JPH03264837A - Apparatus for measuring distribution of light intensity of light emitting array - Google Patents

Abstract

PURPOSE:To perform measurement highly accurately without the effects of the dot size, pitch or the like of a light emitting array by receiving the data of a photosensor when the image of the measuring dot of the light emitting array is located at a position which is not rejected by a slit all the time. CONSTITUTION:The dot size of a light emitting arrays 1 is made to be (a), and the dot pitch is made to be (b). The magnification of an objective lens is (m). For example, images 6b - 6d are shown on the imagery surface of dots 1b - 1d. A slit forming member 3 having a slit 4 whose width is (c) is provided on the imagery surface such as this. A photosensor 5 is provided at the rear side of the member 3. When the lens 2 and the light emitting array 1 are realtively moved at an equal velocity (v), the image 6c of the light emitting dot 1c is moved at 2 velocity (mv) in the vicinity of the imagery surface. The next image 6b arrives at the center of the slit 4 after a specified time. When the image of the measuring dot of the light emitting array is located at a position which is not rejected by the slit 4 all the time, timing is controlled so as to receive the data of the photosensor.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a light intensity distribution measuring device for a light emitting array such as an LED array.

2. Description of the Related Art In general, light emitting arrays such as LED arrays and fluorescent tube dot arrays are used as solid-state scanning optical writing light sources for photoreceptors in digital copiers, facsimile machines, printers, and the like. In this case, in order to manage and control print quality, a device that measures and evaluates the light intensity distribution in the array direction of the light emitting array is required.

There is a measuring device for this purpose as shown in FIG. 5 (first conventional example). Dots la to Ig by light emitting elements
A light emitting array 1 consisting of the following is fixed on a stage (not shown) and is movable in the array direction. A slit forming member 3 is provided at a predetermined distance from the objective lens 2 on the optical path of the light transmitted through the objective lens 2 disposed facing the light emitting array l. A photosensor 5 is disposed near the optical path of the light that has passed through the slit 4 of the slit forming member 3. Here, the dot density of the light emitting array 1 is 300 dpi (the dot pitch b is b=84
．． 6 μm), the magnification m of the objective lens 2 is 4 times, and the width C of the slit 4 is c=3384 (=84, 6X4=4
(value corresponding to b) μm.

When measuring the light intensity distribution of the light emitting array 1 using this device, the light emitting array l is moved with one of its dots la-1g in a non-emitting state and at a constant speed V in the array direction by a stage. At the same time, the light from the light emitting array 1 is transmitted through the objective lens 2 and expanded four times to form an image 6 (imaging surface 60 to
6e is exemplified). This image 6 moves in the opposite direction to the moving direction of the light emitting array l. At this time, the light that has passed through the slit 4 enters the photosensor 5 and its light intensity is detected. This detected value is 21.1 for the light emitting array l.
Data is captured every time it moves by 5 μm (l/4 of one dot pitch).

From such data in the - group, every fourth data is picked up using the data of the non-emitting dots as a reference, and each of these data values is used as the light intensity of each dot in the light emitting array.

In addition, in the configuration shown in FIG. 5, the width C of the slit 4 is c=
1011 m, and there is also one in which the magnification m of the objective lens 2 is set to 1 (second conventional example). According to this method, the detection value of the auto sensor 5 is taken in as data every time the light emitting array l moves by 10 pm. This data is divided into a light-emitting part and a non-light-emitting part depending on the positional relationship between the slit 4 and the imaging surface 6 at the time of data acquisition, and each part is formed by a plurality of pieces of data. A plurality of pieces of data (if the dot size is 50 pm, five or six pieces of data) of the light emitting part are combined to form the light intensity of one dot.

That is, the amount of light for one dot is obtained by adding together several pieces of light that have passed through a slit whose width is narrower than the image size of the dot.

Problems to be Solved by the Invention In the case of the second conventional example, it is not possible to eliminate errors caused by uneven feeding in the relative movement of the objective lens 2 and the light emitting array l. Further, if the slit width is further narrowed in an attempt to improve accuracy, the amount of light received by the photosensor 5 decreases, which also becomes a cause of worsening measurement accuracy. The burden of data processing is also large.

On the other hand, in the case of the first conventional example, 4·v for the moving speed V
/b data is taken in every time. Therefore,
Although there is a data processing burden, measures such as providing a pair of non-luminous dots on the light-emitting array that serve as markers at both ends reduce the burden compared to the second conventional example, making it possible to perform highly accurate measurements. It is. However, according to the conditions of the first conventional example, for example, if the dot size a changes such that a = 20 pm, if the dot pitch b changes, or if there is unevenness in the moving speed V, the light-emitting dots will not move due to the slit. In some cases, the light intensity value of a particular dot cannot be measured with high accuracy.

