JPH05309868A - Inspection device and method of focus of led head - Google Patents

Abstract

PURPOSE:To enable swiftly and highly precisely an inspection of focus without requring a mechanism part such as a sensor moving table, by a method wherein pitches among dots each of a line sensor and LED head are made to differ from one another and a moire interference pattern is obtained on a light volume signal measured by the line sensor. CONSTITUTION:Since output signals of a line sensor 4 are read out electrically in order of dot number by a sensor signal treatment part 5, a signal pattern is put out as time sequence signal. Hereupon, since a pitch between dots of an LED head 1 and that of the line sensor 4 are different slightly from each other, the more a dot signal advances, the more a confronting relation between an LED dot of the LED head 1 and a detector dot of the line sensor 4 changes little by little and light volume inciding into detectors each of the line sensor 4 is changed little by little. Therefore, a light volume signal to be measured by the detectors each of the line sensor becomes a moirelike pattern. Therefore, the maximum value I max and minimum value I min of the moire pattern are obtained, through which an extent of coincidence of the focuses can be obtained quantitatively.

Description

Detailed Description of the Invention

[0001]

This invention relates to a printing device L
The present invention relates to an ED head focus inspection device and method.

[0002]

2. Description of the Related Art FIG. 16 is a block diagram showing a structure of a conventional focus inspection device for LED heads, 1 is an LED head to be inspected, and 2 is an L for turning on the LED head 1.
ED head drive unit, 3 is the focal plane of the LED head, 4 is a sensor that measures the light amount distribution of the LED head 1 while moving, and a sensor that outputs a light amount signal, and 5 is sensor signal processing that processes the light amount signal from the sensor 4. Part, 6 is the focal plane of the sensor 4, 7
Is a table for moving the sensor 4 along the focal plane of the sensor, 8 is a table drive unit for driving the table 7, 9 is a lighting pattern data signal to the LED drive unit 2,
The control unit outputs a signal for moving the sensor to the table drive unit 8, receives the light amount signal from the sensor signal processing unit 5, and analyzes the light amount signal.

Next, the operation will be described. The LED head drive unit 2 turns on or off each dot of the LED head based on the LED head lighting pattern signal from the control unit 9, and the sensor 4 measures the light amount distribution of the LED head irradiated on the focal plane 6. This is converted into an electric signal and output as a light amount signal. Since the sensor 4 moves by the table 7 while measuring the light amount distribution, the light amount distribution of the LED head is output as a time series signal.

FIG. 17 is an explanatory diagram showing the above relationship.
17A shows a lighting pattern when the LED head is lit every other dot, and FIG. 17B shows a light amount distribution of the LED head on the sensor focal plane 6.
(C) shows the light amount signal waveform read by the sensor 4 that moves in this light amount distribution, corresponding to the dot position of the sensor 4. The sensor signal processing unit 5 and the control unit 9 perform calculations for processing and evaluation of the above light amount signal.

Here, when the focal plane 3 of the LED head and the focal plane 6 of the sensor are coincident with each other, the contrast of the light amount distribution of FIG. 17 (b) is high, but when the focal planes are not coincident, the light amount distribution is not equal. Since the contrast is blurred and the contrast is lowered, it is necessary to use the maximum value and the minimum value of the light amount signal of FIG.
The degree of coincidence between the focal plane 3 of the head and the sensor focal plane 6 is calculated. In the product inspection, when the degree of coincidence of the focal planes is poor, the mounting positions of the LED head and the lens array are adjusted, and the focus inspection is repeated.

[0006]

Since the conventional focus inspection device for the LED head is constructed as described above, it is necessary to move the sensor over the entire length of the LED head during the focus inspection, which requires a long time for the inspection. There was a problem. Further, since a moving mechanism is required, the apparatus becomes complicated and large, and the dimensional error of the moving mechanism lowers the accuracy of focus inspection.

The present invention has been made in order to solve the above-mentioned problems of the conventional focus inspection apparatus, and does not require a mechanical portion such as a table for moving a sensor and enables the focus inspection to be performed quickly and with high accuracy. An object of the present invention is to provide a focus inspection device for an LED head and a focus inspection method suitable for such a focus inspection device.

