grating

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grating

(grāt′ing)
In spectrophotometry, the element used in a monochromator that disperses white light into the visible spectrum. It is composed of finely etched lines in the reflecting material.

grating

A series of black and white parallel bars of equal width used to measure visual acuity, contrast sensitivity, and resolution of optical systems. The grating can be either square-wave (also called Foucault grating or Foucault pattern), in which the luminance across a bar is constant, or sine-wave, in which the luminance varies sinusoidally (Fig. G6). See cycle per degree; contrast sensitivity function.
Fig. G6 Square-wave gratingenlarge picture
Fig. G6 Square-wave grating
References in classic literature ?
Hetty Sorrel often took the opportunity, when her aunt's back was turned, of looking at the pleasing reflection of herself in those polished surfaces, for the oak table was usually turned up like a screen, and was more for ornament than for use; and she could see herself sometimes in the great round pewter dishes that were ranged on the shelves above the long deal dinner-table, or in the hobs of the grate, which always shone like jasper.
He locked and unlocked his hands over the grate and spread his fingers close to the bluish flame, while the coals crackled and the clock ticked and a street vendor began to call under the window.
There was not litter enough, when she had swept the floors and cleaned the grates, to even half fill the housemaid's bucket which she carried with her.
Felix visited the grate at night and made known to the prisoner his intentions in his favour.
The coals glowed without a flame; and upon the red glow the vertical bars of the grate stood out at her feet, black and curved, like the charred ribs of a consumed sacrifice.
The mass of hot coals tumbled down in the grate, and he turned to look at them .
With his elbow presenting no appearance of a joint, but more like a bend in a dummy's limb, thrown over the back of a chair, he leaned forward slightly over his short and enormous thighs to spit into the grate.
leaflets, stretched out his robust legs, keeping the soles of his boots turned up to the glow in the grate.
With which parting words, coolly added as he listened to his receding footsteps and locked the grate upon himself, he descended the steps, and lighting the fire below the little copper, prepared, without any assistance, for his daily occupation; which was to retail at the area-head above pennyworths of broth and soup, and savoury puddings, compounded of such scraps as were to be bought in the heap for the least money at Fleet Market in the evening time; and for the sale of which he had need to have depended chiefly on his private connection, for the court had no thoroughfare, and was not that kind of place in which many people were likely to take the air, or to frequent as an agreeable promenade.
He looked sharply at the birds himself, as he held the child up at the grate, especially at the little bird, whose activity he seemed to mistrust.
There was a silence, broken only by the fall of the ashes in the grate.
He had liberty to walk in a small paved yard at a certain hour, and learnt from the turnkey, who came to unlock his cell and show him where to wash, that there was a regular time for visiting, every day, and that if any of his friends came to see him, he would be fetched down to the grate.