling clock having no periodicity with respect to the frequency of the modulation signal from the modulation signal 39.

According to the seventh embodiment, since the sampling clock has no periodicity with respect to the frequency of the image data, random sampling of the image data can be performed, and the data collection without deviation can be performed. And more accurate statistical values can be obtained.

Although the above embodiment is an image forming apparatus using a semiconductor laser, the present invention is directed to an image forming apparatus using a solid-state image forming element such as a light emitting diode array or an image forming apparatus performing image formation by ink jetting. And the like can be similarly applied.

[0081]

As described above, according to the first aspect of the present invention, a counting means for counting the number of black forming pixels can be realized with a simple and low-cost configuration by the above configuration. The number of black pixels in the population can be estimated. According to the second aspect of the present invention, with the above configuration, it is possible to realize, with a simple and inexpensive configuration, an accumulative addition means for accumulating and adding image data having a plurality of bits of density information to each pixel. With the configuration, the average value of the image data of the population can be estimated.

According to the third aspect of the present invention, with the above configuration, there is no clock synchronized with the image data in the control unit.
The counting means for counting the lighting time of the light source means when a modulation signal for directly driving the light source means is inputted from the outside can be realized with a simple and low-cost configuration, and the lighting time of the light source means with a simple and low-cost configuration Can be inferred.

According to the fourth aspect of the present invention, the counting means for counting the number of black forming pixels can be realized with a simple and low-cost structure. According to the invention according to claim 5,
According to the above configuration, it is possible to realize a simple and low-cost configuration of a cumulative addition unit for cumulatively adding image data in which each pixel has a weight of density.

According to the sixth aspect of the invention, with the above configuration, there is no clock synchronized with the image data in the control unit.
A counting means for counting the lighting time of the light source means when a modulation signal for directly driving the light source means is input from the outside can be realized with a simple and low-cost configuration. According to the seventh aspect of the invention, with the above configuration, the inventions of the fourth to sixth aspects can be realized with a simpler and lower cost configuration.

According to the eighth aspect of the present invention, the means for generating a sampling clock in the fourth or fifth aspect of the present invention can be realized with a simple and low-cost configuration. According to the ninth aspect of the invention, with the above configuration, more accurate statistical values can be obtained in the inventions of the fourth to sixth aspects.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a part of a print control unit according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing the same embodiment.

FIG. 3 is a block diagram showing a part of another embodiment of the present invention.

FIG. 4 is a block diagram illustrating a part of a print control unit according to another embodiment of the present invention.

FIG. 5 is a block diagram showing a pixel count circuit and a sampling clock generation circuit according to another embodiment of the present invention.

FIG. 6 is a block diagram showing a pixel count circuit and a sampling clock generation circuit according to another embodiment of the present invention.

FIG. 7 is a block diagram showing a part of another embodiment of the present invention.

[Explanation of symbols]

 19 LD unit 21 Polygon mirror 37, 40 Pixel count circuit 38, 41 Random extraction timing generation circuit 42, 43 Sampling clock generation circuit

Claims (9)

[Claims] 1. An image forming apparatus for forming an image based on image data, comprising: counting means for counting the number of black forming pixels by using a sample of image data randomly extracted from the image data. apparatus. 2. An image forming apparatus for forming an image from image data having a plurality of bits of density information in each pixel, wherein the image data is cumulatively added using samples of image data randomly extracted from the image data. An image forming apparatus comprising: A light source for generating a light beam; a deflecting device for deflecting and scanning the light beam from the light source device; In an image forming apparatus which forms an image by forming a latent image on the surface to be scanned by modulating the light beam on and off by a signal, an on / off state of the modulation signal at a random moment is sampled. The image forming apparatus further includes means for estimating the cumulative ON time of the light beam based on a ratio of the number of times of sampling and the number of times of ON or OFF. 4. An image forming apparatus for forming an image by image data input in synchronization with an image clock, wherein said image data is sampled by a sampling clock having a period different from said image clock, and An image forming apparatus comprising a counting unit for counting the number of black forming pixels. 5. An image forming apparatus for forming an image by a plurality of bits of image data input in synchronization with an image clock, wherein said image data is fetched by a sampling clock having a cycle different from said image clock, and said fetched image is An image forming apparatus comprising a cumulative addition unit for cumulatively adding data. 6. A light source means for generating a light beam, a deflecting means for deflecting and scanning the light beam from the light source means, and a light beam from the deflecting means for scanning a surface to be scanned and exposing the light beam, thereby producing a modulation system based on image data. In an image forming apparatus which forms an image by forming a latent image on the surface to be scanned by modulating the light beam on and off by a signal, the light beam is turned on or off by an asynchronous sampling clock from the modulation signal. Counting means for sampling whether there is, and counting the number of times the sampled on or off;
An image forming apparatus comprising: means for estimating the cumulative ON time of the light beam based on the ratio of the number of ONs or OFFs counted by the counting means to the number of times of sampling. 7. The image forming apparatus according to claim 4, wherein a cycle of said sampling clock is set to be slower than a cycle of a pixel clock. 8. An image forming apparatus according to claim 4, further comprising clock counting means for counting a pixel clock,
An image forming apparatus, wherein a signal generated each time the clock counting means counts a predetermined value is used as the sampling clock. 9. The image forming apparatus according to claim 4, wherein said sampling clock has no periodicity with respect to a frequency of said image data.