[0008]

An LE according to claim 1
The focus inspection device for the D head includes a line sensor having a plurality of detectors arranged at equal intervals, and the dot pitch of the line sensor is different from the dot pitch of the LED head. A moire interference pattern is generated in the signal.

A focus inspection apparatus for an LED head according to a second aspect of the present invention is the focus inspection apparatus for an LED head according to the first aspect, wherein a gap is provided between the detectors of the line sensors.

A focus inspection device for an LED head according to a third aspect of the present invention is the focus inspection device for an LED head according to the first or second aspect, in which the shape of the detector of the line sensor is changed in the main scanning direction. The shape is longer in the sub-scanning direction than the above.

According to a fourth aspect of the present invention, there is provided a focus inspection device for an LED head, which comprises a light-shielding mask having slits arranged at equal intervals, and the pitch between the slits of the light-shielding mask is LE.
Due to the difference in the pitch between the dots of the D head, a moire interference pattern is generated in the amount of transmitted light of the light shielding mask.

According to a fifth aspect of the present invention, there is provided a method for inspecting a focus of an LED head, wherein the LED head comprises a plurality of detectors arranged at equal intervals, and a line sensor having a dot pitch different from that of the LED head. Is placed opposite to the L
The maximum value and the minimum value of the light amount signal of the moire pattern of the line sensor obtained by turning on the ED head every other dot were used.

A focus inspection method for an LED head according to a sixth aspect is the focus inspection method for an LED head according to the fifth aspect, wherein each of the LED heads has a lighting section and a light-out section which are each formed of an arbitrary plurality of dots. It was lit in a repeating pattern of sections.

A focus inspection method for an LED head according to a seventh aspect is the focus inspection method for an LED head according to the fifth aspect, wherein the light amount signal of the moire pattern is compared with a standard pattern. did.

A focus inspection method for an LED head according to claim 8 is the focus inspection method for an LED head according to claim 5, wherein the sum and difference of the light amount signals of adjacent two dots of the light amount signals. Was used.

According to a ninth aspect of the method for inspecting a focus of an LED head, a light-shielding mask having slits arranged at equal intervals and having a pitch between slits different from a pitch between dots of the LED head is arranged to face the LED head. The LED
A transmitted light pattern of the light-shielding mask obtained by lighting the head in a repeating pattern of a lighting section and a non-lighting section each consisting of an arbitrary integer dot was used.

[0017]

In the focus inspection device for the LED head according to the first aspect, when the light emission pattern of the LED head is read by the line sensor, the light quantity signal of the line sensor is generated due to the difference in dot pitch between the LED head and the line sensor. A moire pattern having a period which is the least common multiple of the pitch between the dots of the line sensor and the lighting pattern period of the LED head is generated. This moire pattern changes depending on whether the focal plane of the LED matches the focal plane of the line sensor.

In the focus inspection device for the LED head according to the second aspect, since the gap is provided between the detectors of the line sensor, the moire pattern is measured in the form of being picked up every other dot, which is different. A morphological moire pattern is obtained. This moire pattern also changes depending on the degree of coincidence of the focal planes.

In the focus inspection device for the LED head according to the third aspect, since the shape of each detector of the line sensor is lengthened in the sub-scanning direction, the relative position of the LED head and the line sensor is deviated in the sub-scanning direction. Even if there is an angle error along the focal plane, the light amount signal of the line sensor does not change, so that an accurate focus inspection can be performed even if there is the above mounting error.

In the focus inspection device for an LED head according to claim 4, when the light emission of the LED head is seen through the light-shielding mask, the light-shielding mask is caused by the difference in the pitch between the dots of the LED head and the pitch between the slits of the light-shielding mask. A moire pattern whose period is the slit pitch and the least common multiple of the lighting pattern period of the LED head can be seen. The difference in brightness between the moire patterns becomes maximum when the focal plane of the LED head coincides with the light-shielding mask surface.

According to the fifth aspect of the LED head focus inspection method, the ratio of the maximum value and the minimum value of the light amount signal is maximized when the focal plane of the LED head and the focal plane of the line sensor are coincident with each other. Can be used to quantitatively inspect the degree of coincidence of the focal planes.