For this reason, a measuring device as shown in FIG. 6 has been proposed by the present applicant in Japanese Patent Application No. 1-157963. This means that a deflection mirror 7 that deflects a part of the light transmitted through the objective lens 2 is placed near the slit forming member 3 at 45.
The photo sensor 5 is installed at an angle of 1.degree., and the reflected light is detected by another photosensor 8 to obtain the capture timing, and data from the original photosensor 5 is captured in synchronization with this timing.

Here, for example, the magnification m of the objective lens 2 is 1, the width C of the slit 4 is 60)+m, the dot size a is 50 pm,
The dot-to-dot size is 34.6 μm, and the moving speed is 5 cm.
/s.

In such a configuration, when measuring the light intensity distribution of the light emitting array 2, the light emitting array 1 moves to the left in the figure. For example, as shown in FIG. 7, when a part of the light forming the imaging surface 6d of the dot 1d is incident on the deflection mirror 7, this light is reflected by the deflection mirror 7 and enters the photosensor 8, and the light is reflected by the deflection mirror 7. Intensity is detected. Thereafter, the light emitting array 1 further moves, and as shown in FIG. (image formation of the non-emitting part) is the deflection mirror 7
The state will be located at . At this time, no light enters the deflection mirror 7 or the photosensor 8, and all of the light forming the imaging plane 6d enters the photosensor 5. Therefore, when the detected value of the photosensor 8 becomes O, each dot is at an appropriate position when the detected value of the photosensor 5 is taken in as data.

The allowable range for the dot deviation from the proper position is:
It is determined by the dot size and the size between dots, and in the above proposed example, it is ±5 μm. Here, since the moving speed of the light emitting array 1 is 5CITl/S, the allowable range of the deviation in the measurement timing for taking in the detection value of the photosensor 5 as data is ±10011S. Therefore, if the measurement timing is set using an external device or the like 100 ps after the moment when the detection value of the photosensor 8 suddenly decreases, accurate values of the light intensity of each dot can be obtained.

According to this proposed method, since the deviation in measurement timing is small, highly accurate measurement is possible. However, the design and machining of the optical system including the deflection mirror 7 and the like are difficult and costly, and as a result, measurement accuracy may actually be lowered.

Means for Solving the Problems An objective lens is provided facing a light emitting array in which a large number of light emitting element dots are arranged, and a slit forming member having a slit is provided near the image formation plane of the light emitting array by the objective lens. A light intensity distribution measuring device for a light emitting array, wherein a photosensor is provided on the optical path of the light passing through the slit, and the objective lens, the slit forming member, the photosensor, and the light emitting array are moved relative to each other. Each dot size is a, dot arrangement pitch is b
, the slit width is c, the magnification of the objective lens is m, and b
When the relationship ≧c/m≧a is satisfied, and when the light emitting array and the objective lens are moved at a relative speed V, the maximum value of the deviation amount of uneven feeding with respect to this relative speed ■ is defined as X, In the invention according to claim 1, n≧b/(
(c/m)-a-2X}≧O for an integer n satisfying the relationship: b/nv; / n v When capturing data from the photosensor at time intervals, n≧b/{(c/m)a-2
If there is no integer n that satisfies the relationship:

According to the invention described in claim 1, the timing is controlled so that data from the photosensor is taken in when the image of the measurement dot of the light emitting array is always at a position where it is not obstructed by the slit. It is possible to measure light intensity with high precision without using any members or separate photosensors, and which is not affected by the dot size, dot pitch, unevenness of relative movement speed, etc. of the light emitting array.

Further, according to the second aspect of the invention, even under conditions where the image of the measurement dot of the light emitting array is obstructed by the slit, that is, when a sufficiently large value of n cannot be obtained, the width of the slit is Since the image of the adjacent dot is optimized to fit within the slit, the eclipse can be equally compensated for, making highly accurate measurement possible.

Embodiment An embodiment of the invention set forth in claim 1 will be described with reference to FIGS. 1 to 3. The same parts as those shown in FIG. 5 are indicated using the same reference numerals. FIG. 1 schematically shows the positional relationship of the measuring devices according to FIG. 5, etc., and the dot size of the light emitting array 1 is a, and the dot pitch is b. The magnification of the objective lens 2 is m times, and for example, images 6b to 6d of the dots 1b to 1d are shown on the imaging plane. A slit forming member 3 having a slit 4 having a slit width C is provided on such an imaging plane, and a photosensor 5 is provided behind it.

