JPH0495749A - Mtf measuring apparatus of led array - Google Patents

Abstract

PURPOSE:To omit a wave-form observing means in a conventional technology by obtaining MTF with the electronic circuits of an MAX/MIN holding circuit, an analog operation circuit and a sample holding circuit. CONSTITUTION:When the output of an image sensor is inputted into an MAX/ MIN holding circuit, the MAX and the MIN of the wave forms are sequentially detected. The output voltage which is held for the specified time is obtained. The output voltage is supplied into an analog operating circuit 2. In the analog operating circuit 2, MTF=(MAX-NIN)/(MAX+MIN) is operated based on the inputted MAX and MIN. Then, the MTF output voltage from the analog operation circuit is held at the MTF sample timing of the MAX/MIN holding circuit 1, and the MTF is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an MTF (modulation transfer function) IJ constant device for an LED array used as a light source for an LED printer device or the like.

[Prior Art] The LED array r printer head is composed of an LED array in which a large number of minute light emitters are arranged in a straight line, and a SELFOC lens array that is placed facing the LED array at a certain distance. There is an optical system that

Next, the configuration of the LED printer device will be explained with reference to FIG. 1G is the toner transfer section, 1
7 is a heat fixing section.

Electrostatic sensation caused by corona charge 12)'
(When the light from the LED array 13 shines on the Ni drum 11, only the areas hit by the light will be discharged.

(1) Toner 14 is transferred to the paper produced by the toner transfer unit 1G at a position corresponding to the charged portion of the electrostatic photosensitive drum 11, and the toner 14 is fixed to the paper by the heat fixing unit 17. Ru.

Next, the electrostatic photosensitive drum 11 and the LED array 1 shown in FIG.
3 will be explained with reference to FIG.

11r] 18 is a selfoc lens array,
The light beam of the LED array 13 is transferred to the electrostatic photosensitive drum 1.11.
If there are variations in the amount of light emitted from the LED array 13 or variations in the distance between the LED array 13 and the SELFOC lens array 18, the printing quality will deteriorate due to the variations. Therefore, it is necessary to measure the irradiation intensity of each beam emitted from the LED array 13 and check for variations in the amount of light.

, to ζ? 7ff LED array (MTF) using next technology
The measuring device will be explained with reference to FIG.

In FIG. 12, an image sensor 19 that receives the irradiated light from the LED array 13 is placed at a certain distance from the SELFOC lens array 18, and the LED array 13 is one light emitting body (hereinafter referred to as one dot). Lights up in a pattern that flashes every other time.

The light intensity distribution of the irradiation beam is measured by the LED array 13 at a position a certain distance away from the light beam emission surface of the LED array r13.
When measured in the arrangement direction of V i in FIG. 7 or 8
A ripple-like waveform like n is obtained.

The MTF measurement of the LEDTL 13 is a means of evaluating the quality of the irradiated beer from the individual maximum values (hereinafter referred to as MAX) and minimum values (hereinafter referred to as MIN) of such ripple waveforms. For example, in the case of measurement using a blinking pattern of every other dot, the larger the ripple ratio of the waveform, the higher the irradiation resolution of each light beam will be.

The received light intensity distribution on the light receiving surface of the image sensor 19 is observed by the waveform observing means 21 via the signal detecting means 20, and λITF is determined from the maximum received light intensity MAX and the minimum received light intensity MIN using the following equation.

λ4TF= (84AX-MIN)'/ (MAX+M
IN)・・・・・・・・・・・・・・・・・・(1)[
Problems to be Solved by the Invention] In FIG. 12, the MTF detection signal from the image sensor 19 is measured as a waveform il! by a waveform observation means 21 such as an oscilloscope.
However, with the conventional device shown in Figure 12, the operation is complicated, it is difficult to obtain measurement accuracy, the measurement takes time, and a waveform observation means 21 such as an oscilloscope is required. There are issues such as what needs to be done.

This invention provides electronic circuits for MAX/MIN hold circuits, analog calculation circuits, and sample hold circuits.
The MTF detection signal waveform is tracked in real time and the MTF detection signal waveform is tracked in real time.
IVIT, an LED array that can output calculated values
The purpose is to provide an F measuring device.