According to the sixth aspect of the LED head focus inspection method of the present invention, since the lighting pattern of the LED head is a repeating pattern of a lighting section and a non-lighting section each consisting of an arbitrary integer dot, the line sensor having a large dot pitch. The focus inspection of the LED head having a small dot pitch can be performed by using.

In the focus inspection method of the LED head according to the seventh aspect, if there is an error in the light emission amount or the focus position of each dot of the LED head, irregularity occurs in the moire pattern of the light amount signal, so that it is a regular rule. The defective dot of the LED head can be detected by comparison with a standard pattern.

In the focus inspection method of the LED head according to the eighth aspect, the sum of the light amount signals of two adjacent dots of the line sensor corresponds to the light emission amount of the opposite LED dots, and the difference is the displacement of the position of the LED dots. It is possible to inspect the amount of light emission and the position of each dot of the LED head by utilizing the information that indicates

In the focus inspection method of the LED head according to the ninth aspect, when the light emission of the LED head is viewed through the light shielding mask, the light shielding mask of the A moire pattern whose cycle is the least common multiple of the pitch between slits and the lighting pattern cycle of the LED head can be seen. The difference in brightness between the moire patterns becomes maximum when the focal plane of the LED head coincides with the light-shielding mask surface.

[0026]

【Example】

Example 1. FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention, 1 is an LED head to be inspected, 2 is an LED head drive unit for lighting the LED head 1, 3 is a focal plane of the LED head 1, 4 is a line sensor that measures the light amount distribution of the LED head 1 and outputs a light amount signal, 5 is a line sensor signal processing unit that processes the light amount signal from the line sensor 4, 6 is the focal plane of the line sensor 4, and 9 is an LED It is a control unit that outputs a lighting pattern data signal of the LED head to the head drive unit 2 and receives a light amount signal from the sensor signal processing unit 5 for analysis.

FIG. 2 is a diagram showing a dot arrangement of the LED head 1 and the line sensor 4. In the figure, the dot pitch of the line sensor is slightly different from the LED dot pitch. The LED dot pitch is 125 μ.
The dot pitch of the line sensor is 117.65 μm (8.5 dots / mm) for m (8 dots / mm). According to this arrangement, 16 dots are arranged in the LED head and 17 dots are arranged in the line sensor in 2 mm, which is a repeating cycle of the arrangement.

Next, the operation will be described. Figure 3 shows LED
5 is an explanatory diagram showing a relationship between lighting of the head 1 and measurement of a light amount by the line sensor 4. FIG. FIG. 3A shows an LED head 1
A lighting pattern in which dots are lit, FIG. 3B is a light amount distribution on the focal plane 6 of the line sensor, FIG. 3C is a detector array of the line sensor, and FIG. 3D is a light amount distribution of the LED head. The light amount signal read by each detector of the sensor is shown. Since the output signal of the line sensor is electrically read by the sensor signal processing unit 5 in the order of the dot number,
The signal pattern of FIG. 3D is output as a time series signal. As mentioned above, the dot pitch of the LED head and the dot pitch of the line sensor are slightly different,
As the dot number advances, the facing relationship between the LED dots of the LED head and the detector dots of the line sensor changes little by little, and the amount of light incident on each detector of the line sensor changes little by little. Therefore, the light amount signal measured by each detector of the line sensor has a moire pattern as shown in FIG. FIG. 5 shows the moire pattern of FIG. 5D over a wide range.

The moire pattern has various forms _depending on the relationship between the dot pitch P _LED of the LED head and the dot pitch P _LS of the line sensor, but the patterns shown in FIGS. 3D and 5 are obtained. Requires the relation of the following equation, where n is an integer. At this time, the repetition period L of the moire pattern can be expressed by the following equation.