With such a configuration, the objective lens 2 (including the slit 4 and the objective lens 5) and the light emitting array 1 are moved at a relatively constant velocity V.
to move it. For example, in FIG. 1, the objective lens 2
, the light emitting array 1 is moved to the right by the stage at a speed V
When the image 6C of the light emitting dot IC is moved to the left in the vicinity of the imaging plane at a speed mv, the next image 6b comes to be at the center of the slit 4 after a certain period of time. FIG. 2 shows the state at this time as seen from the photosensor 5 side.

Here, the moving speed V is actually uneven.

Now, this unevenness is expressed as a deviation between the predicted position and the actual position after a certain period of time, and the maximum value thereof is assumed to be X. A control means 9 is connected to the photosensor 5 for timing control so that the detection data of the photosensor 5 is taken in at regular intervals.

Now, when the vicinity of the image plane is enlarged, it becomes as shown in Fig. 3. Here, it is assumed that the images 6b, 6c, and 6d are perpendicular to the slit 4 in the positional relationship shown in FIGS. Then, it is ideal to capture the data of the photosensor 5 when the image 6c is at the center of the slit 4, as shown in FIG.
shall be. However, as shown in the same figure (b), the amount of deviation d=
Even if the data is acquired with a shift to the right by d,
There is no vignetting due to the slit 4, and the entire amount of light from the image 6c can be captured behind the slit. However, the same figure (
As shown in c), when data is captured with the deviation amount d = d shifted to the right, the right end side of the image formation 6c becomes a length of (d, -(c - m a ) / 2) due to the slit 4. As a result, the accuracy of measurement decreases.

Therefore, the amount of dot shift at the timing of capturing data from the photosensor 5 is always d, = (c-m
a) It is necessary to set it to less than /2 in order to obtain highly accurate data.

On the other hand, the data acquisition timing depends on the uniform velocity movement mv including the positional deviation mX due to speed unevenness, and by acquiring data at fixed time intervals, the slit 4 and the image are formed by the length of Q = m v /l. It is assumed that the positional relationship with 6 is changed and captured. At this time, since it is desirable that the breath value be a deviation amount O between adjacent dots, a value of 9=mb/n (n is an integer) is preferable. The time to move at relative velocity mv with respect to this Q = m b / n is t = Q /
m v = (m b / n ) / m v =
b / n v, and the time b / n for the set n
The control means 9 may control to capture data from the photosensor 5 every nv.

Here, considering the given dot size a, tod pitch b, moving speed V, and positional deviation X due to uneven moving speed of the light emitting array 1, the maximum amount of deviation d M during data acquisition is
AX is the sum of the maximum positional deviation mx (on the imaging plane) and half of the movement i m b / n when continuously acquiring data, and becomes dMAX"mx + (mb/2n). This is As mentioned above, it is d.If ≦d1, the accuracy increases, so m x + (m b / 2 n
)≦(c-ma)/2. Calculating this for n, n≧b/ ((c/m)
-a-2x). However, b≧C≧a, x≦(c-
ma)/2. By setting the values of n and b so as to satisfy the above equation, the light intensity distribution of each dot of the light emitting array I can be measured with high precision. As long as n generally satisfies the above formula,
It is easier to process the captured data if it is made as small as possible.

This will be explained using specific numerical values. For example, as a first example,
300dpi (pitch b = 84, 6 μm)
A light emitting array l having a structure where the dot size a=501 Im
When the maximum value of positional deviation due to uneven feeding is x = 2 μm, objective lens 2 with m = 4, width c = 24
If 0pm slit 4 is used, n≧84.6/
(240/4-5O-2x2)=14.1, n=15, t=84. ' Highly accurate measurement can be achieved by acquiring data at time intervals of 6/15v.

Also, as a second example, 400dpi (pitch b=63.
Even in the case of the light emitting array 1 having a structure in which the dot size a=40 μm and the dot size a=40 μm, n≧63.5/(240/4−40−2X2)=3.
92. Therefore, high precision measurement can be achieved by setting n=4 and acquiring data at time intervals of t=63.5/4v.

Furthermore, as a third example, 300 dpi as in the first example.
When using the light emitting array 1 having the structure, the width c=
If 300 pm slit 4 is used, n≧84.6/ (300/4-5O-2X2)4.0
3, and by setting n=5 and acquiring data at time intervals of t=84,615v, highly accurate measurement can be achieved.

In other words, by simply increasing the slit width from 240 μm to 300 μm, the time interval is tripled compared to the first example, that is, 1/
Highly accurate measurement is possible with a data amount of 3.