[Means for Solving the Problems] In order to achieve this object, the present invention provides an MTF measurement device that detects light emission from an LED array with an image sensor via a SELFOC lens array. , a MIN hold circuit 5 and a timing control circuit 6, and a λ・18X hold circuit 4 and an MI
The N hold circuit 5 receives the output of the r image sensor as input, and the timing control circuit 6 receives the start signal as input to control the timing of the MAX hold circuit 4 and the MIN hold circuit 5.
The output of AX/MIN hold circuit 1 is input, and (MA
The analog calculation circuit 2 includes an analog calculation circuit 2 that calculates X-MIN)/(MAX + MIN), and a sample-hold circuit 3 that receives the output of the analog calculation circuit 2 and samples and holds the MTF sample signal from the timing control circuit 6.

Next, a system diagram of the MTF measuring device according to the present invention will be explained with reference to FIG.

In FIG. 1, 1 is a %i AX/MIN hold circuit, 2 is an analog arithmetic circuit, and 3 is a sample hold circuit.

When the Vin shown in Fig. 8 is input to the MAX/MIN hold circuit 1, the MAX and MIN of the waveform are detected independently and sequentially, and -
- An output voltage held for a certain period of time is obtained, and this output voltage is supplied to the analog calculation circuit 2.

The analog calculation circuit 2 calculates equation (1) from the input MAX and Δ4■N.

Next (≧ The MTF output voltage from the analog arithmetic circuit 2 is sampled and held by the sample hold circuit 3.
The MTF shown in FIG. 8 is obtained by sequentially holding at the MTF sample timing of the N hold circuit 1.

[Embodiment] Next, the configuration diagram of the embodiment shown in FIG. 1 will be explained with reference to FIG. 2.

FIG. 2 is a block diagram showing in detail the inside of the blocks in FIG. 1.

The MAX/MINt7/l/do circuit 1 includes a MAX hold circuit 4, a MIN hold circuit 5, and a timing control circuit 6.
The MAX hold circuit 4 and the 84 IN hold circuit 5 receive the output of the image sensor 19 shown in FIG. 5
control the timing of

Next, a circuit diagram of an embodiment of the MAX/MIN hold circuit 1 shown in FIG. 2 will be explained with reference to FIG.

Fig. 4 is an operation waveform diagram of Fig. 3, and shows 1, ~, and Vin, start, and MTF samples in Fig. 3, :sl
The operating waveforms of AX and MIN are shown in correspondence with diagram M4.

Next, the M A X / M I N hold circuit shown in FIG. 3 will be explained.

&iAX hold circuit 4 in Figure 3 is a peak hold circuit, and 4A and 4B are FETs with small input bias current.
Input operational amplifier, 4C is comparator, 4D is C%103F
This is an analog switch using ET, and conducts when the control input (current) is at logic level "1".

Comparator・↓C when input voltage Vin exceeds MAX,
Outputs logic level "O".

4E is a hold capacitor, for example, a 0.1 μF capacitor.

The XII N hold circuit 5 in FIG. 3 is a bottom hold circuit, and 5A to 5E are the same as 4A to 4E.

The ratio 1i2 unit 5C outputs a logic level "O" when the λ voltage Vin exceeds MIN.

The timing control circuit 6 is connected to the MAX hold circuit 4 and the person 1.
When both rN hold circuits 5 obtain a hold state, a logic level "1" is output for a certain period of time as an MTF sample timing. 6A and 6B are monostable multis that operate at the input logic level "0", and the output pulse widths are in the relationship T i ) T yu. In the example, T = 0.
5ms, T = 0.2rns.

Next, a circuit diagram of another embodiment shown in FIG. 3 will be explained with reference to FIG. 5.

FIG. 6 is an operational waveform diagram of FIG. 5. Figure 5 1...
Back and Vin and start and MTF samples, NlΔ
The operating waveforms of X and MIN are shown in correspondence with FIG.

MAX hold circuit 4 and MIN hold circuit 5 in Figure 5
is the same as in Figure 4.