Next, a focus inspection method will be described. Figure 3
Shows the case where the focal plane 3 of the LED head and the focal plane 6 of the line sensor are in agreement with each other in FIG. 1, but FIG. 4 shows the case where the two focal planes are not in agreement. Two
When the two focal planes are coincident with each other, as shown in FIG. 3B, the contrast of the light amount distribution on the focal plane of the line sensor is large and the amplitude of the moire pattern in FIG. When the surfaces do not match, the contrast of the light amount distribution is lowered as shown in FIG. 4B, and the amplitude of the moire pattern is reduced as shown in FIG. 4D. Therefore, as shown in FIG. 5, the maximum value Imax and the minimum value Imin of the moire pattern can be obtained, and from this, the degree of focus matching can be quantitatively obtained. The MTF of the following equation is used as an index of the degree of coincidence of the focal planes. The above signal processing and calculation are performed by the sensor signal processing unit 5 and the control unit 9.

As described above, the focus inspection according to the present embodiment does not require the movement of the sensor by the mechanical section and can be performed quickly because it depends only on the electrical signal processing, and the accuracy due to the dimensional error of the mechanical section is high. There is no decrease.

In the present embodiment, in addition to the inspection of the degree of coincidence of the focal planes of the LED heads, the focus inspection of individual LED heads of the LED heads can be performed. In the moire light amount signal pattern of the line sensor shown in FIG. 5, if the light emission amounts of the dots of the LED head are equal and the arrangement is regular, the same pattern is repeated. If there is irregularity in the light emission amount or array position of a specific LED head, it appears as the irregularity of the above-mentioned moire pattern, and therefore defective dots can be detected by comparison with a standard pattern. The standard pattern as a reference for comparison is obtained by actually measuring the moire pattern data over a wide range shown in FIG. 5 for the LED heads of the same design and averaging the data in each cycle.

Detailed data of each LED dot can be obtained as follows. At a 3, since the n-th light emission of the LED dot is measured as intensity signal I _n and I _{n + 1} of the n th and (n + 1) th dot line sensor, I _n and I
The sum of _{n + 1} indicates the light emission amount of the nth LED dot. That is, the light emission amount of the n-th LED dot = I _n + I _{n + 1} (4) Next, looking at the difference between I _n and I _{n + 1} , as is apparent from FIG. If the LED dot is slightly shifted to the right, I _n decreases and I _{n + 1} increases, so I _n and I
The difference of _{n + 1} is information indicating the displacement of the position of the nth LED dot. As an index of the position of the LED dot that is not affected by the light emission amount, the following equation normalized by the light emission amount of the equation (4) may be used. Since the index of the position of the equation (5) is a complex number of the dot number n, a standard pattern to be used as a reference for comparison is prepared in advance based on the measured data of the LED heads of the same design. The displacement of the position of the LED dot is calculated by comparison.

In FIG. 2, in order to make the dot pitch between the LED head and the line sensor slightly different, the dot pitch between the LED heads is 125 μm (8 dots / m).
m) the dot pitch of the line sensor is 117.65μ
Although it was slightly narrowed to m (8.5 dots / mm), they are slightly different, and if the relationship of equation (1) is satisfied, a moire pattern can be obtained in the same way, and the same effect can be obtained. For example, the pitch between the dots of the sensor is 133.33 μm
It may be a little wider, such as (7.5 dots / mm). However, since in this case the detector of the line sensors corresponding to the n-th LED dot At a 3 replace n-1 th and n th, formula (4), I _n and I _{n + 1} (5) Is I _n-1 and I _n
Instead of. Further, the period L of the moire pattern does not have to be limited to 16 dots (2 mm) of the LED head, and the pitch between the dots of the line sensor can be set so that the desired repeating period L can be obtained based on the equations (1) and (2). May be set. For example, if n = 24 and the dot pitch of the line sensor is 120 μm (8.33 dots / mm), the period is 3000 μm (3 mm) according to the equation (2). Ie

In this embodiment, since the LED head is turned on every other dot, in order to inspect all the LEDs, the blinking pattern of the LEDs is reversed and inspected.

Example 2. In the first embodiment, as shown in FIG. 6A, the line sensor 4 has a square detector shape. In this case, the LED head 1 and the line sensor 4 must be accurately positioned relative to each other. is there. If the line sensor deviates from the LED head in the Y direction (sub-scanning direction) of FIG. 6C or if there is an angle error in the O direction, accurate light amount measurement cannot be performed, and an error occurs in the focus inspection data. In the second embodiment, as shown in FIG. 6B, the detector shape of the line sensor is made longer in the Y direction (sub-scanning direction) than in the X direction (main scanning direction).
Directional angular error is acceptable and no focus inspection error occurs.