Next, an embodiment of the invention according to claim 2 will be described with reference to FIG. Due to the burden of data processing, n≧b/ ((c
/m)-a-2x) If there is no combination of n and c that satisfies c=mb and the maximum n, that is, 1≦n≦b/ ((c/m)-a-2x)= b, / (
By setting n to an integer that satisfies the relationship ba-a-2X), although the accuracy of the light intensity of a specific dot decreases, it is possible to measure it with sufficient accuracy to know the overall light intensity distribution state.

This results in the image formation 6 as shown in FIGS.
c shifts from the slit 4, and as shown in the same figure (C), when do)(c-ma)/2, the right end portion 6c' of the image 6C is eclipsed by the slit 4. ,c=
Because of mb, the right end portion 6d' of the next image 6d enters the slit 4, so only the subtraction light quantity bone of both sections 6c' and 6d' decreases in accuracy, and c (m b) The measurement accuracy is higher than that in the case shown in FIG. Assuming α, the measurement accuracy S at this time is a+b-2d 2d, -b+a)),]X100'
/.

5-(((')+α(2a a It can be expressed as

Effects of the Invention As described above, the present invention has the advantage of reducing the dot size of the light emitting array,
In order to deal with irregularities in feeding due to the dot pitch and the relative movement between the objective lens and the light emitting array, the invention according to claim 1 allows data to be acquired when the image of the measurement dot on the light emitting array is always at a position that cannot be obstructed by the slit. In the invention as claimed in claim 2, even if the dot is excluded by the slit, focusing on the image formation of the subsequent adjacent dot, a part of the image of the subsequent adjacent dot enters the slit, thereby making it possible to Since the width of the slit is set so as to compensate for the deviation, it is possible to measure the light intensity distribution with high precision using a simple structure that remains the same as the basic structure.

[Brief explanation of drawings]

FIG. 1 is a vertical side view showing an embodiment of the invention as claimed in claim 1, FIG. 2 is a partial plan view thereof, and FIG. 3 is a vertical side view showing an enlarged example of the positional relationship near the slit. , FIG. 4 is an enlarged longitudinal sectional side view showing an example of the positional relationship near the slit of an embodiment of the invention as claimed in claim 2, FIG. 5 is a longitudinal sectional side view showing a conventional example, and FIG. FIGS. 7 and 8 are vertical side views showing an example proposed by a person. FIGS. 7 and 8 are vertical side views showing an enlarged view of the vicinity of the imaging plane in order to explain its operation. l...Light emitting array, 1a-xlf...Dot, 2.
...Objective lens, 3...Slit forming member, 4...
Slit, 5... Photo sensor, 9... Control means 3
” Figure applicant Rico Co., Ltd. la ”e 3 Figure 4 bd'6c' Σ

Claims (1)

[Scope of Claims] 1. An objective lens is provided opposite to a light emitting array in which a large number of light emitting element dots are arranged, and a slit forming member having a slit is provided near the image formation plane of the light emitting array by the objective lens, A light intensity distribution measuring device for a light emitting array, wherein a photosensor is provided on the optical path of the light passing through the slit, and the objective lens, the slit forming member, the photosensor, and the light emitting array are moved relative to each other. where each dot size is a, the dot arrangement pitch is b, the slit width is c, and the magnification of the objective lens is m, the relationship b≧c/m≧a is satisfied, and the light emitting array and the objective lens are An integer that satisfies the relationship n≧b/{(c/m)-a-2x}≧0, where x is the maximum deviation amount of uneven feeding with respect to relative speed v when moving at relative speed v A light intensity distribution measuring device for a light emitting array, characterized in that a control means is provided for acquiring data from the photosensor at time intervals of b/nv for n. 2. An objective lens is provided to face a light emitting array in which a large number of light emitting element dots are arranged, and a slit forming member having a slit is provided near the image formation plane of the light emitting array by the objective lens, and light passing through the slit is provided. In a light intensity distribution measuring device for a light emitting array, a photo sensor is provided on an optical path of the light emitting array, and the objective lens, the slit forming member, the photosensor, and the light emitting array are moved relative to each other. , the dot array pitch is b, the slit width is c, and the magnification of the objective lens is m, satisfying the relationship b≧c/m≧a, and moving the light emitting array and the objective lens at a relative speed v. When the maximum value of the deviation amount of uneven feeding with respect to this relative speed v is x, when data from the photosensor is acquired at a time interval of b/nv, n≧b/{(c/m) -a-2x}≧0 If there is no integer n that satisfies the relationship, the light intensity distribution of the light emitting array is characterized in that a control means is provided to take in data from the photosensor by setting the size of the slit to c=mb. measuring device.