The comparators 4C and 5C in Fig. 5 are connected to 4C and 5C in Fig. 3 with ten-man power and one-man power interchanged, and comparators 4C-5C in Fig. 5 detect MAX and MIN. The output logic level is "1", which is the opposite of that in FIG.

Reference numeral 7 in FIG. 5 is a timing control circuit, which outputs a logic level "1" as MTF sample timing for a certain period of time when both the MAX hold circuit 4 and the MIN hold circuit 5 obtain a hold state.

7A to 7C are monostable multis that operate at an input logic level of "1". The output pulse width is T s > T
2''=Ts.In the example, T:0.
5 ms, T2 = 0.2 ms, T3:
It is set to 0.2ms.

Next, the analog arithmetic circuit 2 and sample hold circuit 3 will be explained with reference to FIG.

2A to 2C in FIG. 2 are operational amplifiers, each having a gain of 11 times. The output of operational amplifier 2C is (MAX
+MIN) is obtained, and (MAX-MIN) is obtained at the output of the operational amplifier 2B.

Add these outputs to the X and X inputs of divider 2D.

Since the sample and hold circuit 3 in FIG. 2 sequentially holds the MTF calculation voltage obtained by the analog calculation circuit 2,
The MTF calculation result as shown in Figure jI8 is obtained.

Figure 9 shows the knee/one-choice F calculation output when using the measuring device according to the present invention, and the arrangement interval is 105.8 μm.
This is data when the LED array 13 of 2 is caused to emit light in a continuous dot pattern.

Note that the sample and hold circuit 3 in FIG.
A D converter can also be used.

In this case, change the MTF sample timing in Figure 2 to A.
/ Since it can be used as a conversion timing input for a D converter, MTF data can be digitized.

[Effects of the Invention] According to the present invention, the electronic circuits of the MAX/MIN hold circuit, the analog calculation circuit, and the sample hold circuit can
Since we are looking for TF, we can eliminate the need for conventional waveform observation means, track the MTF detection signal waveform in real time, and measure MTF.
Calculated values can be output.

[Brief explanation of the drawing]

FIG. 1 shows the MTFil! according to this invention. System diagram of the I-determined device, Figure 2 is a detailed configuration diagram of Figure 1, Figure 3 is the MA of Figure 2.
A circuit diagram of an embodiment of the X/MIN hold circuit 1, FIG. 4 is an operation waveform diagram of FIG. 3, FIG. 5 is a circuit diagram of another embodiment of FIG. 3, and FIG. 6 is an operation of FIG. 5. Waveform diagrams, Figures 7 and 8 are MTF measurement waveform diagrams, Figure 9 is a waveform diagram of MTF measurement data when using the measuring device in Figure 1, and Figure 10 is LE
FIG. 11 is a diagram illustrating the relationship between an LED array and an electrostatic photosensitive drum, and FIG. 12 is a diagram illustrating a conventional MTF measurement device for an LED array. 1...M A X /? vi I N hold circuit, 2...analog calculation circuit, 3...sample hold circuit, 11...
・MAX hold circuit, 5-...MIN hold circuit, 6...timing control circuit, 7...timing control circuit. 13...LED array, 18...Selfoc lens array, 19...
...Image sensor. Figure 1 Agent Patent Attorney Kin Tsukasa Komata Figure 2 Time Figure Time Figure Figure Figure Korokyo Charge Figure Cause

Claims (1)

[Claims] 1. MTF of an LED array in which light emission from the LED array is detected by an image sensor via a SELFOC lens array
In the measuring device, MAX hold circuit (4), MIN hold circuit (5)
and a timing control circuit (6), the MAX hold circuit (4) and the MIN hold circuit (5) input the output of the image sensor, and the timing control circuit (6).
) is a MAX hold circuit (4) using the start signal as input.
) and the MAX/MIN hold circuit (1) that controls the timing of the MIN hold circuit (5), and the MAX/MIN
The output of the hold circuit (1) is input, and (MAX-MI
An analog calculation circuit (2) that calculates N)/(MAX+MIN) and the output of the analog calculation circuit (2) are input,
An MTF measurement device for an LED array, comprising a sample and hold circuit (3) that samples and holds an MTF sample signal from the timing control circuit.