Example 3. In Example 3 shown in FIG. 7, the pitch between dots of the line sensor 4 is slightly different from twice the pitch between dots of the LED head 1, and a space is provided between the detectors of the line sensor. .. Figure 7
(A) is a lighting pattern in which the LED head is lit every other dot, and (b) is L on the focal plane 6 of the line sensor.
The light amount distribution of the ED head, (c) shows the detector array of the line sensor, and (d) shows the light amount signal obtained by reading the light amount distribution of (b) with the line sensor. The light amount signal (d) is shown by a solid line corresponding to the detector position, but the signal waveform read as a time series signal has an envelope like a dotted line.

In FIG. 7, the pitch between dots of the LED head
The line sensor dot pitch is 235.3 μm (4.25 dots / mm) compared to 125 μm (8 dots / mm).
It is slightly narrower than the double pitch (250 μm) of the dot pitch of the ED head. The width of each detector of the line sensor is 117.65 μm, which is ½ of the pitch between dots. According to this array, 32 dots of the LED head and 17 dots of the line sensor are arrayed within 4 mm, and this is the repeating cycle of the array. The cycle L of the array is represented by the following equation, where n is an integer.

The light amount signal pattern of FIG. 7D is the first embodiment.
Similarly, a moire pattern is formed, but this pattern is obtained by taking out the light amount signal pattern of FIG. 3D in Example 1 every other dot, and connecting the odd-numbered signal values of FIG. 3D. It is an envelope. FIG. 8A shows FIG.
FIG. 8D shows the moire pattern of FIG. 8D over a wide range, and FIG. 8B is a signal pattern when the lighting pattern of the LED head is reversed from that of FIG. 7A. FIG. 9 shows FIG. 8A and FIG.

Also in this embodiment, as shown in FIG. 8 or 9, the maximum value Imax and the minimum value Imi are calculated from the light amount signal pattern.
It is possible to inspect the degree of coincidence between the LED head and the focal plane of the line sensor by calculating n and calculating the MTF of (3) as in the first embodiment.

The dot pitch of the line sensor does not have to be limited to the example shown in FIG. 7, and the LED is set so that an appropriate moire pattern cycle can be obtained based on the equation (6).
The value may be slightly different with respect to twice the dot pitch of the head. Further, the detector width of the line sensor in FIG. 7C is not particularly limited as long as there is a space between the detectors, but the pitch between dots is 1
The closer to / 2, the greater the contrast of the moire pattern.

Example 4. In Example 4 shown in FIG. 10, the dot pitch of the line sensor 4 is slightly different from an integer multiple of the dot pitch of the LED head, and the LED heads are alternately turned on by the unit of the integer dots. .. FIG. 10A shows an LED when the integer is 2.
The lighting pattern of the head is shown.

The light amount signal pattern in this embodiment (see FIG.
0 (d)) is the same as FIG. 3D in the first embodiment, and the maximum value Ima is obtained from the light amount signal pattern as in the first embodiment.
x and the minimum value Imin are obtained, and the LED is calculated based on the equation (3).
The degree of coincidence between the head and the focus of the line sensor can be inspected.
In this embodiment, a line sensor having a large dot pitch can be used to perform focus inspection of an LED having a small dot pitch.

Example 5. In Example 5 shown in FIG. 11, a space is provided between detectors by making the dot pitch of the line sensor slightly different from an integer multiple of the dot pitch of the LED head, and the LED head is made to cycle the integer dots. It is lit in the pattern. FIG. 11 (a)
Shows an example in which the above-mentioned integer is 4 and the LED head is lit in a pattern of blinking every 2 dots with 4 as the cycle. FIG. 11C shows an example in which the space between the detectors of the line sensor is ½ of the dot pitch.

The light amount signal pattern of FIG. 11D is the same as that of FIG. 7D in the third embodiment, and the maximum value Imax is obtained from the light amount signal pattern of FIG. 8 or 9 as in the third embodiment.
And the minimum value Imin are obtained, and based on the equation (3), LE
The degree of coincidence between the D head and the focal plane of the line sensor can be inspected. Also in this embodiment, similarly to the fourth embodiment, it is possible to perform the focus inspection of the LED head having the small dot pitch by using the line sensor having the large dot pitch.

The space between the detectors of the line sensor is not limited to 1/2 of the dot pitch, but 1 /
The closer to 2, the greater the contrast of the moire pattern, which is advantageous. It is desirable that the LED head lighting pattern also has the above-mentioned integer as a cycle, 1/2 of the above-mentioned integer is turned on, and the rest is turned off. From this point, it is desirable that the integer is an even number.

Example 6. FIG. 12 is a block diagram showing the configuration of the sixth embodiment. The present embodiment uses a light-shielding mask 10 having an array of slits instead of the line sensor 4 and the sensor signal processing unit 5 of the first embodiment shown in FIG.
The pitch between the slits of the light shielding mask is slightly different from twice the pitch between the dots of the LED head, and the LED head is lit every other dot.

FIG. 13A shows the lighting pattern of the LED head, and FIG. 13B shows the slit arrangement of the light-shielding mask 10.
(C) shows the transmitted light amount pattern of the light shielding mask.
In the figure, the dot pitch of the LED head is 125 μm (8
The dot pitch is 235.3 μm (4.25 lines / mm), which is twice the dot pitch of the LED head (25 dots).
(0 μm). The width of the slit is 117.65 μm, which is ½ of the pitch between slits.

The slit arrangement in FIG. 13B is shown in FIG. 7C.
Since it is the same as the detection array of the line sensor of the third embodiment shown in FIG. 13, the transmitted light amount pattern of FIG. 13C is the same as the light amount signal pattern of FIG. 7D in the third embodiment. In this embodiment, there is no means for electrically measuring the light quantity signal, but the transmitted light quantity pattern of FIG. 13C can be directly observed with the naked eye in the direction of the arrow of FIG. In the transmitted light amount pattern, the brightness difference becomes maximum when the focal plane of the LED head coincides with the light-shielding mask surface, so that there is an advantage that the focal position of the LED head can be adjusted very easily while observing the brightness difference.

Although the slit width of the light-shielding mask is not particularly limited, it is advantageous that the lightness difference between the transmitted light amount patterns becomes clearer as the slit width becomes closer to ½ of the pitch between the slits.

The pitch between the slits may be a slightly different value with respect to an arbitrary integral multiple of the pitch between the dots of the LED head. In this case, the lighting pattern of the LED head may be a pattern having the above integer as a cycle. Similar to the fifth embodiment, the focus inspection of the LED head having a small dot pitch can be performed by using the slit arrangement having a large pitch.

Example 7. In Example 7 shown in FIG. 14, instead of making the line sensor 4 correspond to the entire length of the LED head 1, the line sensor 4 is provided only at two positions near both ends of the LED head. FIG. 14A is an elevation view showing the configuration of this embodiment, and FIG. 14B is a plan view. The line sensor 4 is composed of two partial line sensors 4a and 4b provided in the vicinity of both ends of the LED head. When the purpose of the focus inspection is to inspect the position of the focal plane of the entire LED head and does not require local focal position information, or when the flatness of the focal plane 6 of the LED head is sufficiently guaranteed. , Figure 1
The objective can be achieved even by a focus inspection limited to two places on the focal plane as in 4. By doing so, the focus inspection of a large LED head can be efficiently performed. Further, the distance between the two line sensors 4a and 4b can be made variable and used for the inspection of LEDs of various sizes.

Example 8. The eighth embodiment shown in FIG. 15 is a photosensitive drum 1 shown in FIG.
Instead of 5, the line sensor 4 can be attached to the print surface position of the photosensitive drum as shown in FIG. 15 (b). When the focus inspection and adjustment are performed with the LED head mounted on the printer device, conventionally, the print pattern for focus inspection such as a checkerboard pattern is printed, but according to the configuration shown in FIG. If so, focus inspection and adjustment can be performed easily and efficiently.

Example 9. The line sensor may or may not use a reduction optical system, and may be a thin film type sensor or a multi-chip type sensor. A line sensor that does not use a reduction optical system has an advantage that an error caused by the optical system can be avoided.

Example 10. In the above embodiment, the time-series light intensity signal pattern of the line sensor 4 may be displayed on an oscilloscope (not shown), and the focus inspection and adjustment may be performed while observing the waveform. This way the LED
The focus of the head can be adjusted easily and quickly.

Example 11. LED on the line sensor 4
An optical filter may be provided to block light other than the light emission of. By doing so, it is possible to prevent an error in focus inspection due to incident light other than the light from the LED.

Example 12 The light-shielding mask having the slit may be a metal plate etched,
It is also possible to form a light-shielding mask on glass or a transparent film and etch it.

Example 13 The line sensor 4 may mask unnecessary portions other than the detector dots in order to block intruding light from around the detector dots. By doing so, it is possible to prevent an error in the focus inspection due to the light penetrating from around the detector dots.

[0059]

In the focus inspection device for LED heads according to the first to third aspects, the focus inspection can be performed by using the light amount signal of the moire pattern measured by the fixed line sensor. Unlike the inspection device, it is not necessary to move the sensor over the entire length of the LED head during the focus inspection, and the focus inspection can be performed quickly. Further, since the mechanism for moving the sensor is not required, the device can be simplified and downsized. Further, since there is no sensor moving mechanism, there is no reduction in focus inspection accuracy due to dimensional error of the moving mechanism.

In the LED head inspection device according to the third aspect of the present invention, since the detector of the line sensor has a long shape in the main scanning direction, the relative position of the LED head and the line sensor is displaced in the sub scanning direction, or the focal plane. Even if there is an angular error along the line, accurate focus inspection can be performed without causing an error in the light amount measurement.

In the LED head inspecting device according to the fourth aspect, the focus inspection can be performed by using the transmitted light amount pattern of the fixed light-shielding mask having a moire pattern. Focus inspection can be performed quickly without the need to move the LED head over the entire length.
Further, since the sensor and the moving mechanism of the sensor are not required, the device can be simplified and downsized. Further, since there is no sensor moving mechanism, there is no reduction in focus inspection accuracy due to dimensional error of the moving mechanism. Also, with this focus inspection device, the inspection result can be viewed directly with the naked eye, so the inspection result can be immediately
It can be used for focus adjustment of the ED head, and focus adjustment can be performed easily and quickly.

In the focus inspection method for the LED head according to the fifth to ninth aspects, it is not necessary to move the sensor over the entire length of the LED head as in the conventional focus inspection method, and therefore the focus inspection can be performed quickly. Further, since the sensor moving mechanism is not provided, the focus inspection accuracy does not deteriorate due to the dimensional error of the moving mechanism.

In the focus inspection method of the LED head according to claims 5 to 7, since the maximum value and the minimum value of the light amount signal of the moire pattern of the line sensor are used, the focal plane of the LED head and the line sensor are detected. The degree of coincidence of the focal planes can be inspected quantitatively.

According to the seventh aspect of the LED head focus inspection method, the defective dot of the LED head can be detected by comparing the light amount signal of the moire pattern of the line sensor with the standard pattern.

In the LED head inspecting method according to the eighth aspect, the light emission amount and position of each detector dot of the LED head is calculated by using the sum and difference of the light amount signals of two adjacent dots of the light amount signal of the line sensor. Can be inspected.

In the focus inspection method of the LED head according to the ninth aspect, the fact that the amount of transmitted light of the light-shielding mask has a moire pattern is used, and the focal plane of the LED head and the focal plane of the line sensor are visually observed with the naked eye. The degree of coincidence can be checked. Further, in this focus inspection method, since the inspection result can be directly viewed with the naked eye, the inspection result can be immediately used for the focus adjustment of the LED head, and the focus adjustment can be performed easily and quickly.

In the focus inspection method according to the sixth and ninth aspects, a line sensor with a large pitch between dots is obtained by lighting the LED head in a repeating pattern of a lighting section and a non-lighting section each consisting of an arbitrary plurality of dots. Alternatively, the focus inspection of the LED head having a small dot pitch can be performed by using a light-shielding mask having a large pitch between slits.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing dot arrays of the LED head and the line sensor according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a lighting pattern of the LED head and a light amount signal pattern of the line sensor according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a case where the focal plane of the LED head in FIG. 3 is displaced.

FIG. 5 is an explanatory diagram showing a light amount signal pattern of the line sensor according to the first embodiment of the present invention over a wide range.

FIG. 6 is a plan view showing a detector shape of a line sensor according to a second embodiment of the present invention.

FIG. 7 is an explanatory diagram showing Embodiment 3 of the present invention.

FIG. 8 is an explanatory diagram showing a light amount signal pattern of a line sensor according to a third embodiment of the invention.

FIG. 9 is an explanatory diagram showing a light amount signal pattern of a line sensor according to a third embodiment of the present invention.

FIG. 10 is an explanatory diagram showing Embodiment 4 of the present invention.

FIG. 11 is an explanatory diagram showing Embodiment 5 of the present invention.

FIG. 12 is a block diagram showing a configuration of a sixth embodiment of the present invention.

FIG. 13 is an explanatory diagram showing a lighting pattern of an LED head and a transmitted light amount pattern of a light shielding mask according to a sixth embodiment of the present invention.

FIG. 14 is a structural diagram showing a line sensor according to a seventh embodiment of the present invention.

FIG. 15 is an explanatory diagram showing Embodiment 8 of the present invention.

FIG. 16 is a block diagram showing a configuration of a conventional focus inspection device for an LED head.

FIG. 17 is an explanatory diagram showing an operation of a conventional focus inspection device for an LED head.

[Explanation of symbols]

 1 LED head 2 LED head drive unit 3 Focal plane of LED head 4 Sensor or line sensor 5 Sensor signal processing unit 6 Focal plane of sensor or line sensor 7 Table 8 Table drive unit 9 Control unit 10 Light-shielding mask 15 Photosensitive drum

Claims (9)

[Claims] 1. A line sensor having a plurality of detectors arranged at equal intervals, wherein the dot pitch of the line sensor is different from the dot pitch of the LED head so that the light amount signal measured by the line sensor is moire. Inspection device for LED head, which produces a linear interference pattern. 2. The focus inspection apparatus for an LED head according to claim 1, wherein a gap is provided between the detectors of the line sensor. 3. The focus inspection of the LED head according to claim 1, wherein the shape of the detector of the line sensor is longer in the sub scanning direction than in the main scanning direction. apparatus. 4. A light-shielding mask having slits arranged at equal intervals is provided, and a pitch between slits of the light-shielding mask is different from a pitch between dots of the LED head, so that a moire interference pattern is generated in a transmitted light amount of the light-shielding mask. A focus inspection device for an LED head, characterized in that 5. A line sensor having a plurality of detectors arranged at equal intervals, the line sensor having a pitch between dots different from the pitch between dots of the LED head is arranged facing the LED head.
A focus inspection method for an LED head, comprising using the maximum value and the minimum value of a light amount signal of a moire pattern of the line sensor obtained by lighting the LED head every other dot. 6. The method for inspecting a focus of an LED head according to claim 5, wherein the LED head is lit in a repeating pattern of a lighting section and a non-lighting section each including an arbitrary plurality of dots. 7. The focus inspection method for an LED head according to claim 5, wherein the irregularity of the moire pattern is detected by comparing the light amount signal of the moire pattern with a standard pattern. . 8. The sum and difference of the light quantity signals of two adjacent dots of the light quantity signal are used.
Item 4. A focus inspection method for an LED head according to the item. 9. A light-shielding mask, which has a plurality of slits arranged at equal intervals and has a pitch between slits different from a pitch between dots of the LED head, is arranged to face the LED head.
A focus test of an LED head, which uses a difference in brightness of a moire-like transmitted light pattern of the light-shielding mask obtained by lighting the LED head in a repeating pattern of a lighting section and an extinguishing section each consisting of an arbitrary integer dot. Method.